Human Exploration of Mars:

Stephen J. Hoffman, Editor

David I. Kaplan, Editor

Lyndon B. Johnson Space Center

Houston, Texas

July 1997

NASA Special Publication 6107

The Reference Mission of the

NASA Mars Exploration

Study Team

Human Exploration of Mars:

The Reference Mission of the NASA Mars Exploration Study Team

Stephen J. Hoffman, Editor

Science Applications International Corporation

Houston, Texas

David I. Kaplan, Editor

Lyndon B. Johnson Space Center

Houston, Texas

July 1997

NASA Special Publication 6107
This publication is available from the NASA Center for AeroSpace Information, 800 Elkridge Landing Road, Linthicum Heights,

MD 21090-2934 (301) 621-0390.
III

Foreword

Mars has long beckoned to humankind

from its travels high in the night sky. The

ancients assumed this rust-red wanderer was

the god of war and christened it with the

name we still use today.

Early explorers armed with newly

invented telescopes discovered that this

planet exhibited seasonal changes in color,

was subjected to dust storms that encircled

the globe, and may have even had channels

that crisscrossed its surface.

Recent explorers, using robotic

surrogates to extend their reach, have

discovered that Mars is even more complex

and fascinating—a planet peppered with

craters, cut by canyons deep enough to

swallow the Earth’s Grand Canyon, and

shouldering the largest known volcano in the

solar system. They found intriguing evidence

that water played an important role on Mars

with channels that bear a striking

resemblance to stream beds and clouds of

crystalline ice that still traverse its red sky.

But they also found that Mars was cold and

dry, and believed to be devoid of life.

Now present day explorers have

announced that pieces of Mars have arrived

on Earth as meteorites, and that these bits of

the red planet contain evidence pointing to

the possible existence of life early in Mars

history. This has resulted in renewed public

interest in this fellow traveler of the solar

system, adding impetus for exploration.

Over the past several years studies

have been conducted on various approaches

to exploring Earth’s sister planet Mars. Much

has been learned, and each study brings us

closer to realizing the goal of sending humans

to conduct science on the Red Planet and

explore its mysteries. The approach described

in this publication represents a culmination of

these efforts but should not be considered the

final solution. It is our intent that this

document serve as a reference from which we

can continuously compare and contrast other

new innovative approaches to achieve our

long-term goal. A key element of future

improvements to this document will be the

incorporation of an integrated robotic/human

exploration strategy currently under

development.

We will continue to develop alternative

approaches, technologies, precursor missions,

and flight demonstrations that collectively

move us forward. Inputs have been, and will

always be, encouraged from all sources—

NASA centers, industry, research

organizations, entrepreneurs, government

agencies, international partners, and the

public at large—which will improve our

understanding and current planning. We

plan to use the results of these assessments to

shape our investments in technology, and to
IV

look for high leverage, innovative, breakthrough approaches to the most cost effective

exploration. These data will also help us

understand the required infrastructure, as

well as provide important insights into how

we can use the International Space Station to

validate key assumptions and technologies.

To achieve our goal, we must

fundamentally change the way in which we

explore with both humans and robots. We

must search for alternatives to substantially

reduce the cost of exploration, while

increasing the inherent value to humankind.

This Reference Mission provides a viable

starting point for NASA’s continuing efforts

to develop the technologies and systems, as

well as the international partnerships, needed

for the grand adventure of sending humans to

explore another planet in our solar system—

one that may have once, and may yet again,

harbor life.
V

Acknowledgments

Sending people to Mars has been a

long-held dream of humankind, and many

have approached the task of turning the

dream into reality. This document is another

chapter in the ongoing process of melding

new and existing technologies, practical

operations, fiscal reality, and common sense

into a feasible and viable human mission to

Mars. However, this is not the last chapter in

the process, but marks a snapshot in time that

will be added to and improved upon by

others in the future. This report has benefited

from the contributions and advice of many

individuals from the government and private

sectors. The individuals listed on the

following page assisted in preparing the

concepts described in this report and in

compiling the words, images, and data used

for that description.

Stephen J. Hoffman

David I. Kaplan
VI

Contributing Authors

Ames Research Center:

Roger Arno

Dr. Geoff Briggs

Dr. Yvonne Clearwater

Dr. Marc Cohen

Andy Gonzales

Johnson Space Center:

Dr. Michael Duke

David Kaplan

Catherine Larson

David Weaver

Laurie Weaver

Lewis Research Center:

Robert Cataldo

Dr. Stanley Borowski

SAIC:

Dr. Stephen Hoffman

Paul Phillips

Study Team Members

Ames Research Center:

Dr. Geoff Briggs (co-lead)

Johnson Space Center:

Jeri Brown

Nancy Ann Budden

Beth Caplan

John Connolly

Dr. Michael Duke (co-lead)

Dallas Evans

Dr. Steve Hawley

Kent Joosten

David Kaplan

Darrell Kendrick

Barbara Pearson

Barney Roberts

Ed Svrcek

David Weaver

Lewis Research Center:

Dr. Stanley Borowski

Robert Cataldo

Los Alamos National Laboratory:

Dr. Paul Keaton

Marshall Space Flight Center:

William Huber

General Contributors

Ames Research Center:

Betsy Dunsky

Paul Espinosa

Vladimir Garin

Lynn Harper

Butler Hine

Larry Lemke

Doug O’Handley

Nelson Schlater

Michael Sims

Boeing:

Brent Sherwood

Lewis Research Center:

Dr. Stanley Borowski

Rockwell International:

Robert Raasch

Lisa Rockoff

Reviewers and Commenters

Johnson Space Center:

Nancy Ann Budden

John Connolly

Other Support and Contributions

Ames Research Center:

Dr. Chris McKay

Jeff Moore

Dr. Carol Stoker

Anthony Gross

Editorial and Graphics Support

J. Frassanito and Associates:

J. Frassanito

SAIC:

R. Patrick Rawlings
VII

There is a set of supplemental technical reports which

provide greater depth into many of the design features of the

Mars Reference Mission than is given in section 3 of this

document. Had those papers been included as appendices, the

size of this document would have greatly expanded.

Consequently, we decided to make those supplemental

materials available through the world wide web. We intend to

post new materials as to the web as they are produced and hope

to maintain a site with the latest information which describes

key technologies and design features of a human mission to

Mars.

The site for the Mars Reference Mission is

http://www_sn.jsc.nasa.gov/marsref/contents.html
VIII
IX

Contents

Section Page

Acronyms .................................................................................................................................................... xv

1. OVERVIEW AND EXECUTIVE SUMMARY..................................................................................... 1-1

1.1 INTRODUCTION ..................................................................................................................................... 1-3

1.2 BACKGROUND........................................................................................................................................ 1-5

1.3 REFERENCE MISSION EXECUTIVE SUMMARY .............................................................................. 1-6

1.3.1 Objectives ...................................................................................................................................... 1-6

1.3.2 Groundrules and Assumptions .................................................................................................. 1-7

1.3.3 Mission and Systems ................................................................................................................... 1-8

1.3.3.1 Mission Design ............................................................................................................. 1-8

1.3.3.2 In Situ Resource Production ..................................................................................... 1-16

1.3.3.3 Flight Crew ................................................................................................................. 1-16

1.3.3.4 Robotic Precursors ..................................................................................................... 1-17

1.3.3.5 Launch Systems .......................................................................................................... 1-18

1.3.3.6 Interplanetary Transportation Systems .................................................................. 1-18

1.3.3.7 Surface Systems .......................................................................................................... 1-22

1.3.3.8 Operations ................................................................................................................... 1-24

1.3.3.9 Mission and Systems Summary ............................................................................... 1-27

1.4 TESTING PRINCIPAL ASSUMPTIONS AND CHOICES ................................................................ 1-28

1.4.1 Robust Surface Infrastructure .................................................................................. 1-28

1.4.2 Split Mission Strategy ................................................................................................ 1-28

1.4.3 Nuclear Thermal Propulsion .................................................................................... 1-30

1.4.4 In Situ Resource Utilization ...................................................................................... 1-30

1.4.5 Common Habitat Design .......................................................................................... 1-31

1.4.6 Nuclear Surface Power .............................................................................................. 1-31

1.4.7 Abort to the Surface ................................................................................................... 1-32

1.4.8 Design for the Most Difficult Opportunity ............................................................ 1-33

1.5 CONCLUSIONS AND RECOMMENDATIONS ............................................................................... 1-33

1.5.1 Mission and Systems ................................................................................................. 1-33

1.5.2 Technology Development ......................................................................................... 1-34

1.5.3 Environmental Protection ......................................................................................... 1-37

1.5.4 Program Cost .............................................................................................................. 1-38

1.5.5 International Participation ........................................................................................ 1-39

1.5.6 Program Management and Organization ............................................................... 1-41

1.6 REFERENCES .......................................................................................................................................... 1-44
X

Section Page

2. SCIENCE AND EXPLORATION RATIONALE ................................................................................ 2-1

2.1 INTRODUCTION ..................................................................................................................................... 2-3

2.2 THE “WHY MARS” WORKSHOP ......................................................................................................... 2-3

2.3 SCIENCE RATIONALE ........................................................................................................................... 2-6

2.4 EXPLORATION RATIONALE .............................................................................................................. 2-13

2.4.1 Inhabiting Another Planet......................................................................................................... 2-13

2.4.2 International Cooperation ......................................................................................................... 2-15

2.4.3 Technological Advancement ..................................................................................................... 2-16

2.4.4 Inspiration ................................................................................................................................... 2-18

2.4.5 Investment ................................................................................................................................... 2-19

2.5 WHY NOT MARS? ................................................................................................................................. 2-19

2.5.1 Human Performance.................................................................................................................. 2-19

2.5.2 System Reliability and Lifetime ............................................................................................... 2-21

2.5.3 Political Viability and Social Concerns ................................................................................... 2-22

2.6 SUMMARY .............................................................................................................................................. 2-23

2.7 REFERENCES .......................................................................................................................................... 2-23

3. MISSION AND SYSTEM OVERVIEW............................................................................................... 3-1

3.1 INTRODUCTION ..................................................................................................................................... 3-3

3.1.1 Mission Objectives ....................................................................................................................... 3-3

3.1.2 Surface Mission Implementation Requirements...................................................................... 3-4

3.1.2.1 Conduct Human Missions to Mars ........................................................................... 3-4

3.1.2.2 Conduct Applied Science Research ........................................................................... 3-5

3.1.2.3 Conduct Basic Science Research ................................................................................ 3-6

3.1.2.4 Surface Operations Philosophy.................................................................................. 3-7

3.1.3 Groundrules and Assumptions .................................................................................................3-11

3.2 RISKS AND RISK MITIGATION STRATEGY .................................................................................... 3-12

3.2.1 Risks to Human Life .................................................................................................................. 3-13

3.2.2 Risks to Mission Success ........................................................................................................... 3-14

3.2.3 Risks to Program Success .......................................................................................................... 3-14

3.2.4 Risk Mitigation Strategy ............................................................................................................ 3-14

3.3 FLIGHT CREW ....................................................................................................................................... 3-16

3.3.1 Crew Composition ..................................................................................................................... 3-16

3.3.2 Crew Systems Requirements .................................................................................................... 3-20

3.4 MISSION OPERATIONS ....................................................................................................................... 3-21

3.4.1 Training Guidelines.................................................................................................................... 3-22

3.4.2 Science and Exploration ............................................................................................................ 3-24

3.4.3 System Operations and Maintenance...................................................................................... 3-24

3.4.4 Programmatic Activities ............................................................................................................ 3-25

3.4.5 Activity Planning ....................................................................................................................... 3-26

3.4.5.1 Pre-Launch Phase ....................................................................................................... 3-27

3.4.5.2 Earth Launch Phase ................................................................................................... 3-28

3.4.5.3 Trans-Mars Phase ....................................................................................................... 3-29

3.4.5.4 Mars Landing Phase .................................................................................................. 3-30

3.4.5.5 Mars Surface Phase .................................................................................................... 3-31

3.4.5.6 Mars Launch Phase .................................................................................................... 3-33

3.4.5.7 Trans Earth Phase ....................................................................................................... 3-34

3.4.5.8 Earth Entry and Landing .......................................................................................... 3-35

3.4.5.9 Post Landing ............................................................................................................... 3-35
XI

Section Page

3.5 MISSION DESIGN .................................................................................................................................. 3-36

3.5.1 Trajectory Options ...................................................................................................................... 3-36

3.5.2 Trajectory Selection Factors ...................................................................................................... 3-37

3.5.2.1 Satisfying Reference Mission Goals and Objectives ............................................. 3-38

3.5.2.2 Satisfying Reference Mission Risk Strategy ........................................................... 3-38

3.5.2.3 Satisfying Reference Mission Program Flexibility ................................................ 3-41

3.5.3 Mission Design Strategy ............................................................................................................ 3-42

3.5.3.1 Trajectory Type ........................................................................................................... 3-42

3.5.3.2 Split Mission Strategy ................................................................................................ 3-42

3.5.3.3 Aerocapture ................................................................................................................ 3-43

3.5.3.4 Surface Rendezvous................................................................................................... 3-43

3.5.3.5 Use of Indigenous Resources ................................................................................... 3-44

3.5.3.6 Mars Orbit Rendezvous and Direct Entry at Earth ............................................... 3-44

3.5.4 Mission Sequence ....................................................................................................................... 3-44

3.5.4.1 First Mission: 2007 Opportunity .............................................................................. 3-45

3.5.4.2 Second Mission: First Flight Crew, 2009 Opportunity .......................................... 3-46

3.5.4.3 Third Mission: Second Flight Crew, 2011 Opportunity ........................................ 3-54

3.5.4.4 Fourth Mission: Third Flight Crew, 2014 Opportunity ........................................ 3-55

3.5.4.5 Mission Summary ...................................................................................................... 3-59

3.6 SYSTEMS .................................................................................................................................................. 3-60

3.6.1 Operational Design Considerations ........................................................................................ 3-61

3.6.2 Launch Vehicles .......................................................................................................................... 3-62

3.6.3 Interplanetary Transportation .................................................................................................. 3-72

3.6.3.1 Trans-Mars Injection Stage........................................................................................ 3-72

3.6.3.2 Biconic Aeroshell ........................................................................................................ 3-73

3.6.3.3 Transit/Surface Habitat ............................................................................................ 3-77

3.6.3.4 Mars Surface Lander .................................................................................................. 3-79

3.6.3.5 Mars Ascent Vehicle ................................................................................................... 3-82

3.6.3.6 Earth-Return Vehicle.................................................................................................. 3-86

3.6.3.7 Interplanetary Transportation Power Systems ...................................................... 3-90

3.6.4 Surface Systems .......................................................................................................................... 3-95

3.6.4.1 Surface Habitat/Laboratory ..................................................................................... 3-95

3.6.4.2 Life Support System .................................................................................................. 3-97

3.6.4.3 In-Situ Resource Utilization.................................................................................... 3-101

3.6.4.4 Surface Mobility ....................................................................................................... 3-105

3.6.4.5 Extra Vehicular Activity Systems ............................................................................3-110

3.6.4.6 Surface Power Systems ............................................................................................ 3-111

3.7 PRECURSORS .....................................................................................................................................3-116

3.7.1 Current Robotic Program Plans ..............................................................................................3-116

3.7.2 Mars Sample Return With ISRU ............................................................................................. 3-116

3.7.3 Human Exploration Precursor Needs ....................................................................................3-117

3.7.4 Autonomous Deployment of Surface and Orbital Elements ..............................................3-117

3.8 GROUND SUPPORT AND FACILITIES OPERATIONS .................................................................3-118

3.8.1 Systems Operations.................................................................................................................. 3-120

3.8.2 Science Operations ................................................................................................................... 3-121
XII

Section Page

3.9 PROGRAMMATIC ISSUES ................................................................................................................. 3-122

3.9.1 Cost Analysis ............................................................................................................................ 3-122

3.9.1.1 Organizational Culture and Cost ........................................................................... 3-123

3.9.1.2 The Cost Model ........................................................................................................ 3-124

3.9.2 Management and Organizational Structure ......................................................................... 3-132

3.9.3 Technology Development ....................................................................................................... 3-136

3.10 REFERENCES ........................................................................................................................................ 3-144

TABLES

Table Page

1-1 Pricipal Discriminators of Short- and Long-Stay Mission Scenarios.................................... 1-29

1-2 Key Elements of Lower-Cost Programs .................................................................................... 1-42

2-1 Mars Exploration Consultant Team............................................................................................. 2-4

2-2 Mars Study Team ........................................................................................................................... 2-5

3-1 Capabilities and Demonstrations for Surface Mission Activities ........................................... 3-5

3-2 Surface Mission Skills .................................................................................................................. 3-18

3-3 General Launch Manifest: 2007 Launch Opportunity ............................................................ 3-47

3-4 General Launch Manifest: 2009 Launch Opportunity ............................................................ 3-49

3-5 Surface Science Payload for First Flight Crew ......................................................................... 3-52

3-6 General Launch Manifest: 2011 Launch Opportunity ............................................................ 3-55

3-7 Surface Science Payload for Second Flight Crew .................................................................... 3-57

3-8 General Launch Manifest: 2014 Launch Opportunity ............................................................ 3-59

3-9 Surface Science Payload for Third Flight Crew ....................................................................... 3-60

3-10 Launch Vehicle Concepts for the Mars Reference Mission .................................................... 3-63

3-11 Mass Estimates for TMI Stage Alternatives ............................................................................. 3-75

3-12 Mass and Size Estimates for Biconic Aeroshell Family .......................................................... 3-77

3-13 Mars Transit/Surface Habitation Element ............................................................................... 3-82

3-14 Earth Return Habitation Element Mass Breakdown .............................................................. 3-92

3-15 Estimated Power Profile for Outbound and Return Transits ................................................ 3-93

3-16 30kWe Power System With Fuel Cells and Solar Arrays ........................................................ 3-96

3-17 5kWe Power System With Fuel Cells and Solar Arrays .......................................................... 3-96

3-18 Mars Surface Laboratory/Habitat Element Mass Breakdown .............................................. 3-98

3-19 LSS Mass, Volume, Power Comparison .................................................................................. 3-100

3-20 Mass and Power Estimates for the First ISRU Plant ............................................................. 3-105

3-21 Mass and Power Estimates for the Second ISRU Plant ........................................................ 3-106

3-22 Characteristics for Fixed Surface Power System Options .....................................................3-113

3-23 Rover Power System Characteristics........................................................................................3-115

3-24 Program Environment Effects on Program Management Style .......................................... 3-126

3-25 A Comparison of Development Culture Parameters for Commercial

Aircraft and NASA Manned Programs................................................................................... 3-127

3-26 Key Elements of Lower-Cost Programs .................................................................................. 3-134

3-27 Dual Use Technologies: Propulsion ......................................................................................... 3-139

3-28 Dual Use Technologies: Communications/Information Systems....................................... 3-139
XIII

Table Page

3-29 Dual Use Technologies: In Situ Resource Utilization............................................................ 3-140

3-30 Dual Use Technologies: Surface Mobility - Suits ................................................................... 3-141

3-31 Dual Use Technologies: Surface Mobility - Vehicles ............................................................. 3-141

3-32 Dual Use Technologies: Human Support ............................................................................... 3-142

3-33 Dual Use Technologies: Power ................................................................................................. 3-142

3-34 Dual Use Technologies: Structures and Materials ................................................................. 3-143

3-35 Dual Use Technologies: Science and Science Equipment ..................................................... 3-143

3-36 Dual Use Technologies: Operations and Maintenance ......................................................... 3-144

FIGURES

Figure Page

1-1 Typical fast-transit trajectory ........................................................................................................ 1-9

1-2 Mars Reference Mission Sequence............................................................................................. 1-10

1-3 General sequence of events associated with first mission to Mars ........................................ 1-11

1-4 Possible time line for first Mars surface mission ..................................................................... 1-15

1-5 Reference Mars cargo and piloted vehicles .............................................................................. 1-20

1-6 Distribution of Reference Mission costs ................................................................................... 1-39

1-7 Relationship between program cost and program culture .................................................... 1-41

2-1 Orbital image taken by Mariner 4 (1965) .................................................................................... 2-7

2-2 Olympus Mons v (Mariner 9 image), the largest volcano in the solar system...................... 2-8

2-3 Across the middle is Valles Marineris, a huge canyon as long as the United States ............ 2-9

2-4 Dense tributary networks indicative of past presence of liquid water on Mars ................. 2-11

3-1 A regional map illustrating potential locations for a Mars outpost ....................................... 3-8

3-2 Typical short-stay mission profile.............................................................................................. 3-37

3-3 Typical long-stay mission profile ............................................................................................... 3-37

3-4 Fast-Transit mission profile ........................................................................................................ 3-38

3-5 Round-trip mission duration comparisons .............................................................................. 3-39

3-6 Microgravity comparisons for various mission classes .......................................................... 3-41

3-7 Mars reference mission sequence .............................................................................................. 3-45

3-8 Mars surface outpost after deployment of payloads from

first two cargo landers ................................................................................................................. 3-48

3-9 Mars surface outpost at the end of first flight crew’s stay ..................................................... 3-51

3-10 Possible surface mission time line ............................................................................................. 3-53

3-11 Mars surface outpost at the end of second flight crew’s stay ................................................ 3-56

3-12 Mars surface outpost at the end of third flight crew’s stay ................................................... 3-58

3-13 Mars Energia-derived HLLV with eight Zenit-type boosters ................................................ 3-64

3-14 STS External Tank-derived HLLV with seven LOX/RP boosters ......................................... 3-65

3-15 STS External Tank-derived HLLV with four strap-on boosters, each

having two F-1 engines ............................................................................................................... 3-67

3-16 Saturn V-derived Mars HLLV with F-1A/J-2S propulsion .................................................... 3-68

3-17 Saturn V-based Mars HLLV concepts ....................................................................................... 3-69

3-18 Energia launch vehicle adapted to Mars mission profile ....................................................... 3-70
XIV

Figure Page

3-19 Mars mission launch vehicle with two external tank boosters and kick stage ................... 3-71

3-20 Reference Mars cargo and piloted vehicles .............................................................................. 3-73

3-21 Biconic aeroshell dimensions for Mars lander and surface habitat modules ...................... 3-76

3-22 Transit habitat attached to International Space Station .......................................................... 3-78

3-23 The crew exercise facility component of the countermeasures system

designed to inhibit crew degradation from exposure to reduced

gravity environments .................................................................................................................. 3-80

3-24 EVA suit storage locations are critical in a robust crew safety system ................................. 3-80

3-25 Conceptual Mars habitation module-wardroom design ........................................................ 3-81

3-26 Habitat and surface laboratory joined on Mars surface ......................................................... 3-83

3-27 Mars surface lander descending on parachutes ...................................................................... 3-84

3-28 Mars surface lander just prior to landing illustrating landing legs

and surface mobility system ....................................................................................................... 3-85

3-29 Mars surface lander and biconic aeroshell ............................................................................... 3-87

3-30 Crew ascent capsule just after launch from Mars surface ...................................................... 3-87

3-31 Methane/LOX ascent stage configuration2 ............................................................................. 3-88

3-32 ECCV returning to Earth on a steerable parafoil..................................................................... 3-91

3-33 Solar array power source for interplanetary spacecraft ......................................................... 3-94

3-34 Nominal power profile for the transit/surface habitat .......................................................... 3-95

3-35 Hybrid LSS process distribution .............................................................................................. 3-100

3-36 Schematic of the first ISRU plant ............................................................................................. 3-104

3-37 Concepts for the unpressurized and automated surface rovers ......................................... 3-108

3-38 Concept for the large pressurized surface rover ................................................................... 3-109

3-39 Conceptual airlock and EVA suit maintenance facility ......................................................... 3-111

3-40 Mars surface power profile ........................................................................................................3-112

3-41 The relative cost of programs using different management approaches ........................... 3-125

3-42 A comparison of the relative costs for Reference Mission elements ................................... 3-129
XV

Acronyms

AMCM Advanced Missions Cost Model

COSPAR Committee on Space Research

CPAF cost plus award fee

CPFF cost plus fixed fee

DIPS Dynamic Isotope Power System

ECCV Earth crew capture vehicle

ERV Earth return vehicle

ETO Earth-to-orbit

EVA extravehicular activity

GCR galactic cosmic radiation

HMF health maintenance facility

HLLV heavy-lift launch vehicle

IAA International Academy of

Astronautics

IMLEO intial mass to low Earth orbit

ISRU in-situ resource utilization

LEO low Earth orbit

LMO low Mars orbit

LOX liquid oxygen

LSS life support system

MAV Mars-ascent vehicle

MGS Mars Global Surveyor

MOI Mars Orbit Insertion

MTV Mars transfer vehicle

NASA National Aeronautics and

Space Administration

ND NERVA derived

NDR NERVA derivative reactor

NERVA nuclear engine for rocket vehicle

application

NTR nuclear thermal rocket

PI principal investigator

PVA photovoltaic array

RFC regenerative fuel cell

RTG radioisotope thermoelectric generator

SPE solar proton event

SSME Space Shuttle Main Engine

STS Space Transportation System

TEI trans-Earth injection

TCS Thermal Contract System

TMI trans-Mars injection

TROVs telerobotic rovers

1-1

1. Overview
1-2
1-3

1.1 Introduction

The human exploration of Mars will be a

complex undertaking. It is an enterprise that

will confirm the potential for humans to leave

our home planet and make our way outward

into the cosmos. Though just a small step on a

cosmic scale, it will be a significant one for

humans, because it will require leaving Earth

with very limited return capability. The

commitment to launch is a commitment to

several years away from Earth, and there is a

very narrow window within which return is

possible. This is the most radical difference

between Mars exploration and previous lunar

explorations.

Personnel representing several NASA

field centers have formulated a “Reference

Mission” addressing human exploration of

Mars. This report summarizes their work and

describes a plan for the first human missions

to Mars, using approaches that are technically

feasible, have reasonable risks, and have

relatively low costs. The architecture for the

Mars Reference Mission builds on previous

work, principally on the work of the

Synthesis Group (1991) and Zubrin’s (1991)

concepts for the use of propellants derived

from the martian atmosphere. In defining the

Reference Mission, choices have been made.

In this report, the rationale for each choice is

documented; however, unanticipated

technology advances or political decisions

might change the choices in the future.

One principal use of the Reference

Mission is to lay the basis for comparing

different approaches and criteria in order to

select better ones. Even though the Reference

Mission appears to have better technical

feasibility, less risk, and lower cost than

previous approaches, improvement is still

needed in these areas to make the first piloted

Mars mission a feasible undertaking for the

spacefaring nations of Earth. The Reference

Mission is not implementable in its present

form. It involves assumptions and

projections, and it cannot be accomplished

without further research, development, and

technology demonstrations. It is also not

developed in the detail necessary for

implementation, which would require a

systematic development of requirements

through the system engineering process. With

this in mind, the Reference Mission may be

used to:

•Derive technology research and

development plans.
1-4

•Define and prioritize requirements for

precursor robotic missions.

•Define and prioritize flight experiments

for precursor human missions, such as

those involving the Space Shuttle, Mir, or

the International Space Station.

•Understand requirements for human

exploration of Mars in the context of

other space missions and research and

development programs, as they are

defined.

•Open discussion with international

partners in a manner that allows

identification of potential interests of the

participants in specialized aspects of the

missions.

•Provide educational materials at all

levels that can be used to explain various

aspects of human interplanetary

exploration.

•Describe to the public, media, and

political system the feasible, long-term

visions for space exploration.

•Establish an end-to-end mission baseline

against which other proposals can be

compared.

However, the primary purpose of the

Reference Mission is to stimulate further

thought and development of alternative

approaches which can improve effectiveness,

reduce risks, and reduce cost. Improvements

can be made at several levels; for example, in

the architectural, mission, and system levels.

•The architectural level involves

assembly of all elements into an

integrated whole. The principal features

to be addressed in a new architecture

that will improve on the Reference

Mission appear to be simplification

(particularly the number of separate

elements that must be developed) and

integration with other programs.

Simplification by reduction of system

elements can lower life-cycle costs and

diminish both programmatic and

technical risk. For example, the

development of higher performance

space propulsion systems can lead to

simplification, particularly if one vehicle

can be used for transit to and from Mars.

Integration opportunities to link the

Mars program with other development

programs could reduce total cost

through sharing of developmental costs.

The Reference Mission did not assume

integration with a lunar exploration

program. The development of a major

Earth-orbiting operations center in

another program could lead to major

changes in the Reference Mission

architectural approach.

•At the mission level, it may be possible

to reduce the number of separate

launches from Earth. Reducing the total

number of launches required to

implement the Reference Mission

objectives could potentially reduce

program and technical risk as well as

cost. Focusing and streamlining mission
1-5

objectives and improving technology

that will lower mass and power

requirements can improve the mission

level.

•At the system level, the performance of

individual systems and subsystems can

be improved through research and

development programs. The

programmatic and technical risks can be

reduced by demonstrations of ground,

Earth-orbit, or planet surface (including

the Moon) technology. Criteria for

improved systems are principally

technical—reduced mass, reduced

power, increased reliability.

The current section of this report

provides a brief overview of the origins of the

study and the Reference Mission design,

specifically discussing key issues, findings,

and recommendations. Section 2 of this report

addresses what can be learned by

undertaking the Reference Mission and

describes the scientific and technical

objectives of Mars exploration. Section 3

provides a detailed discussion of the mission

life cycle, the systems needed to carry it out,

and the management challenges and

opportunities that are inherent in a program

to explore Mars with humans.

1.2 Background

The Mars Exploration Study Project was

undertaken to establish a vision for the

human exploration of Mars that would serve

as a mechanism for understanding the

programmatic and technical requirements

that would be placed on existing and planned

Agency programs.

In August 1992, the first workshop of the

Mars Study Team held at the Lunar and

Planetary Institute in Houston, Texas,

addressed the “whys” of Mars exploration to

provide the top-level requirements from

which the Mars exploration program could be

built (Duke and Budden 1992). The workshop

attendees identified the major elements of a

potential rationale for a Mars exploration

program as:

•Human Evolution – Mars is the most

accessible planet beyond the Earth-Moon

system where sustained human presence

is believed to be possible. The technical

objectives of Mars exploration should be

to understand what would be required

to sustain a permanent human presence

beyond Earth.

•Comparative Planetology – The scientific

objectives of Mars exploration should be

to understand the planet and its history,

and therefore to better understand Earth.

•International Cooperation – The political

environment at the end of the Cold War

may be conducive to a concerted

international effort that is appropriate to,

and may be required for, a sustained

Mars program.

•Technology Advancement – The human

exploration of Mars currently lies at the

ragged edge of achievability. The
1-6

necessary technical capabilities are either

just available or on the horizon.

Commitment to the program will both

effectively exploit previous investments

and contribute to advances in

technology.

•Inspiration – The goals of Mars

exploration are grand; they will motivate

our youth, benefit technical education

goals, and excite the people and nations

of the world.

The study team of personnel from NASA

field centers used these inputs to construct

the Reference Mission, and then translated the

inputs into a set of goals and objectives.

Ground rules and assumptions were agreed

upon and reflect the lessons learned from

previous study efforts. From this work, a

mission and a set of systems were developed.

1.3 Reference Mission Summary

1.3.1 Objectives

Reflecting the conclusions of the August

1992 workshop, three objectives were adopted

for the analysis of a Mars exploration

program and the first piloted missions in that

program. They are to conduct:

•Human missions to Mars and verify a

way that people can ultimately inhabit

Mars.

•Applied science research to use Mars

resources to augment life-sustaining

systems.

•Basic science research to gain new

knowledge about the solar system’s

origin and history.

The human missions to Mars, which are

required to accomplish the exploration and

research activities, also contain requirements

for safe transportation, maintenance on the

surface of Mars, and return of a healthy crew

to Earth. The surface exploration mission

envisions approximately equal priority for

applied science research (that is, learning

about the environment, resources, and

operational constraints that would allow

humans eventually to inhabit the planet) and

basic science research (that is, exploring the

planet for insights into the nature of planets,

the nature of Mars’ atmosphere and its

evolution, and the possible past existence of

life). These more detailed objectives form the

basis for defining the required elements and

operations for the Reference Mission.

In addition, past mission studies have

yielded results that have characterized piloted

Mars missions as being inherently difficult

and exorbitantly expensive. To confront these

commonly accepted beliefs that are

unfortunately tied to Mars missions, this

study added objectives to:

•Challenge the notion that the human

exploration of Mars is a 30-year program

that will cost hundreds of billions of

dollars. Although the nations of the

world could afford such expenditures in

comparison to, for example, military

budgets, the smaller the total cost, the
1-7

more likely it is that the program will be

implemented.

•Challenge the traditional technical

obstacles associated with sending

humans to Mars.

•Identify relevant technology

development and investment

opportunities that benefit both Mars

exploration and Earth-bound endeavors.

From these basic objectives, a Reference

Mission was crafted by drawing on lessons

learned from many past studies and by

adding new insights to various aspects of the

mission. This approach substantially

improved the yield from piloted missions

while also reducing risk and cost.

1.3.2 Ground Rules and Assumptions

Translating these objectives into specific

missions and systems for the Reference

Mission required adopting a number of

ground rules and assumptions. These were to:

•Balance technical, programmatic,

mission, and safety risks.

•Provide an operationally simple mission

approach emphasizing the judicious use

of common systems.

•Provide a flexible implementation

strategy.

•Limit the length of time that the crew is

continuously exposed to the

interplanetary space environment.

•Define a robust planetary surface

exploration capacity capable of safely

and productively supporting crews on

the surface of Mars for 500 to 600 days

each mission.

•Define a capability to be able to live off

the land.

•Rely on advances in automation to

perform a significant amount of the

routine activities throughout the

mission.

•Ensure that management techniques are

available and can be designed into a

program implementation that can

substantially reduce costs.

•Use the Earth-Mars launch opportunities

occurring from 2007 through 2014. A

2009 launch represents the most difficult

opportunity in the 15-year Earth-Mars

cycle. By designing the space

transportation systems for this

opportunity, particularly those systems

associated with human flights, they can

be flown in any opportunity with either

faster transit times for the crew or

increased payload delivery capacity.

•Examine three human missions to Mars.

The initial investment to send a human

crew to Mars is sufficient to warrant

more than one or two missions. Each

mission will return to the site of the

initial mission thus permitting an

evolutionary establishment of

capabilities on the Mars surface.
1-8

Although it is arguable that scientific

data return could be enhanced by a

strategy where each human mission

went to a different surface site, the goal

of understanding how humans can

inhabit Mars seems more logically

directed toward a single outpost

approach.

1.3.3 Mission and Systems

Previous studies of human exploration of

Mars have tended to focus on spacecraft and

flight, rather than on what the crew would do

on the surface. The Reference Mission takes

the point of view that surface exploration is

the key to the mission, both for science and

for evaluation of the potential for settlement.

As a consequence, the Reference Mission

architecture allows for a robust surface

capability with significant performance

margins: Crews will explore in the vicinity of

the outpost out to a few hundred kilometers,

will be able to study materials in situ and in a

surface laboratory, and will be allowed to

update and modify the exploration plan to

take advantage of their discoveries.

In addition, key technologies will be

developed and demonstrated to test

settlement issues, potentially imposing a

substantial workload on the Mars exploration

crew. To improve the effectiveness of surface

operations, supporting systems must be

highly reliable, highly autonomous, and

highly responsive to the needs of the crew.

Some needs may not be anticipated during

crew preparation and training, which will

significantly challenge the management and

operations systems to support the crew in the

new situations.

1.3.3.1 Mission Design

The crew will travel to and from Mars on

relatively fast transits (4 to 6 months) and will

spend long periods of time (18 to 20 months;

600 days nominal) on the surface, rather than

alternative approaches which require longer

times in space and reduce time on the surface.

Figure 1-1 illustrates a typical trajectory.

Designed to the worst-case mission

opportunity (2007-2009) of the next two

decades, the transit legs are less than 180 days

in both directions. For easier Mars mission

opportunities (for example, 2016-2018), the

transit legs are on the order of 130 days.

Shorter transit times reduce the time spent by

the crew in zero g to the length of typical

tours of duty for the International Space

Station. (Thus, the Mars Study Team chose

not to use artificial gravity spacecraft designs

for the Reference Mission.) In addition,

relatively fast transits will reduce the

exposure to galactic cosmic radiation and the

probability of encountering solar particle

events. Reducing the exposure to zero g and

radiation events helps reduce the risk to the

crew.

The strategy chosen for the Reference

Mission, generally known as a “split mission”

strategy, breaks mission elements into pieces

that can be launched directly from Earth with

launch vehicles of the Saturn V or Energia

class, without rendezvous or assembly in low
1-9

Earth orbit (LEO). The strategy has these

pieces rendezvous on the surface of Mars,

which will require both accurate landing and

mobility of major elements on the surface to

allow them to be connected or to be moved

into close proximity. Another attribute of the

split mission strategy is that it allows cargo to

be sent to Mars without a crew during the

same launch opportunity or even one or more

opportunities prior to crew departure. This

allows cargo to be transferred on low energy,

longer transit time trajectories and the crew to

be sent on a required higher energy, shorter

transit time trajectory. Breaking the mission

into two launch windows allows much of the

infrastructure to be emplaced and checked

out before committing a crew to the mission,

and also allows for a robust capability, with

duplicate launches on subsequent missions

providing either backup for the earlier

launches or growth of initial capability.

Figure 1-2 illustrates the mission

sequence analyzed for the Reference Mission.

In this sequence, three vehicles will be

launched from Earth to Mars in each of four

launch opportunities which, for reasons

presented earlier, start in 2007. The first three

launches will not involve a crew but will send

infrastructure elements to low Mars orbit and

to the surface for later use. Each of the

remaining opportunities analyzed for the

Reference Mission will send one crew and

two cargo missions to Mars. These cargo

missions will consist of an Earth-return

vehicle (ERV) on one flight and a lander

carrying a Mars-ascent vehicle (MAV) and

additional supplies on the second. This

sequence gradually builds up assets on the

martian surface so that at the end of the third

crew’s tour of duty, the basic infrastructure

could be in place to support a permanent

presence on Mars.

The six launches used to support the

activities of the first crew will be discussed in

more detail here to illustrate what will

typically occur for all three crews. (Note: For

the nominal mission, launches 1 through 4 are

required to support the first crew; launches 5

and 6 provide backup systems for the first

crew and, if not used, are available for the

second crew.) Figure 1-3 illustrates the

general sequence of events associated with

the first crew’s mission to Mars as discussed

in the following paragraphs.

In the first launch opportunity, three

cargo missions are sent on minimum energy

trajectories direct to Mars (that is, without

assembly or fueling in LEO). Launch 1

γ

Earth Launch

2/1/2014

Depart Mars

3/11/2016

Arrive Mars

7/1/2014

Earth Return

6/29/2016

MISSION TIMES

OUTBOUND 150 days

STAY 619 days 

RETURN 110 days

TOTAL MISSION 879 days

Nominal 

Departure

3/11/2016

Figure 1-1 Typical fast-transit

trajectory.
1-10

delivers a fully fueled ERV to Mars orbit. (The

crew will rendezvous with this stage and use

it to return to Earth after completion of their

surface exploration mission.) Launch 2

delivers an unfueled MAV, a propellant

production module, a nuclear power plant,

liquid hydrogen (to be used as a reactant to

produce the ascent vehicle propellant), and

approximately 40 tonnes of additional

payload to the surface. After the descent stage

lands on the surface, the nuclear reactor

autonomously deploys itself several hundred

meters from the ascent vehicle. Using the

Mars atmosphere as feedstock, the propellant

production module begins to manufacture the

nearly 30 tonnes of oxygen and methane that

1

2

3

6

4

5

9

7

8

12

10

ETO

FLIGHT 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

∆ MAV-1 landing

∆ Initial Habitat landing

∆ ERV-1 parks in LMO

∆ Crew 1 ascent

∆ Crew 1 TEI

∆ Crew 1 Earth return

ERV loiter

ERV loiter

ERV loiter

∆ ERV-2 parks in LMO

∆ MAV-2 landing

∆ MAV 3 landing

Crew 1: launch ∆ ∆ Landing

Crew 2 launch ∆

Crew 3 launch ∆

∆ Landing

∆ Landing

∆ ERV-3 parks in LMO

∆ Crew 2 TEI

∆ Crew 2 Earth return

∆ MAV 4 landing

∆ Ascent

∆ Crew 2 ascent

∆ ERV 4 LMO

2017

∆ Crew 3 TEI

2018

∆ Crew 3 Earth return

ERV loiter

11

12345678901

12345678901

12345678

Interplanetary transit

Unoccupied wait in Mars orbit

Propellant production and on Mars surface

Crew surface operations

Figure 1-2 Mars Reference Mission sequence.

ERV: Earth Return Vehicle

MAV: Mars Ascent Vehicle

TEI: Trans Earth Injection

LMO: Low Mars Orbit
1-11

Figure 1-3 General sequence of events associated with first mission to Mars.
1-12

Figure 1-3 General sequence of events continued.
1-13

will be required to eventually deliver the crew

to Mars orbit. This production is completed

within approximately one year—several

months prior to the first crew’s scheduled

departure from Earth. Launch 3 lands in the

vicinity of the first descent vehicle and

delivers a surface habitat/laboratory,

nonperishable consumables for a safe-haven,

and a second nuclear power plant to the

planetary surface. The second nuclear power

plant autonomously deploys itself near the

first power plant. Each power plant can

provide sufficient power (160 kWe) for the

entire mature surface outpost, thereby

providing complete redundancy within the

power production function.

During the second launch opportunity,

two additional cargo missions and the first

crew are launched. All assets previously

delivered to Mars have been checked out and

the MAV, already on the martian surface, is

verified to be fully fueled before either the

crew or the additional cargo missions are

launched from Earth. (Should any element of

the surface system required for crew safety or

critical for mission success not check out

adequately, the surface systems will be placed

in standby mode and the crew mission

delayed until the systems can be replaced or

their functions restored. Some systems can be

replaced using hardware originally intended

for subsequent missions; others may be

functionally replaced by other systems.) The

first cargo launch of this second opportunity

is a duplicate of Launch 1 from the first

opportunity, delivering a second fully fueled

ERV to Mars orbit. The second cargo launch

similarly mirrors Launch 2 of the previous

opportunity, delivering a second unfueled

ascent vehicle and propellant production

module. These systems provide backup or

extensions of the previously deployed

capabilities. For example, the second MAV

and second ERV provide the first crew with

two redundant means for each leg of the

return trip. If, for some reason, either the first

ascent vehicle or the first return vehicle

becomes inoperable after the first crew

departs Earth, this crew can use either of the

systems launched in the second opportunity

instead. If the first ascent and return vehicles

operate as expected, then the systems

delivered in the second opportunity will

support the second crew that will launch to

Mars in the third opportunity.

The first crew of six departs for Mars in

the second opportunity. They leave Earth

after the two cargo missions have been

launched, but because they are sent on a fast

transfer trajectory of only 180 days, they will

arrive in Mars orbit approximately 2 months

before the cargo missions. The crew lands on

Mars in a surface habitat substantially

identical to the habitat/laboratory previously

deployed on the martian surface. After

capturing into a highly elliptic Mars orbit, the

crew descends in the transit habitat to

rendezvous on the surface with the other

elements of the surface outpost. (The crew

carries sufficient provisions for the entire

surface stay in the unlikely event that they are

unable to rendezvous on the surface with the

assets previously deployed.)
1-14

Surface exploration by robotic vehicles

and human explorers will include a wide

range of activities.

•Observing and analyzing the surface and

subsurface geology.

•Observing and analyzing the

composition and structure of the

atmosphere.

•Collecting samples and examining them

in the outpost laboratory.

•Performing experiments designed to

gauge the ability of humans to inhabit

Mars.

Prior to the arrival of the first human

crew, telerobotic rovers (TROVs) may be

delivered to the surface. (These rovers are

assumed to be intelligent enough to perform

broadly stated objectives without human

assistance. But humans will continue to

monitor progress and be available to

“supervise” the TROV if it cannot solve a

particular problem.) When the crew arrives,

the rovers will be available for teleoperation

by the crew. The TROVs may be designed to

provide global access and may be able to

return samples to the outpost from hundreds

of kilometers distance from the site if they are

deployed 2 years before the crew arrives.

The outpost laboratory will be outfitted

to provide mineralogical and chemical

analyses of rocks, soils, and atmospheric

samples; and depending on technical

development, it may be possible to undertake

simple kinds of geochronologic analysis on

Mars. The purpose of these studies would be

to support the field investigations, answer

“sharper” questions, and allow the human

explorers to narrow their focus to the sites of

optimum sample collection. As hypotheses

evolve, crews will be able to return to sample

sites and gather specific samples to test the

hypotheses. Ultimately, selected samples will

be returned to Earth for more detailed

analysis.

As experience grows, the range of human

exploration will grow from the local to the

regional. Regional expeditions, lasting

perhaps 2 weeks and using mobile facilities,

may be conducted at intervals of a few

months. Between these explorations, analysis

in the laboratory will continue. The crew will

also spend a significant portion of its time

performing maintenance and housekeeping

tasks (system design requirements addressing

enhanced reliability and maintainability will

help keep these activities to a minimum).

Figure 1-4 provides a possible time line for

the first surface mission.

The deployment of a bioregenerative life

support capability will be an early activity

after crew landing. Although this system is

not required to maintain the health and

vitality of the crew, it will improve the

robustness of the life support system and is

important to the early objectives of the

outpost.

Crew activities related to living on

another planet should be viewed as

experiments. With minor modifications in
1-15

Figure 1-4 Possible time line for first Mars surface mission.

Mars Surface Mission Time Allocation

(Total Time = 8 crew X 24 hr/day X 600 days = 115,200 hr)

8 crew X 24 hr day = 200)

Charge Fuel Cells

Check Vehicle

Load Vehicle

Plan Excursion

Drive Vehicle

Navigate

Don Suits (X 20)

Pre-breathe (X 20)

Egress (X 20)

Unload Equip

Set up Drill (X 10)

Operate Drill

Collect Samples

In Situ Analysis

Take Photos

Communicate

Disassemble Equip

Load Vehicle

Ingress (X 20)

Clean Suit (X 20)

Stow Suit, Equip

Inspect Vehicle

Secure for night

(Sleep, eat, cleanup

hygiene, etc.

covered)

3 Crew X 7 hr X 10 Day =

210 hrs total

600 day (or 20 months, or 86 weeks)

Sleep, Sleep Prep, Dress, Undress: 8 hr

Hygiene, Cleaning, Personal Communication: 1 hr

Recreation, Exercise, Relaxation: 1 hr

Eating, Meal Prep, Clean-up: 1 hr

One Day Off Per Week: 3 hr (per day)

General Planning, Reporting, Documentation, Earth Communication: 1 hr

Group Socialization, Meetings, Life Sciences Subject, Health Monitoring, Health Care: 1 hr

System Monitoring, Inspection, Calibration, Maintenance, Repair: 1 hr

Site Prep,

Construction

Verification

Week Off

Local Excursions

Analysis

Distant Excursion

Analysis

Week Off

Distant Excursion

Analysis

Distant Excursion

Analysis

Week Off

Distant Excursion

Analysis

Distant Excursion

Analysis

Flare Retreat

Week Off

Distant Excursion

Analysis

Distant Excursion

Analysis

Week Off

Sys Shutdown

Departure Prep

Personal

14 hr

(total 67,200 hr)

Hr/Over

head

3 hr

(14,400 hr)

Production

7 hr

(33,600 hr total)

90 days

7 days

100 days

10 days

40 days

7 days

100 days

15 days

7 days

7 days

100 days

60 days
1-16

hardware and software, ordinary experiences

can be used to provide objective databases for

understanding the requirements for human

settlement.

The first crew will stay at the outpost for

18 to 20 months. Part of their duties will be to

prepare the outpost site for the receipt of

additional elements launched on subsequent

mission opportunities. Since the first crew

will have to depart before the second crew

arrives, some systems will have to be placed

in standby mode.

After their stay on Mars, each crew will

use the previously landed and in situresource-utilization fueled ascent vehicle to

return to orbit where they will rendezvous

with the waiting ERV. The crew will return to

Earth in a habitat similar to the one used for

the outbound transit leg. This habitat, which

is part of the ERV deployed in a previous

opportunity by one of the cargo flights,

typically will have been in an untended mode

for nearly 4 years prior to the crew arrival.

1.3.3.2 In Situ Resource Production

The highly automated production of

propellant from martian resources is another

defining attribute of the Reference Mission.

The technology for producing methane and

liquid oxygen from the martian atmosphere

and some nominal hydrogen feedstock from

Earth is an effective performance

enhancement and appears to be

technologically feasible within the next few

years. The split mission strategy allows the

propellant production capability to be

emplaced, checked out, and operated to

produce the required propellant prior to

launching the crew from Earth.

In addition to spacecraft propulsion, the

production capability on Mars can provide

fuel for surface transportation, reactants for

fuel cells, and backup caches of consumables

(water, oxygen, nitrogen, and argon) for the

life support system.

1.3.3.3 Flight Crew

Humans are the most valuable mission

asset for Mars exploration and must not

become the weak link. The objective for

humans to spend up to 600 days on the

martian surface places unprecedented

requirements on the people and their

supporting systems. Once committed to the

mission on launch from LEO, the crew must

be prepared to complete the full mission

without further resupply from Earth.

Unlimited resources cannot be provided

within the constraints of budgets and mission

performance. Their resources will either be

with them or will have already been delivered

to or produced on Mars. So trade-offs must be

made between cost and comfort, as well as

performance and risk. Crew self-sufficiency is

required because of the long duration of their

mission and the fact that their distance from

Earth impedes or makes impossible the

traditional level of communications and

support by controllers on Earth. The crews

will need their own skills and training and

specialized support systems to meet the new

challenges of the missions.
1-17

The nominal crew size for this mission is

six. This number is believed to be reasonable

from the point of view of past studies and

experience and is a starting point for study.

Considerable effort will be required to

determine absolute requirements for crew

size and composition. This determination will

have to consider the tasks required of the

crew, safety and risk considerations, and the

dynamics of an international crew. Crew

members should be selected in part based on

their ability to relate their experiences back to

Earth in an articulate and interesting manner,

and they should be given enough free time to

appreciate the experience and the opportunity

to be the first explorers of another planet.

Significant crew training will be required to

ensure that the crew remains productive

throughout the mission.

1.3.3.4 Robotic Precursors

Robotic precursor missions will play a

significant role in three important areas of the

Reference Mission. The first area is to gather

information about Mars that will be used to

determine what specific crew activities will be

performed and where they will be performed.

The second area is to demonstrate the

operation of key techonologies required for

the Reference Mission. The third is to land,

deploy, operate, and maintain a significant

portion of the surface systems prior to the

arrival of the crew.

For optimum mission performance, it

will be necessary to pick a landing site based

primarily on its ability to achieve Reference

Mission objectives. The site must be

consistent with operational considerations,

such as landing and surface operational

safety. Detailed maps of candidate landing

sites built from data gathered by precursor

robotic missions will define the safety and

operational hazards of the sites, as well as

confirm whether access to scientifically

interesting locations is possible by humans or

robotic vehicles. Robotic surface missions,

including missions to return samples, may be

required to confirm remotely sensed data

from orbit and to satisfy planetary protection

issues. To satisfy the human habitation

objectives in particular, it would be highly

desirable to locate the outpost site where

water can be readily extracted from minerals

or from subsurface ice deposits. Such a

determination may only be possible from data

collected by a robotic surface mission.

To accomplish the Reference Mission, key

advances in certain critical technologies will

need to occur. The robotic precursor missions

offer an opportunity to demonstrate the

operation of many of those technologies, such

as in situ resource utilization, aerocapture,

precision landing, etc. The information and

experience gained from the demonstration of

these technologies will add immeasurable

confidence for their use in the human

mission.

The first phase of human exploration is

the automated landing of surface

infrastructure elements, including a system to

produce propellant and life support

consumables, the first of two habitats, power
1-18

systems, and surface transportation elements.

All of these systems will be delivered, set up,

and checked out using robotic systems

operated or supervised from Earth. The

propellant required for the MAV will be

produced and stored as will oxygen and

water caches for the habitat. The overall site

will be prepared for receipt of the second

habitat.

1.3.3.5 Launch Systems

The scale of the required Earth-to-orbit

(ETO) launch capability is determined by the

mass of the largest payload intended for the

martian surface. The nominal design mass for

individual packages to be landed on Mars in

the Reference Mission is 50 tonnes for a crew

habitat sized for six people that is transferred

on a high-energy orbit. This requires the

capability for a single launch vehicle to be

from about 200 to 225 tonnes to LEO.

Because 200-ton-class launch vehicles

raise development cost issues, consideration

was given to the option of launching pieces to

LEO using smaller vehicles and assembling

(attaching) them in space prior to launching

them to Mars. This smaller launch vehicle

(110 to 120 tonnes) would have the advantage

of more modest development costs and is

within the capability of the Russian Energia

program. However, the smaller launch vehicle

introduces several potential difficulties to the

Reference Mission scenario. The simplest,

most desirable implementation using this

smaller launch vehicle is to simply dock the

two elements in Earth orbit and immediately

depart for Mars. To avoid the boiloff loss of

cryogenic propellants in the departure stages,

all elements must be launched from Earth in

quick succession. This places a strain on a

single launch facility and its ground

operations crews or requires the close

coordination of two or more launch facilities.

Assembling the Mars vehicles in orbit and

loading them with propellants from an

orbiting depot just prior to departure may

alleviate the strain on the launch facilities, but

the best Earth orbit for a Mars mission is

different for each launch opportunity.

Therefore, a permanent construction or

propellant storage facility in a single Earth

orbit is not an optimal solution.

The choice of a launch vehicle remains a

significant issue for any Mars mission. For the

Reference Mission, however, the larger, 200-

ton-class launch vehicle has been assumed

without specifying a particular configuration.

1.3.3.6 Interplanetary Transportation System

The interplanetary transportation system

consists of a trans-Mars injection (TMI) stage,

a biconic aeroshell for Mars orbit capture and

Mars entry, a descent stage for surface

delivery, an ascent stage for crew return to

Mars orbit, an Earth-return stage for

departure from the Mars system, and a crew

capsule (similar to an Apollo Command

Module) for Earth entry and landing. As

mentioned earlier, the Reference Mission

splits the delivery of elements to Mars into

cargo missions and human missions, all of

which are targeted to the same locale on the
1-19

surface and must be landed in close proximity

to one another. The transportation strategy

adopted in the Reference Mission eliminates

the need for assembly or rendezvous of

vehicle elements in LEO, but it does require a

rendezvous in Mars orbit for the crew leaving

Mars. The transportation strategy also

emphasizes the use of common elements to

avoid excessive development costs and to

provide operational simplicity.

The TMI stage (used to propel the

spacecraft from LEO onto a trans-Mars

trajectory) employs nuclear thermal

propulsion. Nuclear thermal propulsion was

adopted for the TMI burn because of its

performance advantages; its advanced,

previously demonstrated state of technology

development; its operational flexibility; and

its inherent mission enhancements. A single

TMI stage was developed for both piloted

and cargo missions. The stage is designed for

the more energetically demanding 2009 fast

transit trajectory and then used in the

minimum energy cargo missions to carry the

maximum payload possible to Mars. In the

human missions, the TMI stage uses four

15,000 lb. thrust NERVA (Nuclear Engine for

Rocket Vehicle Application)-derivative reactor

(NDR) engines (Isp = 900 seconds) to deliver

the crew and the surface habitat/descent

stage onto the trans-Mars trajectory

(Borowski, et al., 1993). After completion of

the two-perigee-burn Earth departure, the

TMI stage is inserted into a trajectory that will

not reencounter Earth or Mars over the course

of one millionyears. The TMI stage used with

the crew incorporates a shadow shield

between the NDR engine assembly and the

LH2

 tank to protect the crew from radiation

that builds up in the engines during the TMI

burns. Although it may seem wasteful to

discard the nuclear stage after one use, the

complexity of Mars orbit insertion and

rendezvous operations for the return flight

are avoided.

As shown in Figure 1-5, the same TMI

stage is used in all cargo missions, which

allows the transportation system to deliver

approximately 65 tonnes of useful cargo to the

surface of Mars or nearly 100 tonnes to Mars

orbit (250 × 33,793 km) on a single launch

from Earth. The TMI stage for cargo delivery

requires the use of only three NDR engines,

so one NDR engine and the shadow shield are

removed from the TMI stage, which reduces

cost and improves performance.

Mars orbit capture and the majority of

the Mars descent maneuver is performed

using a single biconic aeroshell. The decision

to perform the Mars orbit capture maneuver

was based on the facts that (1) an aeroshell

will be required to perform the Mars descent

maneuver no matter what method is used to

capture into Mars orbit, (2) the additional

demands on a descent aeroshell to meet the

Mars capture requirements were determined

to be modest, and (3) a single aeroshell

eliminated one staging event, and thus one

more potential failure mode, prior to landing

on the surface.

The crew is transported to Mars in a

habitat that is fundamentally identical to the
1-20

Figure 1-5 Reference Mars cargo and piloted vehicles.

2007 Cargo Mission 1

"Dry" Ascent Stage & Lander 2007 Cargo Mission 2 Hab Module & Lander 2007 Cargo Mission 3 LOX/CH4 TEIS & Hab 2

Surfac

"Expandabe TMI Stage LH2 (@ 18.2 m length) sizedby 2009 Mars Piloted Mission

86.0 t LH2(@ 100%)

86.0 t LH2(@ 100%)

86.0 t LH2

(@ 192.9%)

10 m 10 m 10 m

7.6 m

16.3 m

19.0 m

15.0 m 16.3 m

20.6 m*

4.7 m

IMEO = 216.6T 216.6T 204.7T 
1-21

surface habitat deployed robotically on a

previous cargo mission. By designing the

habitat so that it can be used during transit

and on the surface, a number of advantages to

the overall mission are obtained.

•Two habitats provide redundancy on the

surface during the longest phase of the

mission.

•By landing in a fully functional habitat,

the crew does not need to transfer from a

“space-only” habitat to the surface

habitat immediately after landing, which

allows the crew to readapt to a gravity

environment at their own pace.

•The program is required to develop only

one habitat system. The habitat design is

based on its requirement for surface

utilization. Modifications needed to

adapt it to a zero-g environment must be

minimized.

A common descent stage has been

assumed for the delivery of the transit/

surface habitats, the ascent vehicle, and other

surface cargo. The descent vehicle is capable

of landing approximately 65 tonnes of cargo

on the Mars surface. The landing vehicle is

somewhat oversized to deliver crew;

however, design of a scaled-down lander and

the additional associated costs are avoided To

perform the postaerocapture circularization

burn and the final approximately 500 meters

per second of descent prior to landing on the

Mars surface, the common descent stage

employs four RL10-class engines modified to

burn LOX/CH4

. The use of parachutes has

been assumed to reduce the descent vehicle’s

speed after the aeroshell has ceased to be

effective and prior to the final propulsive

maneuver. The selection of LOX/CH4

 allows

a common engine to be developed for use by

both the descent stage and the ascent stage,

the latter of which is constrained by the

propellant that is manufactured on the

surface using indigenous materials.

The ascent vehicle is delivered to the

Mars surface atop a cargo descent stage. It is

composed of an ascent stage and an ascent

crew capsule. The ascent stage is delivered to

Mars with its propellant tanks empty.

However, the descent stage delivering the

ascent vehicle includes several tanks of seed

hydrogen for use in producing the

approximately 30 tonnes of LOX/CH4

propellant for the nearly 5,600 meters per

second delta-V required for ascent to orbit

and rendezvous with the ERV. The ascent

vehicle uses two RL10-class engines modified

to burn LOX/CH4

.

The ERV is composed of the trans-Earth

injection (TEI) stage, the Earth-return transit

habitat, and a capsule the crew will use to

reenter the Earth’s atmosphere. The TEI stage

is delivered to Mars orbit fully fueled, where

it waits for nearly 4 years before the crew uses

it to return to Earth. It uses two RL10-class

engines modified to burn LOX/CH4

. These

are the same engines developed for the ascent

and descent stages, thereby reducing engine

development costs and improving

maintainability. The return habitat is a

duplicate of the outbound transit/surface
1-22

habitat used by the crew to go to Mars, but

contains consumables for the return trip only

and minimizes crew accommodations

required for the surface mission.

1.3.3.7 Surface Systems

The provision of adequate amounts of

electrical power is fundamental to a

successful exploration program. For the

transit phase, the need for power is less

severe than on the martian surface. Solar

energy is available for crew needs throughout

the cruise phase (the transit phase both to and

from Mars).

The selection of a power systems strategy

for surface operations is guided by risk

considerations, which require two-level

redundancy for mission-critical functions and

three-level redundancy for life-critical

functions. The surface power systems should

have 15+ year lifetimes to allow them to serve

the three mission opportunities with good

safety margins. Surface transportation power

systems should have 6+ year lifetimes to

minimize the need for replacement over the

program lifetime.

The strategy adopted for the Reference

Mission includes a primary and backup

nuclear reactor with dynamic energy

conversion. Each system is capable of

producing 160 kWe. Additionally, each habitat

retains the solar arrays used during transit,

and they can also be operated on the martian

surface. Due to several factors (for example,

the presence of an atmosphere, a day-night

cycle, etc.) each power system can produce

approximately 30 percent of the power

generated in space. For emergency situations,

the pressurized rover’s Dynamic Isotope

Power System can supply 10 kWe of

continuous power.

From a series of volume, mass, and

mission analyses, a common habitat structural

cylinder, 7.5 meters in diameter, bilevel, and

vertically oriented, was derived for the

Reference Mission. The three habitation

element types identified for the Reference

Mission (the surface laboratory, the transit/

surface habitation element, and the Earthreturn habitation element) will contain

substantially identical primary and secondary

structures, windows, hatches, docking

mechanisms, power distribution systems, life

support, environmental control, safety

features, stowage, waste management,

communications, airlock function, and crew

egress routes. The following are brief

descriptions of the unique aspects of the three

primary habitation elements developed for

the Reference Mission analysis.

•The Mars surface laboratory, sent out,

landed, and verified prior to the launch

of any crew members, will operate only

in 3/8 gravity. It contains a large,

nonsensitive (that is, no special

environmental control required) stowage

area with crew support elements on one

level and the primary science and

research lab on the second level. Future

development of this element includes

possible retrofitting of the stowage level

into a greenhouse as consumables and
1-23

resources are consumed and free volume

is created.

•The Mars transit/surface habitats

contain the required consumables for the

Mars transit and surface duration of

approximately 800 days (180 days in

transit and 600 days on the surface) as

well as all the required equipment for

the crew during the 180-day transfer

trip. This is the critical element that must

effectively operate in both zero and

partial gravity. Once on the surface of

Mars, this element will be physically

connected with the previously landed

surface lab thereby doubling the

pressurized volume for the crew.

Eventually, all four habitation elements

(the surface laboratory and three transit/

surface habitats) will be interconnected.

•The Earth-return habitat, functioning

only in zero g and requiring the least

amount of volume for consumables, will

be volume rich but must be mass

constrained to meet the limitations of the

TEI stage. Since little activity (other than

conditioning for the one-g environment

on Earth and training for the Earthreturn maneuvers) is projected for the

crew during this phase of the mission,

mass and radiation protection were the

key concerns in the internal architecture

concepts created.

Extravehicular activity (EVA) tasks

consist of maintaining the habitats and

surface facilities and conducting a scientific

exploration program encompassing geologic

field work, sample collection, and

deployment, operation, and maintenance of

instruments.

Mobility on several scales is required by

people operating from the Mars outpost.

Crew members outside the habitat will be in

pressure suits and will be able to operate at

some distance from the habitat, determined

by their capability to walk back to the

outpost. They may be served by a variety of

tools, including rovers, carts, and wagons. On

a local scale, perhaps 1 to 10 kilometers from

the outpost, exploration will be implemented

by unpressurized wheeled vehicles. Beyond

the safe range for exploration on foot,

exploration will be in pressurized rovers,

allowing explorers to operate for the most

part in a shirtsleeve environment.

The requirements for long-range surface

rovers include having a radius of operation of

up to 500 km in exploration sorties that allow

10 workdays to be spent at a particular

remote site, and having sufficient speed to

ensure that less than half of the excursion

time is used for travel. Each day, up to 16

person-hours would be available for EVAs.

The rover is assumed to have a nominal crew

of two people, but be capable of carrying four

in an emergency. Normally, the rover would

be operated (maneuvering from site to site,

transmitting high data rate communications,

supporting EVA activities, etc.) only in the

daytime, but could conduct selected

investigations at night.
1-24

1.3.3.8 Operations

Previous space missions have generally

cost more to operate than to design and

construct. This phenomenon was caused

partly by the fact that systems were designed

first and operations were developed to fit the

designs. The Reference Mission attempts to

bring operational considerations into the

process early to better balance the cost of

design and development with the cost of

operations.

1.3.3.8.1 Crew Operations

The principal difference between Mars

exploration and previous space ventures is

the requirement for crew operations in an

environment where on-call communications,

assistance, and advice from ground

controllers is not available in emergencies due

to the communications delay. This leads to a

set of operations requirements that:

•The crew be able to perform

autonomously for time-critical portions

of the mission.

•Highly reliable, autonomous system

operations be possible without intensive

crew participation.

•A balance be struck between ground

control and the crew on Mars which

optimizes the crew’s time and

effectiveness yet maintains their

independence and motivation to attain

mission objectives.

Thus, the Reference Mission will be

successful to the degree that ground and

flight crews can execute all activities which

lead to the accomplishment of mission

objectives. All crew activities throughout each

mission, from prelaunch through postlanding,

constitute crew operations and as such are

essential to the overall program. To enhance

program success, they must be factored into

all aspects of program planning. The majority

of crew activities fall into one of four

categories: training, science and exploration,

systems operations and maintenance, and

programmatics.

•Training includes activities such as

development of training programs,

development of training facilities and

hardware, prelaunch survival training

for all critical life support systems,

operational and maintenance training on

mission-critical hardware, prelaunch and

in-flight proficiency training for critical

mission phases, and science and research

training for accomplishing primary

science and exploration objectives.

•The majority of science and exploration

activities will be accomplished on the

surface of Mars and will include, but not

be limited to, operating TROVs,

habitability exercises, local and regional

sorties, and planetary science

investigations. Supplemental science

objectives may be accomplished during

other phases of the mission as well but

will be limited by the mass available for

onboard science equipment. Those

activities required for crew health and

safety (such as medical checks during
1-25

transit phases, monitoring solar activities

for flares, etc.) will be performed.

•During the first mission, a substantial

amount of crew time will be devoted to

the operation and maintenance of

vehicle systems. This time is expected to

decrease during subsequent missions as

both the systems and operational

experience bases mature. However,

maximizing the crew’s useful science

and exploration time will increase

overall mission effectiveness, and the

systems or procedures which contribute

to increasing this time and decreasing

routine operations and maintenance will

be incorporated wherever possible.

•Lastly, programmatic activities for flight

crews will include public relations,

documentation, reporting, and real-time

activity planning. Public relations

activities have been and always will be

an integral part of crew activities. While

these activities absorb resources, the

most significant of which is time, they

also bring public and political support to

the program and provide some of the

return on investment of the program.

Throughout all mission phases,

documentation of activities and feedback

on training effectiveness will be required

of all crews. This will be essential to

make effective use of the follow-on

crew’s training time and the program’s

training hardware and facilities. Many of

the mission-critical activities will be

planned and rehearsed in great detail

before each crew leaves Earth. However,

once on the surface of Mars, the very

nature of the work done by the crews

will require real-time activity planning

to take advantage of discoveries made as

the mission progresses.

No specific conclusions regarding

hardware requirements, facilities

requirements, training programs, and the like

were derived for this study. But a number of

recommendations and guidelines regarding

these areas have been developed and tailored

to the various mission phases that will be

experienced by each crew sent to Mars. While

these and other crew activities may not be

seen as directly affecting program success, all

areas contribute to the successful execution of

each mission and, therefore, are essential to

the overall success of the Reference Mission.

1.3.3.8.2 Earth-Based Support

The overall goal of Earth-based support

operations is to provide a framework for

planning, managing, and conducting

activities which achieve mission objectives.

Achieving this operational goal requires

successful accomplishment of the following

functions.

•Safe and efficient operation of all

resources. This includes, but is not

limited to, vehicles, support facilities,

training facilities, scientific and systems

data, and personnel knowledge and

experience bases.
1-26

•Provision of the facilities and an

environment which allow users (such as

scientists, payload specialists, and to an

extent crew members) to conduct

activities that will enhance the mission

objectives.

•Successful management and operation of

the overall program and supporting

organizations. This requires defining

roles and responsibilities and

establishing a path of authority. Program

and mission goals and objectives must

be outlined so that management

responsibilities are clear and direct.

Confusing or conflicting objectives can

result in loss of resources, the most

important of which are time and money.

In addition, minimizing the number of

layers of authority will help to prevent

operational decision-making activities

from being prolonged.

The Reference Mission, while large and

complex, has the added complication of being

a program with mission phases which cannot

be supported with near real-time operations.

Planetary surface operations pose unique

operational considerations on the

organization of ground support and facilities.

A move toward autonomy in vehicle

operations, failure recognition and resolution,

and mission planning is needed. And ground

support must be structured to support these

needs.

In general, due to the uniqueness of

planetary surface operations, Earth-based

support should be assigned the role of

managing and monitoring operations

planning and execution while crew members

will be assigned the actual responsibility for

operations planning and execution. Crew

members will be told what tasks to do or

what objectives to accomplish, but not how to

do it. This has the benefit of involving system

and payloads experts in the overall planning,

yet giving crews the flexibility to execute the

tasks. The proposed method for the Reference

Mission would take advantage of the unique

perspective of crew members in a new

environment but would not restrict their

activities because of the mission’s remote

nature. Additionally, it places the

responsibility of mission success with the

crew, while the overall responsibility for

prioritizing activities in support of mission

objectives resides with Earth-based support.

After dividing functional responsibilities

between Earth-based support and crew, the

support may be structured to manage the

appropriate functions. To accomplish mission

objectives while maintaining the first

operational objective of safe and efficient

operation of all resources, Earth-based

support can be organizationally separated

into systems operations and science

operations provided a well-defined interface

exists between the two. The systems

operations team would be responsible for

conducting the safe and efficient operation of

all resources, while the science operations

team would be responsible for conducting

activities which support scientific research.

Such an organizational structure would
1-27

dictate two separate operations teams with

distinct priorities and responsibilities yet the

same operational goal.

Systems operations are those tasks which

keep elements of the program in operational

condition and support productive utilization

of program resources. Thus, the systems

operations team has responsibility for

conducting the safe and efficient operation of

all such resources. The systems operations

team consists of representatives from each of

the primary systems (power, propulsion,

environmental, electrical, etc.) which are used

throughout the various mission phases.

The science operations team’s sole

function is to recommend, organize, and aid

in conducting all activities which support

scientific research within the guidelines of the

mission objectives. The team will consist of

representatives from the various science

disciplines (biology, medicine, astronomy,

geology, atmospherics, etc.) which support

the science and mission objectives. Each

scientific discipline will have an appropriate

support team of personnel from government,

industry, and academia who have expertise in

that field. The science operations team will act

as the decision-making body for all science

activities—from determining which activities

have highest priority to handling and

disseminating scientific data.

Crew and vehicle safety are always of

primary concern. When those are ensured,

science activities become the highest priority.

To accommodate this hierarchy of priorities

within the operations management structure,

the overall operations manager should reside

within systems operations. A science

operations manager, who heads the science

operations team, should organizationally be

in support of the operations manager. Various

levels of interfaces between systems engineers

and science team members must exist to

maximize the amount of science and mission

objectives that can be accomplished.

1.3.3.9 Mission and Systems Summary

To summarize, the major distinguishing

characteristics of the Reference Mission

include:

•No extended LEO operations, assembly,

or fueling.

•No rendezvous in Mars orbit prior to

landing.

•Short crew transit times to and from

Mars (180 days or less) and long surface

stay-times (500 to 600 days) for the first

and all subsequent crews exploring

Mars.

•A heavy lift launch vehicle capable of

transporting either crew or cargo direct

to Mars, and capable of delivering in

four launches all needed payload for the

first human mission and in three

launches for each subsequent

opportunity.

•Exploitation of indigenous resources

from the beginning of the program, with

important performance benefits and

reduction of mission risk.
1-28

•Availability of abort-to-Mars surface

strategies, based on the robustness of the

Mars surface capabilities and the cost of

trajectory aborts.

•Common transit/surface habitat design.

•Maintenance of a robust, safe

environment for crews throughout their

exploration.

•Substantial autonomy of crew and

system operations from ground control.

1.4 Testing Principal Assumptions

and Choices

A number of assumptions and choices

were made in constructing this Reference

Mission. For each assumption, this section

provides a top-level trade analysis, the

rationale for the choice, and guidance to

further research and development which

could strengthen, improve, or change the

choice.

1.4.1 Robust Surface Infrastructure

The principal payoff from Mars

exploration lies in surface capability—staytime, crew safety, exploration range, and

other factors that characterize the crew’s

performance environment. All dictate a

robust infrastructure. The choice to land all of

the payloads and crews at the same site on

four different opportunities was based on the

assumption that the marginal cost of

additional surface capability would be a costeffective way to substantially increase the

accomplishment of the program.

Two different approaches have been

proposed in the past. The first is comparable

to the Reference Mission by the long stay-time

on the martian surface. The second involves a

short stay-time (<30 days on the martian

surface) mission. Table 1-1 characterizes

principal discriminators of the two scenarios.

In most studies, the short stay-time

missions have only been invoked for the first

mission; to develop long stay-time capability

would require close to total mission redesign

and much higher cost for a continued

program.

The second alternative is to land each

crew at a different location. This scenario

would be permitted by the capability defined

in the Reference Mission. The principal tradeoff is between the additional exploration that

might be accomplished by exploring three

distant sites versus the benefits of building up

the capability to test settlement technologies

(such as closed life support systems) and the

reduced risk provided by accumulating

surface assets at one site. As the range of

exploration provided in the single location

Mars outpost is high (hundreds of

kilometers), the advantages of exploring

several landing sites were considered of lower

priority for the Reference Mission.

1.4.2 Split Mission Strategy

The split mission strategy takes

advantage of the currently available

capability to successfully fly and land

automated spacecraft on another planet. Such

capability can be used to deliver supplies and
1-29

Table 1-1 Principal Discriminators of Short and Long Stay-Time Mission Scenarios

Long Stay-Times Short Stay-Times Key

Discriminating Factor

Surface High Low Difference in time

Accomplishment on surface

Surface Low High Robust vs. limited

risk/day surface capability

Surface Low Low Difference of time

risk/cumulative vs. robustness

Interplanetary risk Low High

Available to Yes No

direct launch

Available to Yes Difficult

split mission

Abort to Mars Yes No

surface

Availability of Mars Yes No

at every opportunity

equipment to support human missions

without a crew being present. By using this

capability to deliver cargo not absolutely

necessary for transporting crews between

Earth and Mars, the size of the transportation

system (both launch vehicles and upper

stages) for any one mission becomes smaller

and thus less expensive to develop and

manufacture. In addition, these cargo

missions can be sent on the absolute

minimum energy trajectories between Earth

and Mars because there is no time-critical or

life support critical element on board.

However, the total number of launches

increases under this strategy which offsets at

least part of the cost savings due to the

increased number of transportation elements

that must be used.

The split mission strategy is contrasted

with the “all-up” approach in which a single

vehicle, assembled in LEO, is capable of

landing the required assets in a single mission

to the surface. The principal trade-off is

between rendezvous and assembly in LEO

and rendezvous on the Mars surface. For the

all-up approach, significant capability is

required in LEO to assemble and fuel the

spacecraft. Previous designs (the 90-Day

Study; see NASA, 1989) projected very high

LEO infrastructure costs, which would have

to be expended in the early phases of the

program. For chemically propelled spacecraft,
1-30

the logistics of transporting, storing, and

loading propellants was excessive and

inevitably high in cost. Because the best

departure orbit at Earth is different for each

Mars opportunity, the space-based

infrastructure would have to be moved or

reproduced, or additional propulsion

penalties be taken to modify the vehicle’s

departure orbit for every launch to Mars. The

elimination of this element in the architecture

provides a significant cost reduction. It has

been assumed here that the capability of very

precise landing on Mars can be developed

technically, and that all assets for each flight

can be integrated on Earth and simply joined

on Mars. These capabilities can be

demonstrated on precursor robotic missions.

While the savings resulting from a

smaller transportation system may not alone

be sufficient to invoke the use of the split

mission strategy, the strategy does enhance

another assumed element of the Reference

Mission—the use of in situ resource

utilization. By splitting the missions into

cargo and crew flights, infrastructure can be

set up and operated before committing a crew

to a flight to Mars. Operating this

infrastructure for an extended period prior to

launching a crew also improves the

confidence of using the Mars surface as a safe

haven for the crew.

1.4.3 Nuclear Thermal Propulsion

High-performance propulsion is found to

be an enabling technology for a human

exploration program. Nuclear thermal

propulsion was selected because of its higher

propellant utilization efficiency and because

nuclear rockets were developed almost to

flight status in the 1960s. For any given

velocity change needed to depart from or be

captured at a planet, a nuclear thermal rocket

uses approximately 50 percent less propellant

than the theoretical best chemical engine. (The

Space Shuttle main engine is approaching this

theoretical upper limit.) The vast majority of

mass needed for a Mars mission is propellant,

and any option that reduces the need for

propellant can lower the program life cycle

cost by reducing the size and number of

launch vehicles. Although such rockets might

be expensive to test on Earth (the magnitude

of which has not been determined) with

current environmental concerns, their use in

space should not present an environmental

issue for they are dangerous only after firing

the engines for a significant period of time.

Higher performance engines would be better,

but typically require a large source of

electrical power (from either a nuclear source

or very large solar arrays) which calls for

additional development to reach the same

level of maturity as nuclear thermal rockets.

1.4.4 In Situ Resource Utilization

This technology (assumed to be currently

available) has been developed at breadboard

level and can be demonstrated on robotic

missions. It provides significant benefits to

the mission by reducing launch mass from

Earth and increasing robustness of surface

systems where caches of consumables and
1-31

surface vehicle fuels can be maintained. As

discussed in the previous section, any

technology that can reduce the amount of

mass (and propellant is the largest single item

on such a list) can do much to reduce life

cycle cost. This is accomplished primarily by

reducing the size and number of launches

from Earth and by providing a dual purpose

infrastructure that not only provides

propellants for a return trip but also supports

crew activities and helps reduce risk.

1.4.5 Common Habitat Design

A common habitat was chosen for the

Reference Mission primarily to save on cost

over the life of the program. Because seven

separate habitats will be required to support

the three crews sent to Mars, this item

becomes a likely candidate for a common

approach rather than designing, testing, and

building separate systems for the

interplanetary leg, the surface leg, and the

transition between the two. It may not be

feasible to use a common design for all of the

components that make up a habitat. However,

some of the significant elements—such as the

pressure vessel (both primary and secondary

structure), electrical distribution, hatches, and

docking mechanisms—lend themselves to a

common approach. Inasmuch as these major

elements of the habitat can be defined and

their cost estimated, a common design for the

habitats has been adopted for the Reference

Mission. A significant amount of work still

remains on definition and design of interior

details of the habitats which will become part

of future efforts associated with Mars mission

planning. Study team members were not

unanimous in the choice of a common habitat

for space transit, for landing on the surface,

and for surface habitation. Some argued that,

due to the different requirements, a common

design was not in the best interest of the

mission. This is an area for further research.

1.4.6 Nuclear Surface Power

With no known natural resources on

Mars that can be used to generate power, a

crew exploring Mars must rely on either

converting solar radiation or using a power

source they have brought with them. With

Mars lying, on average, 50 percent farther

from the Sun as Earth, only 44 percent as

much solar radiation reaches that planet. This

means a crew must bring 2.25 times as much

solar energy collecting and converting

systems to generate the same amount of

power as could be generated on Earth. Add to

this a day-night cycle (which requires the

addition of an energy charging and storage

system) as well as martian dust storms (which

significantly diminish the amount of light

reaching the surface over extended periods of

time) and the size of a solar power station on

Mars becomes both large in area and mass

and subject to interruption or diminished

effectiveness due to the dust storms. Of those

sources of energy that can be brought with

the crews, only a nuclear power source can

concentrate sufficient energy in a reasonable

mass and volume. However, other concerns—

environmental on Earth, operational on Mars,

to name a few—are added to any mission that

considers the use of a nuclear power source.
1-32

Given these kinds of considerations, a

choice was made to rely primarily on nuclear

power for systems operating on the martian

surface. Power provided by the solar arrays

used during the transit to Mars will be

available for backup and emergency

situations. However, the solar arrays will not

be sufficient to power the propellant

manufacturing plants that are also a key

feature of this mission architecture.

1.4.7 Abort to the Surface

Mars missions differ from Space Shuttle

and lunar missions in that once the crew is

committed to launch, orbit mechanics force

the crew to remain away from Earth for

approximately 2 to 3 years. This imposes on

all of the systems the need for a higher degree

of reliability and maintainability or for

multiple independent means of providing

life-critical functions (collectively referred to

as robustness).

There has been a tendency to view the

martian surface as the most hostile location

for a crew during a Mars mission. However,

of the three environments that a crew will

encounter—Earth, interplanetary space, and

the martian surface—interplanetary space

offers the highest potential for debilitating

effects on the crew. Practicality dictates a

relatively small habitable space for the crew

during transit. To do otherwise causes a

corresponding increase in the size and cost of

the systems, primarily launch vehicles and

transfer stages, associated with the

transportation system. But to confine the crew

to a small habitable space for an extended

duration can lead to cabin fever. Zero g has

known debilitating effects on the human body

that must be addressed. Radiation from a

constant background and the threat of solar

flares require that protection be adequate for

background sources and that a safe haven be

provided for extreme events. All of these

threats have engineering solutions that can

make the extended stay in interplanetary

space a viable prospect for the crew. But the

solutions typically require increases in size,

mass, and complexity of the vehicle and the

transportation elements that are used to move

it from planet to planet.

An alternate strategy, and one that was

selected for this Reference Mission, is to take

advantage of the martian surface as a safe

haven where open space, gravity, and

radiation protection are naturally available.

This strategy, referred to as “abort to the

surface,” builds on these naturally available

resources and breaks from the previous

viewpoint of Mars as the most hostile

environment encountered on the mission. The

reliability and maintainability of the systems

needed to keep the crew alive on the surface

is no greater than that imposed on spacebased systems. In fact, the buildup of an

infrastructure at a single site on the surface

enhances the safe haven character of the

martian surface. This approach places a

greater burden on the entry, landing, and

martian-based launch systems. However, the

trade-off of making these systems a viable

part of the abort strategy through increased
1-33

redundancy and reliability versus the

enhancements needed to sustain a crew

through a 2- to 3-year interplanetary abort

have tended to favor the abort to the surface

strategy. The enhancements that will be made

to various systems to allow an abort to the

surface also work to the advantage of the

overall mission by improving the chances of

the crews to successfully reach the surface

and perform their exploration activities.

1.4.8 Design for the Most Difficult

Opportunity

The design of the Reference Mission was

based on the premise that a series of closely

spaced missions would result in costs

significantly lower than the sum of an

equivalent number of single missions. To

achieve this cost savings requires that a single

set of systems be designed which can

accomplish the mission under the most

difficult circumstances of any single

opportunity. The most significant of these

variations results from trajectory differences

that occur during sequential mission

opportunities. As a result, some systems may

have excess capability during some years.

However, this allows the advantage of either

launching more payload mass in those years

with more favorable trajectories or reducing

mission durations by flying shorter trajectory

legs, but at the expense of greater fuel

consumption. For example, in the 2009

opportunity, transit times for piloted missions

are approximately 6 months; using the same

systems in the 2018 opportunity reduces

transit times to just 4 months.

1.5 Conclusions and Recommendations

Based on both mission and programmatic

points of view, a number of conclusions and

recommendations are made in the following

areas: mission and systems, technology

development, environmental protection,

program cost, international participation, and

program management and organization.

1.5.1 Mission and Systems

Conclusions

A feasible mission scenario and suite of

vehicles and other systems have been

integrated to meet the objectives initially set

out for this study. In addition, the Reference

Mission addresses a long-standing issue

regarding extended-duration flights and crew

safety by adopting a view that the surface of

Mars is a safe haven and that equipment and

procedures should be developed with this in

mind.

The Reference Mission includes

technology assumptions which require

further development and which contribute to

an estimated development cost that is higher

than can currently be supported. Both

technology and cost must be addressed and

the alternative missions and systems could

result in a better program for human

exploration of Mars. However, the mission

and systems described here substantially

reduce the program cost and at the same time

present a more robust approach than in

previous studies of this subject.
1-34

Recommendations

•Use this study as an informal baseline

against which future alternatives should

be compared.

•Continue investigating alternative

mission scenarios and systems to

improve this Reference Mission, or

suggest a better alternative.

1.5.2 Technology Development

Conclusions

The Reference Mission was developed

assuming advances in certain technology

areas thought to be necessary to send people

to Mars for a reasonable investment in time

and resources. The Reference Mission is not

intended to lock in these assumed

technologies. The purpose of identifying

technologies at this time is to characterize

those areas that can either significantly reduce

the required mass or cost of the program or

significantly reduce its risks (for example, in

the area of fire safety). Alternative means of

satisfying these requirements may be

identified and, if promising, should be

supported. The alternatives could be the

result of a dual use development, spin off

from other programs, or a fortunate “spill

over” from some unexpected area.

At this particular stage in developing

human exploration missions to Mars, it is

difficult to do more than speculate about spin

off and spill over technologies that could

result from or be useful to this endeavor.

However, identifying dual uses for some of

the assumed technologies can be started now

and, to a certain degree, may be required for

such a program to progress. In the current

political environment, investment in

technology is seen as a means of improving

the general quality of life for people on Earth,

and multiple use of technologies is

emphasized to obtain the best return on the

resources invested in their development. The

following is a list of twelve technologies

which are important to space transportation,

humans living in space or on a planetary

surface, or the utilization of extraterrestrial

resources.

Resource Utilization

•Extraterrestrial mining techniques

•Resource extraction process and

chemistry

•Material preparation and handling in

reduced gravity

•Extraterrestrial manufacturing

Transportation and Propulsion

•Advanced chemical systems that provide

high performance and are compatible

with the resources available on the Moon

and Mars

•Nuclear propulsion to enable short trip

times to Mars

•Aerocapture/aerobraking at the Earth

and at Mars for propulsive efficiency

and reusable systems

•Lightweight/advanced structures

• Reduced-g combustors
1-35

Cryogenic Fluid Management

•Long-term (years) storage in space

•Lightweight and high efficiency

cryogenic liquefaction

•Zero g and microgravity acquisition,

transfer, and gauging

EVA Systems

•Lightweight, reserviceable, and

maintainable suit and PLSS

•Durable, lightweight, high mobility suits

and gloves

Regenerative Life Support Systems

•Contamination and particle control

•Loop closure

•Introduction of locally produced

consumables

•Food production

•Trash and waste collection and

processing

•High efficiency and lighter weight active

thermal control systems

Surface Habitation and Construction

•Lightweight structures

•Seal materials and mechanisms

•Construction techniques using local

materials

Human Health and Performance

•Zero-g adaptation and countermeasures

•Human factors

•Health care at remote locations

•Radiation protection in transit and on

surface

Power Generation and Storage

•Long life, lighter weight, and less costly

regenerative fuel cells

•Surface nuclear power of the order of

100kw

•High efficiency solar arrays

Teleoperations/Telerobotics

•Remote operations with long time delays

•Fine control manipulators to support

wide range of surface activities

•Telepresence sensors and displays

Planetary Rovers

•Long range (hundreds of km) rovers

•Motor lubricants (long-term use)

•Dust control

•High efficiency lightweight power

generation and storage

Advanced Operations

•Automated systems control

•Systems management and scheduling

•Simulations and training at remote

locations

Fire Safety

•Fire prevention

•Fire detection

•Fire suppression
1-36

Some of these technologies (such as

nuclear thermal propulsion, Mars surface

space suits, and in situ resource extraction), at

the system level, are unique to the Reference

Mission or to human space exploration in

general. It is likely that NASA or cooperating

international partners will have to bear the

burden for support of this research and

development. The Reference Mission, as it is

described here, will fail if these systems are

not advanced to a usable state. Other areas,

such as medical countermeasures, closed-loop

life support systems, autonomous operations

systems, surface power systems, and surface

mobility, may be of more general interest and

may provide opportunities for government

and industry to develop shared programs. In

still other areas, such as long-lived electronics

and materials research, where the underlying

research will probably be done by industry to

address general problems of technology

development, NASA or the international

partners should focus on infusing that

technology. The exchange of information

should be continuous between NASA and the

commercial sector particularly concerning the

needs of future missions, so that industry can

incorporate research into its privately funded

programs where it is justified. In all areas,

subsystem or component technologies may be

developed by industry to meet commercial

requirements, and the Mars Program will

need to have processes that allow the element

designers to use the most advanced

capabilities available.

Recommendations

•Establish a Mars Program Office

(discussed further under International

Participation and Management and

Organization) early in the process (now,

probably) at a low level to lay the

foundation for technology requirements

to be undertaken by NASA or other

government agencies with similar

requirements. Formal organizational

agreements should exist between these

offices if the technology development is

not formally assigned to the Program

Office.

•Rank technology investments according

to their return to the Program, as either

cost or risk reductions.

•Prior to initiation of the Reference

Mission, take critical technologies to a

demonstration stage. NASA should

ensure that experimental work in

support of the Reference Mission is

incorporated into the International Space

Station program at the earliest

reasonable time.

•Create a database (in the Program Office)

of available technologies that can be

used in design studies, and track the

progress of these technologies. The

database should include domestic and

international capabilities.
1-37

1.5.3 Environmental Protection

Conclusions

Fundamental principles of planetary

environmental protection have been

developed since the first planetary

exploration missions began in the 1960s. With

respect to Mars, the principles adopted by the

international scientific community are

straightforward: Mars should be protected

from biological contamination from Earth that

would interfere with or confound the search

for natural martian organisms, and Earth

must be protected from contamination by

martian organisms harmful to the terrestrial

biosphere. The United States is signatory to a

treaty under the auspices of the Committee on

Space Research (COSPAR) which provides the

basic framework for its Planetary Protection

policy and program (COSPAR 1964 and

United Nations 1967).

Planetary protection will be an ongoing

discussion at an international level. The

policy principles stated here and those that

evolve in the future must be carried along as

significant requirements for mission planning

and system design.

A further political concern is

unfortunately tied to the planet Mars. A

significant portion of the popular press and

the entertainment industry is devoted to

speculation about life, intelligent and

otherwise, that may exist beyond the planet

Earth. Percival Lowell, H. G. Wells, Orsen

Wells, and others have placed Mars in the

forefront of possible locations for

extraterrestrial life. NASA itself has

contributed to this perception by supporting

legitimate scientific research in this area.

Because it is not possible to prove that Mars is

completely devoid of life, there is the

potential for misinterpretation or

misunderstanding when martian materials

and human crews are brought back to Earth.

For example, an ailment (regardless of the

source) among a returning human crew could

give rise to speculation that the crew has

some unknown Mars “bug” and is about to

expose the rest of the human population to its

effects.

Recommendations

•Develop adequate and acceptable

human quarantine and sample handling

protocols early in a Mars exploration

program. The protocols must address

not only the purely scientific concerns to

maintain the pristine nature of samples

but also the societal concerns, real or

imagined, that are likely to arise.

•Include the protocols as program-level

requirements for mission and system

development.

•Publicly release for review (by

independent authoritative bodies) the

principles and practices of

contamination control in effect for Mars

missions.
1-38

1.5.4 Program Cost

Conclusions

The cost of the Reference Mission was

estimated using standard models. Input for

these models was derived from previous

experience and information provided by

members of the Study Team. Included in the

estimate were the development and

production costs for all of the systems needed

to support three human crews as they explore

Mars. In addition, ground rules and

assumptions were adopted that incorporated

some new management paradigms, as

discussed later in the Program Management

and Organization section. The management

costs captured program level management,

integration, and a Level II function. Typical

pre-production costs, such as Phase A and B

studies, were also included.

Not included in the cost estimate were

selected hardware elements, operations, and

management reserve. Hardware costs not

estimated include science equipment and EVA

systems, for which data were not available at

the time estimates were prepared; however,

these are not expected to add significantly to

the total. No robotic precursor missions are

included in the cost estimate although their

need is acknowledged as part of the overall

approach to the Reference Mission.

Operations costs have historically been as

high as 20 percent of the development cost.

However, due to the extended operational

period of the Reference Mission and the

recognized need for new approaches to

managing and running this type of program,

estimating the cost for this phase of the

program was deferred until an approach is

better defined. Similarly, the issue of

management reserve was not addressed until

a better understanding of the management

approach and controls has been developed.

When compared to earlier estimates of a

similar scale (NASA, 1989), the cost for the

Reference Mission is approximately an order

of magnitude lower. A distribution of these

costs is shown in Figure 1-6. It can be seen

from this figure that the major cost drivers are

those associated with the transportation

elements: the ETO launch vehicles, the TMI

stages, and the Earth-return systems.

The Mars Study Team recognizes that,

even with the significant reduction in the

program cost achieved by this Team, the

Reference Mission is probably still too

expensive in today’s fiscal environment. More

work to further reduce these costs is needed.

Recommendation

•Seek alternative solutions or effective

approaches to cost reduction in each of

the areas cited above. The efforts may

require revolutionary changes

throughout NASA, the aerospace

industry, the United States, and the

world.
1-39

1.5.5 International Participation

Conclusions

The human exploration of Mars should

be inherently an international, indeed a

global, undertaking. Just as the U. S. landing

on the Moon excited and amazed the world at

U. S. technological skills and organizational

accomplishment, the human exploration of

Mars can excite and amaze the people of the

world with a commonly sought level of

technological prowess and organizational

capability. The International Academy of

Astronautics’ International Mars Exploration

Study (IAA 1993) describes in more detail the

rationale and possible organizational

approaches to an international Mars

exploration program.

The Reference Mission is rich in

possibilities for multinational or even global

participation. Many major elements, systems,

and subsystems will have to be developed

and produced, precursor missions must be

developed and flown, and operations

capabilities must be developed; and the

mission operations can be designed to be

undertaken on an international basis. Three

types of international participants may

Surface Systems

8%

Phase A & B

2%

Habitats

12%

Cost of

Facilities

8% Mgmt, Adv. Devel.,

Program Support

12%

Figure 1-6 Distribution of Reference Mission costs.

Earth to Orbit Vehicle

Earth to Mars Vehicle 26%

18%

Descent Vehicle

6%

Mars to Earth

Vehicle

11%
1-40

contribute based on the ability to provide

resources and participate technically in the

program.

•Countries with limited resources and

technical base. Their participation could

be linked to technology transfer to their

countries, which could improve the level

of technical education and take

advantage of technical internship in the

endeavor. These relationships might be

similar to the participation of Cuba or

Viet Nam in the Russian space program.

•Countries with greater amounts of

resources and technical base. Their

participation would reflect technical

interest in limited areas targeted for

technical or industrial growth in their

economies. The participation of Canada

in the International Space Station

program is an example.

•Countries with substantial resources and

technical base. Their participation would

reflect a desire to demonstrate world

leadership, retain broad technological

skills, and promote aerospace industry.

The major contributors to the

International Space Station program fall

into this category.

All participating countries should expect

to gain in proportion to their investment in

the enterprise; richer countries might view

the program as an opportunity to help poorer

countries improve their standards of living

through stimulation and transfer of modern

technology and technological training.

The ranges of opportunities and interests

are large and must be well understood before

an international program is constructed. The

discussions may be iterative with respect to

initial design in order to optimize the

collective returns to all nations in the

program, and it is not unlikely that 10 years

would be needed to formulate the principles

and agreements needed to undertake the

program. It is important that these

discussions lead to a set of basic principles

under which the program will be designed

and implemented.

Recommendations

•Make the human exploration of Mars

program international from its inception,

and take as a basic principle that all

partners will have a voice in all phases of

the program in proportion to the

resources contributed to the program.

•Do not exclude any nation even though

their participation might be small in

economic terms.

•Create a forum in the near future for

discussion of the elements of an

international program to lay the basis for

international participation.

•Create an International Program Office

(sensitive to political and technical

issues) to lead the design effort. Just as it

is important to have all of the design

requirements understood prior to

development, all of the political

requirements must also be understood

early in the process.
1-41

1.5.6 Program Management and

Organization

Conclusions

Organization and management is one of

the principal determinants of program cost.

This is a rather wide-ranging topic, which is

not entirely divisible from the technical

content of the program, because it includes

program level decision-making that is

intimately tied to the system engineering

decision-making process. The relationship

between program cost and program culture

(Figure 1-7) is an indication of that

relationship.

The relationship between cost and

management style and organizational culture

is rather well-known in a general manner,

through a large number of “lessons learned”

analyses made postprogram. The list of key

elements of lower-cost programs (shown in

Table 1-2) have been pointed out in a series of

analyses, but have not commonly been

applied at the critical stage of developing

program organization and management

approaches. The organizational and

management style has been determined

rather late in the program, generally because

the program content and final design was

typically delayed through redesign, changing

requirements, and funding irregularities. For

example, the International Space Station

program went through several redesigns, and

some of the hardware was actually in

production when the program architecture

was modified to integrate the Russian and Figure 1-7 Relationship between

program cost and program culture.

Space Station Freedom programs. To manage a

Mars exploration program to a lowest possible

cost, several recommendations are proposed.

Recommendations

•In subsequent studies of the Reference

Mission, investigate the design of the

organization and management system.

•Reach a formal philosophical and budgetary

agreement (between all parties) as to the

objectives and requirements imposed on the

mission before development is initiated, and

agree to fund the project to its completion. In

the U. S., this would include multiyear

budgetary authority. This should be

accompanied by a management process that

would protect against program overruns

through appropriate incentives.

•Prepare a risk management plan. The human

exploration of Mars will have risks that are

quite different from any space mission

previously undertaken. Two general types of

Relative Cost Spacecraft

Aircraft

Ships Trucks

Specifications

+Difficulty

+
1-42

risk seem to be most critical: risks to the

safety of the crew and accomplishment

of the mission (primarily technical risks)

and risks of not meeting cost and

schedule objectives. Maintaining launch

schedule is important due to the

dependency on several successful

launches for mission success and the

high cost of missed launch windows.

Failure to maintain the launch schedule

implies a 2-year program delay at a

potentially high program cost.

•Establish a clear demarcation between

the design phase and the development

and production phase of the project, and

do not allow development to begin

before the design phase is ended. Prove

all technologies prior to initiating

production of program elements. Do not

change requirements after they are

established unless they can be relaxed.

Ensure that a system to document the

relationship and interaction of all

requirements exists and is available for

Table 1-2 Key Elements of Lower-Cost Programs

•Use government only to define requirements.

•Keep requirements fixed: once requirements are stated, only relax them; never add new

ones.

•Place product responsibility in a competitive private sector.

•Specify end results (performance) of products, not how to achieve the results.

•Minimize government involvement (small program offices).

•Ensure that all technologies are proven prior to the end of competition.

•Use the private sector reporting system: reduce or eliminate specific government

reports.

•Don’t start a program until cost estimates and budget availability match.

•Minimize or eliminate government-imposed changes.

•Reduce development time: any program development can be accomplished in 3 to 4

years once uncertainties are resolved.

•Force people off of development programs when development is complete.

•Incentivize the contractor to keep costs low (as opposed to CPAF, CPFF of NASA).

•Use geographic proximity of contractor organizations when possible.

•Use the major prime contractor as the integrating contrator.
1-43

use prior to the beginning of production.

The Reference Mission requires a

number of elements, many of which are

technically alike but serve somewhat

different functions over the duration of

the program. For example, the surface

habitat may be the basis for the transit

habitat; each of the habitats delivered to

the surface will have a different

complement of equipment and supplies,

according to its position in the delivery

sequence. The elements will be

developed over a period of several years,

and there will be a temptation to

improve the equipment and supply

manifest. To maintain cost control for the

program, requirements must be fixed at

the time of initial development.

•Provide clear requirements for the

design phase, describing the

performance expected and a clear set of

criteria for completeness of design as a

function of resources expended in

design. Use a significant design cost

margin to manage the design resources.

Terminate the project if a satisfactory

design cannot be accomplished within

the available resources. Further, select

the successful prime contractor as

integration contractor for the

development phase, and exclude the

prime contractor as a development

contractor. The design phase of the

program is critical to successful cost

control, and should be based on a set of

functional requirements established by

the Program Office (which may well be a

multinational activity). The Program

Office will be in place to manage

technical requirements, provide

decisions that require consultation and

trade-offs (both technical and political),

and manage development contracts. The

Program Office should establish

functional requirements for the design

phase and conduct a competitive

procurement for the design phase, with

the selection of a prime contractor.

•Prepare a specific construction sequence

and plan to accompany each production

element of the program. Once

committed to development, the

development time should be strictly

limited if costs are to be contained. This

will be difficult in the Mars program,

where it probably will be effective to

produce common elements sequentially

rather than all at one time, although

there may be a high enough production

rate that costs will drop as experience is

gained. A new approach will be needed

to ensure that the development time for

each individual element is strictly

limited.

•Make the two levels of integration,

program and launch package, the

responsibility of a single organization—a

prime contractor to the Program Office.

The program will require two levels of

integration, similar to that of the

International Space Station program: a

program level which ensures that overall

mission requirements are met at each
1-44

stage of the mission, that is, for the

packages assembled for each launch

opportunity; and a launch package level

integration, in which all required

elements of each launch to Mars are

packaged and their performance

ensured.

•Include operational considerations in the

design and development phases of the

program, and use life cycle costs for

program design and development

decisions. The operational phase of the

Mars program must be represented in

the design and development phase. This

will require a concurrent engineering

approach which considers the

operational costs as well as the

development costs in a life cycle cost

approach to the program. If the

approaches identified above to separate

design and development and to obtain

prior commitments for funding for the

entire program are successful, there

should be less of a problem maintaining

the life cycle cost approach to

minimizing program costs.

•Put into place positive incentives to

maintain program costs within approved

levels at all stages of design,

development, production, and

operations, and to reduce costs of each

phase of the program.

1.6 References

Borowski, S. K., R. R. Corban, M. L.

McGuire, and E. G. Beke, “Nuclear

Thermal Rocket/Vehicle Design Options

for Future NASA Missions to the Moon

and Mars,” NASA Technical

Memorandum 107071, 1993.

Committee on Space Research (COSPAR),

“Statement on the Potentially Harmful

Effects of Space Experiments Concerning

the Contamination of Planets,” COSPAR

Information Bulletin No. 20, pp. 25-26,

Geneva, Switzerland, 1964.

Duke, M. and N. Budden, “Results,

Proceedings and Analysis of the Mars

Exploration Workshop,” JSC-26001,

NASA, Johnson Space Center, Houston,

Texas, August 1992.

International Academy of Astronautics

(IAA), “International Exploration of Mars:

A Mission Whose Time Has Come,” Acta

Astronautica, Vol. 31, pp. 1-101, New York,

USA, October 1993.

United Nations, “Treaty on Principles

Governing the Activities of States in the

Exploration and Use of Outer Space,

Including the Moon and Other Celestial

Bodies,” U.N Document A/RES/2222/

(XXI), TIAS #6347, New York, USA,

January 1967.

NASA, "Report of the 90-Day Study on

Human Exploration of the Moon and

Mars," NASA Headquarters, Washington,

DC, November 1989.
1-45

Synthesis Group, “America at the

Threshold: Report of the Synthesis Group

on America’s Space Exploration

Initiative,” U.S. Government Printing

Office, Washington DC, May 1991.

Zubrin, Robert, “Mars Direct: A Simple,

Robust, and Cost Effective Architecture

for the Space Exploration Initiative,”29th

Aerospace Sciences Meeting, AIAA 91-

0326, held in Reno, Nevada, January 7-10,

1991.

2-1

2. Science and

Exploration Rationale
2-2
2-3

2.1 Introduction

Mars is an intriguing and exciting planet

with many adventures and discoveries

awaiting planetary explorers. But before we

go, we must provide the tools the explorers

will use, anticipate as much as possible the

situations they will encounter, and prepare

them for the unexpected. For the first time in

a space exploration mission, it will be up to

the crew and supporting personnel on Earth

to create specific activities as the mission

progresses and discoveries are made. The

length of time spent on the martian surface, as

presented in the Reference Mission, will

preclude development of the detailed, highly

choreographed mission plans typical of

today’s space missions. The crew will have

general goals and objectives to meet within

their other time constraints (for example,

exercise for health maintenance, regular

medical checks, routine systems maintenance,

etc.). Based on knowledge gained from

precursor robotic missions, the crew will land

in an area that has a high probability of

satisfying the pre-set mission objectives.

However, due to the extended

communications time lag between Earth and

Mars, the crews and their systems must be

able to accomplish objectives in a highly

autonomous manner with only general

support from Earth. From the rationale

generated by the Mars Study Team for

sending human crews to Mars, goals and

objectives are derived to provide guidance for

the exploration crews during their extended

stay on the martian surface. This section will

discuss that Study Team rationale.

2.2 The “Why Mars” Workshop

In August 1992, a workshop was held at

the Lunar and Planetary Institute in Houston,

Texas, to address the “whys” of Mars

exploration. This workshop brought together

a group of experts (listed in Table 2-1) familiar

with the key issues and past efforts associated

with piloted Mars missions in an effort to

provide the top-level rationale and

requirements from which the Mars

exploration program could be built (Duke

and Budden, 1992). This group was asked to

generate three key products: a Mars mission

rationale, Mars exploration objectives, and a

list of key issues and constraints, to be used

by the Mars Study Team (members listed in

Table 2-2) to define the technical details of a

Reference Mission. The workshop attendees

identified six major elements of the rationale

for a Mars exploration program.
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Table 2-1 Mars Exploration Consultant Team

Dr. George Morgenthaler

University of Colorado

Boulder, Colorado

Dr. Robert Moser

Chama, New Mexico

Dr. Bruce Murray

California Institute of Technology

Pasadena, California

Mr. John Niehoff

Science Applications International

Corporation

Schaumburg, Illinois

Dr. Carl Sagan

Center for Radiophysics and Space

Research

Cornell University

Ithica, New York

Dr. Harrison Schmitt

Apollo 17 Astronaut

Albuquerque, New Mexico

Dr. Steven Squyers

Cornell University

Ithica, New York

Mr. Gordon Woodcock

Boeing Defense and Space Group

Huntsville, Alabama

Dr. David Black

Director

Lunar and Planetary Institute

Houston, Texas

Dr. Michael Carr

U.S. Geological Survey

Menlo Park, California

Dr. Ron Greeley

Dept. of Geology

Arizona State University

Tempe, Arizona

Dr. Noel Hinners

Lockheed Martin

Denver, Colorado

Dr. Joseph Kerwin

Skylab Astronaut

Lockheed Martin

Houston, Texas

Mr. Gentry Lee

Frisco, Texas

Dr. Roger Malina

Center for EUV Astrophysics

University of California

Berkeley, California

Dr. Christopher McKay

NASA Ames Research Center

Moffett Field, California
2-5

Table 2-2 Mars Study Team

Dr. Geoff Briggs

NASA Ames Research Center

Moffett Field, California

Ms. Jeri Brown

NASA Johnson Space Center

Houston, Texas

Ms. Nancy Ann Budden

NASA Johnson Space Center

Houston, Texas

Ms. Beth Caplan

NASA Johnson Space Center

Houston, Texas

Mr. John Connolly

NASA Johnson Space Center

Houston, Texas

Dr. Michael Duke

NASA Johnson Space Center

Houston, Texas

Dr. Steve Hawley

NASA Johnson Space Center

Houston, Texas

Mr. William Huber

NASA Marshall Space Flight Center

Huntsville, Alabama

Mr. Kent Joosten

NASA Johnson Space Center

Houston, Texas

Mr. David Kaplan

NASA Johnson Space Center

Houston, Texas

Dr. Paul Keaton

Los Alamos National Laboratory

Los Alamos, New Mexico

Mr. Darrell Kendrick

NASA Johnson Space Center

Houston, Texas

Ms. Barbara Pearson

NASA Johnson Space Center

Houston, Texas

Mr. Barney Roberts

NASA Johnson Space Center

Houston, Texas

Mr. Ed Svrcek

NASA Johnson Space Center

Houston, Texas

Mr. David Weaver

NASA Johnson Space Center

Houston, Texas

•Human Evolution – Mars is the most

accessible planetary body beyond the

Earth-Moon system where sustained

human presence is believed to be

possible. The technical objectives of Mars

exploration should be to understand

what would be required to sustain a

permanent human presence beyond

Earth. However, it is not an objective of

the Reference Mission to settle Mars but

to establish the feasibility of, and the

technological basis for, human

settlement of that planet.
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•Comparative Planetology – The scientific

objectives of Mars exploration should be

to understand the planet and its history

to better understand Earth.

•International Cooperation – The political

environment at the end of the Cold War

may be conducive to a concerted

international effort that is appropriate,

and may be required, for a sustained

program.

•Technology Advancement – The human

exploration of Mars currently lies at the

ragged edge of achievability. Some of the

technology required to achieve this

mission is either available or on the

horizon. Other technologies will be

pulled into being by the needs of this

mission. The new technologies or the

new uses of existing technologies will

not only benefit humans exploring Mars

but will also enhance the lives of people

on Earth.

•Inspiration – The goals of Mars

exploration are bold, are grand, and

stretch the imagination. Such goals will

challenge the collective skill of the

populace mobilized to accomplish this

feat, will motivate our youth, will drive

technical education goals, and will excite

the people and nations of the world.

•Investment – In comparison with other

classes of societal expenditures, the cost

of a Mars exploration program is

modest.

The workshop attendees then translated

these elements into two specific mission

objectives. For the first human exploration of

Mars:

•A better understanding is needed of

Mars—the planet, its history, and its

current state. And to answer, as best as

possible, the scientific questions that

exist at the time of the exploration, a

better understanding of the evolution of

Mars’ climate and the search for past life

are pressing issues.

•It is important to demonstrate that Mars

is a suitable location for longer term

human exploration and settlement.

The following sections discuss the details

of the science and exploration rationale as

applied to the Reference Mission.

Implementation details are in Section 3.

2.3 Science Rationale

Mars is an intriguing planet in part for

what it can tell us about the origin and history

of planets and of life. Visible to the ancients

and distinctly reddish in the night sky, it has

always been an attractive subject for

imaginative science fiction. As the capability

for space exploration grew in the 1960s, it

became clear that, unlike Earth, Mars is not a

planet teeming with life and has a harsh

environment. The images of Mariner 4

showed a Moon-like terrain dominated by

large impact craters (Figure 2-1).
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Figure 2-1 Orbital image of Mars.
2-8

This terrain now is believed to represent

ancient crust, similar to the Moon’s, formed in

an initial period of planetary differentiation.

Mariner 9 showed for the first time that Mars

was not totally Moon-like, but actually

exhibits later volcanic and tectonic features.

Large volcanoes of relatively recent activity

(Figure 2-2) and large crustal rifts due to

tensional forces (Figure 2-3) demonstrate the

working of internal forces.

Figure 2-2 Olympus Mons, the largest volcano

in the solar system.
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Figure 2-3 Across the middle is Valles Marineris, a huge canyon

as long as the United States.
2-10

The absolute time scale is not accurately

calibrated; however, by analogy with the

Moon, the initial crustal formation may have

occurred between 4 billion and 4.5 billion

years ago, and the apparent freshness of the

large martian volcanoes suggests their

formation within the last billion years.

Many scientific questions exist regarding

Mars and its history and will continue to exist

long after the first human missions to the

planet have been achieved. Two key areas of

scientific interest are the evolution of martian

climate and the possible existence of past life.

Mars’ atmosphere now consists largely of

carbon dioxide with a typical surface pressure

of about 0.01 of Earth’s atmosphere

(comparable to Earth’s atmospheric pressure

at an altitude of approximately 30,000 meters

or 100,000 feet) and surface temperatures that

may reach 25°C (77°F) at the equator in

midsummer, but are generally much colder.

At these pressures and temperatures, water

cannot exist in liquid form on the surface.

However, Mariner 9 and the subsequent

Viking missions observed features which

indicate that liquid water has been present on

Mars in past epochs (Figure 2-4).

Evidence for the past existence of

running water and standing water has been

noted, and the interpretation is that the

atmosphere of Mars was thicker and

warmer—perhaps much like Earth’s early

atmosphere before the appearance of oxygen.

Three questions arise:

•What was the reason for the change of

atmospheric conditions on Mars?

•What are the implications of such

changes for environmental changes on

Earth?

•Were the conditions on early Mars

enough like those of early Earth to guide

a search for past life?

These questions are part of the Mars

scientific exploration addressed by the

Reference Mission, and these questions can be

answered only by understanding the

geological attributes of the planet: the types of

rocks present, the absolute and relative ages

of the rocks, the distribution of subsurface

water, the history of volcanic activity, the

distribution of life-forming elements and

compounds, and other geologic features.

These attributes all have to be understood in

the context of what we know about the Earth,

the Moon, and other bodies of our solar

system.

Addressing the question of whether life

ever arose on Mars can provide a

fundamental framework for an exploration

strategy because, in principle, the search for

past life includes investigating the geological

and atmospheric evolution of the planet. It is

generally understood that the search for

evidence of past life cannot be conducted

simply by a hit-and-miss landing-and-looking

strategy, but must be undertaken in a stepwise manner in which geological provenances

that might be suitable are characterized,

located, and studied (Exobiology Program

Office, 1995). The characteristics of suitable

exploration sites are highly correlated with

the search for past or present water on the
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Figure 2-4 Dense tributary networks indicative of past presence

of liquid water on Mars.
2-12

planet. Within the geological framework,

strategic questions related to the search for

evidence of life can be posed.

•What is the absolute time scale for

development of the major features on

Mars? This would include determining

the time of formation of the martian

crust, a range of formation ages for

volcanic plains, and the age of the

youngest volcanoes. With this

information as a guide, the age of

formation of water-formed channels

should be boundable, and the

organogenic element content of martian

materials as a function of time may be

obtainable. As is inferred from the SNC

meteorites which are believed to have

originated on Mars (Bogard, et al., 1983

and McSween, 1994), impacts on Mars

have preserved samples of the martian

atmosphere in shock-produced glasses.

Thus, it may be possible to characterize

the evolution of the atmosphere from

carefully selected samples of impact

glass.

•What is the evidence for the distribution

in space and time of water on the

surface? This would include water

combined in widely distributed igneous

or clay minerals, in localized deposits

such as hydrothermal vents, in

subsurface permafrost, in the polar caps,

and in the atmosphere. The distribution,

age, composition, and mode of

formation (minerals formed by reaction

with or deposition from heated or cool

aqueous fluids, as found in the SNC

meteorites) is of major interest. Can the

channels apparently formed by water

erosion be demonstrated to have

experienced running water? Is there

verifiable evidence for the existence of

ponds of water? What is the distribution

of subsurface permafrost, and can the

features interpreted as permafrost

collapse be verified?

•What are the distribution and

characteristics of carbon and nitrogen—

the organogenic elements? Where do

they exist in reduced form? In what

environments are they preserved in their

original state? Is there chemical, isotopic

(hydrogen, carbon, nitrogen isotopes), or

morphological evidence that will link

concentrations of organogenic elements

to the past existence of life?

•If organic remains can be found, how

extensive are they in space and time?

What are their characteristics, variety

and complexity? How are they similar or

different to biological materials on

Earth?

Answers to these questions may be

sought through orbital mapping (for example,

to determine the distribution of hydrothermal

mineral deposits), in situ studies (surface

mineralogy, distribution of volatile elements),

sample return (age of rock units, detailed

chemistry, mineralogy, and isotopic

composition), and human exploration with

sample return (similar but with more highly

intelligent sample collection). The scientific
2-13

community debates the precise order of

investigative means used to achieve this

strategy, but generally concludes that the

question of distribution of past life will be of

such a difficult nature that sample return will

be required and that humans will ultimately

choose to carry out the exploration in person.

Given the assumption that humans will

take on the bulk of this type of exploration,

the key questions become:

•What is the appropriate role and place in

the exploration strategy of robotic

sample return missions?

•Scientifically, where is the appropriate

transition from robotic missions,

conducted routinely, and human

exploration missions, which may be

singular, large, and not reproducible?

General guidelines are needed to answer

these questions. Sample return missions

should be favored when they can be used to

significantly reduce the number of

subsequent missions to address the geological

modeling of the planet. Sample return

missions are likely to be more expensive than

one-way missions, so to be cost effective, they

must reduce the need for a proportionally

larger number of subsequent missions or

garner otherwise unobtainable information if

their justification is purely scientific. From a

scientific perspective, the guidelines for

human exploration are similar. If a human

exploration mission promises to answer the

major strategic questions better than a larger

number of robotic explorers, or opens new

modes of exploration that cannot be achieved

robotically, then the human mission will be

cost effective on scientific grounds.

2.4 Exploration Rationale

Aside from purely scientific benefits, the

human exploration of Mars brings with it

many tangible and intangible near-term

benefits such as:

•New associations between groups or

disciplines which previously have not

interacted, but because of common

objectives in exploration find new

strengths and opportunities (for

example, new international cooperation).

•New technologies which may be used

for practical application on Earth or in

other space enterprises (dual-use

technologies).

•Education of a new generation of

engineers and scientists spurred by the

dream of Mars exploration.

In the long term, the biggest benefit of

the human exploration of Mars may well be

the philosophical and practical implications

of settling another planet.

2.4.1 Inhabiting Another Planet

The dream of human exploration of Mars

is intimately tied to the belief that new lands

create new opportunities and prosperity. In

human history, migrations of people have

been stimulated by overcrowding, exhaustion

of resources, the search for religious or
2-14

economic freedom, competitive advantage,

and other human concerns. Rarely have

humans entered new territory and then

completely abandoned it. A few people have

always been adventurous enough to adopt a

newly found territory as their home. Most of

the settlements have eventually become

economically self-sufficient and have

enlarged the genetic and economic diversity

of humanity. The technological revolution of

the twentieth century, with high speed

communication and transportation and

integrated economic activity, may have

reversed the trend toward human diversity;

however, settlement of the planets can once

again enlarge the sphere of human action and

life.

Outside the area of fundamental science,

the possibility that Mars might someday be a

home for humans is at the core of much of the

popular interest in Mars exploration. A

human settlement on Mars, which would

have to be self-sufficient to be sustainable,

would satisfy human urges to challenge the

limits of human capability, create the

potential for saving human civilization from

an ecological disaster on Earth (for example, a

giant asteroid impact or a nuclear incident),

and potentially lead to a new range of human

endeavors that are not attainable on Earth.

The settlement of Mars presents new

problems and challenges. The absence of a

natural environment that humans and most

terrestrial fauna and flora would find livable

and the current high cost of transportation are

the main barriers to human expansion there.

The fact that, once on Mars, humans cannot

easily return to the Earth (and then only at

specified times approximately 26 months

apart) makes it necessary to develop systems

with high reliability and robustness.

At the present level of human

technological capability, a self-sufficient

settlement on Mars stretches our technical

limits and is not economically justifiable, but

it is imaginable. If, however, transportation

costs were to be reduced by two orders of

magnitude, such settlements might become

economically feasible. What kind of strategy

should be followed to explore the concept of

humans permanently inhabiting Mars? Three

considerations are important.

•Demonstrating the potential for selfsufficiency. This would include

understanding the potential to obtain all

important materials to support human

habitation from the natural materials of

Mars. It is most important that humans

be able to capture energy for driving

processes and have access to natural

resources (such as water, oxygen,

agricultural raw materials, building

materials, and industrial materials) from

martian rocks and soil. Demonstrating

self-sufficiency requires that resources be

located and technology and experience

be developed to efficiently extract them

from the in situ materials. Much can be

done robotically to locate resources prior

to arrival of the first human crew.

Extraction technology depends on a

more detailed understanding of the
2-15

specific materials present on Mars and

requires the detailed mineralogical and

chemical analyses generally associated

with sample return missions. An

exception is the production of water,

methane, and oxygen from the martian

atmosphere, which is now known well

enough to design extraction technology

(Sullivan, et al., 1995). In addition to the

extraction and use of martian resources,

self-sufficiency undoubtedly requires

highly advanced life support systems in

which most of the waste product from

human activity is recovered and reused,

and food is grown on the planet.

•Demonstrating that human beings can

survive and flourish on Mars. This will

likely be first explored by long-duration

missions in Earth orbit and may be

continued in the 1/6-g environment of

the Moon (Synthesis Group, 1991). Two

types of needs—physical and

psychological—must be met for humans

to survive and flourish on Mars. Physical

needs will be met through advanced life

support systems, preventive medical

sciences (nutrition, exercise,

environmental control, etc.), and the

capability of medical support for people

on Mars. Psychological needs will be

met through the design of systems,

identification and selection of work for

crews, communications with Earth, and

a better understanding of human

interactions in small communities. Many

of these can be addressed through a

lunar outpost program or in the

International Space Station program to

be conducted in the late 1990s. Some of

these concerns can also be addressed on

the first human exploration missions to

Mars, in which greater risks may be

taken than are appropriate for later

settlement.

•Demonstrating that the risks to survival

faced in the daily life of settlers on Mars

are compatible with the benefits

perceived by the settlers. Risks to

survival can be quantified through the

Mars exploration program. However, the

benefits will be those perceived by

future generations and cannot be

addressed here.

2.4.2 International Cooperation

The space age gained its start in a period

of intense technical and social competition

between East and West, represented by the

Soviet Union and the United States.

Competition during the International

Geophysical Year resulted in the Soviet Union

being the first to launch a satellite into Earth

orbit, which served to challenge and remind

the United States that technological

supremacy was not solely the province of the

United States.

The start of the Apollo program was a

political decision based more on the

perception of the political and technological

rewards to be gained by attacking a truly

difficult objective in a constrained time

period. The space race began, the United

States won it, and a relatively few years later,
2-16

the Soviet Union collapsed. Fortunately, the

Russians did not view Apollo success as a

reason to terminate their space exploration

program, and they continued to develop

capabilities that are in many areas on a par

with United States capabilities. Also, during

the post-Apollo time frame, space capability

grew in Europe (with the formation of the

European Space Agency), Japan, Canada,

China, and other countries. With these

developments, the basis has been laid for a

truly international approach to Mars

exploration—an objective in which all

humanity can share.

The exploration of Mars will derive

significant nontechnical benefits from

structuring this undertaking as an

international enterprise. It is unnecessary for

any country to undertake human exploration

of Mars alone, particularly when others, who

may not now have the required magnitude of

capability or financial resources, do have the

technological know-how. An underlying

requirement for the Reference Mission is that

it be implemented by a multinational group

of nations and explorers. This would allow

for a continuation of the cooperative effort

that is being made to develop, launch, and

operate the International Space Station.

2.4.3 Technological Advancement

From the outset, the Reference Mission

was not envisioned to be a technology

development program. The Mars Study Team

made a deliberate effort to use either

technology concepts that are in use today or

basic concepts that are well understood.

Section 3 of this report will illustrate that

much of the technology needed for a Mars

mission is either currently available or within

the experience base of the spacefaring nations

of the Earth. No fundamental breakthroughs

are required to accomplish the mission.

However, an extended period of advanced

development will be required to prepare the

systems needed to travel to and from Mars or

to operate on the surface of Mars; specifically,

high efficiency propulsion systems, life

support systems, and an advanced degree of

automation to operate, and if necessary

repair, processing equipment. At a general

level, perhaps two of the most important

ways in which the Reference Mission will

help advance technology that will benefit

more than just this program is to provide the

programmatic “pull” to bring technologies to

a usable state and the “drive” to make

systems smaller, lighter, and more efficient for

a reasonable cost.

For any of the technology areas

mentioned above (as well as others not

mentioned), this program will require

systems using these technologies to meet

performance specifications and be delivered

on schedule, all at a pace perhaps not

otherwise required. This applies to any

development effort. But for the Reference

Mission, many technologies will need to be

ready at once, causing many of these systems

to advance in maturity much faster than

might have otherwise been possible. These

mature systems and related technologies will

then be available to the marketplace to be
2-17

used in applications limited only by the

imagination of entrepreneurs.

The matured systems and the

technologies behind them will be attractive

to entrepreneurs in part because of the effort

to make them smaller, lighter, and more

efficient. A kilogram of mass saved in any of

these systems saves many tens of kilograms

of mass at launch from Earth (depending on

the propulsion system used) simply because

less propellant is required to move the

systems from Earth to Mars. Smaller, lighter,

or more efficient each translate into a

competitive advantage in the marketplace

for those who use these technologies.

Among the specific areas of desirable

technology advancement is propulsion

systems. Even the earliest studies for sending

people to the Moon or Mars recognized that

propulsion system efficiency improvements

have tremendous leverage in reducing the

size of the complete transportation system

needed to move people and supplies.

Chemical propulsion systems are reaching

the theoretical limits of efficiency in the

rocket engines now being produced. Further

improvements in efficiency will require the

use of nuclear or electrical propulsion

concepts which have the potential of

improving propulsion efficiencies by a factor

of up to 10, with corresponding reductions in

the amount of propellant needed to move

payload from one place to another. Both of

these propulsion technologies have matured

to a relatively high state of readiness in the

past, but neither has reached the level

necessary to be used on the Reference

Mission. Once developed, these technologies

become available for use, perhaps on reusable

vehicles, for the ever-increasing traffic in LEO

up to geosynchronous altitude.

Another area of tremendous leverage for

a mission to other planets is the ability to use

resources already there rather than burdening

the transportation system by bringing them

from Earth. Focusing on understanding what

is required for eventual settlement on Mars

leads quickly to those technologies that allow

the crew to live off the land. Of the known

raw materials available on Mars, the

atmosphere can be found everywhere and can

be used as feedstock to produce propellants

and life support resources. Other raw

materials (such as water) will eventually be

found and used, but sufficient detail is not

currently known about their locations and

quantities. This is an objective for initial

exploration.

Much of the processing technology

needed to produce propellants from

atmospheric gases already exists and is in use

on Earth. However, integrating these

technologies into a production plant that can

operate unattended for a period of years,

including self-repair, is an area where

additional development effort will be

required. (Chemical processing plants on

Earth are making significant progress toward

autonomous operation even now.) In this

area, the Reference Mission will adapt the

existing technologies at the time of the

Reference Mission rather than pull those
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technologies up to the levels needed by the

program. Regardless of how this technology

is developed, the advantages in

manufacturing and materials processing will

be significant.

Life support systems is another specific

area where advancing the state of the art can

significantly reduce the overall size of the

systems launched from Earth. The same

technologies that produce propellants can

also produce water and breathable gases for

human crews. These resources can be used as

makeup for losses in a closed or partially

closed life support system, and can also serve

as an emergency cache should primary life

support weaken or fail. Life support for this

Reference Mission can take advantage of

developments already made for International

Space Station and submarine use.

Developments in support of the Reference

Mission are likely to return technologies that

are smaller, more efficient, and perhaps less

costly than those available at the time.

Important in all of these areas is a focus

on ensuring that the cost to manufacture and

operate these systems is affordable in the

current economic environment. The designto-cost concept is not currently well

understood in the aerospace industry, and

any advancements in this area will benefit

development programs well beyond those

connected with the Reference Mission.

Developing the tools needed to determine

costs that are as easy to use as the tools used

to predict system performance is one of the

key technology areas that will help make the

Reference Mission possible. Equal with this is

instilling an attitude of cost consciousness in

the engineering community that will design

and produce these systems. The importance

of cost as a design consideration and

providing the tools to accurately forecast cost

should be incorporated in the educational

system that trains these engineers.

2.4.4 Inspiration

It can be argued that one role of

government is to serve as a focusing agent for

those events in history that motivate and

unify groups of people to achieve a common

purpose. Reacting to conflicts quickly comes

to mind as an example. For the United States,

World War II and the Persian Gulf War are

examples of how a nation was unified in a

positive sense; the Viet Nam War is an

example of how the opposite occurred.

It can also be argued that a role of

government is to undertake technical and

engineering projects that can inspire and

challenge. The great dam building projects in

the American West during the 1930s is an

example of the government marshaling the

resources to harness vast river systems for

electrical power and irrigation to allow for

population growth. The Interstate Highway

System is another example that receives little

fanfare but has changed the way we live. The

government incentives to private entities that

led to the development of the vast

intercontinental rail system in the last century

is another example.
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Few government efforts can collectively

motivate, unify, challenge, and inspire. The

Apollo program was one such example that

focused a national need to compete with

another nation in a very visible and high

profile manner; the Reference Mission can

serve as another. In this instance, the

undertaking provides a focus for the human

need to struggle and compete to achieve a

worthy goal—not by competing against each

other but rather against the challenges

presented by a common goal.

2.4.5 Investment

Scientific investigation, human

expansion, technology advancement, and

inspiration are not attainable free of charge.

Resources must be devoted to such a project

for it to succeed; and at a certain level, this

can be viewed as denying those resources to

other worthy goals. The Reference Mission

costs are high by current space program

standards, and additional effort is needed to

reduce these costs. The total program and

annual costs of the Reference Mission range

from 1 percent to 2 percent of the current

Federal budget—still far below other Federal

programs. If this program expands to an

international undertaking, the costs incurred

by each partner would be reduced even more.

A debate must still occur to determine if

this project is a worthwhile investment of the

public’s resources. But the use of these

resources should be viewed as more than just

an effort to send a few people to Mars. This

project will be investing in a growing part of

the infrastructure that affects our everyday

life: the use of space for business, commerce,

and entertainment. Just as space projects do

now, the Reference Mission can serve as a

focal point for invigorating the scientific,

technical, and social elements of the

education system, but with a much longer

range vision.

2.5 Why Not Mars?

Several impediments may severely

hamper the implementation of a program for

the human exploration of Mars. Some

impediments are due simply to the fact that

they have not been evaluated in sufficient

detail to gauge their impact. Others are

simply beyond the control of this or any other

program and must be taken into account as

the program advances. The following

paragraphs discuss some of these

impediments as viewed by the Mars Study

Team and others considering programs of this

type (Mendell, 1991).

2.5.1 Human Performance

It is a known fact that the human body

undergoes certain changes when exposed to

extended periods of weightlessness—changes

that are most debilitating when the space

traveler must readapt to gravity. The most

serious known changes include

cardiovascular deconditioning, decreased

muscle tone, loss of calcium from bone mass,

and suppression of the immune system. A

variety of countermeasures for these

conditions have been suggested, but none
2-20

have been validated through testing for longterm, zero-g spaceflight. The Russians have

had some success with long periods of daily

exercise to maintain cardiovascular capacity

and muscle tone, but monotonous and timeconsuming exercise regimes affect the

efficiency and morale of the crew.

Artificial gravity is often put forward as a

possible solution. In this case, the entire

spacecraft, or at least that portion containing

the living quarters for the crew, would be

rotated so that the crew experiences a

constant downward acceleration that

simulates gravity. It is generally assumed that

the Coriolis effect (the dizziness caused by

spinning around in circles) will fall below the

threshold of human perception if the

spacecraft is rotated at a slow rate. It is not

known whether simulation of full terrestrial

gravity is required to counteract all of the

known deconditioning effects of

weightlessness, or whether the small residual

Coriolis effect will cause some disorientation

in crew members. No data from a space-based

facility exists, and the space life science

research community is split over the viability

of artificial gravity as a solution.

Deconditioning is a critical issue for Mars

missions because the crew will undergo high

transient accelerations during descent to the

martian surface. Depending on the

physiological condition of the crew, these

accelerations could be life threatening. Once

on the surface of Mars, the crew must recover

without external medical support and must

perform a series of demanding tasks. The

time required for recovery is particularly

important if the surface stay is short (as has

been proposed for “opposition-class”

missions).

No one knows whether exposure to a

gravity field lower than the Earth’s will

reverse the deconditioning induced by

weightless space travel. And if some level of

gravity does halt the deconditioning effects,

what level is too low? In other words, if a

crew arrives on Mars in good physical

condition, what will their condition be after

spending an extended period of time under

martian gravity? Artificial gravity cannot be

provided easily on the martian surface, and

Apollo missions to the Moon were too short

to produce observable differences between

the condition of the astronauts who went to

the surface and those who remained

weightless in orbit.

The human body’s reaction to Mars

surface conditions, other than gravity, is also

not yet known. The Viking missions to Mars

found a highly reactive agent in the martian

soil, an explanation for which has not yet

been agreed to by the scientific community.

Without understanding this agent’s chemical

behavior, its impact on human crews cannot

be determined. No matter how carefully the

Mars surface systems are designed and no

matter how carefully the crews handle native

materials, small amounts of the martian

atmosphere and soil will be introduced into

crew living compartments during the course

of the mission. It will be necessary to better

characterize the Mars environment and assess
2-21

its impact on the crew. Assuring the health

and safety of the crew will be of obvious

importance.

Psychiatrists and psychologists agree that

piloted missions to Mars may well give rise to

behavioral aberrations among the crew as

have been seen on Earth in conditions of

stress and isolation over long periods of time.

The probability of occurrence and the level of

any such anomalous behavior will depend

not only on the crew members individually

but also on the group dynamics among the

crew and between the crew and mission

support personnel on Earth. In general, the

probability of behavior extreme enough to

threaten the mission will decrease with an

increased crew size. However, the expense of

sending large payloads to Mars to support a

large crew will limit the number of people in

any one crew. At the present time, little effort

has been spent developing techniques for

crew selection that will adequately guarantee

psychological stability on a voyage to Mars

and back. Russian experience suggests that a

crew should train together for many years

prior to an extended flight.

2.5.2 System Reliability and Lifetime

The spacecraft and surface elements will

likely be the most complex systems

constructed up to that point in time, and the

lives of the crew will depend on the reliability

of those systems for at least 3 years. By

comparison, a Mars mission will be of a

duration at least two orders of magnitude

greater than a Shuttle mission, and there will

be no opportunity for resupply. Either the

systems must work without failure or the

crew must have adequate time and capability

to repair those elements which fail.

Particularly important to the success of

piloted Mars missions will be testing of

integrated flight systems under conditions

similar to the actual mission for periods of

time similar to, and preferably much greater

than, the actual mission. Integrated flight

testing is truly critical if the flight system is

the first of its kind. Unfortunately, if history is

a guide, budget pressures will cause program

management to search for substitutions for

full-up flight testing. (For full-up flight

testing, hardware identical to that used in

flight is operated for periods of time equal to

or greater than the actual mission which

allows weaknesses or failures to be identified

and corrected. This is the most expensive way

to test, in terms of time and money.) After all,

most of the expense of a mission to Mars is in

launch and operations, two categories of

expense for a flight test whose magnitude

would be similar to that of an actual mission.

And what possible motivation would there be

for a crew to spend 2 or 3 years in orbit

pretending to go to Mars?

Somewhere in a large, complex program,

a manager will take a shortcut under pressure

from budget or schedule reasons, and the

consequences will not always be obvious to

program management. As a result, the

reliability of the product will be

overestimated. And management always

expresses a very human tendency to believe
2-22

good news. (This can be illustrated by the

change in the official estimates of the

reliability of the Shuttle before and after the

Challenger tragedy.) In short, significant risk

is introduced when relying on a product that

has not been tested in its working

environment, whether it is a new car, a

complex piece of software, or a spacecraft.

2.5.3 Political Viability and Social

Concerns

The human exploration of Mars is likely

to be undertaken for many of the reasons

already cited as well as others not presented

here. To a large degree, the responsibility for

taking action based on these reasons is in the

realm of political decision makers as opposed

to commercial concerns or other spheres of

influence. Thus, support for this type of

program must be sustained in the political

environment for a decade or more in the face

of competition for the resources needed to

carry it out.

Perhaps the closest analogy to a possible

international Mars exploration program is the

International Space Station, which has been

an approved international flight program for

over 10 years. During those 10 years, the

configuration of the Station has changed

several times and the number of and level of

commitment from partners has changed

significantly. Also during this time, Russia,

initially a significant competitor, has turned

into one of the larger partners in the

endeavor. And all of this has taken place prior

to launching the first element of the Station.

Shortening development time can be

beneficial if the project remains focused on its

requirements and can avoid changes imposed

by external forces.

If an institution wishes to be supported

with public funds for a long-duration project,

then the institution must be sophisticated

enough to plan visible milestones, which are

comprehensible to the public, at intervals

appropriate to the funding review process.

Historically, NASA has been reasonably

successful at maintaining funding of decadelong programs in the face of an annual budget

review. The vast majority of the programs are

understood by all to have a finite duration.

After a satellite has been launched and

operated for a given period of time, it either

fails or is shut off. Neither NASA nor the U.S.

Congress are yet comfortable with openended programs such as the Shuttle or

International Space Station or human

settlement of the solar system.

The decades-long time frame for human

exploration of Mars cannot be supported until

the role of the space program is well

integrated into the national space agenda and

the exploration of space is no longer

considered a subsidy of the aerospace

industry. To accomplish this, the space

program must show concern for national and

international needs (visible contributions to

technology, science, environmental studies,

education, inspiration of youth, etc.) while

maintaining a thoughtful and challenging

agenda of human exploration of space in

which the public can feel a partnership.
2-23

Finally there is the political concern of

back-contamination of Earth. This is as much

a social issue as a technical one. Some

segments of the population will object to any

Mars mission on these grounds. The two

tenets of a successful defense against such

opposition are to ensure that prudent steps

are taken at all phases of the project to

minimize risks and to demonstrate that the

value of the mission is high enough to merit

the residual minuscule risk.

2.6 Summary

This section has woven together several

key elements of a rationale for undertaking

the Reference Mission: human evolution,

comparative planetology, international

cooperation, technology advancement,

inspiration, and investment. Several

challenging aspects must be resolved before

the first human crews can be sent to Mars. But

the Reference Mission has a longer range

view and purpose that makes these

challenges worth the effort to overcome. If, at

some future time, a self-sufficient settlement

is established on Mars, with the capability of

internal growth without massive imports

from Earth, the benefit will be to the eventual

descendants of the first settlers, who will have

totally different lives and perspectives

because of the initial investment made by

their ancestors.

2.7 References

Bogard, D. and P. Johnson, “Martian

Gases in an Antarctic Meteorite,” Science,

Vol. 221, pp. 651-654, 1983.

Duke, M. and N. Budden, “Results,

Proceedings and Analysis of the Mars

Exploration Workshop,” JSC-26001,

NASA, Johnson Space Center, Houston,

Texas, August 1992.

Exobiology Program Office, “An

Exobiological Strategy for Mars

Exploration,” NASA SP-530, NASA

Headquarters, Washington, DC, April

1995.

McSween, H., “What We Have Learned

About Mars From SNC Meteorites,”

Meteoritics, Vol. 29, pp. 757-779, 1994.

Mendell, W., “Lunar Base as a Precursor

to Mars Exploration and Settlement,” 42nd

Congress of the International Astronautical

Federation, IAF-91-704, Montreal, Canada,

October 5-11, 1991.

Sullivan, T., D. Linne, L. Bryant, and K.

Kennedy, “In Situ-Produced Methane and

Methane/Carbon Monoxide Mixtures for

Return Propulsion from Mars,” Journal of

Propulsion and Power, Vol. 11, No. 5, pp.

1056-1062, 1995.

Synthesis Group, “America at the

Threshold: Report of the Synthesis Group

on America’s Space Exploration

Initiative,” U.S. Government Printing

Office, Washington, DC, May, 1991.

3-1

3. Mission and System

Overview
3-2
3-3

3.1 Introduction

Previous studies of human exploration of

Mars have tended to focus on spacecraft and

flight, rather than on what the crew would do

on the surface. The Reference Mission takes

the point of view that surface exploration is

the key to the mission, both for science and

for evaluation of the potential for settlement.

As a consequence, the Reference Mission

architecture allows for a robust surface

capability with significant performance

margins: crews will explore in the vicinity of

the outpost out to a few hundred kilometers,

will be able to study materials in situ and in a

surface laboratory, and will iterate their

findings with their exploration plan. In

addition, the development and demonstration

of the key technologies required to test

settlement issues will provide a substantial

workload. To make surface exploration

effective, the supporting systems (such as

EMU, life support, vehicles, robotics) must be

highly reliable, highly autonomous, and

highly responsive to the needs of the crew.

Some needs may not be anticipated during

crew preparation and training, which will

significantly challenge the management and

operations systems.

An infinite number of designs are

possible for a mission of this type. The

approach taken here is based on two general

principles.

•A hierarchy of requirements (starting

from mission objectives) is followed,

which, as they gain greater depth and

definition, merge with the proposed

implementation through a set of system

specifications (note that the Reference

Mission has followed these requirements

down to the system level only).

•A reasonable number of alternatives will

be considered, through trade studies at

each level of definition allowing

comparisons and choices.

3.1.1 Mission Objectives

Section 1 of this report discussed a series

of workshops conducted by NASA to define a

set of objectives and supporting rationale for

a Mars exploration program. The workshop

attendees (see Table 2-1) identified and

recommended for adoption three objectives

for analysis of a Mars exploration program

and the first piloted missions in that program.
3-4

They are to conduct:

•Human missions to Mars and verify that

people can ultimately inhabit Mars.

•Applied scientific research for using

martian resources to augment lifesustaining systems.

•Basic scientific research to gain new

knowledge about the solar system’s

origin and history.

A Mars Study Team composed of NASA

personnel representing most NASA field

centers (see Table 2-2) used inputs from the

adopted objectives to construct the Reference

Mission. In addition, the Study Team

recognized that past mission studies had

characterized piloted Mars missions as

inherently difficult and exorbitantly

expensive. Therefore, the Mars Study Team

added three objectives. These were to:

•Challenge the notion that human

exploration of Mars is a 30-year program

that will cost hundreds of billions of

dollars.

•Challenge the traditional technical

obstacles associated with sending

humans to Mars.

•Identify relevant technology

development and investment

opportunities.

3.1.2 Surface Mission Implementation

Requirements

To satisfy the objectives for the Reference

Mission, the Mars Study Team developed a

series of capabilities and demonstrations that

should be accomplished during surface

mission activities. Table 3.1 defines the

activities and capabilities that must exist to

meet the first three program objectives to the

next level of detail. The three objectives added

by the Study Team are useful in selecting

among feasible mission implementation

options that could be put forth to satisfy the

capabilities and demonstrations listed in the

table.

3.1.2.1 Conduct Human Missions to Mars

From the point of view of the surface

mission, conducting human missions implies

that the capability for humans to live and

work effectively on the surface of Mars must

be demonstrated. This includes several subobjectives to:

•Define a set of tasks of value for humans

to perform on Mars and provide the

tools to carry out the tasks.

•Support the humans with highly reliable

systems.

•Provide a risk environment that will

maximize the probability of

accomplishing mission objectives.

•Provide both the capability and the

rationale to continue the surface

exploration beyond the first mission.
3-5

These then require a set of functional

capabilities on the surface, including habitats,

surface mobility systems, and supporting

systems (such as power and communications

systems).

3.1.2.2 Conduct Applied Scientific Research

to Use Mars Resources to Augment LifeSustaining Systems

This objective will require that an

assessment be made of the location and

availability of specific resources (such as

water) that are useful for human habitation or

transportation. It will also require that

effective system designs be developed and

demonstrated to extract and use indigenous

resources. Opportunities exist to use

indigenous resources as demonstrations in

the life support subsystem, in energy systems

as fuel or energy storage, and as propellant

for spacecraft. These may eventually develop

into essential systems for the preservation of

the outpost. In addition, the following

habitation activities and demonstrations

satisfy the first and second objectives.

•Demonstrate that martian habitability

has no fundamental limitations due to

uniquely martian characteristics such as

Table 3-1 Capabilities and Demonstrations for Surface Mission Activities

Conduct Human Missions to Mars

a. Land people on Mars and return them safely to Earth.

b. Effectively perform useful work on the surface of Mars.

c. Support people on Mars for 2 years or more without resupply.

d. Support people away from Earth for periods of time consistent with Mars mission durationss

(2 to 3 years)

e. Manage space operations capabilities including communications, data management, and

operations planning to accommodate both routine and contingency mission operational

situations; and understand abort modes from surface or space contingencies.

f. Identify the characteristics of space transportation and surface operations systems consistent

with sustaining a long-term program at affordable cost.

Conduct Applied Science Research to Use Mars Resources to Augment Life-Sustaining Systems

a. Catalog the global distribution of life support, propellant, and construction materials

(hydrogen, oxygen, nitrogen, phosphorous, potassium, magnesium, iron, etc.) on Mars.

b. Develop effective system designs and processes for using in situ materials to replace products

that otherwise would have to be provided from Earth.

Conduct Basic Science Research to Gain New Knowledge About the Solar System’s Origin and

History

a. Using robotic and human investigations, gain significant insights into the history of the

atmosphere, the planet’s geological evolution, and the possible evolution of life.

b. Identify suitable venues at Mars, in the martian system, and during Earth-Mars transits for

other science measurements.
3-6

low gravity, absence of a magnetic field,

soil toxicity, or the radiation

environment.

•Demonstrate that self-sufficiency can be

achieved on the local scale of a Mars

base. This includes providing a

reasonable quality of life and reasonably

low risk for the crews, and should

include operating a bioregenerative life

support system capable of producing

food and recycling air and water.

•Determine the potential for expansion of

base capabilities using indigenous

resources. This would include the

successful extraction of life support

consumables from the martian

environment and storage for later use.

•Investigate the biological adaptation of

representative plant, animal, and

microbial species to the martian

environment over multiple generations.

These activities and demonstrations are

aimed at establishing the feasibility and

approach required to move beyond the

exploratory phase toward the development of

long-term activities on the planet. They

influence the selection of elements that are

included in the surface systems (habitats,

mobility, life support, power, and

communications systems).

To the support facilities identified in the

previous section must be added exploration

systems (orbital or surface), resource

extraction and handling systems, and

additional systems for producing food and

recycling air and water.

3.1.2.3 Conduct Basic Scientific Research to

Gain New Knowledge About the Solar

System’s Origin and History

This will require that a variety of

scientific explorations and laboratory

assessments be carried out on the surface of

Mars by both humans and robots. The

scientific research will not be conducted

completely at any one site, which will create a

need for crew member mobility and

transportation systems to support

exploration, the specialized tools required

outside the outpost to collect and document

materials, and the facilities inside the outpost

to perform analyses.

The principal science activities and

demonstrations for Mars exploration include

answering the following questions.

•Has Mars been a home for life?

This set of objectives will combine field

and laboratory investigations in geology,

paleontology, biology, and chemistry. The

underlying assumption is that this question

will not have been answered by previous

robotic Mars exploration programs, and the

best way to get an answer is through

judicious use of humans on Mars as field

geologists and laboratory analysts. Recent

evidence indicating past life on Mars found in

a martian meteorite has placed increased

emphasis on this question (McKay, et al.,

1996).
3-7

•What are the origin and evolution of

Mars, particularly its atmosphere, and

what does it tell us about Earth?

This set of objectives involves geology

and geophysics, atmospheric science,

meteorology and climatology, and chemistry.

Iterative sampling of geological units will be

required as well as monitoring of a global

network of meteorological stations. (A global

network will most likely be established by

robotic elements of the program.)

•What resources are available on Mars?

The resource discovery and verification

of accessibility will require investigations in

geology, atmospheric science, and chemistry.

A general strategy for accomplishing this will

begin with a global mapping (from orbit) of

selected elemental and mineralogical

abundances. This activity is best suited for a

robotic spacecraft sent prior to the flight of

the first human crew. Robotic missions are

also likely for verifying the abundances and

making an initial assessment of accessibility

of the resources. The data gathered will also

be important for selecting likely sites for the

surface outpost to be used by human crews.

3.1.2.4 Surface Operations Philosophy

In addition to the facilities and

equipment mentioned above, the crew must

have a general operating philosophy for

conducting activities, demonstrations, and

experiments on the surface. The targeted

investigations to be carried out from the Mars

outpost depend on humans and automated

rover sample collectors having accessibility to

interesting or significant sites at increasing

distances from the outpost. Figure 3-1 shows

a photomosaic of the Candor region of the

Valles Marineris in which the location of an

outpost could address fundamental questions

of Mars’ origin and history. This region is

located roughly between 70 degrees and 75

degrees west longitude and between 2.5

degrees and 7.5 degrees south latitude. A

general geological map of the region of the

outpost site should be prepared using data

gathered by robotic missions prior to selecting

and occupying the initial site.

Once the outpost is established,

exploration activity will consist of surface

observations made by robotic vehicles and

human explorers, collection of samples, and

examination of samples in the outpost

laboratory. Crews will be given broadly stated

scientific questions or exploration objectives

to be addressed in relatively large regions

near the outpost site. Operations will not be

as highly choreographed over the 600-day

surface stay-time as they are for current

spaceflight missions. The crews and Earthbased supporting investigators will plan

campaigns lasting days or weeks, eventually

extending to months, but always with the

assumption that replanning may be necessary

based on discoveries made. It is likely that a

strategy of general reconnaissance followed

by detailed investigations will be followed.

The outpost laboratory will be outfitted to

provide mineralogical and chemical analyses

and, depending on technical development, it
3-8

Figure 3-1 A regional map illustrating potential locations for a Mars outpost.

Desired

Landing

Area
3-9

may be possible to perform simple kinds of

geochronologic analysis. The purpose of these

studies will be to support the field

investigations, answer “sharper” questions,

and allow human explorers to narrow their

focus to the sites of optimum sample

collection. Ultimately, selected samples will

be returned to Earth for more detailed

analysis.

Science equipment, experiments, and

tools must be proven in order for the

exploration and science objectives of the

missions to be accomplished, and their

selection is at the core of the argument that

humans can effectively perform scientific

research on the planet. Failure to equip

humans properly will be a failure to take

advantage of their unique potential. Overequipping them may be counterproductive as

well, at least from the cost aspect of

transporting unneeded equipment to Mars.

The exploration and science objectives to be

performed on the surface can be broken into

four categories: field work, telerobotic

exploration, laboratory and intravehicular

activity experiments, and preparation of

materials for return to Earth.

•Observations related to exobiology,

geology, and martian atmosphere studies

will be made by humans in the field.

Samples and data will be collected and

returned to the outpost laboratory for

analysis. The information from the

analyses will be used to plan or replan

future traverses as scientific and

exploration questions are sharpened.

Information will be transmitted to

scientists on Earth so they can

participate in the replanning activity.

Crews will also emplace geophysical and

meteorological instruments to measure

internal properties and atmospheric

dynamics. Drilling short depths into the

surface should be standard capability. At

some point it will be appropriate to drill

deeply into the surface to address

stratigraphic issues and to locate and tap

into water reservoirs.

•The Mars crews will also have the

capability to operate telerobotic systems

conducting even broader exploratory

tasks using the ability to communicate

with and direct these systems in near

real-time. Some teleoperated rovers

(TROVs) may be emplaced before crews

arrive on Mars and may collect samples

for assembly at the Mars outpost. The

TROVs may be designed to provide

global access and may be able to return

samples to the outpost from hundreds of

kilometers distance from the site. These

robotic systems may also emplace

geophysical monitoring equipment such

as seismometers and meteorological

stations.

•Scientific experiments will also be

conducted that are uniquely suited to

being performed on the surface of Mars.

These will typically be experiments that

make use of the natural martian

environment (including reduced gravity)

or involve interaction with martian
3-10

surface materials. Studies will be

performed on biological systems, best

performed in conjunction with an

experimental bioregenerative life

support system. The deployment of a

bioregenerative life support capability

will be an early activity after crew

landing. Although this system is not

required to maintain the health and

vitality of the crew, it will improve the

robustness of the life support system and

is important to the early objectives of the

outpost. Field samples will be studied in

laboratory facilities shared between the

geosciences, biosciences, and facilities

support systems. For example, analytical

systems used to monitor organisms in

the biological life support system may

also be used to monitor the environment

of the habitat in general. Some analytical

capabilities (such as gas

chromatographs) find use in both

geological and biological analysis. All

samples and data (geological, biological,

medical, etc.) will be documented and

cataloged for later research.

•One crew task will be to select and

package samples for return to Earth for

more detailed study. This will require the

creation of a minicuratorial facility and

procedures to ensure that

uncontaminated samples are returned to

Earth.

As experience grows, the range of human

exploration will grow from the local to the

regional. Regional expeditions, lasting several

weeks and using mobile facilities, may be

conducted at intervals of a few months.

Between these explorations, analysis in the

laboratory will continue. The crew will also

spend a significant portion of time

maintaining and ensuring the continuing

functionality of life support and materials

processing systems and performing

maintenance on robotic vehicles and EVA

suits (systems should be designed to help

keep these activities to a minimum).

Crew activities related to living on

another planet should be viewed not only as

experiments but also as activities necessary to

carry out the mission. With minor

modifications in hardware and software,

ordinary experiences can be used to provide

objective databases for understanding the

requirements for human settlement.

To optimize the performance of the

mission, it will be necessary to pick a landing

site primarily on the basis of satisfying

mission objectives. However, the landing site

must be consistent with landing and surface

operational safety. Detailed maps of candidate

landing sites should be available to define the

safety and operational hazards of the site, as

well as to confirm access (by humans or

robotic vehicles) to scientifically interesting

locations. Depending on the results of prior

missions, it would be desirable to site the

outpost where water can be readily extracted

from minerals or from subsurface deposits.
3-11

3.1.3 Ground Rules and Assumptions

Translating these goals and objectives

into specific missions and systems required

adopting a number of guidelines and

assumptions.

•Balance technical, programmatic,

mission, and safety risks. Mars

exploration will not be without risks.

However, the risk mitigation philosophy

as well as the acceptability of the mission

concept to the public, its elected leaders,

and the crews will be critically important

in the technical and fiscal feasibility of

these missions. Mars is not “3 days

away,” and overcoming the temptation

to look back to Earth to resolve each

contingency situation may be the most

challenging obstacle to overcome in

embarking upon the human exploration

of Mars.

•Provide an operationally simple mission

approach emphasizing the judicious use

of common systems. For example, an

integrated mission in which a single

spacecraft with all elements needed to

carry out the complete mission is

launched from Earth and lands on Mars

to conduct the long exploration program

is not feasible due to launch mass

considerations alone. It is necessary to

determine the simplest and most reliable

set of operations in space or on the

surface of Mars to bring all of the

necessary resources to the surface where

they are to be used. A strategy

emphasizing multiple uses for single

systems can potentially reduce the total

program costs and enhance crew safety

and system maintainability.

•Provide a flexible implementation

strategy. Mars missions are complex, so

multiple pathways to the desired

objectives have considerable value in

ensuring mission success.

•Limit the length of time the crew is

continuously exposed to the

interplanetary space environment. Doing

this will reduce the physiological and

psychological effects on the crew and

enhance their safety and productivity. In

addition, the associated life science

concerns are partially mitigated. It is

assumed that crews will arrive at Mars

in good health, that full physical

capability can be achieved within a few

days, and that crew health and

performance can be maintained

throughout the expedition.

•Define a robust planetary surface

exploration capacity capable of safely

and productively supporting crews on

the surface of Mars for 500 to 600 days

each mission. The provision of a robust

surface capability is a defining

characteristic of the Reference Mission

philosophy. This is in contrast to

previous mission studies that have

adopted short stay-times for the first or

first few human exploration missions

and focused attention principally on

space transportation.
3-12

•Be able to live off the land. The

capability to manufacture resources at

Mars, particularly propellants, has long

been known to have significant leverage

in terms of the amount of material that

must be launched from Earth. It also

provides a risk reduction mechanism for

the crew when viewed as a cache of life

support consumables to back up those

brought from Earth. Additional system

development effort will be required, but

the advantages outweigh the cost and

development risk, particularly if the

infrastructure supports more than one

human exploration expedition.

•Rely on reasonable advances in

automation to perform a significant

amount of the routine activities

throughout the mission. This includes a

capability to land, set up, operate, and

maintain many of the Mars surface

systems needed by the crew prior to

their arrival.

•Ensure that management techniques are

available and can be designed into a

program implementation that can

substantially reduce costs.

•Use the Earth-Mars launch opportunities

occurring from 2007 through 2014. A

2009 launch represents the most difficult

opportunity in the 15-year Earth-Mars

trajectory cycle. By designing the space

transportation systems for this

opportunity, particularly those systems

associated with human flights, they can

be flown in any opportunity with faster

transit times for the crew or increased

payload delivery capacity for cargo. This

enhances program flexibility.

•Examine at least three human missions

to Mars. The initial investment to send a

human crew to Mars is sufficient to

warrant more than one or two missions.

Each mission will return to the site of the

initial mission, with missions two and

three launching in the 2012 and 2014

launch opportunities, respectively. This

approach permits an evolutionary

establishment of capabilities on the Mars

surface and is consistent with the stated

goals for human exploration of Mars.

Although it is arguable that scientific

data could be enhanced by landing each

human mission at a different surface site,

the goal of understanding how humans

could inhabit Mars seems more logically

directed toward a single outpost

approach. This leaves global exploration

to robotic explorers or perhaps later

human missions.

3.2 Risks and Risk Mitigation

Strategy

Several related but also separable aspects

of risk are associated with a Mars mission and

must be considered in designing the

Reference Mission. Reference Mission

activities will inevitably be hazardous

because they are conducted far from home in

extreme environments. However, the hazards

can be reduced by proper design and

operational protocols. Before a Mars
3-13

exploration program is approved, it will be

necessary to decide whether the elements of

risk to the enterprise can be reduced to a level

consistent with the investment in resources

and human lives.

3.2.1 Risks to Human Life

Crews undertaking the human

exploration of Mars will encounter the active

space environment, the in-space environment,

and the planetary surface environment.

The active space environment includes

launch from Earth, maneuvers in near-Earth

space, launch on a trajectory to Mars, entry

and landing on Mars, launch from Mars, Mars

orbital maneuvers, launch on a trajectory to

Earth, reentry of Earth’s atmosphere, and

landing on Earth. Because these are energetic

events, the risk is relatively high. In 100

launches of United States manned spacecraft

and a similar number of Russian spacecraft,

the only fatal accidents have occurred in

launch or landing. Once in space, the

environment has been relatively benign.

(Apollo 13 was an exception. En route to the

moon, it experienced an equipment failure

which jeopardized the crew. Because of the

characteristics of the Earth-Moon trajectories

and the spacecraft design, it was possible to

recover the crew. This type of risk can be

addressed in part by the Mars exploration

architecture, and can be different for humans

and cargo.)

The quiescent in-space environment is

relatively benign from the point of view of

explosions and other spacecraft accidents.

However, there are important and potentially

deadly environmental hazards (such as

radiation and meteoroid damage) which must

be addressed. Two radiation hazards exist.

First and most dangerous is the probability of

a solar proton event (SPE) which is likely to

occur during any Mars mission. Solar proton

events can rise to the level where an unshielded person can acquire a life threatening

radiation dosage. However, shielding with

modest amounts of protective material can

alleviate this problem. The task becomes one

of monitoring for events and taking shelter at

the appropriate time. Galactic cosmic rays, the

other radiation hazard, occur in small

numbers, are very energetic, and can cause

deleterious effects over a long period of time.

For astronauts in LEO, exposure to cosmic

radiation has been limited to that level which

could induce an additional 3 percent lifetime

risk of cancer (curable or incurable). Because

of a policy that radiation hazards should be

kept as low as reasonably achievable, spacecraft and space operations must be designed

to minimize exposure to cosmic rays. The

health risk today from radiation exposure on

a trip to Mars cannot be calculated with an

accuracy greater than perhaps a factor of 10.

The biomedical program at NASA has given

high priority to acquiring the necessary health

data on HZE radiation, including the design

shielding materials, radiation protectant

materials, and SPE monitoring and warning

systems for the Mars crew. (For additional

discussion and explanation of this topic, see

NASA, 1992; Townsend, et al., 1990; and

Simonsen, et al., 1990.)
3-14

The planetary surface is the third

environment which provides risks to crews.

Because operational experience on Mars is

limited, this environment is the least

understood. As the objective of human

exploration of Mars will be to spend time on

the surface of Mars, extensive EVA will be

required as part of the mission. EVAs will

involve exiting and reentering pressurized

habitats and conducting a variety of activities

on the surface in space suits or other

enclosures (including vehicles). In this area,

accidents and equipment failures are the

biggest concerns. These risks must be

addressed by examining a combination of

detailed information about the surface

environment, designing and testing

hardware, and training the crew. To some

extent, EVA can be reduced or simplified by

using telerobotic aids operated by the crew

from their habitat. (The risks associated with

the habitat itself are probably similar to those

faced in free space, with somewhat more

benign radiation and thermal environments.)

Finally, the presence of dust on Mars will

present risks, or at least annoyances, to

surface operations. Robotic missions to Mars

prior to human expeditions should improve

understanding of the surface hazards crews

will encounter.

3.2.2 Risks to Mission Success

The risk of a Mars exploration mission is

measured by the degree to which the program

objectives can be accomplished. A successful

trip to and from Mars, without accomplishing

any surface exploration objectives, would be

only minimally successful. Mission risk is

related to the integrated capability of the crew

and their systems to conduct the mission. For

the crew or the systems to fail to perform puts

the mission at risk of failure. On the human

side, this requires attention to health, safety,

performance, and other attributes of a

productive crew. On the system side, this

requires that systems have low failure rates,

have robust backups for systems that may fail

or require repair, and be able to operate

successfully for the required period of the

mission. Strategies to minimize failure can be

designed at the architecture level or at the

system level.

3.2.3 Risks to Program Success

Program risk is a term that refers to the

programmatic viability of the exploration

program—that is, once the program has been

approved, what are the risks that it will not be

completed and the exploration not

undertaken? These are programmatic issues

that in many cases seem less tractable than

the technical risks. They can be influenced

when management of the enterprise fails to

meet milestones on schedule and cost, when

unforeseen technical difficulties arise, or

when political or economic conditions

change. They can be mitigated by sound

program management, good planning, and

advocacy or constituency building on the

political side.
3-15

3.2.4 Risk Mitigation Strategy

The riskiest part of the first exploration

missions to Mars may well be the risk of

accident on launch from Earth, and the

energetic events of launches and landings

during other phases of the mission are likely

to make up the remaining high risk parts of

the mission. Yet, the environment on the

surface of Mars will be new and untried, the

missions will be long, and the opportunities

to make up for error small. Therefore, a

conscious approach to minimizing risks on

the martian surface must be adopted. For a

starting point, it is assumed that this risk

must be smaller than the combined risks of all

of the energetic events. Design requirements

will have been developed with this in mind.

The strategy for reduction of risks on the

surface involves four levels of consideration.

At the top level, the mission architecture

provides for assurance that all systems will

operate before crews are launched from Earth.

The strategy must be flexible in allowing

subsequent robotic missions to replace any

systems shown not to be functional prior to

sending crew. This, in turn, places design

requirements on the hardware to allow

problems to be identified, isolated, fixed in

place if possible, and bypassed if necessary

through the addition of a parallel capability

sent on a subsequent flight.

The second level of risk reduction

involves providing redundancy through the

overlapping functional capabilities between

various systems, the ability to repair any lifecritical systems, and the provision of a

suitable suite of replacement systems as

backups to the prime systems. The following

priorities are recommended.

•Crew health and safety are top priority

for all mission elements and operations;

life-critical systems are those absolutely

required to ensure the crew’s survival.

This implies that life-critical systems will

have two backup levels of functional

redundancy; if the first two levels fail, the

crew will not be in jeopardy but will not

be able to complete all mission objectives.

At least the first level of backup is

automated. (This is a fail operational/fail

operational/fail-safe system.)

•Completing the defined mission to a

satisfactory and productive level

(mission-critical) is the second priority.

This implies that mission-critical

objectives will have one automated

backup level. (This is a fail operational/

fail-safe system.)

•Completing additional, possibly

unpredicted (mission-discretionary),

tasks which add to the total productivity

of the mission is third priority. The crew

will not be in jeopardy if the missiondiscretionary systems fail, and a backup

is not needed. (This is a fail-safe system.)

The systems contributing to this backup

strategy were assumed to be provided by

either real redundancy (multiple systems of

the same type) or functional redundancy

(systems of a different type which provide the

required function). Recoverability or
3-16

reparability by the crew will provide yet

additional safety margins.

The third level of risk reduction involves

the automation of systems including fault

detection, failure projection, and maintenance

activities, and the provision of data that

demonstrate current status and predict future

states. Such systems are not only conservative

of crew time, but also more effective and

precise, particularly on routine monitoring

and control tasks.

The fourth level of risk reduction is

related to crew training and proficiency. The

biggest concern in this area is that the crew

will be away from the traditional Earth-based

training environment for years at a time.

Those areas with direct human

involvement—EVA, life support systems,

high capacity power systems, propellant

production and storage, mobile vehicles, and

other complex facilities—all carry a high risk

for accident, particularly if training is not

recent or crew members become

overconfident. Crews will most likely be

required to participate in continuous task

training for safety awareness requirements.

3.3 Flight Crew

Humans are the most valuable mission

asset for Mars exploration and must not

become the weak link. The objective for

humans to spend up to 600 days on the

martian surface places unprecedented

requirements on the people and their

supporting systems. Once committed to the

mission on launch from LEO, the crew must

be prepared to complete the full mission

without further resupply from Earth.

Unlimited resources cannot be provided

within the constraints of budgets and mission

performance. Their resources will either be

with them or will have already been delivered

to or produced on Mars. So trade-offs must be

made between cost and comfort as well as

performance and risk. Crew self-sufficiency is

required because of the long duration of their

mission and the fact that their distance from

Earth impedes or makes impossible the

traditional level of communications and

support by controllers on Earth. The crews

will need their own skills and training and

specialized support systems to meet the new

challenges of the missions.

Crews should be selected who will agree

to conduct operational research willingly and

openly. Crew members should be selected

who can relate their experiences back to Earth

in an articulate and interesting manner, and

they should be given enough free time to

appreciate the experience and the opportunity

to be the first explorers of another planet.

Because the objectives of the missions are

to learn about Mars and its capability to

support humans in the future, there will be a

minimum level of accomplishment below

which a viable program is not possible.

Survival of humans on the trip there and back

is not a sufficient program objective.

3.3.1 Crew Composition

The number of crew members to be taken

to Mars is an extremely important parameter
3-17

for system design, because the scale of the

habitats, space transportation system, and

other systems supporting the mission are

directly related to the number of crew

members. This, in turn, will have a direct

relationship to the cost of the first missions.

The size of the crew also is probably inversely

proportional to the amount of new

technology which must be developed to allow

all tasks to be performed. Because of

communication time delays between Earth

and Mars, some functions that have

previously been performed by people on

Earth will be carried out autonomously or by

crew members. Generally, there will be a high

degree of automation required for routine

operations on the Mars journey to allow crew

members to do specialized tasks.

For the Reference Mission study, it was

assumed that crew health and safety are of

first priority in successfully achieving mission

objectives and that the surface system design

requirements for operability, self-monitoring,

maintenance, and repair will be consistent

with the identified minimum number of crew

members. The crew size and composition was

determined in a top-down manner (objectives

➝ functions ➝ skills ➝ number of crew

members + system requirements) as the

systems have not been defined in a bottomsup manner based on an operational analysis

of the system.

The Mars Study Team workload analysis

assumed that the crew would spend available

time in either scientific endeavors or

habitation-related tasks. From that analysis,

lists of required skills were developed.

Expertise is required in three principal areas.

•Command, control, and vehicle and

facility operations functions. These

functions include command,

management, and routine and

contingency operations (piloting and

navigation, system operations,

housekeeping, maintenance, and repair

of systems). Maintenance must be

accomplished for facility systems,

human support systems (medical

facilities, exercise equipment, etc.), EVA

systems, and science equipment.

•Scientific exploration and analysis. This

area includes field and laboratory tasks

in geology, geochemistry, paleontology,

or other disciplines associated with

answering the principal scientific

questions.

•Habitability tasks. These tasks include

providing medical support; operating

the bioregenerative life support system

experiment; performing biological,

botanical, agronomy, and ecology

investigations; and conducting other

experiments directed at the long-term

viability of human settlements on Mars.

The types of crew skills needed are

shown in Table 3-2 (Clearwater, 1993). If each

skill is represented by one crew member, the

crew size would be too large. Personnel will

have to be trained or provided the tools to

perform tasks which are not their specialty.
3-18

Special skill requirements appear to be in the

areas of medicine, engineering, and

geoscience.

•Medical treatment. In a 3-year mission, it

is very likely that an accident or disease

will occur. At least one medically trained

person will be required as well as a

backup who is capable of conducting

procedures under the direction of

medical experts on Earth (through

telemedicine).

•Engineer or technician. A person skilled

in diagnosing, maintaining, and

repairing mechanical and electrical

equipment will be essential. A high

degree of system autonomy, selfdiagnosis, and self-repair is assumed for

electronic systems; however, the skill to

Table 3-2 Surface Mission Skills

Specialized Operations Focused

 and Services Objectives In-Common

Geology

Geochemistry

Paleontology

Geophysics including

 Meteorology and

 Atmospheric Science

Biology

Botany

Ecology

Agronomy

Social Science

Management/planning

Communications

Computer Sciences

Database Management

Food Preparation

• routine greenhouse

 operations

• plants to ingredients

• ingredients to food

Vehicle Control

Navigation

Teleoperated Rover Control

Journalism

Housekeeping

Mechanical Systems Operations,

 Maintenance and Repair

Tool-Making

Electrical Systems Operations,

 Maintenance and Repair

Electronics Systems Operations,

Maintenance and Repair

General Practice Medicine

Surgery Biomedicine

Psychology Psychology
3-19

identify and fix problems, in conjunction

with expert personnel on Earth, has been

repeatedly demonstrated to be essential

for space missions.

•Geologist-Biologist. A skilled field

observer-geologist-biologist is essential

to manage the bioregenerative life

support system experiment. All crew

members should be trained observers,

should be highly knowledgeable of the

mission science objectives, and should be

able to contribute to the mission science.

Other factors will also contribute to the

final determination of crew size: system

autonomy, simultaneous operations,

contingency situations, human factors, and

international participation.

•Electronic and mechanical equipment

must be highly autonomous, selfmaintained or crew-maintained, and

possibly self-repairing. The amount of

time taken to do routine operations must

be minimized through system design. In

principle, the operation of supporting

systems (such as power, life support, in

situ resource recovery) should be

transparent to the crew. The best

approach in this area is to define the

requirement for technological

development based on the mission

requirements for a given crew size.

•Simultaneous operations will be

required during the nominal mission. All

crew members will be fully occupied

during their assigned working hours,

and a minimum number of crew

members will be required by the

distribution of tasks. For example, EVAs

are likely to require at least two people

outside the habitat at any one time in

order to assist each other. A third person

is likely to be required inside to monitor

the EVA activities and assist if necessary.

If other tasks (repair, science,

bioregenerative life support system

operation) are required to be done

simultaneously, the number of crew

members may need to be increased.

•Specific contingency situations and

mission rules have not been established

for the Reference Mission because it is

too early in the design phase. However,

the choice of what the crew will be

allowed to do or not do can impact the

size of the crew. For example, during

exploration campaigns, mission rules

may require that some portion of the

crew be left in the main habitat while the

remainder of the crew is exploring in the

mobile unit. It will be necessary to have

a backup crew to operate a rescue

vehicle in case the mobile unit has a

problem. If the exploration crew requires

three people, the requirement to have

one driver for a backup unit and one left

at the outpost implies a crew of not less

than five.

•In terms of human factors

considerations, the psychological

adjustment is more favorable in larger

crews of six to eight than in smaller
3-20

crews of three to five. However, the

psychological environment may be met

by system and support provisions rather

than by the crew size itself.

•It is conceivable that each country that

makes a major contribution to an

international Mars exploration mission

will demand representation on the crew.

Currently, a Mars crew might be

patterned after the International Space

Station with representatives from the

United States, Russia, European Space

Agency, and Japan. However, in an

enterprise of this magnitude, Third

World representatives might also be

selected by the United Nations.

At a summary level, the five most

relevant technical fields required by the

exploration and habitation requirements

include mechanical engineer, electrical and

electronics engineer, geologist, life scientist,

and physician-psychologist. These fields

should be represented by a specialist, with at

least one other crew member cross-trained as

a backup. Crew members would also be

cross-trained for the responsibilities of a wide

variety of support tasks as well as tasks of

command and communications.

The result of the workload analysis

indicates that the surface mission can be

conducted with a minimum crew of five,

based on the technical skills required.

However, loss or incapacitation of one or

more crew members could jeopardize mission

success. Therefore, a larger crew may be

required to address the risk issues. Currently,

the Reference Mission is built on the

assumption of a crew of six.

3.3.2 Crew Systems Requirements

To survive, the crew will need adequate

shelter, including radiation protection;

breathable, controlled, uncontaminated

atmosphere (in habitats, suits, and

pressurized rovers); food and water; medical

services; psychological support; and waste

management. During the 4- to 6-month transit

to Mars, the chief problems will be

maintaining interpersonal relationships

needed for crew productivity and

maintaining physical and mental

conditioning in preparation for the surface

mission. On the Mars surface, the focus will

turn to productivity in a new and harsh

environment. The transit environment is

likely to be a training and conditioning

environment, the surface environment is

where the mission-critical tasks will be done.

For long-duration missions with

inevitably high stress levels, the trade-off

between cost and crew comfort must be

weighed with special care. High quality

habitats and environmental design features

are critical to assuaging stress and increasing

crew performance—conditions that will

greatly increase the likelihood of mission

success. Providing little more than the

capability to survive invites mission failure.

Not all amenities need be provided on

the first mission. The program should be
3-21

viewed as a sequence of steps which, over

time, will increase the amount of habitable

space on the surface, increase the amount of

time available to the crew to devote to

mission objectives and personal activities,

increase the amount of crew autonomy,

improve the quality of food, increase access to

privacy, and increase the quality and quantity

of communications with Earth. In addition,

experience in Mars surface operations may

reduce some of the stresses associated with

the unfamiliarity of the environment.

The quality of life can be enhanced by

access to and use of indigenous resources. In

the near term, use of indigenous resources

reduces some of the mission risks (creation of

caches, use of local resources for radiation

shielding, etc.). In the long term, use of local

resources may allow more rapid expansion of

usable space. Achieving the capability to

produce water and oxygen from local

resources may have physical and

psychological benefits over continued

recycling (for example, reducing limitations

on water utilization for hygiene purposes).

The ability to grow food on site also has an

enhancing psychological effect. The

psychological impacts of these developments

is difficult to quantify, however real the effects

may be.

Finally, crew support by intelligent robots

and automated systems appears to be a good

investment from the point of view of total

mission productivity. The workload analysis

indicates that the total amount of time spent

in the field (on foot or in a rover) by a crew

member will be from 10 percent to 20 percent

of the amount of their time on Mars.

Automated or teleoperated rovers could

extend the effective field time by crew

members.

3.4 Mission Operations

Central to the success of the Reference

Mission is the accomplishment of all activities

associated with mission objectives. To this

end, crew operations are an essential part of

ensuring program success and must be

factored into all aspects of program planning.

All crew activities throughout each mission,

from prelaunch through postlanding,

constitute crew operations. The majority of

crew activities fall into four categories:

training, science and exploration, systems

operation and maintenance, and

programmatic.

•Training activities include such areas as

prelaunch survival training for all critical

life support systems, operational and

maintenance training on mission-critical

hardware, prelaunch and in-flight

proficiency training for critical mission

phases, and science and research

training for accomplishing primary

science objectives.

•The majority of science and exploration

activities will be accomplished on the

surface of Mars. They include, but are

not limited to, teleoperated robotic

activities, habitability experiments, local

and regional sorties, and planetary
3-22

science investigations. Supplemental

science objectives may be accomplished

during other phases of the mission as

well.

•During the first mission, a substantial

amount of crew time will be spent

operating and maintaining vehicle

systems. This time allocation is expected

to decrease with subsequent missions as

the systems and operational experience

base matures.

•Lastly, programmatic activities for the

crews include publicity, documentation,

reporting, and real-time activity

planning.

This report does not make specific

conclusions regarding hardware

requirements, facilities requirements, and

training programs, but a number of

recommendations and guidelines regarding

these areas have been developed and tailored

to the various mission phases that will be

experienced by each crew sent to Mars. While

these and other crew activities may not be

seen as directly affecting program success, all

areas contribute to the successful completion

of each mission and are, therefore, essential to

the overall success of the Reference Mission.

3.4.1 Training Guidelines

The key to successful operations is

having well prepared, knowledgeable team

members. This knowledge and preparation is

most effectively obtained by training for

nominal and contingency operations.

Extensive training in these areas will improve

overall mission success as well as contribute

to meeting science and exploration objectives.

Several overriding principles must govern the

way training is conducted for the Reference

Mission. Due to time constraints, crew

training in preparation for the first mission

must be done concurrently with vehicle and

training facility development. The first crew

and mission controllers will be supplanting

operational training with involvement in

system design and testing. This will provide

the mission team with the needed system

familiarity which would otherwise come from

operational training exercises. Operations

input on system designs also has the added

benefit of enhancing vehicle functionality and

operability (for example, nominal daily

operations such as housekeeping, food

preparation, and system maintenance will

benefit from input by the actual users).

Additional prelaunch training must

emphasize developing a working knowledge

of life-critical and mission-critical elements.

Because reliance on Earth-based ground

control becomes more difficult and less timeresponsive as the mission progresses toward

Mars, crew self-sufficiency becomes essential.

In-depth training on life-critical and missioncritical systems will enable crews to become

more self-sufficient. Contingency survival

training for failures in critical life support

systems will also be required as real-time

ground support will not be possible during

Mars surface operations and similar remote

phases of flight.
3-23

Extensive preflight and in-flight training

on critical event activities (such as major

propulsive maneuvers, Mars atmospheric

entry, surface sorties, and Earth atmospheric

entry) will be required to ensure crew

proficiency during these busy time periods.

The need for such training will require

preflight development of a well-defined

activity plan for all critical events.

Significantly less preflight training will be

required for noncritical, mission-successoriented activities such as surface science

operations. The initial surface operations

required for the establishment of the Mars

surface base and preliminary surface science

activities will be well defined before the first

crew departs. Subsequent exploration and

science activities will depend on the findings

from the initial scientific investigations. As a

result, training for more than the initial

science activities will not be feasible. Instead,

it will be necessary to ensure that crews have

the skills to enable them to plan and prioritize

real-time activities in support of the overall

mission objectives. Some planning assistance

and direction will be provided by ground

personnel; however, the responsibility for

detailed planning and execution will reside

with the crew. They are on the surface and

have firsthand knowledge of environmental

and logistical considerations.

Due to the length of the mission and

length of time between critical event

activities, proficiency training will be

necessary during all phases of the mission. In

flight and on the martian surface, training for

critical events will ensure that crews are

adequately prepared for both nominal and

contingency situations. From Earth launch

until Mars ascent and TEI is about 2 years

which necessitates an ongoing training

regime to maintain proficiency. The Earthbased training the crews received 2 years

earlier prior to Earth launch will not be

sufficient. Training for the Mars atmospheric

entry and landing phase will be conducted by

the crew during the transit between Earth and

Mars. While on the martian surface and

intermixed with other surface activities, the

crew will conduct proficiency training for the

critical Mars ascent phase, subsequent

docking with the ERV, and trans-Earth

propulsive maneuver. In-flight and surface

training requirements dictate the need for

effective training facilities in the habitat

vehicles or in the ascent vehicles. Design and

development of such facilities will require

further investigation and is beyond the scope

of this preliminary report.

Documentation in the form of computerbased libraries must be available for

operational instruction, maintenance of and

troubleshooting systems, and hardware

failures. Reliable and immediate access to this

type of information will supplement crew

training for all types of activities from

mission-discretionary to life-critical. Extensive

computer-based resources will have the

added effect of increasing crew selfsufficiency during remote mission phases.

The final, but by no means least

significant, element of crew training will be
3-24

the feedback provided by the early crews on

training applicability and effectiveness related

to all mission phases. Feedback from the first

crew in particular will need to be

incorporated into training procedures,

hardware, and facilities to be used by

subsequent crews. An effective channel for

incorporating this feedback into redesign and

upgrading of systems and procedures will be

essential for follow-on crew training.

3.4.2 Science and Exploration

The majority of science and exploration

activities will be accomplished on the surface

of Mars. They include, but are not limited to,

teleoperated robotic activities, habitability

experiments, local and regional sorties, and

planetary science investigations. Additional

science activities which supplement the

primary science objectives may be

accomplished during other phases of the

mission as well; however, the largest portion

of time and activity allocated in support of

science and exploration will occur on the

planetary surface.

Initial surface science activities will be

well defined before each crew departs Earth.

Detailed activity planning to maximize the

crews useful science and exploration time will

increase overall mission success and will be

necessary to ensure the successful completion

of many primary science objectives and

mission safety requirements. Many

investigative results designed to satisfy safety

requirements (for example, tracking crew

health) will contribute to satisfying science

objectives as well. Detailed identification of

safety requirements and related activities is

not required until later in the mission

planning process and will not be discussed

here.

Subsequent exploration and science

activities will depend on the findings from

the initial scientific investigations. As a result,

it will be necessary for crews to do real-time

science activity planning to continue research

activities. Principal investigators and ground

support personnel will provide the guidelines

for use in planning priorities of mission

objectives. However, the detailed procedures

for executing science activities must be left, in

general, to the crews who have firsthand

knowledge of the unique environmental and

logistical considerations of this mission.

Additionally, eliminating the excessive

ground planning and replanning activities

which have been customary for near real-time

manned space operations will reduce cost.

Beyond the initial investigations, several

surface science and exploration activities can

be identified preflight as targets for detailed

planning and execution: telerobotic

exploration and local and regional surface

sorties. Such preflight planning will maximize

the crew’s useful science time, maximize

science return, improve crew safety on

difficult exercises, and increase overall

mission success.
3-25

3.4.3 Systems Operations and

Maintenance

During the first mission, a substantial

amount of crew time will likely be spent

operating and maintaining vehicle systems.

This time is expected to decrease with

subsequent missions as the systems and

operational experience base mature.

However, until that time, the more familiar

the crews are with all systems, the less time

operations and maintenance will take from

science and exploration activities. To enhance

crew familiarity with the numerous vehicle

systems prior to launch, crews should be

involved in the design and testing of primary

vehicle systems. The resulting intimate

knowledge of the vehicle systems has the

added benefit of supplementing crew training

on their operational use. Another way to

facilitate crew familiarity is to ensure that

system designs are modular and easily

repairable. The simpler and more familiar the

design, the easier it is to repair and maintain.

Due to the nature of the Reference

Mission program design (where vehicles are

placed in a standby mode and subjected to

hostile environments for long durations), indepth vehicle and system checkouts will be

required periodically. Crew participation in

these activities should be minimized but may

be necessary due to their access to some of the

system hardware. Such access and

participation may make the crews uniquely

suited for analysis of anomalous results that

might appear in the system testing.

Where applicable, autonomous vehicle

health monitoring and testing will enable

crew members to use their time performing

science and exploration activities. In

conjunction with this automation, access to

hardware and software documentation for all

systems can expedite operations and

maintenance activities which require crew

participation. Additionally, due to large

resource requirements, some of the vehicle

operations, such as long-term health

monitoring, trend development or prediction,

and failure analysis, may be accomplished by

ground system support personnel. The

delineation between which system functions

are automated, crew-managed, or groundsupport-managed is not clear and is subject to

a host of variables. Some of the considerations

to be used in making this determination are

crew useful time, availability of supporting

documentation, knowledge of system

performance (that is, are we operating outside

the envelope?), time criticality of failure

recognition and recovery, and constraints on

development time and cost. General

guidelines of responsibility for vehicle

operations are best determined early in the

design process as automation of functions

will affect mission and vehicle design.

3.4.4 Programmatic Activities

Programmatic activities for the crews

include publicity, documentation, reporting,

and real-time activity planning. These types

of activities are not usually seen as directly

affecting program success. They do, however,
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and if properly planned and coordinated, will

enhance crew performance and interaction.

Like vehicle performance, crew performance

is key to a successful mission.

Successful team performance and

interaction depends on having defined roles

and responsibilities and the flexibility to

handle real-time events. For complex

programs like the Reference Mission, this is

important not only among crew member

teams, but also among ground support

personnel teams and between ground support

and the crews. For the crews, knowing who is

responsible for what and when makes for

smoother operations and can alleviate some

of the stress associated with long-term, small

space, personnel interaction. For ground and

crew interaction, clear rules governing who is

in charge of what activities and who

determines what gets done and when are

essential for maximizing mission and science

objective returns and alleviating confusion

especially during remote operations. This will

enhance operational performance when

combined with a flexible operational

architecture allowing crews to create and

optimize the methods required to handle realtime events and achieve set objectives and

goals. (Further discussion on ground

operations and team interaction can be found

in Section 3.8.)

Public affairs activities have been and

always will be an integral part of crew

activities. While they absorb resources

(mostly time), they also bring public and

political support to programs and contribute

to program success. Crew resources from

preflight through postlanding will have to be

allocated in support of this activity.

Another element which contributes to

program success is the crew feedback on all

aspects of the mission. Their input on system

designs, operations, science activities (for

example, appropriateness, preparedness,

required hardware), and training effectiveness

is necessary for the continued improvement

and enhancement of follow-on missions.

Along these same lines, documentation of all

activities (such as procedural changes, lessons

learned, observations, hardware

discrepancies) is a time-consuming but

necessary crew activity. (Using various

electronic systems rather than similar paper

systems for documentation preparation will

provide savings in terms of mass, reliability,

reduced consumables, etc.) Crew records can

be used to contribute to mission feedback as

well as documentation. Documentation and

feedback are important, especially for the first

crew, to ensure optimal use of the subsequent

crew’s time and to enhance the chances of

success of future missions of this type.

3.4.5 Activity Planning

The level of crew operations in training,

science and exploration, systems operations

and maintenance, and programmatic

activities varies throughout different phases

of the mission; however, some characteristics

are consistent throughout the phases. For

instance, life-critical or mission-critical
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activities, regardless of mission phase, require

detailed planning and precise execution. In

contrast, non-life-critical or mission-critical

science and exploration activities may rely on

real-time procedures generated by the crew

whose guidelines for planning will be to

achieve set mission objectives and goals.

Guidelines for crew activity planning must

incorporate the flexibility to adapt to the

crew’s experience as they learn to live and

work in a new environment.

In general, crew activity planning must

be done using a relatively fixed format and

timeline. This will allow crew members to

readily adapt to the various environments in

which they will be expected to work and live.

Having regular awake and sleep times,

consistent meal times, etc., from phase to

phase will help the crew adapt to mission

phase transitions. Having a consistent length

workday is also important. With the Mars day

lasting nearly 25 hours, adhering to an Earthbased daily schedule of 24 hours would

routinely have the crew awake during

martian night. A consistent 25-hour day

throughout all phases of flight should be

considered.

A typical work schedule on the Space

Shuttle has crew members working

throughout an entire flight, only getting time

off during extremely long flights (those

approaching 2 weeks in duration). For

missions that can last a number of years, a

consistent long-term work schedule must be

developed that will give crew members

sufficient time off yet maintain productivity

and the success of mission objectives.

Feedback from the crew will be important

during the early phases of this mission, as

both ground support and flight crew

members adapt to the unique environmental

and operational challenges of the mission.

3.4.5.1 Prelaunch Phase

Crew activities during the prelaunch

phase of the mission will concentrate on

training activities for all mission phases. Early

on in the program development, crew

involvement in design and testing of primary

systems will help facilitate crew familiarity

with the systems and enhance applicability of

system designs. The resulting intimate

knowledge of the vehicle systems has the

added benefit of supplementing crew training

on their operational use. Extensive training on

nominal everyday operations (such as

housekeeping and food preparation) will also

make the crew more comfortable in their

changing environments. Strong emphasis on

critical life support and mission-critical

systems training will also be required.

An important part of crew training

activities in this prelaunch phase will be

participation in integrated training activities

with scientists and systems engineers.

Preflight interaction with the science

community, in the form of experimental

exercises (crews learn to conduct scientific

investigations) and exploration exercises

(crews simulate local and remote sortie

operations) will enhance overall mission

success and scientific return. This will benefit
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not only the crew but also the ground science

and systems teams by forcing them to interact

in a way that will be unique to remote

operations.

Crew involvement in integrated training

for critical activities (such as launch, injection

phase, Earth orbit systems checkout, Mars

landing phase, return phases) will be needed

to ensure crew proficiency and performance

during these phases. Simulations which stress

the crew and ground support by introducing

failures and abort scenarios will help ensure

crew safety should such instances occur

during the mission.

In addition to prelaunch training

activities, extensive medical testing will be

required of the crew during this time. Their

long- and short-term health will be critical

factors in the success of this type of longduration mission.

3.4.5.2 Earth Launch Phase

The Earth launch phase is defined as the

crew activities required to support mission

activities from launch through TMI and

subsequent powerdown of nonessential

hardware. It is expected that some systems

used during the launch phase will not be

required until later in the mission. The

hardware which fits in this category will be

placed in a quiescent mode to conserve

resources.

During the Earth launch phase of the

mission, the crew’s primary focus will be to

ensure a safe launch and Mars injection.

Nominal actions directly associated with the

launch are expected to be minimal. Once in

orbit, crew activities will center on a complete

checkout of vehicle systems prior to leaving

Earth orbit while near real-time

communications with ground support are

possible. This checkout will include all lifecritical, mission-critical, and missiondiscretionary systems with appropriate

actions being taken for anomalies on each

system according to its criticality. Such a

checkout, which will be as automated as

possible, will require some crew and ground

support actions either for testing or for

troubleshooting failures.

While in Earth orbit but before TMI,

limited time or personnel may cause some of

the less critical pre-TMI testing to be deferred.

For instance, testing on mission-discretionary

hardware intended for use only on the

martian surface may be delayed until later in

the transit to Mars. Such decisions will be

more appropriately made when vehicle

system checkout requirements are identified

during the design process. Additionally, such

real-time decisions may be made based on

assessments of other activities during the

Earth orbit phase.

Training activities will not be scheduled

during the Earth launch through TMI phase

of the mission as the crew will have been

trained for these activities prior to launch.

Additionally, with the exception of those

activities related to crew health maintenance

and monitoring, planned science activities

will not be performed during this high
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systems activity time frame. Medical testing

and assistance may be required during this

phase as crew members adapt to the change

in environment. (The number of crew

members who typically do not experience

space sickness during the first few days of

weightlessness is just one in three based on

171 Shuttle crew members (Reschke, et al.,

1994).) Any serious life- or missionthreatening crew illness prior to TMI will be

reason to abort the mission.

Throughout all mission phases,

documentation of activities and feedback on

training effectiveness will be required of all

crew members. This will be essential in order

to make effective use of the training time of

the follow-on crew and the program’s

training hardware. Due to the high systems

activity during this phase, documentation

and other programmatic activities will be

either minimal or deferred to a later time.

3.4.5.3 Trans-Mars Phase

The trans-Mars phase of the mission is

defined as crew activities from post-TMI

system powerdown through Mars Orbit

Insertion (MOI) preparation. This

interplanetary transit phase will be fairly

homogeneous from the standpoint of

environment and crew activity. Crew

activities related to vehicle systems are

expected to be minimal. Only nominal

operations (housekeeping, food preparation,

etc.) will be required unless missiondiscretionary systems testing has been

postponed until after TMI. This decision may

be made prior to launch based on time or

personnel constraints or based on the result of

earlier failures. Activities for failure analysis

and troubleshooting will be accomplished on

an as needed basis.

The relatively quiescent vehicle system

activity during the transit phase makes it

well-suited for crew training activities.

During this time, additional training time can

be made available for the training above and

beyond the preflight training that is required

to maintain crew proficiency during the

relatively long Mars transit time. The need for

in-flight training will require that training

simulators be available to the crew in the

transit-habitat vehicle. Critical events that will

require training during this time are MOI,

landing, and Mars launch activities.

Additional time may also be made available

for training and review of payload and

science hardware to be used on the surface.

During the transit phase, time may be

available for limited science activities. The

primary restriction on conducting

interplanetary science activities will likely be

mass related. Interplanetary science

(astronomy, solar observations) is not the

primary science objective for this type of

mission; and, as such, related hardware will

only be provided for crew use if mass

margins exist at the appropriate point in the

design process. However, there may be

opportunities for useful scientific data return

which can “piggy-back” on instruments

provided for crew safety issues. An example

would be conducting some solar science
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experiments as part of meeting requirements

for crew safety (as in solar flare detection).

Also, medical testing will be required

periodically throughout this phase to verify

crew health. Related studies on crew

adaptation to the space environment and

other health-related biomedical science

experiments may benefit from such testing.

As with all mission phases,

documentation of activities and feedback on

training effectiveness will be required of all

crew members in order to make effective use

of the follow-on crew’s training time.

Additionally, the information will provide

engineers on Earth with guidelines for

upgrading and improving the vehicle systems

and training hardware. Transit time is ideal

for documenting current and earlier phases of

the mission.

Due to the high interest in such a

mission, the crew will be required to

participate in numerous public affairs

activities. International participation in this

type of mission will only increase press

demands on crew time. Press and crew

exchanges will be particularly productive

during relatively quiescent periods early in

the transit phase when communication lag

times are short. As communication lag time

increases, the necessity for crew autonomy

will become evident. However,

communication with Earth will still have to

be provided for failure assistance and crew

personal interaction with Earth.

Communication activities will be higher

during the initial and critical mission phases,

and appropriate time must be allocated

during the crew schedule for such activities.

3.4.5.4 Mars Landing Phase

The Mars landing phase is a very

dynamic phase of the mission and is defined

as the time from MOI preparation through

postlanding crew recovery and surface

system activation. Many of the activities

during this time frame will have been

planned in detail before launch and perhaps

updated during the interplanetary transit.

Prior to MOI the crew will have to

prepare the transit-habitat vehicle for

transition from a zero-g to a partial-g surface

vehicle. All peripherals, supplies, and

hardware that have been taken out for use

during transit will have to be safely stowed.

Nonessential equipment will be powered

down in exchange for equipment necessary

for this phase of flight. During this time, the

crew will have to checkout or verify the

operational status of all hardware and

software required for the upcoming critical

MOI and landing activities.

Pre-MOI activities must be initiated early

enough to allow sufficient time to

troubleshoot any failures or discrepancies

prior to the critical phase. Many of the

activities during this phase will, by necessity,

be automated. However, crew intervention

and override must be available due to the

uniqueness and criticality of this phase of the

mission (for example, doing critical activities

without real-time support in a new and

unique environment) and in general as a

backup to the automated systems.
3-31

After landing, a thorough vehicle

checkout will be necessary due to the drastic

transition in operational environment from

vacuum and zero g to a planetary surface

environment. Initially, the only checkout

which will be done will be on those systems

required to certify that crew safety and lifesupport systems and their backups are

operational.

Crew training activities during the latter

part of the transit phase and the early part of

the landing phase will intensely focus on

critical activities for the MOI and landing

phase so that the crew is adequately prepared

for upcoming events. Again, this will require

that adequate training facilities be available to

the crew on the transit-habitat vehicle.

Minimal science activities will be done

during the Mars landing phase. Time may be

available for limited orbital observations to

take advantage of the unique opportunity to

photograph and gather remotely sensed data

of Mars on approach and from orbit.

However, this will depend on the available

mass allocated for this type of equipment, the

success of the higher priority critical systems,

and the training activities during this time

frame.

Due to the high systems activity during

this phase, documentation and other

programmatic activities will be minimal.

Those activities necessary to improve the

follow-on crew’s training time and program

training hardware will be deferred until the

crew has time available.

On approach and on the surface of Mars,

communication lag time with Earth will be

near or at its maximum. During such a critical

phase of flight, crew functions will, of

necessity, be virtually autonomous from

Earth-based support. Some communication

with Earth will still have to be provided for

failure assistance and vehicle health

monitoring of trend data. Such requirements

may drive the need for regular, perhaps

continuous, communications capability with

Earth.

3.4.5.5 Mars Surface Phase

The Mars surface phase is defined as

postlanding recovery operations to prelaunch

operations. In general, this phase of the

mission will receive a minimal amount of

mission-specific planning and training prior

to departing Earth; its focus will be on the

mission’s primary science and exploration

activities which will change over time to

accommodate early discoveries. A general

outline of crew activities for this time period

will be provided before launch and updated

during the interplanetary cruise phase. This

outline will contain detailed activities to

ensure initial crew safety, make basic

assumptions as to initial science activities,

schedule periodic vehicle and system

checkouts, and plan for a certain number of

sorties. Much of the detailed activity planning

while on the surface will be based on initial

findings and therefore cannot be

accomplished before landing on Mars.

However, the crew will be provided with
3-32

extensive, but not mission-specific, training

related to scientific investigation and vehicle

systems. This will assist the crew in planning

specific activities in these areas, as required,

while on the martian surface.

Initial postlanding systems activities will

focus on hardware testing and verification for

life support, then mission-critical, and finally

mission-discretionary systems. The initial

phase of these checkouts must be done

without the requirement for EVAs. EVAs will

be restricted until sufficient data have been

collected to fully characterize the immediate

martian environment. Once it has been

confirmed that the martian environment is

not a threat to crew health or mission success

(assuming this has not been done by prior

robotic missions), EVAs may then be

accomplished to complete required systems

testing and verification.

During the crew stay-time on the surface

of Mars, additional full-scale testing and

verification of some hardware will be

required. After vehicle system checkout of the

crew habitat shortly after crew arrival,

activities for joining the crew habitat with a

previously landed laboratory may begin.

Complete connection of these two vehicles

will be accomplished after a full verification

of each vehicle’s individual integrity is

completed. Also during the initial

postlanding time frame, verification and

system status check of the vehicles needed for

crew launch and Earth return will be

required. While much of this activity will be

autonomous and supervised by ground

operations personnel, crew involvement

provides the crew with confidence in their

return systems, enables visual verification of

ascent vehicle system integrity, and allows for

crew interaction or intervention in anomaly

troubleshooting on surface hardware. Beyond

annual, comprehensive vehicle checkouts,

system activities for the crew will consist of

maintenance, housekeeping, consumables

tracking, and repair operations.

Initial science activities during the

surface phase will concentrate on verifying

crew health and safety on the martian surface.

Atmospheric, chemical, and biological studies

of the immediate environment surrounding

the crew habitat will be critical to ensure crew

safety. Once the immediate environment is

characterized and potential threats well

understood, planning for future local and

regional sorties may begin. Some general

planning of these initial science activities may

be done in advance; however, much of the

crew activity will depend on the initial

findings and therefore cannot be prepared

prior to launch. The crew must be provided

with enough expertise and applicable

hardware and resources to help them deal

with potential unforeseen discoveries and

obstacles to their investigations.

Prior to the first EVA and sortie, robotic

exploration may map local areas and allow

investigators to seek out interesting sites for

regional sorties. Mission preparation will

have assumed a minimum number and type

of EVAs; however, adaptation to real-time
3-33

discoveries will be necessary for many of

these excursions.

Additional biomedical health science

activities performed on the crew will be

required during the surface phase as well.

Safety issues, health examinations,

investigations to gather data on low-g

adaptation, and long-term physiological

effects on the crew will also be conducted

during the surface phase.

As with other phases of flight, there may

be opportunities for some scientific data

return which can piggy-back on instruments

provided for crew safety issues. For instance,

limited solar science may be provided in part

for crew safety issues (as part of solar flare

detection), thus providing opportunity for

additional solar science observations while on

the martian surface.

Training during surface operations will

be periodic to maintain proficiency for

mission-critical activities (such as launch and

Earth return). Additional training activities,

on an as needed basis, may be required for

activities such as sorties and EVAs.

Documentation of activities and feedback

on training effectiveness will be required of

all crew members in order to make effective

use of the follow-on crew’s training time. The

information will provide engineers on Earth

with guidelines for upgrading and improving

the vehicle systems and training hardware.

Additional documentation of scientific

experiments and results will need to be

relayed to Earth for use by the science teams

in analysis and future planning.

Time will also be allocated for public

affairs events. These types of events will not

be interactive due to the time lag, but will be

recorded and subsequently transmitted to

Earth. Requests from news media and other

organizations will be reviewed, scheduled,

and then relayed to the crew through mission

management personnel on Earth. Activities

such as these will require a flexible planning

architecture in which crew and ground

support both participate.

All of the above mentioned surface

activities will require some level of

communication with mission teams on

Earth—both science and systems teams.

Analysis of the communication requirements

will result from a combination of system data

requirements, crew health data requirements,

crew personal communications, and science

data requirements.

3.4.5.6 Mars Launch Phase

The Mars launch phase is a very dynamic

phase of the mission and is defined as the

activities from preparation for launch through

TEI and nonessential hardware powerdown.

Many of the activities during this time frame

will have been planned in detail prior to

launch from Earth.

Before committing the crew to Mars

ascent and Earth return activities, full systems

checkout of the MAV and ERV is required.

Because both vehicles are critical to crew

safety and survival, sufficient time must be

provided prior to launch to verify systems

and troubleshoot any anomalous indications
3-34

prior to crew use. Additional crew time will

be spent preparing the surface habitat and

other facilities for an untended mode. Such

activities will include stowing any

nonessential hardware, safing critical systems

and their backups, and performing general

housekeeping duties which will facilitate use

of the facilities by future crews.

Once the crew has prepared all surface

equipment for departure, the actual departure

activities will begin. Detailed activities for this

departure will have been prepared and

simulated on Earth, so a detailed plan for

Mars launch through TEI will be available

and executed at the appropriate time.

Contingency scenarios will also have been

planned prior to Earth launch, and enough

time will be allocated during ascent and

rendezvous activities to enable successful

operations within these contingencies. After

successful launch, rendezvous with the return

vehicle, and TEI, the crew will again place

nonessential hardware in a quiescent mode

for the return trip.

In the time period leading up to the Mars

launch phase, the crew will spend an

increasing amount of time training and

preparing for this extremely critical phase of

the mission. In particular, the rendezvous

with the ERV will require attention. Sufficient

training facilities must be available on the

surface to ensure crew proficiency in these

activities prior to execution. Also,

physiological training for the return to a zerog and eventually a one-g environment will be

dramatically increased during prelaunch.

During this most critical of time frames,

other activities such as public affairs events

and documentation of activities will be

minimized. Due to the critical nature of this

mission phase, communication transmissions

to Earth will be necessary for failure

assistance and vehicle health monitoring.

However, due to the nature of the lag time

and the criticality of events, vehicle and crew

activities will remain fairly autonomous.

3.4.5.7 Trans-Earth Phase

The trans-Earth phase is defined as the

post-TEI powerdown through preparation for

Earth landing. This interplanetary transit

phase will be fairly homogeneous from an

environment and crew activity standpoint.

The crew activities related to vehicle systems

are expected to be minimal. Only those

activities required for nominal operations will

be required (housekeeping, food preparation,

etc.).

Crew training activities during this time

frame will focus on the critical Earth entry

and landing phase of flight. This will drive an

ERV hardware requirement to provide the

crew with adequate simulators and on-board

training facilities to maintain proficiency in

vehicle operations. The crew will also begin a

regime of zero-g countermeasure activities

(such as exercise, lower body negative

pressure, etc., depending on the best available

knowledge at the time) to prepare themselves

physically for return to a one-g environment.

Again, due to the relatively quiescent

system activity during the transit phase, time
3-35

may be available for the crew to do limited

science activities. The restrictions on

interplanetary science activities will be mass

related. Medical testing will be required

periodically throughout this phase in order to

meet biomedical science objectives and verify

crew health for entry.

During this time frame, documentation

activity will be extremely important due to

the fact that the next crew will be launched

prior to the return crew’s landing.

Additionally, the information will provide

engineers on Earth with guidelines for

upgrading and improving the vehicle systems

and training hardware. Due to time

considerations, some handover

documentation for the next crew will have

been prepared prior to leaving Mars. Final

transfer of vehicle status is recommended to

be direct from crew to crew to prevent

confusion and ensure thoroughness. Some

aspects of the hand over may be filtered

through ground support in order to simplify

communications requirements.

Due to the high interest in such a

mission, the crew will be required to

participate in numerous public affairs

activities. Quiescent periods of transit time

can provide opportunities for press and crew

interaction.

3.4.5.8 Earth Entry and Landing

The Earth entry and landing phase is

defined as the crew activities which support

preentry preparation through landing and

crew health recovery. Because it is not

currently known how prolonged low-g and

zero-g environments will affect the human

physiology, the main focus of this phase of

flight will be the safe return and recovery of

the crew.

Crew activities related to vehicle systems

will be emphasized prior to entry. System

checkout will be required with sufficient time

prior to entry to allow for troubleshooting

any failures and guarantee a safe crew

landing. Upon landing, vehicle safing and

powerdown will be required. Due to the high

probability of lower than normal physical

capability among the crew, many of the

postlanding system activities should be

automated.

No training or science activities will be

planned during this critical phase of flight.

Crew health monitoring will be conducted for

the purposes of crew health and safety. Also,

due to the time-critical nature of this phase,

documentation will be minimal and will

pertain only to crew preparedness and system

performance.

3.4.5.9 Postlanding

The postlanding phase of crew

operations is defined as the activities

conducted after vehicle powerdown through

mission termination. In most instances,

mission termination will not be a well-defined

time and may be different for different

members of the crew as crew involvement in

additional program activities is subject to

various conditions.
3-36

Face-to-face debriefings with the

engineers responsible for individual systems

and vehicles will be beneficial after landing.

Such meetings can be more productive and

provide more information than written

documentation. Feedback on all training

activities and facilities throughout the mission

will also be beneficial postlanding as it will

facilitate the training of follow-on crews.

Medical testing after landing will

continue as part of long-term health

monitoring. This may be required for an

indefinite period of time. Some effects from

the mission may not appear until months or

even years after the flight phases of the

mission have ended. Therefore, the crew

members should be subject to periodic

medical testing for observation of long-term

effects of the mission. It may also be necessary

to satisfy quarantine issues, whether real or

political, immediately upon return to Earth.

(Quarantine issues will have to be addressed

early in the mission planning phases to

ensure that adequate facilities are available

when and if they are needed.)

Formal documentation of all aspects of

the mission will be required of all crew

members after landing. Additional emphasis

will be placed on providing engineers on the

ground with guidelines for upgrading and

improving vehicle systems and training

hardware.

Due to the high interest in such a

mission, the crew will be required to

participate in many public events and

debriefings after they return to Earth.

3.5 Mission Design

The focus of this section is to describe a

feasible sequence of flights on specific

trajectories with specific systems that

accomplish Reference Mission goals and

objectives. Foremost among the choices that

must be made is the type of trajectory to use.

It must be one that can accomplish mission

objectives using a reasonable transportation

system and at the same time address the risk

mitigation strategy and still provide for

flexibility within a development and flight

program. Other assumptions made that affect

the “how” of mission implementation are

discussed as part of the overall mission

strategy. With these elements in place, this

section presents a discussion that includes

such information as launch and arrival dates,

payload manifests, and crew activities for

each flight in the set studied for this Reference

Mission.

3.5.1 Trajectory Options

Trajectory options between Earth and

Mars are generally characterized by the

length of time spent in the Mars system and

the total round-trip mission time. The first

option is typified by short Mars stay-times

(typically 30 to 90 days) and relatively short

round-trip mission times (400 to 650 days).

This is often referred to as an opposition-class

mission, although this report has adopted the

terminology “short-stay” mission. The

trajectory profile for a typical short-stay

mission is shown in Figure 3-2. This class has

higher propulsive requirements than the often
3-37

considered long-stay missions, and typically

requires a gravity-assisted swingby at Venus

or the performance of a deep-space

propulsive maneuver to reduce total mission

energy and constrain Mars and Earth entry

speeds. Short-stay missions always have one

short transit leg, either outbound or inbound,

and one long transit leg, that requires close

passage by the Sun (0.7 AU or less). A

significant characteristic of this class of

trajectory is that the vast majority of the

round-trip time, typically over 90 percent, is

spent in interplanetary space. The second

mission class consists of long-duration Mars

stay-times (as much as 500 days) and long

total round-trip times (approximately 900

days). This mission type is often referred to as

conjunction-class, although this report has

adopted the terminology “long-stay” mission.

These represent the global minimum-energy

solutions for a given launch opportunity. The

trajectory profile for a typical long-stay

mission is shown in Figure 3-3.

Within the long-stay category of

missions, the option exists to dramatically

decrease the transit times to and from Mars

through moderate propulsive increases. The

total round-trip times remain comparable to

those of the minimum-energy, long-stay

missions; but the one-way transits are

substantially reduced, in some cases to less

than 100 days, and the Mars stay-times are

increased modestly to as much as 600 days.

The round-trip energy requirements of this

class, referred to as a “fast-transit” mission,

are similar to the short-stay missions even

though the trajectories are radically different.

The profile for a typical fast-transit mission is

shown in Figure 3-4.

Figure 3-3 Typical long-stay mission

profile.

γ

MISSION TIMES

OUTBOUND 224 days

STAY 458 days 

RETURN 237 days

TOTAL MISSION 919 days

Earth Launch

1/17/2014

Depart Mars

11/30/2015

Arrive Mars

8/29/2014

Earth Return

7/24/2016

Figure 3-2 Typical short-stay mission

profile.

γ

DEPART 

MARS

9/26/2014

EARTH 

RETURN

7/14/2015

ARRIVE 

MARS

8/27/2014

VENUS 

FLYBY

2/23/2015

DEPART 

EARTH

1/15/2014

MISSION TIMES

OUTBOUND 224 days

STAY 30 days 

RETURN 291 days

TOTAL MISSION 545 days
3-38

3.5.2 Trajectory Selection Factors

Three factors make the selection of the

trajectory class critical to the Reference

Mission. First, the selection must be consistent

with achieving the Mars exploration goals

and objectives. Second, the selection must be

consistent with the risk philosophy of the

Reference Mission. And third, for

programmatic reasons, the trajectory class

selection must provide the flexibility to

conduct missions in all opportunities within

the 15-year Earth-Mars trajectory cycle and to

conduct missions supporting the evolution of

Mars exploration objectives and

implementation strategies.

3.5.2.1 Satisfying Reference Mission Goals

and Objectives

The goals and objectives of the Reference

Mission focus on allowing human crews to

spend the greatest amount of time on the

surface of Mars for the investment made to

transport them there and to learn as much as

possible about how humans react in this

environment. Verifying the ability of people

to inhabit Mars requires more than a brief

stay of 30 days at the planet. In addition, the

low return on investment associated with a

30-day stay at Mars (of which significantly

less than 30 days would actually be

productively spent on the Mars surface due to

the crew adaptation to the Mars gravity, crew

preparations for Mars departure, etc.) was

considered unacceptable. Following the

August 1992 Workshop (Duke, et al., 1992), it

was decided that the “Plant the Flag” mission

objective was not a tenable rationale to

support the substantial investment involved.

Consequently, a long-stay trajectory option

was considered to be best able to satisfy the

greatest number of mission goals and

objectives.

3.5.2.2 Satisfying Reference Mission Risk

Strategy

The applicability of each of the

previously discussed mission types to the

human exploration of Mars has been the

subject of much debate. The general opinion

is that the initial flights should be short-stay

missions performed as fast as possible (socalled “sprint” missions) to minimize crew

exposure to the zero-g and space radiation

environment, to ease requirements on system

reliability, and to enhance the probability of

mission success. However, when considering

“fast” Mars missions, it is important to

specify whether one is referring to a fast

round-trip or a fast-transit mission. Past

Figure 3-4 Fast-transit mission profile.

γ

Earth Launch

2/1/2014

Depart Mars

3/11/2016

Arrive Mars

7/1/2014

Earth Return

6/29/2016

MISSION TIMES

OUTBOUND 150 days

STAY 619 days 

RETURN 110 days

TOTAL MISSION 879 days

Nominal 

Departure

3/11/2016
3-39

analyses have shown that decreasing roundtrip mission times for the short-stay missions

does not equate to fast-transit times (that is,

less exposure to the zero-g and space

radiation environment) as compared to the

long-stay missions. Indeed, fast-transit times

are available only for the long-stay missions.

This point becomes clear when looking at

Figure 3-5 which graphically displays the

transit times as a function of the total roundtrip mission duration. Although the short-stay

mission has approximately half the total

duration of either of the long-stay missions,

over 90 percent of the time is spent in transit,

compared to 30 percent for the fast-transit

mission.

The interplanetary ionizing radiation of

concern to mission planners consists of two

components: galactic cosmic radiation (GCR)

and solar particle events. NASA policy

establishes that exposure of crews to radiation

in space shall not result in heath effects

exceeding acceptable risk levels. At present,

acceptable risk levels are based on not

exceeding long-term cancer risk by more than

3% above the natural cancer death probability

(which is approximately 20% lifetime risk for

the US population as a whole). At present,

the information required to calculate

acceptable risk from radiation exposure

during a Mars mission, especially for the

GCR, is not available. Although doses (the

average physical energy deposition by

incident particles) can be calculated, the

conversion of this information into a

predicted radiation risk cannot be done

accurately. The National Research Council

recently issued a report estimating the

uncertainty in risk predictions for GCR can be

as much as 4-15 times greater than the actual

risk, or as much as 4-15 times smaller.

Current knowledge does allow for some

qualitative conclusions to be drawn. Radiation risk on the Mars surface, where the GCR

fluence is attenuated by 75 percent due to the

Mars atmosphere and the planet itself, is

likely to involve less risk than a comparable

length of exposure in interplanetary space. If

the difference in radiation effectiveness

between the interior of a shielded spacecraft

and a habitat on the surface of Mars is not

considered, the GCR fluence to which crews

are exposed during a 500 plus day transit to

Mars is equivalent to approximately 125 days

of Mars surface exposure. A significant

reduction in transit time, to 100 days for the

one-way transit, would result in a radiation

exposure comparable to the short-stay

mission. Thus, the risk to crews on fasttransit missions may be even less than the risk

Outbound Transit Time at Destination Return Transit 

0 100 200 300 400 500 600 700 800 900 1000

Short-Stay

Long-Stay 

(Fast-Transit)

Long-Stay 

(Minimum 

Energy) 

Mission Duration, Days 

Figure 3-5 Round-trip mission

comparisons.
3-40

to crews on short-stay missions, not only

because of minimized exposure to GCR but

also reduced probability of exposure to solar

particle events in interplanetary space.

A similar analysis of mission classes is

involved in considering the crew’s exposure

to the zero-g environment during transits to

and from Mars. Significant physiological

changes occur when zero-g time begins to be

measured in weeks or months. (Bone

decalcification, immune and cardiovascular

system degradation, and muscular atrophy

are a few of the more unpleasant effects.)

Research on the effects of long-term zero-g on

the human body is in an elementary stage. At

the time of the writing of this report, the

longest continuous stay in space by a U.S.

astronaut is the 181 days of Shannon Lucid

(aboard the Russian MIR Space Station); the

longest stay by a Russian cosmonaut is 366

days. In none of the cases were crews exposed

to zero-g/partial-g/zero-g sequences similar

to that projected for Mars missions. Current

data indicates that recovery in a one-g

environment can be fairly rapid (a few days),

but development of full productivity could

require significantly more time. Upon arrival

on the martian surface, the crew will need to

spend some currently unknown, but probably

short, time re-adapting to a partial-g field.

This may be of concern for the short-stay

missions where a substantial portion of the

surface stay-time could be consumed by crew

adaptation to martian gravity. Conversely,

ample time will be available for the crew to

regain stamina and productivity during the

long surface stays associated with the

minimum-energy, fast-transit missions.

Several potential solutions to the

physiological problems associated with zero-g

transits to and from Mars may exist:

countermeasures (exercise, body fluid

management, lower body negative pressure),

artificial-g spacecraft, and reduced transit

times.

The usefulness of countermeasures to

reduce some of the zero-g effects is still

unknown. Russian long-duration crews have

experienced physiological degradation even

when rigorous exercise regimens have been

followed. However, most of these effects seem

to be quickly ameliorated upon return to a

one-g environment, at least when immediate

medical aid is available.

Rotating the Mars transfer vehicle (MTV)

and ERV is a method of providing an

artificial-g environment for the crew and is

most often associated with low-performance

propulsion systems, or the short-stay class of

trajectories (since both require long transit

times). Studies have indicated that the MTV

design mass penalties are on the order of 5

percent to 20 percent if artificial g is

incorporated. Depending on the specific

configuration, there may also be operational

complications associated with artificial-g

spacecraft including EVA, maintenance, and

the spin-up/spin-down required for

midcourse maneuvering and rendezvous and

docking.
3-41

Figure 3-6 illustrates some example

transit times for minimum-energy, fast-transit,

and short-stay missions. Note that all oneway transits are within the Russian zero-g

database.

However, the surface stay-times for

short-stay missions are typically 1 to 3

months. It is unknown whether such a short

time spent in a 0.38-g field will counteract 5

months of outbound zero-g exposure. In

contrast, the one-way trip times of

representative fast-transit missions are nearly

within the current U.S. zero-g database,

which will certainly be augmented by normal

International Space Station operations prior to

executing human interplanetary missions.

Also note that the fast-transit mission’s zero-g

transfer legs are separated by a substantial

period of time in the martian gravitational

field. This long period on the surface of Mars

may prove sufficient to ameliorate the

physiological effects of the relatively short

outbound transit.

3.5.2.3 Satisfying Reference Mission Program

Flexibility

Finally, the selection of trajectory type

depends on its allowance for flexibility to

respond to mission opportunities and

implementation strategies. The higher energy,

short-stay missions significantly vary in both

propulsive requirements and round-trip flight

times across the 15-year Earth-Mars trajectory

cycle. Additionally, these missions generally

require the use of a Venus swingby maneuver

to keep propulsive requirements within

reason. However, these swingbys are not

always available on the return transit leg and

must be substituted in the outbound transit

leg. Because the transit leg containing the

Venus swingby is the longer of the two, the

crew will spend up to 360 days on the trip to

Mars, with any associated physiological

degradation occurring at the beginning of the

mission—that is, prior to the crew’s arrival at

Mars. These variations in the trajectory

energy requirements can significantly impact

the configuration of the Earth-Mars

transportation elements for different EarthMars opportunities. Programmatically, such a

result is unattractive. In contrast, the

minimum-energy, long-stay missions exhibit

very little variation over the 15-year cycle,

while the fast-transit long-stay missions

reflect only moderate variations across the

same 15-year cycle. In addition, neither

Figure 3-6 Microgravity

comparisons for various mission

classes.

0

100

200

300

400

500

600

Minimum Energy * Fast-transit * Short Stay **

Outbound

Inbound

Total

Time

(Days)

Maximum 

Soviet 

Experience 

(366 Days)

* Zero-g transits separated by long surface stay (450-600 days)

** Zero-g transits separated by short surface stay (30-90 days)

Maximum US

Experience 

(84 Days)
3-42

mission requires a Venus swingby or travel

inside the Earth’s orbit around the Sun.

3.5.3 Mission Design Strategy

Keeping the Reference Mission goals and

objectives in mind, numerous alternatives

were considered that could successfully

accomplish the basic mission. Two major

considerations that drove many of the

mission design-related selections include:

•Reducing the amount of propellant

needed to move mission hardware from

one location to another (propellant mass

is the single largest element of all

components in the Reference Mission)

•Extending the amount of time spent by

the crew conducting useful

investigations on the surface of Mars.

The alternatives selected by the Mars

Study Team that impact mission design

strategy have been grouped into six major

areas and are presented here. Other

alternatives will be discussed in subsequent

sections.

3.5.3.1 Trajectory Type

The discussion presented in the previous

section led to the selection of the fast-transit,

long-stay class trajectories. However, the

amount of reduction sought in the Earth-Mars

and Mars-Earth transit times must be

balanced with other considerations.

Reductions below 180 days in the one-way

transit times (for the 2009 opportunity, the

worst case) would require either significant

propulsive capability improvements or would

necessitate much larger interplanetary

spacecraft launched into LEO for the human

missions, thereby requiring assembly and

docking in LEO and higher ETO launch rates.

Indeed, others have demonstrated that

reductions in trip times reach a point of

diminishing returns from the space transfer

vehicle design perspective (Drake, 1991).

Thus, a C3 leaving Earth of 20 to 25 km2

/sec2

appears to be appropriate for human

missions. This results in maximum EarthMars transit times of approximately 180 days

(2009 opportunity) and minimum transit

times of approximately 120 days (for the 2018

opportunity, the best case). Similarly, a C3

leaving Mars of ~16 km2

/sec2 appears to be

appropriate for human missions, resulting in

similar Mars-Earth transfer times for these

opportunities. (C3 is a measure of the energy

required to get from Earth to Mars or vice

versa. Specifically, C3 is the square of the

velocity of departure from a planet. Low C3s

are desirable because there is a direct

correlation between C3 and the size of the

transportation system.)

3.5.3.2 Split Mission Strategy

The split mission approach has been

adopted for the Reference Mission because it

allows mission elements to be broken into

manageable pieces rather than trying to

integrate all necessary hardware elements for

a single, massive launch. For this mission,

“manageable” was defined to mean pieces

that can be launched directly from Earth and

sent to Mars, using launch vehicles of the
3-43

Saturn V or Energia class, without

rendezvous or assembly in LEO. A key

attribute of the split mission strategy is that it

allows cargo to be sent to Mars without a

crew, during the same launch opportunity or

even one or more opportunities prior to the

crew’s departure. This creates a situation

where cargo can be transferred on low energy,

longer transit time trajectory, and only the

crews must be sent on a high-energy, fasttransit trajectory. By using a low energy

transfer, the same transportation system can

deliver more payload to the surface of Mars at

the expense of longer flight times. Spacing the

launches needed to support a mission across

two launch windows allows much of the

infrastructure to be pre-positioned and

checked out prior to committing crews to

their mission. When combined with the

decision to focus all Mars surface

infrastructure at a single site, this approach

allows for an improved capability to

overcome uncertainties and outright failures

encountered by the crews. Launches of

duplicate hardware elements, such as ERVs,

on subsequent missions provides either

backup for the earlier launches or growth of

capability on the surface.

3.5.3.3 Aerocapture

Mars orbit capture and the majority of

the Mars descent maneuver will be performed

using a single biconic aeroshell. The decision

to perform the Mars orbit capture maneuver

aerodynamically was based on the fact that an

aeroshell will be required to perform the Mars

descent maneuver no matter what method is

used to capture into orbit about Mars, and

current technology can develop an aeroshell

with a mass that is equal to or less than the

propulsion system required for capture. Thus,

the strategy assumed the development of a

single aeroshell that can be used for both

Mars orbit capture and descent maneuvers.

Given the demands on a descent aeroshell of

the Mars entry and landing requirements, the

additional capability to permit aerocapture is

considered modest.

3.5.3.4 Surface Rendezvous

The hardware elements launched as part

of the split mission approach must come

together on the surface of Mars, which will

require both accurate landing and mobility of

major elements on the surface to allow them

to be connected or moved into close

proximity. The alternative was to link major

components either in Earth orbit or in Mars

orbit prior to entry and landing. Previous

studies (NASA, 1989) indicated that the heat

shields for vehicles with the combined mass

implied by such an orbital rendezvous

approach would be exceedingly large and

difficult to launch and assemble in orbit.

Precision landing has been demonstrated for

the Moon (Apollo 12), and studies indicate

(Barton, et al., 1994) that available guidance

and control systems combined with a simple

beacon transmitting from the surface

(assumed to be carried by the first element at

the site) are sufficient to allow a vehicle to

land at a designated location on Mars with

uncertainties measured in meters.
3-44

3.5.3.5 Use of Indigenous Resources

The highly automated production of

propellant from martian resources is another

defining attribute of the Reference Mission.

The hardware necessary to produce and store

propellants using raw materials available on

Mars (in this case, carbon dioxide from the

atmosphere) is less massive than the

propellant needed to depart the martian

surface for orbit (Ash, et al., 1978). It is now

apparent that the technology for producing

methane and liquid oxygen from the martian

atmosphere and some nominal hydrogen

feedstock from Earth is not only an effective

performance enhancement but also appears to

be technologically feasible within the next few

years. Splitting the launch of mission

elements allows the propellant production

capability to be emplaced, checked out, and

operated prior to committing the crew to

launch from Earth. In addition to spacecraft

propulsion, this production capability on

Mars can provide fuel for surface

transportation, reactants for fuel cells, and

backup caches of consumables (water,

oxygen, and trace gases) for the life support

system. All of these features allow for smaller

amounts of consumable material to be

launched from Earth and contributes to the

goal of learning how to live on Mars.

3.5.3.6 Mars Orbit Rendezvous and Direct

Entry at Earth

The last element of mission design is

returning the crew to Earth. There are

potentially three significant propulsive

maneuvers associated with the return:

departing from the martian surface, departing

from Mars orbit, and capturing into Earth

orbit. Several alternatives are associated with

these three events, the proper selection of

which can result in a significant savings in

propellant and thus in mass that must be

launched from Earth. Three key choices

affecting this portion of the mission are made

in the Reference Mission. First, the Earthreturn transit habitat used by the crew is left

in Mars orbit. While the outbound habitat

could have been used for this task, the

propellant needed to lift it is significant; and

it is considered more valuable as part of a

growing surface infrastructure. The entire

ERV is composed of the TEI stage and the

Earth-return transit habitat. The ERV is

delivered to Mars orbit fully fueled, and it

loiters there for nearly 4 years before being

used by the crew in returning to Earth.

Second, the crew is not captured into an Earth

orbit at the completion of the mission, but

descends directly to the surface much as the

Apollo astronauts did when returning from

the Moon. The Earth crew capture vehicle

(ECCV) has the necessary heat shield for

Earth reentry. Third, the crew rides into Mars

orbit in a dedicated ascent capsule.

3.5.4 Mission Sequence

Figure 3-7 illustrates the mission

sequence analyzed for the Reference Mission.

In this sequence, three vehicles will be

launched from Earth to Mars in each of four

launch opportunities starting in 2007. The
3-45

first three launches will send infrastructure

elements to both Mars orbit and to the surface

for later use. Each remaining opportunity

analyzed for the Reference Mission will send

one crew and two cargo missions to Mars.

The cargo missions will consist of an ERV on

one flight and a lander carrying a habitat and

additional supplies on the second. This

sequence will gradually build up assets on the

martian surface so that at the end of the third

crew’s tour of duty, the basic infrastructure

could be in place to support a permanent

presence on Mars.

3.5.4.1 First Mission: 2007 Opportunity

In the first opportunity, September 2007,

three cargo missions will be launched on

minimum energy trajectories direct to Mars

(without assembly or fueling in LEO). The

first launch delivers a fully fueled ERV to

Mars orbit. The crew will rendezvous with

this stage and return to Earth after completion

of their surface exploration in October 2011.

The second launch delivers a vehicle to

the Mars surface which is comprised of an

unfueled MAV, a propellant production

Figure 3-7 Mars Reference Mission sequence.

1

2

3

6

4

5

9

7

8

12

10

ETO

FLIGHT 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

∆ MAV-1 landing

∆ Initial Habitat landing

∆ ERV-1 parks in LMO

∆ Crew 1 ascent

∆ Crew 1 TEI

∆ Crew 1 Earth return

ERV loiter

ERV loiter

ERV loiter

∆ ERV-2 parks in LMO

∆ MAV-2 landing

∆ MAV 3 landing

Crew 1: launch ∆ ∆ Landing

Crew 2 launch ∆

Crew 3 launch ∆

∆ Landing

∆ Landing

∆ ERV-3 parks in LMO

∆ Crew 2 TEI

∆ Crew 2 Earth return

∆ MAV 4 landing

∆ Ascent

∆ Crew 2 ascent

∆ ERV 4 LMO

2017

∆ Crew 3 TEI

2018

∆ Crew 3 Earth return

ERV loiter

11

ERV: Earth Return Vehicle

MAV: Mars Ascent Vehicle

TEI: Trans Earth Injection

LMO: Low Mars Orbit
3-46

module, a nuclear power plant, liquid

hydrogen (to be used as a reactant to produce

the ascent vehicle propellant), and

approximately 40 tonnes of additional

payload to the surface. After this vehicle

lands on the surface in late August 2008, the

nuclear reactor will be autonomously

deployed approximately 1 kilometer from the

ascent vehicle, and the propellant production

facility (using hydrogen brought from Earth

and carbon dioxide from the Mars

atmosphere) will begin to produce the nearly

30 tonnes of oxygen and methane that will be

required to launch the crew to Mars orbit in

October 2011. This production will be

completed within approximately 1 year—

several months before the first crew’s

scheduled departure from Earth in midNovember 2009.

The third launch in the 2007 opportunity

will deliver a second lander to the Mars

surface; it will be comprised of a surface

habitat/laboratory, nonperishable

consumables for a safe haven, and a second

nuclear power plant. It will descend to the

surface in early September 2008 and land near

the first vehicle. The second nuclear power

plant will be autonomously deployed near

the first plant. Each plant will provide

sufficient power (160 kWe) for the entire

mature surface outpost, thereby providing

complete redundancy within the power

function. The outpost laboratory will include

tools, spare parts, and teleoperated rovers to

support scientific exploration and will

provide geological and biological analyses.

Table 3-3 lists the various payload items

deployed to the surface during the first

opportunity. And Figure 3-8 illustrates the

surface outpost configuration after

deployment of payloads from the first two

cargo landers.

3.5.4.2 Second Mission: First Flight Crew,

2009 Opportunity

In the second opportunity, opening in

October 2009, two additional cargo missions

and the first crew mission will be launched.

Before either the crew or additional cargo

missions are launched from Earth in 2009, all

assets previously delivered to Mars are

checked out and the MAV launched in 2007 is

verified to be fully fueled. Should any

element of the surface system required for

crew safety or critical for mission success not

check out adequately, the surface systems will

be placed in standby mode and the crew

mission delayed until the systems can be

replaced or their functions restored. Some of

the systems can be replaced using hardware

originally intended for subsequent missions

and which would have otherwise provided

system enhancement; others may be

functionally replaced by other systems.

Table 3-4 lists the manifested payloads

for launch in the 2009 opportunity.

The first cargo launch in October 2009 is a

duplicate of the first launch from the 2007

opportunity, delivering a fully fueled Earthreturn stage to Mars orbit. The second cargo

launch similarly mirrors the second launch of

the 2007 opportunity, delivering a second
3-47

unfueled ascent stage and propellant

production module. These systems provide

backup or extensions of the previously

deployed capabilities. For example, the

second MAV and second ERV provide the

2009 crew with two redundant means for each

leg of the return trip. If, for some reason,

either the first ascent stage or the first ERV

become inoperable after the first crew departs

Earth in 2009, the crew can use the systems

launched in 2009 instead. They will arrive in

plenty of time to be available for the crew’s

departure from Mars in October 2011. If the

MAV and ERV delivered in 2007 operate as

expected, then the systems delivered in 2009

will support the second crew of six that will

launch to Mars early in 2012.

The first crew of six will depart for Mars

in mid-November 2009. They leave Earth

after the two cargo missions launched in

October 2009, but because they are sent on a

fast transfer trajectory of only 180 days, they

Table 3-3 General Launch Manifest: 2007 Launch Opportunity

Flight 1: Cargo Flight 2: Cargo Flight 3: Cargo

Surface Payload

• None • Ascent Capsule • Surface Habitat/Laboratory

• Empty Ascent Stage • Nonperishable

• LOX/CH4 Production Consumables

 Plant • Power Supply (nuclear-

• LH2 Propellant Seed 160 kW)

• Power Supply (nuclear- • Utility Truck

 160 kW) • Spares

• Utility Truck • Teleoperable Science

• Pressurized Rover Rover

• Additional Payload

Mars Orbit Payload

• Earth-Return Vehicle • None • None

• Fueled (LOX/CH4

)

 TEI Stage

• Transit Habitat

• Earth-Return Capsule

Space Transportation Vehicles

• NTR Transfer Stage • NTR Transfer Stage • NTR Transfer Stage

• LOX/CH4

 TEI Stage • LOX/CH4 Descent • LOX/CH4 Descent

 w/Mars Aerobrake Stage w/Mars Stage w/Mars

 Aerobrake Aerobrake

TEI: Trans Earth Injection LOX: liquid oxygen LH2: liquid hydrogen

NTR: Nuclear Thermal Rocket CH4: methane
3-48

Figure 3-8 Mars surface outpost after deployment of payloads from first two cargo landers.

MAV: Mars Ascent VehicleTROV: teleoperated rover

(unpressurized)

ROV: pressurized roverLSS: life support systemISRU: in-situ resource utilizationPVA: photo-voltaic array
3-49

will arrive in Mars orbit approximately 2

months prior to the cargo missions. Once the

TMI burn has been completed, the crew must

reach the surface of Mars. During the

outbound portion of this mission, the crew

will use their time to monitor and maintain

systems on board the transit spacecraft,

monitor and maintain their own physical

condition, and train for those activities

associated with capture and landing at Mars.

Additional time will be available during the

outbound leg to conduct experiments and

continue a dialog with Earth-bound science

and exploration teams who may revise or

refine the initial set of surface activities

conducted by this crew. The crew carries with

them sufficient provisions for the entire 600-

day surface stay in the unlikely event that

they are unable to rendezvous on the surface

with the assets previously deployed.

Table 3-4 General Launch Manifest: 2009 Launch Opportunity

Flight 4: Cargo Flight 5: Cargo Flight 6: First Crew

Surface Payload

• None • Ascent Capsule • Crew

• Empty Ascent Stage • Surface Habitat

• LOX/CH4 Production • Consumables

 Plant • Spares

• LH2 Propellant Seed • EVA Equipment

• Bioregenerative Life • Science Equipment

 Support Outfitting

 Equipment

• Science: 1 km drill

• Science Equipment

• Additional

 Payload /Spares

Mars Orbit Payload

• Earth-Return Vehicle • None • None

• Fueled (LOX/CH4)

 TEI Stage

• Transit Habitat

• Earth-Return Capsule

Space Transportation Vehicles

• NTR Transfer Stage • NTR Transfer Stage • NTR Transfer Stage

• LOX/CH4 TEI Stage • LOX/CH4 Descent • LOX/CH4 Descent

 w/Mars Aerobrake Stage w/Mars Stage w/Mars

 Aerobrake Aerobrake

TEI: Trans Earth Injection LOX: liquid oxygen LH2: liquid hydrogen

NTR: Nuclear Thermal Rocket CH4: methane
3-50

The crew will land on Mars in a surface

habitat almost identical to the habitat/

laboratory previously deployed to the Mars

surface. The transit habitat sits atop a descent

stage identical to those used in the 2007

opportunity. After capturing into a highly

elliptic Mars orbit (250 by 33793 km), the crew

descends in the transit habitat to rendezvous

on the surface with the other elements of the

surface outpost. There is no required

rendezvous in Mars orbit prior to the crew

descent. This is consistent with the risk

philosophy assumed for the Reference

Mission.

Figure 3-9 illustrates the surface outpost

configuration at the end of the first crew's stay.

Surface exploration activity will consist

of diverse observations by robotic vehicles

and human explorers, the collection of

samples and their examination in the outpost

laboratory, and experiments designed to

gauge the ability of humans to inhabit Mars.

Table 3-5 lists a representative set of science

and exploration equipment that will be

delivered as part of the cargo on Flight 5.

These payloads are simply examples; the

selection of specific experimental capability

will depend on the requirements of martian

science at the time that the missions are

defined in detail. There is also a category

listed for “discretionary principal investigator

(PI) science.” This category of experimental

equipment will be allocated to investigators

who have competed through a proposal and

peer review process and are selected for one

of these flights. This allows a wider range of

investigations and participants in the

exploration of Mars.

Prior to the arrival of the first human

crew, teleoperated rovers (TROV) may be

delivered to the surface. When the crew

arrives, these rovers will be available for

teleoperation by the crew. It is also possible

for the rovers to be operated in a supervised

mode from Earth. If used in this mode, the

TROVs may be designed to provide global

access and may be able to return samples to

the outpost from hundreds of kilometers

distance from the site if they are deployed

with the first set of cargo missions launched

more than 2 years before the crew arrives.

As experience grows, the range of human

exploration will grow from the local to the

regional. Regional expeditions lasting

perhaps 2 weeks, using mobile facilities, may

be conducted at intervals of a few months.

Between these explorations, analysis in the

laboratory will continue. Figure 3-10 (Cohen,

1993) provides a possible surface mission

timeline for the first 600-day mission.

The deployment of a bioregenerative life

support capability will be an early activity

following crew landing. This bioregenerative

system is not required to maintain the health

and vitality of the crew; however, it will

improve the robustness of the life support

system and is important to the early

objectives of the outpost.

The first crew will stay at the outpost

from 16 to 18 months. Part of their duties will

be to prepare the outpost site for the receipt of
3-51

Figure 3-9 Mars surface outpost at the end of first flight crew's stay.

MAV: Mars Ascent VehicleTROV: teleoperated rover

(unpressurized)

ROV: pressurized roverLSS: life support systemISRU: in-situ resource utilizationPVA: photo-voltaic array
3-52

additional elements launched on subsequent

mission opportunities. Systems associated

with the ascent vehicle, although monitored

during the entire stay on the surface, will be

checked and, if necessary, tested in detail to

ensure that they will operate satisfactorily.

The surface crew will also spend increasing

amounts of time rehearsing the launch and

rendezvous phase of the Mars departure to

sharpen necessary skills that have not been

used in over 2 years. Because the first crew

will have to depart before the second crew

arrives, surface systems will have to be in

standby mode for approximately 10 months.

After their stay on Mars, the crew uses

one of the previously landed ascent vehicles

to return to orbit, rendezvous with the ERV,

and return to Earth. Like the outbound transit

leg, the crew rides in a habitat on the inbound

transit leg. This habitat is part of the Earthreturn stage deployed in a previous

opportunity by one of the cargo flights and

typically has been in an untended mode for

nearly 4 years prior to the crew’s arrival.

During the return portion of the mission,

the crew will again spend a significant

portion of their time monitoring and

maintaining systems on board the transit

spacecraft, monitoring and maintaining their

physical condition, and training for the

activities associated with Earth return. As

mentioned previously, the second crew will

be in transit to Mars during a portion of the

first crew’s return to Earth. This implies that a

debriefing of the first crew, to gain insight

from lessons learned and suggestions for

future surface activities, will begin during this

return phase. This debriefing will be relayed

to the outbound crew so that they can

participate in the interaction with the

returning crew and modify their plans to take

advantage of the first crew’s experience.

On landing, the first crew and their

returned samples will be placed in quarantine

Table 3-5 Surface Science Payload for First Flight Crew

Payload Description Payload Mass (kg)

Field Geology Package: geologic hand tools, cameras, 335

 sample containers, documentation tools

Geoscience lab instruments: microscopes, 125

 geochemical analysis equipment, camera

Exobiology laboratory: enclosures, microscopes, 50

 culture media

Biomedical/bioscience lab 500

Traverse geophysics instruments 400

Geophysics/meteorology instruments (8 sets) 200

10-meter drill 260

Meteorology balloons 200

Discretionary PI science 300

Total 2370
3-53

Figure 3-10 Possible surface mission time line.

Mars Surface Mission Time Allocation

(Total Time = 8 crew X 24 hr/day X 600 days = 115,200 hr)

8 crew X 24 hr day = 200)

Charge Fuel Cells

Check Vehicle

Load Vehicle

Plan Excursion

Drive Vehicle

Navigate

Don Suits (X 20)

Pre-breathe (X 20)

Egress (X 20)

Unload Equip

Set up Drill (X 10)

Operate Drill

Collect Samples

In Situ Analysis

Take Photos

Communicate

Disassemble Equip

Load Vehicle

Ingress (X 20)

Clean Suit (X 20)

Stow Suit, Equip

Inspect Vehicle

Secure for night

(Sleep, eat, cleanup

hygiene, etc.

covered)

3 Crew X 7 hr X 10 Day =

210 hrs total

600 day (or 20 months, or 86 weeks)

Sleep, Sleep Prep, Dress, Undress: 8 hr

Hygiene, Cleaning, Personal Communication: 1 hr

Recreation, Exercise, Relaxation: 1 hr

Eating, Meal Prep, Clean-up: 1 hr

One Day Off Per Week: 3 hr (per day)

General Planning, Reporting, Documentation, Earth Communication: 1 hr

Group Socialization, Meetings, Life Sciences Subject, Health Monitoring, Health Care: 1 hr

System Monitoring, Inspection, Calibration, Maintenance, Repair: 1 hr

Site Prep,

Construction

Verification

Week Off

Local Excursions

Analysis

Distant Excursion

Analysis

Week Off

Distant Excursion

Analysis

Distant Excursion

Analysis

Week Off

Distant Excursion

Analysis

Distant Excursion

Analysis

Flare Retreat

Week Off

Distant Excursion

Analysis

Distant Excursion

Analysis

Week Off

Sys Shutdown

Departure Prep

Personal

14 hr

(total 67,200 hr)

Hr/Over

head

3 hr

(14,400 hr)

Production

7 hr

(33,600 hr total)

90 days

7 days

100 days

10 days

40 days

7 days

100 days

15 days

7 days

7 days

100 days

60 days
3-54

Figure 3-11 illustrates the surface outpost

configuration at the end of the second crew's

stay.

As before, the second crew will continue

with the general type of activities conducted

by the first crew: diverse observations by

robotic vehicles and human explorers,

collection of samples and their examination in

the outpost laboratory, and experiments

designed to gauge the ability of humans to

inhabit Mars. Specific crew activities will

build on the lessons learned and questions

generated by the first crew. Table 3-7 lists a

representative set of science and exploration

equipment that will be delivered as part of

the cargo on Flight 8. Note in particular that

this manifest contains a drill designed to

reach depths of 1 kilometer. (The deep drilling

operation must be consistent with planetary

protection protocols.) This tool will be used to

gather subsurface core samples that will help

reconstruct the geologic history of Mars, and

to try to locate subsurface deposits of water in

either liquid or solid form. Such a discovery

will substantially enhance the habitability

prospects for future crews by possibly

upgrading propulsion systems to the use of

hydrogen and oxygen and expanding

agricultural activities.

The second crew will repeat the activities

of the first crew in preparing themselves, the

ascent vehicle, and the surface habitat for a

departure from Mars during December 2013.

The third crew will already be in transit to

in accordance with the protocols in effect at

the time. The crew’s re-adaptation to a 1-g

environment will be monitored in detail to

learn more about how the human body

adapts to the varying gravity conditions and

to better prepare for the return of subsequent

crews.

3.5.4.3 Third Mission: Second Flight Crew,

2011 Opportunity

In the third opportunity opening in

December 2011, two additional cargo

missions and the second crew mission will be

launched. As in the second opportunity, all

assets previously delivered to Mars are

checked out and the MAV is verified to be

fully fueled. Any non-mission-critical

maintenance items identified by the first crew

or items noted prior to the departure of

Flights 7 through 9 are added to the spares

manifest and delivered with other surface

equipment. Table 3-6 lists the manifested

payloads for launch in the 2011 opportunity.

Prior to the arrival of the second crew, the

ISRU plants are producing not only the

propellants needed for the ascent vehicle, but

also water, oxygen, and buffer gases to serve

as an emergency cache for the life support

system. Teleoperated rovers are deployed on

extended traverses, perhaps to distances of

more than 100 kilometers, to take measurements, gather samples, and reconnoiter sites

for the human crew to investigate in more

detail.
3-55

Mars, again necessitating a debriefing of the

second crew, with participation by the third

crew, during the return to Earth. Once on

Earth, the second crew will likely benefit from

observations of the first crew, particularly in

the areas of modifications to the re-adaptation

regime and quarantine protocols.

3.5.4.4 Fourth Mission: Third Flight Crew,

2014 Opportunity

In the fourth opportunity opening in

March 2014, the final two cargo missions and

the third crew mission will be launched. As in

the second and third opportunities, all assets

previously delivered to Mars are checked out

and the MAV is verified to be fully fueled.

Any non-mission-critical maintenance items

identified by the first two crews or items

noted prior to the departure of Flights 10

through 12 are added to the spares manifest

and delivered with other surface equipment.

Table 3-8 lists the manifested payloads for

launch in the 2014 opportunity. As listed, the

manifests do not use the full cargo-carrying

Table 3-6 General Launch Manifest: 2011 Launch Opportunity

Flight 7: Cargo Flight 8: Cargo Flight 9: Second Crew

Surface Payload

• None • Ascent Capsule • Crew

• Empty Ascent Stage • Surface Habitat

• LOX/CH4 Production • Consumables

 Plant • Spares

• LH2 Propellant Seed • EVA Equipment

• Pressurized Rover • Science Equipment

• Science Equipment

• Additional Payload/

 Spares

Mars Orbit Payload

• Earth-Return Vehicle • None • None

• Fueled (LOX/CH4)

 TEI Stage

• Transit Habitat

• Earth-Return Capsule

Space Transportation Vehicles

• NTR Transfer Stage • NTR Transfer Stage • NTR Transfer Stage

• LOX/CH4 TEI Stage • LOX/CH4 Descent • LOX/CH4 Descent

 w/Mars Aerobrake Stage w/Mars Aerobrake Stage w/Mars Aerobrake

TEI: Trans Earth Injection LOX: liquid oxygen LH2: liquid hydrogen

NTR: Nuclear Thermal Rocket CH4: methane
3-56

Figure 3-11 Mars surface outpost at the end of second flight crew's stay.

MAV: Mars Ascent VehicleTROV: teleoperated rover

(unpressurized)

ROV: pressurized roverLSS: life support systemISRU: in-situ resource utilizationPVA: photo-voltaic array
3-57

capacity of the landers. The experience gained

by the first two crews will dictate any

additional equipment that can be used to

either upgrade existing equipment or add

new equipment to enhance the capabilities of

this outpost.

Prior to the arrival of the third crew, the

ISRU plants are again producing not only the

propellants needed for the ascent vehicle, but

also water, oxygen, and buffer gases to serve

as an emergency cache for the life support

system. Teleoperated rovers are again

deployed on extended traverses to take

measurements, gather samples, and

reconnoiter sites for the third crew to

investigate in greater detail.

Figure 3-12 illustrates the surface outpost

configuration at the end of the third crew's

stay. This represents the complete outpost

configuration as envisioned by the Mars

Study Team. With the facilities and

capabilities available at this stage, the surface

outpost will be able to support larger crews

for longer periods of time. The potential level

of self-sufficiency on Mars should also be

evident by this time, and a decision can be

made regarding any further use or expansion

of the outpost.

As before, the third crew will continue

with the general type of activities conducted

by the first and second crews: diverse

observations by robotic vehicles and human

explorers, collection of samples and their

examination in the outpost laboratory, and

experiments designed to gauge the ability of

humans to inhabit Mars. Specific crew

activities will build on the lessons learned

and questions generated by the first two

crews and should be focused on providing

information needed to determine the future

status of the outpost. Table 3-9 lists a

representative set of science and exploration

Table 3-7 Surface Science Payload for Second Flight Crew

Payload Description Payload Mass (kg)

Field Geology Package: geologic hand tools, cameras, 335

 sample containers, documentation tools

Geoscience lab instruments: microscopes, 125

 geochemical analysis equipment, camera

Exobiology laboratory: enclosures, microscopes, 50

 culture media

Biomedical laboratory 500

Plant and animal lab 500

Traverse geophysics instruments 400

Geophysics/meteorology instruments (8 sets) 200

1 kilometer drill 20,000

10-meter drill 260

Meteorology balloons 200

Discretionary PI science 600

Total 23,000
3-58

MAV: Mars Ascent VehicleTROV: teleoperated rover

(unpressurized)

ROV: pressurized roverLSS: life support systemISRU: in-situ resource utilizationPVA: photo-voltaic array

Nuclear Power Plant Nuclear Power Plant

Figure 3-12 Mars surface outpost at the end of third flight crew's stay.
3-59

equipment that will be delivered as part of

the cargo on Flight 11.

As with the first two crews, the third

crew will repeat those activities necessary to

prepare themselves, the ascent vehicle, and

the surface habitat for a departure from Mars

during January 2016.

3.5.4.5 Mission Summary

This section has illustrated a feasible

sequence of missions that can satisfy the

Reference Mission goals and objectives. These

missions use assumed hardware systems and

mission design principles to place the flight

crews in the martian environment for the

longest period of time at a satisfactory level of

risk. The major distinguishing characteristics

of the Reference Mission, compared to

previous concepts, include:

•No extended LEO operations, assembly,

or fueling

•No rendezvous in Mars orbit prior to

landing

Table 3-8 General Launch Manifest: 2014 Launch Opportunity

Flight 10: Cargo Flight 11: Cargo Flight 12: Third Crew

Surface Payload

• None • Ascent Capsule • Crew

• Empty Ascent Stage • Surface Habitat

• LOX/CH4

 Production • Consumables

 Plant • Spares

• LH2 Propellant Seed • EVA Equipment

• Science Equipment • Science Equipment

• Additional Payload/

 Spares

Mars Orbit Payload

• Earth-Return Vehicle • None • None

• Fueled (LOX/CH4)

 TEI Stage

• Transit Habitat

• Earth-Return Capsule

Space Transportation Vehicles

• NTR Transfer Stage • NTR Transfer Stage • NTR Transfer Stage

• LOX/CH4 TEI Stage • LOX/CH4 Descent • LOX/CH4 Descent

 w/Mars Aerobrake Stage w/Mars Aerobrake Stage w/Mars Aerobrake

TEI: Trans Earth Injection LOX: liquid oxygen LH2: liquid hydrogen

NTR: Nuclear Thermal Rocket CH4: methane
3-60

•Short transit times to and from Mars (180

days or less) and long surface stay-times

(500 to 600 days) for the first and all

subsequent crews exploring Mars

•A heavy-lift launch vehicle (HLLV),

capable of transporting either crew or

cargo direct to Mars, and capable of

delivering all needed payload with a

total of four launches for the first human

mission and three launches of cargo and

crew for each subsequent opportunity

•Exploitation of indigenous resources

from the beginning of the program, with

important performance benefits and

reduction of mission risk

•Availability of abort-to-Mars-surface

strategies, based on the robustness of the

Mars surface capabilities and the cost of

trajectory aborts

The characteristics of the hardware

systems used in these missions are more

completely discussed in the following

sections.

3.6 Systems

The following sections discuss the

characteristics and performance capabilities

of the various hardware elements needed for

the Reference Mission. The hardware

elements include a launch vehicle large

enough to place cargo bound for Mars into a

suitable Earth parking orbit, the

interplanetary transportation elements

necessary to move crew and equipment from

Earth to Mars and back, and the systems

needed to sustain the crew and perform the

proposed exploration activities on the martian

surface. Each section describes the principal

characteristics of the hardware system as

developed by the Mars Study Team.

Payload Description Payload Mass (kg)

Field Geology Package: geologic hand tools, cameras, 335

 sample containers, documentation tools

Geoscience lab instruments: microscopes, 125

 geochemical analysis equipment, camera

Exobiology laboratory: enclosures, microscopes, 50

 culture media

Plant and animal lab 500

Traverse geophysics instruments 400

Geophysics/meteorology instruments (8 sets) 200

Advanced Meteorology Laboratory 1000

10-meter drill 260

Meteorology balloons 200

Discretionary PI science 1000

Total 4070

Table 3-9 Surface Science Payload for Third Flight Crew
3-61

3.6.1 Operational Design

Considerations

Several operational factors related to

utilization, training, and repair influence the

design of hardware and software systems for

all vehicles. Early incorporation of these

factors into the vehicle design process will

enhance utility and functionality of the

systems, prevent costly workarounds late in

the development cycle, and maximize overall

mission success.

This section discusses some of the design

considerations identified as important in the

eventual detailed design and construction of

systems used for the Reference Mission.

While the system descriptions in the sections

that follow may not reach a level of detail that

reflects the specific topics mentioned here, the

design considerations should be considered

as guiding principles that should be used as

more detailed studies are performed.

A primary operational consideration in

system development is the subsequent ease

with which users, specifically crew members,

can become familiar with the system prior to

the mission. The more familiar crew members

are with vehicle hardware and software, the

less time will be spent on systems operations

and the more time will be available for

science and exploration activities. By the same

token, the more familiar technicians are with

the systems, the easier and less costly

production, maintenance, and repair will be

during the development process. To facilitate

this, all vehicles and systems need to use

common hardware and software where

applicable. System commonality in power

sources, interfaces, payload locker sizes, etc.,

among all vehicles will ease nominal

operational activities such as replacements,

reconfigurations, and hardware transfers.

Commonality will also help maintain

corporate knowledge bases and simplify crew

operations and repair procedures as

experience with one system can be applied to

many. The cost savings associated with the

use of common hardware and software

elements are obvious, and may be increased

by using as much off-the-shelf hardware as

possible. This, too, helps with familiarity as

crews and technicians may have previous

experience with similar systems. Repair

operations will also be simplified by requiring

a smaller set of standard tools for use by the

crew during mission execution.

The need for training facilities will have a

significant impact on vehicle design. Due to

the extended duration of the mission, training

facilities will be required on board crew

vehicles during various phases of the mission.

Trainers on Earth will need to match trainers

on vehicles which in turn will need to match

actual system performance. The requirement

for crew training facilities during various

mission phases will place additional

hardware and software design constraints on

the vehicles. Incorporation of training

facilities into appropriate vehicles is an

important operational factor influencing the

design process.
3-62

For both crew safety and operational

simplicity, system designs will require some

level of automatic fault detection for all lifecritical, mission-critical, and missiondiscretionary elements. For those elements

pertaining to crew safety and mission-critical

objectives, auto-fault detection and correction

should be incorporated into the design. Crew

action should not be required for life-critical

systems failures; backup system activation

should be automatic. Mission-critical system

failures should be as automated as possible,

leaving only the most complex tasks (such as

complete hardware replacement or repair) to

the crew. In addition, many of the routine, yet

important, system operations should be

automated to the greatest extent possible. For

example, an often overlooked aspect of

operations is consumables tracking and

forecasting for all life-critical and missioncritical systems. Crew time is better spent on

science activities than on tracking and

forecasting consumables such as propellant,

water, and breathable air. Many of these

functions are currently done for Space Shuttle

crews by flight controllers on the ground. Due

to the long delay time in communications

during the Reference Mission, maintenance of

this function by ground personnel is

impractical. Periodic verification of

consumables tracking activities by ground

personnel can validate the crew activities;

however, means by which the crew can

independently monitor and forecast

propulsive and nonpropulsive consumables

while not expending significant resources is a

necessity. Where cost effective, missiondiscretionary system failures can require

some crew response to enhance mission

objectives. A balance between the cost of

automation and crew time and training for

such activities will be needed. In general,

maximizing crew science time and

minimizing crew system maintenance and

operations throughout the mission will

improve overall mission success.

3.6.2 Launch Vehicles

The scale of the ETO launch capability is

fundamentally determined by the mass of the

payload that will be landed on the martian

surface. The nominal design mass for

individual packages to be landed on Mars in

the Reference Mission is 50 tonnes for a crew

habitat (sized for six people) which must be

transferred on a high-energy, fast-transit orbit.

This in turn scaled the required mass in LEO

to about 240 tonnes.

A number of different technologies could

be used to construct a single launch vehicle

capable of placing 240 tonnes into a 220-

nautical mile circular orbit. These launch

vehicle concepts used various combinations

of past, present, and future U.S. expendable

launch vehicle technology and existing launch

vehicle technology from Russia and Ukraine.

Table 3-10 summarizes some of the key

parameters for a representative set of the

vehicle options examined (Huber, 1993). Each

option is covered in more detail in the

following paragraphs.

Option 1 (Figure 3-13) illustrates the

capabilities possible through the use of
3-63

Energia and Zenit launch vehicle technology

combined with STS technology. All of the

engines used for this option are existing types

that have flown numerous times. The core

stage is assumed to be a modification of the

existing Energia stage. The modification

involves changing the vehicle from one that

uses a side-mounted payload container to an

in-line configuration with strap-on boosters

surrounding the core. The upper stage is a

new development using STS external tank

technology combined with a single SSME.

The shroud is entirely new and would be

sized for the largest of the Reference Mission

payloads. Note, however, that this

combination of largely existing components

does not meet the desired payload launch

mass.

Option 2 (Figure 3-14) illustrates what is

possible if a large launch vehicle makes

extensive use of existing STS and Russian

technology. The first stage core and upper

stage use the SSME, and the propellant tank

structure is based on the STS external tank.

Strap-on boosters for this vehicle use the

Russian RD-170 engine and a newly designed

propellant tank structure. Note that this

combination also does not meet the desired

payload launch mass.

Option Payload Mass (tonnes) to 220 Key Technology Assumptions

n.mi. Circular Orbit

1 179 Modified Energia core with eight Zenittype strap-on boosters. New upper stage

using a single Space Shuttle Main Engine

(SSME).

2 209 New core stage based on Space

Transportation System (STS) external tank

and SSMEs. Seven new strap-on boosters

each use a single RD-170 engine. New

upper stage using a single SSME.

3 226 New core stage based on STS external tank

and four of the new Space Transportation

Main Engines. Four strap-on boosters each

with a derivative of the F-1 engine used on

the first stage of the Saturn V. New upper

stage using a single SSME.

4 289 New vehicle using technology derived

from the Saturn V launch vehicle. Boosters

and first stage use a derivative of the F-1

engine, and the second stage uses a

derivative of the J-2 engine.

Table 3-10 Launch Vehicle Concepts for the Reference Mission
3-64

Figure 3-13 Mars Energia-derived HLLV with eight Zenit-type boosters.
3-65

Figure 3-14 STS External Tank-derived HLLV with seven LOX/RP boosters.
3-66

Option 3 (Figure 3-15) uses new and old

as well as existing technology to create a

vehicle that can deliver a payload that is

reasonably close to the desired value. The first

stage core propellant tank structure is based

on the STS external tank but uses newly

designed and as yet untested STME engines.

The strap-on boosters use an updated version

of the F-1 engine that powered the first stage

of the Saturn V in conjunction with newly

designed propellant tanks. The upper stage is

comparable to those discussed for the first

two options, using STS external tank

technology and a single SSME.

Option 4 (Figure 3-16) is indicative of a

launch vehicle that uses technology derived

from the Saturn V launch vehicle. The first

stage core is virtually identical to the first

stage of the Saturn V launch vehicle in its

basic size and its use of five F-1A engines.

Strapped to this stage are four boosters, each

with two F-1A engines and roughly one-third

of the propellant carried by the core stage.

The second stage uses six of the J-2 engines

that powered the second stage of the Saturn

V. However, this upper stage is considerably

larger than the Saturn second stage.

This last option was the largest of a

family of launch vehicles derived using

Saturn V launch vehicle technology. Figure

3-17 illustrates some of the other vehicle

configurations examined and provides

additional information on their capabilities.

All of these options can deliver a payload

almost as large as the stated need for 240

tonnes in a 220-nautical mile circular orbit.

Because a 240-ton-class launch vehicle

would be such a development cost issue,

consideration was given to the option of

launching several hardware elements to LEO

using smaller vehicles, assembling (attaching)

them in space, and then launching on the

outbound trajectory to Mars. This smaller

launch vehicle (with a 110- to 120-ton payload

capability) would have the advantage of more

modest development costs and is in the

envelope of capability demonstrated by the

unmodified U.S. Saturn V and Russian

Energia programs (Figure 3-18). However,

this smaller launch vehicle introduces several

potential difficulties to the Reference Mission

scenario. The most desirable implementation

using this smaller launch vehicle is to simply

dock the two elements in Earth orbit and

immediately depart for Mars. To avoid boiloff

losses in the departure stages (assumed to use

liquid hydrogen as the propellant), all

elements must be launched from Earth in

quick succession, placing a strain on existing

launch facilities and ground operations crews.

Assembling the Mars vehicles in orbit and

loading them with propellants just prior to

departure may alleviate the strain on launch

facilities, but the best Earth orbit for Mars

missions is different for each launch

opportunity, so a permanent construction

and/or propellant storage facility in a single

Earth orbit introduces additional constraints.

Several launch vehicle designs that could

provide this smaller payload capability using

existing or near-term technology were

examined. Figure 3-19 illustrates one possible
3-67

Figure 3-15 STS External Tank-derived HLLV with four strap-on boosters, each

having two F-1 engines.
3-68

Figure 3-16 Saturn V-derived Mars HLLV with F-1A/J-2S propulsion.
3-69

Figure 3-17 Saturn V-based Mars HLLV concepts.

2x2 F-1A Boost

5 F-1A Core

6 J-2S 2nd Stage

10 m

237 t

Vehicle Height (ft.)

400

VAB Height Limit - 410'

300

200

100

0

2x2 F-1A Boost

5 F-1A Core

6 J-2S 2nd Stage

13 m

228 t

2x2 F-1A Boost

5 F-1A Core

6 J-2S 2nd Stage

16 m

219 t

2x2 F-1A Boost

5 F-1A Core

6 J-2S 2nd Stage

17 m

285 t

2x2 F-1A Boost

5 F-1A Core

6 J-2S 2nd Stage

14 m

289 t

Shroud Diameter (Usable)

Payload to 220 nm Circular*

(Kickstage performs circ.)
3-70

Figure 3-18 Energia launch vehicle adapted to Mars mission profile.
3-71

320 ft

172 ft

89 ft

27.6 ft D

Side View Base View

Figure 3-19 Mars mission launch vehicle with two external tank boosters and

kick stage.
3-72

vehicle configuration and provides additional

information on its capabilities. This particular

option uses the STS external tank for its

propellant storage and main structure.

Engines for the core stage and the two strapon boosters were assumed to be the STME

engine that was under development at the

time of this study.

A 240-ton payload-class launch vehicle is

assumed for the Reference Mission. However,

it is beyond the experience base of any

spacefaring nation. While such a vehicle is

possible, it would require a significant

development effort for the launch vehicle,

launch facilities, and ground processing

facilities; and its cost represents a

considerable fraction of the total mission cost.

The choice of a launch vehicle remains an

unresolved issue for any Mars mission.

3.6.3 Interplanetary Transportation

The interplanetary transportation system

assembled for the Reference Mission consists

of seven major systems: a TMI stage, a

biconic aeroshell for Mars orbit capture and

Mars atmospheric entry, habitation systems

for the crew (both outbound and return), a

descent stage for landing on the surface, an

ascent stage for crew return to Mars orbit, an

ERV for departure from the Mars system, and

an ECCV (comparable to Apollo) for Earth

entry and landing. As mentioned earlier, the

Reference Mission splits the transportation of

people and equipment into cargo missions

and human missions, all of which are targeted

to the same locale on the surface and must be

landed in close proximity to one another. The

transportation strategy adopted in the

Reference Mission eliminates the need for

assembly or rendezvous in LEO of vehicle

elements and for rendezvous of a crew

transport vehicle with a Mars lander in Mars

orbit, both features of many previous mission

designs for Mars (NASA, 1989). But the

Reference Mission scenario does require a

rendezvous on the surface with previously

landed hardware elements and a rendezvous

in Mars orbit with the ERV as the crew leaves

Mars. The transportation strategy emphasized

the use of common elements wherever

possible to avoid development costs and to

provide operational simplicity.

3.6.3.1 Trans-Mars Injection Stage

A single TMI stage was developed for

both piloted and human missions. The stage

is designed for the more energetically

demanding 2009 human mission and is then

used in the minimum energy cargo missions

to launch the maximum payload possible to

Mars. Because of the energetic trajectories

used for human flights and the desire to

deliver large payloads to the martian surface,

nuclear thermal propulsion was selected for

this stage not only for its performance

advantages but also because of its advanced,

previously demonstrated state of technology

development, its operational flexibility, and

its inherent mission enhancements and crew

risk reduction (Borowski, et al., 1993).

After completion of two TMI burns

(required by the selected thrust-to-weight
3-73

ratio), the stage is disposed of by allowing it

to drift on a relatively stable interplanetary

trajectory. Calculations (Stancati and Collins,

1992) using the Planetary Encounter

Probability Analysis code indicate that the

probability of a collision of a nuclear engineequipped vehicle and the Earth is quite low.

The probabilities of a collision with Earth in

one millionyears are 3.8 percent for the

piloted TMI stages and 12 percent for the

cargo TMI stages.

The basic TMI stage is shown in Figure

3-20. For piloted missions, the TMI stage uses

four 15,000 lb. thrust NERVA* derivative

(ND) engines to deliver the crew and their

surface habitat/descent stage onto the transMars trajectory. Engines of this size are well

within the previous development history of

NERVA engines (Borowski, et al., 1993). This

version of the TMI stage incorporates a

shadow shield between the ND engine

assembly and the LH2

 tank to protect the crew

from radiation generated by the engines that

will have built up during the TMI burns. For

cargo missions, this transportation system can

deliver approximately 65 tonnes of useful

cargo to the surface of Mars or nearly 100

tonnes to Mars orbit (250 I 33,793 km) on a

single launch from Earth. The TMI stage for

cargo delivery requires only the use of three

ND engines. So for cost and performance

reasons, one ND engine and the shadow

shield are removed from this version of the

TMI stage.

The TMI stage adopted for the Reference

Mission could be designed around any of four

reactor options studied by the Team: (1)

Rocketdyne and Westinghouse NERVAderivative reactor (ND), (2) Pratt and Whitney

and Babcock and Wilcox (B&W) CERMET fast

reactor, (3) Aerojet and B&W particle bed

reactor and (4) Russian Energopool and B&W

engine concept using the “twisted ribbon”

ternary carbide fuel form. Work done in

Russia is especially promising, with the

possibility of higher Isp (approximately 950

seconds versus a 900-second demonstrated

capability by NERVA engines) at a thrust-toweight ratio of about 3.0 (for a 15,000 pound

thrust engine) being a possible development

target. The Reference Mission adopts the

more conservative ND engine concept, with a

projected Isp performance of 900 seconds.

Table 3-11 lists the mass estimates for the

various components of the TMI stage for

piloted and cargo versions. In both versions,

this stage is assumed to have a maximum

diameter of 10 meters and an overall length of

25.3 meters.

3.6.3.2 Biconic Aeroshell

On each cargo and piloted mission, Mars

orbit capture and the majority of the Mars

descent maneuver are performed using a

single biconic aeroshell. The decision to

perform the Mars orbit capture maneuver

From 1955 to 1973, the Nuclear Engine for Rocket

Vehicle Application (NERVA) program designed, built,

and tested a total of twenty rocket reactors. The

feasibility of using low molecular weight LH2 as both a

reactor coolant and propellant was convincingly

demonstrated.
3-74

Figure 3-20 Reference Mars cargo and piloted vehicles.

IMLEO Initial Mass to Low Earth Orbit

TEIS Trans Earth Injection Stage

2007 Cargo Mission 1

"Dry" Ascent Stage & Lander

2007 Cargo Mission 2

Hab Module & Lander

2007 Cargo Mission 3

LOX/CH4 TEIS & Hab

2009 Piloted Mission 1

Surface Hab with Crew and Lander

IMLEO = 216.6 t 216.6 t 204.7 t 212.1 t

* Expendable TMI Stage LH2 Tank (@ 18.2 m length) sized by 2009 Mars Piloted Mission

20.6 m*

4.7 m

10 m 10 m 10 m 10 m

86.0 t LH2

(@ 100%)

86.0 t LH2

(@ 100%)

86.0 t LH2

(@ 91.9%)

86.0 t LH2

(@ 100%)

15.0 m

16.3 m

19.0 m 7.6 m

16.3 m
3-75

using an aeroshell (that is, aerocapture) was

based on the fact that this option typically

requires less mass than an equivalent

propulsive capture stage (Cruz, 1979), and

aerodynamic shielding of some sort will be

required to perform the Mars descent

maneuver no matter what method is used to

capture into Mars orbit. Previous Mars

mission concepts employing aerocapture have

typically used more than one aeroshell to

deliver the crew to the surface. The use of two

aeroshells was driven by one or both of the

following factors. First, Mars entry speeds

may have been higher than those proposed

for the Reference Mission and therefore more

maneuverability and thermal protection were

required for this phase of the mission. Second,

the mission profile may have required a postaerocapture rendezvous in Mars orbit with

another space transportation element,

possibly delivered during the same launch

opportunity or during a previous

opportunity. Neither of these features is in the

Reference Mission. Thus, the strategy

employed was to develop a single family of

biconic aeroshells that can be used for both

Mars orbit capture and descent maneuvers.

Given the demands on a descent aeroshell of

the Mars entry and landing requirements, the

additional capability to permit aerocapture is

considered modest.

The aerodynamic maneuvering and

thermal protection requirements for the

aeroshells used in the Reference Mission were

studied in some detail (Huber, 1993). Based

on the studies, it was determined that a

biconic aeroshell with similar forward and aft

conic sections provided sufficient

maneuverability for the aerocapture and

entry phases of flight. Figure 3-21 illustrates

two of these aeroshells, one for the Mars

ascent vehicle and the other for the surface

habitat. For this family of aeroshells, the nose

section is a 25° half-angle cone ending in a

spherical cap. The skirt section is a 4° halfangle cone with a 10-meter diameter base.

The skirt section consists of two parts: a fixed

length aft section and a variable length center

section (“center” indicating its location

between the aft skirt and the nose section).

Table 3-11 Mass Estimates for TMI Stage Alternatives

TMI Stage Element Piloted Version Cargo Version

ND Engines (4 for piloted, 3 for cargo)

Radiation Shield

Tankage and Structure

LH2 Propellant (maximum)

Control System Tankage and Propellant

9.8

0.9

18.4

86.0

3.1

7.4

0.0

18.4

86.0

3.0

Total (tonnes) 118.2 114.8
3-76

Figure 3-21 Biconic aeroshell dimensions for Mars lander and surface habitat

modules.

Cg = center of gravity

Cp = center of pressure

14.9 (m)

6.0 (m)

8.9 (m)

7.7 (m)

to Cg

& Cp

Dia = 10.0 (m) Dia = 10.0 (m)

25 %

4 %

18 (m)

Reference Biconic: 10 (m) Dia by 15 (m)

length. I/D = 0.65 At 25° Angle of Attack

Extended Center Section Biconic

10 (m) Dia by 18 (m) length.
3-77

The length of the skirt center section is

determined by the size of the payload carried

within. Table 3-12 lists the overall lengths of

the various aeroshells used in the Reference

Mission.

Table 3-12 also lists an estimated mass for

the various aeroshells. The Mars Study Team

did not conduct a detailed study of the mass

of the various aeroshells used. Based on

previous studies of aerocapture vehicles, a

simple scaling factor of 15 percent of the entry

mass was used to determine the aeroshell

mass (Scott, et al., 1985). As more detail

regarding the aeroshell is developed,

variations in aeroshell mass will result caused

by differences in the amount of thermal

protection material used (some missions are

flown on faster trajectories and will encounter

higher entry speeds with correspondingly

higher heat loads) and in the size of the

aeroshell structure. At the present level of this

study, the simple scaling factor is considered

sufficient to estimate the aeroshell mass.

3.6.3.3 Transit/Surface Habitat

The crew is transported to Mars in a

habitat that is identical to the surface habitat/

laboratory deployed robotically on a previous

mission. Although a smaller habitat might

suffice for a crew of six during the

approximately 6 months of transit time,

designing the habitat so that it can be used

during transit and on the surface results in a

number of advantages to the overall mission.

Duplicating habitats on the surface provides

redundancy during the longest phase of the

mission and reduces the risk to the crew. By

landing in a fully functional habitat, the crew

does not have to transfer from a “space-only”

habitat to the surface habitat immediately

after landing, allowing them to re-adapt to a

gravity environment at their own pace. This

approach also allows the development of only

one habitat system instead of two or more

unique, specialized systems (although some

subsystems will have to be tailored for zero-g

operation). The performance of the transit

habitat may be tested by attaching a

development unit to the International Space

Station (Figure 3-22).

Each habitation element will consist of a

structural cylinder 7.5 meters in diameter and

4.6 meters long with two elliptical end caps

(overall length of 7.5 meters). The internal

Table 3-12 Mass and Size Estimates for Biconic Aeroshell Family

Aeroshell Payload Mass Estimate

(tonnes)

 Overall Length

(meters)

Ascent Stage and Lander

Surface Habitat and Lander

TEI Stage and Habitat

Surface Habitat with Crew and Lander

17.3

17.3

17.3

17.3

15.0

16.3

19.0

16.3
3-78

Figure 3-22 Transit habitat attached to International Space Station.
3-79

volume will be divided into two levels

oriented so that each “floor” will be a cylinder

7.5 meters in diameter and approximately 3

meters in height. The primary and secondary

structure, windows, hatches, docking

mechanisms, power distribution systems, life

support, environmental control, safety

features, stowage, waste management,

communications, airlock function and crew

egress routes will be identical to the other

habitation elements (the surface habitat/

laboratory and the Earth-return habitat). After

establishing these basic design features, there

exists an endless array of feasible internal

architecture designs. Deciding among feasible

internal designs involves a trade of resources

derived from a specific set of habitation goals.

At this level of detail, habitation goals are

somewhat subjective and open for discussion.

Figures 3-23, 3-24, and 3-25 illustrate one

internal arrangement for the transit/surface

habitat that was investigated for feasibility

and cost purposes.

The Mars transit/surface habitat will

contain the required consumables for the

Mars transit and surface duration of

approximately 800 days (approximately 180

days for transit and approximately 600 days

on the surface) as well as all the required

systems for the crew during the 180-day

transfer trip. Table 3-13 provides a breakdown

of the estimated masses for this particular

habitat.

Once on the surface of Mars, this transit/

surface habitat will be physically connected

with the previously landed surface laboratory,

doubling the usable pressurized volume (to

approximately 1,000 cubic meters) available

to the crew for the 600-day surface mission.

This configuration is illustrated in Figure 3-26

with the first of the transit habitats joined to

the previously landed surface habitat/

laboratory.

3.6.3.4 Mars Surface Lander

A single common descent stage was

developed for delivery of all hardware

systems (the habitats, ascent vehicle,

propellant production plant, and other

surface cargo) to the surface of Mars. The role

of this stage is to complete the descent-tolanding maneuver once the biconic aeroshell

ceases to be effective and to maneuver the

surface systems into the appropriate relative

position at the surface outpost.

The descent stage consists of four

subsystems: a basic structure to which all

other elements (including payload) are

attached, a parachute system to assist in

slowing the stage, a propulsion system to

slow the stage prior to landing, and a surface

mobility system.

The use of parachutes has been assumed

to help reduce the descent vehicle’s speed

after the aeroshell has ceased to be effective

and prior to the final propulsive maneuver

(Figure 3-27). Sufficient atmosphere is present

for parachutes to be more effective than an

equivalent mass of propellant.
3-80

Figure 3-24 EVA suit storage locations are critical in a robust crew safety system.

Figure 3-23 The crew exercise facility component of the countermeasures

system designed to inhibit crew degradation from exposure to reduced gravity

environments.
3-81

Figure 3-25 Conceptual Mars habitation module - wardroom design.
3-82

The propulsion system employs four

RL10-class engines modified to burn LOX/

CH4

 to perform the post-aerocapture

circularization burn and to perform the final

approximately 500 meters per second of

descent velocity change prior to landing on

the surface.

Once on the surface, the lander can move

limited distances to compensate for landing

dispersion errors and to move surface

elements into closer proximity. This allows,

for example, the surface laboratory to be

connected to the transit/surface habitats.

Mobility system power is provided by onboard regenerative fuel cells and from the

previously landed pressurized rover. Figure

3-28 illustrates one possible configuration for

this lander with its mobility system.

The descent lander is capable of placing

approximately 65 tonnes of cargo on the

surface. The dry mass of this lander is

approximately 4.7 tonnes, and it can carry

approximately 30 tonnes of propellant to be

used for orbital maneuvers and for the final

descent maneuver.

3.6.3.5 Mars Ascent Vehicle

When the surface mission has been

completed, the crew must rendezvous with

the orbiting ERV. This phase of the mission is

Table 3-13 Mars Transit/Surface Habitat Element

Subsystem Subsystem

Mass

(tonnes)

Consumables

Subtotal

(tonnes)

Dry Mass

Subtotal

(tonnes)

Physical/chemical life support

Plant growth

Crew accommodations

Health care

Structures

EVA

Electrical power distribution

Communications and information

 management

Thermal control

Power generation

Attitude control

Spares/growth/margin

Radiation shielding

Science

Crew

6.00

0.00

22.50

2.50

10.00

4.00

0.50

1.50

2.00

0.00

0.00

3.50

0.00

0.90

0.50

3.00

0.00

17.50

0.50

0.00

3.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.50

3.00

0.00

5.00

2.00

10.00

1.00

0.50

1.50

2.00

0.00

0.00

3.50

0.00

0.90

0.00

Total estimate 53.90 24.50 29.40
3-83

Figure 3-26 Habitat and surface laboratory joined on Mars surface.
3-84

Figure 3-27 Mars surface lander descending on parachutes.
3-85

Figure 3-28 Mars surface lander just prior to landing illustrating landing legs and

surface mobility system.
3-86

accomplished by the MAV which consists of

an ascent propulsion system and the crew

ascent capsule.

The MAV is delivered to the Mars surface

atop a cargo descent stage (Figure 3-29

illustrates the MAV inside the biconic

aeroshell and deployed on the surface). The

ascent propulsion system is delivered with its

propellant tanks empty. However, the same

descent stage also delivers a nuclear power

source, a propellant manufacturing plant

(both discussed in later sections), and several

tanks of hydrogen to be used as feedstock for

making the required ascent propellant. This

approach was chosen because the mass of the

power source, manufacturing plant, and seed

hydrogen is less than the mass of the

propellant required by the ascent stage to

reach orbit (Stancati, et al., 1979; Jacobs, et al.,

1991; Zubrin, et al., 1991). Not carrying this

propellant from Earth gave the Reference

Mission the flexibility to send more surface

equipment to Mars or to use smaller launch

vehicles or some combination of the two

options.

The crew rides into orbit in the crew

ascent capsule (Figure 3-30). This pressurized

vehicle can accommodate the crew of six,

their EVA suits, and the samples gathered

during the expedition and from experiments

conducted in the surface habitat/laboratory.

Life support systems are designed for the

relatively short flight to the waiting ERV. This

ascent capsule does not have a heat shield, as

it is not intended for reentering the

atmosphere of Earth or Mars. Once the

rendezvous has been completed and all crew,

equipment, and samples have been

transferred to the ERV, the MAV is jettisoned

and remains in orbit around Mars.

The MAV is depicted in Figure 3-31

showing basic dimensions for the vehicle. The

ascent propulsion system will require

approximately 26 tonnes of propellant to

accomplish the nearly 5,600 meters per

second of velocity change required for a

single-stage ascent to orbit and rendezvous

with the previously deployed ERV. The

structure and tankage needed for this

propellant and the other attached hardware

elements have a mass of 2.6 tonnes, including

the mass of the engines but not the crew

capsule. The ascent propulsion system uses

two RL10-class engines modified to burn

LOX/CH4

. These engines perform with an

average specific impulse of 379 seconds

throughout the MAV flight regime.

The ascent crew capsule has a maximum

diameter of 4 meters, a maximum height of

2.5 meters, and a mass of 2.8 tonnes. This

capsule contains the basic crew life support

systems and all guidance and navigation

equipment for the rendezvous with the ERV.

3.6.3.6 Earth-Return Vehicle

Returning the crew from Mars orbit to

Earth is accomplished by the ERV which is

composed of the TEI stage, the Earth-return

transit habitat, and the ECCV. The ERV is

delivered to Mars orbit with the TEI stage

fully fueled, and it loiters there for nearly 4

years before being used by the crew returning
3-87

Figure 3-29 Mars surface lander and biconic aeroshell.

Figure 3-30 Crew ascent capsule just after launch from Mars surface.
3-88

Figure 3-31 Methane/LOX ascent stage configuration.

9 (m)

6 (m)

4 (m)

One center (core)

3.6 (m) dia spherical

LO2 tanks

One center (core)

3.3 (m) dia spherical

LOH4 tanks
3-89

to Earth. For the return to Earth, the crew will

jettison the MAV and wait for the appropriate

departure time to leave the parking orbit.

During the 180-day return trip, the crew will

recondition themselves as much as possible

for the return to an Earth gravity

environment, train for those procedures they

will use during the entry phase, perform

science experiments and maintenance tasks,

and prepare reports. As they approach Earth,

the crew will transfer to the ECCV, along with

the samples they are returning, and separate

from the remainder of the ERV. The TEI stage

and the transit habitat will fly by Earth and

continue on into deep space. The crew in the

ECCV will deflect their trajectory slightly so

that they reenter the Earth’s atmosphere and

land on the surface.

The propulsion system for the ERV is

sized for the velocity change needed to move

the Earth return habitat and the ECCV from

the highly elliptical parking orbit at Mars to

the fast-transit return trajectory to Earth. As

with the TMI stage, the energetically

demanding 2011 return trajectory was used to

size this system for a 180-day return; less

energetically demanding returns could be

accomplished faster or with larger return

payloads.

Several propellant and engine

combinations were considered by the Mars

Study Team for the TEI propulsion system.

The two options given the most consideration

were liquid hydrogen with a NERVA

derivative engine comparable to the TMI

stage, and liquid oxygen/liquid methane

with the same engine used by the lander and

the MAV. With the 4-year loiter time in Mars

orbit, propellant boiloff was the major design

consideration. Liquid hydrogen would

require active refrigeration for this extended

period in orbit to avoid excessive boiloff

losses. Liquid oxygen/liquid methane boiloff

losses could be held to acceptable levels using

passive insulation and appropriate

orientation of the vehicle while in Mars orbit

(to minimize radiative heat input from Mars,

the largest source). The 30 kWe solar power

system (used primarily for powering the ERV

on the return to Earth) is also on board and

could be used for active cooling of these

propellants. Based primarily on this trade-off,

liquid oxygen and liquid methane were

chosen as the TEI stage propellants.

With this selection, the TEI propulsion

system uses two RL10-class engines modified

to burn LOX/CH4

. Again, these are the same

engines developed for the ascent and descent

stages, thereby reducing engine development

costs and improving maintainability. To

achieve the velocity change for the 2011 fasttransit return requires approximately 52

tonnes of liquid oxygen and liquid methane.

The remainder of the TEI propulsion system,

including tanks, structure, engines, and

reaction control systems, has a dry mass of

approximately 5.2 tonnes.

The return habitat is a duplicate of the

outbound transit/surface habitat used to go

to Mars but without the stores of consumables
3-90

in the surface habitat. As with the surface

habitats, the primary structure of this habitat

consists of a cylinder 7.5 meters in diameter

and 4.6 meters long with two elliptical end

caps (overall length of 7.5 meters). The

internal volume will be divided into two

levels, oriented so that each “floor” will be a

cylinder 7.5 meters in diameter and

approximately 3 meters in height. The

primary and secondary structure, windows,

hatches, docking mechanisms, power

distribution systems, life support,

environmental control, safety features,

stowage, waste management,

communications, airlock function and crew

egress routes will be identical to the other

habitation elements. Table 3-14 details the

mass estimate for this habitat module.

The ECCV is similar in concept to the

Apollo Command Module and is eventually

used by the crew to enter the Earth’s

atmosphere and deliver the crew to a safe

landing on land. The ECCV will have the

necessary heat shield for Earth reentry and

will be heavier than the ascent capsule

specialized only for that portion of the

mission. This vehicle has all of the life

support, guidance and navigation, and

propulsion systems to keep the crew alive for

several days and to maneuver the vehicle into

the proper entry trajectory. Once the reentry

phase has been completed, the ECCV will use

a steerable parafoil to land at a designated

location on the surface (Figure 3-32). The

ECCV has an estimated mass of 5.5 tonnes.

3.6.3.7 Interplanetary Transportation Power

Systems

A source of power will be required for all

of the interplanetary transportation systems

during the flight times to and, in the case of

the ERV, from Mars. While several alternatives

are available as a primary source of power for

these vehicles, solar energy is readily

available throughout these transit phases and

photovoltaic energy is a known technology.

Thus, a basic photovoltaic power capability is

assumed for those vehicles that are operating

in interplanetary space. A source of stored

power will also be needed for the

interplanetary vehicles during periods of

eclipse and of array retraction prior to capture

into Mars orbit, and for vehicles not typically

operating in interplanetary space (such as the

Mars surface lander, the MAV, and the ECCV).

During the eclipse periods and for the other

vehicles, a regenerative fuel cell (RFC) system

will be used to provide necessary power.

The most significant power requirements

for the interplanetary transportation system

come from the transit/surface habitat and the

ERV. Table 3-15 shows the estimated power

requirements to support the six-person crew

for both nominal and powerdown emergency

mode. The life support system is a major

constituent of the almost 30 kWe needed for

these two vehicles under nominal conditions.

The life support system is based on a partially

closed air and water system design that performs CO2

 reduction, O2 and N2 generation,

urine processing, and water processing

(potable and hygiene). The emergency mode
3-91

Figure 3-32 ECCV returning to Earth on a steerable parafoil.
3-92

value is based on the life support system

operating in an open loop mode with

reductions in noncritical operations.

The solar array as it would appear on the

ERV (Figure 3-33) is designed to produce the

required 30 kWe in Mars orbit at the worstcase distance from the Sun, 1.67 AU. The

energy storage system is sized to provide

power before and after Mars orbit capture as

well as during attitude control, array

retraction, orbit capture, array extension

maneuvers, and orbit eclipse. A nominal

power profile for these activities is shown in

Figure 3-34. It is currently assumed that the

outbound transit/surface habitat can be

safely powered down to 20 kWe during these

mission phases to save RFC mass and

volume, and that the RFC and solar array will

remain with the transit/surface habitat to be

used on the surface as a backup system.

Based on the size of the energy storage

system, eclipse power requirement, and

available power from the array, it will take

seven orbits of Mars to fully charge the RFC.

The RFC delivers power when the solar array

is retracted during entry, descent, and landing

of the transit/surface habitat. The RFC can

also deliver 20 kWe for 24 hours after landing,

Table 3-14 Earth-Return Habitat Element Mass Breakdown

Subsystem Subsystem

Mass

(tonnes)

Consumables

Subtotal

(tonnes)

Dry Mass

Subtotal

(tonnes)

Physical/chemical life support

Plant growth

Crew accommodations

Health care

Structures

EVA

Electrical power distribution

Communications and information

 management

Thermal control

Power generation

Attitude control

Spares/growth/margin

Radiation shielding

Science

Crew

6.00

0.00

22.50

2.50

10.00

4.00

0.50

1.50

2.00

0.00

0.00

3.50

0.00

0.90

0.50

3.00

0.00

17.50

0.50

0.00

3.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.50

3.00

0.00

5.00

2.00

10.00

1.00

0.50

1.50

2.00

0.00

0.00

3.50

0.00

0.90

0.00

Total estimate 53.90 24.50 29.40
3-93

and it will be the prime power source for the

transit/surface habitat and crew until the

habitat is moved to its final location and

connected to the main power grid. The RFC

could also provide power for moving the

habitat from the landing site to its final

emplacement location, assuming no solar

array deployment.

A duplicate of the solar array and RFC

system will be used on the ERV, saving

development costs for a unique system. All

other spacecraft discussed will use a subset of

the RFC system (assumed to be modular or at

least manufactured in smaller units) used in

the transit/surface habitat. The base power

load for vehicle avionics, communications,

and the propulsion system (noted as “S/C

Utility Power” in Table 3-15) is estimated at 5

kWe. This value is assumed as the power

requirement for the unmanned cargo-only

vehicles during the outbound transit.

Tables 3-16 and 3-17 show the mass

estimates for the two power systems

discussed: the 30 kWe system used for the

habitats and the 5 kWe system used for the

cargo flights. Both tables show the resulting

system characteristics if the RFCs must be

recharged over the course of one orbit versus

recharging them over seven orbits. The

savings in mass, volume, and array area are

obvious and support the choice to stay in

orbit for a longer period of time.

Table 3-15 Estimated Power Profile for Outbound and Return Transits

Element Mode Notes

Nominal Emergency

Life Support System (LSS) 12.00 8.00 Open Loop in Emergency

Thermal Contract System (TCS) 2.20 2.20 Mode

Galley 1.00 0.50 Emergency values

Logistic Module 1.80 1.80 Derated from nominal where

Airlock 0.60 0.10 appropriate

Communications 0.50 0.50

Personal Quarters 0.40 0.00

Command Center 0.50 0.50 Values adapted from NAS8-

Health Maintenance Facility (HMF) 1.70 0.00 37126, “Manned Mars System

Data Management System 1.90 0.80 Study

Audio/Video 0.40 0.10

Lab 0.70 0.00

Hygiene 0.70 0.00

SC/Utility Power 5.00 5.00

Total 29.40 19.50
3-94

Figure 3-33 Solar array power source for interplanetary spacecraft.
3-95

3.6.4 Surface Systems

The surface systems assembled to

support the long-duration science and

exploration activities of the Reference Mission

consist of six major systems: a surface

laboratory and habitat module, a

bioregenerative life support system, ISRU

equipment, surface mobility systems (rovers),

extravehicular mobility systems (EVA suits or

space suits), and power systems. All of these

systems, with the possible exception of the

EVA suits, are sent to Mars, landed on the

surface, deployed, and determined to be

functioning before departure of the flight

crew. This requires that each system be

developed with a high degree of built-in

autonomy and require support from the flight

crew or Earth-based supervisors only in

extreme situations where built-in capabilities

cannot cope.

3.6.4.1 Surface Habitat/Laboratory

The primary function of the Mars surface

habitat/laboratory is to support the scientific

and research activities of the surface crews.

The same structural cylinder (7.5 meters in

diameter, bi-level, and vertically oriented)

used for the other habitat elements was used

here, but it is more specialized for the

research activities. It will operate only in 3/8

gravity.

Figure 3-34 Nominal power profile for the transit/surface habitat.

NOTES:

Time axis was not drawn to scale

MO = Mars Orbit, period is 1 sol (Martian day = 25 hrs)

AD = Array Deployment (4 hr)

AR = Array Retraction (4 hr)

Descent (2hr)

Time

Power Level (kWe) 20

30

0 8 hr

180 days

Solar arrays

Batteries or RFC

Solar arrays and batteries

Transit from Earth Orbit 

to Mars Orbit

10 hr

1st Sol 2nd Sol

Max. orbit eclipse, 4.2 hr

AD

7th Sol

10.6 hr

AR

10.6 hr

6th Sol

MO

10
3-96

Table 3-16 30 kWe Power System With Fuel Cells and Solar Arrays

Power

System Type

1-Orbit

Recharge

7-Orbit

Recharge

Mass

(kg)

Volume

(m3

)

Array Area

(m2)

Mass

(kg) Volume (m3

) Array Area

(m2

)

Fuel Cell

Radiator

Array

1481

259

2971

0.194

3.260

N/A

N/A

47

918

1102

190

1682

3.83

1.5

N/A

N/A

35

520

Total 4711 3.454 965 2974 5.38 555

Table 3-17 5 kWe Power System With Fuel Cells and Solar Arrays

Power

System Type

1-Orbit

Recharge

7-Orbit

Recharge

Mass

(kg)

Volume

(m3

)

Array Area

(m2)

Mass

(kg) Volume (m3

) Array Area

(m2

)

Fuel Cell

Radiator

Array

398

76

795

9.498

0.971

N/A

N/A

14

246

347

49

431

0.456

0.653

N/A

N/A

9

138

Total 1269 1.469 260 827 1.109 147
3-97

This surface habitat/laboratory will be

one of the first elements landed on the surface

of Mars. Once moved to a suitable location

(should the actual landing site prove

unsuitable or to accommodate other

operational needs), this facility will be

connected to the surface power systems and

all internal subsystems will be activated. Only

after these internal subsystems and other

landed surface systems have been verified to

be operating satisfactorily will the first crew

be launched from Earth.

The surface habitat/laboratory contains a

large stowage area on the first level and the

second level is devoted entirely to the

primary science and research laboratory. The

stowage area will initially contain

nonperishable consumables that can be sent

to the surface prior to the arrival of the first

crew. As these consumables are used, this

space will become available for other uses—

likely to be plant growth and greenhousetype experiments. The other subsystems of

this module, such as the primary and

secondary structure, windows, hatches,

docking mechanisms, power distribution

systems, life support, environmental control,

safety features, stowage, waste management,

communications, airlock function, and crew

egress routes, will be identical to the other

habitats with a few exceptions. No crew

quarters or accommodations will be included

in this module except for a minimal galley

and minimal waste management facility.

However, the life support subsystem will be

capable of supporting the entire crew should

it become necessary for the crew to spend

extended periods of time in the habitat/

laboratory. The primary airlock for EVA

activities will be located in this module (with

backup capability in one of the other habitat

modules) with an EVA suit maintenance and

charging station located near the airlock.

Table 3-18 details the estimated mass for this

module.

3.6.4.2 Life Support System

An important reason for sending humans

to live on and explore Mars is to determine

whether human life is capable of surviving

and working productively there. The life

support system (LSS) for a Mars surface

mission will be an integral part of the mission

architecture, and must be viewed in terms of

its requirements to maintain the health and

safety of the crew and its capability to

minimize the dependence of a Mars outpost

on materials supplied from Earth. Proving

that human, and by extension animal and

plant, life can inhabit another world and

become self-sufficient and productive will be

a major objective of this LSS.

Four options were examined for use as

the LSS for the Mars surface facilities: open

loop, physical/chemical, bioregenerative, and

cached stocks of consumable materials.

•The open loop option is the simplest to

implement but typically the most expensive

in terms of the mass required. For this option,

life support materials are constantly

replenished from stored supplies as they are

used (for example, as air is breathed by the

crew, it is dumped overboard and replaced
3-98

with “new” air). While not seriously

considered, this option was carried for

comparison purposes.

•The physical/chemical option is typical

of the systems used in current spacecraft

and relies on a combination of physical

processes and chemical reactions to

scrub impurities from the air and water.

•The bioregenerative option uses higher

plant life species to provide food,

revitalize air, and purify water. This type

of approach is technically embodied in

the concept of a Controlled Ecological

Life Support System, although it is often

described colloquially as a “greenhouse

system.”

•The cached stocks option makes use of

the ISRU equipment already in place for

manufacturing propellants to also make

usable air and water for the crew. Trace

amounts of the constituents of usable air

and water will be by-products (in fact

impurities that must be removed) of the

propellant manufacturing process.

Capturing and storing these impurities

as well as oversizing some of the

Table 3-18 Mars Surface Habitat/Laboratory Mass Breakdown

Subsystem

Subsystem

Mass

(tonnes)

Consumables

Subtotal

(tonnes)

Dry Mass

Subtotal

(tonnes)

Physical/chemical life support

Plant growth

Crew accommodations

Health care

Structures

EVA

Electrical power distribution

Communications and information

 management

Thermal control

Power generation

Attitude control

Spares/growth/margin

Radiation shielding

Science

Crew

4.00

3.00

7.50

0.00

10.00

1.50

0.50

1.50

2.00

0.00

0.00

5.50

0.00

3.00

0.00

2.00

1.00

7.50

0.00

0.00

1.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Uncertain

0.00

2.00

2.00

0.00

0.00

10.00

0.50

0.50

1.50

2.00

0.00

0.00

5.00

0.00

3.00

0.00

Total estimate 38.50 11.50 27.00
3-99

production processes can allow the crew

to at least augment other elements of the

LSS.

Combinations and hybrids of these

options are also possible and were also

examined for this report. Using a combination

of systems or a hybrid system would provide

more levels of functional redundancy and

thus provide an attractive option for

enhancing the viability of the Mars surface

facilities as a safe haven. Figure 3-35

illustrates a hybrid system using physical/

chemical and bioregenerative elements.

In this example, certain life support

functions, such as CO2 reduction and water

purification, can be shared by both elements,

while other functions, such as fresh food

production, can only come from the

greenhouse. As an integrated system, neither

element needs to provide 100 percent of the

full life support demand on a continuous

basis. Both elements however, should be

capable of being periodically throttled to

satisfy from 0 percent to 100 percent of the

LSS load.

The Reference Mission adopted the

philosophy that life-critical systems (those

systems absolutely essential to ensure the

crew’s survival) should have two backup

levels of functional redundancy. That is, if the

first two levels fail, the crew will not be in

jeopardy, but will not be able to complete all

mission objectives. As previously discussed,

each habitat is equipped with a physical/

chemical LSS capable of providing for the

entire crew for the duration of their surface

stay. A physical/chemical system was chosen

due to the mature nature of the technology.

Thus, the first habitat and the surface

laboratory constitute the primary and first

backup (although not strictly a functional but

rather a redundant backup) for the crew life

support.

It is highly desirable for the second

backup to use indigenous resources so that

the backup life support objective and the live

off the land objective are both met. Table 3-19

compares the various options for the

combined LSSs with an open system. Each of

these options was sized for a crew of six

spending 600 days on the martian surface.

Because of the life-critical nature of the

propellant manufacturing facility and the

high level of reliability that must be designed

into this system, the cached stocks option was

chosen as the second backup. However,

demonstrating the capability to produce

foodstuffs and revitalize air and water using

bioregenerative processes is considered a

mission-critical objective for the Reference

Mission. For that reason, an experimental

bioregenerative life support system capable of

producing a small amount of food is included

as a science payload to be delivered for use by

the second crew.

Several options exist for the location of

the experimental bioregenerative LSS. One is

to use the storage space in the surface

habitat/laboratory that will become available

as consumables are used. This is the simplest

to implement but would require artificial

lighting and would be restricted to the
3-100

Figure 3-35 Hybrid LSS process distribution.

SUPPLY

HIGHWAY

LSS

WASTE

PRODUCT

HIGHWAY

DISPOSAL

PATH

RECYCLE

PATH

PHYS. / CHEM. BIO-REGEN.

MASS CO2 H2O CO2

H2O O2 O2

ELECT.

POWER

HIGHWAY

EFFL.

BUS

INFL.

BUS

H2O FOOD

H2O

H2O

O2

CO2

Table 3-19 LSS Mass, Volume, Power Comparison.

Architecture

Functional

Redundant

Levels

Mass

(mt)

Volume

(m^3)

Maximum ∆

Power Over

Open Loop (kW)

Open Loop 1 180 290 0

Physical/Chemical with Cached

Stocks 2 60 470 7

Bioregenerative with Cached

Stocks 2 60 410 60

Hybrid Physical/Chemical and

Bioregenerative with Cached

Stocks

3 80 600 60
3-101

volume available in the storage area. Two

other options involve attaching an external

pressurized structure to one of the habitat

modules. One external option would use a

hard opaque structure for the external shell

and would also require artificial lighting. The

other external option would use an inflatable

transparent structure for the external shell.

Natural sunlight would be used to illuminate

the plants which would reduce the power

needed by the system; however, the potential

risk of a puncture due to natural or humanderived events would be increased.

In either external scheme, the greenhouse

atmospheric volumes would normally

communicate directly with the atmospheric

volume of the habitat without further

processing, but could be sealed off in

contingencies. The greenhouse(s) could be

erected or inflated at the convenience of the

crew. The loss of a greenhouse module for

any reason, such as puncture, mechanical or

electrical failure, or loss of shielding integrity,

would not seriously impact overall mission

success.

3.6.4.3 In Situ Resource Utilization

ISRU for the Reference Mission provides

two basic resources: propellants for the MAV

and cached reserves for the LSSs. Using

indigenous resources to satisfy these needs

instead of transporting resources from Earth

reduces launch mass and thus mission cost.

ISRU production for the Reference Mission

includes two virtually redundant ISRU plants,

the first delivered before the initial piloted

mission and the second delivered prior to the

first follow-up mission. Each ISRU plant will

produce propellants for at least two MAV

missions. However, only the first plant is

required to produce life support caches.

For each MAV mission, a plant is

required to produce 20 tonnes of oxygen and

methane propellants at a 3.5 to 1 ratio: Each

plant must produce 5.8 tonnes of methane

and 20.2 tonnes of oxygen. Further, the first

ISRU system is required to produce 23.2

tonnes of water, 4.5 tonnes of breathing

oxygen, and 3.9 tonnes of nitrogen/argon

inert buffer gasses for use by any of the three

Mars crews. The system liquefies and stores

all of these materials as redundant life

support reserves or for later use by the MAV.

The approach to ISRU production uses

the martian atmosphere for feedstock and

imports hydrogen from Earth. The main

processes used are common to both ISRU

plants. The significant difference between the

two is that the second plant is smaller and

excludes equipment for buffer gas extraction.

Should sources of indigenous and readily

available water be found, this system could be

simplified.

3.6.4.3.1 Processes

The Mars atmosphere, which is used as a

feedstock resource, is composed primarily of

carbon dioxide with just over 3 percent

nitrogen and argon. The ISRU plants must be

capable of converting the carbon dioxide to

methane, oxygen, and water. Since hydrogen

is not substantially present in the atmosphere

in gaseous form and indigenous sources of
3-102

water are uncertain, hydrogen must be

imported from Earth. The first plant must also

be capable of extracting the nitrogen and

argon for buffer gas reserves. The reference

ISRU system uses Sabatier, water electrolysis,

carbon dioxide electrolysis, and buffer gas

absorption processes to achieve these ends.

•Methane production - The Sabatier

reaction was discovered by French

chemist P. Sabatier in the nineteenth

century and is one of the most often

cited for ISRU on Mars (Sullivan, et al.,

1995). The reaction converts carbon to

methane and water by reacting it with

imported hydrogen at elevated

temperatures. This process is also

commonly used in closed physical/

chemical LSSs for reduction of metabolic

carbon dioxide. It results in a water to

methane mass ratio of 2.25:1 and

requires 0.5 tonnes of hydrogen for each

tonne of methane produced. The

resultant methane is stored cryogenically

as fuel. The water can either be used

directly as cached life support reserves

or can be broken down into oxygen and

hydrogen to be recycled.

•Oxygen production - Oxygen production

is accomplished with two different

processes. The Reference Mission uses

both water electrolysis to produce

oxygen from water produced in the

plant and carbon dioxide electrolysis to

directly convert the Mars atmosphere to

oxygen.

Water electrolysis is well known and has

been used for numerous terrestrial

applications for many years. The combined

Sabatier and electrolysis processes generate

oxygen and methane for use as propellants at

a mass ratio of 2:1. In this combined process

case, the hydrogen is recycled into the

Sabatier process so that 0.25 tonnes of

hydrogen are needed for each tonne of

methane. The engines selected for the

Reference Mission use oxygen and methane at

a mass ratio of 3.5 to 1. Therefore, an

additional source of oxygen is needed to

avoid overproduction of methane.

The carbon dioxide electrolysis process is

used in the Reference Mission to provide the

needed additional oxygen. The process

converts the atmospheric carbon dioxide

directly into oxygen and carbon monoxide

using zirconia cells at high temperature. The

zirconia cell system is not as well developed

as the Sabatier process but is under

development (Sridhar, et al., 1991; Ramohalli,

et al., 1989; and Colvin, et al., 1991). This

process eliminates the overproduction of

methane during propellant production except

during the first mission when the Sabatierproduced water is also needed.

The two strong alternatives to carbon

dioxide electrolysis—methane pyrolysis and

reverse water gas shift—were not studied indepth for the Reference Mission report, but

they should be considered seriously in further

studies of manned Mars missions.
3-103

•Buffer gas extraction - The buffer gas

extraction process has not been

examined in detail during this study. It

will most likely be a nitrogen and argon

absorption process in which compressed

atmosphere is passed over a bed of

material which absorbs the nitrogen and

argon. The gases are then released by

heating the bed and the products are

passed on to the cooling and storage

system. Parallel chambers are used so

that one bed is absorbing in the presence

of atmosphere while the other is

releasing its captured gases.

•Ancillary Systems - Systems for

atmosphere intake, product liquefaction,

and product storage and transfer will be

needed. These systems have not been

detailed for the Reference Mission at this

stage of study but their necessary

functions can be described. The filter

and compressor equipment cleans the

martian atmosphere of dust and

compresses it to a pressure usable by the

rest of the ISRU plant. Product

liquefaction must include cryogenic

liquefaction of oxygen, methane and

nitrogen as well as condensation of the

water stored as cached reserves. Storage

systems will include cryogenic tanks for

cached oxygen and buffer gasses. An

expandable bladder-type tank is

anticipated for cached water. Propellant

storage will be accomplished in the MAV

tanks and so is not considered part of the

ISRU system.

3.6.4.3.2 Initial ISRU Plant

The first ISRU plant is delivered to Mars

over a year prior to the first departure of

humans from Earth, and during that year the

plant produces all the propellants and life

support caches that will be needed. Thus,

humans do not even leave Earth until

reserves and return propellants are available.

This plant also produces propellants for the

MAV mission of the third crew in the overall

Reference Mission scenario.

A schematic of this initial plant is shown

in Figure 3-36. The plant integrates all the

processes needed for both propellant and life

support products. The water electrolyzer is

not used in the plant during the first period of

operation. Because of the total mass of the

water cache, all of the water produced by the

Sabatier reactor is stored and the carbon

dioxide electrolysis reactor is responsible for

producing all the oxygen needed. In addition,

over 10 tonnes of excess methane are

produced as a by-product of the water

production process for the LSS cache.

When the plant is operated for the third

MAV launch propellants, the water

electrolyzer is brought on-line. Instead of

being condensed, the water from the Sabatier

reactor is split by the electrolyzer into

hydrogen (which is recycled to the Sabatier

reactor) and oxygen (which is liquefied and

sent to the MAV tanks). For this operation of

the plant, no methane overproduction is

needed.
3-104

The size of the ISRU plant has only been

estimated parametrically. These estimates are

based on some previous work on the options

for ISRU and on the rates needed to produce

requisite materials over a 15-month period.

The mass and power requirements for this

plant are given in Table 3-20. The power

requirements represent those of the plant’s

initial period of operation.

3.6.4.3.3 Second ISRU Plant

The second ISRU plant is delivered at

essentially the same time as the arrival of the

first crew on Mars. This allows time for

propellant production prior to the Earth

departure of the second crew. The second

plant is only charged with production of

propellants since, the life support reserves are

presumably still present.

H2O (trace)

H20

Filter/

Compressor

Buffer Gas Extraction

Sabatier

Buffer gas

storage cache

O2 O2

CH4

Water Storage

Cache

CO2 Electrolysis

Water

Condenser

CO2

CH4

O2

Breathing

O2 Storage

Cache

H2

Mars

Atmosphere

N2/Ar

H2

NC

NC

NC

Water Electrolysis

O2(trace)

Buffer Gas

Cryo Cooler

CH4

Vent

CH4

CO

Vent

MAV

First

Stage

MAV

Second

Stage

Cryo Cooler

Figure 3-36 Schematic of the first ISRU plant.
3-105

The plant schematic is essentially the

same as that shown in Figure 3-36. The

second plant does not include the buffer gas

extraction, liquefaction, and storage

equipment or the water condensation and

storage equipment. Further, the size of the

reactors is reduced because of the lower

production rates needed. Table 3-21 shows the

estimated mass and power requirements for

this plant. Plant operations are the same as

those of the first plant during its second

period: All Sabatier-produced water is

electrolyzed, and the extra oxygen needed is

produced by the carbon dioxide electrolyzer.

3.6.4.4 Surface Mobility

Mobility on a local scale and regional

scale will be required during all phases of the

surface exploration of the Reference Mission.

The basic objectives for the Reference Mission

require that a variety of mobility systems be

provided for basic maintenance and

operations activities as well as for exploration

of the surface. Prior to the first crew’s arrival

and during all subsequent periods whether a

crew is present or not, exploration at short

and long ranges will be performed by

automated rovers. Surface facility setup

activities will require rovers acting under the

supervision of Earth-based operators.

Maintenance and operations by the surface

crews can be more productive with the

availability of mobile utility systems. And

finally, long-range, long-duration exploration

by the surface crews will be possible only

with the use of pressurized, autonomous

rovers.

The Reference Mission identifies three

classes of mobility systems, based on the time

and distance to be spent away from the

surface habitats.

Table 3-20 Mass and Power Estimates for the First ISRU Plant

Plant Component Production Rate

(per day)

Component Mass

(kg)

Component Power

(kWe)

Compressor 269.7 kg 716 4.09

CO2

 Electrolysis 53.2 kg 2128 63.31

Sabatier 22.9 kg 504 1.15

H2

O Electrolysis 27.8 kg 778 0.00

Buffer Gas Extraction 8.7 kg 23 0.13

Cryogenic Coolers 84.8 kg 653 3.59
3-106

•Immediate vicinity of the surface base

facilities: hundreds of meters and the 6-

to 8-hour limit of the EVA portable LSS

•Local vicinity of the surface base facility:

several kilometers and the 6- to 8-hour

limit of the EVA portable LSS

•Regional distances: a radius of up to 500

km in exploration sorties that allow 10

workdays to be spent at a particular

remote site, and with a transit speed

such that less than half of the excursion

time is used for travel (for example, for

10 workdays, no more than 5 days to

reach the site and 5 days to return).

These divisions resulted in three basic

rover types and a number of other mobility

systems to support the kinds of activities at

these ranges and for these amounts of time.

On the local scale, any time the crew is

outside of the habitat(s) they will be in EVA

suits and will be able to operate at some

distance from the habitat. The maximum

distance will be determined by their

capability to walk back to the outpost within

the time set by the recharge limits of the

portable LSS. During these activities, the EVA

crew will have a variety of tools, including

rovers, carts, and wagons, available for use.

For distances perhaps beyond a kilometer

from the habitats but less than 10 kilometers

distant, exploration will be assisted by

unpressurized self-propelled rovers. This

rover is functionally the same as the Lunar

Rover Vehicle used in the Apollo Program

and is meant to assist the EVA crews by

transporting them and their equipment over

relatively short distances. Figure 3-37

illustrates one concept for this rover (partially

hidden behind one of the teleoperated longrange rovers) with a gabled radiator above

the aft end. This rover is driven by six coneshaped wheels and has an estimated mass of

4.4 tonnes. Three of these vehicles will be part

of the cargo carried to the surface for use in

and around the surface facilities.

Plant Component Production Rate

(per day)

Component Mass

(kg)

Component Power

(kWe)

Compressor 87.8 kg atm 233 1.33

CO2

 Electrolysis 18.5 kg O2 740 22.00

Sabatier 12.4 kg CH4 272 0.62

H2

O Electrolysis 27.8 kg H2O 778 5.79

Cryogenic Coolers 30.8 kg 238 2.3

Table 3-21 Mass and Power Estimates for the Second ISRU Plant
3-107

On the regional scale, beyond the safe

range for exploration on foot or in

unpressurized rovers, crews will explore in

pressurized rovers, allowing them to operate

for the most part in a shirtsleeve

environment. Figure 3-38 illustrates one

possible concept for this rover. The rover is

assumed to have a nominal crew of two

people, but can carry four in an emergency.

Normally, the rover would be maneuvered

and EVAs would be conducted only during

daylight hours, but sufficient power will be

available to conduct selected investigations at

night. Crew accommodations inside the rover

will be relatively simple: a drive station, a

work station, hygiene facilities, a galley, and

sleep facilities. An airlock on this rover will be

capable of allowing not only surface access

for an EVA crew, but also direct connection to

the habitat, thus precluding the need for an

EVA to transfer either to or from the rover.

Each day on an excursion away from the

main surface facilities, the rover has the

capability of supporting up to 16 personhours of EVAs. Facilities for recharging the

portable LSSs and for making minor repairs

to the EVA suits are also included. The work

station will be used, in part, to operate two

mechanical arms that can be used to

manipulate objects outside the rover without

leaving the pressurized environment. These

arms, along with other mobility subsystems,

can also be operated remotely by Earth-based

personnel. This feature is required to allow

many of the deployment, setup, and

monitoring activities to be carried out prior to

the arrival of the first crew. A final feature of

this rover is the power system. The choice of

the specific power system is discussed in a

later section. However, this system will be

mounted on a separate trailer to be towed by

the rover whenever it is in operation. At times

when the rover is dormant, the power trailer

can be used for other purposes, including its

use as a backup power source for any of the

surface facilities. Two pressurized rovers will

be carried to the surface. This allows for

redundancy in this function, including the

possibility of rescuing the crew from a

disabled rover located at a distance from the

habitats. Each rover is driven by four coneshaped wheels and is estimated to have a

mass of 16.5 tonnes.

Exploration at a regional scale will also

be undertaken by small teleoperated rovers.

The foreground of Figure 3-38 illustrates one

possible concept for this rover. The main

purpose for these rovers is to explore the

martian surface at long distances, hundreds to

thousands of kilometers, from the habitats.

The activities carried out by this type of rover

will be to conduct scientific investigations,

collect and return samples to the habitats, and

scout possible locations for human crews to

investigate in more detail. Three of these

rovers will be delivered as part of the first

cargo mission and will be supervised from

Earth during the time between landing and

the arrival of the first crew. Determining sites

for the crews to investigate and safe routes to

the sites will be the primary activity before

the first crew arrives and during those

periods when no crew is at the surface base.

When a crew is on the martian surface, these
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Figure 3-37 Concepts for the unpressurized and automated surface rovers.
3-109

Figure 3-38 Concept for the large pressurized surface rover.
3-110

rovers will be available for teleoperation by

the crews. Focused exploration, sample

collection, and scientific measurements will

be the main tasks for these rovers while under

the control of the surface crew, who will be

able to operate these rovers from the

shirtsleeve environment of the surface

habitat/laboratory. Each rover is estimated to

have a mass of 440 kilograms.

This range of mobility systems will allow

exploration activities to be carried out

continuously once the first cargo mission has

delivered its payload to the martian surface.

The variety of range requirements and surface

activities leads to a suite of mobility systems

that have overlapping capabilities.

3.6.4.5 EVA Systems

The ability for individual crew members

to move around and conduct useful tasks

outside the pressurized habitats will be a

necessary capability for the Reference

Mission. EVA tasks will consist of

constructing and maintaining the surface

facilities, and conducting a scientific

exploration program encompassing geologic

field work, sample collection, and

deployment, operation, and maintenance of

instruments. EVA systems provide a primary

operational element and a critical component

of the crew safety system and must be

integrated into the design of a habitation

system during the very early stages. Two

systems will make EVA possible for the crews:

an EVA suit designed for use in the martian

environment and an airlock system that will

allow the crew to safely exit and enter the

pressurized habitats.

The EVA system will have the critical

functional elements of a pressure shell,

atmospheric and thermal control,

communications, monitoring and display, and

nourishment and hygiene. Balancing the

desire for high mobility and dexterity against

accumulated risk to the explorer will be a

major design requirement on a Mars EVA

system. Lightweight and ease of maintenance

will also contribute to the design. Specific

concepts for an EVA suit that will satisfy these

requirements were not investigated in this

study. Further effort will be required to

translate these general needs into specific

requirements and an actual implementation.

The airlock system, although integral

with the habitation system, was developed as

an independent element capable of being

“plugged” or relocated as the mission

requires. Because EVA will be a substantial

element of any planetary surface mission, the

design and location of the associated airlock

facilities will have a major impact on the

internal architecture of each pressurized

element.

A conceptual airlock configuration was

prepared (Figure 3-39). In the foreground of

this conceptual design is an airlock sized for

two suited crew members. In the rear of the

illustration is a facility for EVA suit

maintenance and consumables servicing.

Each habitat will have an airlock located

within it. The maintenance and consumables
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servicing facility will be located in the surface

habitat/laboratory.

3.6.4.6 Surface Power Systems

A source of power will be required for a

number of diverse systems operating on the

surface of Mars. A large fixed power source is

required to support the propellant

manufacturing facility and the surface

habitats. A mobile source of power is required

to support the three categories of rovers that

will move crew and scientific instruments

across the martian surface. Various power

system options were reviewed for their

appropriateness to meet mission

requirements and guidelines for these surface

systems. Contending power system

technologies include solar, nuclear, isotopic,

electrochemical, and chemical for both the

fixed and mobile power source.

While all surface element power system

requirements were assessed for application

synergies that would suggest common

hardware (duplicates of the same or similar

design) or multiuse (reuse system in a

different application or location) wherever

prudent, the specific requirements for the

fixed and mobile power sources were

examined individually.

3.6.4.6.1 Fixed Surface Power Systems

To best determine the type and design of

the fixed power system, an estimated power

profile was developed and is shown in Figure

3-40.

The power system must be one of the

first elements deployed because it provides

power to produce the life support cache and

ascent vehicle propellants prior to the launch

of the first crew. Approximately 370 days will

be available to produce the required life

support cache and ascent propellant.

However, this will be reduced by the time to

deploy the power system. With an estimated

power system deployment time of 30 to 60

days, about 320 days remain for producing

these products. An initial 60 kWe power level

was determined by this required deployment

time and the energy required to produce the

life support cache and ascent vehicle

propellants during the time remaining. As the

outpost reaches full maturity, power levels

approach 160 kWe due to increased habitation

volumes and life support capability.

Significant design requirements are also

placed on all the surface equipment delivered

on the initial cargo flights. Each system must

be deployed to its respective locations and

Figure 3-39 Conceptual airlock and

EVA suit maintenance facility.
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Figure 3-40 Mars surface power profile.

function autonomously for almost 2 years.

Crew safety and well-being demands

reliability and robustness in all surface

elements. (Part of this risk is mitigated by

backup and redundant systems or systems

that can perform multiple functions.) These

requirements all impact the design and

selection of the power system for the central

base.

To meet the evolutionary power

requirements of the base, two types of power

systems were evaluated: nuclear and solar.

Table 3-22 shows estimated mass, volume,

and area for each of these options.

The power management, transmission,

and distribution system masses (at 95 percent

efficiency) have been included in each of the

system sizing estimates. Transmission cable

masses were calculated using 500 volts due to

the Paschen breakdown limit associated with

Mars’ atmospheric pressure. (For a wide

range of conditions, exposed conductors at an

electrical potential greater than 500 volts

could experience large power drains due to

atmospheric discharges.)

Due to the potential radiation hazard of a

nuclear power source, the nuclear power

system is configured with a completely

175

150

125

100

75

50

25

P

o

w

e

r

kWe

1 2 34 56 7

Years After First Cargo Landing
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enveloping shield for remote deployment and

is integrated with a mobile platform. The

entire system is deployed from the landing

site (trailing distribution cables) to a site at

least 1 kilometer from the base. It is planned

to use one of the rovers for this task. Power

from the rover will be used to start up the

power system, deploy radiators, and obtain

operating conditions. All of these activities

will be supervised remotely by personnel on

Earth and will be performed in a manner that

will minimize the risk to this critical piece of

equipment. The first nuclear power system

will be capable of delivering the full base

needs of 160 kWe. A second system is

delivered during the first opportunity and is

deployed to satisfy the fail-operational

mission requirement, but it will not be turned

on unless required.

The second option, a solar power system,

requires array panels to supply the main base

load and recharge the energy storage for

nighttime operations. The primary 120 kWe

system was sized to produce required power

during winter diurnal cycles at the equator.

The backup habitat power system was

designed to operate at worst-case global dust

storm conditions, characterized by an optical

depth (O.D.) equal to 6.0, since these

conditions could be present at the base when

an emergency power situation arose. Under

nominal conditions, these two systems were

assumed to be operating in unison to provide

the maximum 160 kWe required for the

Table 3-22 Characteristics for Fixed Surface Power System Options

O.D. - optical depth

Main Power

System (kWe)

Type Mass

(MT)

Volume

(m3) Area (m2

)

160

NUCLEARSP-100 type, low-temp, stainless

steel, dynamic conversion, 4-Pi

shielding

14 42

321 radiator area

120 SOLAR - tracking,

O.D. = 0.4 19.6 341 6,400 array area

45,000 field area

SOLAR - nontracking,

O.D. = 0.4

33.5 686 13,000 array area

39,000 field area

Backup 40 SOLAR - tracking,

O.D. = 6.0 14 390 7,600 array area53,000 field area

SOLAR - nontracking,

O.D. = 6.0

26 816 16,000 array area

48,000 field area

Emergency Use Pressurized Rover Power System (See Table 3-21)
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mature base. The ISRU plant was not

considered a life-critical function so the

power system was designed to produce full

power at an O.D. of 0.4 or a clear Mars sky.

Both sun tracking and nontracking arrays

were evaluated. The solar tracking array total

land area is greater that the nontracking

because of the required panel spacing needed

to eliminate shadows from one panel upon

the other.

O.D., or the intensity of the solar

radiation reaching the surface of Mars, has a

significant impact on system size and mass.

For example, if the entire 160 kWe were solar

generated, the array field would encompass

about 11 (O.D. = 0.4) to 40 (O.D. = 6.0) football

fields. In addition, the need for prompt

telerobotic emplacement of the array panels

and interconnecting cables would present a

significant challenge. Dust erosion, dust

accumulation, and wind stresses on the array

panels raise power system lifetime issues. For

these reasons, nuclear power was deemed the

most appropriate primary power source for

the fixed surface power system. However, use

of the “in-space” solar array and fuel cell

power system is assumed as the habitat

emergency/backup power systems, which

could be stowed until needed. The MAVs will

also be provided with this same solar array

backup system to ensure that the

manufactured propellants are maintained in

their cryogenic state should power from the

nuclear system be lost (Withraw, et al., 1993).

3.6.4.6.2 Mobile Surface Power Systems

The other major category of surface

systems needing a power source will be the

rovers. The three types of rovers identified,

long-range pressurized, local unpressurized,

and long-range robotics, each have power

requirements driven by their range and the

systems they must support. Several power

source options were evaluated for the rovers,

including solar arrays/RFCs, combustion

engines, and isotopes. Solar array systems

were not considered due to the large size of

the array needed to support each vehicle.

The long-range pressurized rover must

be able to support a crew of 2 to 4, with a 500-

km range sortie (5 days out, 10 days at site, 5

days back). The power estimate for this rover

is 10 kWe continuous. It is anticipated that the

pressurized, regional rover or its power

system would be used to assist in the

deployment of the main power system,

situate future habitat modules, and serve as

backup emergency power when required. A

desirable feature for the rover power system

is that it be mounted on its own cart. This

would add considerable versatility to its use

when the rover is not on a sortie.

The local unpressurized rover is

conceptually the same as the Apollo lunar

rover. It would function to transport the crew

10's of kilometers, 3 hours out and back, and 4

hours at the site.

Table 3-23 shows the estimated mass,

volume, and array or radiator area for the

four power system options listed.
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The Dynamic Isotope Power System

(DIPS) was considered primarily for its low

mass and significantly lower radiator size

compared to the photovoltaic array (PVA)

area. The 238Pu isotope has a half life of 88

years and can be the same design as the flight

proven radioisotope thermoelectric generator

(RTG). The isotope fuel would be reloadable

into other power units in the event of a

failure, thus preserving its utility. Another

feature of isotope fuel is that it does not need

to be recharged and is always ready as a

backup, emergency power source

independent of solar availability or

atmospheric conditions. However, the 238Pu

isotope availability, quantity, and cost are

issues to be addressed.

The PV/RFC power option seems

impractical for the regional rover due to the

large array area. The arrays would have to be

sized to provide required power output

during a local dust storm, the worst-case

scenario, anticipating suspended operations

during potential global dust storm season.

Methane is a possible fuel for the rover

since the propellant plant could produce

additional fuel, given that extra hydrogen is

brought from Earth. Methane could be used

in an appropriately designed fuel cell. The

reactant water would be returned and fed

through an electrolyzer to capture the

hydrogen. However, once the water has been

electrolyzed into H2

 and O2, which the fuel

cell actually uses to operate, it is not prudent

from an energy utilization standpoint to make

methane again. Storing and maintaining

reactants on the rover also needs further

study.

A methane-burning internal combustion

engine could be used to operate either rover.

However, combustion materials would need

to be collected to reclaim the H2

.

Table 3-23 Rover Power System Characteristics

Power System Mass

(MT) Volume (m3

) Area

(m2)

Mass

(MT) Volume (m3) Area

(m2)

Regional Rover Local Rover

Dynamic isotope 1.1 10 33 0.5 4 16

Photovoltaic (PV) RFC 2.8 66(RFC-4)

PV-62)

1,275

recharge by fueling

Primary Fuel Cell 6.5 29 13 0.160 1 6

Methane/Oxygen Internal

Combustion Engine 12 36 n/a 0.160 0.4 n/a
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Given these system characteristics, the

DIPS system was selected for the long-range

pressurized rover, and the primary fuel cell

was selected for the local rover. The DIPS

system can be another level of functional

redundancy for the base systems, and the

small amounts of radiation emitted can be

mitigated by a small shield and distance to

the rover crew. The primary fuel cell would

meet the local rover requirements at less mass

than other options. However, this power

system design assumes refueling after every

sortie. The power system for the long-range

robotic rover was not specifically addressed

in this analysis. However, the long range over

rugged terrain and long duration of this

rover’s missions will likely drive the selection

to an RTG- or DIPS-type system.

3.7 Robotic Precursors

Robotic precursor missions will play a

significant role in two important facets of the

Reference Mission. The first will be to gather

information about Mars that will be used to

determine specific activities the crew will

perform and where they will perform them.

The second will be to land, deploy, operate,

and maintain a significant portion of the

surface systems prior to the arrival of the

crew.

3.7.1 Current Robotic Program Plans

In November and December 1996, NASA

launched two missions to Mars: the Mars

Global Surveyor (MGS) and the Mars

Pathfinder lander. MGS will monitor global

weather and provide global maps of martian

surface topography and mineral distribution.

The Mars Pathfinder will validate entry,

descent, and landing technologies and will

also deploy a microrover on the surface to

analyze the elemental composition of martian

rocks and soil.

NASA’s Mars Surveyor Program will

continue the robotic exploration of Mars with

two spacecraft launches planned during each

of the 1998, 2001, and 2003 opportunities. A

Mars sample return mission is scheduled for

2005. The goals of the Mars Surveyor Program

are to expand our knowledge of the geology

and resources on Mars, to understand the

meteorology and climate history, and to

continue the search for evidence of past life.

3.7.2 Mars Sample Return With ISRU

Detailed laboratory analyses of martian

rock, soil, and atmosphere samples at Earth

will provide essential information needed

before sending humans to Mars. In addition

to an understanding of the martian

environment, a sample return mission will

afford the opportunity to validate the

technology of ISRU for propellant production.

As discussed in Section 3.6.4.3, ISRU is a

critical technology for the Reference Mission.

To ensure that this technology is available for

the human missions, it should be

demonstrated on the Mars sample return in

2005.
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3.7.3 Human Exploration Precursor

Needs

Robotic precursor missions offer the

capability to demonstrate and validate the

performance of key technologies that are

essential to the Reference Mission (such as

ISRU, aerobraking and aerocapture at Mars)

and to provide information needed for site

selection.

Critical to selection of the landing site for

the humans will be the availability of

indigenous resources, and of paramount

importance is water. Precursor missions

which can identify the location and

accessibility of water will be invaluable in the

Mars exploration program. To satisfy the

human habitation objectives in particular, it

would be highly desirable to locate an

outpost site where water can be readily

extracted from minerals or from subsurface

deposits. Such a determination may only be

possible from data collected by a surface

mission.

With the three human missions all

landing at the same site, selection of that

landing site is very important. The location

chosen must permit the objectives of the

Reference Mission to be achieved.

Consequently, the site will be chosen on the

basis of proximity to a region of high science

yield, availability of water or other

indigenous resources, and operations

considerations such as a hazard-free terrain

for safe landing and surface mobility. Final

site selection may require several robotic site

reconnaissance landers to be sent to survey

various candidate sites. Detailed maps of

candidate landing sites built from data

gathered by these precursor missions will

define the safety and operational hazards of

the sites, as well as confirm access to

scientifically interesting locations and

resources.

In summary, then, the Reference Mission

assumes a set of robotic precursor missions

which includes:

•The Mars Surveyor Program

•A Mars sample return mission in 2005

which also demonstrates in situ

propellant production

•Other sample return missions to various

interesting regions

•A demonstration of aerobraking/

aerocapture

•Mission(s) to search for resources,

particularly water

•Site reconnaissance landers to aid in the

selection of the human landing site

The last two mission types may have

their objectives incorporated into the Mars

Surveyor Program or the Mars sample return

mission; or a separate set of missions may be

required.

3.7.4 Autonomous Deployment of

Surface and Orbital Elements

As described in Section 3.5.3.2, a key

strategy of the Reference Mission is to use a

split mission concept that will allow
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unmanned cargo to be sent to Mars on low

energy, longer-transit-time trajectories. These

unmanned elements must arrive at Mars and

be verified to be operating properly before the

human crew is launched from Earth. The

arrival, precision landing, deployment, and

operation of these surface or orbital elements

will be performed using robotic systems. The

detailed nature of these robotic systems was

not examined as part of this study; however,

the discussion of the surface facilities and the

nature of the operations involved to set up,

maintain, and, if necessary, repair these

facilities can well be imagined. This area of

technology development will be a very active

one to meet the needs of the Reference

Mission.

3.8 Ground Support and Facilities

Operations

The overall goal of mission operations is

to provide a framework for planning,

managing, and conducting activities which

achieve mission objectives. (In general,

mission objectives can be considered all

activities which maintain and support human

presence and support scientific research

during the mission.) Achieving this

operational goal requires successful

accomplishment of the following functions.

•Safe and efficient operation of all

resources (includes, but is not limited to,

vehicles, support facilities, training

facilities, scientific and systems data, and

personnel knowledge and experience

bases).

•Provision of the facilities and an

environment which allow users (such as

scientists, payload specialists, and to an

extent crew members) to conduct

activities that will enhance the mission

objectives.

•Successful management and operation of

the overall program and supporting

organizations. This requires defining

roles and responsibilities and

establishing a path of authority. Program

and mission goals and objectives must

be outlined so that management

responsibilities are clear and direct.

Confusing or conflicting objectives can

result in loss of resources, the most

important of which are time and money.

In addition, minimizing layers of

authority will help avoid prolonged

operational decision-making activities.

This is key when considering large,

complex programs such as the Reference

Mission.

As with the discussion of crew operations

(Section 3.4), specific hardware, software, and

system recommendations will not be made in

this section. Guidelines for the organization

and management of operations are put

forward as foundation on which an actual

operations philosophy and detailed plan

should be built.

The organization of supporting facilities

must follow the lower costing and innovative

approaches being taken by other areas of the

Reference Mission. One way of achieving this
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is to use the related expertise and

functionality of existing facilities to keep to a

minimum the layers of authority and

overhead in the program and take advantage

of the existing knowledge bases at each

facility. Proper and efficient organization of

mission operations and support facilities is

required for any program to be successful.

The Reference Mission has the added

complication of being a program with phases

that cannot be supported with near real-time

operations. Planetary surface operations pose

unique operational considerations on the

organization of ground support and facilities.

Near real-time ground support, as provided

for current manned space programs, is not

possible. A move toward autonomy in vehicle

operations, failure recognition and resolution,

and mission planning is needed; and ground

support must be structured to support these

needs. Some of the specific criteria required

for allocating functions between ground

support and the Mars surface base will be the

available resources at the remote site versus

on Earth, criticality of functions for crew

safety and mission success, and desired time

and resources available for achieving

scientific mission objectives.

In general, due to the uniqueness of

planetary surface operations, Earth-based

support should manage and monitor

operations planning and execution, and crew

members should be responsible for operations

planning and execution. Crew members will

be told what tasks to do or what objectives to

accomplish, but not how to do it. This has the

benefit of involving system and payloads

experts in the overall planning, yet giving

crews the flexibility to execute the tasks. This

approach differs from current Space Shuttle

operations where detailed plans are prepared

by ground personnel, crew members execute

the plans, and ground personnel monitor in

near real-time. The crew members are fully

involved in execution but do little in terms of

planning. The proposed method for the

Reference Mission would take advantage of

the unique perspective of crew members in a

new environment but would not restrict their

activities because of the mission’s remote

nature. Additionally, it places the

responsibility of mission success with the

crew, while the overall responsibility for

prioritizing activities in support of mission

objectives resides with Earth-based support.

After dividing functional responsibilities

between Earth-based support and crew, the

support may be structured to manage the

appropriate functions. To accomplish mission

objectives while maintaining the first

operational objective of safe and efficient

operation of all resources, Earth-based

support can be organizationally separated

into systems operations and science

operations, provided a well-defined interface

exists between the two. The systems

operations team would be responsible for

conducting the safe and efficient operation of

all resources, while the science operations

team would be responsible for conducting

activities which support scientific research.

Such an organizational structure would
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dictate two separate operations teams with

distinct priorities and responsibilities yet the

same operational goal.

Crew and vehicle safety are always of

primary concern. When those are ensured,

science activities become the highest priority.

To accommodate this hierarchy of priorities

within the operations management structure,

the overall operations manager should reside

within systems operations. A science

operations manager, who heads the science

operations team, should organizationally be

in support of the operations manager. Various

levels of interfaces between systems engineers

and science team members must exist to

maximize the amount of science and mission

objectives that can be accomplished. For

example, a proposed science activity may

need systems information for its planning and

feasibility studies, and such information,

including providing access to the systems’

experts, must be made available. There may

be a few overlapping areas of responsibility

between the systems and science teams. (In

the area of crew health and safety, for

example, scientific investigators doing

biomedical research on the crews will have to

interface with the systems medical team

responsible for maintaining crew health.)

Avenues for such interaction and exchange

must be provided to ensure mission success.

3.8.1 Systems Operations

Systems operations are those tasks which

keep elements of the program in operational

condition and support productive utilization

of program resources. Thus, the systems

operations team has the responsibility for

conducting the safe and efficient operation of

all such resources and consists of

representatives from each of the primary

systems (power, propulsion, environmental,

electrical, etc.) used throughout the various

mission phases. This organizational structure

is similar to current flight vehicle operations

where representatives for each system are

responsible for verifying the system’s

operational functionality. Each system

representative will have an appropriate

support team of personnel familiar with the

hardware and software of that system.

Real-time operational support will be

applicable only during launch, Earth orbit (for

vehicle and crew checkout), and Earth entry

phases. As a result, the systems operations

team will function in a response, tracking,

and planning mode throughout most of the

other mission phases. Thus, Earth-based

operations will be a checks and balances

function analogous to the mission

engineering functions executed during Space

Shuttle missions. Hardware and software

documentation will be available to the crew

on board for real-time systems operations and

failure response. However, Earth-based

support must be provided for instances where

documentation is limited or does not cover a

particular situation.

Except for the above mentioned near

real-time mission phases, data monitoring by

Earth-based personnel must be limited to

periodic evaluations. Data and
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communication constraints will make realtime system monitoring by Earth-based

personnel impractical and unfeasible. Failures

and other systems issues will be worked by

Earth-based personnel on an as needed basis

and in support of long-term trend analysis.

Vehicle and system maintenance and

checkout will be evaluated by the Earth-based

systems experts to assist in crew monitoring

and verification. Consumables management

such as usage planning and tracking will be

done by the crew (with some degree of

automation) with Earth-based personnel

doing verification only.

3.8.2 Science Operations

The science operations team’s sole

function is to recommend, organize, and aid

in conducting all activities which support

scientific research within the guidelines of the

mission objectives. The team will consist of

representatives from the various science

disciplines (biology, medicine, astronomy,

geology, atmospherics, etc.) which support

the science and mission objectives. Each

scientific discipline will have an appropriate

support team of personnel from government,

industry, and academia who have expertise in

that field. The science operations team will act

as the decision-making body for all science

activities from determining which activities

have highest priority to handling and

disseminating scientific data. The science

operations team will be coordinated and

managed by the science operations manager,

who will be the ultimate decision maker and

the primary interface between the science

team and the operations manager.

As science activities (such as initial

investigations, clarification of previous

research, and follow-up investigations) are

proposed by various principle investigators,

the science team will evaluate the proposed

research, determine feasibility and

appropriateness of the study, and select

appropriate crew activities based on available

time and personnel. This process is similar to

the process used by the National Science

Foundation for the U.S. Antarctic Program

which has successfully operated remote

scientific bases in Antarctica since 1970

(Buoni, 1990). Selected science proposals will

be presented to the systems operations team

for evaluation of feasibility and resources. For

example, appropriate members of the systems

operations team will determine if there are

enough consumables to support the required

activities and if all of the desired activity is

operationally feasible from a systems

standpoint. Upon verification, the proposed

research activity will be submitted to the crew

for execution.

An initial set of science activities will be

planned before each crew departs Earth. This

is especially true of the scientific

investigations which support not only crew

health and safety but also the primary

mission objectives. As new discoveries are

made and new avenues for research are

opened, an iterative science planning process

will become essential for the success and

effectiveness of all scientific activities.
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Successful scientific operations will also

require, when needed, crew access to the

principal investigators for a given research

avenue. Such access must be made feasible

within the structure of mission operations.

3.9 Programmatic Issues

Three significant programmatic issues

must be considered in an undertaking of this

magnitude, if the undertaking is to be

successfully achieved: cost, management,

and technology development. Each of these

factors was examined to determine how they

should be incorporated into this and further

studies of the Reference Mission or

comparable endeavors.

3.9.1 Cost Analysis

Cost analysis is an important element in

assessing the value of a program such as this

and should be used from the very beginning.

But at the beginning of a program and, in

many cases, up to the time that specifications

are written and contracts are let, it is not

possible to analytically determine the cost of a

program. If new systems need to be

developed for programs, it is not possible to

know at the outset what the total cost will be

because hardware is not on the shelf. For

these reasons, cost models are used that are

typically based on historical data for similar

programs.

•The total program cost will be important

to the beneficiaries and resource

providers, who will be interested in

whether to invest current and future

resources in this program or some

alternative program. As many of the

benefits of an exploration program are

intangible and long term, reducing the

program costs to an understandable and

supportable level is of prime

importance.

•Whatever the total cost, the program will

not be undertaken if resources are not

available. Thus, cost estimates can be the

basis for apportionment of resource

requirements between participants,

phasing of resource provisions, or

phasing of mission elements to avoid

peak-year funding issues that could

stymie the program. Little has been done

in the Reference Mission costing to

address this question; however, the

database is available to analyze costphasing strategies.

•The cost of mission elements and

capabilities needs to be understood in

order to prioritize early investments in

technology and initiate other costreduction strategies. The estimated cost

of each element (for example, ETO

launch) is related to the program risk,

with higher relative costs associated

with larger perceived risks of

development or operation. Thus,

understanding the cost can be a first step

in designing program risk-reduction

strategies. As part of this process,

estimates were also made of the cost

uncertainty for each of the technical

elements of the mission, which are also
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useful in understanding the appropriate

capability development strategies. In the

past, technology development efforts

have focused primarily on improving

performance. Now, it is important to

address reduction of cost as a goal of the

technology development program.

The cost of a program such as the

Reference Mission is a function of two major

variables: the manner in which it is organized

and managed and the technical content of the

program.

3.9.1.1 Organizational Culture and Cost

Management systems and the

organization under which programs are

conducted are a major factor in the cost of a

program. Basing costs simply on historical

data implies that the management system

under which the historical programs were

carried out will be assumed for the new

program. This is a particularly serious

problem in estimating the Reference Mission

costs, as the environment in which future

space exploration will be carried out will be

much more cost-conscious than in the past.

Changes in management, for which no

comparative costs are available, will have to

occur. Because management style and culture

are introduced at each level of design and

production, the leverage of management

changes in making cost reductions can be

quite high. However, such changes are

difficult to estimate. This is a major reason

why cost analysis should be considered a

design tool to be used at all stages of a

program. It is also a major reason to seek

examples or benchmarks in other programs to

determine the best possible management

approaches to design and development, or to

conduct specific programs under new

management rules as prototypes for the

approach that will be used in the actual

program.

The cost of doing space missions lies at

the extreme edge of costliness in comparison

to other high technology systems. The

technical reasons for this appear to be that

space missions:

•Are usually one of a kind or are projects

with small numbers of production units

•Are typically aimed at expanding

capability and technology, so are

designed with small margins of mass,

power, volume, etc.

•Have high transportation costs, so high

reliability in the spacecraft is important

•Are expected to operate for extended

periods of time in difficult environments

and, in the case of crewed vehicles, they

must meet high standards of safety

The engineering and management

culture that has been built up around these

characteristics has stressed excellence of

performance, safety, and high reliability. Cost

has typically been a secondary criterion. It is

not clear that high quality performance and

high reliability always require the

corresponding costly culture.
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To illustrate the effect of culture on cost,

consider Figure 3-41 which shows the relative

cost of programs developed using different

management approaches. Point 0 is the

relative cost for human spacecraft, point 1 is

for robotic spacecraft, point 2 for missiles, and

point 3 for military aircraft. Differences in

management styles develop as a result of the

different environments in which programs are

carried out.

Table 3-24 depicts the differences

between a “Skunk Works” management

environment, such as might be used on a

military aircraft development program (point

2 in Figure 3-41) and the environment for

NASA’s human programs. Some of these

differences will have to be addressed if the

cost of human space exploration is to be

reduced. To further illustrate differences,

Table 3-25 compares the parameters of the

development culture for commercial aircraft

and NASA human programs. These are

starting points that indicate the changes that

will be necessary.

The cost model used for the Reference

Mission (see next section) takes these

variables into account in a “culture” variable,

which can be characterized in more detail by

such attributes as organizational structure,

procurement approach, and the degree of

program office involvement in production.

3.9.1.2 The Cost Model

The cost model used for the technical

content of the Reference Mission is the

Advanced Missions Cost Model (AMCM)

(Cyr, 1988). This model considers the scale

(particularly mass), the scope (number of

production and test articles) of the

development of each of the systems required

to undertake the program, the complexity or

technical readiness for each of the systems

and their subsystems, the schedule under

which the program will be carried out, and

the production generation in which the item

is produced. To the extent that experience

exists or off-the-shelf hardware can be

procured, more precise numbers can be

estimated. The newer or more untried a

technology is, the greater will be its cost in the

model.

Input for the AMCM model was derived

from previous experience and information

provided by members of the Study Team.

Included in the estimate were the

development and production costs for all of

the systems needed to support three human

crews as they explore Mars. In addition,

ground rules and assumptions were adopted

that incorporated some new management

paradigms, as discussed later in the Program

Management and Organization section. The

management costs captured program level

management, integration, and a Level II

function. Typical pre-production costs, such

as Phase A and B studies, were also included.

Not included in the cost estimate were

selected hardware elements, operations, and

management reserve. Hardware costs not

estimated include science equipment and EVA

systems, for which data were not available at

the time estimates were prepared; however,
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Figure 3-41 The relative cost of programs using different management

approaches.

these are not expected to add significantly to

the total. No robotic precursor missions are

included in the cost estimate although their

need is acknowledged as part of the overall

approach to the Reference Mission.

Operations costs have historically been as

high as 20 percent of the development cost.

However, due to the extended operational

period of the Reference Mission and the

recognized need for new approaches to

managing and running this type of program,

estimating the cost for this phase of the

progam was deferred until an approach is

better defined. Similarly, the issue of

management reserve was not addressed until

a better understanding of the management

approach and controls has been developed.

When compared to earlier estimates of a

similar scale (NASA, 1989), the cost for the

Reference Mission is approximately an order

of magnitude lower. A distribution of these

costs is shown in Figure 3-42. It can be seen

from this figure that the major cost drivers are

those associated with the transportation

elements: the ETO launch vehicles, the TMI

stages, and the Earth-return systems. In

addition, the organization mechanisms

chosen have significantly reduced the cost for

these elements of cost, when compared to

traditional programs of this type, creating a

significant challenge for those who would

manage this program.

The Mars Study Team recognizes that,

even with a significant reduction in the

program cost achieved by this team, the
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Table 3-24 Program Environment Effects on Program Management Style

Environment Factor "Skunk Works" Management NASA Human Program

Management

Political Environment - Major threat perceived by all

 involved

- Non-urgent

- Threat not perceived as critical

Cost of Failure - Hidden - Public

- Potentially catastrophic to

 Agency

Products - High technology

- Prototypes

- Experimental

- High technology

- High quality "mature" designs

Risk to Life - Acceptable, but

- Worthy of spending major resources

 to avoid

- Unacceptable

- Worthy of spending major

 resources to avoid

Public Perception - Secret

- Defense

- Urgent

- Unaware of existence until after

 deployment

- Public

- Science, exploration

- Discretionary

- Every detail open to public

 scrutiny and criticism

Schedule - Typically 2 years - Typically 8 to 10 years

Quantities - Small to moderate - Small to moderate

Management Teams

• Contractor

• Government

- Very small (under 10)

- Very small (3 to 10 typically)

- Moderate to large (dozens)

- Large (hundreds)

Political Support - High - High

Cost - Small portion of parent agency

 budget

- Low specific cost (e.g., $/1b)

- High percentage of parent

 agency budget

- High specific cost
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Table 3-25 A Comparison of Development Culture Parameters for Commercial Aircraft and

NASA Manned Programs

Parameter Commercial Aircraft Program NASA Human Program

Management

Customer Role Requirements definition, arms

length

Highly interactive

Type of Requirements Performance of the product Detailed build specifications, some to

piece part level

Program Office Size and

Type of Interactions

Small (tens or less)

Interaction for clarification of

details

Large (hundreds)

Interaction to lowest WBS levels

Proximity of Program Office

Relative to Customer

Geographic separation, frequent

travel by very small groups

Geographic separation, with frequent

travel for face-to-face meetings by

large numbers of project people

Competition Through Commitment to fixed price by

supplier

Three phases: end of preliminary

design, program definition, start of

detailed design and development

Technology Status at Full

Scale Development Start

Totally demonstrated flight

systems

Proof of concept

Management Systems Supplier's systems only:

occasional tailored reports to the

customer

Customer imposed, often duplicative

with contractor systems

Length of Full Scale

Development

2 to 3 years 6 to 15 years

Budget Strategy Full commitment with guarantees

by both parties

Annual, incremental, high risk

Changes None to very few Thousands per year

Fee Type Included in fixed price Fixed, and/or award, based on

supplier performance

Contract Type Fixed price with incentives Cost plus fixed, award fee

SR&QA Industry and supplier standards Customer specified
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magnitude is probably still too high in today’s

fiscal environment. More work to further

reduce these costs is needed.

The largest cost element of the Reference

Mission is the ETO transportation system

which makes up approximately 32 percent of

the total program cost. This element was

assumed to be a new HLLV capable of lifting

220 tonnes of payload to LEO. Although this

is a launch vehicle larger than any previously

developed, its design was assumed to be

based on the Saturn V technology, and

engines were selected from existing designs.

The costs of development were approximately

20 percent of the total ETO Line Item, and

production costs (assuming that 12 HLLVs

would be produced to support the program,

using 3 HLLVs for the first opportunity and 3

HLLV launches at each of the remaining 3

launch opportunities) were 80 percent of the

ETO Line Item.

To reduce the cost of the HLLV

component, several possible strategies could

be used.

•Reduce the mass of systems,

infrastructure, and payloads that need to

be launched into Earth orbit for

transport to Mars to support the surface

mission (assume that mission capability

is not going to be reduced, which is also

possible but not desirable). This could

reduce the total number of HLLV

launches and the assumed production

cost. For example, Robert Zubrin

believes that the program could be

carried out using two HLLV launches

per opportunity (requires some

reduction of capability) (Zubrin, et al.,

1991). Reducing the number of launches

from 12 to 8 would reduce the

production costs by one-third and would

reduce total costs of this element by 26

percent. Developments in new materials,

which are rapidly occurring, could

improve systems performance and

reduce the mass of the protective shells

and vehicle systems.

•Reduce the size of the HLLV (also

proposed by Zubrin). This might or

might not reduce total costs, because

additional costs for on-orbit operations

might be required. Reducing the cost of

launch to LEO using reusable vehicles

currently under consideration in the

reusable launch vehicle program would

require very large investments in LEO

assembly. The trade-off might be

favorable, but may or may not make a

significant reduction in total cost. The

availability and use of an in-orbit

assembly capability like the International

Space Station could make this an

effective strategy.

•Improve the production efficiency for

HLLVs. The AMCM model includes a

learning curve assumption that each

time the number of items produced

doubles, the cost per item is 78 percent

of the previous production cost. More

production learning could be very
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Figure 3-42 A comparison of the relative costs for Reference Mission elements.

significant. For example, if 12 HLLVs of

equal capability had been produced for

another program, the cost of HLLVs for

the Mars program could be cut by 22

percent. To achieve these cost reductions

would require that no special

modifications be necessary for the ETO

vehicles used by the Mars program.

•A significant reduction in HLLV cost

might be designed in at the start if new

techniques for manufacturing and

testing were introduced. However, the

learning curve benefits of mass

production might be less.

•The HLLV development was assumed to

be purchased by the government in a

conventional manner; however, some

procurement aspects were assumed to be

new, and credit was taken in the

estimates for these new ways of doing

business. The HLLV might be developed

by industry at lower cost, to meet

performance specifications rather than

government technical specifications. The

assured sale of 12 vehicles may be large

enough to achieve some amount of cost

reduction to LEO, but is not likely to

lead to major cost reductions. However,

industry might be able to consider the

government an “anchor tenant” for

HLLV production, develop additional

markets for their technology, and

amortize the investment over a larger

TMI Stage

16%

Habitation

14%

R&D

2%

ETO

32%

CoF

1%

Surface Systems

11%

Space Transport

22%

Resources

2%
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number of vehicles. This would imply an

assumption that the space frontier is

expanding significantly.

•The HLLV could be supplied by the

Russians or as a joint effort by multiple

international partners. This might be a

contribution to an international program

where it would be an example of costsharing between partners. At the present

time, this does not appear to be a feasible

solution; however, it may be reasonable

in 15 years. If the U. S. or other partners

were expected to pay the Russians for

their participation, it would require the

appropriate political rationale. If the

Russians were to contribute the HLLV

without payment, it would be the

equivalent of one-fourth of the total

program cost, though it might not cost

the Russians as much as it would cost

the U. S. in absolute dollars.

•Finally, innovative advances in

propulsion could result in the

development of new propulsion

techniques; for example, electromagnetic

propulsion for ETO could substantially

decrease the transportation cost for some

materials (propellant).

The Earth-Mars vehicle (the TMI stage)

and the Mars-Earth vehicle (the ERV)

elements provide for the delivery of humans

and payloads to Mars and the return of

humans to Earth. The costs are for the

transportation elements alone (the

interplanetary habitat elements are not

included). The TMI stage was costed

separately because it was assumed to require

separate development of a nuclear thermal

propulsion system. The TMI stage was

assumed to be jettisoned before reaching

Mars. Conventional space storable chemical

propellants were assumed to be used in the

ERV stage to return to Earth. The nuclear

thermal stage assumed considerable

inheritance from the U. S. nuclear propulsion

program that produced the NERVA engines in

the 1960s; development costs for the TMI

stage were projected to be 16 percent of the

total cost. The space transportation vehicles

are all new and include several vehicles

(ascent vehicle, crew capsule, and the TEI

stage). The cost of the space transportation

vehicles comprises 22 percent of the total.

The ratio of development cost to

production cost for these vehicles is rather

high, partly because of the smaller number of

vehicles produced for the return home.

Various ways of reducing the costs of these

elements might be considered.

•Development of nuclear electric or solar

electric propulsion vehicles that are more

efficient could lower transportation costs

for cargo but might not reduce costs of

human flights and might increase costs if

parallel development of two

transportation systems was necessary. If

a single technology with higher

efficiency than chemical rockets could be

used to go to Mars and return, much of

the cost associated with developing the

space transportation stages might be
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saved because the number of separate

developments would be minimized.

•Systematic application of new

techniques of automated design to the

development process and use of

concurrent engineering could reduce life

cycle costs of the systems.

•General improvements in methods of

procurement and program management

could have significant returns in these

areas. Reduction of integration costs can

be accomplished by centrally locating

design and development teams and

keeping simple interfaces between

systems manufactured by different

providers.

•Several vehicle elements could be

provided by international partners. Each

of the vehicles provided without cost to

the program could reduce total program

costs by several percent.

Habitats are an essential part of the

Reference Mission scenario. They represent 14

percent of total mission cost and are assumed

to have inheritance from the International

Space Station program. The Reference

Mission has made the assumption that all

habitats required by the program are

essentially identical, which is probably an

oversimplification. To the extent the design of

space habitats and surface habitats diverges,

the cost could rise. Eight production habitats

are required. Modest learning curve cost

reductions are assumed for the production

line. About one-third of the estimated cost of

habitats is development, production is the

remaining two-thirds. Thus, cost reductions

involving the improvement of design and

procurement processes are potentially the

most important objectives. Note, however,

that the habitats are also a significant mass

element; therefore, technology that reduces

their mass will also have a significant effect

on the transportation system.

Surface systems, including mobility

systems and resource utilization systems,

surface power, and other nonhabitat systems,

constitute about 11 percent of the total

mission cost. Because these surface systems

are rather complex, critically determine

mission productivity, and are a small fraction

of the total, this area does not appear to be a

high-priority source of major additional cost

reductions. However, mass reductions in the

hardware will have high leverage in the space

transportation cost elements, if the size of the

transportation vehicles or the number of

launches can be reduced. Surface systems

costs are probably underestimated in the

current model, because no data for a closed

LSS, EVA hardware, and science hardware

were included in this estimate. Development

of a suitable EVA suit will be a significant

technology challenge and potentially

expensive. The closed environment LSS

hardware probably is not extraordinarily

expensive. However, testing and

demonstrating it will only partially occur in

the International Space Station program, so

additional cost and risk are involved in its

development. Science equipment is not a
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major cost item, in comparison with the large

costs ascribed to the transportation system.

Operations was not included as part of

the cost analysis, but has been previously

estimated as a proportion (historically as high

as 20 percent) of the total development costs.

The operations costs are incurred primarily in

the 11 years of the operational missions. The

allocation of budget that would be associated

with this estimate is equivalent to

approximately 20,000 people per year for that

period of time. This is definitely an old way of

doing business which must change for the

Mars missions. A reasonable target would be

an operational team of approximately l,000

persons. This is likely to be attainable in part

because automation and autonomy will be a

necessary characteristic of the Mars missions.

A principal mechanism for reducing these

costs may be a directed program to reduce the

operational costs of the International Space

Station as an analog to Mars missions.

The number and type of systems

represented in the Reference Mission is near

minimal considering the desired surface

mission capability. It is always possible to

reduce costs by reducing the required

performance. For example, using the same

assumptions used for this model if only a

single landing were carried out, the total

program costs would be reduced by about 30

percent in comparison to the full three piloted

mission program. Reducing the scope of the

surface activity will not have a big effect on

cost, as it is already a relatively small

proportion of total mission costs, confirming

the expectation that optimizing the surface

mission for its benefit is also the way to

improve the benefit/cost ratio for the human

exploration of Mars.

The question of management style must

now be addressed. Particular attention needs

to be paid to the process by which the

production elements are procured. The

current estimates probably are still influenced

by current ways of doing business. If total

Reference Mission costs are to be reduced, it is

at this level of effort that the most effective

changes can be made. Focusing on the wrap

factors may not accomplish significant

additional reductions, although reducing the

production costs will also reduce the amount

that must be spent in these areas.

3.9.2 Management and Organizational

Structure

Organization and management is one of

the principal determinants of program cost.

This is a rather wide-ranging topic, which is

not entirely divisible from the technical

content of the program, because it includes

program level decision making that is

intimately tied to the system engineering

decision-making process.

The magnitude of the Reference Mission,

once it has been initiated, is enormous. Many

good examples exist of smaller programs that

have failed or have not performed well due to

management deficiencies. Thus, as the

Reference Mission is examined and improved,

continued consideration should be given to

streamlining its management; assigning
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authority, responsibility, and accountability at

the right levels; and developing processes that

are simple, with clear-cut interfaces and

measurable performance standards.

The relationship between cost and

management style and organizational culture

is rather well-known in a general manner,

through a large number of lessons learned

analyses made postprogram. The list of key

elements of lower-cost programs is shown in

Table 3-26. These have been pointed out in a

series of analyses, but have not commonly

been applied at the critical stage of

developing program organization and

management approaches. Rather, the

organizational and management style has

been determined rather late in the program,

generally because the program content and

final design were typically delayed through

redesign, changing requirements, and

funding irregularities.

To manage a Mars program to a lowest

possible cost, a number of considerations

have been identified.

•The design of the organization and

management system should be an area

of investigation in subsequent studies of

the Reference Mission. The relationship

between program cost and program

culture is illustrated in Figure 3-46.

Although several factors are involved,

this figure indicates that significant cost

impacts are tied to the organizational

culture and the management system.

•The human exploration of Mars will be

highly visible to the world, will be a tool

of international policy in many

countries, will be complex and

expensive, and will take several years to

develop. Under these conditions, it is

essential that a philosophical and

budgetary agreement be reached prior to

initiating development. A formal

agreement should be reached between

all parties as to the objectives and

requirements that are imposed on the

mission before development is initiated,

and an agreement to fund the project to

its completion should be reached prior to

development. In the U. S., this would

include multiyear budgetary authority.

This should be accompanied by a

management process that would protect

against program overruns through

appropriate incentives.

•The human exploration of Mars will

have quite different risks than any space

mission which will have been

undertaken at its time. These include

risks to the safety of the crew and

accomplishment of the mission

(primarily technical risks) and risks of

meeting cost and schedule objectives.

Maintaining launch schedule is

exceedingly important, due to the

dependency on several successful

launches for mission success and the

high cost of missed launch windows

(missed launch windows imply 2-year

program delays at potentially high
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Table 3-26 Key Elements of Lower-Cost Programs

• Use government to define only requirements

• Keep requirements fixed; once requirements are stated, only relax them; never add new

ones

• Place product responsibility in a competitive private sector

• Specify end results (performance) of products, not how to achieve the results

• Minimize government involvement (small program office)

• Ensure that all technologies are proven prior to the end of competition

• Use the private sector reporting reporting system: reduce or eliminate specific

government reports

• Don't start a program until cost estimate and budget availability match

• Reduce development time: any program development can be accomplished in 3 to 4

years once uncertainties are resolved

• Force people off development programs when development is complete

• Incentivize the contractor to keep costs low (as opposed to CPAF, CPFF, or NASA)

• Use goegraphic proximity of contractor organizations when possible

• Use the major prime contractor as the integrating contractor

program cost). Thus a risk management

plan can help identify the risks and

formulate a mitigation strategy.

•The Reference Mission requires a

number of elements, many of which are

technically alike but serve somewhat

different functions over the duration of

the program. For example, the surface

habitat may be the basis for the transit

habitat, and each habitat delivered to the

surface will have a different complement

of equipment and supplies, according to

its position in the delivery sequence. The

elements will be developed over a

period of several years, and there will be

a temptation to improve the equipment

and supply manifest. It will be important

for requirements to be fixed at the time

of initial development to maintain cost

control for the program. To accomplish

this:

-There should be a clear demarcation

between the design phase and the

development/production phase of the

project, and development should not

begin before the design phase is ended.

-All technologies should be proved prior

to initiation of production of program

elements.

-Once the requirements have been

established, they should not be changed

unless they can be relaxed.

-A system should be developed that

documents the relationship and

interaction of all requirements and

should be available for use prior to the

beginning of production.
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•The design phase of the program is

critical to successful cost control. The

design should be based on a set of

functional requirements established by a

Program Office, which may well be a

multinational activity. The Program

Office should be in place to manage

technical requirements, provide

decisions that require consultation and

trade-offs (technical and political), and

manage development contracts. The

Program Office should also establish

functional requirements for the design

phase and conduct a competitive

procurement for the design phase with

the selection of a prime contractor. To

accomplish this:

-Requirements should be provided for the

design phase, describing the

performance expected, and a clear set of

criteria for completeness of design as a

function of resources expended in

design.

-A significant design cost margin should

be used to manage the design resources.

-The successful prime contractor should

be selected as integration contractor for

the development phase.

•Once committed to development, the

development time should be strictly

limited if costs are to be contained. This

will be difficult in the Mars program,

where it probably will be effective to

produce common elements sequentially

rather than all at one time, although

there may be a high enough production

rate that costs will drop as experience is

gained. A new approach will be needed

to ensure that the development time for

each individual element is strictly

limited.

•The program will require two levels of

integration, similar to that of the

International Space Station program: a

program level which ensures that overall

mission requirements will be met at each

stage of the mission, and a launch

package level integration in which all

required elements of each launch to

Mars are packaged and their

performance ensured. To accomplish

this, both aspects of integration should

be the responsibility of a single

organization, a prime contractor to the

Program Office.

•The operational phase of the Mars

program must be represented in the

design and development phase. This will

require a concurrent engineering

approach which considers the

operational costs as well as the

development costs in a life cycle cost

approach to the program. To accomplish

this, operational considerations must be

included in the design and development

phases of the program, and life cycle

costs should be used as the determinant

for program design and development

decisions.
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•Finally, at all stages of design,

development, production, and

operations, all program office officials

and contractor organizations must be

incentivized to maintain program costs

within approved levels, and positive

incentives must be put into place to

reduce costs of each phase of the

program.

3.9.3 Technology Development

The Reference Mission was developed

with advances assumed in certain technology

areas known to be necessary to send people to

Mars for a reasonable investment in time and

resources. The same objective could be

satisfied using other technologies in some

cases, making it necessary to identify

selection criteria for the set of technologies the

Reference Mission should favor. A reasonable

investment also implies that there must be

some reliance on technologies developed for

other uses or simply discovered during some

other development activity.

Dual-use technologies are those which

are deliberately developed with more than

one application in mind and which carry

requirements for these various uses through

the development period. Spin off or spin in

technologies are those which are developed

with a specific application in mind but which

find other uses with little or no additional

development work. Spill over technologies

are those which grow to include entirely new,

unplanned technologies as a by-product of

the effort to bring the original technology to

its desired state.

At this particular stage in developing

human exploration missions to Mars, it is

difficult to do more than speculate about spin

off and spill over technologies that could

result from, or be useful to, this endeavor.

However, identifying dual uses for some of

the assumed technologies can be started now

and, to a certain degree, will be required for

such a program to progress. In the current

political environment, investment in

technology is seen as a means of improving

the general quality of life, and multiple use of

technologies is emphasized to obtain the best

return on the resources invested in their

development. Space programs are not spared

this requirement. A program strategy that

emphasizes dual-use technologies, besides

being consistent with this current trend could:

•More easily generate funds through

increased cooperation and joint ventures

with other U.S. federal agencies,

international partners, and commercial

concerns

•Provide smaller projects which could be

more easily funded

•Provide a step-by-step approach to the

Reference Mission

•Provide a stimulus to local and national

economies

•Foster an increase in advocacy for space

programs
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To this end, the Reference Mission study

identified and worked with 10 Mars missionrelated technology categories: propulsion,

communications and information systems,

ISRU, surface mobility - suits, surface

mobility - vehicles, human support, power,

structures and materials, science and science

equipment, and operations and maintenance.

These categories were then associated with a

total of 54 technology areas along with their

applications. Tables 3-27 through 3-36

document these various technology

applications. In addition, the tables indicate

where these technologies may spin off into

other applications and where developments

in other areas may, in fact, benefit or spin into

the Mars program.

Not all of the advantageous technology

for the Reference Mission must be developed

by the program organization. International

cooperation can benefit from the technology

advancements needed for this class of space

mission. Two obvious examples include

heavy lift launch technology and space-based

nuclear power. The relatively heavy lift

launch capabilities either developed or

nearing completion for the Russian Energia

and the European Ariane V could form the

basis for at least part of a cooperative

technology development program. The

former Soviet Union had also developed a

relatively sophisticated operational spacebased nuclear power capability.

U.S. federal agencies can also cooperate

to develop mutually beneficial technologies.

The long-standing cooperation between

NASA and the Department of Energy to

develop small nuclear power sources for

robotic spacecraft could be expanded to

include the development of larger power

sources (perhaps as part of a cooperative

endeavor with the Russian government) or

for the propulsion system technologies

assumed for the Reference Mission. The

Department of Defense is currently studying

an integrated propulsion and electrical power

system driven by the heat of the Sun

(Reference: Anon., 1995). This could be a

technology useful to the Reference Mission as

an alternative to the nuclear system assumed

and form the basis for a cooperative

development program.

Several specific examples may help

illustrate how technology development for

the Reference Mission will benefit from spill

over, spin off, and dual-usage.

One of the precursor activities to the

Reference Mission that has a high priority will

be the characterization of the martian surface

in great detail by orbiting robotic spacecraft.

Data collected by this vehicle or vehicles will

be needed in many areas to prepare for this

Reference Mission. One of the most

significant areas will be the choice of a

landing site at which the outpost will be

established. This selection will be based in

part on information ranging from hazards in

the proposed landing zone to the proximity of

the site to a variety of surface features, the

investigation of which will contribute to

meeting the overall Reference Mission

objectives. Technology to obtain this remote
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sensing data could be available from the U.S.,

Russia, Japan, and the Europeans, based on

their previous Earth-orbiting, remote-sensing

missions and other planetary explorations.

But due to the high cost of transporting these

sensors to the vicinity of Mars, further

development or enhancement of these

technologies could reduce their size, mass,

and need for supporting resources (power,

communications band width, etc.).

Advancements in other areas, such as the Ka

band utilization, data compression, and

information processing technologies

mentioned in the Communication and

Information Systems category or from

technology developed as part of the explosive

growth in the PC marketplace, can also serve

to improve performance and reduce costs for

these systems and the data they return. Any

technology enhancement developed to

support the Reference Mission will then be

available for use in Earth-orbiting

applications.

The single largest cost of a human Mars

exploration program may be the cost of ETO

transportation. The development of a new

HLLV solely for the Mars program could

require up to 30 percent of the total resources

for the program. However, approaches that

can launch the appropriate payloads to Mars

using smaller launch vehicles have not

appeared to be viable in the past. This is a

conundrum which has and may still stymie

human exploration of Mars. Other avenues

exist:

•The Russian Energia heavy lift launch

system can be maintained and upgraded

until human missions to Mars can begin.

A variation of this would be to evolve a

higher capacity launch vehicle using

technologies developed for Energia,

Ariane V, and the Space Shuttle. Either of

these options would offer an

opportunity for international

cooperation that would not only benefit

the Reference Mission but also allow for

heavier, more sophisticated payloads to

be launched into Earth orbit or used for

lunar missions.

•The mass of hardware required to

support humans in Mars journeys can be

reduced. Few concepts now exist for

this, but advancements in the technology

options mentioned in most, if not all, of

the 10 categories identified by the Mars

Study Team will lead to a reduction in

the hardware mass that must be sent to

Mars. Each of the 10 categories also

identified Earth-bound applications that

may also benefit from these

advancements.

A third example involves the significant

level of automation assumed for the

Reference Mission. The program assumes

infrastructure elements (including a system to

produce propellant and life support

consumables, the first of two habitats, power

systems, and surface transportation elements)

will robotically land on the surface at a

designated location. All of these systems will

be delivered, set up, and checked out using
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Table 3-28 Dual-Use Technologies: Communications/Information Systems

spin-in

spin-off

Both

Terrestrial Application Technology Space Application

• Communications High-Definition

 TV Broadcast

• Ka Band or Higher • Telepresence: Vision and

 Video Data

• Interferometers: Raw Data

 Transmission

• Entertainment Industry

• Commercial Aviation

• Machine-Human Interface • Control Stations

• System Management

• Communications

• Archiving

• Data Compression

 Information Processing

• Large Scale Data

 Management Systems

• Interferometers: Raw Data

 Transmission Information

 Processing

• System Management,

 Expert Data

• Archiving/Neural Nets

Terrestrial Application Technology Space Application

• Nuclear Reactors

• Weapons and Nuclear Waste Disposal

• High-Efficiency Heat Engines

 (Turbines, Thermostructural Integrity)

• High-Temp Materials • NTR

• Aerobraking

• Clean-Burning Engines (H2

/O2) • High Efficiency

 Cryo-Refrigeration

• Propellant

 Maintenance

• Higher Performance Commercial Launches • Methane/O2

 Rocket

 Engines

• ISRU-Based Space

 Transportation

Table 3-27 Dual-Use Technologies: Propulsion
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spin-in

spin-off

Both

Terrestrial Application Technology Space Application

• Mineral Analysis, Yield Estimation-

 Deep Mine Vein Location and Tracking

• Wall and Ceiling Integrity

• Advanced Sensors • Mineral Analysis, Yield

 Estimation Surface Mineral

 Analysis, and Resource

 Location

• Deep Mine Robotic Operations

 • Mining

 • Beneficiating

 • Removal

• Advanced Robotic

 Mining

• Surface Mining Operations

 • Mining

 • Beneficiating

 • Removal

• Improved Automated Processing;

 Increased efficiency • Automated Processing:

 Advanced FDIR

• Remote, Low-

 Maintenance, Processing

• Reliable, Low-Pollution Personal

 Transmission

• Regenerable Energy Economies

• Small, Decentralized Power Systems for

 Remote or Third World Applications

• Alternative, Regenerable

 Energy Economies

 • Methane/O2

 • H2/O2

• ISRU-Based Engines

• Regenerable Energies

• High-Density Energy Storage

• Environmentally Safe Energy Production • Space-Based Energy

 Generation and

 Transmission

• Surface Power Generation

 and Beaming

Table 3-29 Dual-Use Technologies: In Situ Resource Utilization
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Terrestrial Application Technology Space Application

• Hazardous Materials Cleanup

• Fire Fighting Protection and

 Underwater Equipment

• Lightweight, Superinsulation

 Materials

• Surface Suits: Thermal

 Protection

• Robotic Assisted Systems

• Orthopedic Devices for Mobility

 Impaired Persons

• Robotics

• Mobility Enhancement Devices

 and Manipulators

•Robotic Assisted Suit Systems

• Hazardous Materials Cleanup

• Fire Fighting Protection and

 Underwater Equipment

• Dust Protection, Seals, Abrasive

 Resistant Materials

• Surface Suits: Outer Garment

• Hazardous Materials Cleanup,

 Underwater Breathing Gear

• Lightweight Hi-Rel, Life Support • Portable Life Support for Surface

 Suits

• Remote Health Monitoring • Portable Biomedical Sensors and

 Health Evaluation Systems

• Surface EVA Crew Member

 Health Monitoring

• Hypo-Hyper Thermal Treatments

• Fire Fighting Protection and

 Underwater Equipment

• Artic/Antartic Undergarments

• Small, Efficient, Portable,

 Cooling/Heating Systems

• Surface Suits: Thermal Control

 Systems

Table 3-30 Dual-Use Technologies: Surface Mobility - Suits

Table 3-31 Dual-Use Technologies: Surface Mobility - Vehicles

spin-in

spin-off

Both

Terrestrial Application Technology Space Application

• All-Terrain Vehicles

 • Research (Volcanoes)

 • Oil Exploration

• Mobility • Surface Transportation

 • Humans

 • Science Equipment

 • Maintenance and

 Inspection

• Reactor Servicing/Hazardous

 Applications

• Robotics and Vision Systems • Teleoperated Robotic Systems

• Earth Observation, Weather, Research • Super-Pressure Balloons

 (110,000 ft - Earth Equiv)

• Mars Global Explorations

• Efficient, Long-Term Operations

 Low-Maintenance

• Machines in Artic/Antaric

 Environments

• Tribology • Surface Vehicles

 • Drive Mechanisms

 • Robotic Arms

 • Mechanisms

• Helicopers, Autos • Variable Speed Transmissions • Surface Vehicles

• Automated, Efficient Construction

 Equipment

• Multipurpose Construction

 Vehicle Systems and Mechanisms

• Robotic Construction and

 Set-up Equipment
3-142

Table 3-33 Dual-Use Technologies: Power

Table 3-32 Dual-Use Technologies: Human Support

spin-in

spin-off

Both

Terrestrial Application Technology Space Application

• Stored Food

 • US Army

 • NSF Polar Programs

• Long-Life Food Systems

 • With High Nutrition

 • Efficient Packaging

• Efficient Logistics

 • Planetary Bases

 • Long Spaceflights

 • Space Stations

• Improved Health Care

• Sports Medicine - Cardiovascular

• Osteoporesis - Immune Systems

• Isolated Confined Environments/Polar

 Operations

• Noninvasive Health Assessments

• Physiological Understanding of the

 Human/Chronobiology

• Understanding of Psychosocial

 Issues

• Instrumentation Miniaturization

• Countermeasures for Long-Duration

 and/or Micro-g Space Missions

• Health Management and Care

• Health Care

• Disaster Response

• US Army

• Long-Term Blood Storage • Health Care for Long-Duration Space

 Missions

• Office Buildings

("Sick Building" Syndrome)

• Manufacturing Plants

• Environmental Monitoring and

 Management

• Environmental Control for

 • Spacecraft Cabins

 • Planetary Habitats

 • Pressurized Rovers

• Contamination Cleanup

• Waste Processing

• Waste Processing/SCWO

• Water Purification

• Closed Water Cycles for

 • Spacecraft Cabins

 • Planetary Habitats

 • Pressurized Rovers

• Long-Life Clothes

 • Work Clothes in Hazardous

 Environments

 • US Army

• Advanced Materials/Fabrics • Reduced Logistics Through Long-Life,

 Easy-Care Clothes, Wipes, Etc.

• Fire Proof/Low-Out-gassing Clothes

• Efficient Food Production • Advanced Understanding of

 Food Production/Hydroponics

• Reduced Logistics Through Local Food

 Production for

 • Spacecraft Cabins

 • Planetary Habitats

Terrestrial Application Technology Space Application

• Batteries/RFCs for

 • Autos

 • Remote Operations

 • DOD

 • NSF Polar Programs

• High-Density Energy Storage

• Alternate Energy Storage

 (Flywheels)

• Reduced Logistics for Planetary

 Bases

• High-Rel, Low-Maintenance

 Power Systems

• Clean Energy From Space • Beamed Power Transmission • Orbital Power to Surface Base

• Surface Power Transmission to

 Remote Assets

• Remote Operations

 • DOD

 • NSF Polar Programs

• Small Nuclear Power Systems • Surface Base Power

•Pressurized Surface Rover

• Interplanetary Transfer Vehicle

• Remote Operations

 • DOD

 • NSF Poloar Programs

• High-Efficiency Auto Engines

• High-Efficiency, High-Rel,

 Low-Maintenance Heat-to-

 Electric Conversion Engines

• Energy Conversion for Planetary

 Bases

 • Low Servicing Hours

 • Little or no Logistics
3-143

Table 3-34 Dual-Use Technologies: Structures and Materials

Table 3-35 Dual-Use Technologies: Science and Science Equipment

spin-in

spin-off

Both

Terrestrial Application Technology Space Application

• Vehicles

• Fuel-Efficient Aircraft

• Modular Construction (Homes, etc.)

• Composite Materials

 • Hard

 • Soft

• Advanced Alloys, High-

 Temperature

• Cryo Tanks

• Habitat Enclosures

• Pressurized Rover Enclosures

• Space Transit Vehicle Structures

TBD • Superinsulation

• Coatings

• Cryo Tanks

• Habitable Volumes

• Large Structures, High-Rises, Bridges

• Commercial Aircraft

 • Improved Safety

 • Lower Maintenance

• Smart Structures

• Imbedded Sensors

• Space Transit Vehicle Structures

• Planetary Habitat Enclosures

• Surface Power Systems

• Rover Suspensions

Terrestrial Application Technology Space Application

• Energy Resource Exploration

• Environmental Monitoring, Policing

• Spectroscopy

 • Gamma Ray

 • Laser

 • Other

• Geo-chem Mapping

• Resource Yield Estimating

• Planetary Mining Operation

 Planning

• Undersea Exploration

• Hazardous Environment Assessments,

 Remediation

• Telescience • Remote Planetary

 Exploration

• Environmental Monitoring

• Medicine

• Image Processing

 • Compression Technique

 • Storage

 • Transmission

 • Image Enhancements

• Communication of Science

 Data

• Correlation of

 Interferometer Data

• Improved Health Care

• Sports Medicine - Cardiovascular

• Osteoporesis - Immune Systems

• Isolated Confined Environments/Polar

 Operations

• Noninvasive Health Assessments

• Physiological Understanding of

 the Human

• Instrumentation Miniaturization

• Countermeasures for Long-

 Duration and/or Micro-g

 Space Missions

• Health Management and

 Care
3-144

robotic systems perhaps operated from or,

more likely, merely supervised from Earth.

Due to the communications time delay and

the absence of any local human operator or

repair personnel, these systems must be

capable of performing normal operations,

sense system failures or imminent failures,

and, if necessary, safely shut down or repair

failed items. Chemical processing plants and

manufacturing plants on Earth are

approaching this level of sophistication and it

may be possible to adapt some of the

technologies from these plants, as well as

from technology that will exist in the future,

to the Reference Mission. But as with the

remote sensing example, the Reference

Mission will enhance the automation and

maintenance technologies used which will

then be available to Earth-bound users for a

variety of applications.

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We mentioned this area as important, but did not complete. Recommend that we work with Jon Ericson and bob

Savely to get ir right.

spin-in

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Both
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1-1

National Aeronautics and

Space Administration

Lyndon B. Johnson Space Center