NASA E XPLORATION T EAM

H UMAN S UBSYSTEM W ORKING G ROUP

GUIDELINES

AND

C APABILITIES

FOR

D ESIGNING HUMAN MISSIONS

M ARCH 2002
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

i 

CONTRIBUTORS 

The following people contributed to or reviewed this document: 

! Christopher S. Allen, NASA JSC Space & Life Sciences Directorate, Habitability & Environmental Factors 

Office 

! Rebeka Burnett, NASA JSC Space & Life Sciences Directorate, Habitability & Environmental Factors Office 

! John Charles, NASA JSC Space & Life Sciences Directorate, Program Integration Office 

! Frank Cucinotta, NASA JSC Space & Life Sciences Directorate, Habitability & Environmental Factors Office 

! Richard Fullerton, NASA JSC EVA Project Office 

! Jerry R. Goodman, NASA JSC Space & Life Sciences Directorate, Habitability & Environmental Factors Office 

! Anthony D. Griffith Sr., NASA JSC Mission Operations Directorate, Advanced Operations Development 

Division 

! Jitendra Joshi, NASA HQ, Advanced Human Support Technology Program 

! Joseph J. Kosmo, NASA JSC, Crew & Thermal Systems Division, EVA & Space Suit Systems Branch 

! Alyssa Mueller, NASA JSC Space & Life Sciences Directorate & Futron Corporation, Advanced Technology 

Integration Group 

! Michele Perchonok, NASA JSC Space & Life Sciences Directorate, Habitability & Environmental Factors Office 

! Jan Railsback, NASA JSC Safety, Reliability, & Quality Assurance Office, Technology Division 

! Sudhakar Rajulu, NASA JSC Space & Life Sciences Directorate, Habitability & Environmental Factors Office 

! Marianne Rudisill, NASA LaRC, Spacecraft & Sensors Branch 

! Anne Simmons, Futron Corporation 

! Don Stilwell, NASA JSC Space & Life Sciences Directorate, Advanced Technology Integration Group 

! Gretchen Thomas, NASA JSC Engineering Directorate, Crew & Thermal Systems Branch 

! Terry Tri, NASA JSC Engineering Directorate, Crew & Thermal Systems Branch 

! John Wilson, NASA LaRC, Structures & Materials Competency, Analytical & Computational Methods Branch 

! Ray Wheeler, NASA KSC, Biological Sciences Branch 

Please note that this is draft document and is still under review. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

ii 

TABLE OF ACRONYMS 

ADS altitude decompression sickness 

AG artificial gravity 

ALARA as low as reasonably achievable 

ALS advanced life support 

BEO beyond Earth orbit 

CD crew day 

CH crew hour 

CME coronal mass ejection 

CMO crew medical officer 

CPR Critical Path Roadmap 

CWS caution and warning system 

DO dissolved O2 concentration 

ETO Earth-to-orbit 

EVA extravehicular activity 

GCR galactic cosmic radiation 

GFE government-furnished equipment 

HCD human-centered design 

IC integrated circuit 

IMLEO initial mass in low-Earth orbit 

IMS intravehicular maintenance system 

ISS International Space Station 

IT information technology 

IVA intravehicular activity 

LEO low-Earth Orbit 

LET linear energy transfer 

LMLSTP Lunar-Mars Life Support Test Project 

MDO multi-disciplinary optimization 

MSIS Man-System Integration Stands (NASAStandard-3000) 

NC noise criteria 

NCRP National Council on Radiation Protection and 

Measurements 

NIOSH National Institute of Occupational Safety and 

Health 

PTS permanent threshold shift 

RBE relative biological effectiveness 

SAS space adaptation sickness 

SMAC spacecraft maximum allowable concentration 

SPE solar particle event 

STD software test description 

STS Space Transportation System 

TDD technology-driven design 

TTS temporary threshold shift 

UV ultraviolet 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

iii 

TABLES AND FIGURES 

Table 1.1: Boundary Conditions ................................................................................................................................2

Table 1.2: Exploration Implementation Options ........................................................................................................2

Table 1.3: Recommended Web Sites........................................................................................................................4

Table 2.1: Distribution of Severe and Very Serious Risks across the Critical Path Roadmap Areas .......................7

Table 5.1: Characteristics of Radiation Sources in the Space Environment a ........................................................15

Table 5.2: Non-Ionizing Radiation Exposure Limits a ..............................................................................................16

Table 5.3: Limits for Exposure to Non-Ionizing Sunlight in Space a........................................................................17

Table 5.4: Recommended Organ Dose Limits for Deterministic Effects (All Ages) for LEO Operations 4..............17

Table 5.5: Career Effective Dose Limits a................................................................................................................17

Table 5.6: Estimates of Safe Days Gained in Space from Different Forms of Mitigation 5 .....................................18

Figure 6.1: Elements of Space Medicine.................................................................................................................22

Table 6.1: Ranking of Medical Events or Complaints from Analog Data a ..............................................................23

Table 8.1: Examples of Critical Body Dimensions a,b ..............................................................................................31

Table 9.1: Summary of Water Consumption per Crewmember for Different Operational States ...........................35

Table 9.2: Historical, Near-term Food Masses a......................................................................................................36

Table 9.3: Food Quantity and Packaging a..............................................................................................................36

Table 9.4: Twenty-Day Diet Using All Potential Food Crops a ................................................................................40

Table 9.5: Twenty-Day Diet Using Salad and Carbohydrate Crops a .....................................................................40

Table 9.6: Estimated Waste Mass for Different Mission Profiles a ..........................................................................41

Table 11.1: ISS Hearing Protection Requirements Versus 24-hour Noise-Exposure Levels a ...............................52

Table 11.2: Intermittent Noise Emission Limits a.....................................................................................................54

Table 11.3: Oxygen Concentrations at Different Pressures a..................................................................................55

Table 11.4: Atmosphere Thermal Comfort Requirements a ....................................................................................58

Table 12.1: Defining Characteristics of Intelligent Systems and Interfaces ............................................................60

Table A.1. Historical Space Program Habitat and Spacesuit Atmospheres............................................................73

Table B.1: Waste Components................................................................................................................................81

Table B.2: Inedible Biomass Calculation for a 20-Day Diet Using All Available Crops a.........................................82

Table B.3: Inedible Biomass Calculation for a 20-Day Diet Using Carbohydrate Crops a ......................................83

Figure D-1: Entering Parameters into the Calculation Spreadsheet .......................................................................87

Table D.1: Mass Factors for Crew Accommodations in Various Mission Types ....................................................89

Table D.2: Volume Factors for Crew Accommodations in Various Mission Types.................................................91
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

iv 

TABLE OF CONTENTS 

CONTRIBUTORS .................................................................................................................I

T ABLE OF ACRONYMS ........................................................................................................II

T ABLES AND FIGURES ...................................................................................................... III

T ABLE OF CONTENTS........................................................................................................ IV

1 OBJECTIVES ...........................................................................................................1

1.1 Scope

1.2 Background

1.3 Ground Rules and Assumptions

1.4 References

2 RISK IN HUMAN EXPLORATION MISSIONS .....................................................................5

2.1 Key Concepts

2.2 Fundamental Guidelines

2.3 Mission Success

2.4 References

3 HUMAN-RATED VEHICLE REQUIREMENTS ................................................................... 10

3.1 General

3.2 Safety and Reliability

3.3 Human-In-The-Loop

3.4 Emergency Provisions

3.5 References

4 ARTIFICIAL GRAVITY.............................................................................................. 12

4.1 Key Concepts

4.2 Benefits

4.3 Current Limitations

4.4 Design Considerations

4.5 References

5 RADIATION ........................................................................................................... 15

5.1 Key Concepts

5.2 Non-Ionizing Radiation Considerations

5.3 Ionizing Radiation Considerations

5.4 Uncertainties in Exposure Risk Estimates

5.5 Radiation Countermeasures

5.6 Future Directions

5.7 References

6 ROUTINE AND EMERGENCY MEDICAL CARE ................................................................ 21

6.1 Key Concepts

6.2 Rates of Incidence

6.3 Emergency Care

6.4 Design Considerations

6.5 Medical Technologies and Inventory

7 PSYCHOSOCIAL INTERACTION .................................................................................. 27

7.1 Crewmember Performance

7.2 Crew Interaction

7.3 Communications

7.4 Emergencies and Crises

7.5 Crew Structure and Authority

7.6 Re-assimilation on Earth Return

7.7 References

8 ANTHROPOMETRY AND BIOMECHANICS ...................................................................... 31

8.1 Key Concepts

8.2 Definition of Crew Population
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

v 

8.3 Anthropometric Design Considerations

8.4 References

9 CREW ACCOMMODATIONS ....................................................................................... 34

9.1 Key Concepts

9.2 Resource Model

9.3 Water, Food, and Food Packaging

9.4 Growth Chambers

9.5 Waste Management

9.6 Personal Hygiene

9.7 Intravehicular Maintenance System

9.8 References

10 ARCHITECTURE AND HABITABILITY ........................................................................... 46

10.1 Key Concepts

10.2 Overarching Issues

10.3 Total Habitable Space

10.4 Crew Quarters

10.5 Galley and Wardroom

10.6 Exercise Facilities

10.7 Recreation Facilities

10.8 Stowage Facilities

10.9 References

11 CREW ENVIRONMENT ............................................................................................. 51

11.1 Key Concepts

11.2 Acoustic Noise

11.3 Acceleration, Vibration, and Impact Limits

11.4 Cabin Pressure

11.5 Co2, Trace Gas, and Humidity Limits

11.6 Materials Selection

11.7 Thermal Systems

11.8 Toxicology and Contamination Limits

11.9 References

12 INFORMATION TECHNOLOGY INTERFACES................................................................... 59

12.1 Key Concepts

12.2 Design Considerations

12.3 Intelligent Systems

12.4 Workstations

12.5 Design Considerations

12.6 Information Technology

12.7 References

13 WORK INTERFACES AND TOOLS ............................................................................... 65

13.1 Tools and Aids

13.2 Design Considerations for EVA

14 PAYLOAD ACCOMMODATIONS .................................................................................. 67

14.1 Plant and Animal Factors

15 PLANNING FOR HUMAN OPERATIONS ......................................................................... 70

15.1 Training

15.2 Emergency Response Provisions

15.3 Allocation of Crew Time

APPENDIX A: ATMOSPHERIC PRESSURE .............................................................................. 71

APPENDIX B: WASTE ....................................................................................................... 81

APPENDIX C: SENSORY ADAPTATION ................................................................................. 85

APPENDIX D: CREW RESOURCE MODEL .............................................................................. 87
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 1: Objectives 1

1 OBJECTIVES 

These guidelines and capabilities are meant to identify the points of intersection between humans and 

mission considerations such as architecture, vehicle design, technologies, operations, and science requirements. 

We seek to provide clear, top-level guidelines for human-related exploration studies and technology research that 

address common questions and requirements. As a result, we hope that ongoing mission trade studies consider 

common, standard, and practical criteria for human interfaces. 

1.1 SCOPE

The human element is likely the most complex and difficult one of mission design; it significantly influences 

every aspect of mission planning, from the basic parameters like duration to the more complex tradeoffs between 

mass, volume, power, risk, and cost. For engineers who rely on precise specifications in data books and other 

such technical references, dealing with the uncertainty and the variability of designing for human beings can be 

frustrating. When designing for the human element, questions arise more often than definitive answers. 

Nonetheless, we do not doubt that the most captivating discoveries in future space missions will necessitate 

human explorers. 

Beyond this statement of cause-and-effect, human-driven requirements are highly variable because of 

destination, operational environment, mission objectives, and more. Often, the precise quantification of 

parameters for a human mission is difficult without further study or precise definition of a specific mission 

architecture. Each mission design requires several iterations as the effects of the crew on the system architecture 

(and vice-versa) coalesce. For this reason, we see this document as a tool for understanding the many tradeoffs 

inherent in planning a human space flight mission. 

In the following pages, we convey the key drivers on human safety, health, and performance as simply as 

possible. By integrating this information into mission trade studies, mission planners can better address the most 

important human needs. We make every attempt to deal only with material necessary to mission designers in the 

conceptual design phase. The finer details of the vehicle design human and crew accommodations are not within 

the scope of this document. 

1.2 BACKGROUND

We have distilled guidelines and recommendations from personal experience and a good number of sources; 

because many comprehensive sources are already available, we do not attempt to recreate these. A majority of 

the chapters include detailed reference lists. 

We approach the difficulty of designing for the human presence by briefly describing the fundamental 

concepts and definitions required for decision-making and by considering (where possible) the design tradeoffs of 

current alternatives. When uncertainty arises, we present both the pros and cons of the alternatives, the bestworst boundary conditions, and other caveats for making the best decision. With such an approach, we envision 

that this document becomes only the first step of many towards understanding the human element of the space 

mission. 

The objectives for this document are as follows: 

! Synthesize the current thinking of experts who have spent considerable time considering future missions 

in and beyond low-Earth orbit (LEO); 

! Provide a digestible overview of key human requirements and considerations that drive the success of a 

crewed mission; 

! Clearly introduce some of the problems that must be solved or resolved in planning for human mission 

planning; and 

! Supply mission planners with the requisite tools for making decisions appropriate to a given mission, 

without exhaustively cataloging all possible designs for all possible missions. 

Finally, this document is intended to supplement the many excellent texts that cover the complex issues 

involved with designing future human missions, which are included at the end of each chapter in the References 

section. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 1: Objectives 2

1.3 GROUND RULES AND ASSUMPTIONS

Safe and affordable human systems are feasible for future missions. A human space-faring crew, working 

cooperatively and in concert with intelligent systems and robotics, is needed to answer the greatest questions 

about our solar system and the universe beyond. For this document, we assumed a set of boundary conditions 

described in Table 1.1. 

Table 1.1: Boundary Conditions 

Remote destinations Includes libration points, Moon, and Mars 

Mission duration 50ñ100 days or 500ñ1000 days 

Transport durations 5ñ10 days (near Earth) or 90-180 days (Mars) 

Transport cargo frequency Monthly (near Earth) or every 2 years (Mars) 

Human/robot options Standalone, cooperative, local/remote telepresence (see Table 1.2) 

Tasks Planetary/astronomical sciences, assembly, maintenance, contingencies, commerce 

Primary safety criteria Near-zero risk to public on Earth 

Mission safety criteria Return all crew alive without serious injury or illness 

Assembly/maintenance criteria Spacecraft stable and viable for productive work 

Science success criteria Majority of tasks completed 

Overall success criteria No major impediment to subsequent missions 

Budget Generally flat across the agency for the foreseeable future 

Mass, volume and power Severely-constrained delivery mass 

International participation Likely 

Human Capabilities 

Although robots and artificial intelligence can accomplish specific tasks better than humans and vice-versa, 

robots as intelligent and as capable as humans do not yet exist. Automation alone cannot accomplish the desired 

scenarios within a reasonable timeframe. While automated systems are appropriate for some functions, the 

following human capabilities may well enable otherwise difficult or completely impossible missions. 

! Productivity: use of the brainís creative and cognitive abilities enables rapid, real-time, and on-scene 

decisions, which overcome time delays and data bandwidth limits. 

! Reliability: adaptive and proven capability for manual response to unforeseen, unique, and nonrepetitive activities. 

! Cost and mass: less need to expend resources upon complex, redundant, and fully automated designs. 

For this reason, we emphasize the essential capabilities of humans throughout this document. The options 

and impacts of possible human and robotic roles are included in Table 1.2: 

Table 1.2: Exploration Implementation Options

Robot Method Human Role Site Access Data Scope Relative Cost Hardware Repair Safety Risk 

Remote 

teleoperation 

Earth-based 

control 

Lowest Lowest Low None None 

Fully automated Earth-based 

monitoring 

Low Low Low-medium None None 

Local teleoperation Orbital habitat Low Low-medium Medium None Low 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 1: Objectives 3

Robot Method Human Role Site Access Data Scope Relative Cost Hardware Repair Safety Risk 

Local teleoperation Lander habitat; 

no EVA 

Low Low-medium Medium-high None High 

Variable autonomy Lander habitat; 

no EVA 

Low Medium Medium-high None High 

Variable autonomy 

(pressurized garage) 

Lander habitat; 

no EVA 

Low Medium Medium-high Partial High 

Variable autonomy 

(dockable to habitat) 

Canned mobility; 

no EVA capability 

Low-medium Medium High Partial Highest 

Precursors only Suited humans 

on foot 

Medium-high High Medium-high Full Medium 

Variable autonomy 

(total crew access) 

Suited 

transportable 

humans with 

rovers 

Highest Highest Highest Full Medium-high 

1.4 REFERENCES

Note: Each chapter of this document includes both cited and recommended references. Where possible, NASA 

or general access Web addresses are provided. The following references should be considered part of the 

general reference library for any mission designer or planner. 

1 Charles J and Leveton L. ìCritical Path Roadmap Baseline Document.î NASA Bioastronautics Research 

Division; latest revision 2001 April. Related content available on the public access Web site: 

http://criticalpath.jsc.nasa.gov. 

2 Booher C. Document No. JSC-33695, ìMan-Systems Integration Standards,î Rev B, Vol 1ñ4. NASA JSC 

Human Factors and Habitability Office; July 1995. Available on the NASA internal Web site: http://jsc-webpub.jsc.nasa.gov/fpd/shfb/Msis/MSIS_home.htm. 

3 Griffin B, Spampinato P, and Wilde R. ìChapter 22: Extravehicular Activity (EVA) Systems.î In: Larson W and 

Pranke L, editors. Human Spaceflight: Mission Analysis and Design. New York: McGraw Hill; 2001. p 707-

757. 

4 Parker JF Jr and West V, editors. Report No. NASA-SP-3006, Bioastronautics Data Book. 2nd ed. 

Washington DC: NASA Scientific and Technical Information Office; 1973 January. 

5 Calvin M and Gazenko O, editors. Report No. NASA-SP-374, Foundations of Space Biology and Medicine, 

Vol 1ñ3. Washington DC: NASA Scientific and Technical Information Office; 1975 January. 

6 Connors M, Harrison A, and Akins, F. Report No. NASA-SP-483, Living Aloft: Human Requirements for 

Extended Space Flight. Washington DC: NASA Scientific and Technical Information Branch; 1985. Available 

on the public Web site: http://www.hq.nasa.gov/office/pao/History/SP-483/cover.htm. 

7 Anonymous. Report No. DV-00-014, ìOperations Concept Definition for the Human Exploration of Mars.î 

2000 May. 

8 Stuster, J. Bold Endeavors: Lessons from Polar and Space Exploration. Annapolis (MD): Naval Institute 

Press; 1996. 

9 Eckart P. The Lunar Base Handbook. Space Technology Series of NASA and US Air Force; 1998. 

10 Committee on Advanced Technology for Human Support in Space, National Research Council. Catalog No. 

5826, ìAdvanced Technology for Human Support in Spaceî Washington DC: National Academy Press. 

1997. (Available in HTML on the NAP Web site: http://www.nap.edu/books/0309057442/html/index.html) 

11 Hoffman S and Kaplan D. Report No. NASA-SP-6107, ìHuman Exploration of Mars: The Reference Mission 

of the NASA Mars Exploration Study Team.î 1997 July. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 1: Objectives 4

12 Drake B. Report No. SP-6107-ADD, ìReference Mission Version 3.0 Addendum to the Human Exploration of 

Mars: The Reference Mission of the NASA Mars Exploration Study Team.î 1998 June. 

13 Report No. TP-1999-209371, ìMars Reference Mission - Surface Activities.î 1999 December. 

14 Report No. SSP-50261-01, ìISS Generic Ground Rules, Requirements and Constraints.î 1998 December. 

15 Report No. SSP-50391, ìISS Crew Loading Report.î 1999 July. 

16 Report No. NSTS-12820, ìISS Generic Flight Rules.î 1997 February. 

17 Report No. SSP-41162E, ìISS U.S. Segment Specification.î 1997 January. 

18 Report No. NASA-RP-1045, ìPhysiological basis for spacecraft environmental limits.î 1979. 

19 Report No. JSC-25003, ìInternal Atmospheric Pressure and Composition for Planet Surface Habitats and 

EMUs.î 1991. 

20 van Laak J. Report No. JSC-28354, ìHuman-Rating Requirements.î 1998. 

21 Report No. JSC-29295, ìJSC Radiation Report.î 2001. 

22 Drysdale A and Hanford A. Report No. JSC-39317, ìAdvanced Life Support Systems Modeling and Analysis 

Project: Baseline Values and Assumptions Document,î Crew and Thermal Systems Division, NASA JSC. 

1999 June. (Available on the NASA Web site: http://pet.jsc.nasa.gov/JSC39317_(BVAD).doc, but to be 

updated in the near future) 

Table 1.3: Recommended Web Sites 

Web Site Address Subject or Comments 

http://advlifesupport.jsc.nasa.gov Advanced Life Support home page 

http://advtech.jsc.nasa.gov Advanced Technology Integration Group home page 

http://criticalpath.jsc.nasa.gov Critical Path Roadmap home page 

http://ares.jsc.nasa.gov/HumanExplore/intro.html Human Exploration Science Office home page 

http://srhp.jsc.nasa.gov Space Radiation Health Project home page 

http://peer1.nasaprs.com/peer_review/prog/prog.html Biological and Physical Research (BPR) Program Plans and 

Requirements Documents 

http://spaceresearch.nasa.gov/research_projects/resplans.html BPR Plans and Documents (new version) 

http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/

EXdocindx.htm Exploration library compiled by the JSC Exploration Office 

http://jsc-web-pub.jsc.nasa.gov/fpd/shfb/Msis/MSIS_home.htm Man-Systems Integration Standards (MSIS) 

http://www.jsc.nasa.gov/xa/advanced.html EVA Exploration Requirements and Rationale (2001) 

http://ares.jsc.nasa.gov/HumanExplore/Exploration/NewFrontie

r/frontier.htm

A New Frontier Beckons: document by the JSC 

Astromaterials Research and Exploration Sciences Office 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 2: Risk 5

2 RISK IN HUMAN EXPLORATION MISSIONS 

A risk is frequently described as any event, action, or outcome that threatens success. Indeed, every space 

exploration mission has risks. In addition to physical risks to the crew and the vehicle, other risks must be 

acknowledged and integrated into mission planning. 

2.1 KEY CONCEPTS

! Cost risk: risks resulting from budgetary issues, including unplanned expenditures or inadequate funding 

! Programmatic risk: risks created by political, management, or technical challenges 

! Biomedical risk: risks that result in loss of crew safety, health or performance to the degree that mission 

success or crew survival is compromised 

! Mission success: the maintenance of crew safety, health, and performance; the completion of key 

scientific goals; the return of selected specimens or data; and the completion of public outreach activities. 

2.2 FUNDAMENTAL GUIDELINES

While specific requirements will be addressed in subsequent sections, the following high-level requirements 

address the fundamental needs of a human crew: 

! Providing for subsistence-level human needs means considerable mass expense. 

! Optimum performance requires optimum conditions. 

! The most carefully selected and well-trained crew will never be superhuman. 

Although mission mass and cost will always be an important goal, we recommend that basic crew 

requirements be addressed for what they are: needs. Cost-effectiveness cannot be the only measure of success 

in mission design. We can only obtain superior results and future mission success by creating a state-of-mind 

and value system that emphasizes the safety, comfort, and productivity of the crew over mass and cost. 

2.3 MISSION SUCCESS

Mission success requires consideration of factors beyond the mission itself. NASA has established an 

overarching priority for risk mitigation: 

1 Public safety is paramount because the public must not be injured by any NASA activity, including launch 

phase malfunctions, the Earth return of hazardous materials (such as nuclear power sources or dangerous 

planetary specimens), or by longer-term consequences, such as environmental damage. 

2 Safety for crewmembers, who are exposed to high risks as a result of space flight, is the second most 

important safety concern. 

3 Safety for employees, to ensure a safe and healthful workplace, is a key NASA value. 

4 Safety of high-value equipment, as public investments in space exploration, takes fourth place. 

Other mission goals, such as science return, must therefore fall lower in priority compared to the safety of the 

human crew. 

A recent study by the Space Studies Board at the Institute of Medicine, Safe Passage: Astronaut Care for 

Exploration Missions, considers the current state of readiness for exploration missions with a human crew. The 

key finding of the study, by a panel of learned experts who interviewed NASA personnel, is not startling to many 

who face the problems of crew health, safety, and performance daily. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 2: Risk 6

The basic findings of the committee are these: (1) not enough is yet known about the risks to humans 

during long-duration missions, such as to Mars, or about what can effectively mitigate those risks to 

enable humans to travel and work safely in the environment of deep space and (2) everything reasonable 

should be done to gain the necessary information before humans are sent on missions of space 

exploration. 

But this stark finding ñ regardless of how feasible a human-rated exploration vehicle may be ñ indicates that 

we cannot absolutely guarantee the health and safety of any space-faring crew. The challenge facing mission 

planners and medical operations personnel then becomes one of risk management: how to address the risks with 

the greatest potential impact to crew health and to mission success? 

Biomedical Risks 

Foremost among the issues associated with a human exploration mission are the biomedical and life support 

risks of the spaceflight environment. These risks are described in the Bioastronautics Critical Path Roadmap 

(CPR), a strategic plan for reducing risks to human health and safety in long-duration space flight (see the 

References section). By virtue of its comprehensive approach to the risks of human spaceflight, the CPR 

provides a: 

! Guide for prioritizing research and technology; 

! Framework for assessing progress in mitigating risks; 

! Way to track effective risk-mitigation strategies; and 

! Means to determine acceptable levels for identified risks. 

Panels of academic and government experts were convened to identify critical risks and a set of core 

questions in twelve different disciplines; this work benefits from the consensus of a broad cross-section of the 

academic and scientific community. As summarized in Table 2.1, the CPR has prioritized 55 critical risks and 343 

critical questions that must be addressed to ensure the success of missions that require an extended human 

presence. Investigation and research to address these risks is supported by the National Space Biomedical 

Research Institute (a consortium of 15 universities) and NASAís Office of Biological and Physical Research. 

While the original proviso of the CPR included missions beyond LEO, current funding levels and management 

direction necessitate that the focus be limited to near-term and immediate mission needs. 

Approaches to Avoid 

Although some activities are inherently dangerous, no human endeavor is completely risk-free. Space 

exploration is arguably dangerous; because human space exploration may threaten the lives of many people at 

taxpayer expense, NASA is expected to take every possible measure to reduce risk. Despite this, reducing 

crewmembersí risk to zero is nearly impossible and any reduction often comes at significant cost. 

Occasionally, the following solutions have been advanced to circumvent the more difficult decisions in mission 

design and risk management. These solutions are deceptively simple and unrealistic if they are carefully 

examined. We provide a brief discussion of each to discourage this kind of thinking in future mission design and 

planning. 

! Accepting current risk: just because a relatively large number of candidates are willing to journey to 

Mars or beyond, despite danger and personal risk, does not mean that mission, programmatic, and personal risks 

can be ignored. 

! Crew selection: carefully selecting a crew for extraordinary resistance to the dangers and difficulties of 

the space environment is not feasible. Statistics refute this for at least two reasons: first, if the top ten percentile 

of individuals are selected by a series of 20 independent scales, at least 1020 individuals must be tested to find 

one person who would rate in the top 10 percent of all of 20 scales; second, variability in the human population is 

not sufficient to provide significant protection against the many challenges of exploration missions. From 

geniuses to religious leaders to sports stars, we share many of the same traits and are subject to many of the 

same weaknesses. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 2: Risk 

Table 2.1: Distribution of Severe and Very Serious Risks across the Critical Path Roadmap Areas

Risk Type 1 Area Risk 

Bone Loss ! Acceleration of age-related osteoporosis Human Behavior and Performance ! Human performance failure because of poor psychosocial adaptation Radiation Effects ! Carcinogenesis caused by radiation 

Type I (severe) 

Clinical Capabilities ! Trauma and acute medical problems Advanced Life Support ! Inability to maintain acceptable atmosphere in habitable areas 

! Inability to provide and recover potable water ! Inadequate supplies (including maintenance, emergency provisions, and edible food) ! Inability to maintain thermal balance in habitable areas ! Inability to adequately process solid wastes ! Malnutrition due to inability to provide and maintain a bioregenerative system ! Inadequate stowage and disposal facilities for solid and liquid trash generated during mis

Food and Nutrition ! Malnutrition 

! Unsafe food systems ! Human performance failure due to nutritional deficiencies 

Bone Loss ! Fracture and impaired fracture healing Cardiovascular Alterations ! Occurrence of serious cardiac dysrhythmias 

! Impaired cardiovascular response to orthostatic stress 

Human Behavior and Performance ! Human performance failure because of sleep and circadian rhythm problems Muscle Alterations and Atrophy ! Loss of skeletal muscle mass, strength, and/or endurance 

! Inability to adequately perform tasks ! Inability to sustain muscle performance levels to meet demands of performing activities o

Neurovestibular Adaptation ! Impaired neuromuscular coordination and/or strength (gait ataxia, postural instability) 

! Disorientation and inability to perform landing, egress, or other physical tasks, especially 

Radiation Effects ! Damage to central nervous system from radiation exposure 

! Synergistic effects from exposure to radiation, microgravity and other spacecraft environ! Early or acute effects from radiation exposure 

Clinical Capabilities ! Toxic exposure 

! Altered pharmacodynamics and adverse drug reactions 

Multi-system (Cross-Risk) Alterations ! Post-landing alterations in various systems resulting in severe performance decrements 

Type II (very serious) 

Environmental Health ! Allergies and hypersensitivity reactions from exposure to the enclosed spacecraft and ot

! Inability to maintain acceptable atmosphere in habitable areas due to environmental hea! Inability to provide and recover potable water due to environmental health contaminants 

1 The type assigned to each risk depending upon the level of uncertainty, both about both knowledge of the risk itself (its occurrence 

mitigation status. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 2: Risk 8 

! Crew privation: many of the more complex issues of human space missions cannot be solved simply by 

supplying the absolute basics and nothing else. In planning any long-duration mission with a human crew, the 

argument of ìseparating needs from greedsî is a fallacy. In fact, any mission beyond LEO cannot ever supply 

crews with the quality of life they have enjoyed on Earth; even the most creative concepts and innovative 

approaches do not diminish basic crew needs. The pressure to reduce the mission cost is constant, but the risk 

to mission success and crew survival does not justify underestimating human needs and overestimating human 

abilities to cope with privation. 

Through careful risk assessment and thorough risk management, we must establish a strong record of 

mission success. If humans are to overcome the limitations of unmanned exploration and to explore the key 

scientific questions of our time, space-faring crews must return from their missions ― and in good shape. 

From the perspective of mission success, any mission should be considered a failure if the crew and the data 

they obtain do not return to Earth. Nor can we subject the public to the knowledge that, during the mission, the 

crewmembers have become sick from radiation exposure or are suffering from stress, privation, and a long 

isolation from Earth. 

Risk-Management Schemes 

Numerous means exist to mitigate or minimize the risks of human space missions within the mission design 

process. Examples include the following: 

! Public protection: The public must be protected against harm from departure and return disasters (e.g., 

debris, fire, and contamination) through fault tolerance, range safety devices, and the safe location of facilities. 

! Precursor information: Risk reduction depends on advance knowledge of environmental conditions, 

performance of engineering products, and human response. Minimizing unknowns, through a balance of ground 

demonstrations, in situ robotic sampling, and realistic in-space rehearsals, ensures mission success and safety. 

! Automated asset deployment: To meet the basic goals of safe scientific exploration and 

commercialization, the amount of time required and risk introduced during setup and maintain life-support 

systems should be minimized. Basic life support should be automatically deployed, and crew must be able to 

verify a system as operational or repairable prior to commitment and use. 

! Design risk out: To minimize reliance upon error-prone and time-intensive human or procedural 

controls, the primary means of risk mitigation should involve designing out risk (e.g., fail safe redundancy, 

material selection, load margins, automation, inherent reliability, and test verification). Normal design criteria 

require two-fault tolerance for crew-safety critical functions. 

! Maintenance design: Maintenance can be a complementary means to restore fault tolerance, noncritical functions, and crew/vehicle safety. Because resupply at remote destinations is limited by orbital 

mechanics, transport time and mass and volume constraints, maintenance provisions must be available on site. 

Tactics to ensure efficient and safe maintenance include: advance deployment of spares, component 

commonality, in situ manufacture, low-level repairs, autonomous training and procedures, robotic implementation 

and preventative attention. Unless impractical, all equipment that may require maintenance will be located 

internally, and whenever possible, all external items should be detachable so that they can be moved to the cabin 

interior for repair. In general, crew time and logistics demands must be minimized and conducted under the 

safest possible conditions. 

! Hazard isolation: Because life-threatening failures may occur, remote placement of hazardous 

materials, redundant containment, and cleanup materials are a few of the options for reducing risk. Crew should 

be able to avoid hazardous devices and work zones or should be able to secure them before entering the area. 

! Safe havens: The crew must be protected from the deleterious effects of exposure to temporary or 

prolonged environmental hazards, such as decompression, temperature extremes, natural or artificial radiation, 

and prolonged microgravity. When conditions exceed suit or habitat protection capabilities, a safety shelter (e.g., 

rover, portable enclosure or hardened habitat zone) is necessary. To be effective, the shelter must combine 

practical shielding technologies with limited exposure times, avoidance of harsh/hostile conditions, supplementary 

shelters, and systems for advance warning. Long-term sheltering may be necessary in the event of permanent 

spacecraft decompression or other non-repairable failure of the life support system. Such catastrophic events 

cannot be handled by an emergency return to Earth or by wearing an extravehicular activity (EVA) suit for years 

or months at a time. Finally, considerable planning must be devoted to the crew facilities in such a shelter. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 2: Risk 9 

2.4 REFERENCES

1 Charles J and Leveton L. ìCritical Path Roadmap Baseline Document.î NASA Bioastronautics Research 

Division; latest revision 2001 April. Related content available on the public access Web site: 

http://criticalpath.jsc.nasa.gov. 

2 Institute of Medicine. Safe Passage: Astronaut Care for Exploration Missions. Washington, D.C.: National 

Academy Press. (Available as an electronic publication from the National Academy Pressí Web site: 

http://www.nap.edu/catalog/10218.html) 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 3: Human-Rated Vehicle Requirements 10 

3 HUMAN-RATED VEHICLE REQUIREMENTS 

The spacecraft serves as the crewís first line of defense against the hazardous space environment. NASA 

has identified design requirements to ensure the safety and reliability of human-rated exploration vehicles. The 

most important requirements, fully addressed in NASA Human Rating Requirements1

, are reprinted below. 

3.1 GENERAL

Requirement 1: The vehicle shall be designed, built, inspected, tested, and certified specifically addressing the 

requirements for human rating. 

Requirement 2: The vehicle design, manufacture, and test shall comply with JPG 80803

 and applicable military 

standards. Where alternative approaches are employed, verification shall be provided that the alternative 

approaches meet or exceed the performance of accepted approaches. 

Requirement 3: The vehicle crew habitability and life support systems shall comply with NASA Standard-3000 

and NASA Space Flight Health Requirements for crew habitability and life support systems design. 

Requirement 4: A successful, comprehensive flight test program shall be completed to validate analytical math 

models, verify the safe flight envelope, and provide a performance database prior to the first operational flight 

(flights other than for the specific purpose of flight test) with humans on board. 

Requirement 5: Spacecraft operations in proximity or docking with a crewed vehicle shall comply with joint vehicle 

and operational requirements so as to not pose a hazard to either vehicle. Provisions shall be made to enable 

abort, breakout, and separation by either vehicle without violating the design and operational requirements of 

either vehicle. Uncrewed vehicles must permit safety critical commanding from the crewed vehicle. 

3.2 SAFETY AND RELIABILITY

Requirement 6: The program shall be designed so that the cumulative probability of safe crew return over the life 

of the program exceeds 0.99. This will be accomplished through the use of all available mechanisms including 

mission success, abort, safe haven, and crew escape 

Requirement 7: A crew escape system shall be provided on future (e.g., post-Space Shuttle) Earth-to-orbit (ETO) 

vehicles for safe crew extraction and recovery from in-flight failures across the flight envelope from pre-launch to 

landing. The escape system shall have a probability of successful crew return of 0.99. 

Requirement 8: For ETO vehicles, abort modes shall be provided for all phases of flight to safely recover the crew 

and vehicle or permit the use of the crew escape system. For beyond-Earth orbit (BEO) missions, spacecraft and 

propulsion systems shall have sufficient power to fly trajectories with abort capabilities and provide power and 

critical consumables for crew survival. Trajectories and propulsion systems shall be optimized to provide abort 

options. When such options are unavailable, safe haven capabilities shall be provided. 

Requirement 9: If a flight termination (range safety) system is required for future (e.g., post-Space Shuttle) ETO 

vehicles, the vehicle design shall provide for safe recovery of the crew. 

Requirement 10: All critical systems essential for crew safety shall be designed to be two-fault tolerant. When this 

is not practical, systems shall be designed so that no single failure shall cause loss of the crew. For the purposes 

of this requirement, maintenance can be considered as the third leg of redundancy so long as mission operations 

and logistics resupply permit it. 

Requirement 11: Vehicle reliability shall be verified by test backed up with analysis at the integrated system level 

prior to the first flight with humans on board and verified by flight-based analysis and system health monitoring for 

each subsequent flight. 

Requirement 12: The performance and reliability of all critical software shall be tested on a flight equivalent 

avionics testbed across the entire flight envelope. Independent verification and validation methods shall be used 

to confirm the integrity of the software testing process. 

3.3 HUMAN-IN-THE-LOOP

Requirement 13: The vehicle shall provide the flight crew on board the vehicle with proper insight, intervention 

capability, control over vehicle automation, authority to enable irreversible actions, and critical autonomy from the 

ground. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 3: Human-Rated Vehicle Requirements 11 

Requirement 14: The flight crew shall be capable of taking manual control of the vehicle during all phases of flight. 

The vehicle shall exhibit Level I handling qualities as defined by the Cooper-Harper Rating Scale. 

Requirement 15: The spacecraft displays and controls design shall be based on a detailed function and task 

analysis performed by an integrated team of human factors engineers with spacecraft displays and controls 

design experience, vehicle engineers, and crew members. Solutions in this design area shall not be limited to 

those derived from experience with Shuttle if newer or alternative concepts are applicable. 

Requirement 16: The mission design, including task design and scheduling, shall not adversely impact the ability of 

the crew to operate the vehicle. 

3.4 EMERGENCY PROVISIONS

To protect crew health and vehicle operation, the vehicle architecture must include the following safety 

systems and features: 

! A smoke detection system that provides non-toxic fire suppression and by-product cleanup; 

! A system that will detect cabin depressurization, seal affected areas, and help determine the location and 

cause of seal breech. Ideally, the system would be able to automatically seal the breech and then re-pressurize 

the area. If the breech cannot be sealed automatically, the crew need to be able to safely enter the depressurized 

area wearing EVA suits: 

! Methods to detect and clean particulate, chemical, and biological contamination; 

! Contingency consumables, to allow time for failure correction or mission extension due to resupply or 

return skip cycle; 

! Early return for untreatable health or vehicle emergency; 

! Multiple escape paths; and 

! Preservation of alternate ingress path. 

Caution and Warning System 

The caution and warning system (CWS) is of particular importance for the prevention or management of an 

emergency: it warns personnel of impending danger, alerts an operator to a critical change in system or 

equipment status, reminds the operator of a critical action or actions that must be taken, and provides advisory 

and tutorial information. The following guidelines are distilled from MSIS Section 9.4 on displays. 

! The CWS must provide standard alarms using both visual and auditory information: 

- Class 1 (emergency): A life threatening condition requiring an immediate and predefined action to 

protect the crew. 

- Class 2 (warning): Conditions requiring immediate correction to avoid loss of major impact to the 

mission or potential loss of crew. 

- Class 3 (caution): Conditions of a less time critical nature, but with the potential for further 

degradation if crew attention is not given. 

! Consider the alarmís frequency, intensity, alerting capability, and discriminability. Design verbal alarms 

for maximal intelligibility, considering speech characteristics, intensity, message content, and repetition. 

! Allow rapid CWS recovery to default and ensure that the CWS remains operational during power failures 

or other anomalies. 

3.5 REFERENCES

1 van Laak J. Report No. JSC-28354, ìHuman-Rating Requirements.î 1998. (Available in HTML on the NASA 

Web site:www.hq.nasa.gov/office/codea/codeae/documentd.html) 

2 Anonymous. Report No. NPG 7120.5A, ìContinuous Risk Management.î 

3 Anonymous. Report No. JPG 8080, ìJSC Design and Procedural Standards Manual.î 1991. (Available in 

PDF on the NASA Web site: nodis.gsfc.nasa.gov/Library/Directives/JSC/Policies/Program_Management/80805.pdf) 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 4: Artificial Gravity 12 

4 A R T I F I C I A L G R A V I T Y 

The concept of creating artificial gravity (AG) was first popularized by Werner von Braun, Arthur C. Clarke, 

and others many years ago. Stanley Kubrickís 1968 movie "2001: A Space Odysseyî brought this concept to the 

forefront of public interest, although gaps in fundamental knowledge and research mean that AG cannot yet be 

considered viable. More than 30 years of sporadic activity in AG research has not elucidated the fundamental 

operating parameters for a countermeasure. 

As indicated in the Critical Path Roadmap (section 2.3.1), current measures for preventing the deleterious

physiological effects of microgravity have been only partially successful for orbiting missions that may last only 10 

to 90 days. Certainly, further countermeasure development is required for missions lasting 1000 days or more. 

4.1 KEY CONCEPTS

Countermeasures that rely in part on AG are still under consideration. Although the rotation of an exploration 

spacecraft or component is not a panacea, and cannot ameliorate radiation exposure, isolation, confinement, and 

environmental homeostasis, it may offer significant promise. Many of the tradeoffs and considerations for an AG 

countermeasure are addressed in the 1999 Artificial Gravity Workshop Proceedings, a multi-day meeting of life 

sciences, engineering, and medical experts discussing AG. 

! Countermeasure: any preventive or mitigating measureówhether a form of exercise, a drug or 

nutritional supplement, or a more complex mechanical deviceóthat addresses the most severe physiological and 

psychological risks of human spaceflight. A countermeasure must also meet stringent specifications for use in 

flight, where resources and crew time are equally scarce.

! Operational performance: level of crew performance that must be maintained during a mission and that 

relies in part on the use of countermeasures. Unfortunately, sufficient empirical information is not yet available to 

qualify the level of performance required for crew performance during a Mars or other long-duration mission.

! Rotational artificial gravity: the primary approach to providing AG (as opposed to linear AG), which 

involves rotation of all or part of the spacecraft to produce constant or intermittent levels of gravito-inertial force.

! G-transition: the physiological and psychological process of adapting to different g environments, as 

may be introduced when applying intermittent AG.

The goal of an AG countermeasure should be to maintain the level of operational performance required 

during and after flight, and to minimize irreversible changes likely to compromise the long-term health and safety 

of the crewmember. 

4.2 BENEFITS

An AG countermeasure could potentially reduce or eliminate the physiological changes associated with 

microgravity, which include a spectrum of health issues: loss of bone-mineral density and the associated 

increase in renal stone risk; muscle atrophy; cardiovascular deconditioning; orthostatic hypotension; and 

sensorimotor and neurovestibular alterations, and perceptual illusions. 

AG and exercise combined with diet control and/or pharmacologic supplements might prove to be the optimal 

mitigation for certain health risks faced by crew on long-duration, exploration-class missions. In addition, AG 

would provide some benefit to life support systems: continuous or intermittent rotation would reduce the levels of 

floating particulates in the air, thereby reducing the risk of potential microbiological and/or toxicological hazards. It 

can also simplify the performance of common tasks that are complicated by microgravity (or other hypo-g 

environment), such as materials handling, surgery, sleeping, cooking, and excretory function. 

4.3 CURRENT LIMITATIONS

The lack of systematic research on AG raises significant questions on the appropriateness of AG for 

exploration-class missions that cannot be answered by speculation or theory alone. 

The following summarizes recommendations from the 1999 Artificial Gravity Workshop as to the most crucial 

actions required before any type of AG can be certified as an operational countermeasure: 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 4: Artificial Gravity 13 

1 Implement a rigorous research and development project to investigate rotational AG. The desired 

outcome should be a multi-system countermeasure against the detrimental health and performance effects 

of long-duration, exploration-class spaceflight. 

2 Determine optimal design characteristics for an AG countermeasure facility that will best promote human 

health and performance. 

3 Support the upgrade of existing ground and flight research sites and facilities as needed to perform 

fundamental activities. 

4 Promote community participation of and communication among experts from life sciences fields, human 

factors, international space agencies, mission and vehicle design, crew representation and training, and 

rehabilitation. 

More specifically, research is needed to fully characterize the physiological response to gravity environments 

between 0-g and 1-g and the cumulative effects of g-transitions. Optimal designs require data on the human 

response to varying characteristics of rotating AG environments (e.g., radius and angular velocity). Acceptable 

standards must be defined to maintain the level of operational performance required during and after flight, and to 

minimize irreversible changes likely to compromise the long-term health and safety of the crewmember. 

Indeed, the timeframe required to develop an AG countermeasure is rather significant. If we hope to apply 

AG during the next few decades of space missions, we need to begin human-subject studies on AG in space as 

soon as possible. An Earth-orbiting vehicle equipped with a short-arm centrifuge could be used to study the 

effects of rotating AG environments (from 0.38 to 1 g) on human physiology. Even smaller-scale experiments that 

employ the International Space Station (ISS) as a test bed would yield significant progress in understanding the 

design and operational parameters of AG. 

The following statement summarizes the current state of an AG countermeasure: 

While AG shows significant theoretical and intuitive potential as a multi-system countermeasure, 

considerable research and development effort is required before it can be considered for a 

complex, long-duration mission. 

4.4 DESIGN CONSIDERATIONS

A number of approaches have been considered for designing an AG countermeasure, each of which involve 

tradeoffs between amplitude (g level), duty cycle (how often and for how long), angular velocity, rotation arm, and 

other key variables. The following is an attempt to distill the key considerations and alternatives. 

One confounding factor of any rotational environment, whether constant or intermittent, is the so-called gravity 

gradient. The gravity gradient may cause untoward operational effects and significant discomfort to 

crewmembers. 

The physics of rotational AG mean that the gravity experienced by the crewmember varies directly 

with the distance from the center of rotation: a crewmember exposed to a 1-g vector in a 4-meter 

radius centrifuge could experience 1-g at the feet but only 0.5-g at the head. 

Intermittent AG 

One approach involves using a short-arm centrifuge to produce intermittent AG. With this approach, AG 

might be applied only during crew sleep time or as a means of human-powered exercise2

. But intermittent AG 

represents a significant unknown because it introduces a number of g-transitions between the desired level of g 

and the current ìambientî levels in the spacecraft or on the expedition surface, which may be marked by a host of 

adverse cardiovascular effects. For example, tests of other countermeasures using intermittent lower body 

negative pressure show that crews repeatedly experienced the malaise, facial edema, and other symptoms 

resembling postflight orthostatic hypotension (a condition that may result in fainting or near-fainting upon egress). 

Intermittent AG may produce similar problems, keeping the crew in an uncomfortable or even dangerous state of 

constant physiological adaptation. 

Continuous AG 

Continuous AG may also have drawbacks. We do not know how well the central nervous system can adapt 

to the constantly varying sensory stimuli introduced by this type of rotating AG. Coriolis forces created by rotation 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 4: Artificial Gravity 14 

give the illusion of angular motion (usually roll or pitch) whenever the head is moved outside the plane of rotation. 

In many subjects, this causes severe nausea and vomiting. Whether the effects would be eliminated over time as 

the subject adapts is unknown. Additionally, long-term exposure to continuous rotating AG may alter how a 

subject readapts to Mars or Earth gravity or to microgravity. 

4.5 REFERENCES

1 Diamandis P. ìCountermeasures and Artificial Gravity.î In Fundamentals of Space Life Sciences, Volume 1, 

Churchill S, editor. Malabar, Florida: Krieger Publishing Company; 1997. 

2 Meeker L and others. ìA human-powered, small-radius centrifuge for space application: a design study.î 

Survival and Flight Equipment Association Journal. 26 (1): 34-43. 1996 

3 Paloski W and Young L. ì1999 Artificial Gravity Workshop: Proceedings and Recommendations.î 

(unpublished). 

4 Smith M, Wercinski P, and others. ìA Conceptual Design Study of a Variable Gravity Spacecraftî in Space 

Exploration Projects Center Report. Moffett Field, CA: NASA/Ames Research Center. 1990 July. 

5 Stone R Jr. Report No. NASA-SP-314, ìAn overview of artificial gravity.î Presented at the Fifth Symposium 

on the role of the Vestibular Organs in Space Exploration. Pensacola FL: p 23ñ33. 1970 August. 

6 Vernikos J. ìArtificial gravity: intermittent centrifugation as a spaceflight countermeasure.î Journal of 

Gravitational Physiology 4(2):13-16. 1997 July. 

7 Young L. ìArtificial gravity considerations for a Mars exploration mission.î Annals of the New York Academy 

of Sciences 871:367-78. May 28 1999. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 5: Radiation 15 

5 RADIATION 

Radiation in the space environment remains one of the greatest risks to human health (this risk is further 

described in the Critical Path Roadmap). Crewmembers are exposed to two types of radiation: ionizing radiation 

and non-ionizing radiation. The radiation environment fluctuates considerably over time and location, meaning 

that the crew will likely require different protections or countermeasure approaches over the course of a longduration mission. 

5.1 KEY CONCEPTS

One definitive source for understanding the radiation environment and human-driven requirements is the 

MSIS. In addition, requirements for ionizing radiation received during space flight are set by the National Council 

on Radiation Protection and Measurements (NCRP). Limits for human exposure to non-ionizing radiation in 

space were modified from guidelines provided by the American Conference of Governmental Industrial 

Hygienists. 

Table 5.1 characterizes the key sources of radiation that affect human safety, health, and performance. More 

common examples of ionizing radiation include man-made sources of x-rays, nuclear reactors, and radioactive 

nuclides; and natural sources of galactic cosmic rays (GRC), solar particle events (SPE), and particles trapped in 

naturally occurring magnetic fields. Examples of non-ionizing radiation sources include infrared light, radio 

waves, and ultraviolet light (UV). 

Table 5.1: Characteristics of Radiation Sources in the Space Environment a

Form Source Sphere of Influence Frequency Description 

SPE Natural Outside vehicle, in 

space or on planetary 

surface 

Unpredictable but 

infrequent with 

high intensity 

Produced by dynamic solar 

events, such as solar maximum 

Trapped particles Natural Localized outside of 

vehicle 

Constant with 

moderate intensity 

Found within Earthís magnetic 

field, in polar regions, on other 

planetary surfaces, and in deep 

space 

Ionizing 

GCR Natural Ubiquitous and 

penetrating 

throughout universe 

Constant with low 

intensity 

Permeates the galaxy and moves 

with speeds approaching that of 

light 

Technology sources Artificial Inside vehicle Constant, low 

levels 

Derived from man-made 

equipment or devices 

Non-ionizing 

Solar UV Outside vehicle and 

inside through some 

windows 

Constant, relatively 

high levels 

Produced by solar corona 

a

 Adapted in part from Table 2.1: Sources of Space Radiation1. 

Ionizing radiation is of particular concern because it directly damages the genome when traversing the cell 

nucleus. It also indirectly damages the genome by producing free radicals and by transducing signals between 

adjacent cells within the body. 

! Acceptable risk: currently dose limits are designed to ensure less than 3 percent probability of excess 

cancer death; the ìas low as reasonably achievableî (ALARA) principle is used to stay well below these limits2,3

! Deterministic (non-stochastic) effects: physiological effects (e.g., acute radiation sickness, damage to 

central nervous system, or cataracts) of radiation exposure for which the severity is related to the level of 

exposure; that is, these occur only above dose thresholds2
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 5: Radiation 16 

! Stochastic effects: physiological effects (e.g., cancer, hereditary effects, or neurological disorders) for 

which the probability is related to the level of exposure and can occur long after a mission is complete; that is, 

probability of occurrence is proportional to dose received2

! Radiation dose: measure of energy absorbed by a unit mass of living tissue, expressed in grays (Gy) or 

rads (100 rad = 1Gy)2

! Linear energy transfer (LET): the energy loss rate or stopping power of a given radiation type that is 

one means of attenuating radiation; generally sources are defined as low-LET or high-LET2

! Relative biological effectiveness (RBE): ratio of radiation doses with different linear energy transfer, 

resulting in the same biological effect2

! Gray-equivalent: indicator of deterministic injury, where RBE x dose4

 = Gy-Eq 

! Quality factor (Q): an LET-dependent, defined protection quantity based on judgment of RBE for 

protection purposes2

! Dose equivalent (H): indicator of stochastic risk, where Q x dose2,4 = H, in units of Sv or rem (100 rem = 

1 Sv) 

5.2 NON-IONIZING RADIATION CONSIDERATIONS

The MSIS clearly defines the parameters that contribute to non-ionizing radiation exposure within the 

spacecraft (refer to the NASA Web site: 5.7.3.1 Design Considerations and 5.7.3.2.1 Exposure Limits), as shown 

in Table 5.2. Exposure of eyes and skin to the sun are limited for ultra-violet, ìblue light,î visible, and infrared 

wavelengths, as indicated in Table 5.3. Scientific experiments and observation through spacecraft windows 

impose technical specifications for color-balanced light transmission that permits high intensity of sunlight at some 

non-ionizing wavelengths. 

Table 5.2: Non-Ionizing Radiation Exposure Limits a

Frequency Range 

(MHz) 

Electric Field 

Strength 

(E) (V/m) 

Magnetic Field 

Strength (H) 

(A/m) 

Power Density (S) 

E - Field, H - Field 

(mW/cm2

) 

Averaging Time 

1⁄2E1⁄22, S or 1⁄2H1⁄22 

(minutes) 

0.003 - 01 61.4 163 (100,1 000 000)Ü 6 6 

0.1 - 1.34 61.4 16.3/ f (100,10 000/f2)Ü 6 6 

1.34 - 3.0 823.8/ f 16.3/ f (180/2, 10 000/ f 2)Ü f2/0.3 6 

3.0 - 30 823.8/ f 16.3/ f (180/2, 10 000/ f 2)Ü 30 6 

30 -100 27.5 158.3/ f 1.668 (0.2940000/ f 3.336)Ü 30 0.0636f1.337

100 - 300 27.5 0.0729 0.2 30 30 

300 - 3 000 f/1 500 30 

3 000 - 15 000 f/1 500 90 000/f 

15 000 - 300 000 10 616000/f1.2 

a From the American National Standards Institute Radio Frequency Protection Guides 

* The exposure values in terms of electric and magnetic field strengths are the values obtained by spatially averaging 

values over an area equivalent to the vertical cross-section of the human body (projected area). 

+ These plane-wave equivalent power density values, although not appropriate for near-field conditions, are commonly 

used as a convenient comparison with MPEs at higher frequency and are displayed on some instruments in use. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 5: Radiation 17 

Table 5.3: Limits for Exposure to Non-Ionizing Sunlight in Space a 

Mechanism Solar Irradiance Exposure Time Limit a

Retinal thermal 3 sec 

Retinal photochemical 5 sec 

Infra-red exposure 10 min 

Ultraviolet exposure 8 hr 

a

 From MSIS Figure 11.11.3.1.4-2 

5.3 IONIZING RADIATION CONSIDERATIONS

Regulatory requirements have been established for LEO operations to control stochastic and deterministic 

radiation effects2,4. The current limit of no more than 3 percent excess cancer death in crewmembers originates 

from comparisons to other occupational injuries and analogous populations.2,4 Currently accepted sex- and agedependent cancer risks limits are expressed in terms of dose equivalent.2

 On the basis of more recent cancer risk 

evaluations, the recommended limits (Tables 5.4 and 5.5)4

 have been greatly reduced for LEO operations. 

Deterministic effect limits pertain to three particularly sensitive tissue (ocular lens, skin, and blood-forming organs) 

over 30-day, annual, and lifetime periods.4.

All radiation protection measures and approaches must also adhere to the U.S. regulatory requirements: 

exposure must be ALARA. Mission planners and radiation personnel must demonstrate ALARA has been 

achieved in the designs used and the operations conducted in space.2,4

Unlike LEO, which is often dominated by trapped radiation, deep space exposure is dominated by GCR2,4-7. 

Currently, insufficient data exists on the biological effects of GCR, meaning that specific exposure requirements 

for deep space operations have not been established.2,4 The quantities and limits defined for LEO operations are 

normally used for all mission studies, but the scientific and regulatory communities can hardly be expected to 

retain these standards when concrete planning for BEO missions commences in earnest. 

Table 5.4: Recommended Organ Dose Limits for Deterministic Effects (All Ages) for LEO Operations 4

 

 Bone marrow (Gy-Eq)a Eye (Gy-Eq) Skin (Gy-Eq) 

Career -- 4.0 6.0 

1 year 0.50 2.0 3.0 

30 days 0.25 1.0 1.5 

a Gy-Eq or gray-equivalents 

Table 5.5: Career Effective Dose Limits a

Effective dose (Sv) Age at exposure 

Female Male 

25 0.4 0.7 

35 0.6 1.0 

45 0.9 1.5 

55 1.7 3.0 

a Limits are based on 3 percent excess lifetime risk of fatal cancer in LEO operations4

. 

5.4 UNCERTAINTIES IN EXPOSURE RISK ESTIMATES

Uncertainties in health risk estimates for space radiation are derived from several sources, the greatest of 

which is human health-risk data coming from the two detonations of nuclear weapons during World War II. 

Uncertainty for these data arises from the uncertainty in dosimetry, in statistics from the limited survivor 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 5: Radiation 18 

population, in projection of the fatal cancer risks over the lifetime remaining, and in relationship of these risk 

estimates for this population to other national/ethnic groups.5

 Further uncertainty enters in application of the highdose-rate risk coefficients to low-dose-rate exposures, the RBE for other radiation types, and the estimation of 

dose to specific tissues from space radiations for a specific mission. 

Detailed analysis has shown that the main limitation of shielding design for deep space results from 

uncertainty in applying the known risk coefficientsówith their own associated uncertaintyóto the space 

exposures and not the related evaluation of the exposure conditions.5

 The greatest uncertainty arises from the 

uncertainty in the RBE of different radiation types (or quality factor) while the remaining uncertainty in risk 

coefficients from other sources is comparable to uncertainty arising from estimation of LET-related dose 

contributions in specific tissues for the specific space shielding. 

5.5 RADIATION COUNTERMEASURES

No single method can completely protect crewmembers from the effects of space radiation. Thus, the overall 

approach consists of applying three methods: 

! Design, technology, and shielding: control the radiation reaching specific tissues through shielding and 

selection of exposure conditions. 

! Operational methods: control exposure based on individual sensitivity (currently age and gender), by 

judicious operational scheduling. 

! Biomedical countermeasures: control select symptoms through medical intervention or prevention. 

These must be implemented throughout the entire cycle of mission planning, shield design, operations, and 

biological treatment and controls. In the ensuing sections, these principles are considered in more detail. Table 

5.6 summarizes the results of a detailed analysis conducted to quantify the potential improvements in operational 

capacity that may result from adhering to these principles. Additional details may be found in the report ìSpace 

Radiation Cancer Risk Projections for Exploration Missions: Uncertainty Reduction and Mitigationî.5

Table 5.6: Estimates of Safe Days Gained in Space from Different Forms of Mitigation 5

Mitigation Approach Estimate of days gained Comment 

Improved risk assessment 200 - 400 days Cost-effective approach using data collection and research 

Shielding 50 - 300 days Light-mass materials identified; risk assessment data needed 

to improve approach 

Advanced propulsion 100 - 300 days Large advantage if achievable 

Crew selection 50 - 300 days Age, sex, and genetic selection not ethical; role of sensitivity 

to GCR not established at this time 

Biological countermeasures 0 - 1000 days Needs revolutionary research to achieve 

Solar cycle avoidance 100 - 200 days Reduces launch windows in order to decrease SPE threats 

Design, Technology, and Shielding 

Exposures can be reduced for specific missions through planning, technology choices, and shielding. As 

indicated in Table 5.6, a number of approaches are or should be available to limit radiation exposure to spacefaring crews. For example, limiting the launch windows to coincide with solar cycle variation reduces GCR 

exposure but introduces a rising risk of SPE exposure. Advanced propulsion systems might reduce the transit 

times. Shielding against the radiation environment involves the entire spacecraft, meaning that apparently simple 

design choices (e.g., aluminum structures as opposed to polymer composites) can have adverse effects on 

radiation exposures.7,8 Shielding during every aspect of the mission is necessary to assure crew safety, health, 

and performance. For example, the minimal protection afforded by spacesuits and rovers (due to mobility 

requirements) requires that careful attention is devoted to developing a shelter for SPE storms. 

Operational Methods 

The judicious scheduling of missions and activities may allow crewmembers to simply avoid exposure when 

levels are known to be high. In addition, the duration of exposure during high levels or rates should be minimized 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 5: Radiation 19 

to the greatest extent possible.5

 Second, monitoring the environment and making short-term predictions of 

radiation events is another important means. Personnel monitoring (such as cabin dosimeters or body-worn 

dosimeters) provides for cumulative tallying against career limits and may help guide medical treatment after an 

exposure.5

 

Biological Countermeasures 

Biological countermeasures for radiation must work for extended periods, be effective for high-LET radiations, 

and lead to minimal side effects. A combination of pharmaceutical radioprotectants, anti-oxidants, and enzymatic 

modifiers might reduce health risks.5,9-12 Other approaches that have been considered (but may not necessarily 

be adopted) include: 

! Select-out radio-sensitive individuals and select in radio-resistant individuals 

! Pharmacological protection (prophylactic or post-exposure) 

! Genetic therapy 

! Genetic modification and cloning (so-called designer crews, which may surpass ethical limits) 

5.6 FUTURE DIRECTIONS

Providing adequate radiation protection for crews on long-duration missions outside of Earthís 

protective magnetic field is a major challenge to NASA, for which no effective and affordable 

solution has been found. 

In the following paragraphs, we suggest advances that can drive the capability of radiation protection forward. 

An increased commitment to research and testing of mitigation techniques is required to enable mission scenarios 

beyond LEO. 

Design and Shielding Technologies 

Shielding affects the entire vehicle and habitat designs: space radiation interacts with all structures and 

equipment, modifying the radiation to which humans and devices in the interior are exposed. To perfect efficient 

and affordable shielding, all human-rated structures must be approached with a radical perspective on design 

development.7,8 

In the past, materials research has focused on requirements for functional use (e.g., high mechanical strength 

per material mass) without regard to the property of radiation protection per material mass. Adding this criterion 

requires a new multi-functionality. Also implied in this multi-functional approach is the need for new design 

methods, in which multiple disciplines are addressed in the design process and emphasizes the need for 

multidisciplinary optimization (MDO) processes including radiation-shielding requirements. The parameter space 

in the design process will reveal that MDO solutions are radical departures from conventional approaches. 

Increased emphasis on MDO processes will place requirements on tools for shield analysis. Concomitant to 

the development of such tools is experimental testing of required databases and computational methods to 

validate solutions. High fidelity physics-based models, along with ample model validation in laboratory test 

facilities (including the Booster Application Facility and Alternating Gradient Synchrotron at Brookhaven National 

Laboratory, and the proton accelerator of the Loma Linda University), will become increasingly important as well. 

Operational Methods 

Temporal variations in the space radiation environment have been and can be used to reduce the crew 

exposure. Operational solutions include: 

! Improved propulsion systems that limit transit time for crews 

! Protective spacecraft design 

! Shielded habitats 

! Personal shielding 

GCR, the primary constraint on planning deep space operations, is reduced in magnitude during periods of 

maximum solar activity, thus reducing the need for shielding of crew areas. 

While GCRs are reduced, the probability of a SPE increases. SPEs are sporadic, lasting only a few hours or 

days, so that crew exposure can be minimized with a limited-volume shelter. Unfortunately, the mass of such a 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 5: Radiation 20 

shelter would be quite large. Many have suggested that the water reservoir for the spacecraft could serve as this 

shielding material, but the mass required to protect against a SPE (based on the largest event in recent history) 

would be very great indeed. The potential disadvantage of a SPE shelter is that it may not be readily accessible 

during certain mission events, such as EVA or surface exploration. In this case, the limiting factor is the time 

required to reach the shelter and the availability of timely warning systems. Even an adequate warning system 

may allow only1to 2 hours to seek shelter within proscribed radiation exposure limits; any advance in warning 

systems would permit a larger range of human exploration activities. 

The largest SPEs are associated with coronal mass ejections (CME). Providing an effective early warning 

capability, alarm system, and shelter would nearly eliminate any threat from SPEs. Future sensors should detect 

shock acceleration from a CME, providing up to about 8 hours warning before the shock wave arrives at human 

operation areas. Clearly, the predictability of SPE radiations is in need of continued research and development. 

Biological Countermeasures 

Genetic variability will play an important role in understanding risk estimates and in development of biological 

countermeasures. Many mechanisms underlying mutation, repair, and cell signaling have now been elucidated. 

The relatively new analysis technique employing gene microarrays will now permit scientists to study the 

expression of literally thousands of genes and their role in the genetic response to radiation. Bioinformatics 

methods now in development will allow expedient analysis of microarray data. Individual differences will also be 

important in the development of biological countermeasures and for understanding their potential effectiveness. 

Important ethics issues will need to be addressed in the future to determine how such knowledge can 

appropriately be applied for human space flight. 

5.7 REFERENCES

1 Letlaw J. ìRadiation Biology.î In Fundamentals of Space Life Sciences, Volume 1. Churchill S, editor. 

Malabar, Florida: Krieger Publishing Company; 1997. 

2 NCRP Report No. 98, ìGuidance on Radiation Received in Space Activities.î Washington DC: NCRP; 1989. 

3 NCRP Symposium Proceedings No. 3, ìAcceptability of Risk from RadiationóApplication to Human Space 

Flight.î 1996. 

4 NCRP Report No. 132, ìRadiation Protection Guidance for Activities in Low-Earth Orbit.î 2001. 

5 Report No. JSC-29295, ìSpace Radiation Cancer Risk Projections for Exploration Missions: Uncertainty 

Reduction and Mitigation.î 

6 ìHZE: Particle Effects in Manned Space Flight.î National Academy of Sciences. 1973. 

7 Wilson JW, Miller J, Konradi A, and Cucinotta F. Shielding Strategies for Human Space Exploration. NASA 

CP-3360. 1997 December. 

8 ìIssues in Deep Space Radiation Protection.î Acta Astronautica 49: 289-312. 2001. 

9 Space Radiation Health Project, NASA JSC. 2000. 

10 Strategic Program Plan for Space Radiation Health Research, NASA Publication. 1998. 

11 Space Radiation Health Project, ìBiomedical Research and Countermeasures Program Implementation Plan,î 

NASA JSC. 1998. 

12 Space Studies Board. ìReview of NASA's Biomedical Research Program.î Washington DC: National 

Academy Press. 2000. (Available on the NAP Web site: 

http://www.nationalacademies.org/ssb/biomedmenu.htm) 

13 Space Studies Board. ìRadiation and the International Space Station: Recommendations to Reduce Risk.î 

Washington DC: National Academy Press. 2000. 

14 NASA/LBNL #40278: Modeling Human Risk: Cell and Molecular Biology in Context. 

15 Space Studies Board. ìRadiation Hazards to Crews of Interplanetary Missions.î Washington DC: National 

Academy Press. 1996. (Available online: http://www.nationalacademies.org/ssb/besrmenu.html) 

16 ìRadiation Protection Guides and Constraints for Space-Mission and Vehicle-Design Studies Involving 

Nuclear Systems.î Washington DC: National Academy Press. 1970. 

17 ìRadiobiological Factors in Manned Space Flight.î Washington DC: National Academy Press. 1967. 

18 Home page for the JSC Space Radiation Health Project http://srhp.jsc.nasa.gov/. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 6: Routine and Emergency Medical Care 21

6 ROUTINE AND EMERGENCY MEDICAL CARE 

Since the earliest orbital flights, space medicine has been tasked with ensuring a successful mission in which 

the crew returns safely to Earth. A successful mission relies on three interdependent elementsóthe spacecraft 

system, the human, and the environmentóeach of which are driven by the central objective of crew safety, 

health, and performance. 

Function of the human in the space flight environment is a continuum that begins with stringent selection, 

training, and preflight monitoring of the crew, is followed by comprehensive inflight monitoring and intervention as 

needed, and is completed with postflight monitoring and rehabilitation. The environmental element is closely 

related to that of the crew and takes into account both internal and external monitoring factors [cite relevant 

chapter]. 

These responsibilities encompass both the routine medical event that may occur during the course of a 

normal mission and the emergency care necessitated by an accident or other mission contingency. Elements of 

this specialty include medical monitoring and certification, health maintenance and countermeasures, medical 

intervention, psychosocial support, and environmental health monitoring. As a result, needs for medical 

equipment, crew training, and ground support are considerable; these are greatly influenced by the mass, volume, 

and power restrictions of the flight environment, since standard terrestrial clinics rely on a suite of bulky, resourceintensive diagnostics and therapeutics. 

6.1 KEY CONCEPTS

! Countermeasure: any preventive or mitigating measureówhether a form of exercise, a drug or 

nutritional supplement, or a more complex mechanical deviceóthat addresses the most severe physiological and 

psychological risks of human spaceflight. 

! Countermeasures system: one element of the on-board health care system that is prescribed by flight 

surgeons for counteracting the most detrimental psychological and physiological effects of microgravity (refer to 

Chapter 4 on Artificial Gravity, for a detailed discussion of this one approach)

! Crew medical officer (CMO): one or more members of a crew that are designated as the lead for 

managing any medical issues that may arise in flight; the CMO currently receives up to 18 hours of medical 

training, comparable to that received by an emergency medical technician

! Environmental health system: one element of the on-board health care system that permits crew or 

ground personnel to monitor microbial and chemical contamination of the atmosphere and water, and the 

radiation environment 

! Health maintenance system: one element of the on-board health care system that provides: 

- In-flight preventive, diagnostic, and therapeutic medical care 

- Patient stabilization and transport for serious medical situations 

! Medical event: occurrence of significant illness or injury, normally requiring evacuation, emergency room 

visit, or hospital admission (as applied to the operational environment) 

! Space medicine: the program of comprehensive health care necessary to ensure a safe, healthy, and 

productive crew; a successful mission; and prevention of detrimental mission and long-term health consequences 

Figure 6.1 shows how space medicine relies on many disciplines to meet its objectives. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 6: Routine and Emergency Medical Care 

FLIGHT MEDICINE 

CLINICS

ï Opthalmologyï Dentalï Primary careï Specialistsï Health stabilization

FLIGHT MEDICINE 

CLINICS

ï Opthalmologyï Dentalï Primary careï Specialistsï Health stabilization

MANN

SU

ï Neutral Bï Physiologï Chamber ï KC-135 (p

MANN

SU

ï Neutral Buï Physiologï Chamber ï KC-135 (p

PSYCHOLOGICAL AND 

PSYCHIATRIC 

SUPPORT

ï Testingï Monitoringï Trainingï In-flight support

PSYCHOLOGICAL AND 

PSYCHIATRIC 

SUPPORT

ï Testingï Monitoringï Trainingï In-flight support

D

ï EMS laun

support

D

ï EMS laun

support

PHYSICAL TRAINING

ï Preflight trainingï In-flight exerciseï Postflight 

rehabilitation

PHYSICAL TRAINING

ï Preflight trainingï In-flight exerciseï Postflight 

rehabilitation

CLINIC

CAP

DEVE

PR

ï Technolo

identificatdevelopm

ï Exploratio

planning

ï Telemediï Mission s

CLINIC

CAP

DEVE

PR

ï Technolog

identificatidevelopm

ï Exploratio

planning

ï Telemedicï Mission su

MISSION SUPPORT

ï Procedures (Flight data file)ï Flight controlï Flight rewuirementsï Launchand landingï Mission Control ñ Houstonï Mission Control - Moscow

MISSION SUPPORT

ï Procedures (Flight data file)ï Flight controlï Flight rewuirementsï Launchand landingï Mission Control ñ Houstonï Mission Control - Moscow

TRAINING

ï Flight controlï Crew trainingï Studentsï Simulationsï Computerized onboard training

TRAINING

ï Flight controlï Crew trainingï Studentsï Simulationsï Computerized onboard training

SMMaC PROJECT

ï Monitoring and 

countermeasures development and verification

ï Integrated product teams

SMMaC PROJECT

ï Monitoring and 

countermeasures development and verification

ï Integrated product teams

EPIDEMIOLOGY

ï Longitudinal Study of 

Astronaut Health

ï Data managementï Analog studiesï In-flight studies

EPIDEMIOLOGY

ï Longitudinal Study of 

Astronaut Health

ï Data managementï Analog studiesï In-flight studies

SYSTE

LO

ï Crew Hea

Systems 

ï Shuttle O

System (S

ï Flight pro

integratio

SYSTE

LOG

ï Crew Hea

Systems (

ï Shuttle Or

System (S

ï Flight proj

integration

ENVIRONMENTAL 

HEALTH

ï Preflight testingï In-flight monitoringï Toxicologyï Water and foodï Radiation

ENVIRONMENTAL 

HEALTH

ï Preflight testingï In-flight monitoringï Toxicologyï Water and foodï Radiation

CREW 

SELECTION

ï Screeningï Testingï Evaluationsï Standards

CREW 

SELECTION

ï Screeningï Testingï Evaluationsï Standards

LABORATORIES

ï Biochemistryï Circadian shiftingï Cardiovascularï Bone and muscleï Neurophysiologyï Pharmacologyï Microbiologyï Clinicalï Exerciseï Nutritionï Immunologyï Behavior and performance

LABORATORIES

ï Biochemistryï Circadian shiftingï Cardiovascularï Bone and muscleï Neurophysiologyï Pharmacologyï Microbiologyï Clinicalï Exerciseï Nutritionï Immunologyï Behavior and performance

Comprehensive health care necessary to 

ï enable a healthy and productive crewï ensure mission successï prevent/mitigate long-term negative health 

consequences

Figure 6.1: Elements of Space Medicine 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 6: Routine and Emergency Medical Care 23

6.2 RATES OF INCIDENCE

While the US space flight program has rarely, if ever, been compromised by a medical event during flight 

such an occurrence is indeed likely. 

The probability of significant illness or injury occurring during future human missions is high. These estimates 

even exclude the singular dangers of the space environment, such as radiation exposure, immune system 

depression, and untoward physiological adaptations. 

The probability of significant illness or injury occurring during a 2.5-year mission with 6 crew is 

about 0.9 incidents per mission ― nearly every mission will be confronted with such an event. 

If we use the same datasets to estimate the number of events requiring intensive care, again ignoring the 

untoward effects of the spaceflight environment itself, the probability that such an event will during a Mars mission 

is about one incident for every three missions. Undoubtedly, the effects of the spaceflight environment itself will 

increase these rates. 

Analog Medical Data 

In fact, analysis of illness and injury rates for analog populations (e.g., data from astronaut longitudinal study, 

submarine crews, Antarctic winter-over, and military aviator) reveal that a medical event during a mission is 

increasingly probable. These analog populations are a very valuable source of data because flights generally 

involve a small population and corresponding limitations on medical data. Detailed analyses (unpublished) reveal 

that analog populations do represent many of the physiological and psychological conditions faced by 

crewmembers, with some exclusions as described in the footnotes. 

Nonetheless, analog populations furnish an important source of data on the types and rate of incidence for 

illness or injury that might be expected during a human space mission. Table 6.1 shows a ranking of all medical 

events or complaints compiled from over 20 years of analog data. 

Table 6.1: Ranking of Medical Events or Complaints from Analog Data a12

1 Injury and toxic exposure (poisoning) 

2 Digestive system 

3 Musculoskeletal 

4 Respiratory 

5 Mental disorders 

6 Signs and symptoms (ill defined) 

7 – 9 (tie) Infectious / Circulatory / Genitourinary 

10 Skin and subcutaneous tissue 

11 Nervous system and sense organs 

12 Neoplasms 

13 Endocrine / Metabolic / Nutritional and Immune 

14 Blood and blood forming organs 

a Unpublished data from Billica et al. 

 

1 Expect less musculoskeletal-related injuries in space because analog environments have increased exposures (cold, 

numbers of people, injury risk, etc.) 

2 Expect increased skin and circulatory injuries, and possible metabolic/nutritional/immune events in space because it has 

increased hazards (microgravity, closed environment, radiation, age of crew, etc.) not found in analogous environments. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 6: Routine and Emergency Medical Care 24

Crew Medical Data 

Medical data from human space flight is equally instructive, despite the markedly smaller population size. 

Analysis of medical complaints recorded during 89 Shuttle missions (1981 ñ 1998) and covering 508 total 

crewmembers during 4443 cumulative flight days reveals that an overwhelming majority of any space-faring crew 

will experience some change in performance, even if it relates to normal physiological adaptation: 

! 79 percent reported space motion sickness 

! 98 percent reported some medical symptom: 

- 67 percent reported headache 

- 64 percent reported respiratory complaints 

- 59 percent reported facial fullness 

- 32 percent reported gastrointestinal complaints 

- 26 percent reported musculoskeletal complaints 

Both space flight and analog data analyses inform current estimates of incidence for the ISS and future 

missions. 

Despite every possible attempt to minimize the risks of human space flight, the flight environment remains a 

hostile one for human beings. Microgravity itself brings considerable physiological effects, including space motion 

sickness (SMS), neurovestibular effects, bone mass loss, cardiovascular deconditioning, musculoskeletal 

deconditioning, and psychological effects. The cabin environment may expose crew to hypoxia, decompression, 

toxic releases, extreme temperatures, radiation, and so on. Confinement, isolation, a difficult workload, stress, 

danger, and noise can create difficult psychosocial adaptation problems. Medical emergencies may include 

burns, trauma, cardiac life support, infection, food poisoning, and a host of other injuries. 

Each mission must address and be prepared to manage a wide spectrum of medical concerns during mission 

operations, including medical events affecting mission timeline or objectives; damaged spacecraft or injured/ill 

crew; catastrophic events affecting vehicle integrity and crew survival and Class 1 alarms (fire, toxic atmosphere, 

cabin depressurization). 

6.3 EMERGENCY CARE

The practice of emergency medicine in space is confounded by severe restrictions on vehicle and personnel 

resources. Current medical operations rely on non-physician crewmembers with minimal medical training and 

experience, who are supported by extensive communications with Earth-based medical personnel. Thus, the 

alternatives become (1) stabilization of the injured crewmember to allow medical evacuation or (2) complete 

diagnosis, treatment, and rehabilitation (also known as the ìstand and fightî concept). 

Medical Evacuation 

Medical evacuation from orbit is not unprecedented. In 1976, the Salyut 5 station was abandoned 49 days 

into a 54-day mission for intractable headaches; on Salyut 7 in 1985, a medical evacuation occurred 56 days into 

a 216-day mission for sepsis/prostatitis; and in 1987, there was a medical evacuation from Mir 6 months into an 

11-month mission for cardiac dysrhythmia. There have been several missions where various conditions did not 

result in medical evacuation, but could have: spacecraft fires in 1971, 1977, 1988, and 1997; a possible kidney 

stone in 1982; hypothermia during EVA in 1985; psychological stress reaction in 1988; spacecraft 

depressurization in 1997; and a toxic atmosphere in 1997. Other medical events in the US space program 

include a rescheduling of an Apollo 9 EVA due to medical causes, Type 1 decompression sickness in the 

command module pilot during the Apollo 11, a urinary tract infection during Apollo 13, a cardiac dysrhythmia 

during and after a lunar EVA during Apollo 15, and chemical pneumonitits due to nitrogen-tetroxide inhalation on 

reentry during the Apollo-Soyuz Test Project. 

On-board Care 

Any complex interplanetary mission generally eliminates the option of medical evacuation to Earth. Instead, 

the focus of an emergency medical system becomes autonomy, intelligence, and reliability. The transition to 

missions of increasing distance or to more dangerous operations, such as significant "hard-hat" construction in 

space, intensifies the need for autonomous emergency medical care. A crewed mission to Mars, for example, 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 6: Routine and Emergency Medical Care 25

would be beset by communication delays of up to 40 minutes round trip: in such a scenario emergency support 

from the ground is not feasible. 

6.4 DESIGN CONSIDERATIONS

Planning and designing all the elements of a crew health care system for a long-duration mission is extremely 

difficult due to the large number of medical conditions that might occur. A problem may present across all or 

several crewmembers, and any number of problems may occur repeatedly during a mission. For this reason, 

ìtraveling lightî on a future Mars or Moon mission is just not feasible. 

For a Mars-type mission, the minimum mass of a crew health care system for a habitable vehicle 

is estimated to be at least 1,000 kg (approximately 2,205 lbs) for equipment and 500 kg 

(approximately 1,102 lbs) for consumables, with a total low-estimated volume of 4 m3

(approximately 141 ft3). 

A lunar base would need to be similarly stocked, although the possibility for an evacuation to Earth should 

reduce the mass and volume slightly. 

Consider the complexity and resource-intensive nature of a terrestrial emergency room, in which a team of 

doctors, nurses, laboratory technicians, pharmacists, radiologists, and pathologists work in concert with an 

extensive suite of medical equipment to diagnose and treat critically ill or injured patients. During current ISS 

expeditions, the crew of three includes up to two CMOs who have received medical training equivalent to that of 

an emergency medical technician. Future missions, which may benefit from a larger crew, will still be confounded 

by limited medical training and clinical experience, along with severe resource limitations to diagnose, treat, and 

rehabilitate a fellow crewmember. Even an exploration-class crew possessing all of the relevant mission-critical 

skills (mechanical and electrical engineering, geology, astronomy, etc.) will also have to handle medical 

emergencies of all sorts under extremely stressful conditions. 

Clearly, the resource-limited environment of space flight means that the operational concept for on-board care 

must substitute careful planning and innovation for the many resources of a terrestrial care setting. Vital 

decisions must be made quickly, with little forgiveness for error. To complicate matters, all equipment and 

supplies in a ìspace hospitalî must be stowed in the tightest configuration possible to maximize the available 

space and ensure safety in microgravity, unlike a hospital emergency room where equipment and supplies are 

readily at hand, powered up, and in a high state of readiness. 

6.5 MEDICAL TECHNOLOGIES AND INVENTORY

Crews on long-duration missions will clearly need the support of intelligent medical systems as they attend to 

both routine and emergency medical needs. In this scenario, intelligent systems act as physician-equivalent 

helpers or they can provide logistical support during routine care. Below are examples of various technologies 

required to create such intelligent medical systems: 

! Visual programming shells/interfaces for knowledge capture: allow physicians and other medical 

experts to transfer their knowledge for computer-based training and databases, diagnostic aids, decision-support 

tools, medical protocols, multimedia training, and other support systems); 

! Team coordination/management protocols: use of linked palmtop computers or other means to 

ensure adequate emergency medical response; 

! Rapid data entry and comparison: allows comparison of data with existing records for rapid diagnostic 

support, allowing more natural, simpler access or interaction with medical knowledge; 

! Data visualization techniques: provide large amounts of complex medical data that is easy to 

understand and manipulate, allowing questions about the data to be easily and intuitively investigated in an 

interactive fashion; 

! Physiological simulation models: support development of protocols and procedures for emergency 

medical response; 

! Detailed individual physiological models: guide protocol for the administration of pharmaceuticals and 

assist prediction of treatment effects; 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 6: Routine and Emergency Medical Care 26

! Real-time decision support and “just-in-time” training tools: unobtrusive means that permit 

emergency treatment by non-physicians crewmembers; 

! Intelligent tutoring applications: tools that assist the development of on-board medical training for 

long-term missions, especially those that use a multimedia case-study approach; and 

! Automated systems for delivering aspects of emergency care: guidance or completion of select 

medical tasks that allow crewmembers to attend to other tasks. 

The health care system for supporting a crew on a 2.5-year mission to Mars would require extensive inventory 

and availability of numerous medical consumables. In addition to more commonplace diagnostic and treatment 

equipment and countermeasures included in the current systems, the future system would rely on cutting-edge 

tools (including software, hardware, and consumables) to guide a crew with limited medical knowledge and to 

minimize or eliminate invasive procedures, as outlined below: 

! Noninvasive, in-vivo biosensors and clinical laboratory equipment for monitoring blood chemistry (e.g., 

calcium ions, electrolytes, proteins, lipids, and hormones as well as cellular components); 

! Real-time, in-vitro biosensors and clinical laboratory equipment for monitoring bodily fluids and exhaled 

gas chemistry; 

! Implantable/injectable/ingestable biomedical sensors; 

! Pharmaceuticals with a long shelf-life (approximately 3 years) and/or the capability to produce 

pharmaceuticals during the mission; 

! Telemedicine systems for orbital and near-Earth or -Moon consultation and mentoring; 

! Laboratory diagnostic equipment (e.g., clinical chemistry, hematology, pathology, microbiology, 

hematology, and endocrinology); 

! Imaging diagnostics equipment (e.g., radiographic, magnetic resonance, and ultrasound); 

! Minimally- or noninvasive monitors (e.g., electrocardiograph, blood pressure, oxygen saturation); 

! Equipment and protocols for inflight diagnostic equipment using minimal consumables (cytometer, 

delayed-type hypersensitivity testing (ìskin testî), Enzyme-Linked Immunoassay (ELISA) system, blood collection 

and distribution, and a cell culture and challenge system); 

! Equipment and protocols to provide rescue, resuscitation, stabilization, and transport; 

! Fluid therapy systems including infusion pumps, on-site production of sterile fluids, nutritional support, 

blood and blood component replacement. 

! Medical waste management system; 

! Advanced medical storage systems for samples, pharmaceuticals, and other perishable items; 

! Microsurgery/microtherapeutics equipment and protocols; 

! Methods for monitoring the radiation environment and dose received (e.g., active, solid-state, bio-, and 

personal dosimetry); 

! Radioprotectants and methods for monitoring pharmacological treatments for radiation exposure; and 

! Methods for real-time, autonomous monitoring of air, water, and food for microbial and chemical 

contamination. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 7: Psychosocial Interaction 27

7 P S Y C H O S O C I A L I N T E R A C T I O N 

Human exploration crews of the future will be beset by a multitude of challenges that affect their performance, 

including transitions between g environments, isolation and confinement, significant crew autonomy, significant 

lag times for communication to Earth, increased exposure to the physical environment (especially radiation), and 

decreased perceptual stimulation. 

Although we are gaining experience with long-duration crew deployments in LEO (with Shuttle-Mir and ISS), 

we know little about maintaining a long-duration presence beyond LEO. To some extent, Earth-based analogs 

(e.g., nuclear submarine deployments, Antarctic missions, and naval research vessels) identify and address crew 

performance issues expected during long-duration missions (refer to Chapter 6 for a comparison and contrast of 

analog populations). These analogs have shown that increased isolation and confinement typically result in 

increased crew psychological and social problems; following is a brief description of these issues. 

7.1 CREWMEMBER PERFORMANCE

Crewmember performance can be compromised by many aspects of the mission, including: 

! Microgravity-induced neutral body posture; 

! Physical and biomedical changes; 

! Sleep-wake cycles and sleep deprivation; 

! Work schedules; 

! Isolation and confinement; 

! Metabolic costs of EVA; and 

! Space adaptation sickness (SAS), although this should occur during the initial transition into a different 

gravity environment and will diminish over time. 

Scheduling 

Experience with Skylab, Mir, and ISS shows that precisely choreographed schedules for crew work can be 

problematic during long-duration missions and can be exacerbated during interactions with mission control 

personnel. The present approach for ISS is to use standard duty schedules that permit regular personal time and 

rest days. Other important considerations for crew scheduling include: 

! Balance both overload and underload of crew schedules; excessive workload results in stress, fatigue, 

attention deficits, and decreased motivation. 

! Institute In-flight refresher training and performance assessment during the long en route portion of the 

mission. 

! Consider rotating duties to maintain crew skills and to decrease boredom. 

! Most importantly, the crew should have some authority to determine or modify their own schedules 

Quality of Sleep 

Sleep disturbances (primarily insomnia and decreased sleep quality) have often been reported in confined 

environments. Even with moderate sleep and disruption of normal circadian rhythms, concentration, vigilance, 

decision-making, motivation, and skilled performance decrease. Spacecraft design (e.g., noise, vibration, 

illumination); habitability (e.g., private crew sleep areas), operations (e.g., disruptive communications with mission 

control), and work cycle design should support ìnormalî sleep periods to prevent disruption of circadian rhythms. 

Provide zeitgebers (the external physical, temporal, and social cues that regulate circadian rhythms) to regulate 

crew internal clocks. 

7.2 CREW INTERACTION

Exploration missions in particular will require a high degree of group cohesion and cooperation. Individual 

crewmembers will need strong interpersonal skills, given the requirement to live and work together in a small, 

confined environment for long periods. Traditionally, crew selection has focused on individuals with strong 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 7: Psychosocial Interaction 28

technical skills and competence; in addition, individual personality characteristics must be emphasized. Crew 

interactions relate to issues associated with overall crew functioning and compatibility, including crew size, 

gender, age, culture, competence, and leadership. 

Culture 

Human missions will most likely continue to be composed of an international crew. No culture-based 

problems are expected since individuals will continue to be selected from a specific subset of the population and, 

therefore, will have common ground. Provisions may be required to accommodate special cultural needs of 

particular crewmembers, but the entire crew should be expected to conform to a single culture; nonetheless, an 

official mission language must be selected and all crewmembers must receive training to be proficient in that 

language. 

The entire crew should perform mission training together for enough time to allow cultural differences to be 

addressed prior to departure. During the mission itself, all crewmembers should have equal status based upon 

crew position and not on national origin. 

Focus crew selection on individuals with characteristics that lend themselves to group cohesiveness and 

cooperation. In addition to a strong task and team orientation and high-perceived competence, individuals should 

demonstrate strong social and interpersonal abilities and have introversion/extroversion balance. Pay particular 

attention to selecting the leader: the leader of the first space expeditionary force must have both strong leadership 

abilities and superior interpersonal skills (mature, competent, and experienced rather than ìaction-orientedî). 

Crew Performance 

Crew performance, as distinguished from the performance of an individual crewmember, relies on the 

formation and maintenance of a cohesive team that extends over multiple years of training and continues for the 

duration of the mission. 

 A number of factors affect crew team performance: the knowledge, skills, attitudes, motivation, performance 

strategies, and personality characteristics of individual crewmembers; group factors (e.g., size, cohesiveness, 

leadership); and environmental factors (e.g., mission tasks, risks). Important considerations for mission designers 

include built-in training approaches: 

! Train all crewmembers to identify and manage conflicts and stress during the mission. 

! Train the crew to protect against ìgroupthink,î a situation in which maintaining group harmony prevents 

critical thinking. Groupthink may lead to poor or unsafe decisions, which are of particular concern because 

outside communications are so restricted. 

! Train crews in cockpit resource management (CRM) methods; individual crewmembers must behave 

assertively for the protection of the entire team, including questioning a leaderís decision. 

7.3 COMMUNICATIONS

The isolation, confinement, and distances of long-duration missions yields unique communications issues. 

Distance will prevent real-time communications, so procedures are required to regularly communicate important 

information in a store-and-forward fashion. Examples of store-and-forward communications include periodic 

computer-to-computer transmissions and scheduled crew tapings for public outreach. 

Direct crewmember-to-crewmember communication also changes: microgravity and the artificial atmosphere 

alter speech, and fluid redistribution alters communication cues such as facial expression and body position. 

Equipment noise within the cabin also interferes with communications (refer to Chapter 11 on Crew Environment, 

section 11.2). Given the circumstances of a human exploration mission, electronic communication will take on 

added significance. 

Communications difficulties between the crew and mission control will be exacerbated; the isolation and 

confinement of missions often mean that crew frustration is directed toward ground personnel. The design 

considerations listed below, along with established, formal, and structured protocols will address some of these 

problems; crew and ground controller training can offset potential problems. 

In summary, communications must provide regular access to the crew without constant intrusion or 

interference with onboard operations. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 7: Psychosocial Interaction 29

Design Considerations 

! Communications should include full-motion video, audio, and computer-based modes. 

! New video compression techniques are required to provide error-free transmission of "TV-like" video 

quality. Recent advances in optical communications require further refinement before they can be integrated into 

planning for future human missions. 

Transmitting quality video is a significant requirement, necessitating robust communication 

systems. Overcoming the considerable transmission distances of exploration missions in turn 

affects spacecraft power, mass, sizing, and operations.

! Audio communication has fewer transmission demands than video. Synchronized audio and video are 

nonetheless required. Extend existing systems to accommodate this requirement. 

! Regular computer-to-computer transmissions (e.g., email, burst, text, graphics, telemetry) will be required. 

Consider an autonomous communications system. 

! Crew-family and crew-medical communications that are both secure and regular are required. 

! Regular near real-time crew communications are required for public outreach and education, in which the 

crew shares their experiences. 

! Regular communications between the crew and scientists on earth are required, especially during surface 

operations. Consider allowing direct access between a ground-based ìscience teamî representative and the 

onboard science officer. 

7.4 EMERGENCIES AND CRISES

Danger is inherent in the space environment and is particularly relevant to an exploration mission, where 

unique emergencies or crises ñ some severe and life threatening ñ may arise from external or crew-related 

issues. The individual response to external threats includes both generalized physiological reactions and 

individual responses. Beyond a certain level, however, the response impairs performance and training becomes 

critical. Training provides skills to reduce specific threats and to provide effective responses to threat situations; 

specific coping strategies can also be learned. Considerations for individual and team performance during an 

emergency or crisis include: 

! Consider modifying crew selection criteria to include specific personality characteristics that are stressadaptive. When selecting the crew commander, consider leadership behavior during a crisis. 

! Address the team response to threats with comprehensive training and simulation. 

! Remember that an internal threat, perhaps imposed by a crewmember, is also possible. Psychological 

disturbances increase during long-term confinement and isolation, while negative events on Earth may trigger 

depression or grief. Decisions are required to determine when and how events on Earth should be communicated 

to a crewmember. 

! Prevent potential psychological problems; when required, intervene effectively. Prepare the crew to 

recognize and understand possible psychological problems they may experience. Likewise, give them training in 

generalized stress reducers (e.g., meditation, relaxation, biofeedback) and in the value of regular exercise. 

- Train the mission commander in crew behavior assessment and intervention techniques. 

- Train the crew medical officer in psychological intervention and countermeasures. 

- Train crewmembersí families to increase their sensitivity to psychological issues; provide regular 

support and counseling to them during the mission. 

! Consider the possible death of a crewmember during the mission, which would require the remaining 

crew to manage both psychological and physical demands. Define procedures to manage this event, using the 

experience of analog populations (e.g., Navy vessels at sea; Antarctic during winter-over) as a guide. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 7: Psychosocial Interaction 30

7.5 CREW STRUCTURE AND AUTHORITY

The crew should be directly involved in formulating mission plans. Organizational structure and authority 

within and between the crew and other organizations must be addressed. 

Leadership is formalized and is based on the perceived competence of the leader with formal supporting 

roles. The mission commander will undoubtedly be selected from the ranks of experienced crewmembers, but 

allowing crewmembers to nominate mission commanders is a valuable approach. 

Authority is often shared on space missions between mission control-based personnel and the onboard crew. 

The long distances associated with exploration missions may make this difficult; onboard centralization of 

authority and crew autonomy should be increased, with ground-based personnel focusing on long-range issues. 

Crew Work Roles 

Crew work roles also influence crew structure. Crew roles should be evaluated and defined specifically for 

each mission. Consider assigning complementary roles or functions to a crewmember, without introducing task 

overload. The four functional crew work roles are: 

! Flight operations (e.g., mission command; guidance, navigation and control; flight engineering; systems 

management; communications) 

! Scientific investigation (e.g., data collection, analyses, mission science goals): although not essential to 

mission completion, science tasks may be the primary justification for an exploration-class mission. 

! Environmental support (e.g., vehicle and habitat maintenance, logistics management): with a small 

crew, these roles can be combined with flight operations responsibilities. 

! Crew support (e.g., medical operations) 

7.6 RE-ASSIMILATION ON EARTH RETURN

An exploration crew must remain together for five or more years through initial selection, mission training, and 

the mission. When the mission is completed and the crew returns to Earth, each individual will need to be reassimilated into the life left behind; the separation imposed by the mission and the subsequent re-assimilation can 

be disruptive to the crewmemberís family. The following considerations will ease the re-assimilation of exploration 

crewmembers 

! When selecting the exploration crew, types of familial characteristics must be considered (e.g., should 

crew be married or unmarried; should crewmembers have young children still at home?). 

! Fundamental relationships will be strained significantly by an exploration mission. Consider providing 

support structures for the duration of the mission to help sustain those involved. 

! During the mission, the family must fulfill their needs (with the spouse accorded primary responsibility). 

Other forms of supporting relationships need to be fostered and maintained throughout the entire mission. The 

entire crew will face difficult issues associated with missing family occasions and burdening the spouse with 

added responsibilities. 

! After the mission, family roles will need to be redefined and re-established. Emotions such as frustration, 

resentment, guilt, and depression can affect the re-assimilation process. The spouse who managed the family 

during the mission has established family rules and may feel uncomfortable giving up primary authority and 

modifying established behaviors. 

7.7 REFERENCES

1 Connors M. Report No. NASA-SP-483, Living Aloft: Human Requirements for Extended Spaceflight. Moffet 

Field, CA: Ames Research Center; 1985. 

2 Holland A. ìPsychology of Spaceflightî in Human Spaceflight: Mission Analysis and Design. New York: 

McGraw-Hill, Inc; 2000. p 55ñ91. 

3 Stuster J. Bold Endeavors: Lessons from Polar and Space Exploration. Annapolis, MD: Naval Institute 

Press; 1996. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 8: Anthropometry and Biomechanics 31 

8 ANTHROPOMETRY AND BIOMECHANICS 

Anthropometry and biomechanics seek to improve human performance by understanding the physical 

characteristics of the human body: dimensions, range of joint mobility, locomotion and translation capability, 

physical strength in whole and in part, and functional capabilities (e.g., ratcheting, cranking, arm pushing and 

pulling, leg lifting and lowering, wheel turning, and upper and lower body exertions). 

8.1 KEY CONCEPTS

 Designers must be aware of likely variations in body dimensions to build cockpit seats, EVA and escape 

suits, internal vehicle and habitat architecture, tools, and other items of hardware. They also need to know 

ranges of joint movement and information about strength required for certain tasks. Speed and methods of 

locomotion in microgravity and reduced-gravity under EVA-suited conditions is needed by both suit designers and 

those who design the habitat through which suited crew must move. This is particularly true if a mission plan calls 

for crewmembers to spend any considerable length of time suited up while they attempt to repair the problem. 

Unfortunately, most existing data on anthropometry and biomechanics were gathered in Earthís gravity. Very 

little information is available from microgravity, and there are no measurements for reduced-gravity environments. 

There is a real need to understand the costs, benefits, and political implications of limiting crew physical size. 

Attempting to build equipment to accommodate all people between a 5th percentile Japanese female and a 95th

percentile American male may not be wise. Such a wide spectrum in strength and physical dimensions will 

undoubtedly increase the cost of manufacturing the equipment necessary for a mission. But will limiting size 

really decrease cost or make components more interchangeable or easy to use? There is also a misconception 

that a person in the fifth percentile for stature is also in the fifth percentile for arm reach or shoulder strength. If 

we limit our population by size, we will diminish the pool from which we choose crewmembers. The 

characteristics desired for a crewmember are a cocktail of many parameters, of which size is only one. 

Design and sizing of space modules, EVA suits, and other equipment must consider the user population. To 

fit 90 percent of the general population, one specifies a range of users from the fifth percentile to the 95th

percentile for several critical body dimensions. From there, the range can be narrowed to allow for more 

consistency and interchangeability in EVA suit parts, for example. There is a cost associated with 

accommodating 90 percent of the adult population. In Table 8.1, the variation within each dimension can be as 

high as 58.4 cm (23 in). The choice for EVA, for example, is to (a) develop custom-made suits for each 

crewmember, (b) modify operations to accommodate all crewmembers (e.g., no suited EVA), or (c) greatly restrict 

user size (e.g., a range from 45th to 55th percentile). This last approach, however, may be difficult or impossible if 

we try to accommodate a multicultural crew of both genders. There is a need to perform a cost/benefit analysis 

on all possible options, and to consider the possible political dimensions of such restrictions. 

Table 8.1: Examples of Critical Body Dimensions a,b

Dimensions 5th Percentile 95th Percentile Range 

Stature 148.9 cm (58.6 in) 190.1 cm (74.8 in) 41.2 cm (16.2 in) 

Sitting height 78.3 cm (30.8 in) 99.5 cm (39.2 in) 21.2 cm (8.4 in) 

Arm reach 65.2 cm (25.7 in) 88.2 cm (34.7 in) 23.0 cm (9.1 in) 

Chest circumference 30.3 cm (11.9 in) 89.4 cm (35.2 in) 59.1 cm (23.3 in) 

a Information is from Man-Systems Integration Standards1

b No data is available on sitting leg reach, although this measurement could be an important design factor. 

Currently, the U.S. space program selects crewmembers using the following dimension criteria2: 

! Pilots: 162.5 cm (64 in) to 193.0 cm (76 in) 

! Mission Specialists: 148.6 cm (58.5 in) to 193.0 cm (76 in) 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 8: Anthropometry and Biomechanics 32 

8.2 DEFINITION OF CREW POPULATION 

Current NASA standards1,2 provide data for the fifth percentile Japanese female and the 95th percentile 

American male projected to the year 2000. This does not necessarily define the crew population. These data are 

meant only to characterize the size variation of people across the world. Potential user sizes for specific beyondLEO missions have not been determined. The Anthropometric Initiative document prepared by NASAís Flight 

Projects Division (1999) demonstrates that different organizations use different databases and techniques to 

measure the crew population. This has resulted in widely varying measurements. It would be best to consolidate 

all anthropometric data so that a single well-defined and well-maintained database can represent the relevant 

crew population. 

8.3 ANTHROPOMETRIC DESIGN CONSIDERATIONS

There are three approaches for fitting a design to the user. Not all approaches may be suitable for all 

designs, however. 

! Single size fits all: A single size may accommodate all members of the crew. For example, everyone 

can use a passage, if it is designed for the largest person. A workstation, with a switch within the reach limit of 

the smallest person, will allow everyone to reach it 

! Adjustable: Adjustable hardware, like those found on car seats, can accommodate most of the user 

population when a single size cannot be selected. 

! Custom-build: Individually fitted items may or may not be the right solution. Clothing and eyeglasses 

are examples of items that require a certain amount of custom fitting. Custom-built items, however, are more 

expensive and could increase overall mission costs. 

Variability in Human Body Size 

! Microgravity Effects: Without the loading effect of gravity, the human physique is altered. The following 

must be considered when designing equipment for use in microgravity (refer to Figure 3.2.3.1-1 in the MSIS): 

- Height increases by about 3 percent due to spinal elongation. More complete studies of this effect 

need to be done, especially for long-duration missions 

- The relaxed body naturally assumes an S-shaped posture. Studies have not quantified this, however, 

and this does not account for large individual differences in posture 

- Changes in circumference, associated with fluid shifts and losses, have been subjectively noted, but 

not accurately measured 

- Because of bone and fluid losses, body mass reduces by about 3 to 4 percent. The rate of change 

and the time to reach steady-state conditions have not been fully elucidated 

! Partial-gravity Effects: No studies have been done to characterize how body dimensions change in a 

partial gravity environment. Research needs to be done before equipment is fitted for use during crewed 

planetary and lunar missions. 

! Duration Effects: The effects of ultra-long-term exposure to microgravity and reduced-gravity on body 

dimensions are not known. 

! Effects of Returning to Earth: Data needs to be compiled from prior and future missions to document 

the effects caused by returning to Earth, such as how long it takes to recover body mass, mobility, and the time to 

recover from joint limitations (mobility-related impairment is due to muscle atrophy, bone loss, etc.). 

Strength 

Several aspects of human strength should be understood and considered when designing equipment for the 

space environment: 

! Maximum strength: the ability to generate maximum voluntary muscular tension and apply it to an 

external object; 

! Endurance: the amount of work that can be performed at a given level of effort, isometrically or 

isotonically under submaximal and maximal conditions; 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 8: Anthropometry and Biomechanics 33 

! Functional strength: the ability to perform tasks, such as gripping, grasping, turning a knob, hammering, 

pushing, pulling, carrying, and building; and 

! Tool-specific strength exertions: the use of tools, such as screwdrivers, hammers, and ratchets, to 

maximize strength applied to a task. 

Unfortunately, current design standards1,3 do not provide all the necessary data for designing space hardware 

or tools. To allow 90 percent of the user population to adequately operate the tools provided, the tools should be 

designed for the minimum capability of the user population, while at the same time, be able to withstand the 

maximum capability of the user population. Additional data on a user populationís maximal, functional, and toolspecific strength must be acquired before this goal can be achieved. 

Much of the data in this area are based on Earthís gravity environment. Strength data is needed for reducedgravity environments and long-term missions, since evidence indicates that muscles atrophy in reduced-gravity 

environments. 

Effects of EVA Suits 

Studies5,6 show that wearing a suit reduces strength capacity by about 40 percent. In addition, for industrial 

operations, current National Institute of Occupational Safety and Health (NIOSH) guidelines recommend 

allowable capability to be at or about 30 percent of maximum capabilities. Hence, strength requirements for EVArelated operation may need to be based on similar guidelines. Equipment may also be developed to safely 

augment human strength in order to counteract the effects of the suit.

8.4 REFERENCES

1 Astronaut Selection Criteria (Available in abbreviated form on the public Web site: 

http://spaceflight.nasa.gov/shuttle/reference/factsheets/asseltrn.html) 

2 SSP57000B 

3 Anthropometry Initiative [internal document presented to NASA JSC], April 2000. 

4 Gonzalez L, Maida J, Miles E, Rajulu S, and Pandya A. "Work and fatigue characteristics of unsuited and 

suited humans during isolated isokinetic joint motions" [submitted to Ergonomics Journal]. 

5 Morgan D, Wilmington, R, Pandya, A, Maida, J and Demel, K. Report No. NASA-TP-3613, ìComparison of 

extravehicular mobility unit suited and unsuited isolated joint strength measurements.î 1996. 

6 Pandya A, Maida J, Aldridge A, Hasson S and Woolford B. Report No. NASA-TP-3206, ìThe validation of a 

human force model to predict dynamic forces resulting from multi-joint motions.î 1992a. 

7 Pandya A, Maida J, Aldridge A, Hasson S and Woolford B. Report No. NASA-TP-3207, ìCorrelation and 

prediction of dynamic human isolated joint strength from lean body mass.î 1992b. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 34

9 C R E W A C C O M M O D A T I O N S 

The best exposition of design considerations for crew accommodations is found in the chapter on crew 

accommodations in Human Spaceflight: Mission Analysis and Design.

1 The mass and value factors presented

here and used in the resource model (available as an Excel file: http://advtech.jsc.nasa.gov in the References

section, with detailed instructions in Appendix D) are taken directly from the model described in that chapter.

9.1 KEY CONCEPTS

! Crew accommodations: those elements of mission supplies, hardware, and software that most directly 

serve human needs throughout every phase of a mission, including: 

- Galley, food system, and wardroom; 

- Sleep accommodations and crew 

quarters; 

- Personal hygiene facilities; 

- Clothing systems; 

- Crew health care; 

- Emergency provisions; 

- Recreation equipment; 

- Maintenance equipment; 

- Housekeeping and waste disposal; 

- Photographic equipment; and 

- Restraints and mobility aids. 

! Potable water: water required for drinking, food preparation (typically food rehydration in prior missions), 

and oral hygiene and subject to the most stringent requirements for contamination because it is to be ingested by 

the crew

! Hygiene water: water primarily for external use, such as body cleansing, with similaróbut slightly less 

stringentórequirements for contamination

9.2 RESOURCE MODEL

We have adapted the crew accommodations resource model found in the above-referenced chapter by 

creating an Excel spreadsheet that permits the user to make mission-specific calculations and comparisons of 

mass and volume requirements for eleven systems. We provide detailed instructions for using this model in 

Appendix D and encourage everyone to do so.

The greatest value of this model is that it relies on a comprehensive set of baseline assumptions for crew 

needs, depending on the mission type selected: 

! Shuttle-like mission: generally a short, 2-week mission with little need for self-sufficiency 

! Station-like mission: approximately 3 months or more in duration that can take advantage of Earth resupply and proximity but could benefit from some self-sufficiency 

! Lunar base: expected to be about 6 months to 1 year, where moderate self-sufficiency is needed 

! Mars habitation module: occupied for an extended period of time of 6 to 8 months in transit and up to 

about 2 years on the surface and which requires considerable self-sufficiency 

Although these mission types are used to make all calculations for the model, the user can easily adjust 

specific factors to best approximate the mission design under consideration. 

For example, an exploration or habitation mission will almost certainly require a clothes washer and dryer; 

supplying complete sets of clothes for the duration of the mission, as is done in current space missions, is not 

feasible. By default, this model assumes that a washer/dryer system is not appropriate for Shuttle- or Station-like 

missions, but that the clothing mass for lunar/Mars missions assumes cleaning and reuse of clothing. But the 

baseline assumptions for each mission type are just that: certainly, there are some good reasons for including a 

clothes washer/dryer for an ISS-like mission The goal of this spreadsheet is to allow users accurately explore 

trades in crew accommodations. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 35

9.3 WATER, FOOD, AND FOOD PACKAGING

Water 

Water provisions are divided into potable (ingestible) and hygiene water. Potable water is used for drinking, 

food preparation (typically food rehydration in prior missions), and oral hygiene. Hygiene water is primarily for 

external use, such as body cleansing, and like the potable water, cannot be contaminated with high-levels of 

contaminants. Table 9.1 summarizes the amount of water allotted per crewmember per day for different 

operational states. 

Table 9.1: Summary of Water Consumption per Crewmember for Different Operational States 

Type of Water Operation States Water Consumed per Crewmember per Day 

Potable Nominal 5.16 kg (11.35 lb) 

Potable Off-nominal or otherwise degraded 2.84 kg (6.26 lb) 

Hygiene Nominal 23.4 kg (51.59 lb) 

Hygiene Off-nominal 8.18 kg (18.03 lb) 

Hygiene Degraded 5.45 kg (12.02 lb) 

Water temperature is another important factor because of the food, cleansing, and drinking uses of it. The 

water system must be able to provide potable water in the following temperature ranges: 

! Cold water at 4 °C, +/- 3 degrees (40 °F, +/- 5 degrees); 

! Ambient water at 21 °C, +/- 5 degrees (70 °F, +/- 10 degrees); and 

! Hot water up to 65.6 °C (150 °F). 

Crew hygiene water temperature must be adjustable from 21 °C (70 °F) to 45 °C (113 °F). 

Energy Requirements 

The energy requirements of the crew will depend on the individual needs of each crewmember, their lean 

body mass, and the amount of physical work they are to perform. Crewmembers who frequently conduct EVAs, 

for example, will require more food than crewmembers who do not, because more demanding physical work is 

typically associated with an EVA. 

The caloric requirements for an exploration-class food system are calculated based on the World Health 

Organizationís requirements11, provided below, for the 1-g environment of Earth. Unfortunately, caloric 

requirements for any hypogravity environment are not known, and the activity level of future missions may exceed 

those assumed by the WHO guidelines. 

! Men (30 to 60 years): Activity (1.7) * (11.6 W + 879) = kcal/day required 

! Women (30 to 60 years): Activity (1.6) * (8.7 W + 829) = kcal/day required 

where W = weight (kg) and the activity level is assumed to be medium, ranging from 1.0 to 2.0. 

Assuming an average body mass of 70 kg, the WHO model estimates that an individual would need a caloric 

intake of 1.720 MJ a day. 

Food System Mass 

The mass of the food system will depend heavily on the foodís degree of hydration, which is largely a function 

of the type of food and the method of storage. Fresh foods can contain as much as 95 percent water, while dry 

grains can be as low as 12 percent. Additional information regarding food mass are provided in Tables 9.2 and 

9.3. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 36

Table 9.2: Historical, Near-term Food Masses a

Parameter Mass 

(kg/CD)

Water 

Content 

Volume 

(m3/CD) Comments 

IVA food, dry weight 0.674 0% 

Food provided for Shuttle b 0.8 20% 0.002558 Dehydrated 

 1.818 0.004045 Packaged, with water content 

 0.227 Packaging alone 

 1.591 58% Fresh, no packaging 

Food provided for ISS c 2.3 0.006570 Packaged, with water content 

 1.955 66% Fresh, no packaging 

NOTE: CD: crew day (based on 6 crewmembers) and IVA: intravehicular activity 

a Data based on Bourland (1998) and Vodovotz (1999). 

b STS food systems do not meet nutritional requirements estimated for long-duration space flight. While this diet meets all 

minimum nutritional requirements, it exceeds the limit for sodium and iron for a microgravity diet. Note that this food system

does not use refrigeration. 

c Data provided is based on an ISS assembly-complete diet. Food is provided as 50 percent frozen products. For a 540 CD (6 

crew for 90 days) food supply, 1.84 m3 of refrigerated storage is required. 

In addition to the mass of food itself, packaging is required to protect the food from degradation and 

contamination. This packaging includes exterior food wrappings, which may divide foods into individual servings, 

stowage containers such as lockers, and secondary structures to house the stowage. In total, these can easily 

double the mass of the food system. 

Historically, packaging masses are available for two applicable food systems. An empty food locker onboard 

the Shuttle has a mass of 6.4 kg (14 lbs). Filled, this locker holds up to 42 individual meals for an overall mass of 

24.5 kg (54 lbs) (Bourland, 1999). Perchonok (2002) reports that a loaded ISS food locker for Phase II averages 

5.5 kg each and contains nine meals with snacks (equivalent to one day of food for three ISS crew members). 

For a 1000-day, 6-person Mars mission, food packing would add 3 metric tons to the 30 metric tons of vehicle and 

fuel in the initial mass in LEO, assuming a 10:1 vehicle-payload ratio. 

Table 9.3: Food Quantity and Packaging a

Parameter Assumptions 

Lower Nominal Upper 

Source 

0.54 Lange and Lin (1998) IVA, dry weight (kg/CD) 

 0.674 Bourland (1998) 

IVA human metabolic water 

production (kg/CD) 0.335 Derived from Lange and Lin (1998) 

IVA (MJ/CD) 11.72 Hall and Vodovotz (1999) 

EVA added b (kg/Y) +0.026 Derived from Lange and Lin (1998) 

EVA added b metabolic water 

production [kg/Y] +0.016 Derived from Lange and Lin (1998) 

EVA added b (MJ/CH) +0.563 Lange and Lin (1998) 

Packaging c (kg/kg) 100% Hanford (1997a) 

1 Lane (1999), from Shuttle 

Crew time (CH/d) 3 Hunter (1999); see above 

 9 Kloeris et al. (1998) from LMLSTP Phase III data 

CD: crew day; CH: crew hour (based on 6 crewmembers). 

a The listed food values are ìas shippedî and before addition of any hydration fluid (water). 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 37

b EVA requirements are in addition to any IVA requirements. 

c Packaging accounts for individual food packages, trays, food storage lockers, and other associated secondary structures. 

Although waste will depend on the type of food and preparation used, the waste mass could be quite large. 

For example, during the 10-day menu test conducted during the Lunar-Mars Life Support Test Project (LMLSTP) 

Phase III, total food waste, including preparation, plate waste, and unused food, was 42 percent of all waste.10 

The equipment mass needed to process food for a crew of four is estimated to be about 655 kg (1,444 lbs) 

(Hunter and Drysdale, 1996). This is a very preliminary estimate, however. 

Transit Portions 

The journey between Earth and Mars is approximately 6 to 8 months each way. Assuming that the food items 

provided for this journey will be shelf-stable, prepackaged foods resembling ISS provisions, the mass of food per 

crewmember will be about 1.83 kg (4 lbs) a day. 

Assuming six crewmembers and a transit time of 225 days, then approximately 2.5 metric tons of 

prepackaged food will be required for a single transit between Earth and Mars. If we also assume a 

10:1 vehicle-to-payload ratio, then food alone will increase the mass of the transit vehicle, 

including fuel, by about 25 metric tons. Clearly, considerable overall mission-mass savings can result 

from finding ways to reduce the mass of the food system.

Plants offer the greatest opportunity for self-sufficiency and possibly cost reduction for long-duration missions, 

but at the same time have some of the greatest unknowns. 

Future Directions for Food Systems 

As planning for exploration missions beyond LEO evolves, new technologies in food science and food 

processing will be necessary. Because an exploration crew will not have access to regular resupply, a complete 

3-year diet for 6 crewmembers must be included as part of the mission specifications. Some technologies that 

will be important for such future missions beyond LEO are described below. 

The food system model described above is only one system that might be proposed for a Mars mission. Any 

food system would have the following basic requirements: 

! Prevention of microbial contamination: microbes adversely affect food safety and quality, causing 

changes in freshness, color, texture, and flavor. Therefore, the food system must be free of disease-causing and 

quality affecting microbes, including yeasts, fungus, molds, protozoa, bacteria, viruses, and other organisms. 

! Adequate nutrition for each crewmember: calorie intake requirements will vary from crewmember to 

crewmember, and will be affected by the amount of physical work they perform. For example, the crew must 

consume more food to meet the physical demands of extravehicular activities (EVAs). As we better understand 

the effect of long duration space missions on crew health, the recommended nutrient levels may be revised. 

! Food quality: this parameter can have a tremendous impact on crew morale and performance, which 

requires a highly acceptable and varied system. 

These requirements cannot be met, however, without additional research. For example, the first requirement 

that the food system be free of microbial contamination may not be possible in all circumstances. Shelf-stable 

items that have been vacuum-packaged in plastic and irradiated will remain microbe-free indefinitely, but a diet 

composed of such foods would be nutritionally incomplete if not augmented by fresh items. Hence, many have 

proposed that ultra-long-duration missions that cannot rely on resupply of fresh foods from Earth should include 

one or more growth chambers for plants, in order to provide foods that cannot be made shelf-stable or which 

contain important nutrients that do not survive processing or storage. The warm, moist, and nutrient-rich 

environment of the growth chambers encourages microbial growth and variety. Due to depressed immune 

system function, which is a response to space travel, and the increased rate of microbial mutation, which may 

result from the unique radiation environment, we cannot be certain that ìfarming in spaceî will not engender both 

plant and human disease and adversely affect the safety of the expanded ecosystem. (This is a general concern 

but some evidence suggests that human-associated organisms would not compete well with stable microflora of 

these systems and hence the systems would not be significant reservoirs of these organisms. Refer to Morlaes 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 38

A, Garland J, and Sim D. Survival of potentially pathogenic human associated bacteria in the rhizoshpere of 

hydroponically grown wheat. FEMS Microbial Ecology 20:155-162. 1996) 

The requirement for adequate nutrition may also prove to be challenging. It is almost certain that shelf-stable 

items by themselves will not provide sufficient nutrition to adequately support the crew for ultra-long-duration 

missions beyond LEO. Supplements would help to supply those nutrients not provided by shelf-stable food, but 

there is no guarantee that this augmented diet would provide important micronutrients. Frozen food is an 

attractive supplementary food item, but the mass of a passive freezer and the amount of frozen food required for 

an ultra-long-duration mission may be prohibitive. Additionally, frozen food stored at commercial temperatures is 

only palatable for about a year. Salad components cultivated in a growth chamber would be an excellent food 

supplement, but would also add significant mass to a mission. Because the consequences of crop or seed 

failureóor even the destruction of a frozen foods due to a freezer failureómission designers cannot rely 

exclusively upon crops or food refrigeration. A complete set of shelf-stable food would need to be packed in the 

event of the failure of other food sources. Considerably more inflight experience with these methods of 

provisioning is required before a crew can depend on them for their core nutritional needs. It would also be 

unreasonable to expect that, within the next half century, the addition of necessary ìspace farmingî equipment 

and supplies would reduce mission mass significantly. 

Ultra-long-duration, Shelf-stable Foods 

Shelf-stable foodsóusing high-quality, palatable ingredientsóare important to maintaining a healthy diet 

throughout a long-duration mission. Currently, we have no ability to store a varied and acceptable diet for 3 to 5 

years, as would be required by Mars mission scenarios. New food items developed for a long-duration mission 

should be low in sodium and derive less than 35 percent of total calories from fat. Although breads and a few 

other food items can be made with very-long shelf lives, a large variety of foods in a balanced diet currently fall far 

short of the mark. New and emerging food-preservation technologies and/or packaging methods, such as the 

following, may extend food shelf life: 

! irradiation; 

! sonication; 

! electromagnetism; 

! pressurization; 

! chemical additives; 

! biotechnology; 

! microbial sources 

! pulsed light; 

! dehydration; 

! special packaging; and 

! freezing. 

The treatments employed must be food-specific, due to individual differences in food composition and mode 

of spoiling. Food palatability and variety also requires improvement. If the crew finds the food disagreeable, they 

may consume inadequate amounts of nutrients and, as a result, suffer from poor health or morale. 

Advanced Packaging for Food Storage and Preparation 

The galley on the Shuttle and ISS account for about 75 percent of the trash produced during a mission, and 

about 50 percent of trash dry mass (approximately 0.5 kg per crewmember every day) comes from the plastic 

packages for individually-wrapped meals. Approximately one-quarter of the mass of individually-packaged food 

rations is the packaging material, none of which is biodegradable or recyclable. Waste packaging from the 

Shuttle is returned to Earth for disposal and waste packaging from the ISS is incinerated upon reentry of a spent 

Progress vehicle into Earthís atmosphere. These disposal options would not be possible during exploration class 

missions, resulting in a serious waste-management problem. One solution is to develop new food-packaging 

technologies that use biodegradable or readily recyclable materials and yet still allow for the food items to achieve 

a 3 ñ 5 year shelf life. 

Theoretically, the waste stream coming from the galley could be reduced to near zero if waste products could 

be transformed into objects that would be useful later in the mission. This would also have the net effect of 

eliminating the need to bring those objects. On the outbound trip, for example, the plastic packaging materials 

could be redissolved or remelted and then molded into ìerector-setî-like components that could be used to 

construct tables, chairs, and other items that have little use in microgravity but would be useful on Mars. Holding 

racks, sample containers, rover parts, geological tools―essentially any item of use on a lunar or planetary 

surface―could be manufactured from recycled materials. As a result, the mass of an intravehicular maintenance 

system, which would normally be stocked with a veritable hardware store of supplies, could be reduced if 

replacement items, such as pipes, connectors, mechanical patch materials, could be produced with recycled 

materials during the mission. Even if the recycling process were only partially successful, decreasing the amount 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 39

of unusable waste, and decreasing the size of the systems used to process and store that waste, could easily 

reduce the overall vehicle mass by many metric tons. 

Another solution is to create larger, crew-sized packages. The quantity of trash would decrease, minimizing 

onboard trash storage and treatment facilities needs, and reducing the burden on downstream support systems. 

Additional advantages of family-style dining may also include a decrease in the amount of food required per 

person by reducing food waste and making better use of leftovers. Larger-sized meals are not currently being 

used, because researchers have not found a way to transfer food from the larger pouches to individual food 

holders in 0-g. Any new packaging design would need to be thoroughly tested on the Shuttle or ISS before it 

could be incorporated into a future beyond-LEO mission. Assuming that we will eventually develop ìfamily-styleî 

dining techniques and instruments, the whole galley concept and all of its hardware must be changed to take full 

advantage of ìfamily-style dining.î Ovens, dishwashers, bulk storage, cooking and eating utensils and containers, 

and refrigerator and freezers must be redesigned to accommodate the larger packages. 

9.4 GROWTH CHAMBERS

Fresh salad crops grown during a long-duration mission would provide variety, texture, and color to an 

otherwise dull diet. Crewmembers would realize both nutritional and psychological benefits from salad crops. 

Researchers are developing an advanced life-support system for future missions that would hydroponically grow 

crops and then process them into edible food ingredients or table-ready products. 

The processing equipment for such a system should be highly automated, reliable, and safe, and should 

minimize crew time, power, water, mass, and volume. The equipment must also be suitable for use in 0-g 

or hypogravity (e.g., 0.38-g on Mars) and in hermetically sealed habitats.

The stay on Mars will be approximately 600 days. A plant chamber for growing food could be housed in a full 

rack such as those used on ISS. As the crops mature, they would supply ingredients that would supplement the 

core diet of prepackaged foods. In addition to providing nutrition, such a system might benefit air and water 

recycling, as well as waste removal. 

In the distant future, a Mars base or other ultra-long-duration facility could allow a stay of 5 to 10 years. A 

multitude of plants could be grown at such a base, but more than half of the diet would still likely rely on shelfstable foods. The food system would use food-processing procedures and equipment to convert crops to bulk 

ingredients. These food products could be stored or used immediately, augmenting ingredients supplied from 

Earth. The risks and sustainability of crop systems for life support are still largely unknown, and we need 

continued testing with crops as supplementary dietary items before relying on in situ farming to provide a primary 

food source. If successful, such a system could produce mass savings over 5 to 10 years. 

Mars colonization, with a stay of more than 10 years, may rely primarily on plants grown in situ for the majority 

of the diet (approximately 90 percent of the food, by dry mass). The mass of the farm equipment and growth 

facilities required to create such a self-sufficient base, and which will operate without the danger of crop disease 

or failures, is currently unknown. Such a food system would be integrated with the air revitalization, water 

recovery, biomass, solid processing, and thermal control systems. The designers will consider the availability of 

power, volume, and water as they develop the entire food system. 

Hypothetical Diets for Long Durations 

Tables 8.3 and 8.4 present diets that assume differing availability of crops grown at the site of a base or 

colony. In both cases, the menus are designed to be used as a unit for meeting the crewís nutritional needs. 

NASAís Advanced Life Support Program proposes a 20-day crew diet using crops as shown in Table 9.4. 

The edible masses of the main crops as harvested to support the 20-day diet are calculated per crew-day and for 

a crew of six people for a 20-day period. This menu averages roughly 11.72 millijoules per crew day (MJ/CD), 

uses a wide variety of crops, and provides a high degree of closure. With respect to closure, the majority of the 

resupply mass is oil, which is necessary for nutrition but is not produced efficiently from higher crops. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 40

Table 9.4: Twenty-Day Diet Using All Potential Food Crops a

Crop Average Consumption (kg/CD) Menu Consumption (kg) b

Soybean 0.086 10.4 

Wheat 0.24 28.8 

White potato 0.20 24.2 

Sweet potato 0.20 23.7 

Rice 0.029 3.5 

Peanut 0.013 1.5 

Tomato 0.22 26.6 

Carrot 0.041 5.0 

Cabbage 0.0038 0.5 

Lettuce 0.024 2.9 

Dry bean 0.013 1.5 

Celery 0.013 1.5 

Green onion 0.048 5.7 

Strawberry 0.016 2.0 

Peppers 0.049 5.9 

Pea 0.0075 0.9 

Mushroom 0.0011 0.1 

Snap bean 0.010 1.2 

Spinach 0.040 4.8 

Crop subtotal 1.25 150.7 

Water c 2.20 263.3 

Resupplied food stuffs d 0.37 44.6 

Total 3.82 458.6 

NOTE: CD: crew day (based on 1 crewmember) 

a The listed food values are ìas shippedî and before additional of any hydration fluid (water). Derived from Hall and Vodovotz 

(1999). 

b Quantity is based on six crewmembers over twenty days. 

c Water data is for hydration, cooking, and food preparation only. Water for clean-up and water tankage are not included. 

d Oil is included as a resupply item. No frozen or refrigerated foods or packaging are included in this calculation. Resupplied

food is about 20 percent moisture by mass. 

A second 20-day crew diet is presented in Table 9.5. Again the edible masses of the main crops, as 

harvested to support the 20-day diet, are calculated per crew-day for a crew of six people for a 20-day period. 

This menu also averages 11.72 MJ per crew-day. Unlike the previous formulation, this diet plan produces only 

salad and carbohydrate crops on site, because these crops are the most efficient of the higher plants considered 

here. Most protein is primarily resupplied in the form of shelf-stable meat. 

Table 9.5: Twenty-Day Diet Using Salad and Carbohydrate Crops a

Crop Average Consumption (kg/CD) Menu Consumption (kg)b

Soybean n/a n/a 

Wheat 0.22 25.8 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 41

White potato 0.17 19.8 

Sweet potato 0.18 21.5 

Rice n/a n/a 

Peanut n/a n/a 

Tomato 0.21 24.6 

Carrot 0.040 4.8 

Cabbage 0.0025 0.3 

Lettuce 0.021 2.6 

Dry bean 0.013 1.5 

Celery 0.0075 0.9 

Green onion 0.034 4.1 

Strawberry n/a n/a 

Peppers 0.031 3.8 

Pea 0.0038 0.5 

Mushroom 0.0013 0.2 

Snap bean 0.010 1.2 

Spinach 0.040 4.8 

Crop subtotal 1.0 116.4 

Water c 2.1 253.7 

Resupplied food stuffs d 0.5 57.5 

Total 3.6 427.6 

NOTE: CD: crew day (based on 1 crewmember) 

a The listed food values are ìas shippedî and before additional of any hydration fluid (water). Derived from Hall and Vodovotz 

(1999). 

b Quantity is based on six crewmembers over twenty days. 

c Water data is for hydration, cooking, and food preparation only. Water for clean-up and water tankage are not included. 

d Oil is included as a resupply item. No frozen or refrigerated foods or packaging are included in this calculation. Resupplied

food is about 20 percent moisture by mass. 

9.5 WASTE MANAGEMENT

Based on current waste production levels, each crewmember can be expected to produce about 1 kg (2.2 lbs) 

of dry trash per day, primarily from the use of habitation systems and crew supplies. For a 1000-day, 6-person 

Mars mission, this would come to 6 metric tons of trash in addition to the 60 metric tons of vehicle and fuel for the 

initial mass in LEO (IMLEO), assuming a 10:1 vehicle-payload ratio. Waste weight estimates for several mission 

profiles are provided in Table 9.6. 

Table 9.6: Estimated Waste Mass for Different Mission Profiles a

Waste Component Transit 

(180 days)b

Independent 

Exploration 

(600 days)c

Exploration 

Mission 

(600 days)d

Extended Base 

(10 years)e

Extended Base 

(10 years)e

Dry human waste 0.720 0.720 0.720 0.720 0.720 

Inedible plant biomass 0.404 1.874 5.507 7.486 13.787 

Trash 0.556 0.556 0.556 0.556 0.556 

Packaging material 7.908 7.122 5.866 4.341 1.185 

Paper 1.164 1.164 1.164 1.164 1.164 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 42

Tape 0.246 0.246 0.246 0.246 0.246 

Filters 0.326 0.326 0.326 0.326 0.326 

Miscellaneous 0.069 0.069 0.069 0.069 0.069 

Subtotal 11.390 12.080 14.450 14.910 18.050 

Grown food 0.000 1.740 6.000 7.500 14.172 

Packaged food 4.044 3.642 3.000 2.220 0.606 

Total 15.434 17.462 23.450 24.630 32.828 

CD: crew day 

a All units are based on a 6-person crew. 

b Profile is based on a packaged foods diet model. 

c Profile includes the cultivation of salad crops. 

d Profile is based on a low-carbohydrate diet model. 

e Profile is based on an all-plants diet model. 

Refer to Appendix B for the details of each waste component 

Solid Waste System Requirements 

Table 9.6 provides estimates of types and quantities of waste that must be handled during a variety of mission 

profiles. Important considerations include: 

! Containment and sterilization of wastes; 

! High-fidelity systems to satisfy the different constraints of various missions; 

! Multifunctional systems that can be used for various missions; 

! System models to identify the mission resource-recovery needs; and 

! Various waste processing subsystem integrated with the water recovery and air revitalization subsystem. 

DESIGN C ONSIDERATIONS

! Ease of use: a bodily-waste management system should be simple and quick to use, as well as readily 

available for emergencies, such as vomiting or diarrhea. As a design goal, the facilities should resemble 

equivalent Earth-based facilities, requiring approximately the same amount of time to use. 

! Redundancy: a beyond-LEO mission can be doomed if the bodily-waste management system fails and 

a functioning alternate, redundant system is not available. 

Trash Management 

A trash management system designed for an ultra-long-duration mission should rely heavily on recycling and 

reuse. Plastics, which make up the majority of dry waste, could be remolded into a variety of useful items, such 

as air filters, replacement parts, or even basic erector-set-like components that could be used to build larger 

items. Through inflight and on-surface recycling of trash, it is conservatively possible to reduce the IMLEO of a 

Mars vehicle by at least 45 metric tons, or about 10 percent of total vehicle mass, based on a 425 metric-ton 

vehicle. The possibility of a inflight waste recycling, however, is contingent on additional research into recycling 

techniques and advanced reusable materials. Currently, techniques for recycling in microgravity or reduced 

gravity have not been developed. Before a trash recycling/reuse system can be incorporated into a future mission 

design, extensive testing on both potential systems and materials must be conducted on the Shuttle and the ISS. 

Based on a Mars mission profile like the one described above, approximately 1.5 metric tons of trash will 

remain unrecoverable. This type of trash also requires a carefully-designed management system. 

DESIGN C ONSIDERATIONS

! Location of trash receptacles: The selection and placement of trash receptacles must be based on 

crew activities. Several small receptacles placed throughout the spacecraft may initially save crew time, but will 

ultimately cost time if the crew must gather the trash from the receptacles and transport it to a central receptacle. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 43

! Separation: The crew will sometimes have to manually separate biologically-active trash, such as 

leftover food, from plastics, metals, and other materials to facilitate the stowage, recycling, or disposal of trash. In 

some cases, the most separation will be carried out automatically equipment, such as dishwashers, clothes 

washer and dryers, and showers, but the crew will still need to clear filters or empty traps. 

! Manipulation: Every effort should be made to automate trash management, not only to reduce the 

amount manual manipulation the crew must perform, but to also reduce trash volume through compaction. 

9.6 PERSONAL HYGIENE

Good grooming can enhance self-image, improve morale, and increase the comfort and productivity of the 

crew. Personal hygiene includes body washing (whole or partial), oral care, and hair cutting, grooming, and 

shaving. Adequate and comfortable personal hygiene and body-waste management facilities have been high on 

the list of priorities for participants in prior space missions, but they will become even more important during future 

long-duration missions. The Moon missions conducted in the late 1960s and 1970s were short, but the crew was 

extremely bothered by lunar dust that was brought into the lunar module. In the absence of a significant 

atmosphere on the Moon, extremely fine dust was electrostatically attracted to the EVA suits and could not be 

brushed off. Upon returning to the module and reintroducing air, the tiny dust particles fell off the suits and got 

into everything. 

Frequent whole-body cleansing will become a critical part of personal hygiene during future planetary 

missions if highly effective dust-control methods cannot be developed. Terrestrial personal-hygiene practices and 

procedures may require some modifications, due to equipment limitations and water supply restrictions, but the 

experience should be as simple as possible. Wet wipes are sufficient for whole-body cleansing during shortduration missions, such as the Shuttle, but showers are a must for longer flights. The Russian Mir shower had a 

water-tight, rigid wall that surrounded the user and prevented water from leaking into the rest of the cabin. 

Cosmonauts were allowed 10 liters of water per shower, which was then returned to the water reclamation system 

for extraction and reuse. Skylab had a soft-walled, collapsible shower that earned a reputation for being so 

difficult to use and clean that it was rarely used. A rigid-walled shower would be the better choice for a longduration mission 

Design Considerations 

! Ease and comfort of use: ideally, the personal-hygiene facility should be as easy to use as a groundbased facility, while still taking into consideration mass restrictions and water reclamation needs. Experience with 

the Skylab shower design revealed that a personal-hygiene facility will be used less frequently if it is awkward and 

uncomfortable, or requires an inordinate amount of time to setup and use. 

! Privacy: privacy for partial- and whole-body cleansing, including dressing and undressing, is essential 

particularly if the crew is composed of men and women. 

! Microgravity considerations: Water and debris, such as hair, do not fall to the floor in microgravity as 

they do on Earth. Water and debris collection poses both an engineering and operational problem for 

crewmembers. For example, taking a shower in microgravity requires a hand-held vacuum to remove the buildup 

of water and soap on the body, particularly near the face. Activities, such as showering, that require relatively 

little time on Earth can take a lot more time and be far less relaxing in microgravity. This can have a negative 

impact on mission schedules and personal motivation to use personal hygiene equipment. 

! Restraints: crewmembers can exert an inordinate amount of effort and energy stabilizing themselves if 

restraints are not provided. These restraints should be compatible with the personal hygiene operation and 

environment. For example, foot restraints used in a whole-body wash facility should not be damaged when 

exposed to water and should prevent slipping in wet environments. 

Clothes and Cleaning Rags 

Current LEO missions return soiled garments to Earth for cleaning, and the ISS crews rely on periodic 

deliveries of fresh clothes. This will not be a possibility during a beyond-LEO mission. A 1000-day, 6-person 

Mars mission would require at least 2 metric tons of clothingóeven if the crew wore each garment for a weekóif 

they did not have a clothes-washing system. This estimated weight does not include the 1350 kg (2976 lbs) of 

housecleaning disposable wipes, like those currently used by the space program, and packaging that would be 

added to the waste-management system. Obviously, an ultra-long-duration mission requires a system for 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 44

washing and drying both clothes and cleaning rags. Assuming a 10:1 vehicleñpayload ratio, a cleaning and 

drying system could save 34 metric tons in overall vehicle mass by reducing the amount of clothing that must be 

included in the mission and by replacing disposable wipes with reusable, washable cleaning rags. 

Design Considerations 

A washer/dryer system for use in a microgravity or hypogravity environment does not currently exist. A great 

deal of research and development, followed by significant testing onboard the Shuttle and ISS, must occur before 

such a system can be incorporated into a beyond-LEO mission. The resulting technology could be considered 

enabling, however, since it is unlikely that a Mars mission would be undertaken if clothes could not be cleaned en 

route. 

9.7 INTRAVEHICULAR MAINTENANCE SYSTEM

Technologies for system repair are essential to mission success, as well as to mass and cost reduction. The 

complexity of a Mars vehicle, the long mission duration, the high-probability of equipment failure, communication 

distances of up to 20 minutes each way, and the impossibility of resupply all make a complete intravehicular 

maintenance system (IMS) one of the most critical components of a Mars mission. Similarly, an adequate IMS is 

also critical for long-duration Moon missions. The IMS should include tools, replacement parts, hoses, wire, 

connectors, supplies, methods for mocking up integrated circuits (ICs) through programmable ICs, decisionsupport and expert systems, troubleshooting drawings or procedures, and other electronic tools. 

Sizable mass and volume savings can be made by designing a minimal-mass, yet complete, IMS. For 

example, the development and use of ultrasonically-cured patching materials and adhesives might reduce the 

number of pipes, panels, and other replacement parts that would need to be stocked. The ability to manufacture 

some components during the mission would also reduce mass and cost. 

The current state-of-the-art, inflight maintenance systems are insufficient for a Mars mission. Generally 

simple tasks, such as plumbing and soldering, become more challenging in a microgravity or reduced-gravity 

environment. A great deal of development and inflight testing onboard the Shuttle and ISS must be done for 

materials and techniques before true mass savings from IMS technology can be realized. 

Design Considerations 

! Uniform materials: Repair materials should be carefully selected before vehicle design begins to ensure 

that uniform materials are used throughout the vehicle, making it easier to replace and manufacture parts during 

the mission. 

! Expert advice: Any IMS should be highly usable and as intelligent as possible. The IMS should have a 

computer interface, or some other intelligent device, that would provide the crew with expert advice and guidance 

for troubleshooting and repairs. 

9.8 REFERENCES

1 Stilwell D, Boutros R, and Connolly J. ìChapter 18: Crew Accommodationsî in Human Space flight: Mission 

Analysis and Design. New York: McGraw Hill Companies, 1999. 

2 Brown R, îISS Trash Operations Plan, Team 0 Proposal,î 1999 November. 

3 Connors MM. (1985) Living aloft: Human requirements for extended spaceflight. NASA SP-483. Moffet Field, 

CA: Ames Research Center. 

4 Drysdale A and Hanford A. Report No. CTSD-ADV-383, îAdvanced Life Support Systems Modeling and 

Analysis Reference Missions Document (Draft),î NASA JSC; 1999 October. 

5 Golub M and Wydeven T. Report No. NASA-TM-103888, îWaste Streams in a Typical Crewed Space Habitat: 

An Update.î February 1992. 

6 Hanford A. "Advanced Life Support Systems Modeling and Analysis Project Baseline Values and 

Assumptions Document,îCTSD-ADV-371,June 18, 1999. 

7 Hunter J and Drysdale A. (1996) ìConcepts for Food Processing for Lunar and Planetary Stations,î SAE 

paper 961415, 26th International Conference on Environmental Systems, Society of Automotive Engineers, 

Warrendale, PA. 

8 Hunter J. Department of Agricultural and Biological Engineering, Cornell University, Ithaca, New York. 1999. 

Personal communication, 24 May 1999. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 9: Crew Accommodations 45

9 JSC Food Processing System Infrastructure Preliminary Design Review, July 2000. 

10 Kloeris V, Vodovotz Y, Bye L, Stiller CQ, and Lane E. ìDesign and Implementation of a Vegetarian Food 

System for a Closed Chamber Test,î Life Support and Biosphere Science 5:231-242. 1998. 

11 Lane HW. National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas. 

12 NASA-STD-3000. Man-Systems Integration Standards. Revision B. Houston, TX: Johnson Space Center. 

July 1995. 

13 ECLSS Architecture Description Document, Volume 2, Book 2, Revision A, ISS Document D684-10508. 

1996 May. 

14 Stuster J. Bold Endeavors: Lessons from Polar and Space Exploration. Annapolis, MD: Naval Institute 

Press; 1996. 

15 Verostko C, Packham N, and Henninger D. îFinal Report on NASA Workshop on Resource Recovery from 

Wastes Generated in Lunar/Mars Controlled Ecological Life Support Systems (CELSS)î, CTSD-ADV-035, 

1992 August. 

16 Hall and Vodovotz, Y. (1999) National Aeronautics and Space Administration, Lyndon B. Johnson Space 

Center, Houston, Texas. 

17 Vodovotz Y, Bourland C, and Rappole C. SAE Paper #972363, ìAdvanced Life Support Food Development: A 

New Challenge.î Presented at the 26th International Conference on Environmental Systems. 1997. 

18 World Health Organization (WHO). ìEnergy and Protein Requirements.î Technical Report Series 724, 

Report of a Joint FAO/WHO/UNU Expert Consultation. Geneva: World Health Organization; 1985. 

19 Wydeven T. Report No. NASA-TM-84368, îComposition and Analysis of a Model Waste for a CELSS.î 1983 

September. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 10: Architecture and Habitability 46

10 ARCHITECTURE AND HABITABILITY 

The following description of facilities addresses specific considerations for designing and configuring the 

human-rated spacecraft or habitat. General issues concern how much volume to devote to each function, where 

to place the facility, and how to demarcate functional areas within a limited pressurized volume. At present, we 

do not fully understand the amounts and types of space required for the exploration crew (likely composed of 

international members) that will be confined together during a long duration missions. Chapter 9 on Crew 

Accommodations also considers these factors in some detail. 

10.1 KEY CONCEPTS

The architecture of any spacecraft must address the following needs and considerations, a number of which 

are described below. To begin with, several functions/facilities must be defined: 

! for work, 

! ìpublicî recreational areas that are shared by the entire crew, and 

! individual crew private areas. 

Architecture must also consider crew privacy and the need for personal space, especially given the public 

nature of a long-duration exploration mission. This design aspect relates to personal volume, the ability to control 

or personalize oneís space with family photographs, books, tapes, and the need for private time during 

communications with family and flight surgeons (this is further addressed in Chapter 9 on Crew Accommodations, 

section 9.7). Individual privacy needs are also determined by individual characteristics and culture. Given 

volume constraints, it is more efficient to provide only shared interior space, but private space becomes more 

important as mission duration increases; facilities to meet the need for individual privacy and public interaction 

should be balanced. 

10.2 OVERARCHING ISSUES

Any system design should be based on the smooth flow and logical sequence of activities. The most efficient 

layout is usually to place crew stations adjacent to each other, if they are used sequentially, or in close 

coordination. However, adjacent positions might cause two workers to get in each otherís way, thereby degrading 

their performance and possibly preventing their safe egress during emergencies. Attention needs to be given to 

the volume of traffic expected in any given area. 

Activities such as communications, sleeping and rest, and mental concentration are adversely affected by 

noise (refer to Chapter 11 on Crew Environment, Section 11.2). Activity centers generating significant noise 

levels should not be placed adjacent to centers adversely affected by noise. 

Ambient illumination may interfere with the activities in an adjacent area. Some areas are kept dimly 

illuminated, such as windows used for outside viewing and crew quarters during sleep hours. These areas should 

be placed away from those requiring bright illumination or light-blocking barriers should be provided to separate 

areas.

Vibrations and jolts disturb some personal activities, such as relaxation and sleep. Crew areas requiring a 

quiescent environment should be isolated from sources of vibration. 

10.3 TOTAL HABITABLE SPACE

There is currently no method to determine, with absolute certainty, the amount of habitable space per 

crewmember needed for missions beyond LEO. 

Until better data is available, designers should plan on allocating a minimum of 16.99 m3

 (600 

ft3) of usable space per crewmember. 

Hatches and Doors 

! User size: The size of the hatch and door opening should accommodate the largest crewmember, plus 

any equipment to be transported. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 10: Architecture and Habitability 47

! Suited crewmembers: Internal doors are normally only be used by IVA crewmembers. In some cases, 

passages and doorways must be large enough to accommodate a suited crewmember. 

! Traffic considerations: Internal doors and hatches are points of potential traffic congestion. Special 

attention should be given to the placement of doors and hatches to help avoid this problem. 

Windows 

! Glare, dark adaptation, and light-sensitive activities: Bright interior illumination could reflect off 

window surfaces and degrade visibility. It could also interfere with dark adaptation necessary for celestial 

viewing. Similarly, exterior light through windows could also interfere with light-sensitive activities, such as 

sleeping, use of cathode ray tube displays, or tasks requiring dark adaptation. Interior and exterior light-control 

devices, special window materials, and careful placement of windows throughout the spacecraft or habitat are 

ways to avoid these problems. 

IVA Mobility Aids 

! Method of use: Previous experience has shown that mobility aids, such as hand rails, are not used for 

hand-over-hand translation. Instead, they are used primarily to control body orientation, speed, and stability. 

After the crew gains confidence in free-flight translation, they mainly use planned fixed-mobility aids at free-flight 

terminal points or while changing direction. Padding or kick surfaces should be considered at free-flight terminal 

points. 

! Use in emergencies: IVA mobility aids may have to be used by space-suited crewmembers during 

emergency conditions. Therefore, the aids should be located to accommodate bulky garments with reduced joint 

movement and clearance (refer to Chapter 3 on Human-Rated Vehicle Requirements, section 3.4 and Chapter 10 

on Architecture and Habitability, section 10.3 for related information). 

! Operator stability: Restraints should be available around workstations where the operator must remain 

stable or must use two hands to performance certain tasks, such as viewing through an eyepiece, operating a 

keyboard, or repairing a circuit. 

Interior Decor 

! Personalization: The ability of a crewmember to personalize certain portions of her or his environment 

can be a morale booster. This option should be limited to an individual's personal quarters. A simple way to 

personalize an quarters is a bulletin board on which the crewmember could display photos or other memorabilia. 

Orientation and Layout 

In a 1-g or hypogravity environment, the orientation of objects within an area is not a particular problem. The 

pull of gravity determines how we position our bodies, and we orient our surroundings based on our perception of 

up and down. In a microgravity environment, where gravity and acceleration are imperceptible, orientation is 

arbitrary. There is no gravity cue that defines up or down, and orientation is defined primarily through visual cues 

that are under the control of the system designer. The orientation within a particular crew station is referred to as 

a local vertical. Several orientation factors should be considered when designing for the microgravity 

environment: 

! Work surfaces: Microgravity expands the number of possible work surfaces (walls, ceilings, as well as 

floors) within a given volume. This could result in a number of different local verticals within a module. 

! Training and testing: Some of the working arrangements that will occur in microgravity will not be easily 

duplicated on Earth. Pre-mission training and testing will not fully prepare crew. Facilities and equipment will be 

necessary to conduct additional training during the mission. Please refer to Chapter 15 on Planning for Human 

Operations, section 15.1 for further consideration of training needs. 

! Disorientation: We are accustomed to forming mental images of our environment with a consistent 

orientation derived from gravitational cues. We locate ourselves and objects according to these mental images. 

If we view the environment in an unusual orientation, these mental images are not supported, causing 

disorientation, temporary loss of direction, overall decreased performance, and in the case of spaceflight, space 

motion sickness.

Visual cues are needed to help crewmembers quickly orient themselves and create a more familiar view of 

the world. These visual cues, such as the edges of a window, should define some sort of horizontal or vertical 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 10: Architecture and Habitability 48

reference plane (a horizontal cue is more effective). Further research is presently being conducted by NASA to 

determine additional guidelines for the design of visual-orientation cues. 

10.4 CREW QUARTERS

The design and layout of private activity and sleeping quarters for an individual crewmember can significantly 

affect the crewís quality of life: 

! Mission duration and privacy: As missions become longer, the need for privacy increases, as does the 

space required for each crewmember. The need for privacy is determined by individual and culture factors: the 

level of introversion or extroversion is an individual trait; and while privacy is a culturally-universal need, cultures 

vary in how private space is implemented or in expectations of privacy. However, the need for privacy becomes 

more pronounced for all crewmembers as missions become longer, particularly if they must endure a confined 

spacecraft or habitat. 

Hot-bunking, where crewmembers sequentially occupy the same sleep space, should be avoided even 

though it might reduce the overall mass and volume of a spacecraft or habitat. Everyone needs to have at least 

some individual space, and there will be times when all crewmembers might simultaneously need to take some 

time off or sleep. 

Depending on the design, dormitory sleeping arrangements might be acceptable if individual bunks can be 

created and used as places of retreat. 

! Communications: A two-way audio, visual, and data communications system needs to be provided 

between the crew quarters and other module areas. The system must also adequately alert occupants in crew 

quarters of emergency situations. 

! Environmental controls: Individual lighting, ventilation, and temperature controls need to be provided in 

crew quarters. These controls should be adjustable from the bed. 

! Noise control: The noise dampening systems in the crew quarters must meet all requirements, as 

described in Chapter 11, Crew Environment, section 11.2. 

! Compartment size: Without additional research, the amount of dedicated, private volume that needs to 

be assigned for each crew quarters during long-duration missions cannot be definitely determined. The internal 

dimensions should be sufficient to comfortably accommodate the largest crewmember. 

For conceptual designs, the following should be considered minimums: 

! 1.50 m3

 (53 ft3) for sleeping 

! 0.63 m3

 (22 ft3) for stowage of operational and personal equipment 

! 1.19 m3 (42 ft3

) for donning and doffing clothing

These volumes do not include the crew quarters structures or the additional space needed for a desk, 

computer and communications system, trash stowage, personal grooming, medical equipment and supplies 

during convalescence, and an area for off-duty activities. 

10.5 GALLEY AND WARDROOM

Meals can considerably enhance the quality of the crewmembers' lives. In addition to satisfying nutritional 

needs, mealtimes can offer a chance to rest and socialize, while providing a familiar reminder of normal, Earth 

living. The social benefits of sharing a meal are significant as well. Researchers have suggested that 

crewmembers should plan to eat at least one meal a day together to maintain group cohesion. 

Design Considerations 

! Food consumption locations: Ideally, it should be possible to consume food virtually anywhere in the 

habitat without undue difficulty. Work schedules and other pressures may make it desirable to eat while engaged 

in various work activities. However, having a comfortable group dining space, called a wardroom in naval and 

space applications, is very important for ultra-long-duration missions. To reduce overall spacecraft mass and 

volume, a wardroom need not be a separate, dedicated room. It can also double as a conference room or other 

group-activity space. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 10: Architecture and Habitability 49

! Restraints: Restraints need to be provided for crewmembers, food, utensils, cooking equipment, and 

other loose items in the galley and wardroom. 

! Cleaning: The surfaces in the galley and wardroom must be fully accessible for cleaning and sanitation, 

and the surface texture should be easy to wipe clean. Permanent bactericidal surface coatings have been 

developed in recent years. Further research should be done to determine if recently-developed permanent 

bactericidal surface coatings will be useful in the space environment. 

10.6 EXERCISE FACILITIES

A well-outfitted facility for exercise is needed to combat the harmful effects of microgravity or hypogravity on 

the human body. Exercise also provides recreation and helps maintain crew morale. Exercise facilities should 

include strength-training equipment, to provide the muscle enhancement and increased-strength benefits of 

weightlifting, and different types of aerobic exercise equipment, to increase cardiovascular strength and capacity. 

Design Considerations 

! Vibration and noise: Most exercise equipment is noisy and causes vibration, and should be isolated 

from crew quarters, science and spacecraft systems, and instruments affected by vibration. 

! Potable water dispenser: Cool drinking water should be readily available during exercise. 

! Cooling: Perspiration does not drip from the body in microgravity, but rather pools on the body or floats 

into the atmosphere. In 1-g, convection causes warm air around the body to rise, but in microgravity this will not 

occur. Adequate airflow is the most effective means of cooling in 0-g. Absorbent clothing and other techniques 

can also help control perspiration. 

10.7 RECREATION FACILITIES

As crews travel far from Earth on ultra-long-duration missions, they will need generous amounts of time for 

recreation. The fast-paced Shuttle mission may be scripted almost down to the minute, but crews cannot keep up 

a high level of work for many months or years at a time without ample opportunities to relax. One of the favorite 

recreations in prior space missions has been gazing out the window at Earth, but this may be less interesting 

given the stark interplanetary space or the bleak surface of a planet. A generous supply of recreational items for 

individual and group entertainment, such as games, books, music, and audio-visual materials, are necessary. 

Photographic Equipment 

Since the first human space flights, crewmembers have recorded their experiences in space, from Earth and 

Moon observations to daily in-flight activities. These videos, movies, and photographs transmitted or returned to 

Earth are the publicís most obvious return on their investment in the space program. Many crewmembers also 

find photography to be an enjoyable pastime. Future beyond-LEO exploration missions will probably include highspeed, high-resolution video and still digital cameras, allowing the images to be rapidly transmitted back to Earth. 

10.8 STOWAGE FACILITIES

Stowage difficulties have plagued many LEO flights due to sheer mass and to the logistics required for 

inventorying and locating stowed items. Facilities can be located at particular crew workstations, ready for 

immediate use, or kept in a separate stowage area apart from normally occupied areas. 

The Shuttle-Mir Phase I program demonstrated the difficulty of finding little used items, such as tools, written 

procedures, and supplies. A method for tracking the location and status (e.g., health and functional state) of 

items, such as by embedding a small microchip with an integral micro-transmitter, may help crew locate items, 

preventing failures from propagating from system to system while the missing item is sought. 

Design Considerations 

In most cases, items should be stored in an area as close as possible to where they are used. There are 

cases, however, when this would be impractical. A central storage point can make inventory tracking a simpler 

task, while also maximizing the space allotted for stowage. A combination of techniques is probably best. For 

example, food for a dayís worth of meals might be stored in a galley pantry, but the bulk of the food supply might 

be stored in a central facility. Considerations for the intravehicular maintenance system are addressed in Chapter 

9 on Crew Accommodations, section 9.7). 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 10: Architecture and Habitability 50

10.9 REFERENCES

1 Report No. MSC-03909. ìMobility and Restraint.î Habitability Data Handbook - Vol. 1. NASA-MSFC. 7-31-

71. 

2 Report No. MSC-03909. ìArchitecture and Environment.î Habitability Data Handbook - Vol. 2. Supplement 

2. NASA-MSFC. 5-73. 

3 Report No. MSC-03909. ìHousekeeping.î Habitability Data Handbook - Vol. 3. NASA-MSFC. 7-31-71. 

4 Report No. MSC-03909. ìFood Management.î Habitability Data Handbook - Vol. 4. NASA-MSFC. 7-31-71. 

5 Report No. MSC-03909. ìGarments and Ancillary Equipment.î Habitability Data Handbook - Vol. 5. NASAMSFC. 7-31-71. 

6 Report No. MSC-03909. ìPersonal Hygiene.î Habitability Data Handbook - Vol. 6. NASA-MSFC. 7-31-71. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 51

11 CREW ENVIRONMENT

11.1 KEY CONCEPTS

! Noise criteria (NC): rating of ambient noise typically represented as a family of curves; developed to 

quantify how room noise affects speech communications 

! Comfort zone: that range of environmental conditions in which humans can achieve thermal comfort 

11.2 ACOUSTIC NOISE

The many detrimental effects of a noisy environment on crewmembers include: 

! Physical damage to the sensing organs of the ear, resulting in permanent or temporary hearing loss; 

! Speech and communication interference resulting in potentially unsafe operating conditions; and 

! Psychological stress, possibly resulting in hypertension, loss of sleep, fatigue, irritability, loss of 

productivity, distraction, possible increase of errors in judgment, and decreased morale. 

The most severe of these effects are associated with the loudest noise levels. Nonetheless, even moderate 

noise levels over extended periods can cause auditory damage and hearing loss. Hearing loss occurs differently 

in individuals, with some people being more sensitive to sound and other being more susceptible to physical 

damage. Hearing loss is classified as either a temporary threshold shift (TTS) or a permanent threshold shift 

(PTS). 

As opposed to industrial workers, the spacecraft crews cannot escape their noisy work environment after the 

work day is over. Conversely, we would not expect machines like punch presses or saws used in factories, 

industry, or other high-noise work environments to be employed on crewed spacecraft or habitats. 

Acoustic Environment 

Because of the 24-hour per day, 7-day per week exposure, space vehicles are required by NASA to meet 

more stringent noise requirements than the Occupational Safety and Health Administration (OSHA) levies on 

workplaces for an eight-hour day. In addition to the consideration of 24-hour-a-day exposure, NASA spaceflight 

requirements also vary depending on the duration of the mission. 

In the past, failure to maintain reasonable levels in extended-noise-exposure situations has led to many cases 

of hearing loss. For example, hundreds of U.S. Navy personnel have experienced significant hearing loss during 

submarine and ship missions, resulting in the U.S. government having to spend millions of dollars annually to pay 

for hearing aids for veterans. In another example, a very-high percentage of Mir cosmonauts experienced TTS, 

and several with PTS were disqualified from further space flights as a result. 

Hearing protection provides some small amount of relief, but is only comfortable to wear for a few 

hours and, therefore, does not provide a permanent solution for a 24-hour-a-day noise problem. 

On vehicles or in habitats, noise is generated by fans, pumps, compressors, motors, environmental systems, 

actuators, exercise equipment and rotating machinery, as well as equipment supporting computers and science 

experiments. Any given vehicle has hundreds of these items. The cumulative noise emissions, along with the 

acoustic characteristics of the enclosed space, create the habitable volumeís acoustic environment. Vibration 

isolation, sound containment, sound dampening, and machinery balancing are some of the measures available 

for quieting these sources; success has been limited to date, mostly because of the lack of attention to acoustics 

in the design phase of hardware. 

In terms of duration, some noise producers operate continuously and some operate intermittently. To 

characterize a noise environment that is produced by differing numbers of continuous and intermittent sources, a 

time-weighted average of the noise is taken over a period of time. We denote the equivalent sound pressure level 

or noise dose as LAeq For a typical Earth-based workday, the duration used is eight hours, but for spacecraft 

environments, the applicable integration period is 24 hours. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 52

Acoustic Specifications for Mission Durations of 4 Months 

The ISS, which hosts relatively long-duration missions lasting up to 4 months, is used below as a model of 

acoustic requirements during space missions. The unit used to denote noise level (dBA) relates noise to 20 

microPascals, the lowest noise level that the average 18-year old male human can hear. For a standard 8-hour 

workday, the NIOSH has recommended an average noise level of less than 85 dBA, with hearing protection 

required for personnel exposed to levels of 85 dBA or higher. NASA standards are necessarily more stringent, 

because most noise in space is continuous for 24 hours a day. For Shuttle flights no more than 2 weeks in 

duration, the flight rules call for hearing protections when noise levels reach 74 dBA. For the ISS, the flight rules 

state that hearing protection must be used at and above 67 dBA. A breakdown of hearing-protection 

requirements for ISS is provided in Table 11.1.

Table 11.1: ISS Hearing Protection Requirements Versus 24-hour Noise-Exposure Levels a 

LAeq24 (dBA) b

 65-66 67 68 69 70 71 72 73 74-75 76-77 >77 

Required hours per day 

of hearing protection 0 2 7 11 14 16 17 19 20 21 22 

(full time) 

a From ìISS Generic Operational Flight Rulesî, Volume B, NSTS-12820. February 1997.

b

 Hours are in addition to 2-hour exercise period 

The above exposure limits, where hearing protection is specifically required, address the concern of crew 

hearing loss. NASA stipulates additional requirements to address the concerns of speech communication 

effectiveness and psychological effects, ensuring that noise in space vehicles does not approach the levels 

specified in the flight rules. 

The ISS Flight Crew Integration Standard (SSP-50005) also recommends additional limits on the acoustic 

environment for the crewís habitable volume: 

! Impulsive noise, i.e. noise with duration less than 1 second, shall not exceed 140 dB. 

! Infrasonic noise shall be less than 120 dB in the frequency range from 1 to 16 Hz for a 24-hour exposure. 

The reverberation time in areas where crewmembers must communicate by voice shall be between 0.4 and 

0.6 seconds for sound in the 1000 Hz Octave Band. 

In addition to the LAeq24 noise-exposure limits, NASA ISS specifications include individual limits on the noise 

emitted into the crewís habitable volume by ISS modules, payloads, and government-furnished equipment (GFE). 

These specifications are divided into continuous and intermittent emissions. 

Frequency content is important, because humans are more sensitive to noise in specific frequencies; noise 

that interferes with speech falls within a limited range; and high spikes or levels in some frequencies can be very 

annoying and dominate overall broad-band noise-level concerns. Specifically, these criteria do not address the 

spectral shape of the acoustic environment. To satisfy the need for this more comprehensive and rigorous 

specification, NASA utilizes NC curves, which were developed to quantify how room noise affects speech 

communications. A partial set of the NC curves is provided in Figure 11.1. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 53

10

20

30

40

50

60

70

80

90

63 125 250 500 1K 2K 4K 8K

Sound Pressure Level, dB (re 20 μPa)

Octave Band Center Frequency, Hz

NC

70

65

60

55

50

45

40

35

30

25

20

15

A-wt 

OASPL

(dBA)

77

72

67

63

58

53

49

44

40

36

31

27

Figure 11.1: Noise Criteria Curves x

 Used in Noise Emission Specifications. To use the NC curves, 

compare the acoustic emission of the item, measured at the specified location using a Type 1 microphone 

and analyzed into octave frequency bands using appropriate filtering or spectral analysis, with the 

appropriate NC curve. The sound pressure level in dB (no weighing) in each frequency band measure 

must be equal or lower than the corresponding values of the appropriate NC curve. 

Continuous Noise-Emission Limits 

! Modules in the US segment shall not exceed NC-50 at the center of the moduleís habitable volume, 

including noise emitted by the integrated GFE. In addition, the sleeping environment shall not exceed NC-40 

(SSP 41000). The Russian segment modules have roughly equivalent but different requirements which will not 

be discussed for clarity. 

! The compliment of payload racks in a given module shall not exceed NC-48 when evaluated at the center 

of the moduleís habitable volume (Payload Verification Program Plan, SSP 57011). To implement this 

specification, the NASA Payloads Office has specified that each payload rack shall meet the NC-40 criteria when 

measured 2 feet from the loudest point on the rack (Pressurized Payloads Interface Requirements Document, 

SSP 57000). Furthermore, in order to meet this rack requirement, rack integrators specify a sub-allocation to the 

individual payloads that are typically close to NC-32. 

! Non-Integrated GFE shall not exceed the NC-40 criteria when measured two feet from its loudest point 

(ISS Acoustic Requirements and Testing Document for ISS Non-Integrated Equipment, JSC-28322). 

Intermittent Noise-Emission Limits 

Table 11.2 specifies the intermittent noise-emission limits for ISS payloads and nonintegrated GFE. The 

limits apply to measurements performed 2 feet (0.6 m) from the loudest point on the item. Items that have 

operational durations longer than 8 hours must comply with the continuous noise limits stated above. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 54

Table 11.2: Intermittent Noise Emission Limits a 

Maximum Noise Duration (per 24-hour Period) A-wt OASPL (dBA) b

8 hours ≤ 49 

7 hours ≤ 50 

6 hours ≤ 51 

5 hours ≤ 52 

4 hours ≤ 54 

3 hours ≤ 57 

2 hours ≤ 60 

1 hours ≤ 65 

30 minutes ≤ 69 

15 minutes ≤ 72 

5 minutes ≤ 76 

2 minutes ≤ 78 

1 minute ≤ 79 

Not allowed ≥ 80 

a From Pressurized Payloads Interface Requirements Document, SSP 57000, and ISS Acoustic 

Requirements and Testing Document for ISS Non-Integrated Equipment, JSC-28322. b A-wt OASPL: A-weighted overall sound pressure level is the sound pressure level including acoustic 

energy at al frequencies, with the contributions from the various frequency bands weighted according 

the A-weighting scale which approximates the response of the human ear for high levels of noise. 

Acoustic Risk Mitigation and Countermeasures 

Ground-based testing, empirical predictions, and on-orbit measurements are all used in conjunction with 

remedial actions and countermeasures to maintain a safe acoustic environment on the ISS. First, ground based 

testing is conducted on all noise-producing hardware in order to insure compliance with the specifications. The 

test data, combined with calculations and assumptions about equipment installation and reverberation effects, 

predict the acoustic environment at any stage during a mission. Finally, on-orbit measurements are taken to 

verify that the acoustic environment is appropriate. These on-orbit measurements employ sound level meters to 

measure acoustic spectra and frequency-weighted sound levels at specific locations. Acoustic dosimeters are 

also used to measure the LAeq noise-exposure levels. As a final safety precaution, on-orbit audiometry is 

performed in addition to the pre- and post-mission audiometry to monitor the hearing sensitivity of the crew. 

Noise emission problems are fixed on the ground if possible, but if a problem is identified on-orbit, it is 

reviewed and fixed on-orbit with remedial actions, such as vibration isolators and sound absorbing or blocking 

materials. As a last resort, acoustic countermeasures, such as passive bulk and molded earplugs and active 

noise-control headsets, are employed. 

Design Considerations

For mission durations in excess of 1 year, a low level of ambient noise in the vehicle or habitat environment 

must be achieved on the order of NC-50. Although these levels are achievable, consideration of acoustics must 

be included in the design phase. Simple features such as well-placed absorbent panels, equipment isolators, and 

sound absorbers are efficient and easily incorporated approaches to include in the design phase, but are 

expensive or impossible to employ to an existing vehicle. And the fact that the vehicle might not be accessible, if 

out of Earth orbit, means that the vehicle must not require remedial actions. 

From an acoustic load perspective, we recommend that the crew be provided with a quiet place to recover 

from the higher acoustic levels of the working space without having to use hearing protection. It would be 

desirable to design the sleeping quarters as well as a recreation or meeting area to be especially quiet so that the 

crew can relax and unwind. To help with this, the emerging field of active noise control could be employed to 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 55

eliminate the low frequency noise within these spaces, while more traditional methods might be used to handle 

the high frequency noise. 

11.3 ACCELERATION, VIBRATION, AND IMPACT LIMITS

The maximum deceleration load upon the crew after long-duration microgravity exposure shall be 5G.

11.4 CABIN PRESSURE

To assure crew safety, performance, and health, the internal pressure and air composition in habitable 

elements must be carefully selected. Atmospheric pressure and composition can critically affects the construction 

strength of a habitable vehicle and EVA systems and, therefore, strongly affects overall mission cost. 

A main function of controlling the pressure and composition of the atmosphere is to maintain oxygen partial 

pressure somewhere between the hypoxic and oxygen toxicity or flammability limits. Table 11.3 shows the 

normal oxygen (normoxic) pressures and concentrations at sea level. 

Table 11.3: Oxygen Concentrations at Different Pressures a

Total Pressure (psia) b Normoxic Partial Pressure (psia-O2) Normoxic Concentrations (percentage of O2) 

3.7 3.70 100 

4.0 3.62 90.5 

5.0 3.45 69.0 

6.0 3.36 56.0 

7.0 3.29 47.0 

8.0 3.24 40.0 

9.0 3.20 35.5 

10.0 3.17 31.7 

14.7 3.08 21.0 

a All measurements are taken at sea level 

b

 psia: absolute pressure in pounds per square inch 

Lowering oxygen partial pressure reduces flammability concerns. Therefore, a higher total habitat pressure 

with less concentrated oxygen would be safer. A total habitat atmospheric pressure of 68.9 kPa (10.0 psia) might 

satisfy both the flammability and crew health requirements. Skylab demonstrated, however, that crewmembers 

and selected materials could function well at 34.5 kPa (5.0 psia). 

Crewmember mobility, especially glove dexterity, is improved if the pressure of the EVA system stays low. 

Low suit pressure also reduces overall suit structural weight. To reduce prebreathe time prior to an EVA, the 

cabin pressure should remain as low as possible. The higher the pressure differential between the EVA suit and 

the spacecraft environment, the greater the risk of decompression sickness. 

Shuttle EVA experience reveals that routine EVA operations can be conducted from a 70.3 kPa (10.2 psia) 

cabin, with a 29.6 kPa (4.3 psia) spacesuit after a minimum prebreathe period of 40 minutes. This model 

presents an acceptable bends risk ratio (R) of approximately 1.65. 

Skylab EVAs were conducted with a 34.5 kPa (5.0 psia) cabin environment (70 percent oxygen/30 

percent nitrogen), with a 26.2 kPa (3.75 psia) spacesuit and no prebreathe period. This model 

presented a very-low bends risk ratio (R) of 0.4. We strongly recommend this second, much safer 

Skylab approach. 

For additional background information, trade-off considerations, and references, refer to Appendix A. 

11.5 CO2, TRACE GAS, AND HUMIDITY LIMITS

Crew comfort and health also depend on the proper mix of atmospheric gases and humidity. Carbon dioxide 

(CO2) partial pressure maximum limits for space habitat atmospheres are as follows: 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 56

! 400 N/m2

 (3.0 mm Hg) max for normal operations; 

! 1013 N/m2

 (7.6 mmHg) max 90-day for degraded operations; and 

! 1600 N/m2

 (12.0 mm Hg) max 28-day for emergency operations. 

Dewpoint (humidity) maximum levels for habitat atmospheres are as follows: 

! 278-289 K (40-60 °F) max for normal operations; 

! 274-294 K (35-70 °F) max 90-day for degraded operations; and 

! 274 - 294 K (35-70 °F) max 28-day for emergency operations. 

A wide assortment of trace gases can be found in space habitat atmospheres, each of which is assigned a 

spacecraft maximum allowable concentration (SMAC), typically in concentrations of parts per million (ppm) or 

parts per billion (ppb). 

11.6 MATERIALS SELECTION

The flammability triangle of fuel, oxygen, and ignition source must be broken. Atmospheric pressure and 

composition determine material safety. For example, exceeding 4 percent hydrogen concentration or 30 percent 

O2 concentration greatly increase ignition probability and decrease the list of safe material selections. Habitat 

construction materials must be selected based on their performance during flammability tests at different oxygen 

concentration levels. Additionally, the materials must be able to withstand the total habitat pressure 

recommended above. If the pressure is increased, the materialsí strength must increase accordingly. 

11.7 THERMAL SYSTEMS

The cabin heating, circulation, and cooling systems must closely control air temperature, velocity, pressure, 

and humidity to maintain crew comfort. The comfort zone is defined as that range of environmental conditions in 

which humans can achieve thermal comfort, and is affected by the work rate, clothing, and state of 

acclimatization. Discomfort will be more of a problem as mission length increases, since a thermal system will 

have to maintain comfort in support of a wide range of activities likely during a long-duration mission, from long 

periods of relative inactivity to vigorous activities such as exercise and EVA. Under microgravity conditions, 

sweat does not drip from the body but tends to sheet on the skin form ringlets around the neck. The thermal 

system must provide adequate cooling and air circulation to keep perspiration from exercise and strenuous work 

to a manageable level. Normal atmospheric parameters for thermal comfort are as follows: 

! 12.8 °C (55 °F) for crew workloads of 1000 British thermal units (BTU) per hour; 

! 21.1-26.7 °C (70-80 °F) when workloads are at a minimal 300-600 BTU per hour; and 

! Approximately 50 percent humidity. 

Human Performance in Hot Environments 

Performing heavy work elevates skin temperature, followed by an elevation of body core temperature. The 

body attempts to dissipate heat through vasodilatation and sweating, but this may not completely compensate for 

the heat load on the body. As the core temperature continues to rise, the heart rate increases and eventually may 

reach 140 beats per minute or more. If the body continues to overheat, the crewmember may suffer from heat 

exhaustion, which is characterized by hypertension, difficulty with breathing (dyspnea), confusion, and fainting. A 

person performing moderate or heavy work will develop higher core temperatures before developing heat 

exhaustion. Occasionally, people hard at work in the heat experience almost none of the above symptoms and 

suddenly faint or, in some rare instances, go directly into heat stroke. 

The principal effect of microgravity on heat transfer is the loss of natural convection (i.e., warmer 

air will not naturally rise in microgravity). Therefore, fans or blowers are required to remove heat 

from around objects and to maintain thermal comfort. 

Human Performance in Cold Environments 

During cold stress, the body rapidly reduces peripheral circulation in an attempt to conserve core heat. As the 

core and skin temperatures continue to drop, the individual begins to shiver and will feel continually 

uncomfortable. Eventually, shivering may become violent and uncontrollable. If the core continues to lose heat, 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 57

shivering eventually lessens and then stops altogether. At this point, complete loss of thermoregulation is 

imminent. Death, however, may not come quickly. The core temperature can be drastically reduced, to 26 °C 

(78.6 °F) or lower, and the body may still survive. When the core is cooled to such an extreme level, death can 

occur when attempts are made to rewarm the body, often causing cardiac fibrillation. A hypothermia victim, 

however, becomes critical when the core temperature drops to about 35 °C (95 °F). 

Future mission concepts do not include cryogenic hibernation for the crew, but refrigerated storage of 

deceased crew members may need to be considered. 

Special Ventilation and Metabolic Heat Removal Design Considerations 

The ventilation requirements ventilation of any habitable space element cannot be based on ground-based 

systems due to an absence of connective airflow. 

The amount of air required in any region of the cabin depends on the number of crew present and on their 

work activity. The recommended amount of cabin air for adults engaged in moderate physical activity ranges 

from 2.4 to 14.2 liters/sec (5 to 30 ft3

/min) per person, with approximately two-thirds of this being fresh, revitalized 

air. In a fan-ventilated pressurized suit, the flow rate must be 6 ft3

/min. Special consideration should be given to 

the following areas: 

! Exercise station: This area should have adjustable airflow controls and added ventilation to relieve 

sweating during exercise. Individual airflow units with air-temperature control would help the crewmember match 

the airflow to the activity. The direction of airflow should not blow sweat into other station areas, particularly 

eating or sleeping stations, and should blow over the entire body, not just one part. 

! Sleeping station: Sleeping stations are usually rather small. Individually adjustable airflow controls 

would maximize comfort. 

! Galley: Airflow should not blow loose food around, but should be sufficient to keep food odors from 

accumulating inside the module. 

! Ventilator intakes: Ventilation system intakes should be accessible by the crew for recovery of lost 

objects. Airflow in the vicinity of the inlets should not exceed 0.2 m/sec (40 ft/min). The ventilation rates used in 

the cabin should be sufficient to control local air contamination by body products or from noxious substances in 

the compartment. The cabin ventilation airflow should be sufficient to dilute contaminants and divert them from 

the crewmembers. 

Thermal Monitoring and Control Design Requirements 

! Thermal environment monitoring: Cabin temperature and relative humidity should be monitored 

through an automated system. The number, type, and location of temperature sensors and the frequency of 

monitoring should ensure representative cabin temperature measurements and stable atmospheric control. 

! Visual and audible alarms should be initiated automatically if thermal parameters exceed the limits given 

in Table 11.3. 

! Adjustment of thermal environment by the crew: Crewmembers shall be provided with controls that 

allow them to modify temperatures, humidity, and ventilation rates inside the space module within the ranges for 

these parameters as specified in Table 11.3. 

! Compartment controls: Temperature and ventilation shall be maintained in each of the private crew 

quarters, the personal hygiene area, and the waste management compartment, and shall be controlled in each of 

these areas within the range of these parameters as specified in Table 11.4. 

! Portable fans: If activity stations are isolated from the module air circulation systems, auxiliary airflow 

and/or portable fans shall be provided. 

! Exercise station control: Each exercise station shall be provided with means for sweat removal. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 11: Crew Environment 58

Table 11.4: Atmosphere Thermal Comfort Requirements a

Parameter Operational 28-Day Emergency 

Temperature b 65 - 80 °F (292 - 300 °K) 60 - 85 °F (289 - 303 °K) 

Dew point c 40 - 60 °F (278 - 289 °K) 35 - 70 °F (274 - 294 °K) 

Ventilation 15 - 40 ft/min (0.08 ñ 0.20 m/sec) 10 - 200 ft/min (0.05 - 1.0 m/sec) 

a Source: MSIS Figure 5.8.3.1-1 

b In the operational mode, temperature will be selectable ± 2 °F throughout the range 

c Relative humidity shall be within the range of 25 to 75 percent 

11.8 TOXICOLOGY AND CONTAMINATION LIMITS

Current limits for gaseous contaminants can be obtained from Spacecraft Maximum Allowable Concentration 

(SMAC) specifications (refer to http://www.jsc.nasa.gov/toxicology/ for links to this document and other related 

primary sources). Future ultra-long-duration missions may maintain the same SMACS, or they may be modified if 

prolonged exposure becomes a concern. 

Normal atmosphere scrubbing, sensing, and off-nominal cleanup provisions are required. For representative 

limits and metabolic generation rates, refer to Table XXXVI in the U.S. Segment Specification of SSP-41162. 

According to this standard, airborne microbes must be monitored and limited to 1000 colony-forming units per 

cubic meter. Airborne particulates must be limited to an average of 100,000 particles per ft3

 with a peak of less 

than 2 million particles per ft3

 for sizes ranging from 0.5 microns to 100 microns. 

11.9 REFERENCES

1 Eckart P. The Lunar Base Handbook. Space Technology Series of NASA and US Air Force; 1998. 

2 Booher C. Document No. JSC-33695, ìMan-Systems Integration Standards,î Rev B, Vol 1ñ4. NASA JSC 

Human Factors and Habitability Office; 1995 July. Available on the NASA internal Web site: http://jsc-webpub.jsc.nasa.gov/fpd/shfb/Msis/MSIS_home.htm. 

3 Webb P, editor. Report No. NASA-SP-3006, Bioastronautics Data Book. Washington DC: National 

Aeronautics and Space Administration; 1964. 

4 SSP 41000, System Specification for the International Space Station. 

5 SSP 57000, Pressurized Payloads Interface Requirements Document. 

6 SSP 57011, Payload Verification Program Plan. 

7 JSC 28322, "ISS Acoustic Requirements and Testing Document for ISS Non-Integrated Equipment." 

8 SSP 50005, International Space Station Flight Crew Integration Standard. 

9 Larson W and Pranke L, editors. Human Spaceflight: Mission Analysis and Design. New York: McGraw Hill; 

2001. 

10 Baranek L and Ver I. Noise and Vibration Control Engineering, John Wiley and Sons, Inc.; 1992. 

11 Crocker M. Handbook of Acoustics. John Wiley and Sons, Inc.; 1998. 

12 Bies D and Hansen C. Engineering Noise Control, Theory and Practice. E and FN Spon; 1988. 

13 Report No. 98-126, ìCriteria for a Recommended Standard, Occupational Noise Exposure.î Revised Criteria 

1998, DHHS (NIOSH). 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 12: IT Interfaces 59

12 INFORMATION TECHNOLOGY INTERFACES 

Much of the crewís work in future exploration missions undoubtedly will be conducted with the support of 

intelligent systems at intravehicular workstations. On planetary surfaces, the crew may conduct some tasks with 

the help of robotic assistants or intelligent tools designed to amplify human abilities. Using the present state-ofthe-art to extrapolate what technologies might be available, we envision that the crew and artificial systems (e.g., 

automation, intelligent assistants, and ambulatory robots) will collaborate seamlessly to fulfill exploration goals. 

12.1 KEY CONCEPTS

During the design of every spacecraft system, the engineer is confronted with important decisions as to the 

degree of automation the system will possess and what interfaces the crew will use to monitor or control that 

system as needed. Such decisions must emphasize collaboration between human and machine, capitalizing on 

the unique capabilities of the human user and the intelligent system alike. 

! Technology-driven design: design and development of new systems based on the availability of a new 

technology or capability 

! Human-centered design: design and development of new systems based on the human userís needs 

! Intelligent systems: artificial systems designed to replicate or augment some specific aspect of human 

intelligence (e.g., expert systems) 

! Workstation: the well-equipped location(s) where a crewmember performs a particular kind of work or 

specific task; workstation components include the hardware, the software, and the information technology 

! Information technology: a broad domain encompassing multiple areas, such as robotics, automation, 

vehicle health management, human-centered computing, and intelligent systems, all of which supply important 

infrastructure for mission and spacecraft design 

In the following sections, we consider how to balance the unique but complementary capabilities of human 

and machine, so that introducing new technologies into a mission produces the maximum benefit. In addition, two 

papers (one by Rudisill and one by Stilwell) listed in the references provide detailed information on concerns and

lessons to be learned. 

12.2 DESIGN CONSIDERATIONS

The reality of future exploration missions is that the crew will be completely isolated from society, Earthly 

support, and terrestrial resources for years at a time, meaning that the crewís needs must be supplied solely by 

on-board or surface systems. 

From the very beginning of mission planning and spacecraft design, the paramount consideration 

must be the capabilities, limitations, and needs of the crew.

To date, engineers have exclusively employed a technology-driven design (TDD) approach for providing the 

crew with new or improved interfaces or workstations. In the following paragraphs, we consider why this 

approach does not produce optimal results and how to shift the perspective of the design process to humancentered design. 

Technology-Driven Design 

This approach begins when a designer recognizes the value-added potential of a particular technology. What 

characterizes TDD is the way in which the design is carried out: it begins with a technical concept, proceeds 

through prototype development and testing, and concludes with production and delivery to the human user. Too 

often, the result is a procrustean design that tries to conform the user to the technology. 

Automation provides many examples of how TDD may not work well withóor exclude entirelyóthe human 

component, resulting in an inadequate or unsafe system. We must better understand the strengths and 

deficiencies of humans in an automated environment. Automated systems born from the TDD process tend to 

place the human operator either in an occasional monitoring role or completely out of the loop. When an anomaly 

does occur, the human operator can take control by overriding the automated system, but may be hesitant to do 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 12: IT Interfaces 60

soóeven with compelling evidence of the anomalyóbecause doing so would require the operator to override the 

system without fully understanding how the situation occurred or knowing what effects human-directed changes 

will have. 

Commercial aircraft are so automated that flying from point A to point B only requires the human pilot to enter 

the destination and minimal flight parameters into the flight system. Many accidents occur because pilots place 

too little or too much confidence in automation. When trouble arises, the pilot may merely assume that the 

monitoring instruments have failed. Alternatively, instruments often do not directly reveal the nature of a problem, 

so that the pilot has no indication what to do or what will happen if he or she does take control. The Federal 

Aviation Administrationís Aviation Safety Reporting System permitted the categorization of a large data set of 

aircraft accidents and incidents; that analysis attributes approximately 70 percent to human error. 

Flight deck automation, like the technology-driven model of automation in general, usually provides an 

either/or situation where (1) the pilot must take complete control of the aircraft or (2) the automated system 

maintains complete control. The goal of TDD is not to optimally balance operator workload with automated 

systems, but rather to replace human effort and attention completely. This is often called ìstrong-but-silentî 

automation. 

Human-Centered Design 

Human-centered design (HCD), on the other hand, revolves around the human users themselves. The focus 

shifts to the userís capabilities and needs, his/her tasks, and the most effective way to complete them. HCD 

facilitates human abilities to do difficult tasks and expands human capabilities. It yields new technologies and 

methods for reducing workload, thereby increasing human performance, giving users greater flexibility and 

allowing them the ability to respond more quickly. 

12.3 INTELLIGENT SYSTEMS

Recent history is replete with examples of new technologies that are intended to improve human 

performance, but which had unintended consequences or failed when applied. New technology advances may 

actually add new burdens to operators or may create new types of errors more insidious than those caused by 

prior technologies. Systems sometimes become too complex: even expert users may not recall how to completed 

infrequent but essential tasks and they are not aware of all the features or capabilities. If the new technology is 

not intuitive, it may actually increase a crewmemberís workload beyond human capacity during a crisis. Certainly, 

this unintended outcome is not acceptable, but it can be improved by a shift in the design process that favors 

intelligent systems. 

The real need is not to transfer every bit of data to the crewmember, but rather to create intelligent 

systems that can separate the truly critical results from oceans of irrelevant information. 

Intelligent systems and interfaces treat the human and system as a vast and closely intertwined network of 

interacting and interdependent control loops. By building more cooperative human-machine interfaces, designers 

capitalize on the unique and complementary capabilities of each. Such systems should allow the user to work 

smarter. Poetically, we speak of ìdeep symbiosis between man and machine,î in which complex real-time 

decisions are made to maintain system viability and ìhomeostasisî in the demanding spaceflight environment. 

Table 12.1 lists the defining characteristics of such intelligent systems and interfaces. 

Table 12.1: Defining Characteristics of Intelligent Systems and Interfaces 

Defining Characteristics 

Users can easily monitor fully autonomous system during nominal operations 

Human skill and reasoning can supercede or completely replace autonomous functions during anomalies 

System automation reduces demands on crew but still permits user interaction with system 

System augments human sensory systems, mapping critical new data in an intuitive fashion 

System compensates for natural limitations on human sensory bandwidth by processing and filtering data before displaying 

data points that require crew intervention 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 12: IT Interfaces 61

Defining Characteristics 

Interfaces are very fluid and vary according to changing conditions (results in ìcrew-multiplicationî) 

In this paradigm, the intelligence and quality of the interface permits a very small crew with aboveaverage intelligence and skills to accomplish what legions normally could not. 

The key to success of intelligent systems and interfaces is to involve humans appropriately and to do 

unobtrusively and efficiently. The spacecraft then becomes an extension of the human being. 

12.4 WORKSTATIONS

Beyond the systems and interfaces that support vehicle or habitat operation, the crew also requires welldesigned work areas. The traditional workstation makes sense when work is physically confined to a particular 

location. For example, a blood chemistry analyzer will still have a fixed port for sample delivery, and a glove box 

will still require that a crewmember work in a particular location. The concept of a workstation will change 

drastically in the not-too-distant future, where body-worn computers and head-mounted displays will likely be the 

standard interface for spacecraft systems. As the crew and spacecraft systems journey farther from Earth and 

become more autonomous, the crew must access information quickly and easily and take control of situations 

wherever they are in the spacecraft. Such an immediate interface can only be satisfied by a body-worn system. 

Body-Worn Systems 

Body-worn systems provide significant advantage over the bulky, wired systems of today. If the crew must 

retire to a small radiation shelter, for example, they will still have access to all spacecraft data and controls. 

Control may be exerted by a combination of body-worn mouse, voice, and gesture-based interfaces. Displays 

can be made to appear in front of the crewmember at a comfortable viewing distance and then individually 

customized for the task. Head movements can be used to expand the display and control area. Such a system 

would allow spacecraft systems to be packaged in the densest way possible and to obviate extensive panel 

space. It is also very likely that such a system would contribute greatly to uniformity of design in displays and 

controls, thus increasing the productivity of individual crewmembers. The ready access to decision-support and 

procedural information tailored to each individualís role in a group task will significantly influence how work is 

done in space. 

12.5 DESIGN CONSIDERATIONS

A number of guidelines (MSIS, Section 9.0, Workstations) have been developed for building crew 

workstations and interfaces, but most of these guidelines are too detailed for the scope of this document. Instead, 

the more interesting and important guidelines are provided below. Many of these guidelines may seem like 

common sense, but are often unintentionally violated.

! Tasks must be divided between the crew and spacecraft systems in a way that maximizes the 

skills and abilities of each. As the situation changes, it makes sense for the workload to be dynamically 

assigned to the party most able to handle the task at that time. As part of the HCD process, human factors 

engineers often use task analysis as a formal method for determining how to divide work, but this process often 

looks at tasks statically. New methods may need to be developed to deal with the dynamic allocation of tasks in 

the complex interplay of events that may occur in space. 

! To the greatest extent practical, crew interfaces should be standardized and consistent throughout 

spacecraft system design. 

Architecture 

! Workstation illumination (fixed, portable, or supplementary) should be suited to the task, be adjustable, 

and uniformly cover the work area. Reflections and other stimuli that can interfere with vision should be avoided. 

! Workstation architecture should consider operator needs and capabilities, including physical dimensions, 

viewing angles, and distances (refer to Chapter 8, Anthropometry and Biomechanics). Workstations must 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 12: IT Interfaces 62

accommodate both the S-shaped, bent knee posture of microgravity and the erect posture of a planetary 

environment. 

! Ventilation should be consistent with NHB 8060.1; flow rate and direction should be adjustable. 

! Workstation restraints, such as foot and waist restraints, tethers, and handholds, should be adjustable, 

comfortable, and easy to engage and disengage. They should provide stability. 

! A maintenance-facility workstation should provide conditioned/converted power, spare parts, supplies, 

repair and diagnostic equipment, data links, and a glove box or other contained location for servicing and 

repairing components. It should allow access to computer-based maintenance procedures, diagnostics, and 

interfaces to troubleshooting and built-in test equipment. Ideally, maintenance interfaces should use the same 

body-worn interface available for other spacecraft control systems. 

Controls 

The MSIS outlines the advantages and disadvantages of different controls and supplies detailed guidelines 

for multiple types of hardware controls. Detailed design guidance for multiple types of computer input devices 

(e.g., keyboard, joystick, light pen, mouse, trackball, stylus and grid, touch display, and bar code reader) are also 

given in this standard. Below, we include select guidelines for ungloved operations: 

! Use shape-coding or -separation for blind operation of controls. 

! Label emergency or critical controls. 

! Protect controls from accidental actuation (by location, orientation, recessing, shielding, cover guards, 

interlocks, resistance, locks, or ìdead-manî switch operation). 

! Protective gear should not interfere with normal operation. 

! For natural communication between the crew and machines, language-based voice communication (for 

both input and output) should be considered. New signal processing techniques show great promise for removing 

ambient noise from voice recognition systems, which is currently the greatest limitation of such systems. 

Displays 

Displays are the primary method for providing crew with information about systems, processes, and the 

vehicle or habitat. Although information is mainly conveyed to the crew visually via meters, indicators, signals, 

flags, and graphics-capable monitors, displays can also be auditory. A particular concern is the display of crew 

caution and warning information. The following represents some top-level guidance for display design, while 

detailed design guidance for visual, auditory, and caution and warning displays is provided in MSIS, Section 9.4. 

! Absent a direct crew request, a system should only display information required to perform the task at 

hand. Do not make the displayed information overly complex, but rather provide a simple, direct means to access 

more detailed information. 

! If a fixed display is necessary, place the display surfaces to enhance readability, taking into consideration 

such factors as user height, orientation, viewing distance, glare and reflectance, brightness, contrast, ambient 

illumination, and vibration and acceleration state. 

! Ensure that the source of an alarm can be easily determined. Allow the crew to view alarm history and 

provide the right information and decision support to allow the crew to make decisions appropriately and rapidly in 

an emergency. 

Display/Control Integration 

! All controls should be operable by a pressure-suited crewmember. 

! Group functionally-related displays and controls. Provide clear and readable labels and a common 

interface across functionally similar displays and controls. Arrange the controls by sequence of use or by logical 

flow. 

! Controls and displays for maintenance tasks should not be visible during normal operations, but should 

be readily accessible during maintenance. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 12: IT Interfaces 63

! Locate emergency displays and controls so they can be easily seen and easily reached. Make 

emergency information on displays conspicuous. 

User/Computer Interaction 

Overall, computers should aid the user by providing the required information in an appropriate format. 

Detailed design guidance is provided in MSIS, Section 9.6. 

! Provide visual consistency across screens; give rapid and predictable feedback for all user actions. 

! Design intuitive (i.e., easy-to-learn, easy-to-use) actions or commands that do not require significant 

memorization. 

! Allow escape, cancel, and abort functions for all user actions. 

! Provide all information the user requires to perform the task; do not display extraneous information, but 

allow easy and direct access to more detailed information. 

! Make consequences of user actions across displays consistent; and provide distinctive and meaningful 

abbreviations and acronyms. 

! Prototype displays and allow users to review them and provide feedback. 

! Design the interaction so that the crewmember can concentrate on the task, not the system. 

12.6 INFORMATION TECHNOLOGY

Information technology (IT) is a broad domain encompassing multiple areas, such as robotics, automation, 

vehicle health management, human-centered computing, and intelligent systems. Future exploration crews will 

undoubtedly have access to IT-based systems, and much of their exploration work would be conducted with such 

technologies. 

IT infrastructure can enable exploration missions, increasing safety, efficiency, and performance 

while decreasing cost. 

These benefits will only be accrued, however, to the extent that advanced IT-based systems work 

collaboratively and effectively with their human team members. To do so requires careful mission and system 

design. 

Broadly defined, IT includes the following: 

• Automated or robotic assembly: IT will enable the construction of structures, such as transit vehicles, 

habitats, and observatories, in a 0-g environment or on a planetary surface. The human crew would be 

involved with such construction operations at both low levels (e.g., via teleoperation of robotic 

manipulators) and at high levels (e.g., by commands to an autonomous system). 

• Autonomous science: Science provides the primary underlying purpose for exploration, and some 

science will be conducted autonomously. Humans and IT systems may forge ìcollaborativeî teams, with 

autonomous intelligent systems extending the crewís reach and visibility. With advanced IT systems, the 

level of scientist/system interaction will change, with the crew providing high-level direction and the 

automated systems making basic decisions, planning, executing the plan, and carrying out much of the 

data collection and analysis. 

• Automated operations: IT will enable the automated control of complex systems that support the 

human crew, such as environmental control, life support, and in situ resource production, without regular 

direct human control, using existing industrial automation and process control technologies. Such 

automation will make complex decisions with limited or no human interaction, perhaps operating for long 

periods locally (e.g., on the Mars surface) with little or no direction from the crew or Earth-based mission 

controllers. 

• Human amplification: Fundamental human capabilities of the crew will be ìamplifiedî or enhanced 

through IT. For example, in advanced fighter aircraft, automated flight-control systems enhance the 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 12: IT Interfaces 64

pilotís manual control of the vehicle. This capability could be extended to such areas as hazard 

identification and avoidance. IT systems may be used to amplify human design capabilities with 

collaborative design tools. Finally, IT may amplify human physical capabilities (e.g., strength) and 

sensory powers (e.g., extended vision and enhanced touch). 

12.7 REFERENCES

1 Hine B and Clancy D. ìThe Role of Information Technology in Human Space Explorationî; NASA ARC. 

2001. 

2 NASA-STD-3000, Man-Systems Integration Standards, Section 9.0. 

3 Rudisill M. ìCrew/Automation Interaction in Space Transportation Systems: Lessons Learned from the Glass 

Cockpitî in Proceedings of the Human Space Transportation and Exploration Workshop, Galveston, TX; 

2000. (in publication) 

4 Stilwell DJ. ìThe View from Earth Versus the View from Marsî presented at Human Factors and Ergonomics 

Society Annual Meeting, Houston, TX; 1999 September. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 13: Work Interfaces and Tools 65 

13 WORK INTERFACES AND TOOLS 

When designing a mission, the overall goal is to minimize the amount of resources needed to maintain 

systems. Standardization of interfaces, minimization of actuation loads, adequate access clearances, and 

appropriate body restraints are typical tactics for accomplishing work with the least amount of overhead and the 

best chance of success. Wherever possible, existing designs, standards, and inventory should be used to 

minimize cost. 

Tools in many forms aid humans with their work. In additional to the traditional hand tools, the basic 

spacecraft, information devices, and robotics can be considered to be tools as well. 

Good tool design should include low mass, high strength, minimal input loads, torques, and 

cycles, ambidexterity, ease of repair and cleaning, thermally- and electrically-insulated handles, 

and restraint attachment features. 

By limiting the quantity and complexity of tools and vehicle interfaces, training time and personnel are also 

minimized. 

13.1 TOOLS AND AIDS

The types of aids to be considered for interior or exterior work include the following: 

! Devices for self and incapacitated rescue that use power and gas sources common to EVA suits and 

employ detachable elements; 

! Free-flight units, such as manned maneuvering units for translation and EVA work; 

! Fixed and portable lighting 

! A range of digital still and video cameras designed to work in different lighting situations, such as low 

light, infrared, and ultraviolet; 

! Body restraints and safety and equipment tethers; 

! Heavy equipment carriers, such as sleds, wagons, wheelbarrows, and rover trailers; 

! Secure restraint without relying on manual transport 

! Power and manual hand tools, with gripping aids, wrist straps, and ambidextrous features; 

! Batteries and chargers; 

! Detectors for chemicals, fluids, gases, and leaks; 

! Multi-meter diagnostic tools; 

! A wide range of geological tools that can support mining and science operations; 

! Meteorological and navigation aids, such as barometers, compasses, and binoculars; 

! Recreation items and exercise equipment; 

! Markers, flags, trail-blaze paint, and rock cairns; 

! Walking aids, such as poles; 

! In-situ resource utilization devices, such as sandbags; 

! Shelters, tents, and caches; and 

! Repair tools, such as welders and gas and fluid patches. 

The mass, volume, and specific selection of manifested tools is dependent on the tasks envisioned. For 

future planning based upon past history, microgravity work involving extensive assembly and maintenance could 

require up to 1100 lbs and 30 ft3

 of stowage space for tools and containers. For missions primarily focused on 

planetary science, even more tools may be needed. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 13: Work Interfaces and Tools 66 

The vehicle and science interfaces to be considered for interior or exterior work may include the following. In 

addition to the specific considerations listed for each item, all interfaces must address clearance parameters.: 

! Handrails: cross-sections, spacing, loads, color, labels, mandatory locations 

! Foot restraint attachments: loads, labels, criteria for necessity 

! Tether points: dimensions, loads, criteria for necessity 

! Electrical and fluid connectors: type, sizes, labels, self alignment 

! Electrical and fluid connectors caps/covers: labels, lanyards, self venting, dust-/ultraviolet-proof 

! Electrical and fluid lines: free length, strain relief, bend radius, stiffness, high flexibility or dual wound to 

cancel line memory, restraints/spacing, labels, spacing, vent before fluid line mate/de-mate, trip-proof line runs 

! Mechanical restraints: hard dock, soft dock, alignment aids, latches, bolt heads, self locking, captive, 

tethered, locking pins, max and min torque limits with and without restraint, long life temporary restraints, 

interior/exterior velcro, contingency release, labels, etc 

! Labels and location codes: colors, contrast, fonts, sizes, content, stowage containers 

! Designs to avoid: zippers, lock wire, snaps, exposed external velcro 

13.2 DESIGN CONSIDERATIONS FOR EVA 

Interfaces unique to EVA should consider additional environmental and human factors constraints. 

Externally-mounted displays must be designed to withstand bright solar lighting, vacuum pressures, and extreme 

hot and cold temperatures. Hands-free controls that rely on voice actuation, eye tracking, or whole arm/hand 

tracking, are a desired alternative to fatiguing and imprecise gloved-finger controls. If interfaces internal to the 

suit are devised, they must be safe for a 100-percent oxygen atmosphere and fit within the extremely limited free 

volume of the garment or helmet. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 14: Payload Accommodations 67 

1 4 P A Y L O A D A C C O M M O D A T I O N S 

14.1 PLANT AND ANIMAL FACTORS

Animals 

The inclusion of animalsóprimarily as laboratory specimensóin a spacecraft environment poses several 

challenges. The animals contribute to the consumption of life-support resources and the production of metabolic 

wastes and must be factored into the sizing of the life-support system. The rate at which an animal may tax a lifesupport system varies widely and can fluctuate, depending on the species and reproduction and mortality. Waste 

system maintenance and collection considerations are not insignificantóespecially in the microgravity 

environment. 

During some missions, such as a mature planetary base, animals could be included as a source of food for 

the crew. These animals would likely be marine life, such as fish or shrimp, which could more easily be contained 

and transported than typical livestock. 

Plants/Biomass Production 

An evolved Mars base will probably utilize higher plants to provide full water regeneration, atmospheric 

revitalization, and a significant portion of the crewís food. Such a biomass subsystem could provide the primary 

air revitalization and water recovery functions, eliminating the need for a duplicate mechanical processing 

subsystem. More specifically, the plants consume atmospheric carbon dioxide to produce biomass and oxygen 

through photosynthesis, thus fulfilling the primary air revitalization task. Furthermore, plants filter organic 

compounds from slightly-processed gray water and urine mixed with the hydroponic solution, returning transpirate 

to the water subsystem for final filtering. In the process of fully revitalizing the atmosphere, the crops also provide 

at least half (by mass) of the crewís diet (Drysdale, et al., 1999). When the biomass subsystem produces 

sufficient oxygen beyond the crewís metabolic requirements, the waste subsystem may oxidize solid wastes. 

The biomass subsystem hardware includes a plant chamber and supporting equipment. Plants grown within 

the plant chamber consume carbon dioxide from human metabolic activities and other sources. In return, the 

plant chamber provides edible biomass for the food subsystem, oxygen for the air subsystem, and clean 

transpirate for the water subsystem. An oxygen scrubber concentrates oxygen from the plant chamber, passing it 

to the crew cabin. To control the atmospheric temperature and humidity, an anti-microbial condensing heat 

exchanger dehumidifies the cabin atmosphere. Condensate passes either to the water subsystem for final 

processing or is recycled to the nutrient solution tank. Recycling excess condensate within the biomass 

subsystem reduces the overall load on the water subsystem and helps to dilute incoming gray water sent from the 

water subsystem. In this arrangement, the biomass subsystem provides both the primary air revitalization and 

water purification functions. Inedible biomass passes to the waste subsystem. 

Staple crops that supply mainly carbohydrates, such as sweet potatoes, wheat, and white potatoes, more 

efficiently generate edible dietary mass on a per-photon, per-volume, and per-time basis than other crops. Crops 

that supply protein and fat, such as peanuts and soybeans, are relatively inefficient at generating edible dietary 

mass. Furthermore, while some salad crops are fairly efficient, the dietary intake from these crops is typically low. 

Salad crops are assumed to be cabbage, carrot, chard, fresh herbs, lettuce, onion, spinach, and tomato (Behrend 

and Henninger, 1998). Thus, for flight systems that allow or require some resupply, it would be most expedient to 

grow the crewís dietary carbohydrate and some salad crops while providing protein and fat by resupply from 

Earth. 

Under the NASA Advanced Life Support Straw Man concept, the biomass subsystem uses artificial lighting to 

grow crops. The lighting photoperiod, photosynthetic photon flux levels, and biomass production module 

environmental conditions are set to maximize crop productivity as a function of time. Alternative models consider 

using natural lighting for biomass production, but the available natural light available during some mission profiles, 

such as a Mars mission, may be insufficient to grow most crops. 

Partial Pressures of Carbon Dioxide and Oxygen 

To promote crop productivity, the nominal atmospheric composition for the biomass modules should maintain 

the carbon dioxide partial pressure at 0.12 kPa and the partial pressure of oxygen at 17.27 kPa. This latter value 

for oxygen provides sufficient oxygen partial pressure within the biomass modules to support crew accessibility 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 14: Payload Accommodations 68 

(Lange and Lin, 1998). This minimum oxygen partial pressure allows for reasonably-timed crew acclimation, 

except for the case of maximum oxygen uptake, such as during hard work (Waligora et al., 1994). The remaining 

biomass production module atmospheric constituents are water vapor and an inert gas, such as nitrogen. 

Minimum Growing Area 

! Total closure: The minimum growth area to achieve total closure depends on the available lighting, but 

based on the Biomass Production Chamber tests using moderately high irradiance, we typically estimate that 40 

to 50 m2

 of growing area (continuously planted and harvested) would provide the daily caloric needs, as well as 

the oxygen and any ìwasteî carbon oxidation back to carbon dioxide, for one human. Results from the Russian 

BIOS-3 studies using higher irradiance came out with a area of about 40 m2

. Bugbee and Salisbury estimated 

that this area could be reduced to less than 20 m2

 using wheat and very high irradiance, which wheat can tolerate. 

However, these estimates do not account for a complete diet (i.e., all the minerals and micronutrients). 

! 50-percent closure: This would be half of the of the typical estimate provided above (i.e., half of 50 m2

 is 

25 m2

), except if you consider biomass subsystem variations where oxygen is not used for recycling the waste 

biomass. For example, 20 to 25 m2

 could provide half of the dietary food and all of the oxygen if you only stabilize 

or throw out the inedible biomass. The plants would still have sufficient carbon dioxide from the crew, who would 

get the remainder of their food from stowage. This model does not necessarily preclude recycling nutrients, which 

can be processed relatively rapidly by bioreactors, before significant biomass oxidation occurs. 

Power Requirements 

! Total closure: A high irradiance of 1000 μmol m-2 s-1 is equivalent to approximately 200 W m-2 of 

irradiance. Assuming a lamp efficiency of approximately 20 percent, including electrical conversion, reflector 

efficiency, and crop interception, this would indicate that the subsystem requires 1 kW to provide high lighting for 

each square meter of crop-growing area. Thus, for 40 to 50 m2

, this would come to 40 to 50 kW of electrical 

power for lighting. As a rough estimate, this number could be doubled for cooling, water pumps, fans, and other 

support equipment, for a total of approximately 100 kW per person for total closure. This estimate would change 

significantly, however, if direct, natural lighting can be provided through the use of solar collectors, greenhouses, 

or some other system. 

! 50-percent closure: The above estimate can be halved to 50 kW per person. 

! Salad Machine: (vegetable production unit that augment the food system and would be important for 

long-duration missions). The estimated power requirements will depend on the size of the system and the light 

intensity. Using a lower light intensity, the current thinking suggests that a 5 m2

 system might be sustained with 5 

kW and a 10 m2

 system would require 10 kW. 

Carbon Dioxide Levels 

! Ambient: The optimum carbon dioxide level for most C3 plants (which encompasses all of the crops 

included in the ALS model) typically ranges from 1000 to 2000 ppm at 1 atm pressure (101 kPa). On a partial 

pressure basis, this would come to a partial carbon dioxide level of 0.1 to 0.2 kPa. 

! Minimum Tolerance: Acceptable growth can be sustained at 400 ppm (0.04 kPa), which is perhaps 75 

percent of that obtained at 1000 ppm. Growth drops off linearly when the carbon dioxide drops below this level. 

Some C4 plants (e.g., corn, sorghum, and sugar cane), however, can sustain good growth well below this level, 

perhaps down to 150 ppm. 

! Maximum Tolerance: Some plant species show drops in yield (10 to 25 percent) at 5000 ppm (0.5 kPa), 

while others show no effects. Yield for susceptible plant species drops even more at 10,000 ppm (1.0 kPa). 

There are also some peculiar effects on transpiration rates at these super-elevated levels, but this varies by 

species, as well. Carbon dioxide levels should be kept below 5000 ppm (0.5 kPa), assuming we select crops that 

might be more tolerant of these levels. 

Oxygen Levels 

! Ambient: If carbon dioxide level is elevated to 1000 ppm, then a 21 percent (21 kPa) normal ambient is 

probably the safest way to ensure crop health. Dropping the oxygen down to 10 percent (10 kPa) or even 5 

percent (5 kPa) should not affect photosynthesis, but could affect shoot-tissue respiration during dark cycles and 

root respiration at any time of day. Since dissolved oxygen (DO) is a linear function of the oxygen partial pressure 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 14: Payload Accommodations 69 

above the fluid (in this case, the nutrient solution), and hydroponic growers usually like to keep the DO above 2 to 

3 ppm, at least above 5 percent (5 kPa). Normal saturated DO below 21 percent is approximately eight to nine 

ppm. 

! Minimum tolerance: The minimum oxygen level for healthy crop growth is 5 percent (5 kPa). 

! Maximum tolerance: The maximum oxygen level for healthy crop growth is 25 percent (25 kPa). 

Carbon dioxide levels should be maintained at 1000 ppm, or this high oxygen level will depress photosynthetic 

rates of C3 crops. Also, fire safety becomes a concern at this level. 

Lighting 

! Ambient: The optimal lighting range for relatively high crop productivity is 600 to 800 μmol m-2 s-1. 

! Minimum tolerance: Lighting requirements vary by crops, but some crops will continue to produce under 

lighting conditions as low as 150 μmol m-2 s-1. 

! Maximum tolerance: Grasses, like wheat and rice, can tolerate up to 2000 μmol m-2 s-1. Broad leaf 

crops can only tolerate up to 1000 μmol m-2 s-1. 

Maintenance Issues 

! Air Quality: Volatile organics, especially ethylene gas, should be kept below 50 ppb. 

! Watering systems: Although some types of bacteria are beneficial to plants and can provide them with 

essential nutrients through symbiosis, it is important to monitor the nutrient solutions and plant-growth substrates 

for plant pathogens. Effective countermeasures for pathogen control is also essential. 

! Human access and automation: While automation may well address much of the burden of biomass 

cultivation, hands-on human involvement will be necessary throughout the growth cycle. Besides correction of 

automation failures, the active handling and caring for plants can provide considerable psychological benefits. 

Assuming that human access is worthwhile, a low-pressure greenhouse should be entered with the volume 

pressurized to 5psi, while the crewmember wears a mask delivering 100 percent oxygen. While this will impact 

greenhouse structural strength and mass, it eliminate the time, risk, awkwardness, and fatigue of wearing a 

pressurized EVA suit while providing normal greenhouse support. The benefits and costs of this approach, 

however, have yet to be adequately confirmed. 

! Planetary contamination: Providing direct access to the greenhouse by shirt-sleeved, oxygen-masked 

crewmembers will simplify the operations necessary to minimize the risks of forward and backward biological 

contamination. Direct linkage of the habitat to greenhouse is recommended. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Chapter 15: Planning for Human Operations 70 

15 PLANNING FOR HUMAN OPERATIONS 

15.1 TRAINING

Crew and ground-team training is essential for proper operation of the vehicle, payloads, and medical and 

logistics systems. Preflight training priorities must place a strong focus on crew safety. For short missions, 

mission-success training and detailed choreography is essential. Long flights rely more heavily on basic skills, insitu, just-in-time, and proficiency training. In all cases, clear, concise, and validated procedures are necessary. 

Except for a limited number of emergency procedures, all procedures should rely on readily-accessible hardware 

with electronic displays, such as palmtop computers or head-mounted displays. This allows the same hardware 

that is used to guide in-situ training to be used during actual performance, and permits decision-support to be 

seamlessly integrated into the system. 

Ground-based facilities and personnel are a major influence on human mission costs. Adequately simulating 

tasks in advance of mission launch often requires multiple-part task-training facilities to reproduce all the skills 

needed. Savings can be leveraged by gracefully evolving development test equipment and software into crew 

training hardware. Consolidation and co-location of training facilities, personnel, and equipment is another means 

of achieving cost efficiency. Designs should be assume the need for low-maintenance, long-life, hands-off 

hardware turnaround, simple upgrades, and off-the-shelf components. Operations support facilities that would 

benefit a mission include the following: 

! Computer simulations and system and environment models; 

! Mockups for interiors and exteriors of habitats, airlocks, and rovers; 

! A planetary surface simulator; 

! A unloading system for microgravity and hypogravity; 

! Vacuum chambers (unmanned, manned, environmental, dust rated, and glove-boxes); 

! A neutral buoyancy laboratory; 

! Self-taught training media for ground support and crew; 

! Scale models; and 

! Body and hand scanners. 

15.2 EMERGENCY RESPONSE PROVISIONS

Provisions and design considerations for emergency responses are addressed in Chapter 3 on Vehicle 

Design, Section 3.4, while the psychosocial aspects of the emergency response are addressed in Chapter 7 on 

Psychosocial Interaction, Section 7.3. 

15.3 ALLOCATION OF CREW TIME

Planning for on- and off-duty time of crewmembers, as well as scheduling plans, details, and constraints, are 

discussed in detail in DV-00-014, ìOperations Concept Definition for the Human Exploration of Marsî (2000, 2nd

edition). These constraints were derived from the NASA Crew Procedures Management Plan and from flight 

experience. In addition, some attention is given to allocation of crew time in Chapter 7 on Psychosocial 

Interaction, Section 7.1. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix A: Atmospheric Pressure 71

APPENDIX A: ATMOSPHERIC PRESSURE 

A-1: BACKGROUND

A number of factors and parameters must be considered when selecting an atmosphere (e.g., an acceptable 

oxygen level and pressure regime) for a cabin or spacesuit. The most important consideration is the crewís 

maintained health. Other significant factors include operations and logistics, science activities, and engineering 

tradeoffs, as well as cost and safety. The atmosphere selected must ultimately be a trade-off or compromise 

between all of the above-mentioned factors, with a close regard for the crewís safety, comfort, and performance 

capabilities. 

One of the primary purposes of a human presence in space exploration is to provide a base for doing 

scientific research, both in the vehicle habitat and in extensive and routine EVA. Because of the importance, 

extent, and expense of EVA, it is vital to maximize the crewís productivity during EVA. Selection of the 

atmospheric pressure level and composition has direct critical effects on technology and engineering 

requirements of the EVA systems, but only moderate effects on engineering requirements of the life-support and 

thermal control-systems of the spacecraft cabin and habitat elements. 

A-2: ISTORICAL PERSPECTIVE

A brief historical summary of spacesuit and habitat atmospheres is presented in Table A.1. As seen in the 

table, extensive experience has been gained with both low- and sea-level pressure environments. 

Present space vehicles operate at standard sea-level atmospheric pressure, with the Shuttle orbiter reducing 

the cabin pressure to 70.3 kPa (10.2 psia) prior to EVA operations. The ISS also operates at the nominal sealevel pressure to maintain compatibility with the Shuttle orbiter and the Russian Soyuz vehicles, as well as to 

maintain a ìcontrolî atmospheric environment for conducting material and biological experiments in the 

microgravity environment. Unlike the Shuttle orbiter, the ISS accommodates EVA operations without decreasing 

habitat pressure, but requires a rigorous prebreathe protocol coupled with use of an airlock. 

In previous space programs, habitat pressures have ranged from 34.5 kPa (5.0 psia) to the current 101.4 kPa 

(14.7 psia), while corresponding spacesuit-system pressures to support these space missions have ranged from 

26.2 kPa (3.8 psia) to 40.0 kPa (5.8 psia), as used by the Russians with their Orlan EVA suit for support of 

previous Mir operations and currently for ISS support. It should be noted that prototype advanced spacesuits 

have been developed by NASA to operate at 57.2 kPa (8.3 psia) in order to eliminate extensive overhead 

prebreathe operations. 

For short duration missions of 2 weeks or less, 100 percent oxygen atmospheres at pressures up to 34.5 kPa 

(5.0 psia) have been utilized (e.g., Mercury, Gemini, Apollo missions). Skylab also used a 34.5 kPa (5.0 psia) 

pressure regime, but was a mixed atmosphere of 70 percent oxygen and 30 percent nitrogen. The longest Skylab 

mission was 84 days. 

Russian spacecraft (e.g., Salyut, Soyuz, Mir) environments have utilized mixed oxygen-nitrogen atmospheres 

all at sea-level pressures. For EVA operations, this environment can present a higher level of risk of the 

crewmembers developing decompression sickness (ìbendsî) unless some element of compromise is established 

between the amount of prebreathe time at 100 percent oxygen and the spacesuit operating pressure, both of 

which are contingent upon the vehicle cabin or habitat pressure. In the case of Russian EVA operations and 

based on extensive ground-based altitude chamber testing of over 500 subject runs, the Russian EVA operations 

are conducted with a suit pressure of 40 kPa (5.8 psia) and only 40 to 60 minutes of 100-percent oxygen 

prebreathe time. Although this poses a slightly higher ìbends ratioî risk―the operational values for the 

decompression ratio―their ground-based test results coupled with their extensive EVA operational experience, 

makes this a manageable and acceptable risk. 

The bends ratio has historically ranged from zero to 1.84 and is driven by cabin atmosphere levels (based on 

the concentration of oxygen and pressure regime), prebreathe timelines, and the corresponding operational 

pressure level of the spacesuit. All spacesuit systems to date have utilized 100 percent oxygen atmospheres 

ranging in pressures from 26.2 kPa (3.8 psia) to 40.0 kPa (5.8 psia). 

It should be noted that adjustments to vehicle cabin or habitat pressures and subsequent prebreathing 

operations consume crewmember time, impacts requirements for support equipment, and correspondingly affects 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix A: Atmospheric Pressure 72

overall mission overhead and productivity. Therefore, it is highly desirable or mandatory to minimize or eliminate 

these operational requirements in future space missions where EVA may be a frequent or routine function. 

The ability of the crew to move quickly and efficiently between the vehicle cabin, habitat, and space suit 

atmosphere environments is important for crew safety, productivity, and overall mission success. 

A-3: SELECTION FACTORS AND PARAMETERS 

The following subsections are presented in the form of short synopsis or vignettes of various attributes, 

consideration factors, parameters, and constraints that influence the design and selection of cabin, habitat, and 

spacesuit atmospheres. 

A-4: HUMAN PHYSIOLOGY

Hypoxia 

For crew well being, the most significant component in the atmosphere is oxygen. The partial pressure of 

oxygen at sea-level on Earth is 21.0 kPa (3.06 psia). As the atmosphere is breathed, its components are diluted 

in the lungs by the addition of carbon dioxide and water vapor so that at the alveoli, where oxygen transfer to the 

blood takes place, oxygen partial pressure is 13.8 kPa (2.01 psia). The lower limit of oxygen concentration is 

bounded by the physiologic impact of hypoxia. Although ambient oxygen pressure decreases with increased 

altitude, as does alveolar oxygen pressure, the human body through the process of acclimatization can adapt 

(within limits) to a hypoxic environment and increase the lungís alveolar oxygen pressure. 

A pressure of 25.8 kPa (3.75 psia) with 100 percent oxygen is required to maintain the lung alveolar pressure 

for the human bodyís blood oxygen saturation to be equivalent to sea-level. A sea-level equivalent atmosphere 

can be achieved between 25.8 kPa (3.75 psia) and 101.2 kPa (14.7 psia) by altering oxygen and nitrogen 

concentrations without seriously affecting physiological responses. 

For total cabin pressures above 25.8 kPa (3.75 psia), the oxygen partial pressure can be controlled between 

17.9 kPa (2.6 psia) and 34.5 kPa (5.0 psia), which is used to vary the oxygen percent by volume in the 

atmosphere. The Skylab crews could go from a ground-based sea-level launch environment to the 34.5 kPa (5.0 

psia, with 70 percent oxygen and 30 percent nitrogen) environment of the Skylab cabin and be unable to tell the 

difference as far as energy expenditure and alertness are concerned. The Skylab crews operated at this low 

pressure and atmosphere composition with only the following subjective noted or observations: 

! The lack of convection resulted in a warm feeling, because the rate of heat rejection was reduced. 

! The reduced water boiling point caused a cold feeling after showering due to rapid evaporation of water. 

! Sweat rapidly evaporated during exercise, which helped body cooling. 

! Lower air density reduced voice projection and made whistling difficult. 

Although oxygen pressures significantly below sea-level equivalent values induce hypoxia, an operational 

method for reducing the potential impacts of the effect during a long-duration mission would be to naturally 

acclimatize the crew to lower physiologically-acceptable oxygen pressure levels. Prolonged exposure to low 

oxygen levels in the hypoxia zone requires acclimatization that can be part of normal adaptations required for 

long-duration space missions. 

Oxygen Toxicity 

The upper limit of oxygen acceptability is bounded by central nervous system toxicity above approximately 2.5 

ATM (36.8 psia). For oxygen pressures from about 2.5 ATM to 0.5 ATM (7.35 psia), pulmonary oxygen is limiting. 

At oxygen pressures below 0.5 ATM (7.35 psia), the limitation is uncertain, but there could be long-term 

limitations relating to reduction in circulating blood mass. Symptoms of oxygen toxicity appear dependent on both 

the oxygen partial pressure and time of exposure. This potential condition would favor lower oxygenconcentration levels without placing the crew in a hypoxia zone. Oxygen concentration is also critical to the 

materials selected for use inside the cabin, habitat, and spacesuit environments. As the oxygen concentration 

increases, many materials become more flammable. Given concerns for both the oxygen toxicity factor and the 

flammability factor, lower oxygen pressure regimes would be the preferred choice. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix A: Atmospheric Pressure 

Table A.1. Historical Space Program Habitat and Spacesuit Atmospheres 

 Habitat Spacesuit a Decompression Program 

Crew stay in Habitat (Days) 

Total Pressure (kPa/psia) 

Percent Oxygen 

Total Pressure (kPa/psia) 

O2

Prebreathe (Minutes) 

Bends Ratio (R = ppN2/Suit Pressure)b

Rationale for HabiAtmosphere Selec

Mercury < 2 34.5/5.0 100 -- -- -- Low vehicle mas

cooling; physiologicmissions. 

Gemini 12 34.5/5.0 100 26.2/3.8 -- 0 See Mercury aboveApollo 12 34.5/5.0 100 26.2/3.8 -- 0 See Mercury aboveSkylab 84 34.5/5.0 70 26.2/3.8 -- 0.4 Long-duration cre

reduced oxygen preasons. Nitrogen some evidence thabeneficial as oppdiluents. 

Shuttle  Normal 

10 101.4/14.7 21 29.6/4.3 240 

(contingency) 

2.7 reduced to 1.7 by contingency EVA prebreathe 

Low development c

Shuttle  EVA Preparation 

1 70.3/10.2 28-31 29.6/4.3 40 1.77 reduced to 

1.65 by prebreathe prior to EVA 

Increased crew ppreparation. 

Russian spacecraft 366 101.4/14.7 21 40.0/5.8 40-60 Assumed: low 

requirements. 

a All spacesuits contain 100 percent oxygen atmospheres. b Based on a controlling tissue compartment with a half time for inert gas elimination of 360 minutes. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 74

Decompression Sickness 

Also identified as altitude decompression sickness (ADS), this condition results from the presence of nitrogen 

bubbles in the body after a reduction in ambient pressure. For example, a change from a sea-level cabin 

pressure to a lower spacesuit pressure is a potential source of ADS if no preventive actions are taken. Protective 

measures involve reducing the body tissue nitrogen content by partial equilibrium of the body to a breathing 

medium of 100 percent oxygen or an atmosphere containing a reduced partial pressure of nitrogen. Reduction of 

atmospheric pressure with dissolved diluent gas (nitrogen) in the body results in the creation of gas bubbles in the 

body tissues. Current U.S. and Russian spacecrafts have atmospheres that are very much like that at sea-level. 

This is a conservative atmosphere that assures the well-being of the crew, minimizes flammability concerns, and 

allows concurrent microgravity adaptation without the masking effect of physiologic acclimatization or adaptation 

that might be imposed by a less benign atmosphere. Although a normoxic sea-level pressure is an attractive 

atmosphere for any mission, a number of alternative ìoperationally friendly,î as well as physiologically safe, 

atmospheres can be proposed for future long-term space missions that would help lower the risk of ADS. It 

should be noted that the task of the physiologist or physician involved in considerations of atmosphere selection is 

not to assure that the selected conditions are equal to Earth normal values, but to assure that the atmosphere is 

physiologically acceptable. Physiologically acceptable approaches that maximize engineering, cost, and safety 

factors are strongly encouraged. 

A-5: OPERATIONS AND LOGISTICS 

EVA Prebreathe Time 

EVA appears to be the chief source of ADS, because of the sustained activity and the duration of exposure. 

Current U.S. spacesuit systems used for the Shuttle and ISS operate at 29.6 kPa (4.3 psia) after either a 4-hour, 

100-percent-oxygen prebreathe time or a 24-hour protocol involving a staged cabin decompression from 101.4 

kPa (14.7 psia) to 70.3 kPa (10.2 psia) and a 40-minute oxygen prebreathe. The Russian EVA spacesuit system 

operates at a nominal pressure of 40.0 kPa (5.8 psia) from a 101.4 kPa (14.7 psia) cabin environment after a 

prebreathe time of between 30 and 40 minutes. Russian investigators have studied and verified long-staged 

pressure exposures through extensive ground-based chamber test activities, but they have not required or used 

long pressure-reduced stages to allow lower suit pressures while in flight. While both the U.S. and Russian 

prebreathe procedures would appear to involve some risk of ADS, there have been no reports of ADS during EVA 

operations in either the United States or Russian space programs. 

EVA Crew Performance 

High crew productivity is essential to both IVAs and EVAs, and probably is even more essential for longer 

space missions and future planetary surface exploration. Specifically, EVA crew time spent in prebreathing 

oxygen prior to decompression is basically unproductive, but may have a corresponding positive influence on 

productivity during the EVA if it allows a lower-pressure, more mobile spacesuit and glove system which induces 

less fatigue in the EVA crewmembers. Many EVA tasks and operations involving high-dexterity and/or -mobility 

performance capabilities (especially those tasks and operations involved with future planetary surface operations) 

may be more difficult to achieve in a high-pressure spacesuit system (5.8 to 8.3 psia range), but relatively easier 

to achieve in a lower pressure spacesuit system (3.8 to 4.3 psia range). 

Crew Movements Between Habitat Elements 

If a habitat contains separate elements at different atmospheric pressures or compositions, airlocks would be 

required. Prebreathing would also be necessary to change locations within the habitat, if the pressure difference 

were great enough. Airlocks between habitat elements would also endanger crew by adding to the time required 

for crewmembers to move from one element to another during emergencies, such as solar flares. Hence, it is 

recommended that one common atmosphere be used as often as possible. However, there is a safety benefit in 

being able to close off areas of the habitat during a depressurization or other emergencies. 

Transfer Between Lander and Habitat 

Crew transfer between a lander and a surface habitat may involve decompression. If the crew transfer 

involves wearing an EVA suit, the differences between the pressure in the spacesuit and the lander will determine 

the time spent preparing for decompression. Common pressures between the lander cabin and surface habitat 

could eliminate decompression preparation time, but only if a pressurized rover is used instead of an EVA 

transfer. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 75

Habitat Noise Level 

The noise level in the habitat will be affected by atmospheric pressure. Lower pressures are expected to 

require higher volumetric-flow rates of air through the thermal control and life support subsystems, resulting in 

increased fan and air noise. As noted earlier, noise levels have been a serious problem in prior space missionsó

a problem that has not been solved to date. Aside from the degradation of crew productivity due to constant 

irritation and sleep disruption, acoustic noise can greatly harm verbal communication and, therefore, is a major 

safety hazard, particularly in emergencies. 

Crew Verbal Communication 

Cabin and habitat atmospheric pressure and composition may also affect face-to-face crew communication. 

Atmosphere diluents such as helium, which have much lower density than that of nitrogen, increase the frequency 

of the voice, and at high helium concentrations, may result in decreased intelligibility. Another potential diluent 

gas, argon, has been suggested as a replacement candidate for helium to alleviate the voice communication 

problems. However, since argon is twice as soluble as nitrogen, this poses corresponding problems related to 

ADS and may seriously impact EVA-related operations. 

Pressures lower than about 69.0 kPa (10.0 psia) interfere directly with sound transmission and will degrade of 

a crewmemberís ability to understand speech. This was demonstrated by measurements of speech intelligibility 

during ground-based testing for the Skylab program in a 34.5 kPa (5.0 psia) pressure chamber with ambient noise 

sources. Speech intelligibility of the Skylab on-orbit crewmembers may have also been affected by facial 

distortions caused by the microgravity environment and the lower pressure. Misinterpretation of oral statements 

caused by facial-feature distortion associated with microgravity environments has been reported to annoy or 

upset some crewmembers. 

Logistics 

Atmospheric pressure and composition affect the supply and resupply of gases. Oxygen and diluent gas 

must be carried in sufficient quantities to make up for structural leakage, airlock losses, and contingency 

decompressions. Since a higher pressure (whether in the habitat or spacesuits) increases the rate of leakage, 

lower internal pressures would result in lower initial supply or resupply requirements. Other ways to reduce gas 

losses include increasing the efficiency of airlock gas recovery, reducing overall cabin, habitat, and spacesuit 

leakage sources, and producing gases in situ when possible. Suitable logistic countermeasures for the loss of 

gas supply should be determined for future long-term space missions and planetary surface exploration where 

return and/or resupply may not be possible. 

Flammability 

In general, spacecraft-related fires will be more easily contained and extinguished in atmospheres that have 

lower oxygen concentrations. Higher habitat pressures, coupled with lower cooling air velocities, may reduce the 

rate of combustion by lowering both the oxygen concentration and the rate of supply of oxygen to a fire in an 

enclosed space, such as an electronics cabinet. 

NASA materials flammability requirements are contained in NHB 8060.1, Flammability, Odor, Off-gassing, 

and Compatibility Requirements and Test Procedures for Materials in Environments that Support Combustion. 

The basic requirement is that materials are nonflammable or self-extinguishing when exposed to a standard 

ignition source in an upward flame propagation test (NHB 8060.1 Test 1). Materials that fail this requirement must 

be restricted in use such that they are nonflammable or non-propagating in the ìas usedî condition. Flammable 

materials may be acceptable if located inside a fireproof container with no internal ignition sources that can lead 

to fire propagation. The acceptability of such a configuration can frequently be determined by analysis, but a 

standard container flammability test (NHB 8060.1 Tests 8, 9) is conducted when the analysis is inconclusive. 

When assessing the flammability of spacecraft materials, ignition sources are assumed to be present. The 

absence of ignition sources is not in itself justification for acceptance of flammable materials, although it may be 

used in conjunction with other acceptance rationale. This philosophy was implemented in the aftermath of the 

Apollo 204 fire and has been the basis for material acceptance for all subsequent U.S. crewed spaceflight 

programs. The effect of these requirements is to ensure that all major-use materials are nonflammable or selfextinguishing. Flammable materials are restricted to minor use and are separated from each other such that they 

are non-propagating in their ìas usedî configuration. The following are some general considerations concerning 

materials selection and atmosphere compositions regarding management of flammability requirements: 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 76

! Materials flammability is strongly dependent on oxygen percentage by volume and weakly dependent 

upon oxygen partial pressure. 

! At constant oxygen partial pressure, materials flammability decreases with increasing total pressure. 

! These same considerations apply to fire extinguishment. 

! Materials flammability testing in a 1-g environment is considered to be a conservative approach for 

determining flammability concerns in microgravity environments. 

NASA has extensive experience in control of materials flammability in a 30 percent oxygen, 70.3 kPa (10.2 

psia) atmosphere based on Shuttle flight operations. Although roughly 85 percent of materials are flammable in 

this environment, sufficient non-flammable materials are available to allow a choice of non-flammable materials 

for almost all applications. From a strict flammability standpoint, the 70.3 kPa (10.2 psia), 30 percent-oxygen 

environment would be the recommended atmosphere for future long-term space missions. Cost impacts would 

have to be traded against the increased materials cost for consideration of higher percentage oxygen, lower 

pressure atmosphere regimes. 

A-6: LABORATORY SCIENCE

Life Sciences (Animal and Plant Experiments) 

Laboratory users will have to conduct additional preflight testing and verification on their hardware if mission 

designers choose a lower-than-sea-level pressure for the cabin or habitat. The additional testing and verification 

will be generated by the need for data on science packaging characteristics related to both total pressure and 

oxygen concentration, such as material off-gassing, flammability, and air cooling. Additionally, ground-based 

reference (control base-line) experiments should be performed at conditions similar to the actual spaceflight 

atmosphere conditions to reduce the number of experimental variables. Ground-based experiments in highaltitude (3000 m/10,000 ft.) cities might be used as analogs for spaceflight conditions at pressures as low as 70.3 

kPa (10.2 psia). 

Experimental animal parameters known to be affected by habitat pressure and/or composition include, but 

may not be limited to, the following: 

! Antibody production (guinea pig); 

! Susceptibility to viral infection (mice); 

! Recovery time from infection (mice); and 

! Gas exchange (chicken eggs). 

Plant parameters known to be affected by habitat pressure and/or composition include, but may not be limited 

to, the following: 

! Photosynthesis (wheat, rice, soybean); 

! Water loss by transpiration; and 

! Production of toxic gases. 

If a space or planetary-surface-based habitat is used to generate life science data under atmospheric 

conditions significantly different from Earth sea-level, additional ground-based life science research would be 

required to establish a suitable control database. Development of instruments to measure experimental variables 

may also be affected by different atmospheric conditions. 

Materials Sciences 

Materials science experiments may be influenced by cabin or habitat atmospheric pressure and/or oxygen 

concentration levels. Affected parameters may include, but are not limited to, the following : 

! Use of negative pressure as a method of material containment; 

! Solubility and/or chemical composition; 

! Acoustics; 

! Combustion and chemical reactions; and 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 77

! Heat transfer through surrounding air. 

Use of Off-the-shelf Equipment 

The use of off-the-shelf equipment will be inhibited by increasingly stringent flight requirements at lower 

atmospheric pressures and/or higher oxygen concentrations. 

A-7: HABITATION SYSTEMS

Air Cooling 

The performance of liquid coolant loops in the thermal-control system is not affected by the total cabin or 

habitat atmospheric pressure. However, to provide the required air cooling to the crew and heat-generating 

equipment in the cabin and habitat elements, the thermal-control system has to flow a certain rate of air mass 

through the elements, independent of the cabin or habitat pressure. As the total pressure and air density 

decrease, the required volumetric flow rate of the air-cooling subsystem increases. A similarity analysis shows 

that the blower power requirement of the air-cooling subsystem is inversely proportional to the square of the total 

cabin or habitat pressure. For example, it normally takes 250 to 500 W to provide air cooling in an ISS-sized 

habitat module at 101.3 kPa (14.7 psia). The blower power requirement will be doubled to 500 to 1,000 W at 70.3 

kPa (10.2 psia) and quadrupled to 1.0 to 2.0 KW at 50.6 kPa (7.35 psia). In short, although the thermal-control 

system does not impose a lower limit on the range of the cabin or habitat pressure, the power penalty incurred to 

the air-cooling subsystem practically limits the total pressure to 50.6 kPa (7.35 psia) or higher. 

Use of Off-the-shelf Equipment 

In addition to the previous comments under ìLaboratory Scienceî regarding the use of off-the-shelf 

equipment, the following specific parameters are anticipated to be directly affected: 

! Materials selection (off-gassing, oxidation/corrosion, flammability); 

! Air cooling of equipment (velocity and density); 

! Sound levels (noise production from fans and sound transmission); 

! Certification and verification (preflight testing at operational conditions); and 

! Commonality with other space-program equipment (equipment design). 

A-8: LIFE SUPPORT

Plant Growth 

Plant growth for life support and/or food production may be affected by the habitat atmospheric pressure and 

composition in several ways. Photosynthesis, transpiration, and the release of toxic gases all vary in relation to 

pressure, oxygen concentration, or carbon dioxide concentration. Carbon dioxide concentration has an affect on 

plant growth, with enriched carbon dioxide/low oxygen concentration atmospheres producing higher 

photosynthesis rates. Wheat germination and early growth under atmospheric pressures as low as about 6.0 kPa 

(0.87 psia) have been shown to be possible. However, under these conditions, seedling characteristics, such as 

leaf size and chlorophyll content, were significantly lower than those of control seedlings grown under Earth 

atmospheric conditions. Germination rate was significantly lower except when the atmosphere was composed of 

99.1 percent oxygen. Oxygen is required for wheat germination and growth during its pre-photosynthetic phase. 

Also, microorganism activity, ecology, and population dynamics may be affected by habitat atmospheric pressure 

and composition. Bioengineering of plant-growth characteristics to accommodate appropriate atmospheric 

pressures and concentrations suitable to future space missions should be considered. 

Animal Growth 

Although not fully understood or investigated to any certain conclusion, food-crop animal growth may also be 

affected by habitat atmospheric pressure and/or composition. Known effects on laboratory animals were 

identified previously in this document under ìLife Sciences (Animal and Plant Experimentation).î 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 78

Rehumidification 

Life-support subsystem heat exchangers for removal of atmospheric humidity will tend to over-condense the 

humidity at atmospheric pressures substantially lower than 70.3 kPa (10.2 psia). An additional non-condensing 

heat exchanger or water spray rehumidifier may be required for low habitat pressures. Heat exchangers 

designed specifically for planetary surface habitats however will not necessarily have this tendency. 

Thermal Control 

In addition to comments regarding air cooling in the previous section under ìHabitation Systems,î a cooling 

fanís power and potentially its size must be increased at reduced atmospheric pressures in order to maintain 

equal mass-flow rates. Mass and volume of air-cooling components, such as fans, ducts, and filters, are 

increased in size at reduced atmospheric pressures in order to maintain equal pressure drop with the increased 

volumetric flow rate. In general, the thermal-control system would not have to physically change greatly if the 

cabin or habitat could afford the extra power for lower atmospheric pressures. 

A-9: HEALTH CARE

Habitat atmospheric pressure and composition may affect health care system hardware and operations. 

Health care systems measure or monitor physiologic variables associated with work capacity, lung function, blood 

chemistry, tissue oxygenation, immune system function, and many other physiologic functions that are likely 

affected by atmospheric pressure and composition. The exact nature of these effects, including the effects of 

long-duration exposure to atmospheres that greatly differ from sea-level, is not completely understood and may 

be a confounding factor in medical treatment and diagnosis. Examples of parameters that may affect long-term 

health, ability to perform, or survival of the crew are changes in pressure, dust or particulate matter, temperature, 

water vapor, and the concentrations of oxygen, carbon dioxide, and inert gas. The effects, which could be acute 

or chronic, could occur as a crewmember moves from one mission task to another or from one mission 

environment to another. 

Medical care will include rescue and resuscitation of crewmembers, delivering oxygen therapy and ventilation 

support, providing fluid therapy, performing emergency surgery, and providing intensive care and hyperbaric 

treatment. In other than standard sea-level environments, some medical diagnostic or therapy equipment may 

not function properly. A lot of research also needs to be done to differentiate normal physiologic adaptation to an 

abnormal environment from pathophysiology. 

A-10: CREW ACCOMMODATIONS

Consumables Packaging 

The design of packaging for crew consumables, such as food, is also affected by the difference between 

Earth sea-level pressure and cabin or habitat pressure. If a sea-level facility is used for packaging consumables 

for launch, the trapped air will exert pressure on the packaging materials when exposed to a lower habitat 

pressure. Some foods can be vacuumed-packed, preventing this effect, but other foods, such as bread, cannot 

be vacuumed-packed without destroying their palatability. Frozen foods are also packaged with an air-filled 

space. Earth-based food packaging for habitat pressures much lower than sea-level could require construction of 

specialized food production and packaging facilities on Earth, which would be pressurized to match the missionís 

habitat pressure. Foods would then be produced, packaged, transported, and stored for use at the same ambient 

pressure. Such a food preparation facility would be expensive to construct and operate. 

Food Cooking Time 

Lower habitat pressure reduces the boiling point of water and food substances. The reduced pressure 

impacts food recipes and increases cooking times. The relationship of cooking time to temperature is fooddependent. For cooking of in-situ produced food, crew time required for food production will increase with lower 

habitat pressures, potentially affecting IVA crew productivity. Using a pressure cooker for some foods can reduce 

preparation times. 

Generally, prepared food items are heated below the boiling point of water and served around 60 °C (140 °F), 

which deters the growth of microorganisms. Food-borne illness is caused by microorganisms and is the chief 

concern for the health and safety of the crew. All microorganisms are killed by heat if the temperature is high 

enough and is applied for a sufficient length of time. The relationship of destruction time to temperature is 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 79

microorganism-dependent. The destruction temperature ranges from 60 °C (140 °F) for vegetative bacteria to 

121.1 °C (250 °F) for heat-resistant spore-forming bacteria. 

A-11: STRUCTURES AND MECHANISMS

Pressure Shell Mass 

Cabin and habitat atmospheric pressure and composition may affect structures and mechanisms subsystem 

hardware and operations in the following ways: pressure vessel design may be more severe for higher pressure 

regimes; and seals around hatches and penetrations will be subject to higher loads and will require closer design 

tolerances to reduce leakage. In this instance, higher internal atmospheric pressure requires more exacting 

design and tolerance factors. Pressure vessel mass may be affected by internal pressure in some cases. 

Pressure vessel requirements are related to internal atmospheric pressure, but other considerations, such as 

launch and landing loads, may also drive the thickness. In the case that internal pressure becomes a pressure 

wall driver, increased pressure will result in a higher structural mass. On the other hand, use of the cabin or 

habitat internal atmospheric pressure as a means of structurally stiffening for launch and landing may be 

beneficial in terms of overall mass savings. In this case, higher internal pressure may produce additional 

stiffening and result in a mass savings. Habitat elements at different pressures would require airlocks between 

them, resulting in an increased amount of structure, mass and system complexity. 

A-12: EVA ACCOMMODATIONS

Airlock Gas Recovery 

Habitat atmospheric pressure and composition may affect EVA accommodations subsystem hardware and 

operations in the following ways. Airlock gas losses during depressurization will not be affected by habitat 

pressure, since the final pressure before evacuation is dependent on the depressurization pump technology and 

not the initial pressure. During normal pressure operations, the airlock and other habitable volumes will leak less 

gas to the outside environment at lower pressures. Airlock pump mass, volume, and power are not significantly 

impacted by initial airlock pressure. The airlock pump design is driven by the final pressure before evacuation. 

The power expended during the initial stages of depressurization is very low compared to the power expended 

when the airlock pressure reaches low values such as 3.4 to 6.9 kPa (0.5 to 1.0 psia). 

Spacesuit System Mass and Mobility 

A major issue that strongly affects the overall weight, design, and mobility functions of future spacesuit 

systems is the pressure level and atmospheric composition chosen for operational use. From both test and 

functional experience, EVA crew task productivity can be shown to be related to the spacesuit operational 

pressure levels. This is especially noticeable by suited subjects with pressurized gloves, who experience 

corresponding levels of reduced mobility and increased hand fatigue. Higher suit pressure also tends to drive the 

requirement for increased structural thickness and associated hardware weight increases. The most 

straightforward method of increasing crewmember productivity and decreasing fatigue is to lower the suit 

pressure. From an EVA standpoint, suit pressure should be selected from a range of 26.2to 29.7 kPa (3.8 to 4.3 

psia). Within this range, current spacesuit technology yields excellent body and hand mobility and dexterity 

capabilities and enables a high degree of productivity. Within this operational pressure range, the atmosphere will 

also provide good breathing for performing various work loads and will be suitable for ventilation and cooling 

purposes. 

A-13: REFERENCES

1 Conkin J. Report No. NASA-TM-2000-210188, ìThe Mars Project: Avoiding Decompression Sickness On A 

Distant Planet.î National Space Biomedical Research Institute; 2000 May. 

2 Conkin J. ìHabitat Options to Protect Against Decompression Sickness on Mars.î JSC Environmental 

Physiology Laboratory. 2000 June. 

3 Brown J and others. Report No. JSC-25003, ìInternal Atmospheric Pressure and Composition for Planet 

Surface Habitats and Extravehicular Mobility Units.î 1991 March. 

4 Waligora J, Horrigan D and Nicogossian A. ìThe Physiology of Spacecraft and Space Suit Atmosphere 

Selection,î Acta Astronautica Vol.23. 1991. p 171ñ177. 

5 Woo H. ìEffect of Lower Cabin Pressures on Space Architectures and Operations.î Presented to AIAA 

Architecture Working Group.1990 October. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 80

6 McCarthy, Band, and Green JA. ìOptimum Cabin Pressure Study,î Rockwell International, Space Systems 

Division, February 1991. 

7 Anonymous. NASA Internal Memo EC7-91-06.: ìSurvey to Support SEI Position on Internal Pressure (Crew 

and Thermal Systems Considerations in Selection of Habitat Internal Pressure).î 1991 February. 

8 Pedley M. ìMaterials Flammability Control for Lunar Transportation System and Lunar Habitat: Impacts for 5 

psia, 70 Percent Oxygen and 10.2 psia, 30 Percent Oxygen Environmentsî, Structures and Mechanics 

Division, NASA-JSC. 1991. 

9 Griffin D and Pedley M. ìMaterials Flammability Considerationsî (Materials Selection and Usage for Habitable 

Environments), NASA-JSC. 1992 May. 

10 Hills B. ìCompatible atmospheres for a space suit, space station, and shuttle based on physiological 

principles.î Aviation, Space, and Environmental Medicine; 1985 November. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 81

APPENDIX B: WASTE 

The following tables contain provide detailed information on various waste components.

Table B.1: Waste Components 

Component Kg/Person Per Day Lbs/Person per Day 

Human waste (dry weight) 

Feces 0.03 0.07 

Urine 0.06 0.13 

Shower/hand wash a-c 0.01 0.02 

Sweat 0.02 0.04 

Total 0.12 0.26 

Inedible plant biomass (dry weight) 

Protein 0.25 0.56 

Carbohydrate 0.29 0.64 

Lipids 0.07 0.16 

Fiber 1.09 2.41 

Lignin 0.11 0.24 

Total h 1.82 4.01 

Trash 

Hygiene 

Clothes and towels 0.0007 0.0015 

Toilet paper d 0.0230 0.0507 

Pads and tampons d 0.0035 0.0077 

Menstrual solids d 0.0004 0.0009 

Paper d 0.0650 0.1433 

Subtotal 0.0926 0.2041 

Packaging material i 

Snack packaging 0.060 0.132 

Food containers e 0.470 1.036 

Plastic bags e 0.060 0.132 

Food remains f 0.100 0.220 

Frozen 0.050 0.110 

Refrigerated 0.020 0.044 

Ambient 0.410 0.904 

Beverage j 0.128 0.232 

Straws 0.020 0.044 

Subtotal 1.318 2.906 

Paper 

Wipes 0.140 0.309 

Tissues 0.020 0.044 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 82

Component Kg/Person Per Day Lbs/Person per Day 

Facial tissues 0.030 0.066 

Waste 0.004 0.009 

Subtotal 0.194 0.428 

Tape 

Masking 0.002 0.004 

Conduit 0.004 0.009 

Duct 0.035 0.077 

Subtotal 0.041 0.090 

Filters 

Air 0.0244 0.0540 

Pre-filters 0.0300 0.0660 

Subtotal 0.0544 0.1200 

Miscellaneous 

Teflon 0.0110 0.0240 

PVC 0.0005 0.0010 

Subtotal 0.0115 0.0250 

Total 1.7115 3.7731 

a Shower/hand wash soap = 10 g/person per day. 

b Clothes wash = 25 g/person per day. 

c Hygiene latent water (0.43 kg/person per day), food preparation latent water (0.03 kg/person per day), and laundry latent 

water (0.06 kg/person per day). 

d Cellulosic. 

e Polyethylene. 

f

25 percent protein, 51 percent carbohydrate, 8 percent lipid, and 16 percent fiber. 

g High-efficiency particle accumulators 

h Derived from Hanford A. Baseline Values and Assumptions Document. 1999. i Derived from Grounds P. STS-35 Trash Evaluation Report. NASA TM SP4-91-041, March 1991. 

j Derived from Grounds P. Beverage Pouches. NASA TM SP4-91-081, June 1991. k ECLSS Architecture Description Document. Vol. 2, Book 2, Revision A. 1998. l ISS Air filters (2.15 kg), 29 total. 

Table B.2: Inedible Biomass Calculation for a 20-Day Diet Using All Available Crops a

Crop Average Consumption 

(kg/person per day) 

Harvest Index Inedible Biomass 

(kg/person per day) 

Soybean 0.086 0.37 0.146 

Wheat 0.24 0.4 0.360 

White potato 0.2 0.7 0.086 

Sweet potato 0.2 0.7 0.086 

Rice 0.029 0.4 0.044 

Peanut 0.013 0.27 0.035 

Tomato 0.22 0.48 0.238 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 83

Crop Average Consumption 

(kg/person per day) 

Harvest Index Inedible Biomass 

(kg/person per day) 

Carrot 0.041 0.9 0.005 

Cabbage 0.0038 0.9 0.000 

Lettuce 0.024 0.95 0.001 

Dry bean 0.013 0.37 0.022 

Celery 0.013 0.7 0.006 

Green onion 0.048 0.5 0.048 

Strawberry 0.016 0.4 0.024 

Peppers 0.049 0.4 0.074 

Pea 0.0075 0.37 0.013 

Mushroom 0.0011 0.5 0.001 

Snap bean 0.01 0.37 0.017 

Spinach 0.04 0.8 0.010 

Crop subtotal 1.2544 n/a 1.215 

Resupplied food 0.37 n/a 0.037 

Total 1.62 n/a 1.25 

NOTE: Inedible biomass ratio = 0.77. 

a Crops for 20-day diet chosen by NASAís Advanced Life Support Program. 

Table B.3: Inedible Biomass Calculation for a 20-Day Diet Using Carbohydrate Crops a

Crop Average Consumption 

(kg/person per day) 

Harvest Index Inedible Biomass 

(kg/person per day) 

Soybean 0 0.37 0.000 

Wheat 0.22 0.4 0.330 

White potato 0.17 0.7 0.073 

Sweet potato 0.18 0.7 0.077 

Rice 0 0.4 0.000 

Peanut 0 0.27 0.000 

Tomato 0.21 0.48 0.228 

Carrot 0.04 0.9 0.004 

Cabbage 0.0025 0.9 0.000 

Lettuce 0.021 0.95 0.001 

Dry bean 0.013 0.37 0.022 

Celery 0.0075 0.7 0.003 

Green onion 0.034 0.5 0.034 

Strawberry 0 0.4 0.000 

Peppers 0.031 0.4 0.047 

Pea 0.0038 0.37 0.006 

Mushroom 0.0013 0.5 0.001 

Snap bean 0.01 0.37 0.017 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix B: Waste 84

Crop Average Consumption 

(kg/person per day) 

Harvest Index Inedible Biomass 

(kg/person per day) 

Spinach 0.04 0.8 0.010 

Crop subtotal 0.9841 n/a 0.854 

Resupplied food 0.5 n/a 0.05 

Total 1.48 n/a 0.90 

NOTE: Inedible biomass ratio = 0.61. 

a Crops for 20-day diet chosen by NASAís Advanced Life Support Program. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix C: Sensory Adaptation 85 

APPENDIX C: SENSORY ADAPTATION 

C-1: VESTIBULAR SYSTEM

There are two effects of spaceflight on the human vestibular system that may impair crew performance: 

spatial disorientation and SAS (ìspace sicknessî). Both spatial disorientation and SAS likely stem from a conflict 

between vestibular and other sensory input, such as vision, when compared to expectations of a 1-g environment. 

Approximately 50 percent of crew experience these symptoms, but individual susceptibility cannot be reliably 

predicted. Symptoms are more pronounced during the first 2 to 4 days of microgravity exposure and typically 

dissipate over time. Effects also become progressively less pronounced in individuals with more space 

experience. 

Serious readaptation symptoms occur after a return to Earth from a long period in microgravity. The 

symptoms become more severe the longer an individual stays in microgravity. Russian cosmonauts who spent 

about a year in the microgravity environment were barely able to move upon return to Earth. Even with much 

shorter stays in microgravity, the return to the terrestrial gravitational environment is frequently difficult. A quick 

motion of the head, for example, can induce all the symptoms of motion sickness, including vomiting. 

Crewmembers will likely experience adaptation symptoms when first entering a reduced-gravity environment 

on a planetary surface. The brief trip to the Moon caused few adverse effects in the adaptation to 1/6 g, but there 

is no information on the effects that may occur when a crew spends 6 to 8 months in microgravity and then 

transitions to the 0.38-g of Mars. A change from 6 months of 0-g to 0.38-g might be worse than a return to 1-g. It 

seems unlikely, but we donít know. Based only on our experience with 0-g to 1-g transitions, we might 

hypothesize that the crew would be able to do very little surface exploration and science during the first month of 

a Mars stay due to their physical condition. During the first month on Mars, crew may spend much of their time, 

when not occupied with mission-critical tasks, undergoing a slow and gentle process of rehabilitation. 

Furthermore, the precise effect of multiple gravity transitions―1-g to the microgravity of LEO, then acceleration 

to an orbit around Mars, and finally from Mars orbit to0.38-g―is also not known. 

Spatial Disorientation is exhibited primarily as postural and movement illusions (e.g., induced perception of 

tumbling or spinning, vertigo, and dizziness), and can occur when eyes are open or closed. SAS symptoms, 

which are similar to Earth-based motion sickness, can vary from individual to individual, ranging from stomach 

ìawarenessî or nausea to repeated episodes of vomiting, and may be accompanied by pallor and sweating. As 

with similar conditions on the planetary surface, many crewmembers can maintain a basic level of performance 

with SAS symptoms, but it is still advisable to allow an adaptation period after major gravity transitions. Some 

crewmembers with severe symptoms show significant performance decrements, others less. These effects may 

become particularly serious during emergencies. 

It is difficult to design countermeasures for this problem, and anti-motion sickness drugs (typically a 

scopolamine/dexedrine combination) do not completely prevent symptoms. Restricting head movements can 

help. Prior flight experience can reduce symptoms, and biofeedback can both prevent and reduce symptoms to 

some extent. 

C-2: VISION

Little is known about the effects of microgravity on the human visual system, especially during long-duration, 

exploration missions. Most data are anecdotal evidence. 

The most important effects on vision are derived from acceleration and vibration. Because acceleration 

effects depend on the direction of the force vector, high accelerations can render visual displays useless. 

Vibration-related visual effects range from minimal to severe, with severity dependent on the frequency and 

amplitude of the vibration. With severe vibration, vision can be seriously affected, decreasing visual display and 

instrument readability and thereby degrading overall performance. Visual displays and instruments to be used 

during high vibration periods (e.g., launch, re-entry) should be designed to account for this reduced readability 

(e.g., character size and contrast; sufficient illumination for photopic vision). 

In the space environment, differences in light transmission and reflectance reduce visual perceptual cues 

(understandably, this is especially pronounced during EVA). Rapidly changing brightness levels over a broad 

intensity range, high contrasts (caused by reduced light scattering given the absence of an atmosphere), and 

rapid brightness drop-off combine to significantly reduce visual cues and may affect crew performance. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix C: Sensory Adaptation 86 

Anecdotal reports from crewmembers aside, there is no substantive objective evidence to verify that normal 

vision is altered in microgravity. Therefore, vision under nominal conditions in space should be considered 

reliable, at least across the mission durations experienced thus far. 

Display Design Considerations 

High accelerations can render visual displays useless. Vibration-caused visual effects may be minimal to 

severe, depending on the frequency and amplitude of the vibration. Severe vibration can impair display and 

instrument readability and can make visual performance difficult or impossible. Visual displays and instruments 

used under high vibration (e.g., launch or re-entry) should be designed to increase readability, by increasing 

character size and contrast, for example. For additional information on display design considerations, refer to 

Chapter 8 on Crew Accommodations, section 8.3. 

C-3: HEARING

There is no evidence that human hearing is altered in microgravity. However, noise and vibration in space 

caused by fans that circulate the internal air and cool equipment is the bigger problem. Even low-level noise can 

interfere with normal communications and increase fatigue through sleep disturbance and sensory irritation. 

Extreme noise and extended noise exposure can cause pain and permanent hearing loss. 

Design Considerations 

Sound-dampening, vibration-absorbing materials can greatly reduce noise and vibration throughout a 

spacecraft or habitat. These materials should be incorporated into payload racks, fan housings, and around other 

high noise and vibration machinery. Special care should be used when selecting materials to enclose crew sleep 

areas. For additional information on other noise considerations, refer to Chapter 11 on Crew Environment, 

section 11.2. 

C-4: SMELL AND TASTE

Microgravity causes a head-ward shift in body fluids, as well as nasal congestion, reducing both smell and 

taste. Crewmembers regularly increase the seasoning in their food, because of a decrease in taste. Fortunately, 

humans do not strongly rely on the sense of smell for information. 

The internal atmosphere of a spacecraft in microgravity contains a higher number of particulate and microbial 

contaminants, because particles do not settle out. This can cause odors and disease during a long-duration 

mission. Microbial contaminants will cause sickness if not properly managed. 

Design Considerations 

! Food: Prepackaged food must be highly acceptable by crewmembers to ensure they maintain 

appropriate caloric intake. The inclusion of condiments and seasonings in the food system will allow crewmember 

to adjust food according to personal taste. See Chapter 8 on crew accommodations for more information on food 

system considerations. 

! Smell: It will be important to keep surfaces clean during long-duration missions. Surfaces in the galley 

and personal hygiene areas should be constructed of mold- and bacterial-growth-resistant materials, and stowage 

should include a selection of low-fume, nontoxic cleaning products. The air system must be designed to both filter 

and circulate the atmosphere throughout the vehicle. 

The vehicle must also be equipped with multiple sensors for detecting smoke and chemical, gas, and 

biological leaks. Since the crews sense of smell will be diminished and cannot be relied on to sense slight 

changes in atmospheric odors, the sensors must detect spills and leaks before they become health hazards. 

Refer to Chapter 11 on Crew Environment, section 11.8 for more information. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model 87

APPENDIX D: CREW RESOURCE MODEL 

D-1: ABOUT THE MODEL

This resource model considers system-level components only and excludes the mass and volume of several 

common components of the habitat architecture and life support system: 

! Potable and hygiene water because the quantity needed depends on onboard reserves and the 

reclamation system used 

! Structural and integration hardware needed to install or attach crew accommodations, such as lockers, 

racks, dividers, and so on 

! Spares or replacement parts, because the quantities needed are based on system reliability 

! Contingency supplies, because the quantities needed require separate analysis of potential failures 

The suggested mass and volume factors used in this resource model are estimates based on historical data, 

with some educated guesses that assume new technologies with more efficient designs will be available. 

The Excel file includes a number of spreadsheets, which together permit you to make basic calculations and 

compare crew accommodations for at least four types of mission scenarios. Mass and volume factors for each 

mission scenario are provided for 11 accommodations systems (refer to Tables 1 and 2 at the end of this 

appendix or to the spreadsheet for the actual values); while these factors are educated or best guesses, they 

should be changed to accommodate the particular parameters of each mission design. The calculations 

spreadsheet allows you to enter the basic parameters (type, crew size, and duration) of a mission design and 

produces total mass and volume amounts. The system subtotals spreadsheet summarizes the calculated data by 

system, in both table and graphic format for easy comparison to other designs. 

D-2: INSTRUCTIONS 

The model is available as an Excel file (CrewAccom_v3.xls) online at advtech.jsc.nasa.gov under References.

The tabs along the bottom of the spreadhsheet provide all of the information required to calculate and compare. 

1 Enter parameters: click on the spreadsheet called ìCalculationsî to enter the parameters of the mission 

(Figure D-1). In the upper left hand corner of this sheet are three cells or menus that allow you to enter your 

particular parameters. 

Figure D-1: Entering Parameters into the Calculation Spreadsheet 

2 Mission Type: select from one of the four mission types that approximates your mission design (you can 

alter the actual mass or volume factors to further tailor the resource model to your design). 

! Shuttle-like mission: generally a short, 14-21 day mission with little need for self-sufficiency 

! Station-like mission: approximately 90 day or more in duration that can take advantage of Earth re-supply 

and proximity but could benefit from some self-sufficiency 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model 88

! Lunar base: expected to be about 180-365 days and where moderate self-sufficiency is needed 

! Mars habitation module: occupied for an extended period of time of 6-8 months in transit or up to about 

700 days on the surface and which requires considerable self-sufficiency 

3 Crew size: select a value (up to 10) from the pull-down menu. 

4 Duration: enter the mission duration in days. Upon hitting return, the spreadsheet automatically 

calculates the mass and volume of crew accommodations and totals the items. Both the factors used for 

calculation and their units are shown. Some items in the model are affected by both duration and number of crew 

and some are not. 

For example, if you select ìMars habitationî for the mission type, a crew size of 6, and type in ì600î, you have 

indicated that you are interested in a surface habitat model rather than a transit habitat one. 

5 Review results: by selecting the ìSystems Subtotalsî tab, you can view the distribution of masses and 

volumes. This is NOT the final step of the model; as with any model, you must look carefully at the data and 

decide whether it truly fits your design. 

6 Tailoring the model: based on the particular needs of your mission design, you may want to modify 

values or add or remove elements from the model. The model should not be slavishly applied, but should be 

modified to tailor it to your specific mission application. If a particular element does not apply to a particular 

mission, it should be allocated zero resources in the model. If you need more of something, youíll need to 

increase the value in the appropriate table of factors. On the following pages, the tables of mass and volume 

factors used in the model are provided. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model Table D.1: Mass Factors for Crew Accommodations in Various Mission Types 3

Factors given are for hypothetical Shuttle-like, Station-like, lunar base, and Mars habitation missions, showing how the model might be custoThe notation "kg/p/d" indicates kilograms/person/day.

Mass Factors 

Crew Accommodations System 

Shuttle-like Station-like Lunar base Mars habitat Units 

Assumption

Galley and Food System 

Food 2.3 2.3 2.3 2.3 kg/p/d Minimum is 1.8 kg/p/d (current Freezer(s) 100 400 kg Empty freezer (no food mass inConventional ovens 50 50 50 50 kg Microwave ovens 70 70 70 70 kg Assumes 2 ovens Cleaning supplies 0.25 0.25 0.25 0.25 kg/d Includes solvents and supplies Sink and spigot 15 15 15 15 kg For food rehydration and drinkiDishwasher 40 40 kg Cooking/eating supplies 0.5 0.5 2 5 kg/p 

Waste Collection System

System 45 45 45 90 kg Assumes 1 toilet for each missSupplies 0.05 0.05 0.05 0.05 kg/p/d Contingency collection mittens/bags 0.23 0.23 0.23 0.23 kg/p/d 

Personal Hygiene

Shower 0 75 75 75 kg Handwash/mouthwash faucet 8 8 8 8 kg 

3 From: Chapter 18, "Crew Accommodations,î in Human Spaceflight Mission Analysis and Design. Stilwell, D., Boutros, R., and J. Co

Companies, 1999. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model 

Personal hygiene kit 1.8 1.8 1.8 1.8 kg/p Hygiene supplies 0.075 0.075 0.075 0.075 kg/p/d Consumables 

Clothing4

Clothing 69 214 69 99 kg/p Assumes 2.3 kg/p for 1 compleWashing machine 0 0 100 100 kg Clothes dryer 0 0 60 60 kg 

Recreational Equipment

Personal stowage 10 25 25 50 kg/p 

Housekeeping

Vacuum 13 13 13 13 kg Prime and 2 spares Disposable wipes for housecleaning 0.15 0.30 kg/p/d Trash compactor/trash lock 0 150 150 150 kg Trash bags 0.05 0.05 0.05 0.05 kg/p/d 

Operational Supplies and Restraints

Operational supplies 10 20 20 20 kg/p Includes diskettes, Ziplocs, tapRestraints 25 83 50 100 kg 

Maintenance Assumes all repairs in habitabl

Hand tools and accessories 100 200 200 300 kg Spare parts and consumables - Assumes no spare parts or conTest equipment 50 100 300 500 kg Includes oscilloscopes, gauges

4 This is an important trade to consider for long-duration mission because it involves supplying complete sets of clothes for the duratio

clothes cleaning system. By default, this model assumes that a washer/dryer system is not appropriate for Shuttle- or Station-like missions lunar/Mars missions includes cleaning and reuse of clothing. Generally, the following rule of thumb applies: if the mass (washer+dryerclothing (duration*crew size*0.46 kg/p/d), then a cleaning system should be considered to lower clothing mass. The mass factor 0.46 kg/p/of clothes and a clothing change every 5 days. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model 

Other tools and equipment 50 50 600 1000 kg Includes fixtures, large machine 

Photography Assumes an all-digital approac

Equipment 120 120 120 120 kg Includes still and video camera

Sleep Accommodations

Sleep provisions 9.00 9.00 9.00 9.00 kg/p Includes sleep restraints only 

Crew Health Care

Exercise equipment 145 145 145 145 kg Assumes 2 devices for aerobic Medical/surgical/dental suite 15 250 500 1000 kg Medical/surgical/dental consumables 125 250 500 kg 

Table D.2: Volume Factors for Crew Accommodations in Various Mission Types5.

Factors given are for hypothetical Shuttle-like, Station-like, lunar base, and Mars habitation missions, showing how the model might be custThe notation "kg/p/d" indicates kilograms/person/day. 

Volume Factors 

Crew Accommodations System 

Shuttlelike Station- like Lunar base Mars habitat Units 

Assumptions 

Galley and Food System

Food 0.0080 0.0080 0.0080 0.0080 m3/p/d Freezer(s) 0 0 0.50 2.00 m3Conventional ovens 0.25 0.25 0.25 0.25 m3Microwave ovens 0.30 0.30 0.30 0.30 m3 Assumes 2 ovens Cleaning supplies 0.0018 0.0018 0.0018 0.0018 m3/d Includes solvents and supplies for 

5 From: Chapter 18, "Crew Accommodations,î in Human Spaceflight Mission Analysis and Design. Stilwell, D., Boutros, R., and J. Co

Companies, 1999. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model 

Sink and spigot 0.0135 0.0135 0.0135 0.0135 m3 For food rehydration and drinking wDishwasher 0 0 0.56 0.56 m3Cooking/eating supplies 0.0014 0.0014 0.0056 0.014 m3/p 

Waste Collection System

System 2.18 2.18 2.15 4.36 m3 Assumes 1 toilet for each mission Supplies 0.0013 0.0013 0.0013 0.0013 m3/p/d Contingency collection mittens/bags 0.0008 0.0003 0.0008 0.0008 m3/p/d 

Personal Hygiene

Shower 0 1.41 1.41 1.14 m3Handwash/mouthwash faucet 0.01 0.001 0.01 0.01 m3Personal hygiene kit 0.005 0.005 0.005 0.005 m3/p Hygiene supplies 0.0015 0.0015 0.0015 0.0015 m3/p/d Consumables 

Clothing6

Clothing 0.224 0.720 0.224 0.336 m3/p Assumes 0.008m3/p for 1 complete Washing machine 0 0 0.75 0.75 m3Clothes dryer 0 0 0.75 0.75 m3

Recreational Equipment

Personal stowage 0.19 0.38 0.38 0.75 m3

Housekeeping

Vacuum 0.07 0.07 0.07 0.07 m3 Prime and 2 spares Disposable wipes for housecleaning 0.001 0.002 0 0 m3/p/d 

6 This is an important trade to consider for long-duration mission because it involves supplying complete sets of clothes for the duratio

clothes cleaning system. By default, this model assumes that a washer/dryer system is not appropriate for Shuttle- or Station-like missions lunar/Mars missions includes a cleaning system and reuse of clothing. Generally, the volume factor assumes 0.008 m3/p for 1 change of 

every 5 days. 
 GUIDELINES AND CAPABILITIES FOR DESIGNING HUMAN MISSIONS

Appendix D: Crew Resource Model 

Trash compactor/trash lock 0 0.3 0.3 0.3 m3Trash bags 0.001 0.001 0.001 0.001 m3/p/d 

Operational Supplies

Operational supplies 0.001 0.002 0.002 0.002 m3/p Includes diskettes, Ziplocs, tapeÖ Restraints 0.135 0.54 0.27 0.54 m3/kg 

Maintenance Assumes all repairs in habitable ar

Hand tools and accessories 0.33 0.66 0.66 1.00 m3Spare parts and consumables - Assumes no spare parts or consumTest equipment 0.15 0.3 0.9 1.50 m3 Includes oscilloscopes, gauges, etOther tools and equipment 0.25 0.25 3.00 5.00 m3 Includes fixtures, large machine to

Photography Assumes an all-digital approach 

Equipment 0.50 0.50 0.50 0.50 m3 Includes still and video cameras, le

Sleep Accommodations Does not include recommended 1.

Sleep provisions 0.10 0.10 0.10 0.10 m3/p Includes sleep restraints only (suita

Crew Health Care

Exercise equipment 0.19 0.19 0.19 0.19 m3 Assumes 2 devices for aerobic exeMedical/surgical/dental suite 0.25 1.00 2.00 4.00 m3Medical/surgical/dental consumables 0.64 1.30 2.50 m3