1 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

HUMAN SPACEFLIGHT

Review of U.S. 

Plans Committee
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“We choose...to do [these] things,

not because they are easy, but because they are hard...”

John F. Kennedy

September 12, 1962

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Table of Contents

Preface ...................................................................................................................................... 7

Executive Summary ...................................................................................................................................... 9

Chapter 1.0 Introduction............................................................................................................................... 19

Chapter 2.0 U.S. Human Spaceflight: Historical Review ............................................................................ 27

Chapter 3.0 Goals and Future Destinations for Exploration ........................................................................ 33

3.1 Goals for Exploration ............................................................................................................... 33

3.2 Overview of Destinations and Approach.................................................................................. 33

3.3 Mars First.................................................................................................................................. 35

3.4 Moon First ................................................................................................................................ 37

3.5 The Flexible Path to Mars......................................................................................................... 40

3.6 Summary of Strategies for Exploration Beyond Low-Earth Orbit........................................... 43

Chapter 4.0 Current Human Spaceflight Programs...................................................................................... 47

4.1 The Space Shuttle .................................................................................................................... 47

4.2 The International Space Station ............................................................................................... 51

4.3 The Constellation Program....................................................................................................... 57

Chapter 5.0 Launch to Low-Earth Orbit and Beyond .................................................................................. 63

5.1 Evaluation Methodology for Launch Vehicles......................................................................... 63

5.2 Heavy Lift to Low-Earth Orbit and Beyond............................................................................. 64

5.3 Crew Launch to Low-Earth Orbit ............................................................................................ 68

5.4 Additional Issues in Launcher Selection .................................................................................. 72

Chapter 6.0 Program Options and Evaluation.............................................................................................. 77

6.1 Evaluation Criteria.................................................................................................................... 77

6.2 Key Decisions and Integrated Options..................................................................................... 79

6.3 Integrated Options Constrained to the FY 2010 Budget........................................................... 84

6.4 Moon First Integrated Options Fit to the Less-Constrained Budget......................................... 85

6.5 Flexible Path Integrated Options Fit to the Less-Constrained Budget ..................................... 91

6.6 Comparisons Across Integrated Options .................................................................................. 94

Chapter 7.0 Critical Technologies for Sustainable Exploration ................................................................... 99

7.1 Fundamental Unknowns........................................................................................................... 99

7.2 Propellant Storage and Transfer in Space................................................................................. 100

7.3 In Situ Propellant Production and Transport............................................................................. 101

7.4 Mars Orbit to Surface Transportation....................................................................................... 102

7.5 Advanced Space Propulsion ..................................................................................................... 102

7.6 Technology Summary............................................................................................................... 103

Chapter 8.0 Partnerships............................................................................................................................... 105

8.1 International Partnerships......................................................................................................... 105

8.2 U.S. Intra-Government Partnerships......................................................................................... 107

Chapter 9.0 Concluding Observations.......................................................................................................... 111

9.1 Establishing Goals.................................................................................................................... 111

9.2 Matching Resources and Goals ................................................................................................ 111

9.3 NASA Management Challenges............................................................................................... 112

9.4 Systems Engineering ................................................................................................................ 113

9.5 Procuring Systems.................................................................................................................... 113

9.6 Managing the Balance of Human and Robotic Spaceflight...................................................... 114

9.7 Concluding Summary ............................................................................................................... 115

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Appendices

A. Committee Member Biographies.............................................................................................. 117

B. Committee Staff........................................................................................................................ 123

C. Review of U.S. Human Space Flight Plans Statement of Task ................................................ 127

D. Charter of the Review of U.S. Human Space Flight Plans Committee .................................... 131

E. List of Full Committee Meetings and Locations...................................................................... 135

F. Briefers and Committee Contacts............................................................................................. 137

G. Communications and Public Engagement................................................................................ 141

H. Bibliography ............................................................................................................................. 145

Glossary Acronyms and Abbreviations ................................................................................................... 153

Back Cover: The Space Shuttle as it moves through the fog on its way down the 3 1/2–mile crawlerway enroute

to Launch Pad 39A. Source: NASA

5 Review of U.S. Human Spaceflight Plans Committee

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HUMAN SPACEFLIGHT

Review of U.S. 

Plans Committee
Over the next 10 years, NASA is scheduled to devote $99 

billion to the nation’s human spaceflight program. In recognition of the magnitude of these planned expenditures, 

coupled with questions about the status of the current human spaceflight program, the White House Office of Science and Technology Policy, as part of the due diligence of a 

new administration, called for an independent review of the 

present and planned effort. Two conditions framed this request: all ongoing human spaceflight work by NASA and its 

contractors was to continue uninterrupted during the review 

process; and the review team’s findings were to be available 

90 days from the Committee’s formal establishment and a 

formal report be published thereafter, in recognition of the 

demands of the federal budget preparation cycle. 

The Committee established to conduct the review comprised 

10 members with diverse professional backgrounds, including scientists, engineers, astronauts, educators, executives 

of established and new aerospace firms, former presidential 

appointees, and a retired Air Force General. The Committee 

was charged with conducting an independent review of the 

current program of record and providing alternatives to that 

program (as opposed to making a specific recommendation) 

that would ensure that “the nation is pursuing the best trajectory for the future of human spaceflight—one that is safe, 

innovative, affordable and sustainable.”

Initially, the directive to the Committee was that it conduct 

its inquiry with the assumption that operation of the Space 

Shuttle would terminate in 2010 and that the 10-year funding profile in the FY 2010 President’s budget would not be 

exceeded. In subsequent discussions between the Committee chairman and members of the White House staff, it was 

agreed that at least two program options would be presented 

that comply with the above constraints; however, if those 

options failed to fully satisfy the stated study objectives, additional options could be identified by the Committee. No 

other bounds were placed on the Committee’s work.

The Committee wishes to acknowledge the highly professional and responsive support provided to it by the staff of 

NASA, as well as the staff of the Aerospace Corporation, 

which provided independent analysis in support of the review. Aerospace worked under the direction of the Committee, and all findings in this report are those of the Committee. 

Individuals to whom the Committee is particularly indebted 

for sharing their views are listed in Appendix B.

The Committee members appreciate the trust that has been 

placed in them to conduct an impartial review that could 

have a major impact on the nation’s human spaceflight program, human lives and America’s image in the world. We 

view this as a very great responsibility.

 

 October 2009

 Washington, DC

Preface

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8 Review of U.S. Human Spaceflight Plans Committee

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HUMAN SPACEFLIGHT

Review of U.S. 

Plans Committee
The U.S. human spaceflight program appears to be on an 

unsustainable trajectory. It is perpetuating the perilous practice of pursuing goals that do not match allocated resources. 

Space operations are among the most demanding and unforgiving pursuits ever undertaken by humans. It really is 

rocket science. Space operations become all the more difficult when means do not match aspirations. Such is the 

case today.

The nation is facing important decisions on the future of human spaceflight. Will we leave the close proximity of lowEarth orbit, where astronauts have circled since 1972, and 

explore the solar system, charting a path for the eventual 

expansion of human civilization into space? If so, how will 

we ensure that our exploration delivers the greatest benefit 

to the nation? Can we explore with reasonable assurances 

of human safety? Can the nation marshal the resources to 

embark on the mission?

Whatever space program is ultimately selected, it must be 

matched with the resources needed for its execution. How 

can we marshal the necessary resources? There are actually 

more options available today than in 1961, when President 

Kennedy challenged the nation to “commit itself to the goal, 

before this decade is out, of landing a man on the Moon and 

returning him safely to the Earth.”

First, space exploration has become a global enterprise. 

Many nations have aspirations in space, and the combined 

annual budgets of their space programs are comparable to 

NASA’s. If the United States is willing to lead a global program of exploration, sharing both the burden and benefit of 

space exploration in a meaningful way, significant accomplishments could follow. Actively engaging international 

partners in a manner adapted to today’s multi-polar world 

could strengthen geopolitical relationships, leverage global 

financial and technical resources, and enhance the exploration enterprise.

Second, there is now a burgeoning commercial space industry. If we craft a space architecture to provide opportunities 

to this industry, there is the potential—not without risk—that 

the costs to the government would be reduced. Finally, we 

are also more experienced than in 1961, and able to build on 

that experience as we design an exploration program. If, after designing cleverly, building alliances with partners, and 

engaging commercial providers, the nation cannot afford to 

fund the effort to pursue the goals it would like to embrace, 

it should accept the disappointment of setting lesser goals.

Can we explore with reasonable assurances of human safety? 

Human space travel has many benefits, but it is an inherently 

dangerous endeavor. Human safety can never be absolutely 

assured, but throughout this report, safety is treated as a sine 

qua non. It is not discussed in extensive detail because any 

concepts falling short in human safety have simply been 

eliminated from consideration.

How will we explore to deliver the greatest benefit to the 

nation? Planning for a human spaceflight program should 

begin with a choice about its goals—rather than a choice 

of possible destinations. Destinations should derive from 

goals, and alternative architectures may be weighed against 

those goals. There is now a strong consensus in the United 

States that the next step in human spaceflight is to travel beyond low-Earth orbit. This should carry important benefits 

to society, including: driving technological innovation; developing commercial industries and important national capabilities; and contributing to our expertise in further exploration. Human exploration can contribute appropriately to 

the expansion of scientific knowledge, particularly in areas 

such as field geology, and it is in the interest of both science 

and human spaceflight that a credible and well-rationalized 

strategy of coordination between them be developed. Crucially, human spaceflight objectives should broadly align 

with key national objectives.

These more tangible benefits exist within a larger context. 

Exploration provides an opportunity to demonstrate space 

leadership while deeply engaging international partners; to 

inspire the next generation of scientists and engineers; and 

to shape human perceptions of our place in the universe. 

The Committee concludes that the ultimate goal of human 

exploration is to chart a path for human expansion into the 

solar system. This is an ambitious goal, but one worthy of 

U.S. leadership in concert with a broad range of international partners.

The Committee’s task was to review the U.S. plans for human spaceflight and to offer possible alternatives. In doing 

so, it assessed the programs within the current human spaceflight portfolio; considered capabilities and technologies a 

future program might require; and considered the roles of 

commercial industry and our international partners in this 

enterprise. From these deliberations, the Committee developed five integrated alternatives for the U.S. human spaceflight program, including an executable version of the current program. The considerations and the five alternatives 

are summarized in the pages that follow.

Key Questions to Guide the Plan for

Human Spaceflight

The Committee identified the following questions that, if 

answered, would form the basis of a plan for U.S. human 

spaceflight:

1. What should be the future of the Space Shuttle?

2. What should be the future of the International Space

Station (ISS)?

3. On what should the next heavy-lift launch vehicle be 

based?

4. How should crews be carried to low-Earth orbit?

5. What is the most practicable strategy for exploration

beyond low-Earth orbit?

Executive Summary

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The Committee considers the framing and answering of 

these questions individually and consistently to be at least as 

important as their combinations in the integrated options for 

a human spaceflight program, which are discussed below. 

Some 3,000 alternatives can be derived from the various 

possible answers to these questions; these were narrowed to 

the five representative families of integrated options that are 

offered in this report. In these five families, the Committee 

examined the interactions of the decisions, particularly with 

regard to cost and schedule. Other reasonable and consistent 

combinations of the choices are possible (each with its own 

cost and schedule implications), and these could also be considered as alternatives.

CURRENT PROGRAMS

Before addressing options for the future human exploration 

program, it is appropriate to discuss the current programs: 

the Space Shuttle, the International Space Station and Constellation, as well as the looming problem of “the gap”—the 

time that will elapse between the scheduled completion of 

the Space Shuttle program and the advent of a new U.S. capability to lift humans into space.

Space Shuttle 

What should be the future of the Space Shuttle? The current 

plan is to retire it at the end of FY 2010, with its final flight 

scheduled for the last month of that fiscal year. Although 

the current administration has relaxed the requirement to 

complete the last mission before the end of FY 2010, there 

are no funds in the FY 2011 budget for continuing Shuttle 

operations. 

In considering the future of the Shuttle, the Committee assessed the realism of the current schedule; examined issues 

related to the Shuttle workforce, reliability and cost; and 

weighed the risks and possible benefits of a Shuttle extension. The Committee noted that the projected flight rate 

is nearly twice that of the actual flight rate since return to 

flight in 2005 after the Columbia accident two years earlier. 

Recognizing that undue schedule and budget pressure can 

subtly impose a negative influence on safety, the Committee finds that a more realistic schedule is prudent. With the 

remaining flights likely to stretch into the second quarter of 

FY 2011, the Committee considers it important to budget 

for Shuttle operations through that time.

Although a thorough analysis of Shuttle safety was not 

part of its charter, the Committee did examine the Shuttle’s 

safety record and reliability, as well as the results of other 

reviews of these topics. New human-rated launch vehicles 

will likely be more reliable once they reach maturity, but 

in the meantime, the Shuttle is in the enviable position of 

being through its “infant mortality” phase. Its flight experience and demonstrated reliability should not be discounted. 

Once the Shuttle is retired, there will be a gap in the capability of the United States itself to launch humans into space. 

That gap will extend until the next U.S. human-rated launch 

system becomes available. The Committee estimates that, 

under the current plan, this gap will be at least seven years. 

There has not been this long a gap in U.S. human launch 

capability since the U.S. human space program began. 

Most of the integrated options presented below would retire 

the Shuttle after a prudent fly-out of the current manifest, 

indicating that the Committee found the interim reliance on 

international crew services acceptable. However, one option does provide for an extension of the Shuttle at a minimum safe flight rate to preserve U.S. capability to launch 

astronauts into space. If that option is selected, there should 

be a thorough review of Shuttle recertification and overall 

Shuttle reliability to ensure that the risk associated with that 

extension would be acceptable. The results of the recertification should be reviewed by an independent committee, 

with the purpose of ensuring that NASA has met the intent 

behind the relevant recommendation of the Columbia Accident Investigation Board. 

International Space Station 

In considering the future of the International Space Station, 

the Committee asked two basic questions: What is the outlook between now and 2015? Should the ISS be extended 

beyond 2015?

The Committee is concerned that the ISS, and particularly its 

utilization, may be at risk after Shuttle retirement. The ISS 

was designed, assembled and operated with the capabilities of 

the Space Shuttle in mind. The present approach to its utilization is based on Shuttle-era experience. After Shuttle retirement, the ISS will rely on a combination of new international 

vehicles and as-yet-unproven U.S. commercial vehicles for 

cargo transport. Because the planned commercial resupply 

capability will be crucial to both ISS operations and utilization, it may be prudent to strengthen the incentives to the commercial providers to meet the schedule milestones. 

Now that the ISS is nearly completed and is staffed by a full 

crew of six, its future success will depend on how well it is 

used. Up to now, the focus has been on assembling the ISS, 

and this has come at the expense of exploiting its capabilities. 

Utilization should have first priority in the years ahead.

The Committee finds that the return on investment from the 

ISS to both the United States and the international partners 

would be significantly enhanced by an extension of its life to 

2020. It seems unwise to de-orbit the Station after 25 years 

of planning and assembly and only five years of operational 

life. A decision not to extend its operation would significantly 

impair the U.S. ability to develop and lead future international spaceflight partnerships. Further, the return on investment from the ISS would be significantly increased if it were 

funded at a level allowing it to achieve its full potential: as the 

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nation’s newest National Laboratory, as an enhanced testbed 

for technologies and operational techniques that support exploration, and as a management framework that can support 

expanded international collaboration. 

The strong and tested working relationship among international partners is perhaps the most important outcome of 

the ISS program. The partnership expresses a “first among 

equals” U.S. leadership style adapted to today’s multi-polar 

world. That leadership could extend to exploration, as the 

ISS partners could engage at an early stage if aspects of exploration beyond low-Earth orbit were included in the goals 

of the partnership agreement. (See Figure i.)

The Constellation Program 

The Constellation Program includes the Ares I launch vehicle, capable of launching astronauts to low-Earth orbit; 

the Ares V heavy-lift launch vehicle, to send astronauts and 

equipment to the Moon; the Orion capsule, to carry astronauts to low-Earth orbit and beyond; and the Altair lunar 

lander and lunar surface systems astronauts will need to explore the lunar surface. As the Committee assessed the current status and possible future of the Constellation Program, 

it reviewed the technical, budgetary, and schedule challenges 

that the program faces today.

Given the funding upon which it was based, the Constellation 

Program chose a reasonable architecture for human exploration. However, even when it was announced, its budget depended on funds becoming available from the retirement of 

the Space Shuttle in 2010 and the decommissioning of ISS in 

early 2016. Since then, as a result of technical and budgetary 

issues, the development schedules of Ares I and Orion have 

slipped, and work on Ares V and Altair has been delayed.

Most major vehicle-development programs face technical 

challenges as a normal part of the process, and Constellation is no exception. While significant, these are engineering problems that the Committee expects can be solved. But 

these solutions may add to the program’s cost and delay its 

schedule. 

The original 2005 schedule showed Ares I and Orion available to support the ISS in 2012, two years after scheduled 

Shuttle retirement. The current schedule now shows that 

date as 2015. An independent assessment of the technical, 

Figure i. Diagram of the International Space Station showing elements provided by each of the international partners. Source: NASA

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budgetary and schedule risk to the Constellation Program 

performed for the Committee indicates that an additional delay of at least two years is likely. This means that Ares I and 

Orion will not reach the ISS before the Station’s currently 

planned termination, and the length of the gap in U.S. ability 

to launch astronauts into space will be at least seven years.

The Committee also examined the design and development 

of Orion. Many concepts are possible for crew-exploration 

vehicles, and NASA clearly needs a new spacecraft for 

travel beyond low-Earth orbit. The Committee found no 

compelling evidence that the current design will not be acceptable for its wide variety of tasks in the exploration program. However, the Committee is concerned about Orion’s 

recurring costs. The capsule is considerably larger and more 

massive than previous capsules (e.g., the Apollo capsule), 

and there is some indication that a smaller and lighter fourperson Orion could reduce operational costs. However, a 

redesign of this magnitude would likely result in more than 

a year of additional development time and a significant increase in development cost, so such a redesign should be 

considered carefully before being implemented. 

CAPABILITY FOR LAUNCH TO LOW-EARTH 

ORBIT AND EXPLORATION BEYOND

Heavy-Lift Launch to Low-Earth Orbit and 

Beyond 

No one knows the mass or dimensions of the largest hardware 

that will be required for future exploration missions, but it will 

likely be significantly larger than 25 metric tons (mt) in launch 

mass to low-Earth orbit, which is the capability of current 

launchers. As the size of the launcher increases, the result is 

fewer launches and less operational complexity in terms of assembly and/or refueling in space. In short, the net availability 

of launch capability increases. Combined with considerations 

of launch availability and on-orbit operations, the Committee 

finds that exploration would benefit from the availability of 

a heavy-lift vehicle. In addition, heavy-lift would enable the 

launching of large scientific observatories and more capable 

deep-space missions. It may also provide benefit in national 

security applications. The question this raises is: On what system should the next heavy-lift launch vehicle be based? 

Potential approaches to developing heavy-lift vehicles are 

based on NASA heritage (Shuttle and Apollo) and (EELV) 

Evolved Expendable Launch Vehicle heritage. (See Figure 

ii.) Each has distinct advantages and disadvantages. In the 

Ares-V-plus-Ares-I system planned by the Constellation 

Program, the Ares I launches the Orion and docks in lowEarth orbit with the Altair lander launched on the Ares V. 

This configuration has the advantage of projected very high 

ascent crew safety, but it delays the development of the Ares 

V heavy-lift vehicle until after the Ares I is developed.

In a different, related architecture, the Orion and Altair are 

launched on two separate “Lite” versions of the Ares V, providing for more robust mission mass and volume margins. 

Building a single NASA vehicle could reduce carrying and 

operations costs and accelerate heavy-lift development. Of 

these two Ares system alternatives, the Committee finds the 

Ares V Lite used in the dual mode for lunar missions to be 

the preferred reference case. 

The Shuttle-derived family consists of in-line and side-mount 

vehicles substantially derived from the Shuttle, thereby providing greater workforce continuity. The development cost 

of the more Shuttle-derived system would be lower, but it 

would be less capable than the Ares V family and have higher recurring costs. The lower lift capability could eventually 

be offset by developing on-orbit refueling.

The EELV-heritage systems have the least lift capacity, requiring almost twice as many launches as the Ares family to 

attain equal performance. If on-orbit refueling were developed and used, the number of launches could be reduced, 

but operational complexity would increase. However, the 

EELV approach would also represent a new way of doing 

business for NASA, which would have the benefit of potentially lowering development and operational costs. This 

would come at the expense of ending a substantial portion of 

the internal NASA capability to develop and operate launchers. It would also require that NASA and the Department of 

Defense jointly develop the new system.

All of the options would benefit from the development of inspace refueling, and the smaller rockets would benefit most 

of all. A potential government-guaranteed market to provide 

fuel in low-Earth orbit would create a strong stimulus to the 

commercial launch industry. 

The Committee cautions against the tradition of designing 

for ultimate performance at the expense of reliability, operational efficiency, and life-cycle cost.

Crew Access to Low-Earth Orbit

How should U.S. astronauts be transported to low-Earth 

orbit? There are two basic approaches: a governmentFigure ii. Characteristics of heavy-lift launch vehicles, indicating 

the EELV and NASA heritage families. Source: Review of U.S. 

Human Spaceflight Plans Committee

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operated system and a commercial transport service. The 

current Constellation Program plan is to use the government-operated Ares I launch vehicle and the Orion crew 

capsule. However, the Committee found that, because of 

technical and budget issues, the Ares I schedule no longer 

supports ISS needs. 

Ares I was designed to a high safety standard to provide astronauts with access to low-Earth orbit at lower risk and a 

considerably higher level of safety than is available today. 

To achieve this, it uses a high-reliability rocket and a crew 

capsule with a launch-escape system. But other combinations of high-reliability rockets and capsules with escape 

systems could also provide that safety. The Committee 

was unconvinced that enough is known about any of the 

potential high-reliability launcher-plus-capsule systems to 

distinguish their levels of safety in a meaningful way.

The United States needs a 

means of launching astronauts 

to low-Earth orbit, but it does 

not necessarily have to be 

provided by the government. 

As we move from the complex, reusable Shuttle back 

to a simpler, smaller capsule, 

it is appropriate to consider 

turning this transport service 

over to the commercial sector. 

This approach is not without 

technical and programmatic 

risks, but it creates the possibility of lower operating costs 

for the system and potentially 

accelerates the availability of 

U.S. access to low-Earth orbit by about a year, to 2016. 

If this option is chosen, the 

Committee suggests establishing a new competition for 

this service, in which both 

large and small companies 

could participate. 

Lowering the cost of space 

exploration

The cost of exploration is 

dominated by the costs of 

launch to low-Earth orbit and 

of in-space systems. It seems 

improbable that significant 

reductions in launch costs 

will be realized in the short 

term until launch rates increase substantially—perhaps 

through expanded commercial activity in space. How 

can the nation stimulate such activity? In the 1920s, 

the federal government awarded a series of guaranteed 

contracts for carrying airmail, stimulating the growth 

of the airline industry. The Committee concludes that 

an exploration architecture employing a similar policy 

of guaranteed contracts has the potential to stimulate a 

vigorous and competitive commercial space industry. 

Such commercial ventures could include the supply of 

cargo to the ISS (planning for which is already under 

way by NASA and industry – see Figure iii), transport 

of crew to orbit and transport of fuel to orbit. Establishing these commercial opportunities could increase 

launch volume and potentially lower costs to NASA 

and all other launch services customers. This would 

have the additional benefit of focusing NASA on a 

more challenging role, permitting it to concentrate its 

efforts where its inherent capability resides: in develFigure iii. Congressional guidance in FY 2008 NASA Authorization and Appropriation Acts and 

other national policies concerning commercial use of space and commercial crew capabilities. 

Source: U.S. Government

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oping cutting-edge technologies and concepts, defining programs, and overseeing the development and 

operation of exploration systems.

In the 1920’s the federal government also supported the 

growth of air transportation by investing in technology. 

The Committee strongly believes it is time for NASA to 

reassume its crucial role of developing new technologies 

for space. Today, the alternatives available for exploration systems are severely limited because of the lack of 

a strategic investment in technology development in past 

decades. NASA now has an opportunity to generate a 

technology roadmap that aligns with an exploration mission that will last for decades. If appropriately funded, a 

technology development program would re-engage minds 

at American universities, in industry, and within NASA. 

The investments should be designed to increase the capabilities and reduce the costs of future exploration. This 

will benefit human and robotic exploration, the commercial space community, and other U.S. government users 

alike.

FUTURE DESTINATIONS FOR EXPLORATION

What is the strategy for exploration beyond low-Earth orbit? 

Humans could embark on many paths to explore the inner 

solar system, most particularly the following: 

• Mars First, with a Mars landing, perhaps after a brief test 

of equipment and procedures on the Moon.

• Moon First, with lunar surface exploration focused on developing the capability to explore Mars. 

• A Flexible Path to inner solar system locations, such as 

lunar orbit, Lagrange points, near-Earth objects and the 

moons of Mars, followed by exploration of the lunar surface and/or Martian surface. 

A human landing followed by an extended human presence on Mars stands prominently above all other opportunities for exploration. Mars is unquestionably the 

most scientifically interesting destination in the inner 

solar system, with a planetary history much like Earth’s. 

It possesses resources that can be used for life support 

and propellants. If humans are ever to live for long periods on another planetary surface, it is likely to be on 

Mars. But Mars is not an easy place to visit with existing technology and without a substantial investment of 

Figure iv. A summary of the Integrated Options evaluated by the Committee. Source: Review of U.S. Human Spaceflight Plans Committee

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resources. The Committee finds that Mars is the ultimate destination for human exploration of the inner solar system, but it is not the best first destination.

What about the Moon first, then Mars? By first exploring the 

Moon, we could develop the operational skills and technology for landing on, launching from and working on a planetary 

surface. In the process, we could acquire an understanding 

of human adaptation to another world that would one day 

allow us to go to Mars. There are two main strategies for 

exploring the Moon. Both begin with a few short sorties to 

various sites to scout the region and validate lunar landing 

and ascent systems. In one strategy, the next step would be 

to build a lunar base. Over many missions, a small colony 

of habitats would be assembled, and explorers would begin 

to live there for many months, conducting scientific studies 

and prospecting for resources to use as fuel. In the other 

strategy, sorties would continue to different sites, spending 

weeks and then months at each one. More equipment would 

have to be brought to the lunar surface on each trip, but more 

diverse sites would be explored and in greater detail. 

There is a third possible path for human exploration beyond 

low-Earth orbit, which the Committee calls the Flexible Path. 

On this path, humans would visit sites never visited before 

and extend our knowledge of how to operate in space—

while traveling greater and greater distances from Earth. 

Successive missions would visit lunar orbit; the Lagrange 

points (special points in space that are important sites for 

scientific observations and the future space transportation 

infrastructure); and near-Earth objects (asteroids and spent 

comets that cross the Earth’s path); and orbit around Mars. 

Most interestingly, humans could rendezvous with a moon 

of Mars, then coordinate with or control robots on the Martian surface, taking advantage of the relatively short communication times. At least initially, astronauts would not 

travel into the deep gravity wells of the lunar and Martian 

surface, deferring the cost of developing human landing and 

surface systems.

The Flexible Path represents a different type of exploration 

strategy. We would learn how to live and work in space, 

to visit small bodies, and to work with robotic probes on 

the planetary surface. It would provide the public and other 

stakeholders with a series of interesting “firsts” to keep them 

engaged and supportive. Most important, because the path 

is flexible, it would allow for many different options as exploration progresses, including a return to the Moon’s surface or a continuation directly to the surface of Mars. 

The Committee finds that both Moon First and Flexible Path 

are viable exploration strategies. It also finds that they are 

not necessarily mutually exclusive; before traveling to Mars, 

we might be well served to both extend our presence in free 

space and gain experience working on the lunar surface. 

INTEGRATED PROGRAM OPTIONS

The Committee has identified five principal alternatives for 

the human spaceflight program. They include one baseline 

case, which the Committee considers to be an executable 

version of the current program of record, funded to achieve 

its stated exploration goals, as well as four alternatives. 

These options and several derivatives are summarized in 

Figure iv.

The Committee was asked to provide two options that fit 

within the FY 2010 budget profile. This funding is essentially flat or decreasing through 2014, then increases at 1.4 

percent per year thereafter, less than the 2.4 percent per year 

used by the Committee to estimate cost inflation. The first 

two options are constrained to the existing budget.

Option 1. Program of Record as Assessed by the 

Committee, Constrained to the FY 2010 budget. 

This option is the program of record, with only two changes 

the Committee deems necessary: providing funds for the 

Shuttle into FY 2011 and including sufficient funds to deorbit the ISS in 2016. When constrained to this budget profile, Ares I and Orion are not available until after the ISS 

has been de-orbited. The heavy-lift vehicle, Ares V, is not 

available until the late 2020s, and there are insufficient funds 

to develop the lunar lander and lunar surface systems until 

well into the 2030s, if ever. 

Option 2. ISS and Lunar Exploration, Constrained 

to FY 2010 Budget. This option extends the ISS to 2020, 

and begins a program of lunar exploration using a derivative 

of Ares V, referred to here as the Ares V Lite. The option 

assumes completion of the Shuttle manifest in FY 2011, and 

it includes a technology development program, a program to 

develop commercial services to transport crew to low-Earth 

orbit, and funds for enhanced utilization of the ISS. This option does not deliver heavy-lift capability until the late 2020s 

and does not have funds to develop the systems needed to 

land on or explore the Moon in the next two decades. 

The remaining three alternatives fit a different budget profile—one that the Committee judged more appropriate for 

an exploration program designed to carry humans beyond 

low-Earth orbit. This budget increases to $3 billion above 

the FY 2010 guidance by FY 2014, then grows with inflation 

at what the Committee assumes to be 2.4 percent per year. 

Option 3. Baseline Case—Implementable Program 

of Record. This is an executable version of the Pro- gram of Record. It consists of the content and sequence 

of that program–de-orbiting the ISS in 2016, developing 

Orion, Ares I and Ares V, and beginning exploration of the 

Moon using the Altair lander and lunar surface systems. The 

Committee made only two additions it felt essential: budgeting for the completion of remaining flights on the Shuttle 

manifest in 2011 and including additional funds for the de15 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION
orbit of the ISS. The Committee’s assessment is that, under 

this funding profile, the option delivers Ares I and Orion in 

FY 2017, with human lunar return in the mid-2020s. 

Option 4. Moon First. This option preserves the Moon 

as the first destination for human exploration beyond lowEarth orbit. It also extends the ISS to 2020, funds technology advancement, and uses commercial vehicles to carry 

crew to low-Earth orbit. There are two significantly different variants to this option. Both develop the Orion, the Altair 

lander and lunar surface systems as in the Baseline Case. 

Variant 4A is the Ares V Lite variant. This option retires the 

Shuttle in FY 2011 and develops the Ares V Lite heavy-lift 

launcher for lunar exploration. Variant 4B is the Shuttle extension variant. It offers the only foreseeable way to eliminate the gap in U.S. human-launch capability: by extending 

the Shuttle to 2015 at a minimum safe-flight rate. It also 

takes advantage of synergy with the Shuttle by developing a 

heavy-lift vehicle that is more directly Shuttle-derived than 

the Ares family of vehicles. Both variants of Option 4 permit human lunar return by the mid-2020s. 

Option 5. Flexible Path. This option follows the Flexible Path as an exploration strategy. It operates the Shuttle 

into FY 2011, extends the ISS until 2020, funds technology 

advancement and develops commercial services to transport 

crew to low-Earth orbit. There are three variants within this 

option. They all use the Orion crew exploration vehicle, together with new in-space habitats and propulsions systems. 

The variants differ only in the heavy-lift vehicle used.

Variant 5A is the Ares V Lite variant. It develops the 

Ares V Lite, the most capable of the heavy-lift vehicles in 

this option. Variant 5B employs an EELV-heritage commercial heavy-lift launcher and assumes a different (and 

significantly reduced) role for NASA. It has an advantage of potentially lower operational costs, but requires 

significant restructuring of NASA. Variant 5C uses a 

Shuttle-derived, heavy-lift vehicle, taking maximum advantage of existing infrastructure, facilities and production capabilities.

All variants of Option 5 begin exploration along the flexible 

path in the early 2020s, with lunar fly-bys, visits to Lagrange 

points and near-Earth objects and Mars fly-bys occurring at 

a rate of about one major event per year, and possible rendezvous with Mars’s moons or human lunar return by the 

mid- to late-2020s.

The Committee has found two executable options that comply with the FY 2010 budget profile. However, neither allows for a viable exploration program. In fact, the Committee finds that no plan compatible with the FY 2010 budget 

profile permits human exploration to continue in any meaningful way. 

The Committee further finds that it is possible to conduct a 

viable exploration program with a budget rising to about $3 

billion annually in real purchasing power above the FY 2010 

budget profile. At this budget level, both the Moon First and 

the Flexible Path strategies begin human exploration on a 

reasonable but not aggressive timetable. The Committee believes an exploration program that will be a source of pride 

for the nation requires resources at such a level. 

ORGANIZATIONAL AND PROGRAMMATIC

ISSUES 

How might NASA organize to explore? The NASA Administrator needs to be given the authority to manage NASA’s 

resources, including its workforce and facilities. It is noted 

that even the best-managed human spaceflight programs will 

encounter developmental problems. Such activities must be 

adequately funded, including reserves to account for the unforeseen and unforeseeable. Good management is especially difficult when funds cannot be moved from one human 

spaceflight budget line to another—and where additional 

funds can ordinarily be obtained only after a two-year delay 

(if at all). NASA would become a more effective organization if it were given the flexibility possible under the law to 

establish and manage its programs.

Finally, significant space achievements require continuity of 

support over many years. Program changes should be made 

based on future costs and future benefits and then only for 

compelling reasons. NASA and its human spaceflight program are in need of stability in both resources and direction. 

This report of course offers options that represent changes to 

the present program—along with the pros and cons of those 

possible changes. It is necessarily left to the decision-maker 

to determine whether these changes rise to the threshold of 

“compelling.”

SUMMARY OF PRINCIPAL FINDINGS

The Committee summarizes its principal findings below. 

Additional findings are included in the body of the report.

The right mission and the right size: NASA’s budget 

should match its mission and goals. Further, NASA should 

be given the ability to shape its organization and infrastructure accordingly, while maintaining facilities deemed to be 

of national importance.

International partnerships: The U.S. can lead a bold 

new international effort in the human exploration of space. 

If international partners are actively engaged, including on 

the “critical path” to success, there could be substantial benefits to foreign relations and more overall resources could 

become available to the human spaceflight program. 

Short-term Space Shuttle planning: The remaining 

Shuttle manifest should be flown in a safe and prudent man16 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION
ner without undue schedule pressure. This manifest will 

likely extend operation into the second quarter of FY 2011. 

It is important to budget for this likelihood. 

The human-spaceflight gap: Under current conditions, 

the gap in U.S. ability to launch astronauts into space will 

stretch to at least seven years. The Committee did not identify any credible approach employing new capabilities that 

could shorten the gap to less than six years. The only way to 

significantly close the gap is to extend the life of the Shuttle 

Program.

Extending the International Space Station: The 

return on investment to both the United States and our international partners would be significantly enhanced by an 

extension of the life of the ISS. A decision not to extend its 

operation would significantly impair U.S. ability to develop 

and lead future international spaceflight partnerships. 

Heavy lift: A heavy-lift launch capability to low-Earth orbit, 

combined with the ability to inject heavy payloads away from 

the Earth, is beneficial to exploration. It will also be useful to 

the national security space and scientific communities. The 

Committee reviewed: the Ares family of launchers; Shuttlederived vehicles; and launchers derived from the Evolved Expendable Launch Vehicle family. Each approach has advantages and disadvantages, trading capability, life-cycle costs, 

maturity, operational complexity and the “way of doing business” within the program and NASA. 

Commercial launch of crew to low-Earth orbit: 

Commercial services to deliver crew to low-Earth orbit are 

within reach. While this presents some risk, it could provide 

an earlier capability at lower initial and life-cycle costs than 

government could achieve. A new competition with adequate incentives to perform this service should be open to all 

U.S. aerospace companies. This would allow NASA to focus on more challenging roles, including human exploration 

beyond low-Earth orbit based on the continued development 

of the current or modified Orion spacecraft. 

Technology development for exploration and commercial space: Investment in a well-designed and adequately 

funded space technology program is critical to enable progress in exploration. Exploration strategies can proceed more 

readily and economically if the requisite technology has 

been developed in advance. This investment will also benefit robotic exploration, the U.S. commercial space industry, 

the academic community and other U.S. government users. 

Pathways to Mars: Mars is the ultimate destination for 

human exploration of the inner solar system; but it is not the 

best first destination. Visiting the “Moon First” and following the “Flexible Path” are both viable exploration strategies. The two are not necessarily mutually exclusive; before traveling to Mars, we could extend our presence in free 

space and gain experience working on the lunar surface. 

Options for the human spaceflight program: The 

Committee developed five alternatives for the Human 

Spaceflight Program. It found:

• Human exploration beyond low-Earth orbit is not viable 

under the FY 2010 budget guideline.

• Meaningful human exploration is possible under a lessconstrained budget, increasing annual expenditures by approximately $3 billion in real purchasing power above the 

FY 2010 guidance. 

• Funding at the increased level would allow either an exploration program to explore the Moon First or one that 

follows the Flexible Path. Either could produce significant results in a reasonable timeframe.

17 Review of U.S. Human Spaceflight Plans Committee

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Review of U.S. Human Spaceflight Plans Committee 19

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

The Executive Office of the President established the 

Review of U.S. Human Spaceflight Plans Committee to 

develop options “in support of planning for U.S. human 

spaceflight activities beyond the retirement of the Space 

Shuttle.” The Committee was asked to review the program of record and offer prospective alternatives, not to 

recommend a specific future course for the human spaceflight program. The Committee consisted of 10 individuals 

versed in the history, challenges and existing policies and 

plans for human spaceflight, members representing a broad 

and diverse set of views on spaceflight’s possible future. 

The Committee’s deliberations in its seven public sessions 

were informed by dozens of briefings, several site visits, 

and hundreds of documents received directly or through 

its website.

The current U.S. human spaceflight program appears to be 

on an unsustainable trajectory. It is perpetuating the perilous practice of pursuing goals that are often admirable, but 

which do not match available resources. President Kennedy stated, “We choose to . . . do [these] things, not because they are easy, but because they are hard. . .” And, 

indeed, space operations are among the most complex and 

demanding activities ever undertaken by humans. It really 

is rocket science. Space operations become all the more 

difficult when means do not match aspirations. Such is the 

case today. The human spaceflight program, in the opinion 

of this Committee, is at a tipping point where either additional funds must be provided or the exploration program 

first instituted by President Kennedy must be abandoned at 

least for the time being.

America continues to enjoy a clear global leadership role 

in space capabilities. NASA’s accomplishments are legion. 

Foremost among these is the landing of 12 astronauts on the 

Moon and returning them all safely to Earth. At that time, 

optimism was such that a study chaired by then-Vice President Agnew provided options to place humans on Mars by 

the mid-1980s—less than two decades after the initial lunar 

landing. (See Figure 1-1.)

Introduction

Chapter 1.0

Figure 1-1. The integrated program that never was. The human spaceflight program that was expected to follow the initial Apollo lunar missions. Only a space 

shuttle and space station have been developed so far. Source: NASA
2 0 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

But that was 40 years ago. The last person to stand on the 

Moon returned to Earth 37 years ago. (See Figure 1-2.) Since 

the end of the Apollo Program, no American has traveled 

more than 386 miles from the surface of the Earth. Some 70 

percent of Americans living today had not yet been born at 

the time of Apollo 11.

Today, the nation faces important decisions about the future 

of human spaceflight. Will we again leave the close proximity of low-Earth orbit and explore the solar system, charting 

a path for the eventual expansion of human civilization into 

space? If so, how will we ensure that our exploration delivers the greatest benefit to the nation? Can we explore with 

reasonable assurance of human safety? And can the nation 

marshal the resources to embark on the mission? Although 

there remain significant potential barriers to prolonged deepspace operations, which deserve greater attention than they 

are currently receiving (e.g., adaptation of humans to the micro-gravity and radiation environments of space away from 

the protective features of the Earth), the principal barrier to 

space operations continues to be its high cost compared with 

the resources that have been available.

Space exploration, initially a competitive pursuit, has become a global enterprise. Many other nations have aspirations in space, and the combined annual budgets of their 

space programs are comparable to NASA’s. If the U.S. is 

willing to lead a global program of exploration, sharing both 

the burdens and benefits of space exploration in a meaningful way, significant benefits could follow. Actively engaging 

international partners in a manner adapted to today’s multipolar world could strengthen geopolitical relationships, 

leverage global financial and technological resources, and 

enhance the exploration enterprise.

In addition, there is now a burgeoning commercial space industry. Given the appropriate incentives, this industry might 

help overcome a long-standing problem. The cost of admission to a variety of space activities strongly depends on the 

cost of reaching low-Earth orbit. These costs become even 

greater when, as is the circumstance today, large sums are 

paid to develop new launch systems but those systems are 

used only infrequently. It seems improbable that order-ofmagnitude reductions in launch costs will be realized until 

launch rates increase substantially. But this is a “chickenand-egg” problem. The early airlines faced a similar barrier, which was finally resolved when the federal government awarded a series of guaranteed contracts for carrying 

the mail. A corresponding action may be required if space 

is ever to become broadly accessible. If we craft a space 

architecture to provide opportunities to industry, creating an 

assured initial market, there is the potential—not without 

risk—that the eventual costs to the government could be reduced substantially. 

Significantly, we are more experienced than we were in 1961, 

and we are able to build on that experience as we design an 

exploration program. If, after designing cleverly, building 

alliances with partners, and engaging commercial providers, 

the nation cannot afford to fund the effort to pursue the goals 

it would like to embrace, it should accept the disappointment 

of setting lesser goals. Whatever space program is ultimately selected, it must be matched with the resources needed 

for its execution. Here lies NASA’s greatest peril of the 

past, present, and—absent decisive action—future. These 

challenging initiatives must be adequately funded, including 

reserves to account for the unforeseen and unforeseeable. 

(See Figure 1-3.)

Figure 1-2. Astronaut Gene Cernan as photographed by astronaut Jack 

Schmitt on the sixth and final Apollo exploration of the lunar surface in 1972. 

Source: NASA (Apollo 17)

Notes:

 1. Mercury, Gemini, Apollo, Shuttle, and ISS costs are actual costs derived 

from historical budget documents.

2. Constellation costs are estimates that are supplied by the Constellation 

Program Office and based on an unconstrained budget that cumulates in 

a single Human Lunar return mission in 2020.

Figure 1-3. Human Spaceflight Programs Costs in Real Year and 

Constant Year 2009 Dollars. Source: NASA
Review of U.S. Human Spaceflight Plans Committee 21

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

Can we explore with reasonable assurance of human safety? 

Human space travel has many benefits, but it is an inherently dangerous endeavor. Past gains in launch systems reliability and safety have been realized at a painfully slow 

pace. Predictive models have generally proven unsatisfactory in accurately forecasting absolute reliability—many actual failures have been attributable to causes not included in 

most reliability models (e.g., process errors, design flaws, 

and, less frequently, operational errors). A great deal has 

been learned in building more reliable space systems, and 

this is not to suggest otherwise; rather, it is to confirm that 

this is an area deserving continuing attention. Human safety 

can never be absolutely assured, but throughout this report, 

safety is treated as the sine qua non. Concepts falling short 

in human safety have simply been eliminated from consideration. For example, no options proceeding directly to Mars 

have been offered as alternatives, because the Committee 

believes the state of technology, the understanding of risks, 

and the available operational experience are sufficiently immature—irrespective of the budgetary limitations—to commit to such an endeavor.

How will we explore to deliver the greatest benefit to the 

nation? Planning for a human spaceflight program should 

begin with a choice of goals—rather than a choice of destinations. Destinations should derive from goals, and alternative architectures may be weighed against those goals. 

There is now a strong consensus in the United States that 

the next step in human spaceflight should be to travel beyond low-Earth orbit. This promises to provide important 

benefits to society, including driving technological innovation; developing commercial industries and important 

national capabilities; and contributing to our expertise in 

further exploration. Human exploration can contribute 

appropriately to the expansion of scientific knowledge, 

especially field geology, and it is in the interest of both 

science and human spaceflight that a credible and wellrationalized strategy of coordination between the two endeavors be developed. Robotic spacecraft will play an 

important role as a precursor to human spaceflight activiFigure 1-4. NASA Appropriation History in Real Year and Constant Year 2009 Dollars. Source: OMB Historical Budget Tables

Figure 1-5. As a percent of Gross Domestic Product the NASA budget has 

more or less continuously diminished since the peak of the Apollo program. 

Source: OMB Historical Budget Tables
2 2 Review of U.S. Human Spaceflight Plans Committee

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ties. The Committee concluded that the ultimate goal of 

human exploration is to chart a path for human expansion 

into the solar system. This is an ambitious goal, but one 

worthy of U.S. leadership in concert with a broad range 

of international partners. 

With regard to the human spaceflight program itself, the 

Committee has been deluged with strongly and genuinely 

held, frequently conflicting, beliefs as to the program’s 

proper composition. For example, the following statements 

appeared in six different communications that happened to 

come across the Committee Chairman’s desk within minutes 

of each other: 

• “As an American, having NASA field a 

retro-reenactment of the Apollo program 

to get back to the moon a half-century after we sent people there the first time is 

humiliating.”

 

• “From a safety and continuity standpoint 

the next step in space must be a return to 

the moon.”

• “I am an aerospace engineering master’s 

candidate. [My classmates’] options are 

working for monolithic bureaucracies 

where their creativity will be crushed by 

program cancellations, cost overruns and 

risk aversion... It is no surprise that many 

of them choose to work in finance...”

 

• “We remember the past well and remind 

ourselves often of long gone civilizations 

whose innovations in science, technology and learning yielded knowledge that 

served as beacons of brilliance, but who 

lost the spark and faded.”

 

• “...going back to the moon takes us into an intellectual and political cul de sac...”

• “The audacity to go to the moon was perhaps 

the 20th century’s greatest illustration of America’s optimism. Present generations of Americans 

need to capture some of that audacity.” 

A primary issue in formulating a human spaceflight 

plan is its affordability. In the way of background, Figures 1-4, 1-5 and 1-6 present the overall NASA budget trend over time in absolute terms and in relationship to the GDP and the federal budget, respectively. 

The trend in funding the human spaceflight portion of 

NASA’s portfolio is shown in Figure 1-7. Today, the 

human spaceflight program costs each citizen about 

seven cents a day. 

So what should America’s human spaceflight program 

look like? Before answering that question, we must 

face an underlying reality. We are where we are. The 

Committee thus identified five questions that could 

form the basis of a plan for U.S. human spaceflight:

• What should be the future of the Space Shuttle?

• What should be the future of the International Space Station?

• On what should the next heavy-lift launch vehicle be 

based?

• How should crew be carried to low-Earth orbit? 

• What is the most practicable strategy for exploration beyond low-Earth orbit?

Figure 1-7. Human spaceflight yearly annual budget in FY 2009 dollars (left scale) and as a percentage 

of total NASA budget (right scale.) Source: NASA

Figure 1-6. The overall NASA budget as a fraction of the federal budget has declined from 

4.5 percent at the peak of the Apollo program to approximately 0.5 percent today. Source: 

OMB Historical Budget Tables
Review of U.S. Human Spaceflight Plans Committee 2 3

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

The Committee considers the framing of these questions, in 

a consistent way, to be at least as important as their combinations in the integrated options for a human spaceflight 

plan. The Committee assessed the programs within the current human spaceflight portfolio, considered capabilities and 

technologies that a future program might require, and examined the roles of commercial industry and our international 

partners in this enterprise. 

A human landing and extended human presence on Mars 

stand prominently above all other opportunities for exploration. (See Figure 1-8.) Mars is unquestionably the 

most scientifically interesting destination in the inner solar system. It possesses resources which can be used for 

life support and propellants. If humans are ever to live 

for long periods with intention of extended settlement on 

another planetary surface, it is likely to be on Mars. But 

Mars is not an easy place to visit with existing technology 

and without a substantial investment in resources. The 

Committee concluded that Mars is the ultimate destination for human exploration of the inner solar system; but 

as already noted, it is not the best first destination. 

The Committee thus addressed several possible strategies for exploration beyond low-Earth orbit. We could 

choose to explore the Moon first, with lunar surface 

exploration focused on developing the capability to 

explore Mars. Or we could choose to follow a flexible path to successively distant or challenging destinations, such as lunar orbit, Lagrange points, near-Earth 

objects, or the moons of Mars, which could lead to the 

possible exploration of the lunar surface and/or Martian surface. 

As a result of its deliberations, the Committee developed 

five integrated options for the U.S. human spaceflight program that the Committee deems representative: one baseline case, founded upon the Constellation program, and 

four alternatives. Two of the options are constrained to 

the FY 2010 budget profile. The remaining three options, 

including the baseline, fit a less-constrained budget. It 

was possible to define some 3,000 potential options from 

the set of parameters considered—hence the options presented here should be thought of as representative families. Various program additions and deletions among 

these families are also plausible, with appropriate budget 

adjustments—including a proper accounting of the many 

interdependent facets of these integrated options. Several 

of these derivatives are discussed in this report.

The Committee considers it important for any exploration strategy to offer a spectrum of choices that provides periodic milestone accomplishments as well as a 

continuum of investment cost options. Unfortunately, 

for all options examined, the “entry cost” for human 

exploration is indeed significant—and for the more inspiring options there does not seem to be a “cost continuum.” Put another way, there is a sizeable difference in the cost of programs between those operating in 

low-Earth orbit and those exploring beyond low-Earth 

orbit.

Clearly, a more penetrating analysis into any choice 

will be required before fully embarking upon it. However, the Committee believes it has fairly represented 

the most plausible courses. It bases this assessment 

in part on the extraordinary supporting effort provided by NASA personnel—an effort that was forthright, 

competent, and, in the NASA spirit, “can-do.” The 

Committee also benefited significantly from prior independent reviews of NASA activities. In addition, the 

Committee contracted with the Aerospace Corporation 

to provide independent assessments. During the Committee’s deliberations, it was informed by day-long 

public meetings in Houston, TX, Huntsville, AL, and 

Cocoa Beach, FL, as well as five days of meetings in 

Washington, DC. In addition, its subcommittees held 

Figure 1-8. Artist’s concept of Mars mission activity. Source: NASA
2 4 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

meetings in Denver, CO; Decatur, AL; Huntsville, AL; 

Michoud, LA; Hawthorne, CA; El Segundo, CA; and 

Dulles, VA. The group conducted numerous teleconference and videoconference preparatory sessions and 

communicated frequently by e-mail (over 1,700 e-mails 

in the Chairman’s case). 

Seeking to benefit from the views of the public, the Committee: established a website and Facebook site; used 

Twitter; conducted all decisional meetings in public session (meetings that were also carried on NASA TV); provided opportunity for public comment at five of the formal 

meetings; testified before committees of both the House 

and Senate; and held seven press conferences. Participation by the public was extensive—and the Committee 

made use of that input. It is heartening to note that the 

public still strongly supports the overall efforts of NASA. 

(See Figure 1-9.)

Finally, it is reasonable to ask whether a review over 

several months is sufficient to offer the options presented here. Certainly, the issues at hand demand a broad 

and detailed understanding of the human spaceflight 

program—ranging from an awareness of the impact of 

galactic cosmic rays on the human body to the fact that 

the hook-height at NASA’s Michoud Assembly Facility 

will only allow the manufacture of a stage with a diameter of 33 feet.

Each of the Committee members had accrued extensive 

experience with spaceflight issues long before the beginning of this review. For example, the members cumulatively have amassed 245 days in orbit, 6 flights into 

space, 293 years working on space matters, 175 years in 

science, 144 years in engineering, 143 years in engineering management, 61 years in space operations, 77 years 

in government, 35 years in the military, and 160 years in 

the private sector. (The totals reflect the overlap of some 

of these categories.) 

The Committee believes that the options presented here, 

if matched with appropriate funds, provide a reasonable 

foundation for selecting a human spaceflight program 

worthy of a great nation.

Figure 1-9. Space exploration (human/robotic) continues to be valued by Americans – 77% think it is very or somewhat important, while 58% think it extremely 

or somewhat relevant. Source: NASA - 2009 Market Research Insights and Implications - August 6, 2009
Review of U.S. Human Spaceflight Plans Committee 2 5

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In human spaceflight, as in other endeavors, 

a review of the past can help provide perspective in planning for the future. This 

chapter, noting the findings of some earlier space-program assessments, seeks to 

provide such perspective.

In 1961, President John F. Kennedy forcefully and publicly focused the nation’s nascent space program on a single goal: U.S. 

astronauts would set foot on the surface 

of the Moon before the end of the decade, 

and return safely. More feasible than a 

mission to Mars, and with better prospect 

of preceding the Soviets than seeking to 

develop an orbiting space station, the lunar landing would ensure U.S. standing 

as the leader in the world’s most prominent exploration competition. Kennedy’s 

challenge to NASA and the nation was an 

audacious one, given that at the time he 

made it in 1961, no American had even 

reached Earth orbit. 

President Kennedy markedly accelerated 

the U.S. space program, but he did not initiate it. NASA was established in 1958. President Dwight 

Eisenhower supported human missions to low-Earth orbit 

and beyond, but he emphasized fiscal restraint in the effort. According to George Low, at the time NASA Chief 

of Manned Spaceflight, a desirable lunar program should 

have project costs kept in balance with expected returns 

and within the foreseeable NASA budget. By the 1960s, 

the drive to meet the end-of-decade goal superseded those 

restraints. 

The outcome of the so-called Space Race was not a foregone conclusion. Among numerous Soviet achievements, 

it was a cosmonaut who was the first human to orbit the 

Earth, and another to first conduct extra-vehicular activity. The U.S. Mercury and Gemini programs achieved 

their objectives of developing and flight-testing the kinds 

of equipment and procedures that would be needed in a 

lunar mission. But in 1967, with less than three years remaining before the deadline set by President Kennedy, fire 

broke out in the pure-oxygen environment of the Apollo 

1 command module during a ground test, resulting in the 

death of the three astronauts on board. Despite the delay from the accident and its aftermath, on July 20, 1969, 

Neil Armstrong and Buzz Aldrin of Apollo 11 became the 

first humans to set foot on a celestial body beyond our 

own, while Mike Collins orbited above, preparing for the 

return to Earth. Ten more astronauts, on five more Apollo 

missions, would reach the lunar surface. 

U.S. Human Spaceflight:

Historical Review

Chapter 2.0

Figure 2-1. Front page of The New York Times from October 5, 1957 and July 21, 1969. 

Source: The New York Times
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Big goals are energizing, for individuals and for national efforts. (See Figure 2-1) But the problem with focusing on a 

single all-consuming objective is the letdown that can ensue 

after the objective is achieved. Public interest appeared to 

wane during the course of succeeding lunar missions. NASA 

had ambitious set of plans to follow Apollo. Space stations 

would orbit the Earth. A more permanent lunar presence 

would be established by 1982. Proposed hardware included 

a space tug and a nuclear-powered shuttle. The first crewed 

landing on Mars would take place by the mid-1980s. By 

1990, there would be 100 humans in low-Earth orbit, 48 on 

the Moon and 72 on Mars and its moons. Most of that never 

came to pass. Since 1972, the year of the last Apollo lunar 

mission, no human has ventured farther from the Earth’s surface than 386 miles.

President Richard Nixon did not end the space program, but 

he did much to scale it back. The trajectory of the NASA 

budget shifted downward. The Nixon administration was 

responding not only to the perceived decline in public support for far-reaching human space exploration, but also to the 

economic decline at the time. When a task group established 

by the administration presented options that included a lunar 

return and a program aimed at Mars, the President confined 

the nation’s crew-carrying space ventures instead to lowEarth orbit. 

The keystone of the redefined initiative was the Space Shuttle, the reusable departure from the expendable transport systems used until that time, capable of launching as a rocket 

and landing as an aircraft. The economic case for the Shuttle 

was that it would provide dependable, high-frequency access 

to orbit, with relatively low cost. Government payloads, both 

civil and military, would be delivered aboard the orbiter, as 

well as commercial satellites. On some missions, the vehicle 

would serve as an orbiting laboratory. Despite its unprecedented technical complexity, the Shuttle’s development 

budget was constrained, eliminating design options such as 

a fully reusable, two-stage configuration.

The first Space Shuttle reached orbit in April 1981, a little 

less than a decade after President Nixon announced the program in 1972. Launch frequency never approached original 

expectations, and the cost per mission turned out to be far 

greater than what was forecast. The plan to launch on nearly 

a weekly basis was cut to 24 flights per year, and even that 

proved unattainable. By January of 1986, five orbiters had 

flown four test flights and 20 operational missions. 

On the morning of January 28, 1986, Space Shuttle Challenger was destroyed in an explosion 73 seconds after launch. 

The accident claimed the lives of all seven crew members. 

The Presidential Commission that investigated the accident, 

chaired by William Rogers, called for measures to correct 

critical design flaws in the Shuttle, as well as to correct management shortcomings it identified at NASA. The Commission advocated reasonable expectations for the Shuttle Program, urging that the space agency “establish a flight rate that 

is consistent with its resources.” 

After the Shuttle had been flying a variety of missions for a 

number of years, its primary purpose evolved to constructing 

and supporting space stations. Both the U.S. and the Soviet 

Union began operating orbiting platforms for research and 

other functions in the early 1970s. In his 1984 State of the 

Union Address, President Ronald Reagan announced plans 

to construct what became known as Space Station Freedom. 

James Beggs, NASA Administrator at the time, called this 

permanent orbiting facility “the next logical step” in space 

exploration. For President Reagan, the international project 

served as an element of foreign policy, helping to reinforce 

ties with allied nations. Later, after the end of the Soviet 

Union but before any joint space station was built, the station concept was promoted as a means to help foster cooperation with a former adversary.

In fact, Freedom was never built. The decade following the 

Reagan announcement saw a long series of design studies, 

redesigns and cost reassessments. Eventually, the original 

initiative, which included the U.S., Europe, Japan, and Canada, was expanded by joining forces with Russia to build the 

International Space Station. Before construction began on 

the International Space Station, the U.S. was building experience with the Russians, flying Shuttle missions to the Mir 

space station and flying NASA astronauts on Soyuz vehicles 

to long-duration Mir missions.

What tasks should a space station perform? Long-term, what 

should the United States be seeking to accomplish in space? 

In 1985, the sense in Congress was that it was not getting 

an adequate response from NASA and the White House, so, 

through legislation, it directed the establishment of an independent commission to examine these questions. Former 

NASA Administrator Thomas Paine chaired the National 

Commission on Space, which developed a half-century 

roadmap for the U.S. civil space program. Among numerous recommendations, the Commission counseled against 

focusing efforts on a single objective, on the Apollo model, 

with nothing to follow. It stressed program continuity, so 

there would not be another gap like the one between the end 

of Apollo and the beginning of the Shuttle. And it departed 

from the policy that had prevailed over the previous decade, 

limiting operational focus to low-Earth orbit. Humans were 

to return to the Moon by 2005 and reach Mars by 2015. The 

impact of the Paine Commission Report was diminished by 

timing: The Challenger accident occurred during the course 

of the Commission’s inquiry. 

In 1989, on the 20th anniversary of the Apollo 11 Moon 

landing, President George H. W. Bush announced the Space 

Exploration Initiative, which supported a number of the 

objectives spelled out in the earlier Paine Report, such as 

missions to the Moon and Mars. In the same speech, the 

President asked Vice President Dan Quayle to lead a National Space Council, which would determine the requirements to fulfill the Initiative. NASA Administrator Richard 

Truly, in turn, established a task force to support that inquiry. 

Among the findings of this “90-Day Study,” the projected 

total cost of the proposed lunar and Mars projects, over 34 

years, would be an estimated $541 billion (in 1991 dollars). 

In 1990, Congress zeroed the budget of the Space Exploration Initiative.
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President Bush, Vice President Quayle and the Space Council called for a fresh assessment of the long-term prospects of 

NASA and the U.S. civil space program. To provide that assessment, an advisory committee was established, chaired by 

Norman R. Augustine, which raised numerous issues, starting with the lack of a national consensus on space program 

goals. Within NASA, the committee found an overextended 

agency, with shortcomings in budget, project development, 

personnel practices and other areas of management, and the 

committee cited the need for a heavy-lift launch vehicle and 

a space program balanced between human and robotic flight. 

The committee said the U.S. civil space program is “overly 

dependent upon the Space Shuttle for access to space.” The 

committee also stated that “the statistical evidence indicates 

that we are likely to lose another Space Shuttle in the next 

several years.” Among its prescriptions for improvement, 

the committee presented a new approach for long-range 

planning of space-exploration projects, in which programs 

would be “tailored to respond to the availability of funding, 

rather than adhering to a rigid schedule” that failed to recognize the impact of funding changes.

Twelve years later, on February 1, 2003, the nation did lose 

another Shuttle. Columbia, the first orbiter to reach space 

22 years earlier, was destroyed during reentry, with the loss 

of all seven members of its crew. The Columbia Accident 

Investigation Board documented the physical cause of the 

accident, but also cited organizational and communications 

failures within NASA that allowed the critical damage to occur and go unaddressed. The report went on to cite “a lack, 

over the past three decades, of any national mandate providing NASA a compelling mission requiring human presence 

in space . . .” 

Throughout NASA’s history, while human spaceflight efforts garnered the most national attention, the agency continued to launch satellites, deep-space probes and rovers of 

ever-greater sophistication. The success of robotic missions 

such as the Voyager spacecraft to the outer planets fostered 

debate over the relative value of robotic versus human space 

exploration. In 1999, NASA Administrator Dan Goldin 

chartered a small internal task force—the Decadal Planning 

Team, which later evolved into a larger, agency-wide team 

known as the NASA Exploration Team—to investigate the 

best ways to coordinate human and robotic missions. These 

teams followed a series of architecture studies over the previous decade, such as the report of General Thomas Stafford 

and the Synthesis Group, all aimed at charting a renewed 

course of space exploration. 

The work of the two NASA teams helped provide the basis 

for a new policy established by President George W. Bush 

in 2004, the Vision for Space Exploration. In announcing 

the Vision, the President acknowledged the numerous tangible benefits of space missions, in areas such as communications and weather forecasting, but the central purpose 

he stressed—as reflected in the name of the policy—was 

exploration, continuing the American tradition of discovery 

in uncharted territory. The new initiative echoed the earlier 

Eisenhower policy: fly well beyond Earth’s realm, but do it 

on a fiscally sustainable basis.

Leading the agenda set out in the Vision was completion 

of the ISS by 2010. One reason cited was to meet the nation’s obligations to its international partners; another was 

to investigate the effects on human biology of extended exposure to the space environment, thereby helping to develop 

the means to sustain astronauts on subsequent, long-duration 

missions. At least initially, the Vision did not stress the role 

of the ISS as a laboratory for other kinds of research. Completion of the ISS depended on returning the Space Shuttle 

to flight once safety concerns raised in the Columbia accident investigation were sufficiently addressed. Exploration 

beyond low-Earth orbit, under the Vision plan, was focused 

on the Moon—starting with robotic missions no later than 

2008, followed by human return to the lunar surface by 

2020. Once a human presence is well established on the 

Moon, the President said, “we will then be ready to take the 

next steps of space exploration: human missions to Mars and 

to worlds beyond.”

At the time he announced the Vision, President Bush also 

appointed a commission, chaired by E. C. “Pete” Aldridge, 

Jr., to develop recommendations for implementing the plan. 

Among its recommendations, the commission said that 

NASA should “aggressively use its contractual authority 

to reach broadly into the commercial and nonprofit communities to bring the best ideas, technologies, and management tools into the accomplishment of exploration goals.” 

Through its Commercial Orbital Transportation Services 

(COTS) program, NASA solicited proposals for private-sector transport of cargo and possibly crew to the International 

Space Station. Three awards were made, one of which was 

subsequently cancelled by NASA for failure to meet milestones.

In announcing the Vision, President Bush noted that “America has not developed a new vehicle to advance human exploration in space in nearly a quarter century.” Proposals for 

a next-generation space vehicle had long been considered, 

but with the loss of Columbia, and with a mandate from the 

new Presidential policy to focus on the completion of the 

ISS, and then retire the Space Shuttle, NASA affirmatively 

began preparing for near-term retirement of the Shuttle. A 

newly constituted Exploration Systems Mission Directorate 

led the task of developing the Shuttle’s successor. Initially, 

NASA chose a broad concept-maturation, risk reduction, 

and technology-investment approach to developing exploration systems. 

In 2005, after Dr. Michael Griffin became Administrator, 

NASA undertook the Exploration Systems Architecture 

Study (ESAS) to select vehicles and systems in keeping 

with the Vision. The team evaluated hundreds of potential 

configurations. A leading objective was to minimize the gap 

between the last Shuttle flight and the first flight of the new 

vehicle. A date of 2012 was set for that first flight. Another criterion, spelled out in the 2005 Authorization Act for 

NASA, was to make use, as much as possible, of assets and 

infrastructure carried over from the Shuttle Program. Since 

the new system—actually a family of vehicles—would 

likely have a decades-long service life, it was to have the 

capability of not only reaching low-Earth orbit, but also extending to the Moon and beyond. The lunar objective would 
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be to do more than replicate what Apollo had accomplished 

long before. The architecture would support larger crews 

and longer missions, capable of reaching any location on 

the Moon and returning. The results of the vehicle-system 

selection process evolved into what is now known as the 

Constellation Program, consisting of Ares launch vehicles, 

Orion crew capsule, the Altair lunar lander, and lunar surface systems. 

Today, budget questions continue to dominate the human 

spaceflight debate. In the 37 years since humans last ventured beyond low-Earth orbit, and five years after announcement of the Vision for Space Exploration, consensus is still 

lacking about what is feasible and affordable in the future 

course of U.S. human spaceflight.
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n 3.1 GOALS FOR EXPLORATION

We explore to reach goals, not destinations. It is in the 

definition of our goals that decision-making for human 

spaceflight should begin. With goals established, questions about destinations, exploration strategies and transportation architectures can follow in a logical order. 

While there are certainly some aspects of the transportation system that are common to all exploration missions 

(e.g. crew access and heavy lift to low-Earth orbit), there 

is a danger of choosing destinations and architectures 

first. This runs the risk of getting stuck at a destination without a clear understanding of why it was chosen, 

which in turn can lead to uncertainty about when it is 

time to move on. 

Since 1972, the destination for U.S. human exploration 

of space has been confined to low-Earth orbit. Following the loss of Columbia, a strong national consensus 

emerged that we should move beyond low-Earth orbit 

once again, and explore the inner solar system. The 

question arises, “What is the point of doing so?” The 

answers to this question help to identify the goals of human spaceflight. While it was not specifically within 

the Statement of Task of the Committee to advise on the 

rationale for a human spaceflight program, the Committee felt compelled to at least review the likely goals as a 

foundation for its further deliberations.

Human spaceflight produces important tangible benefits 

to society. Human spaceflight is a technologically intensive activity, and during its execution new technologies 

are derived that have benefit to other government and 

commercial users of space, and to products that touch 

Americans daily. Access to and development of space 

is critical to our national welfare, and a well-crafted human exploration program can help to develop competitive commercial industries and important national capabilities. We explore our first destinations in part to learn 

how better to explore more challenging sites in the future. Human and robotic explorations both contribute to 

the expansion of scientific knowledge. Human explorers 

are most effective when exploring complex destinations, 

and particularly in endeavors such as field geology.

Human exploration also addresses larger goals. We live 

in an increasingly multi-polar world, and human space exploration is one domain in which the United States is still 

the acknowledged leader. Human exploration provides an 

opportunity to demonstrate space leadership while deeply 

engaging international partners. Chapter 8 will discuss the 

potential of partnerships in exploration.

Human exploration of space can engage the public in new 

ways, inspiring the next generation of scientists and engineers, and contributing to the development of the future 

workforce in science, technology, engineering and mathematics (STEM). By viewing other planets as well as our 

own from deep space, exploration helps to shape human perceptions of our place in the universe. 

There was a strong consensus within the Committee that 

human exploration also should advance us as a civilization 

towards our ultimate goal: charting a path for human expansion into the solar system. It is too early to know how and 

when humans will first learn to live on another planet, but 

we should be guided by that long-term goal. 

In developing alternatives for human spaceflight plans, the 

Committee was guided by these tangible, less-tangible and 

long-term goals. In Chapter 6, the Committee returns to 

these goals as the basis for developing evaluation measures 

against which the options will be evaluated.

n 3.2 OVERVIEW OF DESTINATIONS AND 

APPROACH

The Moon has been the nation’s principal focus of human 

space exploration beyond low-Earth orbit since President 

Kennedy set it as a national goal in 1961. But there are 

Goals and Future Destinations

for Exploration

Chapter 3.0
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many places humans could explore in the inner solar system, 

each with benefit to the public, as well as opportunities for 

scientific discoveries, technology development and steady 

progress in human exploration capabilities. Among these 

destinations are our own Moon, as well as Mars and its 

moons. (See Figure 3.2-1.) Other potential destinations 

include the near-Earth objects, asteroids and spent comets that pass near the Earth. There are also important locations in free space that are of interest, including the 

Earth’s Lagrange points. These are sites at the edge of the 

Earth’s influence, which will be important future points 

for observation toward the Earth and away from it. For 

example, the James Webb Space Telescope, the successor to the Hubble Space Telescope, will be placed at a 

Lagrange point. The Lagrange points might also be the 

nodes of a future space transportation highway through 

the inner solar system.

There is a progression in time and difficulty in reaching these destinations. 

Lunar orbit, the Lagrange points, 

near-Earth objects, and a Mars fly-by 

are the easiest in terms of energy required. It actually requires less energy to fly by Mars than to land on and 

return from the surface of the Moon. 

Next in terms of energy requirements 

is the lunar surface, followed by Mars 

orbit. The surface of Mars requires 

the most energy to reach. An analysis 

of the duration to reach these destinations yields a slightly different order. 

The Moon is days away, the Lagrange 

points weeks, the near-Earth objects 

months, a Mars fly-by a year, and a 

Mars landing is the longest—about 

900 days for a round trip using the most 

likely approach. Among practical criteria 

to apply in selecting destinations are questions such as: How difficult is the destination to reach? How long will it take? How 

dangerous will the mission be? How expensive and sustainable will it be? 

The key framing question for this chapter is: 

What is the most practicable strategy for exploration beyond low-Earth orbit? Options 

include:

• Mars First, with a Mars landing after 

a brief test flight program of equipment 

and procedures on the Moon.

• Moon First, with surface exploration 

focused on developing capability for 

Mars. 

• Flexible Path to Mars via the inner solar 

system objects and locations, with no 

immediate plan for surface exploration, 

then followed by exploration of the lunar and/or Martian surface. 

In assessing these choices, the Committee examined a number of scenarios, performing new analyse and reviewing 

existing studies from the Constellation Program and other 

NASA architecture studies dating back to Apollo. The Committee listened carefully to alternate views presented by a 

number of other organizations, including the Mars Society 

and the Planetary Society. 

With the help of a NASA team, the Committee examined the 

technical, programmatic and goal-fulfillment aspects of the 

destinations in two major cycles. The first cycle considered 

six destination/pathway scenarios, including three variants 

of lunar exploration, two variants of Mars exploration, and 

the “Flexible Path.” (One scenario was the baseline ConFigure 3.2-1. Potential destinations for the U.S. human spaceflight program. Source: Review of U.S. 

Human Spaceflight Plans Committee

Figure 3.3.1-1. Comparison of major features of the Earth and Mars. Source: Review of U.S. Human 

Spaceflight Plans Committee
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stellation Program approach.) For each of these six variants, 

benefits and timelines were developed, along with the necessary hardware elements and approximate costs. A second 

cycle included more detailed analysis, such as coupling to 

launch vehicles and upper stages, and more detailed benefit 

and cost analysis. In the end, the six initial scenarios collapsed into the three destination options described below. 

Later, Chapter 6 provides a more complete description of 

each scenario, combining in each case the choice of destination with the choice of launch system to low-Earth orbit.

n 3.3 MARS FIRST

3.3.1 Overview. A human landing 

that leads to an extended human presence 

on the Martian surface stands prominently 

above all other opportunities for human 

space exploration. Mars is somewhat 

smaller than Earth, has about three-eights 

its surface gravity, a thin atmosphere consisting mostly of carbon dioxide, and water. (See Figure 3.3.1-1.) It therefore possesses potential resources that can be used 

for life support and propellent. If humans 

are ever to live for long durations on another planetary surface and move toward 

permanent expansion of human civilization beyond the Earth, it is likely to be on 

Mars (Figure 3.3.1-2.) Mars is unquestionably the most scientifically interesting destination in the inner solar system. 

Mars has a planetary history similar to that 

of the Earth. It had a period of volcanic 

activity. At one time, water ran freely on its surface. Its 

atmosphere evolved over time, much as ours did. And there 

is the distinct potential that life could have begun to evolve 

on Mars. Learning about Mars would teach us a great deal 

about the Earth. Furthermore, the scientific community that 

studies Mars generally agrees that its exploration could be 

significantly enhanced by direct participation of astronaut 

explorers. The Committee finds that Mars is the ultimate 

destination for human exploration of the inner solar system.

3.3.2 Scenario Descriptions. Two scenarios have been 

developed to examine the human exploration of Mars. In the 

first, the surface of Mars would be the initial and only destination, and all resources would be focused on reaching it as 

soon as possible. In the second, systems would be designed 

for Mars missions, but would be first verified on several test 

flights to the Moon. The latter would require some hardware 

modification, but would test the systems at a planetary body 

near the Earth before committing to a multi-year mission to 

Mars. In the end, the Committee decided to use the variant 

with a brief test flight program of equipment and procedures 

on the Moon as the reference Mars First option.

The Mars First scenario represents a comprehensive human exploration strategy, and requires a focused technology 

development program as well as an integrated test plan to 

reduce risk while gaining confidence and experience with 

the Mars exploration systems. Exploration of Mars would 

be performed in extended stays on the surface, with each 

mission going to a different landing site on Mars. Human 

exploration would be complemented by robotic exploration 

of Mars. Synergies would be exploited, but would not fundamentally drive the program.

This scenario was analyzed based on the existing 2007 NASA 

Human Exploration of Mars Design Reference Architecture 

5.0 (NASA-SP-2009-566 and NASA-SP-2009-566-ADD). 

This architecture is shown in Figure 3.3.2-1. It assumed the 

Figure 3.3.1-2. Mars – A possible first destination for exploration. 

Source: NASA Hubble Space Telescope

Figure 3.3.2-1. Architecture of the Mars First strategy, indicating the three missions launched toward 

Mars necessary to support the landing of a crew of six astronauts. Source: NASA
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use of eight or more Ares V launchers plus an Ares I crew 

launch for each Mars opportunity. Both nuclear thermal rockets and chemical (LOX/LH2) in-space propulsion systems 

were examined. Under this scenario, 26 months before the 

launch of the crew, a mission is launched carrying the ascent 

vehicle to the Martian surface, and a second mission injects 

a crew descent and habitation vehicle into Mars orbit. The 

crew then makes a faster trip, and reaches rendezvous in Mars 

orbit with the descent vehicle, lands on the surface of Mars, 

spends 540 days on the surface, and then returns to Mars orbit 

in the ascent vehicle. There the crew rendezvouses with the 

crew vehicle and returns home to Earth. On both the trip to 

and from Mars, the crew is exposed for 180 to 200 days to the 

weightlessness and full solar and galactic cosmic radiation of 

free space (i.e., away from any planet). The total round trip to 

Mars and back lasts about 900 days.

The Moon would be used as a site for integrated testing of the Mars systems. The systems landed on the Moon—landers, habitat, 

rovers and other surface systems—would be 

those designed for the Mars missions, or as 

similar as possible while suitable for the lunar surface, as shown in Figure 3.3.2-2. Not 

all systems necessary for Mars can be tested 

on the Moon (e.g., entry systems and in-situ 

atmospheric resource utilization). However, 

most of the Mars systems can be tested on 

the Moon, making the Moon not only a conceptual testbed, but also an actual testbed for 

Mars systems.

3.3.3 Milestones, Destinations and 

Capabilities. A notional development 

plan and flight road map for the Mars First 

scenario is presented in Figure 3.3.3-1. The 

strategy shows the progressive expansion 

and extension of human capabilities, starting 

with a demonstration of an extended-duration habitat at the ISS, expanding to unpiloted 

missions to near-Earth objects to demonstrate 

the performance of heavy lift and in-space transportation systems. At the same time, sub-scale 

robotic missions at Mars would demonstrate key 

Mars exploration technologies needed to land 

large payloads at a precise location. The lunar 

dress rehearsal would take place as the Mars 

hardware is completed and prepared for integrated systems testing. The transportation system, 

cargo and crew would be launched toward the 

Moon over a 10-month period. Once the crew 

and cargo are in place on the surface, operations 

will take place over a two-year period, with crew 

rotation occurring every six months. While going to the Moon would primarily be for the purpose of testing Mars systems, astronauts would 

explore the lunar surface as well. When all systems have been tested, cargo-only and then piloted missions to Mars would occur on successive 

opportunities, about 27 months apart.

3.3.4 Assessment. While Mars is the 

ultimate destination for the near-term human 

exploration of space, it is not an easy place to visit with existing technology and experience. No human has ever traveled 

more than three days from Earth, and none beyond 386 miles 

away for almost 40 years. No American has been in space 

much more than 180 days at a time, or exposed to the full radiation of free space for more than about a week. Mars requires 

a trip in space of almost 900 days. We do not have flight-demonstrated technology to confidently approach and land large 

spacecraft on the Mars surface. Mars is distant enough from 

the Sun that it is a weak energy source, and space-based surface nuclear power is probably needed. Under current plans, 

as many as 12 Ares V vehicles would be needed to launch 

each biannual set of missions. It seems likely that some form 

of advanced propulsion may also be needed to make travel 

Figure 3.3.3-1. Timeline of milestones, destinations and capabilities of the Mars First strategy. 

Source: NASA

Figure 3.3.2-2. Architecture of the Mars First system being tested on the Moon. Source: NASA
Review of U.S. Human Spaceflight Plans Committee 3 7

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

feasible. A focused technology program almost a decade long 

would be required before system design could begin.

The preliminary estimates of the cost of Mars missions are far 

higher than for other scenarios, all in an era when budgets are becoming highly constrained. If astronauts were to travel to Mars 

under these circumstances, it would require most of the human 

spaceflight budget for nearly two decades or more, and produce 

few intermediate results. When we finally reached Mars, we 

might be hard pressed to maintain the financial resources needed 

for repeated missions after the first landings, 

recreating the pattern of Apollo. For these 

reasons, the Committee found that Mars is 

the ultimate destination for human exploration of the inner solar system, but is not a 

viable first destination beyond low-Earth 

orbit.

FINDINGS ON HUMAN 

MISSIONS TO MARS

Mars as the Ultimate Destina- tion: Mars is the ultimate destination 

for human exploration of the inner solar system. It is the planet most similar 

to Earth, and the one on which permanent extension of human civilization, 

aided by significant in-situ resources, 

is most feasible. Its planetary history 

is close enough to that of the Earth to 

be of enormous scientific value, and 

the exploration of Mars could be significantly enhanced by direct participation of human explorers.

Mars as the First Destination (“Mars First”):

Mars is not a viable first destination beyond low-Earth orbit at this time. With existing technology and even a substantially increased budget, the attainment of even symbolic missions would demand decades of investment and 

carry considerable safety risk to humans. It is important 

to develop better technology and gain more experience in 

both free space and surface exploration prior to committing to a specific plan for human exploration of the surface 

of Mars.

n 3.4 MOON FIRST 

3.4.1 Overview. If Mars is not the first destination beyond low-Earth orbit, the Moon is an obvious alternative. 

(See Figure 3.4.1-1.) Going there would enable the development of the operational skills and technology for landing on, 

launching from and working on a planetary surface, as well 

as providing a basis for understanding human adaptation to 

another planet that would one day allow us to go to Mars. 

Systems would be designed for the Moon, but would be as extensible as practicable for use on Mars. At a minimum, they 

would demonstrate technologies and operational concepts 

that would be incorporated into eventual Mars systems.

There are potential resources on the Moon that one day could 

be launched from the Moon to fuel depots at the Earth–Moon 

Lagrange points, which could then be used by exploration 

missions beyond the Earth-Moon system. The scientific 

exploration of the Moon is not, in and of itself, a rationale 

for human exploration, but our scientific knowledge of the 

Moon is incomplete. Our previous missions to the Moon, 

both human and robotic, encompassed a geographically limited number of sites for a limited time, with little surface 

range. Much remains to be learned. 

Figure 3.4.1-1. The Earth’s Moon-- the initial destination of the Moon First 

Strategy. Source: NASA

Figure 3.4.2-1. The architecture of the Moon First scenario, using Ares I and Ares V launchers. Source: 

NASA
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3.4.2 Scenario Description. In exploring the Moon, 

there are two main strategies. Both begin with a handful of 

approximately week-long sorties to various sites to scout, 

explore regions of different geography, and validate the 

lunar landing and ascent systems. The Lunar Base strategy would begin with the building of a base, probably at 

the lunar south pole, where the Sun is visible much of the 

time (as it is at the Earth’s south pole in the austral summer). 

Over many missions, a small colony of habitats would be 

assembled, much like the base at the South Pole of the Earth, 

and explorers would begin to live there for up to 180 days. 

Larger rovers would begin to explore hundreds of miles 

from the base. Activities would include science exploration 

and prospecting for resources of hydrogen-rich deposits that 

could be used as fuel. 

Exploring with a few short-duration sorties of just hundreds of miles from the base would actually only allow 

exploration of a very small fraction of the surface of the 

Moon in any depth. The alternate strategy for the Moon 

is to continue a series of increasingly longer sorties to different sites, spending weeks and then months at each one. 

The primary feature of this Lunar Global exploration strategy is that surface operations are flexible and adaptable, 

so that as discoveries on the lunar surface are made, future 

missions can be planned that adjust stay times (from 14 to 

180 days) and mobility range capabilities in response to 

those discoveries. There is even the potential that mobile 

elements could be relocated from one site to another between human visits. 

The lunar exploration options were informed by the Constellation Program plans. These plans trace to the 2005 

Exploration Systems Architecture Study (ESAS) that was 

established to define an architecture that would comply 

with guidance from the 2004 Vision for 

Space Exploration and the 2003 Columbia Accident Investigation Board 

(CAIB) report. Since ESAS, the human 

spaceflight program continued technical 

trades, culminating in the 2008 Lunar 

Capabilities Concept Review, an architecture-level review that brought together the performance, cost, risk and schedule of the transportation architecture and 

verified that representative lunar surface 

mission goals could be accomplished. 

The Constellation Program’s “1.5 

launch” Earth Orbit Rendezvous-Lunar 

Orbit Rendezvous transportation architecture is shown in Figure 3.4.2-1. The 

flight elements are launched on two 

separate vehicles: the Ares I for launch 

of the Orion spacecraft and crew to lowEarth orbit, and the larger Ares V for 

launch of the Altair lunar lander and 

the Earth Departure Stage (EDS). The 

Orion docks with the Altair/EDS in lowEarth orbit, and the EDS performs the 

trans-lunar injection burn to send the crew to the Moon. 

After a four-day coast to the Moon, the Altair descent module engine performs the lunar orbit insertion maneuver, the 

crew transfers to the Altair, and lands on the surface of the 

Moon. Following the surface stay, the Altair transports the 

crew back into orbit for rendezvous with the Orion, which 

returns to Earth.

The Committee developed the following transportation options to support the lunar scenarios:

• Constellation “1.5 launch” architecture – one Ares I 

with Orion, plus one Ares V with the Altair lander. 

This combination is Integrated Option 3 in Chapter 6.

• Ares V Lite “dual” architecture – two Ares V Lites, 

one with the Orion, and one with the Altair lander. This 

combination is Integrated Option 4A in Chapter 6.

• A more directly Shuttle-derived launcher, which 

requires three launches for a crew mission plus 

one commercial launch of crew to low-Earth orbit. This combination is Integrated Option 4B in 

Chapter 6.

3.4.3 Milestones, Destinations and Capabilities.

The milestones and destinations of the Lunar Base and 

Lunar Global alternatives differ slightly. Both begin with 

a set of sorties to various locations on the lunar surface 

that enable up to four crew members to explore a single 

site anywhere on the Moon for up to seven days. This 

type of mission is accomplished independently of prepositioned lunar surface infrastructure such as habitats 

or power systems. The lunar sorties allow for exploration of high-interest science sites, scouting of future lunar 

outpost locations, or other technology development obFigure 3.4.3-1. Timeline of milestones, destinations and capabilities of the Lunar Base variant of the 

Moon First strategy. Source: NASA
Review of U.S. Human Spaceflight Plans Committee 3 9

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jectives. The Lunar Sortie mission may include surface 

mobility assets and science packages, which the crew can 

operate on daily extra-vehicular activities (spacewalks). 

The Lunar Base alternative proceeds then to the construction 

of a lunar outpost. An example of such a scenario is shown 

in Figure 3.4.3-1. It develops extensive surface roving capabilities, semi-permanent occupancy by a crew of four, and 

resource extraction and utilization capability. In later years, 

it permits the development of additional infrastructure, allowing for science exploration with additional sorties and 

longer-range roving, and developing operational concepts 

and experience for Mars exploration.

In contrast, the Lunar Global alternative proceeds from seven-day sorties to longer-duration visits to two to four sites 

of particular interest, as shown in Figure 3.4.3-2. The first 

long-duration site would have about a 56 day visit, spending 

the lunar night on the surface for the first time, and exploring 

with unpressurized rovers. Subsequent sites would be visited for longer durations, and with more capable exploration 

infrastructure, they would eventually reach the same 180-

day stay as with the Lunar Base. After some number of extended sorties, lunar exploration could be ended, continued 

in extended sortie mode, or transitioned to a base approach.

3.4.4 Assessment. The Moon is a viable first destination for human exploration beyond low-Earth orbit. Lunar 

exploration would allow the development of the capability 

to land on and explore a planetary surface, while still remaining only about three days away from Earth. There are scientific objectives that could be met while visiting the Moon, 

including studying the evolution of the Moon and using the 

surface of the Moon as a record for studying the evolution of 

the solar system. The Moon could compete with other locations as a site for observatories and reduced-gravity surface 

science. It is worth noting, however, 

that prior to the announcement of the 

Vision for Space Exploration in 2004, 

only one site on the Moon (the south 

pole Aitken Basin) was on the highpriority locations for robotic exploration of the inner solar system. There 

is useful science to be performed on 

the Moon, but science is not the driver of human lunar exploration.

The exploration of the Moon should 

be focused to the greatest extent possible on developing the technologies 

and concepts that will be important in 

further exploration of Mars: surface 

descent, landing and ascent; habitation and surface exploration; and resource utilization. The Committee 

explored two strategies for exploring 

the Moon. The Lunar Base and Lunar 

Global strategies each have strengths 

and weaknesses. The Lunar Base allows more efficient utilization of the 

material brought to the surface, and 

more accumulated crew time on the 

surface, important to Mars preparation. The Lunar Global 

approach visits more sites in depth, and more closely simulates the exploration strategy likely to be used on Mars. The 

Committee finds that the Lunar Base and the Lunar Global 

exploration strategies have similar costs, and both provide 

value in exploring the Moon and preparing for the exploration of Mars. 

If explored with either of these Moon First strategies, the 

Moon would help develop some of the technologies and operations concepts needed for Mars exploration, and it would 

develop some of the transportation infrastructure. However, 

the Moon does not serve as a perfect analog for Mars. While 

some of the technology and concepts would be applicable to 

Mars, most of the major system components (landers, habitats, rovers, etc.), if designed and optimized for the Moon, 

would have to be redesigned and re-validated for Mars. Other components of the Mars exploration system (atmospheric 

entry and in-situ resource use, for example) have no analog 

on the Moon. A long-duration exploration of the Moon is 

a step towards Mars, but not a giant step, and not the only 

possible step.

FINDING: THE MOON AS A FIRST

DESTINATION (“MOON FIRST”)

The Moon is a viable first destination for exploration beyond low-Earth orbit. It initially focuses next steps on 

entering and departing deep gravity wells, and developing human operations on the surface of a celestial body, 

which should be developed in a manner that leads to the 

eventual exploration of Mars. The Moon is nearby, allowing relatively rapid return to Earth in the event of 

emergencies, and communication transit times are minimal. It also has interesting scientific and resource issues 

that can be pursued through human exploration. 

Figure 3.4.3-2. Timeline of milestones, destinations and capabilities of Lunar Global variant of the Moon First 

strategy. Source: NASA
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n 3.5 THE FLEXIBLE PATH TO MARS

3.5.1 Overview. In addition to Mars First and Moon 

First, there is a third possibility for initial exploration beyond low-Earth orbit: visiting a series of locations and objects in the inner solar system, which the Committee calls 

the Flexible Path. (See Figure 3.5.1-1.) The goal is to take 

steps toward Mars, learning to live and work in free space 

and near planets, under the conditions humans will meet on 

the way to Mars. We must learn to operate in free space for 

hundreds of days, beyond the protective radiation belts of 

the Earth, before we can confidently commit to exploring 

Mars. Human exploration along the Flexible Path would 

also support science, create new industrial opportunities, 

and engage the public through progressively more challenging milestone accomplishments.

On this path, sites would be visited that humans have never 

reached before. Astronauts would learn to service spacecraft beyond low-Earth orbit, much as crews successfully 

serviced the Hubble Space Telescope in low-Earth orbit. 

Humans could visit small bodies in space, such as nearEarth objects (asteroids and spent comets that cross the 

Earth’s path, some of which could someday collide with 

the Earth - Figure 3.5.1-2) and the scientifically interesting moons of Mars, return samples, and understand their 

structure and composition. When humans would come 

close to the Moon or Mars, they could deploy probes and 

coordinate with or control robotic assets on the surface. 

They could even bring home samples from Mars that were 

launched from the surface by robotic spacecraft. In this 

way we could achieve the scientific “first” of a Mars sample return.

These destinations require the smallest energy expenditure 

beyond low-Earth orbit, but are of increasing distance and 

duration from Earth. The missions could include a full 

dress-rehearsal for a Mars mission, consisting of traveling to 

Mars orbit and returning hundreds of days later. The essential concept is that humans would first visit points in space 

and rendezvous with small bodies and orbit larger ones, 

without initially descending into the deep gravity wells of 

Mars or the Moon. 

The Flexible Path is a road toward Mars, with intermediate 

destinations. At several points along the way, the off-ramp 

from the Flexible Path to a Moon exploration program could 

be taken. Alternatively, if new discoveries drew us to Mars, 

the lunar stop could be bypassed, leading directly to a Mars 

landing.

3.5.2 Scenario Description. The Flexible Path 

constitutes a steadily advancing, measured, and publicly notable human exploration of space beyond Earth orbit that 

would build our capability to explore, enable scientific and 

economic return, and engage the public. The focus of the 

Flexible Path is to gain ever-increasing operational experience in space, growing in duration from a few weeks to several years in length, and moving from close proximity to the 

Earth to as far away as Mars. 

Humans need to build the capability to explore other planets, and to operate far from the Earth. On the Flexible Path, 

critical scientific and technological components of human 

spaceflight would be addressed through incrementally more 

aggressive exploration missions. Determining the human 

Figure 3.5.1-1.There are a variety of destinations that can be targeted using the Flexible Path exploration strategy. Source: NASA

Figure 3.5.1-2. Asteroid Ida – representative of near-Earth objects which are 

possible destinations along the Flexible Path. Source: NASA Galileo Satellite
Review of U.S. Human Spaceflight Plans Committee 4 1

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

physiological and operational impacts of (and the countermeasures to) long-term radiation environment (including 

galactic cosmic rays) and extended exposure to zero-gravity 

is necessary for a sustained human-exploration capability. 

The missions would build preparedness to explore by performing increasingly more complex in-space operations and 

by testing new elements.

The Flexible Path targets planetary scientific return focused 

on multiple locations in the inner solar system. The goal focuses human exploration on producing exciting new science 

at each step of the way. The emphasis would be on obtaining multi-kilogram samples from a variety of solar system y 

bodies through tele-robotic exploration in concert with the 

human missions. In the case of the Moon and Mars, humans 

would remain in orbit. They would deploy probes, teleoperate surface robotic vehicles, and potentially rendezvous 

with sample returns from the surface. In the case of smaller 

objects, humans would explore the surfaces directly and return samples. Robotic missions would play a visible and 

complementary role to human exploration through precursor 

missions and scientific missions that deliver instruments.

A sustained exploration program by the United States requires continuous public engagement, inspiration and benefit. The Flexible Path missions are designed in part to 

cultivate and maintain public support and interest in human 

spaceflight by taking on useful, demonstrably new, high-profile missions. They start with unprecedented space missions 

offering dramatic perspectives of humankind’s home planet 

as a member of the inner solar system, including near-Earth 

objects, the Moon and Mars. 

A set of missions along the Flexible Path might include early 

visits to lunar orbit, stops at the Earth’s Lagrange points, 

near-Earth objects and visits in the vicinity of Mars. A more 

detailed sequence might include:

 • Orbiting the Moon to learn how to operate robots on a 

planet from orbit (days in duration).

 • Visiting the Earth-Moon and Earth-Sun Lagrange points 

(special points at the edge of Earth’s influence), which 

are likely sites for science spacecraft servicing and 

potentially important for interplanetary travel. EarthMoon Lagrange points are about 85 percent of the way 

to the Moon from the Earth. Earth-Sun Lagrange points 

are about four times as far from the Earth as the Moon 

(weeks to months in mission duration).

 • Visiting several near-Earth objects (asteroids or burned-out 

comets whose path cross the Earth), to return samples and 

practice operation near a small body and potentially practice 

in-situ resource extraction (months in mission duration). 

Figure 3.5.2-1. Benefits of various destinations along the Flexible Path. Source: Review of U.S. Human Spaceflight Plans Committee
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 • A fly-by of Mars, demonstrating distant operation and 

coordination with robotic probes on the planetary surface 

and during rendezvous (years in mission duration).

 • A trip to Mars orbit, rendezvousing with and returning samples from Mars’s moons (Deimos and Phobos), and potentially from Mars’s surface (years in mission duration).

A more detailed explanation of the activities at each destination is shown in Figure 3.5.2-1.

Key assumptions for the Flexible Path scenarios include the 

notion that viable and relevant exploration missions can be 

completed with a single crew launch and a single in-space propulsion stage. As additional deep-space capabilities, such as 

in-space habitats, air locks and propulsion stages, become operational, the scope of the missions increases. Flexible Path missions assume the development of certain enabling technologies. 

First among these is a cryogenic in-space propulsion stage able 

to have a near-zero boil-off of propellant over almost 200 days, 

equipped with a high performance in-space re-startable engine. 

Additional enabling technologies are in-space cryogenic fluid 

transfer, improved regenerative life-support systems, technologies for deep space crew-system operational autonomy, and 

tele-robotic systems to be operated by the crew in deep space. 

The Flexible Path branch that proceeds to the lunar surface involves a lander smaller than the Altair lander. For the costed 

option, it is assumed that NASA would provide the ascent 

stage, but a commercially acquired descent stage is envisioned 

that could be developed based on the same in-space re-startable 

engine discussed above. Several complementary robotic missions are coupled and require some technical development—

in particular, the Mars Sample Return mission would use the 

heavy lift in-space propulsion stage to send multiple sampler 

missions in a precursor Mars Entry Descent and Landing (EDL) 

aeroshell to validate technologies for 

eventual human landings on Mars.

For the missions assessed in this 

analysis, an Orion capsule was assumed to be capable of carrying up 

to four crew members and operating 

in space for over a year. However for 

missions longer than about a month, 

an additional in-space habitat sustains the crew. All of the Earth entry, 

descent, and landings were to fall 

within the nominal design requirements for the Orion. The three transportation architectures (see Chapter 

5) considered for Flexible Path missions are:

 • Ares V Lite – an Ares V Lite 

launches with crew aboard the 

Orion capsule. This combination is Option 5A in Chapter 6. 

 • An EELV-heritage super-heavy launcher, which requires 

two launches for earlier missions, and three launches 

for later missions. A commercial service transports the 

crew to orbit, where they transfer to the Orion. This 

combination is Option 5B in Chapter 6. 

 • A Shuttle-derived launcher, which also requires two 

launches for earlier missions, three launches for later 

missions, and commercial transport of the crew to lowEarth orbit. This combination is Option 5C in Chapter 

6.

3.5.3 Milestones, Destinations and Capabili- ties. The milestones and capabilities for the Flexible Path 

are best visualized in Figure 3.5.3-1, which shows the flexibility in the strategy. While the Flexible Path missions can 

be conducted in almost any sequence, many of the missions 

build upon the experience gained from prior ones. All assume a first flight to lunar orbit, and then to the Lagrange 

points, and then to near-Earth objects. The various alternatives are then more apparent. The subsequent flow would 

be to continue into the exploration of Mars, first as a fly-by, 

then to Mars orbit, and finally a Mars landing. Off-ramps to 

the Moon could occur at several spots. Mars is the ultimate 

destination.

A possible sequence that places missions in an order that 

successively expands capabilities and reduces risk is shown 

in Figure 3.5.3-2. This sequence follows the path to nearEarth objects, and then performs a Mars fly-by. The main 

path takes the off-ramp to lunar exploration. This alternative with the lunar off-ramp appears in Chapter 6 among the 

costed options. Another alternative continues Mars exploration with a mission to Mars’s moons. At this point the next 

obvious step is to develop the systems and technologies to 

land humans on Mars.

Figure 3.5.3-1. Options for exploration within Flexible Path strategy showing the main path toward Mars with 

alternatives to the Moon. Source: Review of U.S. Human Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 4 3

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3.5.4 Assessment. The Flexible Path is a viable 

strategy for the first human exploration of space beyond low-Earth orbit. Humans could learn how to live 

and work in space, gaining confidence and experience 

traveling progressively farther from the Earth on longer voyages. This would prepare for future exploration 

of Mars by allowing us to understand the long-term 

physical and emotional stress of human travel far from 

the Earth. It would also validate in-space propulsion 

and habitat concepts that would be used in going to 

Mars.

The missions would go to places humans have never 

been to, escaping from the Earth/Moon system, visiting near-Earth objects, flying by Mars, thereby continuously engaging public interest. Explorers would 

initially avoid traveling to the bottom of the relatively deep gravity wells of the surface of the Moon and 

Mars, but would learn to work with robotic probes on 

the planetary surface. This would allow us to develop 

new capabilities and technologies for exploring space, 

but ones that have Earth-focused applications as well. 

It would also allow us to defer the costs of more expensive landing and surface systems. From the perspective of science, it would demonstrate the ability to 

service observatories in space beyond low-Earth orbit, 

as well as return samples from near-Earth objects and 

(potentially) from Mars.

This flexibility would enable us to choose different 

destinations, or to proceed with the exploration of the 

surface of the Moon or Mars. This allows us to react to 

discoveries that robots or explorers make (such as indications of life on Mars) or eventualities that are thrust 

upon us (such as a threat from a near-Earth object). It 

would lead to a better understanding of near-Earth objects, 

through evaluations of their 

utility as sites for mining of insitu resources, and analyses of 

their structure, should we ever 

need to deflect one away from 

the Earth.

Exploration along the Flexible 

Path would not likely complete 

our preparation for the exploration of Mars. At some point 

we would likely need to gain 

more experience landing and 

working on an extra-terrestrial 

planetary surface. This could 

be done on the Moon with specialized lunar systems, or with 

systems designed for Mars (as 

discussed above in the Mars 

First option). Alternatively, 

we could practice autonomous 

landings of large systems on 

Mars, in coordination with science programs. 

FINDING: DESTINATIONS ON THE FLEXIBLE 

PATH TO MARS

The destinations on the Flexible Path (lunar orbit, Lagrange 

points, near-Earth objects, Mars fly-bys, Mars orbits, and 

Mars moons, with potential operation of robotic missions 

on the lunar and Martian surfaces) comprise a viable and 

interesting first set of destinations for exploration beyond 

low-Earth orbit. They are progressively more distant, focusing our next steps on allowing the development and 

understanding of human operations in free space for the 

increasingly longer durations necessary to explore Mars. 

Important scientific, space operational, and Earth-protection benefits would be obtained on this path. 

n 3.6 SUMMARY OF STRATEGIES FOR 

EXPLORATION BEYOND LOW-EARTH 

ORBIT

This chapter addresses the question: What is the most practicable strategy for exploration beyond low-Earth orbit: Mars 

First, Moon First, or the Flexible Path to Mars?

The Committee found that, although Mars is the ultimate 

destination for human exploration in the inner solar system, 

it is not a viable first destination. We do not now have the 

technology or experience to explore Mars safely and sustainably.

Both the Moon First and Flexible Path are viable strategies. Exploring the Moon would prepare us for exploration of Mars by allowing us to learn to live and work on a 

remote surface, yet one that is only three days from Earth. 

Figure 3.5.3-2. Timeline of milestones, destinations and capabilities of the Flexible Path strategy. Source: NASA
4 4 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

ture to Mars, and therefore the potential expansion of human civilization into the solar system. Many opportunities 

could be identified in either pathway for deep involvement 

of international partners, as will be suggested in Chapter 8. 

Science returns, technology and economic development, and 

exploration preparation will follow from either strategy. 

The primary question is: Will the public be engaged? Gone 

is the era when Americans remembered the names of astronauts, or even the date of the next space launch. We cannot take for granted that space excites young people; rather, 

we must make sure that we build a program that will excite 

them. In its plan for exploration, NASA must find new ways 

to engage the public, particularly young people, in a venture of participatory exploration, one that will be exciting 

to them. This should not be an afterthought—it must be an 

integral part of the program.

FINDING: PATHWAYS TO MARS

Mars is the ultimate destination for human exploration 

of the inner solar system; but it is not the best first destination. Both visiting the Moon First and following the 

Flexible Path are viable exploration strategies. The two 

are not necessarily mutually exclusive; before traveling 

to Mars, we might be well served to both extend our 

presence in free space and gain experience working on 

the lunar surface. 

The Flexible Path would prepare us for exploration of Mars 

by developing confidence that we can live and work in free 

space, and allowing us to learn to explore planets and bodies in a new way, potentially in coordination with robotic 

probes.

The Moon First and Flexible Path destinations are not mutually exclusive; before traveling to Mars, we will probably 

both extend our presence in free space and work on the lunar 

surface. For example, if we had had explorers on the Moon 

for a decade, but never more than three days from Earth, 

would we easily commit to a mission that took our astronauts away for three years? This seems unlikely. Likewise, 

if we had worked in space for a decade, would we commit 

to landing on a planet 180 days away without practice? This 

seems equally unlikely. 

Before we explore Mars, we will likely do some of both 

the Flexible Path and lunar exploration—the primary decision is one of sequence. This will be largely guided by 

budgetary, programmatic, and program sustainability considerations. These will be discussed in Chaper 6. Whatever 

destination(s) are selected, it would be desirable to have a 

spectrum of program choices that offers periodic milestone 

accomplishments visible to and appreciated by the public. 

Before leaving the topic of strategies for exploration, it is 

important to reflect back on the goals for human spaceflight. 

The strategies have certainly focused on preparing for a ven-
Review of U.S. Human Spaceflight Plans Committee 4 5

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The current U.S. human spaceflight programs are the operational Space Shuttle Program and the U.S. portion of 

the International Space Station (ISS). The next human 

spaceflight effort, the Constellation Program, is in development.

n 4.1 THE SPACE SHUTTLE 

The Committee has addressed five questions that, if answered, would form the basis of a plan for U.S. human 

spaceflight. First among those questions is: what should 

be the future of the Space Shuttle?

The current plan is to retire the Shuttle at the end of FY 

2010. Six flights are remaining on the manifest, with the 

final flight scheduled for September 2010. Once the Shuttle is retired, there will be a gap in America’s capability 

to independently launch people into space. That gap will 

extend until the next U.S. human-rated launch system becomes available. 

In analyzing the future of the Shuttle, the Committee considered whether the current flight schedule is realistic. It 

also weighed the risks and possible benefits of various 

Shuttle extension options. This section provides a brief 

background on the Space Shuttle, a discussion of important 

issues, and a description of the scenarios considered for 

inclusion in the integrated options presented in this report.

4.1.1 Background. 

The Space Shuttle, introduced in 1981, is fundamentally 

different from all previous U.S. launch systems. (See Figure 4.1.1-1.) It lifts astronauts to orbit in a spaceplane, not 

a capsule, and it lands on a runway, not with a splash in the 

ocean. The spaceplane has a cargo bay to carry satellites 

and experiments with it into space and back to Earth, and it 

can be flown again and again. 

The Shuttle has been the workhorse of the U.S. human 

spaceflight program since its first launch. In its 28 years 

of operations, it has flown 128 times, 126 of those successfully. Two tragic accidents mar its record. Space Shuttle 

missions have evolved considerably in focus, capability 

and complexity over that period. They have progressed 

from early flight tests to operations, which included satellite deployments, tests of a robotic arm, and early scientific experiments. Immediately after the Space Shuttle 

Challenger accident in 1986, the launch of satellites shiftCurrent Human Spaceflight Programs

Chapter 4.0

Figure 4.1.1-1. The principal components of the Space Shuttle. 

Source: NASA
4 8 Review of U.S. Human Spaceflight Plans Committee

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ed from the Shuttle to expendable launch vehicles, and 

Shuttle missions evolved into more sophisticated science 

and operational missions, including Spacelab flights, repair and servicing of the Hubble Space Telescope, and the 

Shuttle Radar Topography Mission. 

In the late 1990s, the focus of Shuttle missions transitioned 

to the assembly, logistics support, and maintenance of the 

International Space Station. The Space Shuttle Columbia

accident in early 2003 interrupted that work, grounding the 

Shuttle for nearly two and a half years while NASA addressed 

the technical, procedural and organizational problems identified during the accident investigation. When the Shuttle 

returned to flight, its missions concentrated almost entirely 

on completing assembly of the Space Station. The President’s 2004 Vision for Space Exploration directed NASA to: 

“Focus use of the Space Shuttle to complete assembly of the 

International Space Station; and retire the Space Shuttle as 

soon as assembly of the International Space Station is completed, planned for the end of this decade.” 

Subsequently, several Shuttle flights planned to support the 

International Space Station assembly and utilization were 

cancelled, and NASA was directed to complete the remaining Shuttle flights by the end of FY 2010. At the time, the 

Constellation Program’s replacement for the Shuttle was 

projected to be ready in 2012, leaving a two-year “gap” in 

the nation’s ability to launch humans into low-Earth orbit.

As of the end of FY 2009, the Shuttle has flown successfully 

15 times since returning to flight in 2005. Missions are now 

far more intricate and complex than earlier Shuttle flights, 

and they illustrate significant growth in the ability to operate 

in space. While early missions were routinely four to seven 

days, and rarely included a spacewalk, missions today are 

often two weeks long, and have included as many as five 

complex and well-orchestrated spacewalks. As of September 2009, six flights remain in the Shuttle manifest, with the 

last flight scheduled for September 2010. There is currently 

modest funding in the FY 2011 budget to cover Shuttle retirement costs, but none for flight operations.

4.1.2 Issues. 

In considering the future of the Space Shuttle, the Committee paid particular attention to safety, schedule, workforce, 

and the program’s fixed costs. 

Schedule. To assess the viability of the current Shuttle 

schedule, the Committee compared the actual post-Columbia

flight rate (July 2005 through STS-128, the last flight in FY 

2009) with the projected flight rate for the remainder of the 

current manifest. In the post-Columbia period through the 

end of FY 2009, there was an average of 100 days between 

flights. In contrast, the current manifest shows an average of 

only 64 days between the remaining six flights. While it is 

not impossible to achieve this latter flight rate, the projected 

rate is not consistent with recent or prior experience. Further, 

Space Shuttle managers have indicated that there is little or 

no margin in the remaining schedule. Experience suggests 

that it is very likely the currently manifested flights will 

extend into the second quarter of FY 2011. 

The Committee also took note that the Columbia Accident Investigation Board (CAIB) cited schedule and 

budget pressure as a contributing factor in the Columbia

accident. The Board observed, “Little by little, NASA 

was accepting more and more risk in order to stay on 

schedule.” It recommended that NASA: “Adopt and 

maintain a Shuttle flight schedule that is consistent with 

available resources” and added that “Although schedule deadlines are an important management tool, those 

deadlines must be regularly evaluated to ensure that any 

additional risk incurred to meet the schedule is recognized, understood, and acceptable.” 

Figure 4.1.2-1. Space Shuttle Program contractor workforce under existing plan. Source: Briefing to the Review of U.S. Human Spaceflight Plans Committee 

Note : *Includes the workforce for the four largest Space Shuttle contractors only (not NASA space employees). 
Review of U.S. Human Spaceflight Plans Committee 4 9

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NASA and the Committee are well aware that schedule 

pressure can have a subconscious influence on decisionmaking, and has asked for, and received, relief from the 

requirement to fly out the manifest by the end of FY 

2010. The Administration has directed that NASA complete the remaining manifest safely, even if that requires 

extending into FY 2011. The looming problem, however, is that there is currently no funding in the FY 2011 

budget to support this likely occurrence.

Workforce. The most visible ramification of the 

impending gap in U.S. human spaceflight is the lengthy 

loss of ability for the U.S. to launch humans into space 

independently. A less well-publicized ramification is the 

potential loss of the knowledge and skill base that makes 

America’s human spaceflight program possible. 

The Space Shuttle is currently operated by a skilled 

workforce of over 12,500 individuals whose experience 

and expertise in systems engineering, systems integration, inspection, ground operations and assembly, test 

and checkout, and mission planning and operations have 

been developed and honed over decades. Once the Shuttle is retired, NASA and its contractors will be forced 

to shed or reassign much of that workforce due to the 

length of the gap in human spaceflight activity. Of these 

12,500 workers, 1,500 are civil servants who, under current practices, will likely retain their jobs even though 

there is no program to which they can easily transition. 

The jobs in the contractor structure will likely be lost. 

(See Figure 4.1.2-1.) When the human spaceflight program resumes in the second half of the next decade, a 

great deal of the knowledge, experience and critical 

skills necessary for successful program execution is 

likely to have atrophied or have been lost altogether. 

Over the past 45 years, the U.S. has enjoyed a relatively 

continuous program of human spaceflight. This continuity enabled engineers, flight operations personnel and 

technicians to learn skills and train successors in an apprentice model, and to capture and transfer knowledge 

from one program to the next. The longest previous gap 

occurred between the Apollo-Soyuz mission in 1975 and 

the first Shuttle flight in 1981. But even as late as 1977, 

the Shuttle was projected to fly in 1979. As a result, 

only a year or two after Apollo-Soyuz flew, much of 

the workforce was actively engaged in ground processing, systems engineering, integrated testing, flight crew 

training and mission planning for Shuttle.

The Committee is concerned about the retention of 

critical knowledge and skills and the availability of that 

unique portion of the workforce necessary to conduct 

the next set of human spaceflight missions—which, as of 

now, cannot be expected until late in the next decade. 

Safety. The Committee’s charter did not call for it to 

review the safety record or assess the reliability of the 

Shuttle. The Committee did, however, consider Shuttle 

safety and reliability in its deliberations. One of the 

recommendations of the Columbia Accident Investigation Board (CAIB) spoke directly to this issue: “Prior 

to operating the Shuttle beyond 2010, develop and conduct a vehicle recertification at the material, component, 

subsystem, and system levels. Recertification requirements should be included in the Service Life Extension 

Program.” 

As part of the Shuttle “Return to Flight” program after the 

Columbia accident and in the years since, NASA has recertified much of the Shuttle system. NASA’s Space Shuttle 

program managers believe the program is meeting the intent 

of the CAIB’s recommendation and would be ready to fly 

the Shuttle beyond 2010, should the need arise. This Committee suggests that an independent review of the Shuttle 

recertification process be undertaken if a decision is made to 

add flights to the current manifest.

How reliable and how safe is the Shuttle, particularly when 

compared to other existing or proposed launch vehicles? 

As noted previously in this report, flying in space is inherently risky, so it is not appropriate to call any launch vehicle 

“safe.” Several factors contribute to a launch vehicle’s risk: 

the design itself; the extent to which the limitations of that 

design are understood; the processes and people involved 

in preparing, launching and operating the vehicle; and “random” component or system failures. Studies of risk associated with different launch vehicles (both human-rated and 

non-human-rated) reveal that many accidents are a result of 

poor processes, process lapses, human error, or design flaws. 

Very few result from so-called random component failures. 

The often-used Probabilistic Risk Assessment (PRA) is a 

measure of a launch vehicle’s susceptibility to these component or system failures. It provides a useful way to compare 

the relative risks of mature launch vehicles (in which the 

design is well understood and processes are in place); it is 

not as useful a guide as to whether a new launch vehicle will 

fail during operations, especially during its early flights.

The Shuttle is one of the few launch vehicles that have flown 

a sufficient number of times to be considered “mature.” It has 

suffered two accidents in its 128 flights, so its demonstrated 

success rate is 98.4 percent. Considerable effort has also been 

expended to develop a Probabilistic Risk Assessment for 

the Shuttle. That PRA shows a reliability of 98.7 percent, 

with the greatest contributor to risk coming from the threat 

of micrometeorite or debris damage while in orbit. Other 

launch vehicles in development have better PRAs, indicating 

that once they reach maturity, they will carry less risk than 

the Shuttle. In comparing Shuttle reliability to that of other 

launch vehicles, however, the most important factor is actual 

flight experience. The Shuttle completed its first 24 missions 

successfully before the Challenger accident; after returning to 

flight, it flew successfully 87 times before the Columbia accident, and has flown successfully 15 times since. This is not to 

say that future vehicles will not be more reliable—they likely 

will be—but the Shuttle has reached a level of maturity that 

those launch vehicles will not reach for many years. (Those 

vehicles still have their “infant mortality” phase ahead of 

them. The Committee cannot resist citing one of Augustine’s 

Laws: “Never fly on an airplane with a tail number less than 

10!” That law encapsulates the value of flight experience.1

)

1 Norman R. Augustine, Augustine’s Laws (Washington, D.C.: American Institute of 

Aeronautics and Astronautics), 1986.
5 0 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

The current program ensures that we will have no failures of U.S. government human-rated crewed launch 

systems from 2011 through at least 2017—because there 

likely will be no flights of those launch vehicles during 

that period. The Committee considered whether the risk 

associated with extending Shuttle operations is appropriate. In doing so, it considered whether it is acceptable 

to complete the current manifest and, if so, whether the 

risk is acceptable for some number of additional flights 

(assuming the current level of attention to mission assurance, processes and procedures is maintained.) The 

Committee believes the risk of flying out the current 

Shuttle manifest is consistent with past experience if 

conducted on a schedule and budget that do not impose 

undue pressure and constraints. The Committee also 

believes the risk of some extension beyond the current 

manifest may be acceptable, assuming the certification 

process discussed above is successfully completed and 

the current emphasis on mission assurance is continued.

Fixed Costs. The annual Shuttle budget is approximately 

$3 billion per year, depending on the number of flights. 

The retirement of the Shuttle is expected to free funds for 

the Constellation Program, and the common perception 

is that with the Shuttle no longer flying, there will be an 

additional $3 billion per year available for design, development, testing and deployment of the new exploration 

program. The situation is more complicated, however, 

and the actual benefit to the Constellation Program is 

considerably less than $3 billion per year. The principal 

reason is that the Shuttle Program today carries much of 

the costs of the facilities and infrastructure associated 

with the human spaceflight program as a whole. But 

those facilities will continue to exist after the Shuttle is 

retired—so their costs must still be absorbed if the facilities are to be preserved. 

These fixed costs are significant—about $1.5 billion per 

year—and include, for example, nearly 90 percent of the costs 

of running: the Kennedy Space Center; the engine test facilities at the Stennis Space Center in Mississippi; a Mission 

Control Center in Houston; and the Michoud Assembly Facility in Louisiana. Unless such facilities are mothballed or disposed of, these costs will simply transfer to a different NASA 

program; in fact, most will have to be absorbed by the Constellation Program. During its fact-finding phase, the Committee discovered that approximately $400 million per year 

of these fixed costs are not yet reflected in the Constellation 

budget after Shuttle retirement. But the costs do have to be 

allocated somewhere in the NASA budget, and will certainly 

affect the overall funding available for exploration. Some of 

the Shuttle funding pays for NASA civil servants who, absent major layoffs, will simply transition to other spaceflight 

programs. Constellation will thus gain both human resources 

and the costs associated with them; in the case of facilities, 

Constellation will soon be paying for their maintenance.

In summary, the savings resulting from Shuttle retirement 

are not as great as they may appear. Conversely, the marginal costs of flying the Shuttle are less than implied by 

the existing bookkeeping. The next human spaceflight 

program will assume most of the fixed costs; the net funds 

available for Constellation design, development, test and 

evaluation (DDT&E) or facilities conversion as a result of 

Shuttle retirement total about $1.6 billion per year—absent 

structural changes to NASA. 

4.1.3 Shuttle Options

The Committee selected three possible Shuttle scenarios to 

consider for inclusion in the integrated options presented 

later in this report: flying out the Shuttle manifest (at a 

prudent rate); adding one flight to provide short-term support for the ISS; and closing the gap by extending Shuttle 

to 2015 at a minimum flight rate. 

• Scenario 1: Prudent Shuttle Fly-Out. As noted, the 

current Shuttle schedule has little or no margin remaining. Scenario 1 is a likely reflection of reality. It restores 

margin to the schedule, at a flight rate in line with recent 

experience, and allocates funds in FY 2011 to support 

Shuttle operations into that fiscal year. Based on historical data, the Committee believes it is likely that the 

remaining six flights on the manifest will stretch into the 

second quarter of 2011, and it is prudent to plan for that 

occurrence and explicitly include the associated costs in 

the FY 2011 budget.

• Scenario 2: Short-Term Support for the ISS. Space 

Shuttle retirement will have an impact on the ISS (described more fully in a subsequent section). Scenario 2 

would add one additional Shuttle flight to provide some 

additional support for the ISS and ease the transition to 

commercial and international cargo flights. It could enhance early utilization of the ISS, offer an opportunity 

for providing more spare parts, and enable scientific experiments to be brought back to Earth. This additional 

Shuttle flight would not replace any of the planned international or commercial resupply flights.

One obvious question is: “Why add just one flight?” Due 

to the planned retirement, the Shuttle’s external tank production line has been closed recently, and it is not costeffective to re-open it for a small number of new tanks. 

However, there is one spare external tank remaining in inventory. This scenario thus envisions using that tank and 

conducting one additional Shuttle flight in late FY 2011 or 

early FY 2012.

This scenario requires that funds be put in the in FY 2011 

and possibly FY 2012 budget for the one additional Shuttle flight. This minimal extension does not mitigate the 

workforce transition issues; it does extend U.S. human 

spaceflight capability, but only by a few months; and it 

does offer some additional short-term logistical support 

to the ISS.

• Scenario 3: Extend Shuttle to 2015 at Minimum Flight 

Rate. This scenario would extend the Shuttle at a minimum safe flight rate (nominally two flights per year) into 

FY 2015. Once the Shuttle is retired, the U.S. itself will 

no longer have the ability to launch astronauts into space, 

and will have to rely on the Russian Soyuz vehicle. That 

gap will persist until a new vehicle becomes available 

to transport crew to low-Earth orbit. Under the current 
Review of U.S. Human Spaceflight Plans Committee 5 1

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

program, the resulting gap is expected to be seven years 

or more. This scenario, if combined with a new crew 

launch capability that will be available by the middle of 

the 2010s, significantly reduces that gap, and retains U.S. 

ability to deliver astronauts to the ISS.

 The impending gap also directly affects the ISS, which was 

designed and built assuming that the Shuttle was available 

to carry cargo and crew to it and to bring cargo and crew 

back to Earth. During the gap, the U.S. will pay for U.S. and 

international-partner astronauts to be carried to and from the 

ISS by the Russian Soyuz. Cargo, including supplies, spares, 

experiments and other hardware, will be carried to the ISS 

by a complement of international and U.S. commercial cargo vehicles. None of these can carry nearly as much as the 

Shuttle, and only one is projected to be able to bring anything 

back to Earth. This could limit the full utilization of the ISS. 

Further, only two of these vehicles have flown—each one 

only once. Delays could place ISS utilization further at risk, 

particularly in the early part of the coming decade. This scenario does not envision replacing any of the planned international or commercial cargo launches with Shuttle flights, but 

rather, enhancing U.S. and international partner capability to 

robustly utilize the ISS. All commercial and international 

cargo flights would remain as planned.

The Committee has concluded that the only way to eliminate 

or significantly reduce the gap in human spaceflight launch capability is by extending the Shuttle Program. If that is an important consideration, then this scenario is one to examine. The 

scenario also minimizes workforce transition problems, and it 

retains the skills that currently enable the U.S. to enjoy a robust 

human spaceflight program. Because this scenario extends the 

Shuttle’s life well beyond 2010, if adopted it should include a 

thorough review of NASA’s safety certification program by an 

independent committee to ensure that NASA has met the intent 

behind recommendation R9.2-1 of the Columbia Accident Investigation Board.

Scenario 3 would require additional funding for Shuttle extension. Assuming that many of the current fixed costs must be carried somewhere in the NASA budget, the relevant cost of this 

option is the marginal cost of flying the Shuttle. There are two 

factors to consider in estimating this cost. First, if the Shuttle 

extension is coupled with a strategy to develop a more directly 

Shuttle-derived heavy-lift vehicle, as opposed to the Ares family, 

there would be synergy that takes maximum advantage of existing infrastructure, design and production capabilities. Second, 

since the Shuttle would be available to carry crew to and from 

the ISS, there would be some savings because the U.S. would not 

need to purchase Russian Soyuz flights (the present plan).

Most of the integrated options presented in Chapter 6 would 

retire the Shuttle after a prudent fly-out of the current manifest, 

indicating that the Committee found the interim reliance on 

international crew services acceptable. However, one option 

does provide for an extension of the Shuttle at a minimum safe 

flight rate to preserve U.S. capability to launch astronauts into 

space. As Chapter 5 will show, the Committee finds that in the 

long run, it is important for the U.S. to maintain independent 

crew access to low-Earth orbit.

FINDINGS REGARDING THE SPACE 

SHUTTLE

 Short-term Space Shuttle planning: The remaining Shuttle manifest should be flown in a safe and prudent 

manner. This manifest will likely extend operations into the 

second quarter of FY 2011. It is important to budget for this 

likelihood. 

 The human spaceflight gap: Under current conditions, 

the gap in U.S. ability to launch astronauts into space is most 

likely to stretch to at least seven years. The Committee did 

not identify any credible approach employing new capabilities that could shorten the gap to less than six years. The only 

way to close the gap significantly is to extend the life of the 

Shuttle Program.

 Shuttle extension provisions: If the Shuttle life is extended beyond 2011, an independent committee should assess NASA’s Shuttle recertification to assure compliance with 

the Columbia Accident Investigation Board Recommendation R9.2-1. The investment necessary to extend the Shuttle 

makes the most sense in the context of adopting a Shuttlederived heavy-lift capability in place of the Ares family and 

extending the life of the ISS. 

 Fixed costs: Because a substantial fraction of the costs of 

the human spaceflight infrastructure is currently allocated to 

the Shuttle Program, the savings resulting from Shuttle retirement are not as great as they may appear. If current operating 

constraints on NASA are maintained, these costs will simply 

be transferred to whatever becomes the continuing exploration program. 

n 4.2 THE INTERNATIONAL SPACE STATION

The second question the Committee addressed to form the 

basis of a plan for U.S. human spaceflight was: What should 

be the future of the International Space Station?

NASA’s current plan is to decommission the International 

Space Station at the end of FY 2015. The Committee believes there is no reasonable path to continue operation of 

the ISS once U.S. participation ends; thus, de-orbiting the 

facility in early 2016 will be required for ground safety reasons. 

In deliberating the ISS’s future, the Committee considered 

the realism of the current plan, the advantages and disadvantages of that plan, and the advantages and disadvantages of 

various scenarios that would extend the life of the ISS. This 

section provides a brief background on the ISS, a discussion of important issues, and a description of the scenarios 

considered for inclusion in the integrated options presented 

later in the report.

4.2.1. Background.

President Ronald Reagan called for the construction of Space 

Station Freedom (Figure 4.2.1-1) in 1984 as an expression 

of America’s continuing leadership in human spaceflight. 

With the end of the Cold War, however, the U.S. approach to 

building the Space Station changed. Space Station Freedom
5 2 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

Figure 4.2.1-1. President Reagan and Prime Minister Thatcher, with model 

of Space Station Freedom, which later evolved into the International Space 

Station. Source: The Ronald Reagan Presidential Foundation and Library

became the International Space Station in 1993, when 

President Clinton encouraged the partnership to invite 

Russia to join the international group building the Station. (Reference Figure 4.2.2-2) The ISS is among the 

more complex technological endeavors ever undertaken 

(some would argue the “most”), involving five space 

agencies representing 16 nations. Soon to be completed, this new outpost will include contributions from the 

United States, Canada, Japan, Russia, Brazil, Belgium, 

Denmark, France, Germany, Italy, the Netherlands, Norway, Spain, Sweden, Switzerland and the United Kingdom. Within the U.S., the ISS effort involves more than 

100,000 people in 37 states, including a presence at some 

500 contractor facilities.

Reorienting the program to facilitate Russian participation 

was considered a major signal of America’s willingness 

to work with a former adversary. The agreement called 

for the Space Shuttle and Russian Soyuz to fly crew to 

the Station, and for the Shuttle and the Russian Progress 

to resupply the Station. In 1998, Russia’s Zarya module 

was the first to be deployed, and the ISS has been continuously inhabited since 2000. As many as 13 people have 

occupied the Station and the docked Shuttles at one time. 

Russian launches sustained the ISS after the Columbia accident in 2003 until the Shuttle returned to flight in 2005. 

Now, in 2009, after nearly 10 years of continuous human 

habitation with a reduced crew, the ISS supports its full 

six-person crew. Six more Shuttle missions remain until 

the ISS construction is completed.

Aside from the Space Station itself, perhaps the most 

valuable outcome of the ISS Program is the development 

of strong and tested working relationships among the ISS 

partners. The partnership resolved numerous technical 

challenges, withstood changes in governments, policies 

and budgets, and it survived the Columbia tragedy. The 

imminent completion of the ISS demonstrates that many 

nations can learn to work together toward a difficult common goal. The effort also expresses a U.S. leadership 

style adapted to the multi-polar world that emerged after 

the Cold War.

ISS completion also marks a transition for the conduct of 

NASA’s human spaceflight program, not only because the 

ISS partners will turn from building the Station to using 

it, but also because the Space Shuttle is nearing the end 

of its planned operational life. How will the Station be 

staffed in the gap between Shuttle decommissioning and 

the availability of new U.S. launch vehicles? Has NASA 

made the best arrangements for full utilization of the ISS? 

For these reasons alone, it is time to reexamine how the 

United States will use the ISS. 

There are other considerations as well. The U.S. made 

a significant sacrifice in order to complete the ISS and 

fulfill its obligations to its partners: the science and engineering development program that might have been conducted on the station was curtailed. Perhaps the absence 

of a significant community of U.S. science users made it 

easier for NASA to propose discontinuing station operations in 2015. But is it wise to cease operations after only 

five years of full utilization when the station has been 25 

years in planning and assembly? Would extension of ISS 

operations from five to at least ten years enable more new 

ideas, based on today’s science and technology, to be introduced through flight on the ISS? When the ISS was 

first designed, there was little thought about using it to 

prepare for exploration beyond low-Earth orbit. Can ISS 

utilization advance exploration goals beyond low-Earth 

orbit? 

4.2.2 Issues. 

In considering the future of the ISS, the Committee examined issues related to the U.S. human spaceflight gap, cargo 

and crew resupply and the commercial launch industry, end 

of ISS life, ISS safety, and international relations. Several 

of the issues are intertwined, and several arise as a result of 

the impending retirement of the Space Shuttle. 

“The Gap.” The Space Station was conceived, designed 

and built with the Shuttle in mind. Its operational strategy, 

utilization capacity, and philosophy of maintenance and 

spares were all developed assuming the availability of the 

Shuttle. 

How will U.S. crew be transported to the ISS after Shuttle 

retirement? The U.S. will depend on Russian launches until 

a new U.S. spacecraft and human-capable launch vehicle become operational. For several years the U.S. will pay Russia to transport our astronauts to the ISS. Further, under 

existing international agreements, the U.S. is responsible for 

transporting astronauts from Canada, Japan, and the European Space Agency to the ISS, so the U.S. will presumably 

also be paying Russia for their transport. This period is now 

expected to extend for seven years. 

How will the U.S. transport cargo to and from the ISS? The 

U.S. plans to stop using Russian Progress vehicles for cargo 

transport in 2011, although this launch vehicle would continue to fulfill Russian needs. The program of record relies 
Review of U.S. Human Spaceflight Plans Committee 5 3

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

on a combination of international and commercial capabilities currently under development. These include the European ATV and Japanese HTV, each of which has flown to the 

ISS once, and two new commercial capsules which, along 

with their rockets, Dragon and Cygnus, are still in development. (See Figure 4.2.2-1.)

The potential issues for the Space Station include: (1) none 

of these cargo carriers has nearly the cargo capacity of the 

Shuttle; (2) only the Dragon is planned to have a capability 

to bring cargo (e.g., experiments, failed parts, etc.) back to 

Earth; (3) two of these systems have flown once successfully, and the other two are untested. ISS resupply will thus 

depend on a mix of as-yet relatively less mature or unproven 

systems after the Shuttle is retired. While the diversity of 

options gives reason to believe that ISS servicing and resupply can be accomplished, there is little assurance that 

the new vehicles and capsules will be operational on their 

planned schedules.

Even today, to supply the ISS with more than the basic essentials for a crew of six using the Shuttle is proving to be a challenge. The Committee notes that while the postSpace Shuttle cargo plan may sustain basic ISS operations, 

it could put the ISS on a somewhat fragile footing in terms 

of utilization. There is little surge capacity for unforeseen 

maintenance or logistics needs, and since utilization has 

been shown to be the first to suffer when funding pressures 

rise, the projected capacity may prove insufficient to support 

meaningful ISS utilization. 

End-of-Life Considerations. How and when should the 

ISS be de-orbited? What should be returned to Earth before 

ISS de-orbit? Will the “down-mass” capabilities at the time 

of de-orbit allow significant retrieval of valuable equipment, 

experiments and facilities? How far in advance of a planned 

de-orbit should consultations among the international partners take place? These are a few of the issues that must be 

considered before a de-orbit can be implemented. 

Because of its unprecedented size and mass (about 350 mt 

on orbit), de-orbiting the ISS is not a simple task. (See Figure 4.2.2-3.) There are currently no existing or planned 

Figure 4.2.2-1. ISS resupply vehicle payload capacities: Shuttle, Russian 

Progress, Japanese H-II Transfer Vehicle, European Automated Transfer 

Vehicle, SpaceX Corp. Dragon and Orbital Sciences Corp. Cygnus. Bars 

indicate the cargo capacity in kilograms. Source: Review of U.S. Human 

Spaceflight Plans Committee

Figure 4.2.2-2. The International Space Station as seen against Earth’s 

horizon. Source: NASA (STS-119 Shuttle mission imagery)

Figure 4.2.2-3. The relative challenge of re-entry of the International 

Space Station as compared with earlier re-entry/debris events. (Diagrams 

approximately to scale). Source: The Review of the U.S. Human Spaceflight 

Plans Committee
5 4 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

vehicles that could de-orbit the 

entire ISS in a predictable manner. Thus, either a new de-orbit 

module would have to be produced and launched to the ISS, 

or the station would have to be 

disassembled and the major 

portions de-orbited individually. The Committee requested 

an independent assessment of 

the difficulty of this task, and 

an estimation of the potential 

cost. The projected costs are 

$2 billion or more, depending 

on the method of de-orbiting 

required.

The Committee also considered the possibility that the ISS 

could be operated with minimum U.S. participation, rather 

than be de-orbited. Preliminary 

considerations suggest that it 

would be nearly impossible 

for the remaining international partners to operate the ISS 

because of the extreme stress 

on their smaller budgets, and 

because U.S. export control 

requirements would limit the 

direct support the U.S. could 

provide to foreign space agencies.

Another alternative would be to “mothball” the ISS in space 

for later use. In order to assure any future utility, it appears 

preferable to keep the ISS staffed at a minimum level, 

similar to that adopted in the early phases of construction. 

Probabilistic risk assessments find a factor of five increase 

in probability of loss of the ISS with no crew on board. 

The need to keep the station occupied would be substantial. 

There is also a risk that an unoccupied ISS could enter the 

Earth’s atmosphere in an uncontrolled manner, resulting in 

liability issues and international difficulties for the U.S. In 

summary, it does not appear that either mothballing the ISS 

or ending U.S. participation is a viable option, and keeping 

the Station occupied is very expensive.

The extension of the ISS operations brings its own technical 

issues. Currently, if a significant part fails on the ISS, this 

part is returned to Earth and refurbished. Once the Shuttle retires, that will no longer be possible; new parts will 

have to be procured and lifted to the ISS. To prepare for 

Shuttle retirement, NASA has begun carrying spare parts up 

to the ISS—this provisioning is intended to supply the ISS 

through 2015. If the ISS is extended, additional spares must 

be procured and the suppliers retained. Further, there are 

a few parts too large for any of the planned cargo vehicles 

to lift. In addition, some components of the ISS (e.g., the 

U.S. laboratory) will reach the end of their certified life in 

2015 or shortly thereafter. It is clear to the Committee that 

if the ISS is to be extended, planning for that should begin 

immediately. 

ISS Utilization and the User Community. For the past decade, efforts on the ISS have been directed toward assembly 

and early operation. Budgetary pressures during construction left little money for utilization. This is still the case. 

Today, less than 15 percent of NASA’s ISS budget is allocated for utilization. As the facility grows, its capacity may 

not be fully used. (See Figure 4.2.2-4.) Further, the current 

plan funds ISS utilization at approximately the same level 

through 2015. At the same time, however, the 2005 NASA 

Authorization Act designated the U.S. segment of the ISS 

as a National Laboratory and directed NASA to develop a 

plan to “increase the utilization of the ISS by other federal 

entities and the private sector...” It would be difficult if not 

impossible to realize the potential envisioned in the Congressional language at the current level of utilization.

How well the ISS is exploited depends to a considerable 

degree on whether its management focuses on utilization. 

With relatively few U.S. users, it may not have seemed 

worth restructuring utilization management of a program 

that was slated for termination after only five years of full 

operation. In the context of ISS renewal, however, a new 

management approach that facilitates the use of the ISS by 

a broad range of scientific, technological, and commercial 

users is warranted. The Committee believes that an organization is needed to mediate between NASA operations 

managers and the broad stakeholder community. This could 

facilitate access to ISS assets by a disparate user community 

(with widely varying levels of sophistication about spaceflight activities), and could help organize the multiple deFigure Figure 4.2.2-4. Major research facilities and support capabilities of International Space Station. 

Source: Review of the U.S. Human Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 5 5

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

mands of the users into more unified requirements. Without a mediated dialogue between operations managers and 

users, it will be difficult to realize operational efficiencies. 

There are numerous examples of existing organizations that 

should be examined as possible models.

4.2.3 Scenarios for the Future of the ISS. 

The Committee examined three scenarios for the future of 

the International Space Station. The first is essentially the 

program of record; that is, terminate U.S. participation in 

the ISS at the end of 2015. The second, “steady as you go,” 

renews U.S. participation at the current level to 2020, and 

assumes that launch vehicle development will proceed at a 

pace determined by whatever the remaining budget permits. 

The third enhances U.S. utilization and (possibly) international participation through at least 2020. 

Scenario 1: End U.S. Participation in the ISS at the End 

of 2015. The current program of record terminates U.S. 

participation in the ISS at the end of 2015, and it calls for 

decommissioning and de-orbiting the ISS by early 2016. 

This approach is reflected in NASA’s current budget projections, though with insufficient funds for de-orbiting. 

NASA’s 2008 Authorization Bill, however, directed the 

agency to take no steps that preclude extending ISS operations until 2020, and NASA has complied. This scenario 

constitutes the current program plan. Under this scenario, 

15 years of continuous human habitation in space would 

end in 2015, and be replaced by intermittent sorties, first 

to low-Earth orbit, and then eventually to the Moon. 

The ISS is about to be completed, and its success will depend on how well it is used. This scenario enables only five 

years of ISS utilization at something less than full capability. 

While scientific and technological experiments already on 

the drawing boards may be flown on the ISS in the next five 

years, it is less likely that new ventures will have enough 

time to do so. The U. S. starts at a disadvantage in this regard relative to its international partners, since its life science and microgravity science programs are stalled because 

of budgetary pressures. Congress designated the ISS as a 

National Laboratory in 2005 to facilitate the development of 

broad capabilities in science and technology by other government agencies and non-government users, a promising 

program that is literally just getting off the ground. It is not 

likely that research will be contemplated or proposed for a 

facility that may be de-orbited before full value of that research can be realized.

There are also significant international consequences associated with this scenario. By terminating the ISS, the U.S. 

would voluntarily relinquish its unique area of unchallenged 

leadership in space. Other nations have been building satellites and launch vehicles and are now constructing humanrated launch vehicles and capsules. But no other nation can 

match the 20-year U.S. lead in space engineering, construction and operations.

Just as important, by pursuing this option, the U.S. would dismantle a successful multilateral framework for international collaboration—a framework that could be extended in the future for 

other space projects. By limiting the time that the international 

partners could realize the return on their investments, the U.S. 

would be open to the accusation that it is an inconsiderate, if not 

unreliable, partner. It is unlikely that another international collaboration as broad and deep could be developed soon to replace the 

current one. New potential partners would be more likely to seek 

less ambitious bilateral relationships. The Committee’s informal 

consultations with various foreign 

partner agencies emphasized how 

important the participation of their 

astronauts and experiments on the 

ISS have been to their space activities and to securing public support 

for their entire space programs. 

Finally, there is broader domestic 

and international public opinion 

that will not unreasonably question 

whether it is sensible to terminate 

after five years of full use a project 

that took 25 years to build.

Our ISS international partners 

issued a joint statement at a July 

2008 Heads of Agency meeting 

calling for continuation of ISS 

operations beyond 2015. Russia has declared publicly that it 

intends to continue operations 

after 2015, independent of the 

U.S., if necessary. NASA believes that this is not technically 

feasible, but the comment is illustrative of the international reaction to the current ISS plan.

Figure 4.2.3-1. Projected lifetime of major International Space Station elements indicating the need for 

recertifying many elements if the International Space Station is extended to 2020. 

Source: Review of the U.S. Human Spaceflight Plans Committee
5 6 Review of U.S. Human Spaceflight Plans Committee

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The commitment to use commercial vehicles for the ISS resupply is one of the more innovative aspects of the current 

program. The prospect of an ISS resupply market is already 

stimulating risk-taking industries to develop new launch 

vehicles and capsules. However, termination of ISS would 

abruptly end that market in 2015 after fewer than five years 

of commercial resupply operations. This may not provide 

enough opportunity for the new industries to grow to maturity, and in some cases would likely threaten the survival of 

their efforts in this area. 

The Committee estimates that the Ares I vehicle planned 

to transport humans to low-Earth orbit will not be available until two years after the ISS ceases to operate under 

the current plan. In this case, there would be several years 

with no U.S. human spaceflight activity at all. Thus, an 

achievement gap would exist in addition to the launch capability gap. 

Scenario 2: Continue ISS Operations at the Present Level 

to 2020. Extending ISS operations by five years ameliorates many of the difficulties cited above with the current 

program (Scenario 1). The U.S. would have a longer time 

to develop uses of the Station; that is, to rebuild its ISS science program; to develop the ISS National Laboratory; and 

to provide opportunities to new users. Renewal of the ISS 

would assure the existing commercial cargo contractors 

of a more secure market and might also encourage other 

financial risk-takers to invest. The international partners 

would have more time to achieve a return on their investments, and the U.S. and its partners would have the opportunity for continuing human activities in space for five 

more years.

The current level of effort, however, does not allow the ISS 

to achieve its full potential as a National Laboratory or as a 

technology testbed. The majority of the funding is devoted 

to sustaining basic operations and providing transportation (including commercial resupply and crew transport 

on Soyuz). With utilization only a modest part of the ISS 

budget, many equipment and experiment racks will remain 

unfilled, which is the case today. 

Extension beyond 2015 does bring new technical issues. 

These issues include procuring and providing spares and 

recertifying the components of the ISS. (See Figure 4.2.3-

1.) One hidden benefit of work on life extension may be 

that it provides practical experience with issues that will 

arise later in missions of exploration beyond low-Earth 

orbit. As described above, planning for life extension to 

2020 would have to begin immediately.

Scenario 3: Enrich the ISS Program and Extend 

through 2020. Since ISS utilization accounts for a relatively small portion of the planned budget, a significant enrichment of ISS utilization could be achieved with a relatively modest increase in funding. This is the basis for the 

Committee’s nominal scenario, which is described below. 

Like Scenario 2, without added funding this scenario would 

adversely affect the Constellation Program in that it consumes funds that are otherwise planned to be added to that 

effort.

A much stronger emphasis on utilization will help ameliorate one of the most intractable problems associated 

with the International Space Station: Because NASA does 

not have a compelling vision for how it will use the ISS, 

many American citizens do not have a clear idea of what 

it is for. Further, the absence of funds to support utilization of the Station causes potential users to be skeptical of 

its overall value. Even if the extension option is adopted, 

it is not clear whether it will be successful in addressing 

these concerns. Up to now, the U.S. has focused almost 

exclusively on building the ISS. Budgetary pressures 

during construction meant that inadequate attention was 

paid to how the U.S. would use the facility after it was 

completed. As one example, the funds originally to be 

used for research and technology development were reduced. The scientific research community that had hoped 

to use the ISS has largely been dispersed and will have to 

be reassembled. 

However, there remains the potential to enhance scientific 

use of the ISS. The National Research Council Space 

Studies Board has recently initiated a decadal survey of 

life and microgravity science that will identify key scientific issues and strategies for addressing them. This 

is the first decadal survey in this area, and it will bring 

the most modern scientific understanding to bear on what 

questions may be answered in the decade through 2020. 

An extended, enriched ISS program will enable more of 

the scientific opportunities identified by the survey to be 

captured.

As the nation’s newest National Laboratory, the ISS has the 

potential to further strengthen relationships among NASA, 

other federal entities and private sector leaders in the pursuit of national priorities for the advancement of science, 

technology, engineering and mathematics. The ISS National 

Laboratory should also open new paths for the exploration 

and economic development of space. The life science research community of the National Institutes of Health and 

NASA’s space station research facilitators recently met for 

the first time to allow researchers to explore the logistics of 

flying their experiments on the ISS. Enriching the ISS program would send a strong signal to these potential users.

There is another important use of the ISS that was not considered when the space station was begun in 1984 or redesigned 

in 1992: to support exploration. The Committee believes that 

the Space Station can be a valuable testbed for the life support, 

environmental, and advanced propulsion technologies, among 

others, that will be needed to send humans on missions farther 

into space. It also has the potential to help develop operational 

techniques important to exploration. Such an emphasis has the 

advantage of keeping the technology development and operational side of NASA involved in ISS utilization.

Among the most compelling considerations supporting this 

scenario are the opportunities it affords for international 

partnership. The negotiations to extend the ISS partnership 

beyond 2016 (which, under the latter two scenarios, should 

begin soon) offer the U.S. a new opportunity for geopolitical 

leadership. The ISS partnership can be enriched in a variety 

of ways: its goals may be enlarged, its membership may be 

enlarged, or both. By adding aspects of exploration beyond 
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low-Earth orbit to the goals of the ISS partnership, the partners would engage at an early stage with the U.S. in the next 

grand challenge of space exploration. The ISS agreement 

itself might serve as the basis for the broader types of agreement that will be appropriate to deep space exploration.

Since the ISS was redesigned in 1992, several nations have 

developed important new capabilities for robotic and, more 

recently, human spaceflight. Opening the ISS partnership to 

new members could engage such emerging space powers with 

the present international space community, thereby facilitating 

the exchange of plans, the sharing of financial and intellectual 

resources, and the same kind of strong working relationships 

that brought the ISS into being and that sustained it. The 

Committee’s informal consultations with current ISS partner 

agencies revealed no fundamental reluctance to adding new 

partners. However, all recommended that the integration of 

potential new partners proceed after careful discussion and in 

small steps that could be taken over time. 

FINDINGS ON THE INTERNATIONAL SPACE 

STATION (ISS)

 Extending the International Space Station: The 

return on investment to both the United States and our international partners would be significantly enhanced by an 

extension of ISS life. Not to extend its operation would 

significantly impair U.S. ability to develop and lead future 

international spaceflight partnerships. 

 ISS termination: If the ISS is to be de-orbited in early 

2016, negotiations with international partners and operational planning must begin now; additional funds must be 

added to the budget to accomplish this complex technical 

task.

 ISS utilization: If the life of the ISS is extended, a more 

robust program of science, human research and technology development would significantly increase the return on 

investment from the Station and better prepare for human 

exploration beyond low-Earth orbit. Additional funds 

would need to be provided for this purpose.

 Cargo to and from the ISS: When the Shuttle is retired, the ISS will rely on a mix of commercial and international cargo transports for provisions, resupply, maintenance and utilization. Some of these delivery systems are 

as yet unproven and could experience delays. While this 

would not place the ISS itself in jeopardy in the near term, 

it could put its utilization at risk. 

 Commercial cargo carriers: NASA’s planned transition of much of the ISS cargo resupply to the commercial sector is a positive development. Financial incentives 

should be added to those suppliers to meet their schedule 

milestones, as the ISS will be vulnerable until the relevant 

vehicles have demonstrated their operational capabilities 

and flight rates. 

 Management structure for ISS utilization: The 

benefits of continued operation of the ISS will depend 

heavily on the extent to which its management focuses on 

utilization. One possible approach would be to establish 

an independent organization that mediates between NASA 

operations managers and the broad stakeholder community of scientific, technological and commercial users. 

 International partnership in ISS: NASA’s international partners value the ISS relationship and U.S. leadership in that relationship. They further view it as a platform 

for international cooperation in exploration. 

n 4.3 THE CONSTELLATION PROGRAM

In addition to the Shuttle and the ISS, the scope of NASA 

activities the Committee was directed to examine includes 

all of the activities within the Exploration Systems Mission 

Directorate (ESMD). These include the Constellation Program, the name given by NASA to the flight development 

program for the next phase of human space exploration.

As the Committee assessed the current status and possible 

future of the Constellation Program, it reviewed the technical, budgetary and schedule challenges that the program faces today. In developing Integrated Options for the nation’s 

human spaceflight program, the Committee established as 

the baseline what it considers to be an implementable version of the Constellation Program. This baseline case is outlined in more detail in Chapter 6. 

The 2004 Vision for Space Exploration established new and 

ambitious goals for the nation’s human spaceflight program. 

The Constellation Program is NASA’s response to that Vision. The Exploration Systems Architecture Study (ESAS) 

defined the broad architecture for the program in 2005. (See 

Figure 4.3-1.) The principal program elements include: the 

Ares I launch vehicle, capable of launching astronauts to 

low-Earth orbit; the Ares V heavy-lift cargo launch vehicle, 

to send astronauts and equipment towards the Moon or other 

destinations beyond low-Earth orbit; the Orion capsule, to 

carry astronauts to low-Earth orbit and beyond; the Altair lunar lander for descent to the surface of the Moon, and ascent 

back to lunar orbit for the crew; and surface systems that 

astronauts will need to explore the lunar surface. 

Development of the first two of the elements needed, the 

Ares I and Orion, is well underway. While development of 

the Ares V has not been initiated, certain components of the 

Ares I can be expected to be common with the Ares V. A detailed review by the Committee of the two launch vehicles, 

the Ares I and Ares V, will be presented in Chapter 5. The 

Altair lander and the lunar surface systems are still in very 

early phases of design, and were discussed as part of the 

Moon First strategy in Chapter 3.

4.3.1 Orion.

The remaining principal element, Orion, consists of a spacecraft generally in the shape of the Apollo capsule, a service 

module and a launch-abort system. Orion is designed to 

operate in space for up to six months and carry six astronauts, but is currently being configured for ISS support as a 

four-person vehicle. An upgraded (Block 2) version is an-
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ticipated for travel to the Moon and beyond. Orion performance is constrained by re-entry and landing considerations 

and is also subject to limitations imposed by Ares I. It has 

undergone multiple redesign cycles in response to changing 

requirements.

The Committee examined the design and operations of 

Orion in some detail. Many concepts are possible for 

crew-exploration vehicles, and NASA clearly needs a new 

spacecraft for travel beyond low-Earth orbit. Evidence reviewed by the Committee indicates that the current Orion 

design will be acceptable for a wide variety of tasks in the 

human exploration of space. The Committee’s greatest 

concern regarding Orion is its recurring cost. The capsule 

is five meters in diameter, considerably larger and more 

massive than previous capsules (e.g., the Apollo capsule), 

and there is some indication that a smaller and lighter fourperson Orion could reduce operations costs. For example, 

such a configuration might allow landing on land rather 

than in the ocean, and it might enable simplifications in 

the (currently large and complex) launch-abort system. In 

addition, this would also increase launch margin, which 

could reduce the cost and schedule risk to the Constellation 

Program. However, a redesign of this magnitude would 

likely result in well over a year of additional development 

time and an increase of perhaps a billion dollars in cost. 

In any case, in order to provide for a sustainable program, 

every effort should be made to reduce the recurring costs 

of Orion. 

Safety is of course of primary concern in any human-rated system, and Orion, and its companion Ares I launcher, 

are designed in accordance with NASA’s latest humanrating requirements. The design includes an abort capability throughout ascent, as well as requirements to make 

loss of crew a factor of 10 less likely than at any previous 

time in human spaceflight. The ability of Ares I to meet these requirements will not be known until it has 

an established flight record, but it is 

clearly being designed to a high standard of safety and reliability. A more 

detailed discussion of human rating 

is contained in Section 5.3.4.

As part of an independent review, 

an assessment of the Orion Crew 

Vehicle “stand alone” development 

plan was conducted. The assessment 

focused on critical path elements. It 

was observed that the Orion development schedule is “back-end loaded,” 

such that designing test articles, conducting tests and producing flight 

hardware run in parallel, thus creating an extremely high schedule risk. 

For example, the Program of Record 

shows only three months between 

completion of system qualification 

(June 2014) and the planned Orion 

1 launch date (September 2014). A 

large number of technical risks also 

add to schedule uncertainty. When compared to historical programs, the most likely delay to the Orion availability approaches 18 months. Additional critical paths exist 

through ground test and flight test. 

4.3.2 Constellation Development. 

Since Constellation’s inception, the program has faced 

a mismatch between funding and program content. Even 

when the program was first announced, its timely execution 

depended on funds becoming available from the retirement 

of the Space Shuttle (in 2010) and the decommissioning of 

the ISS (in early 2016). Since those early days, the program’s long-term budget outlook has been steadily reduced 

below the level expected by NASA. As shown in Figure 

4.3.2-1, the Exploration Systems Architecture Study of 2005 

assumed the availability of a steady-state human spaceflight 

budget for exploration of about $10 billion per year. In the 

subsequent FY 2009 and FY 2010 budgets, the long-term 

projections for funding have decreased. The FY 2010 President’s Budget Submittal suggests a steady state funding of 

about $7 billion per year.

The shorter-term budget situation has had mixed impact on 

Constellation. The formal first post-ESAS budget was the 

FY 2007 budget, in which the funds available to Ares I and 

Orion were significantly lower than those anticipated during the time of ESAS. Subsequently, in the FY 2008 – FY 

2010 budgets, the funds anticipated in the out years in the 

FY 2007 budget were made available to Ares I and Orion. In 

part this has been achieved by scope changes in other NASA 

programs.

The budget outlook for the Constellation Program would 

be even bleaker under some alternate human spaceflight 

plans. Without additional funding, if the Shuttle manifest 

extends into 2011 and/or the life of the ISS is extended, 

Figure 4.3-1. The major elements of the Constellation transportation architecture showing sequence of 

operation. Source: NASA
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there will be even less funding available for Ares I and 

Orion. Further, as the Shuttle and ISS programs are 

terminated, a significant percentage of NASA’s fixed 

costs will transition to Constellation. The Committee has found that not all of those costs have been 

accounted for in the Constellation budget plan. Most 

major vehicle-development programs face technical 

challenges as a normal part of the development process, and Constellation is no exception. For example, 

as the Ares I design has matured, the rocket has grown 

in weight and various technical issues have emerged. 

Among these is the high level of vibrations induced 

by thrust oscillation in the first-stage motor. While 

significant, these can be considered to be engineering 

problems, and the Committee expects that they will be 

solved, just as the developers of Apollo successfully 

faced challenges such as a capsule fire and an unknown 

and potentially hazardous landing environment. But 

finding the solutions to Constellation’s technical problems will likely have further impact on the program’s 

cost and schedule. 

Differences between the original Constellation program planning budget and the actual implementation 

budget, coupled with technical problems that have 

been encountered on the Ares I and Orion programs, 

have produced the most significant overall impacts to 

the execution of the Constellation Program. This has 

resulted, for example, in slipping work on the Ares 

V and lunar systems well into the future and setting 

Orion’s near-term occupancy at four astronauts. 

The original 2005 schedule showed Ares I and Orion available to support the ISS in 2012, only two 

years after scheduled Shuttle retirement. The current 

schedule maintained by the Constellation Program 

now shows that date as 2015, but with a relatively low 

schedule confidence factor and little schedule slack 

Figure 4.3.2-1. Constellation Program Funding Profiles. Source: NASA

on the critical path. The Committee commissioned the Aerospace Corporation to perform 

an independent assessment of 

the technical, budgetary and 

schedule risk on the Constellation Program. The study 

methodology employed for the 

assessment of cost and schedule is substantially the same 

as described for the Integrated 

Options in Figure 6.2.3-1 of 

Chapter 6. All resulting cost 

and schedule impacts prepared 

for the Committee are formulated at the 65-percent confidence level, consistent with 

the direction NASA has given 

the Constellation Program.

The results of the analysis indicate to the Committee that, 

under the FY 2010 budget 

profile, there is likely an additional delay of at least two years, with first launch 

in 2017, and perhaps as much as four years of delay, 

with first launch in 2019. This suggests that Ares 

I and Orion will not reach ISS before the Station’s 

currently planned termination. Assuming a Shuttle 

retirement sometime in FY 2011, the length of the 

gap in which the U.S. will have no independent capability to transport astronauts into orbit will be about 

seven years.

The Constellation Program has identified measures, 

such as ongoing content reduction, deployment of 

stimulus funds to address high-risk schedule areas, 

and program management actions to mitigate major 

risks, that suggest that the first launch of Ares I and 

Orion could occur in 2017 if those measures are successful. 

The Ares V, still in conceptual design, promises to be 

an extremely capable rocket—able to lift 160 metric 

tons of cargo into low-Earth orbit. But its design, 

too, has experienced growth (and program delays) 

due to the impact of the development of other elements of Constellation. Under the FY 2010 funding 

profile, the Committee estimates that Ares V will not 

be available until the late 2020s. Under the FY 2010 

budget, the lunar landing and surface systems will 

also be delayed by over a decade, indicating that human lunar return could not occur until well into the 

2030s. 

4.3.3 Importance of Technology Development.

As currently structured, the only broad-based space 

technology program of NASA is contained within 

the Exploration Systems Mission Directorate, and is 

closely tied to the near- and mid-term needs of Constellation. Two recent reports of the National Research 

Council have examined and made recommendations to 
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FINDINGS ON ORION AND ARES I

 Orion: The Orion is intended to be a capable crew 

exploration vehicle, and the current Orion design will 

be acceptable for a wide variety of tasks in the human exploration of space. The current development 

is under considerable stress associated with schedule 

and weight margins. The primary long-term concern 

of the Committee is the recurring cost of the system.

 Ares I: Ares I is intended to be a high reliability 

launcher. When combined with the Orion and its 

launch escape system, it is expected to serve as a crew 

transporter with very high ascent safety. The Ares I is 

currently dealing with technical problems of a character not remarkable in the design of a complex system – problems that should be resolvable with commensurate cost and schedule impacts. Its ultimate 

utility is diminished by schedule delays, which cause 

a mismatch with the programs it is intended to serve.

(Other findings on the Constellation Program launch 

vehicles are in Chapter 5.)

NASA on the structure of its future space technology 

program.

The need for technology development is apparent, 

and the pursuit of a well-crafted technology program 

would be very beneficial to the longer-term human 

spaceflight program. Failure to adequately fund such 

efforts in the past has reduced the options available today. Further, substantial cost and schedule savings can 

be achieved by having the needed technologies in place 

prior to initiating engineering development activities. 

Almost invariably, to conduct such efforts in parallel is 

extremely costly.

Based on these considerations, the Committee finds 

that a robust technology-development program, funded 

in support of future human spaceflight activities, would 

not only introduce new opportunities for mission architecture but also enable reduction in the cost of human 

spaceflight. This will be discussed in Chapter 7.
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Launch to low-Earth orbit is the 

most energy-intensive and dynamic step in human space exploration. No other single propulsive maneuver, including descent 

to and ascent from the surfaces 

of the Moon or Mars, demands 

higher thrust or more energy or 

has the high aerodynamic pressure forces than a launch from 

Earth. Launch is a critical area 

for spaceflight, and two of the 

five key questions that guide 

the future plans for U.S. human 

spaceflight focus on launch to 

low-Earth orbit: the delivery of 

heavy masses to low-Earth orbit 

and beyond; and the delivery of 

crew to low-Earth orbit. 

n 5.1 EVALUATION 

METHODOLOGY FOR 

LAUNCH VEHICLES

Launch vehicles and associated ground infrastructure are key elements of the architectures that support human spaceflight missions. Launch vehicles 

are generally designed anew or adapted from existing vehicles to support a specified mission or range 

of missions. The mission definition drives the size, 

performance, production rates, reliability and safety 

requirements. This is particularly true for “cleansheet” (i.e., new) designs. For the adaptation of existing launch vehicles to new missions, greater compromise between the launch vehicle and the mission 

is often needed in order to execute the adaptation 

and thus realize the benefits sought. Primary among 

these benefits is proven safety, cost, reliability and 

performance.

The Aerospace Corporation performed for the Committee an evaluation of potential launch vehicles. 

The metrics used in evaluating the various launch 

vehicle candidates, as shown in the upper left hand 

corner of Figure 5.1-1, contain the usual cost, performance and schedule parameters, but also include 

items such as safety, operability, maturity, human rating, workforce implications, impacts on the U.S. industrial base, the development of commercial space, 

the consequences to national security space, and the 

impact on exploration and science missions. Some 

metrics could be evaluated quantitatively, such as 

cost and schedule, while others required qualitative 

assessment, such as the impact on as-yet undefined 

national security space missions. 

Launch to Low-Earth Orbit 

and Beyond

Chapter 5.0

Figure 5.1-1. Process for assessing metrics for launch vehicle evaluation. Source: Aerospace Corporation
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At a summary level, the assessment process centered around 

two evaluations. The first was to assess and modify where 

appropriate the claim for a system as submitted by the provider of that system. The second step was to represent the 

uncertainty associated with the assessment of each metric 

for each launch system. This process made it possible to 

capture cases where claims might be judged to be less than 

their stated values but with a fair degree of certainty as well 

as cases where a claim was judged well within historical 

bounds but significant uncertainty remained about the estimate. It also permitted at least a first-order comparison of 

existing vehicles with proposed vehicles—including defining the uncertainty in the comparison. A sample summary 

of these evaluations is shown in the upper right hand corner 

of Figure 5.1-1. 

In analyzing individual launch vehicles the study approach 

examined approximately 70 lower-level metrics that contributed to the 13 top-level metrics. A summary was created 

for all relevant launch systems for each mission category as 

to their ranking relative to the other launch systems capable 

of supporting that particular mission. 

n 5.2 HEAVY LIFT TO LOW-EARTH ORBIT 

AND BEYOND

The insertion of heavy payloads from Earth orbit towards 

their destination is essential for exploration beyond lowEarth orbit, and such systems significantly benefit from 

heavy lift to low-Earth orbit. The plan of the Constellation 

Program for the exploration of the Moon envisions launching about 600 metric tons (mt) per year to low-Earth orbit, 

while exploration along the Flexible Path may require somewhat less launch mass each year. NASA scenarios for the 

exploration of Mars will have comparable annual requirements. In the three years of lunar surface exploration during 

Apollo, which had a less capable lunar surface infrastructure 

than is currently planned, NASA launched over 250 mt per 

year. As a point of comparison, the ISS, assembled over the 

last decade by the Shuttle, has a mass of about 350 mt. Thus 

in the era of exploration beyond low-Earth orbit, we will 

launch to low-Earth orbit a mass comparable to that of the 

entire ISS every year.

The key decision for heavy lift to low-Earth orbit is: on what 

should the next heavy-lift launch vehicle be based? The 

Committee examined five candidates for heavy lift, with 

their estimated launch mass to low-Earth orbit shown in the 

right-most five bars of Figure 5.2-1. In the end, to simplify 

the considerations, the Committee treated the five launchers 

in the four classes summarized in Figure 5.2-2: the currently 

planned Ares I + Ares V architecture; the Ares V Lite (used 

in a dual mode for lunar missions): a Shuttle-derived vehicle; and a “super-heavy” launcher derived from Evolved 

Expendable Launch Vehicle (EELV) heritage. The Shuttlederived class was used to represent both in-line and sidemount vehicles, each of which will be discussed in more 

detail below.

5.2.1 The Need for 

Heavy Lift

First, the Committee examined the question: do we need 

a heavy-lift capability? While 

it is obvious that the ability to 

inject massive spacecraft away 

from low-Earth orbit is vital for 

exploration, there is some question as to the smallest practical 

size of the launcher that will be 

used to carry cargo to low-Earth 

orbit. The Committee reviewed 

the issue of whether exploration beyond low-Earth orbit 

will require a “super heavy-lift” 

launch vehicle (i.e., larger than 

the current “heavy” EELVs, 

Figure 5.2-2. Heavy Launch Vehicle Options indicating the approximate launch mass to low-Earth orbit, and the 

engines of the first stage (LOX is liquid oxygen, LH is liquid hydrogen, RP-1 is a hydrocarbon fuel, SRB is a Solid Rocket 

Booster derived from the Shuttle system. See text for discussion of engines.)

Source: Review of U.S. Human Spaceflight Committee

Figure 5.2-1. Approximate payload mass launched by various launch 

vehicles to a 28.5 degree inclination low-Earth orbit. Source: Review of

U.S. Human Spaceflight Plans Committee
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whose mass to low-Earth orbit is in the 20-25 mt range), and 

concluded that it will. However, the rationale for this decision 

is subtler than usually thought, and hinges on three factors: the 

size and mass capability of the launcher and of the entire U.S. 

launch capacity; in-space refueling capability; and the launch 

reliability expected for a given mission.

No one knows for certain the mass or dimensions of the largest 

piece of hardware that will be required for future exploration 

missions. It will likely be larger than 25 metric tons (mt) in 

mass, and may be larger than the approximately five-meterdiameter fairing of the largest current launchers. The largest 

single element in the current NASA plans that will be launched 

to low-Earth orbit is the Earth Departure Stage (EDS). Not 

counting its approximately 60 mt of payload, the EDS arrives 

in low-Earth orbit on a standard lunar mission with a mass of 

about 119 mt, of which about 94 mt is fuel, and only 25 mt is 

dry mass. In the absence of in-space refueling, the U.S. human spaceflight program will require a heavy-lift launcher of 

significantly greater than 25 mt capability to launch the EDS 

and its fuel. 

However the picture changes significantly if in-space refueling is used. All of the heavy-lift vehicles listed in Figure 5.2-

2 use an EDS to lift the specified payload mass to low-Earth 

orbit. In the conventional scheme, the EDS burns some of 

its fuel on the way to orbit, and it arrives in low-Earth orbit 

partially full. The remainder of the fuel is expended in injecting the payload toward its destination beyond low-Earth 

orbit. The alternative is to refuel the EDS in low-Earth orbit 

from either a dedicated tanker or a fuel depot. This allows 

more mass to be injected from the Earth with a given EDS. 

Studies commissioned by the Committee found that in-space 

refueling could increase by at least two to three times the injection capability from low-Earth orbit of a launcher system, 

and in some cases more. 

Thus, an in-space refueling capability would make larger 

super-heavy lift vehicles even more capable, and would 

enable smaller ones to inject from low-Earth orbit a mass 

comparable to what larger 

launchers can do without inspace refueling. (See Figure 

5.2.1-1.) In fact, the larger elements launched to low-Earth 

orbit tend to be propulsion stages, and these are usually about 

80 percent fuel by mass. If 

there were the capability to fuel 

propulsion stages in space, the 

single-largest mass launched 

would be considerably less than 

in the absence of in-space refueling. The mass that must be 

launched to low-Earth orbit in 

the current NASA plan, without 

its fuel on board, is in the range 

of 25 to 40 mt, setting a notional lower limit on the size of the 

super heavy-lift launch vehicle 

if refueling is available.

As an additional benefit of in-space refueling, the potential 

government-guaranteed market for fuel in low-Earth orbit 

would create a stimulus to the commercial launch industry 

beyond the current ISS commercial cargo-services market.

The Committee examined the current concepts for inspace refueling. There are essentially two. In the simpler 

one, a single tanker performs a rendezvous and docking with the EDS on orbit, transfers fuel and separates, 

much like an airborne tanker refuels an aircraft. In a more 

evolved concept, many tankers rendezvous and transfer 

fuel to an in-space depot. (See Figure 5.2.1-2.) Then 

at a later time, the EDS docks with the depot, fuels, and 

departs Earth orbit. The Committee found both of these 

concepts feasible with current technology, but in need of 

significant further engineering development and in-space 

demonstration before they could be included in a baseline design. This would require engineering effort, and at 

Figure 5.2.1-1. Mass injected away from LEO towards the Moon (on Trans-Lunar Injection) with and without in-space 

refueling. Source: Review of U.S. Human Spaceflight Committee

Figure 5.2.1-2. Artist’s concept of a fuel depot servicing an Earth Departure 

Stage. Source: Boeing
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some development investment, long-term life-cycle savings may be obtained.

The concept of in-space refueling introduces the idea of critical launches and less critical launches in any given mission. 

Using the lunar mission with crew as a reference, the critical launches would carry the Orion, Altair and EDS to lowEarth orbit. Depending on launch vehicle capacity this could 

be accomplished on one flight (as it was in Apollo), two, or 

even three launches. Less critical missions would be the ones 

that bring fuel to low-Earth orbit. The Committee commissioned a detailed analysis of the reliability of missions that 

would require multiple launches of critical and less critical 

payloads. It found that achieving reasonable probability of 

mission success requires either 90+ days of on-orbit life for 

the EDS, or a depot, and that at most three critical launches 

should be employed. Since it is very constraining to balance 

mission components to always partition equally between 

launches, this strongly favors a minimum heavy-lift capacity 

of roughly 50 mt that allows the flexibility to lift two “dry” 

exploration elements on a single launch. 

Another way to view the requirements of heavy lift is to consider the recurring cost to NASA of using a significant fraction of the yearly existing and planned U.S. launch capability after the Shuttle retires. At reasonable production rates 

of the existing EELV heavy launch vehicles, mid-size EELVs, new commercial vehicles, and the Ares I, much if not 

all of the excess capability that exists in the U.S. production 

system would be used launching 400 to 600 mt to low-Earth 

orbit, and it would be an expensive way to accomplish this.

The Committee finds that exploration would benefit from 

the development of a heavy-lift capability to enable voyages 

beyond low-Earth orbit. This might be supplemented by the 

development of an in-space refueling capability. In-space 

refueling has great potential benefits, but needs development 

and demonstration before being incorporated into a baseline 

design. 

Using a launch system with more than three critical launches 

begins to cause unacceptably low mission launch reliability. 

Therefore a prudent strategy would be to use launch vehicles 

that allow the completion of a lunar mission with no more 

than three launches without refueling. This would imply a 

launch mass to low-Earth orbit of at least 65 to 70 mt based 

on current NASA lunar plans. Vehicles in the range up to 

about 100 mt will require in-space refueling for more demanding missions. Vehicle above this launch capability will 

be enhanced by in-space refueling, but will not require it. 

When in-space refueling is developed, any of these launchers will become more capable.

The development of such a heavy-lift vehicle would have 

other benefits. It would allow large scientific observatories to be launched, potentially enabling them to have optics larger than the current five-meter fairing sizes will allow. More capable deep-space science missions could be 

mounted, allowing faster or more extensive exploration of 

the outer solar system. Heavy lift may also provide benefit 

in national security space applications.

5.2.2 The Choices for Heavy Lift

The Committee examined the four choices for heavy lift outlined in Figure 5.2-1 and Figure 5.2-2, all of which pose different heritage, capability, maturity and organizational ramifications. They will be discussed with reference to the use on 

a typical lunar mission and Flexible Path mission.

Ares V. The Ares V is used with a human rated Ares I for lunar missions – 

the so-called 1.5 launch architecture. 

The Ares I launches the Orion, which 

docks in low-Earth orbit with the Altair lander and EDS launched on the 

Ares V. The Orion and Altair departs 

towards the Moon, propelled by the 

EDS. (See Figure 3.4.2-1.) The Ares I 

rocket is currently under development 

by the Constellation program, and has 

a great deal of commonality with the 

Ares V. This version of the Ares V 

(in contrast with the Ares V Lite discussed below) is the most capable of 

the launch vehicle alternatives under 

study, with a payload to low-Earth orbit of about 160 mt. (See Figure 5.2.2-

1.) When used in conjunction with the 

Ares I, the combined payload to lowEarth orbit is about 185 mt. With an 

appropriately designed lunar lander, 

one Ares I and one Ares V land about 2 mt of cargo on 

the lunar surface on a human mission, and about 14 mt 

reaches the lunar surface on a cargo-only mission with a 

single Ares V launch.

Both the Ares I and Ares V use Solid Rocket Boosters 

(SRBs) – a five-segment SRB in the Ares I, and a five-anda-half segment SRB in the Ares V. The Ares V first stage 

uses six engines from the RS-68 family. The engines are 

mounted on the bottom of a 10-meter diameter tank. The 

second or Earth Departure Stage is based on the J2-X engine, which the Ares V shares in common with the Ares I. 

The advanced RS-68 rocket engine of the core is a modification of the RS-68 engines used on the existing Delta IV 

launch vehicles. Certain changes to the RS-68 for use in 

the Ares family are anticipated. These include upgrades to 

reduce hydrogen flow at startup, and for extended operation in the more aggressive Ares V thermal environment. 

The J-2X rocket engine is a modification of the J-2 engines 

used on the Saturn V program. The use of the Ares I as 

a means of crew transport to low-Earth orbit will be discussed in Section 5.3.

Ares V Lite. The Ares V Lite is a slightly lower performance variant of the Ares V, with a low-Earth orbit payload of about 140 mt, but with the same essential configuration as the Ares V. However, in this option it would be 

human rated, as it is used for crew launch with the Orion. 

It uses five-segment SRBs (already under development 

for the Ares I), and five core engines, a derivative of the 

RS-68, the engine used on the Delta IV Heavy EELV. It 

would use a slight variant of the same EDS as the Ares V, 

with the same J2-X engine. For lunar missions, the Ares 

Figure 5.2.2-1. Ares V. 

Source: NASA
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V Lite is used in the “dual mode.” The Orion and Altair 

are launched on separate Ares V flights, and they dock 

either in Earth or Moon orbit, depending on the mission 

mode eventually chosen. 

With a combined payload to low-Earth orbit for the dual 

launches of about 280 mt, this architecture would enjoy 

considerable payload margin that could provide significant 

enhancement in mission robustness for lunar missions. With 

an appropriately designed lunar lander, this system lands 

about 7 mt of cargo on the lunar surface on a crewed mission. With a single Ares V Lite launch, the same lander can 

deliver about 14 mt on a cargo-only mission.

When used on Flexible Path missions, a single Ares V Lite 

and EDS, in combination with the Orion and an in-space 

habitat, are able to support a visit to the Lagrange points 

without refueling. In order to reach near-Earth objects and 

beyond, in-space refueling (or alternatively multiple Ares V 

Lite launches) is necessary.

Shuttle-Derived Launchers. 

The Committee examined the 

Shuttle-derived family, consisting 

of in-line and side-mount vehicles 

substantially derived from the 

Shuttle. These are all characterized by four-segment solid rocket 

boosters, Space Shuttle Main Engines (or their RS-25E expendable 

derivatives), and 8.3-meter-diameter external tanks, as used on the 

Space Shuttle. This class actually 

comprises a family of possible vehicles. 

Shuttle Derived Side-Mount 

Launcher. On one end of the spectrum is the side-mount launcher 

that is most directly derived from 

the Shuttle. (See Figure 5.2.2-2.) It 

replaces the Shuttle orbiter with an 

expendable side-mounted payload 

carrier that contains both a clamshell-type payload shroud 

and a propulsion system consisting of three Space Shuttle 

Main Engines (SSME). It uses the exact same tank and SRB 

configuration as the Shuttle. It would likely carry an EDS 

with a J2-X engine internal to the payload bay. This would 

be the smallest development effort possible within the family. Depending on details of design, a side-mount launcher 

with an EDS can lift 90 to slightly more than 100 mt to lowEarth orbit.

Shuttle-Derived Inline Launcher. At the other end of the 

spectrum is an inline vehicle, such as the Jupiter 241, with 

four SSMEs mounted at the bottom of a redesigned tank/

thrust structure, and with an EDS atop the tank. (See Figure 

5.2.2-3.) Once the existing stock of SSME engines is depleted, this configuration will use an expendable version of 

the SSME, the RS-25E. The upper stage uses liquid oxygen 

and liquid hydrogen as propellants, with a single J-2X rocket 

engine. The Committee evaluated the smaller Jupiter 130 

that does not have an EDS, but used 

the more capable Jupiter 241 as the 

basis of comparison, which has a 

launch capacity in the range of 100 

to 110 mt to low-Earth orbit. 

In a lunar exploration scenario, it is 

assumed that three Shuttle-derived 

launchers of a nominal 110 mt capability would be used for a crewed 

mission. A single launcher would 

be used for lunar cargo missions. 

When used in conjunction with a 

lunar lander designed for this size 

vehicle, this system lands about 5 

mt of cargo on a crew mission. A 

single-launch cargo mission lands 

less than 5 mt of cargo on the lunar 

surface. However, a single launch 

cargo mission, enhanced by the use 

of in-space refueling, increases the 

cargo mass landed on the lunar surface to more than 20 mt. 

For Flexible Path missions, two Shuttle-derived launchers, 

combined with in-space refueling of an EDS, are required to 

propel the Orion and in-space habitat to the Lagrange points, 

near-Earth objects and beyond.

While the Committee did not examine the technical trade 

between the side-mount and inline variants in detail, it 

observes that the side-mount variant is considered an inherently less safe arrangement if crew are to be carried, 

and is more limited in its growth potential.

EELV Heritage Super-Heavy. The EELV heritage superheavy launchers represent a potential family of vehicles 

derived from the current Evolved Expendable Launch 

Vehicles heritage. They are distinguished technically 

from the NASA heritage vehicle by their use of liquid 

booster (rather than the solid rocket boosters) and secondarily by a hydrocarbon (RP-1) fueled rocket in the 

first stage core. (See Figure 

5.2.2-4.) The upgraded EELV 

systems would have a core 

vehicle that would, by itself, 

have a launch capability to 

low-Earth orbit in the range 

of 30 to 35 mt. Using a “super-heavy” variant that would 

have a core and two boosters 

of the same basic design, and 

when used in conjunction 

with an upgraded common hydrogen/oxygen upper stage, it 

is likely to have a maximum 

payload to low-Earth orbit in 

the range of 75 mt. This exceeds the nominal minimum 

for a heavy lifter useful for 

exploration as defined above. 

A representative of this category of launchers is the Atlas 

5 Phase 2 Heavy.

Figure 5.2.2-2. Shuttle-Derived 

Sidemount Launcher. 

Source: NASA

Figure 5.2.2-3. Jupiter 241. 

Source: NASA

Figure 5.2.2-4. EELV Heritage 

Super Heavy Launcher.

Source: NASA
6 8 Review of U.S. Human Spaceflight Plans Committee

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The EELV super-heavy uses two RD-180 rocket engines on 

each of the core and two boosters. The RD-180 engine has a 

long history of successful launches in Russia and in the U.S. 

on the Atlas V family of launch vehicles. The upper stage 

uses liquid oxygen and liquid hydrogen as propellant, with 

four RL10 rocket engines. The RL10 family of engines has 

a long history of successful launches on programs including 

the Titan, Atlas and Delta families of vehicles. The Atlas 

Phase 2 is a proposed follow-on of the EELV program, with 

larger, five-meter diameter, stages, manufactured using the 

existing five-meter production facilities that currently produce the Delta IV core stages. When used in conjunction 

with Flexible Path missions, the EELV-heritage launcher 

and EDS send the Orion and in-space habitat towards the 

Lagrange points, near-Earth objects and beyond, with two 

launches plus in-space refueling.

Developmental considerations. Any of these launcher 

options will entail a substantial development project. The 

Committee observes that throughout the history of launcher 

development, and particularly for the Shuttle, the aim has 

frequently been to design for ultimate performance, often 

at the cost of reliability and operational efficiency. In particular, NASA’s design culture has repeatedly focused on 

maximizing performance at minimum development cost, 

generally resulting in high operational and lifecycle costs. 

While performance is important in launchers, good performance margins and associated robustness are also desirable, 

and can lead to lower life-cycle costs. A shift in NASA design culture toward design for minimum life-cycle cost, accompanied by robustness and adequate margins, will allow 

NASA programs to be more sustainable.

There is one additional consideration regarding heavy lift capability. In all missions beyond low-Earth orbit, there will 

be a need for one or two additional propulsive maneuvers 

far from Earth. For example, in visiting the Moon, a burn 

is necessary to enter lunar orbit, and another to leave. When 

visiting a near-Earth object, a burn is necessary to decelerate 

to rendezvous with the object, and then a second to return to 

Earth. Exploration will require a long-duration in-space restartable stage. This would become a building block of exploration propulsion systems, potentially including the lunar 

descent stage.

FINDINGS ON LAUNCH TO LOW-EARTH 

ORBIT AND BEYOND

The Need for Heavy-Lift: A heavy-lift launch capability to low-Earth orbit, combined with the ability to 

inject heavy payloads away from the Earth, is beneficial 

to exploration, and will also be useful to the national security space and scientific communities. The Committee 

reviewed the Ares family of launchers, Shuttle-derived 

vehicles, and launchers derived from the EELV family. 

Each approach has advantages and disadvantages, trading 

capability, lifecycle costs, operational complexity and the 

“way of doing business” within the program and NASA. 

In-Space Refueling: The ability to add fuel to an Earthdeparture stage, either from in-space docking with a tanker 

or from a depot, is of significant potential benefit to the inspace transportation system beyond low-Earth orbit. The 

technology for in-space refueling is available, but a further development and demonstration program is required. 

Therefore a prudent approach is to develop a heavy-lift 

launch system with sufficient capabilities for early missions, which would later be enhanced by in-space refueling when it becomes available.

Sustainability of Operations of U.S. Launch Systems:

NASA’s design culture emphasizes maximizing performance at minimum development cost, repeatedly resulting 

in high operational and lifecycle costs. A shift in NASA 

design culture toward design for minimum discounted 

life-cycle cost, accompanied by robustness and adequate 

margins, will allow NASA programs to be more sustainable.

In-space Propulsion: For almost all foreseeable missions beyond low-Earth orbit, there is a need for one or 

two propulsive maneuvers, often after weeks or months 

in space. Efficient engines and stages with high-reliability 

restart capability will need to be developed.

n 5.3 CREW LAUNCH TO LOW-EARTH 

ORBIT

Among the most safety critical aspects of human spaceflight 

is the delivery and return of crew to and from low-Earth 

orbit. The fourth key question examined by the Committee 

is: how should U.S. crew be transported to low-Earth orbit? There are two choices for transporting U.S. crews to 

and from low-Earth orbit that emerged from the work of the 

Committee: a government-provided and operated system, 

and a commercially provided crew-delivery service. This 

discussion assumes that the Orion vehicle will be the primary U.S. capsule for crew transportation beyond low-Earth 

orbit and re-entry into the Earth’s atmosphere upon return 

from those voyages.

5.3.1 Ares I plus Orion: Government-Provided 

Crew to Low-Earth Orbit.

The current NASA plan for crew transport to low-Earth 

orbit—comprising the Ares I launch vehicle and the Orion 

crew capsule—was selected in 2005 as part of the ESAS 

study based in part on the anticipated availability and projected crew safety considerations of the Ares I and Orion. At 

the time of ESAS, estimates showed that Ares I and Orion 

would be available for crew transport service to the ISS by 

2012. The date projected by the Constellation program is 

now 2015. As the plan evolved after 2005, the Ares I developed increasing commonality with the Ares V, providing 

architectural synergy and reducing development costs of the 

family. 

Ares I: The Ares I launch vehicle currently consists of a 

single five-segment solid rocket booster as the first stage and 

a liquid-fueled upper stage. (See Figure 5.3.1-1.) The five-
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segment SRB is a modification to the 

existing Space Shuttle SRBs. The upper stage uses liquid oxygen and liquid 

hydrogen as propellants, with a single 

J-2X rocket engine. The J-2X rocket 

engine is a modification of the J-2 engines used on the Saturn V program.

In its selection of a crew launch system, ESAS correctly placed a very high 

premium on crew safety, and the Ares 

I was selected because of its potential 

delivering at least ten times the level of 

crew safety as the current Shuttle. The 

launch vehicle configuration is one 

that best allows for crew escape in the 

event of a launch failure. The capsule 

is mounted at the top of the stack, and 

has an independent launch escape system. The track record of demonstrated 

high reliability of the SRB suggests a 

low likelihood of first stage failure on 

ascent.

Under the budget profile NASA leadership anticipated in 

2005, estimates showed that the Ares I could be developed 

by the early to mid part of the decade, and the Ares V could 

be developed by the late 2010s. It was thought that the Ares 

I would have lower operating cost when visiting the ISS than 

other alternatives, and would produce a lower operating cost 

of the entire system when joint operations of the Ares I and 

Ares V were begun. 

Additionally the development approach of engaging many 

NASA employees in the design and testing of the Ares I 

would allow the NASA workforce, which has not developed 

a new rocket for over 20 years, to gain experience on the 

relatively simpler Ares I rocket before beginning the development of the more complex Ares V. 

5.3.2 Alternatives to Government-Provided 

Crew Access to Low-Earth Orbit. 

The Committee considered several alternatives to Ares I and 

Orion, including:

• A longer-term reliance on international (currently Russian) crew transport services

• The human rating of an existing EELV for launching 

the Orion 

• The development of commercial crew transport services

• The use of a heavy-lift vehicle to launch the Orion 

While the Committee found interim reliance on international crew transport services acceptable, it also found that an 

important part of sustained U.S. leadership in space is the 

operation of our own domestic crew launch capability. This 

closed out the first alternative. The Committee next examined a NASA-commissioned study by the Aerospace Corporation on the feasibility and 

cost of human-rating an EELV, 

the Delta IV Heavy, for use as 

the launcher for Orion.

Delta IV HLV: The Delta IV 

Heavy Launch Vehicle consists 

of two liquid-fueled strap-on 

boosters, a liquid-fueled first 

stage, and a liquid-fueled upper stage. The two strap-ons 

and the core stage are very 

similar and use liquid oxygen 

and liquid hydrogen as propellants and a single RS-68-family 

rocket engine on each of the 

three stages. The independent 

study found that launch of Orion to low-Earth orbit did not 

require an upper stage, as the 

spacecraft could provide the 

necessary impulse. The Delta 

IV HLV is a variant of one of 

the EELVs that has launched 

successfully many times. 

While launch of the Orion on the Delta IV HLV was found 

to be technically feasible, it requires some modification 

of the current launcher, and was comparable in cost and 

schedule to simply continuing with the development of 

the Ares I. When the Committee factored in the carrying 

cost of the NASA infrastructure that would be maintained 

if any NASA-heritage heavy launcher would eventually 

be developed (Ares V in any variant or a more directly 

Shuttle-derived heavy launcher), any cost savings that 

might have occurred due to using an EELV to launch the 

Orion were lost. Using the EELV for launch of Orion 

would only make sense if it were coupled with the development of an EELV-heritage super-heavy vehicle for 

cargo launch. Except in this case, this analysis closed out 

the second option.

5.3.3 Commercial Services to Transport Crew to 

Low-Earth Orbit

Having eliminated the long-term international supply option and the EELV option for all but the EELV-heritage 

super-heavy choice for heavy lift, the remaining possible 

choices, besides Ares I, were to utilize commercial crew 

services or use the heavy-lift vehicle as a crew launcher. 

As the nation moves from the complex, reusable Shuttle 

back to a simpler, smaller capsule, it is an appropriate 

time to consider turning this transport function over to 

the commercial sector. There is broad policy support for 

this approach, from both Congressional legislation and 

Presidential policy (See Figure iii.), and one of the four 

main charges given to the Committee by the Office of Science & Technology Policy in its Statement of Task was to 

“Stimulate commercial spaceflight capability.” This section considers the technical feasibility of a commercial 

service, safety issues, financial implications, programmatic risks, and acquisition strategy.

Figure 5.3.1-1. Ares I. 

Source: NASA Figure 5.3.2-1. Delta IV – HLV. 

Source: NASA
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Technical Feasibility of Commercial Transport Services for 

Crew. The Committee examined the technical feasibility of 

utilizing a commercial service to transport crew to low-Earth 

orbit. First, it is a statement of fact that all of the U.S. crew 

launch systems built to date have been built by industry for 

NASA. The system under contemplation is not much more 

complex than a modern Gemini, which was built by U.S. 

industry over 40 years ago. It would consist of a three- or 

four-person crew taxi, launched on a rocket with a launch 

escape system. It would have an on-orbit life independent 

of the ISS of only weeks, but potentially be storable at the 

ISS for months. Such a vehicle would re-enter the Earth’s 

atmosphere from the speed of orbital flight, rather than the 

significantly higher speed for which Orion is designed. Its 

smaller size makes possible the option of landing on land, 

potentially reducing operations cost when compared to a sea 

landing. 

Recently, several aerospace companies began developing 

new rockets and on-orbit vehicles as part of the commercial 

cargo delivery program. Several other U.S. companies are 

contemplating orbital passenger flight. There is little doubt 

that the U.S. aerospace industry, from historical builders of 

human spacecraft to the new entrants, has the technical capability to build and operate a crew taxi to low-Earth orbit. 

NASA’s Role in Safety and Mission Assurance. The Committee treated the safety of crew vehicles as the sine qua non

of the human spaceflight program, and would not suggest 

that a commercial service be provided for transportation of 

NASA crew if NASA could not be convinced that it was substantially safe. The critical question is: can a simple capsule 

with a launch escape system, operating on a high-reliability 

liquid booster, be made safer than the Shuttle, and comparably as safe as Ares I plus Orion? An important part of this 

analysis rests on the reliability of the launcher. Thus, commercial crew launchers based on high-reliability vehicles 

that already have significant flight heritage, or will develop 

flight experience soon, would be more obvious candidates as 

a crew launcher. Ares I has a heritage that traces to the use 

of the SRBs on the Shuttle, but other potential crew launchers can also trace their lineage to significant flight heritage. 

Given the history of human spaceflight, putting commercial 

crew transport to space in the critical path of any scenario 

represents a major shift in policy. As will be discussed in 

Section 5.4.2., the Committee reviewed convincing evidence of the value of independent oversight in the mission 

assurance of launchers, and would envision a strong NASA 

oversight role in assuring commercial vehicle safety. The 

challenge of developing a safe and reliable commercial capability for crew transport will require devoting government 

funds to “buy down” a significant amount of the existing uncertainty. Whatever the particulars of this risk removal process, it will take an appreciable period of time and require 

the application of thorough, independent mission-assurance 

practices. A critical aspect of this exercise will be confirming the root cause and adequacy of correction of any failures or anomalies encountered in the development test program. Thus, the Committee views any commercial program 

of crew transport to ISS as involving a strong, independent 

mission assurance role for NASA.

The Committee identified elements of a plan that would lead 

to the creation of a commercial service for crew transport, 

building on NASA incentives and guarantees. This included 

an assessment of the financial aspects and benefits of commercial crew services, the programmatic risks of relying on 

commercial crew services and potential mitigation strategies, and an approach to engaging the commercial community in this program.

Financial Aspects of the Commercial Crew Services. The 

Committee engaged in a two-step process for assessing the 

potential financial benefit of commercial services for crew 

transport. This involved both estimating the cost to develop 

and operate the system, and then determining what fraction of 

this cost NASA would likely have to provide as an incentive 

to industry to enter into this venture.

During its fact-finding process, the Committee received proprietary information from five different companies interested 

in the provision of commercial crew transportation services to 

low-Earth orbit. These included large and small companies, 

some of which have previously developed crew systems for 

NASA. The Committee also received input from prospective 

customers stating that there is a market for commercial crew 

transportation to low-Earth orbit for non-NASA purposes if 

the price is low enough and safety robust enough, and from 

prospective providers stating that it is technically possible to 

provide a commercially viable price on a marginal cost basis, 

given a developed system. None of the input suggested that 

at the price obtainable for a capsule-plus-expendable-launchvehicle system, the market was sufficient to provide a return 

on the investment of the initial capsule development. In other 

words, if a capsule is developed that meets commercial needs, 

there will be customers to share operating costs with NASA, 

but unless NASA creates significant incentives for the development of the capsule, the service is unlikely to be developed 

on a purely commercial basis.

The Committee then estimated the cost to NASA of creating 

an incentive for industry to develop the commercial transport 

capability for crew. This would probably be a significant fraction, but not the entirety of the cost of such a development. 

Given a properly structured procurement, estimates the Committee received from potential providers for the price of reaching initial demonstration flight of a crew-taxi capsule ranged 

from $300 million to $1.5 billion. For estimating purposes, 

the Committee assumed that three contracts were initiated, 

and one competitor subsequently dropped out, suggesting an 

expected cost to NASA of between $2 billion and $2.5 billion. 

In addition, the Committee believes that if a commercial crew 

program is pursued, NASA should make available to bidders 

a suitable version of an existing booster with a demonstrated 

track record of successful flight, adding to the program cost. 

The best preliminary estimate of the Committee was about a 

$3 billion program for the fraction of the design, development, 

test, and evaluation (DDT&E) effort that would be borne by 

NASA. After multiplying by the historical growth factors and 

other multipliers associated with 65 percent confidence estimating (as will be discussed in Section 6.3), the cost carried 

in the Committee’s final estimate of the cost of the program to 

NASA is about $5 billion. 
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Comparing the scope of providing a commercial crew capability to the cost of historical programs offers a sanity check. 

In the existing COTS A-C contracts, two commercial suppliers have received or invested about $400-$500 million 

for the development of a new launch vehicle and unmanned 

spacecraft. Gemini is the closest historical program in scope 

to the envisioned commercial crew taxi. In about four years 

in the early- to mid-1960s, NASA and industry human-rated 

the Titan II (which required 39 months), and designed and 

tested a capsule. In GDP-inflator-corrected FY 2009 dollars, the DDT&E cost of this program was about $2.5-3 billion, depending on the accounting for test flights. These two 

comparatives tend to support the estimate that the program 

can be viable with a $5 billion stimulus from NASA.

The Committee considered several other factors that would 

support this estimate of the incentive cost to NASA. If this 

is to be a commercial venture, at least some commercial 

capital must be at risk. Alternate sources of capital, including private and corporate investment, would be expected. 

Next, the Committee considered the cost associated with the 

development of a relatively simpler launcher and capsule 

designed only as a low-Earth orbit crew taxi in comparison 

with those associated with the far more capable Ares I and 

Orion. Additionally, the Committee heard many argue that 

economic efficiencies could be found by striking a better balance between the legitimate need for a NASA quality assurance and safety process on one hand, and allowing industry 

to execute design and development efficiently on the other. 

Significantly, the Committee considered the fact that some 

development costs, and a larger fraction of operating costs 

of a commercial crew service to low-Earth orbit could be 

amortized over other markets and customers. This is more 

obvious for the launcher, which potentially could also be 

used for the existing markets of ISS cargo to low-Earth orbit, 

science and national security space satellite missions, and 

commercial satellite launches. In the future the commercial 

booster used for crew might also launch fuel to low-Earth 

orbit for in-space refueling, and it might carry additional 

non-NASA crew flights. The non-NASA markets and customers for the capsule are less easily quantified. It is possible that other governments would procure crew launch to 

ISS from a U.S. commercial provider, and that private travel 

to low-Earth orbit could be more common by the latter part 

of the decade. Note that if there were only one non-NASA 

flight of this system per year, it would reduce the NASA 

share of the fixed recurring cost by 33 percent.

It was estimated by the Committee that under the “lessconstrained budget” to be discussed in Chapter 6, the commercial crew launch service could be in place by 2016. Estimates from providers ranged from three years to five years 

from the present. Assuming a year for program re-alignment, this would produce a start in early FY 2011. Using the 

upper end of the estimated range, a capability in 2016 could 

be estimated with reasonable confidence.

Programmatic Risks of Commercial Crew to LowEarth Orbit and Potential Mitigations. The Committee recognizes that the development of commercial services 

to transport crew come with significant programmatic risks. 

Among these are that the development of this capability 

will distract current potential providers from the near-term 

goal of successfully developing commercial cargo capability. Second, the commercial community may fail to deliver 

a crew capability in mid-program, and the task would revert 

to NASA. This could be caused by either a technical failure 

or a business failure—a failure to obtain financing, changes 

in markets or key suppliers, re-alignment of business priorities, or another non-technical reason. Either type of failure 

would require NASA intervention, and the possibility that 

NASA would either have to operate the system, or fall back 

to an alternative. 

While there are many potential benefits of commercial services that transport crew to low-Earth orbit, there are simply too many risks at the present time not to have a viable 

fallback option for risk mitigation. The Committee contemplated several alternatives, including continuing to rely on 

international providers (likely available, but not consistent 

with the long-term need for U.S. access as part of its leadership in space), and continuing the Ares I program in parallel 

(prohibitive in terms of cost). The Committee also considered the possibility of putting the Ares I program on “warm 

hold,” ready for a possible restart, while continuing the development of the five-segment SRB and the J2-X, which are 

common to the Ares V. In the end, the Committee thought 

that the most cost-effective fallback option that would move 

NASA most rapidly toward exploration is to continue to 

develop the Orion, and move as quickly as possible to the 

development of a human-ratable heavy lift vehicle. (See the 

discussion in Section 5.3.4 on human rating.) The first stage 

of any of the heavy-lift launchers under consideration would 

be more than capable of launching an Orion to low-Earth 

orbit. In the best case, the heavy-lift vehicles themselves 

would not be available until the beginning of the 2020s, but 

the first stage or core could be accelerated, perhaps by a year 

or two. In this case, the core heavy human-rated launcher 

would arrive only a few years later than an Ares I under the 

less-constrained budget scenarios. 

The details of the preferred fallback option are best left to 

NASA, but the question is clear. Assume that emphasis will 

be placed on building the heavy lifter as quickly as possible, 

and assume that commercial services for crew transportation to low-Earth orbit will be started in development, and 

may fail to materialize. What variant of the heavy launcher 

can be identified that could be developed quickly and at 

small marginal cost in the future if needed to transport Orion 

and crew to low-Earth orbit? A desirable feature is that the 

preparation for the development of this variant would have 

the minimum impact on the construction of the heavy-lift 

vehicle itself.

Engaging the Commercial Community in Crew Transport Services. The potential providers of capsules emphasized that the nature of the acquisition of these services 

is critical; to be commercially viable, low operating cost is 

essential, and to obtain that cost, the requirements for the 

capsule need to be as few as is essential and stable. Several providers gave anecdotal examples where NASA programs suffered from significant “requirements creep,” and 

emphasized the need for a more commercial-type procure-
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ment, where any changes to work scope would be matters 

for mutual negotiation, rather than one-sided impositions by 

NASA. 

The Committee envisions a new competition for this service, in which both large and small companies are invited 

to participate. Several potential providers should be funded 

through some initial development milestones measuring 

tangible progress, and incrementally incentivized. It is crucial to the success of the program that multiple providers be 

carried through to operational service. It is the pressure of 

competition that provides the drive for low operating cost. 

Assurances of a market would need to be offered by the government. By creating a third market for commercial launch 

services (cargo to ISS, fuel to low-Earth orbit, and crew to 

low-Earth orbit), it is possible that the efficiencies associated with increased production runs and more frequent operations will appear.

5.3.4 Human Rating of Launchers

The history of human rating U.S. launch vehicles can be 

traced to the Atlas and ICBM Titan usage in the Mercury 

and Gemini programs. The purpose of human rating was, 

and is, to assure that safety levels are appropriate for human 

flight. Crew safety was addressed in these earlier programs 

primarily by adding a crew escape system. The reliability of 

these launch vehicles was addressed by eliminating known 

design weaknesses, adding redundancies, providing fault 

detection systems (to initiate crew escape), and tightening 

requirements for manufacturing, assembly, systems test and 

checkout at the launch sites.

The process of human rating launch vehicles is central to the 

viability of commercial service for crew transport, as well 

as the option of using the heavy launcher as a backup. The 

Committee found a progressive new approach to human rating at NASA, reflected in the current human-rating guidelines (NASA Procedural Requirement 8705.2B). These 

guidelines, applicable to newly developed NASA vehicles, 

provide for intelligent application of similar and dissimilar 

redundancy when called for, and appropriate approaches to 

single-string design when unavoidable. In addition, there 

is a general set of guidelines (NPR 8715.3) that currently 

would be applied to NASA personnel operating in nonNASA vehicles.

In view of the complexity and cost of retroactively human 

rating a vehicle (comparable to a significant fraction of the 

original cost to develop the vehicle), the Committee suggests 

that all new NASA-developed vehicles, including heavy-lift 

launchers, be designed so that they are human-ratable, i.e., 

they could be reasonably human rated at some point in the 

future. This is a compromise between human rating them at 

inception and not human-rating them at all. It preserves the 

option to human rate in the future at lower cost. NASA would 

benefit from this approach so that it could use its heavy-lift 

launcher as a backup crew vehicle with Orion, should the 

commercial providers fail to deliver for any combination of 

business and/or technical reasons. Additionally, the criticality of cargo launched on the heavy-lift vehicle would suggest that NASA institute quality control and requirements 

comparable to human-rating guidelines in any event.

FINDINGS ON CREW LAUNCH TO LOWEARTH ORBIT 

(Note: a finding on the Ares I is presented in Chapter 4.)

 The Need for Independent U.S. Human Access to Space:

In the long run, it is important for the U.S. to maintain 

independent access to low-Earth orbit for its crews. In the 

future, this might be provided by government, commercial 

providers, or a combination of the two. 

 Commercial Launch of Crew to Low-Earth Orbit: Commercial services to deliver crew to low-Earth orbit are 

within reach. While this presents some risk, it could provide an earlier capability at lower initial and life-cycle costs 

than government could achieve. A new competition with 

adequate incentives should be open to all U.S. aerospace 

companies. This would allow NASA to focus on more 

challenging roles, including human exploration beyond 

low-Earth orbit based on the continued development of the 

current or modified Orion spacecraft. 

 Human Rating of Launch Vehicles: NASA has recently 

adopted a new, more outcome-based standard for human 

rating space systems, and has in its policy a more flexible 

approach for human rating existing or new third-party systems. NASA would be well served by applying these policies to field a set of safe yet efficient capabilities, including 

the provision that all newly developed, government–funded launch vehicles be readily human-ratable. In this way, if 

plans change in the future—for example, if the commercial 

capability of crew transport to low-Earth orbit fails to materialize—NASA would have a backup means of launching 

crew on heavy lift vehicles. 

 Safety: Human space exploration is an inherently risky endeavor. NASA should continue to make every reasonable 

effort to reduce the risks in spaceflight. Design for safety 

should be the prime but not only criterion in the development of systems and operations.

n 5.4 ADDITIONAL ISSUES IN LAUNCHER 

SELECTION

5.4.1 Launch Vehicle Performance and Costing

In evaluating the systems described in this chapter, the Committee noted that each has avid proponents, and as such the 

claimed cost, schedule and performance parameters include 

varying degrees of aggressiveness. Some of these estimates 

are close to or within the spread of historical programs, 

while others are well outside historical bounds. The latter 

could of course be attributed to fresh new approaches that 

make the historical databases inapplicable—or they could 

be attributable to unwarranted optimism. The analysis techniques employed in the assessment sought to differentiate 

between the two.

The only large potential decrease to the cost of space transportation, absent greatly increased traffic, resides in the 

adoption of a new paradigm for commercially purchasing 

highly reliable space transportation services. This approach 
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benefits from commercial best practices embraced by experienced providers of launch systems and new systems and 

processes offered by young firms. The price of shifting to 

commercial practices is to decrease the NASA workforce 

and sacrifice the expertise that has been built up at NASA 

over the years as the agency has directed and overseen the 

development of launch systems. This new strategy may 

eventually restore the total national space launch workforce 

in terms of expertise and number of workers, but near-term 

reductions would be expected.

The health and viability of the large solid-rocket motor industrial base rests in part on the choice of future crew transport and heavy-lift cargo launch system designs. Those that 

are all-liquid obviously present the most negative impact on 

the SRM industrial base and those that either launch crew 

with an SRM or support heavy-lift with SRMs provide the 

most benefit to the SRM industrial base. If the choice is to 

pursue all-liquid launch systems for both crew and cargo, 

there is no perceived future need for large segmented SRMs 

in support of civil space activities. 

5.4.2 Reliability

Reliability of launchers is important to the safety of 

crew, and the success of missions of exploration. The 

U.S. history of heavy-lift launcher reliability is shown 

in Figure 5.4.2-1. The historical record can be separated 

into two classes: those intended for human spaceflight, 

and those intended for cargo use. Saturn and the Shuttle 

are in the former class, while the other existing vehicles 

considered here are in the cargo class.

The most reliable U.S. heavy-lift launch vehicle built to date 

is the Shuttle, whose launch reliability, demonstrated by 

flight history, and computed using the Bayesian estimation 

process (based on a 50-percent confidence level, common 

for this type of analysis) is 98.7 percent. The Saturn vehicles also exhibited high reliability over their limited flight 

history. The less reliable Titan HLV only launched cargo, 

and the Delta IV H is limited to only three flights to date. 

During this examination of future space exploration 

launcsystems, the vehicles considered included those 

derived from Shuttle, Saturn and Delta IV–Heavy-heritage engines and motors (including Ares I and V and 

Shuttle derivatives), those derived from the EELV program families of launchers (Atlas V and Delta IV), and 

new vehicles with limited heritage (Falcon and Taurus 

II). Historically, vehicles with heritage derived from 

prior demonstrated systems have shown greater reliability in early usage than newly developed systems. The 

process of converting an established cargo launcher into 

a human-rated launcher results in improved reliability, 

as was demonstrated in the early U.S. human spaceflight 

programs where modified ICBMs were employed as 

launch systems. History has shown that the early flight 

period is of much higher risk than would be expected 

later in flight history. Figure 5.4.2-2 displays flight reliability for programs “managed by the U.S. government,” 

those managed by foreign governments, and those managed by commercial providers. It should be noted that 

all of the U.S. vehicles have in large part been engiFigure 5.4.2-1. Historical Growth of Demonstrated Launch Reliability. 

Source: Aerospace Corporation

Figure 5.4.2-2. Demonstrated reliability growth under various programs.

Source: Aerospace Corporation

Figure 5.4.2-3. Root Cause of Launch Vehicle Failures. 

Source: Aerospace Corporation
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neered and manufactured in industry, and that the socalled “commercial vehicles” were originally developed 

and produced under government (Air Force) contracts. 

Importantly, the latter began as ICBMs and, unlike the 

“government launch vehicles” category, are not humanrelated.

Space launch vehicles have a history of malfunctions 

caused by human pre-flight technical error rather than socalled “random” part failure or in-use operator error. This is 

clearly demonstrated in Figure 5.4.2-3 which shows the root 

cause of flight malfunctions derived from all U.S. heavy-lift 

launches to date.

Included in the data are the results of process and design 

errors associated with the Shuttle Thermal Protection System and SRB joint gas anomalies that were observed—

but were not viewed as hazardous prior to the failures of 

Challenger and Columbia, respectively. Although some 

Thermal Protection System anomalies continue to occur, 

SRB joint gas leaks, which had been a recurring problem 

with the large segmented solid motors, have been significantly less prevalent after the design changes following 

the Challenger failure. 

SUMMARY

There are many issues that must be carefully considered 

leading to the final decisions on the launch system for both 

heavy cargo and crew. These include, but are not limited 

to: 

• The cost, schedule and performance of the launch 

system.

• The likelihood that an increase in volume of 

production and operation, including by other 

customers, will decrease costs in the future.

• The impact on the present and future industrial base.

• The initial and ultimate reliability of the launcher, and 

the extent to which the heritage of the launcher 

influences the early operational reliability.

• The benefit of independent assurance in increasing the 

demonstrated reliability.

• The root cause of failures of launchers, and the extent 

to which these can be modeled and controlled by 

sound practices in design and processing.
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This chapter presents a synthesized set of options for the 

future of U.S. human spaceflight. Section 6.1 presents the 

evaluation criteria the Committee developed. The five key 

questions that framed the examination are briefly re-stated in 

Section 6.2, and the choices for each are summarized. These 

have been presented individually in Chapters 3, 4, and 5. 

In Section 6.2, pointers denote places where the individual 

choices will be discussed in the context of the Integrated 

Options. These analyses form the basis of Sections 6.3 

through 6.6. These Integrated Options tie together choices 

from the five key decisions to allow cost and schedule to be 

assessed, and an overall evaluation of progress to be made.

n 6.1 EVALUATION CRITERIA

In order to conduct an independent review of ongoing U.S. 

human spaceflight plans and alternatives, the Committee 

recognized that it would be important to define a process 

that would equitably evaluate the wide range of options 

to be identified. Consistent with the systems engineering 

approach, it was important to clearly define the set of criteria 

against which all options would be assessed, and to define 

an evaluation process that would enable a fair and consistent 

assessment of each option. Since many of the evaluation 

criteria are not quantitative, the Committee did not intend 

that the evaluation would generate a single numerical score; 

rather, it would provide a basis for comparison across options, 

highlighting the opportunities and challenges associated 

with each. Assigning weights to individual figures of merit 

is within the purview of the ultimate decision-makers. 

In order to identify Integrated Options that are safe, innovative, 

useful, affordable and sustainable, the Committee developed 

a number of evaluation criteria by which the relative merits 

of various human spaceflight missions and objectives could 

be compared. The Committee was chartered by the Office 

of Science and Technology Policy in the Executive Office 

of the President. The Committee’s Statement of Task (see 

Appendix C) provided important guidance. The Committee 

considered metrics suggested by its members, as well as 

those based on previous reviews and studies, such as the 

1991 Synthesis Group, as well as those derived from policy 

and historical documents including the Space Act of 1958 

and the 2004 Vision for Space Exploration.

There are numerous challenges in evaluating the complex 

set of Integrated Options considered for human spaceflight, 

because they vary widely with respect to three principal 

“dimensions”: 

• Benefits to Stakeholders. The community of 

stakeholders is diverse, and the potential benefits 

are equally wide-ranging. Stakeholders include: the 

U.S. government; the American public; the scientific 

and education communities; the industrial base and 

commercial business interests; and human civilization 

as a whole. Each option offers benefits to some subset 

of stakeholders, nations and humankind. These benefits 

include: the capability for exploration; the opportunity 

for technology innovation; the opportunity to increase 

scientific knowledge; the opportunity to expand 

U.S. prosperity and economic competitiveness; the 

opportunity to enhance global partnership; and the 

potential to increase the engagement of the public in 

human spaceflight.

• Risk. Each benefit has associated risks. There is 

uncertainty about the level of benefit that will actually 

be achieved, since attaining some of the goals may 

take decades. These risks are not independent of each 

other. NASA can mitigate some, but others are driven 

by external forces. Good program management can 

ameliorate schedule and programmatic risk, given 

sufficient schedule margin and financial reserves. 

Safety and mission risk can be managed by changing 

the mission profile or reducing program content. 

Programmatic sustainability is a key concern, since any 

change to the human spaceflight program is likely to 

affect existing contractual agreements and will require 

long-term commitments beyond the term of any one 

Program Options

and Evaluation

Chapter 6.0
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presidential administration. There is also risk to the 

nation’s workforce and capabilities in critical skills. 

Currently, NASA’s workforce represents expertise 

and experience that have enabled its outstanding 

achievements in space. The industry workforce 

is fragile, because once the need for a capability 

stops, marketplace pressures will diminish it, and 

reconstituting it may be very difficult and extremely 

costly. 

• Budget Realities. The desire to identify options 

that will fit within the existing budget is a significant 

constraint. Ultimately, only the President and 

Congress can determine what is affordable in the 

context of other major national financial demands. 

Human spaceflight is not a short-term commitment, 

and it requires budget stability for decades in order 

to achieve its goals. Year-to-year funding will affect 

NASA’s ability to successfully implement strategic 

decisions that can reduce total life-cycle cost. The 

Committee recognizes that operating costs have a 

sustained and significant impact on the budget, and 

they may limit the ability to start new efforts critical 

to achieving human spaceflight goals. For the purpose 

of this assessment, the Committee chose to represent 

the full cost of the programs and did not assume any 

financial contributions by international partners.

These dimensions were expanded into 12 criteria by which 

Integrated Options could be compared. The Committee 

clearly recognized that for each option there is some 

degree of uncertainty as to the magnitude of the influence 

and interdependence across the three dimensions. The 

Committee selected the following criteria as the basis for 

evaluation:

1) Exploration Preparation. Since the nature of 

exploration is, by definition, uncertain and subject to 

the surprise of discovery, it is important to establish 

a robust program that provides the opportunity to 

demonstrate technology, systems and operations that 

will be important in future exploration—specifically, 

a program that can be adapted to explore destinations 

that facilitate missions to Mars.

2) Technology Innovation. Integrated Options 

should enable technology maturation and foster the 

development of new modes of exploration, in addition 

to creating new technologies and new engineering 

knowledge that will enhance exploration. Technology 

development should also provide the opportunity 

to demonstrate national leadership in innovation. 

Technologies that are of use to stakeholders beyond 

NASA can be critical to the nation as a whole and 

should be sought during the exploration effort.

3) Science Knowledge. Integrated Options should 

address research areas critical to the scientific 

community as defined by the National Academies’ 

decadal survey priorities. They should include an 

implementation plan that supports accomplishment 

of the prescribed research as a key product of the 

mission. The Committee recognizes that for some 

decadal survey priorities, the requirement for the 

human spaceflight program is simply to do no 

harm. However, science can be enhanced by human 

exploration, particularly of complex environments, 

and by providing the ability to service scientific 

facilities in space.

4) Expanding and Protecting Human Civilization.

Integrated Options should lead to the possibility 

of a sustained off-planet human presence. They 

should also support research for physiological effects 

associated with radiation and zero- or low-g, as well 

as psychological stress associated with long-duration 

remote exploration. Finally, an option is more 

highly rated if it will aid in the protection of human 

civilization against a near-Earth-object impact.

5) Economic Expansion. Integrated Options should 

encourage and stimulate a growing, profitable 

industrial base. They should provide an opportunity 

for a sustained commercial engagement, and they 

should help increase U.S. development and production 

capabilities. Those capabilities would, in turn, increase 

the nation’s international competitiveness, as well as 

ultimately lower the cost of space transportation and 

operation.

6) Global Partnerships. Integrated Options should 

provide the opportunity to strengthen and expand 

international partnerships in the human spaceflight 

program. These would include existing international 

partners, but should not preclude expansion to 

new partners, and would allow partners to make 

contributions that could be on the critical path to 

mission success. Participation by other countries 

would be advantageous not only from the perspective 

of encouraging global cooperation, but also in terms 

of creating opportunities for synergistic research, risk 

reduction, cost-sharing and technology interchange.

7) Public Engagement. Integrated Options should 

inspire current and future generations, educate the 

public about the opportunities and societal benefits 

gained from space missions, and motivate young 

people to pursue an education in science, technology, 

engineering and mathematics, followed by careers 

that capitalize on this education. Options that provide 

the opportunity for regular visible accomplishments 

can galvanize broad public interest in exploration.

8) Schedule and Programmatic Risk. Integrated 

Options should be formulated to deliver a stated 

exploration capability on schedule. The technical 

design should be robust, and technologies required 

should be reasonably mature, with sufficient schedule 

and technical margins to support risk mitigation.

9) Mission Safety Challenges. The Committee did 

not carry forward any Integrated Option that failed 

to provide for reasonable crew safety and overall 

mission success. Therefore, to discriminate among 
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options, the Committee assessed the relative risk 

and complexity of mission scenarios and the likely 

impact on crew safety and mission reliability. 

Human exploration beyond low-Earth orbit will be 

riskier than current human spaceflight activities, 

since such exploration requires doing things that have 

not been done before, and the options for recovery 

will be limited. Missions that involve beyondlunar landings, beyond-near-Earth-orbit fly-bys, or 

complex orbital operations will have mission profiles 

with a significantly increased safety challenge.

10) Workforce Impact. The Committee evaluated the 

impact on the workforce in two ways: 1) the impact 

on national critical skills; and 2) the impact on the 

total NASA and industrial workforce. Each option 

was assessed for its potential impact on the critical 

skills across the nation and the ability to retain or 

develop the needed critical skills and expertise 

needed both in industry and at NASA. The impact on 

the total workforce is an assessment of the potential 

for a reduction of employment as a function of the 

dollar investment in human spaceflight. 

11) Programmatic Sustainability. Integrated Options 

should have a broad base of support for ongoing 

future funding. They should have a manageable 

impact on pre-existing contracts and enable a 

smooth transition from current human spaceflight 

operations. Support and advocacy for the option 

could come from other government agencies, spacerelated organizations, industry and Congress. 

12) Life-Cycle Cost. The FY 2010 budget for NASA’s 

future human exploration programs, including 

operations cost through 2020, is roughly $99 billion. 

The Committee was tasked to provide at least two 

options within this budget profile, and if appropriate, 

provide options that are somewhat less-constrained. 

Clearly, a program that meets the current budget 

with high value in other categories would be the 

ideal in complying with the Committee’s charter.

The Committee deliberated at length in public meetings 

about the advantages and disadvantages of each option with 

respect to these 12 criteria. Wherever possible, quantitative 

analytical assessments were utilized to inform the ratings. 

In the end, however, it was usually necessary to interpret the 

available information through the considered judgments of 

the 10 members of the Committee, based on their experience 

in space matters. The results were captured using a score of 

-2 (least benefit),-1, 0, 1 or 2 (most benefit) for each attribute 

of each Integrated Option.

n 6.2 KEY DECISIONS AND INTEGRATED 

OPTIONS

6.2.1 Key Decisions

The future of U.S. human spaceflight in the upcoming 

decades can be formulated in terms of five key questions, 

and the associated choices for answering each one. The 

questions, outlined in Chapter 1 and discussed further, with 

potential answers, in Chapters 3, 4 and 5, are:

1. What should be the future of the Space Shuttle?

• Prudent fly-out of remaining flights (currently part of 

NASA policy, but FY 2011 funding is not part of the 

President’s budget).

• Extend Shuttle through 2015 at minimum flight rate 

(only likely in conjunction with extending the ISS, 

and developing a directly Shuttle-derived heavy-lift 

vehicle).

This question will be examined in Section 6.4, in which 

some Integrated Options extend the Shuttle life and others 

do not.

2. What should be the future of the International Space 

Station (ISS)?

• Terminate U.S. participation in the ISS by the end of 

2015.

• Continue U.S. participation, through at least 2020 

(probably at an enhanced level of U.S. utilization).

This decision will be discussed in Section 6.4, in which 

some Integrated Options extend the utilization of the ISS by 

the U.S. and others do not.

3. On what should the next heavy-lift launch vehicle be 

based?

• Ares I plus Ares V.

• Ares V Lite dual launch, with no refueling required 

for lunar missions, but enhanced with (potentially 

commercial) refueling for more demanding missions.

• Directly Shuttle-derived vehicle, enhanced with 

(potentially commercial) refueling.

• Evolved Expendable Launch Vehicle (EELV)-heritage 

“super heavy” vehicle enhanced with (potentially 

commercial) refueling.

This discussion is contained in two sections of the chapter. 

Section 6.4 includes a comparison of the Ares I plus Ares V 

architecture with the Ares V Lite dual launch architecture. 

Later, the Ares family and other options are contrasted in 

Section 6.5.

4. How should crews be carried to low-Earth orbit?

• U.S.-government-provided systems.

• Commercially provided systems (with backup by U.S. 

government system).

Section 6.4 contains Integrated Options that include both 

choices.
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5. What is the most practicable strategy for exploration 

beyond low-Earth orbit?

• Moon First on the Way to Mars, with lunar surface 

exploration focused on developing capability for 

Mars.

• Flexible Path to Mars via the inner solar system objects 

and locations, with no immediate plan for surface 

exploration, then followed by exploration of the lunar 

and/or Martian surface.

Section 6.4 contains Integrated Options that have the Moon 

First as their strategy, while Section 6.5 presents those that 

explore along the Flexible Path. The cross-case analysis of 

these options will be presented in Section 6.6.

The Committee addressed one other underlying question: 

what meaningful exploration program beyond low-Earth 

orbit could be executed within the budget constraints 

represented in the FY 2010 budget. This will be the topic of 

Section 6.3.

The Committee considers the framing and answering of these 

questions, individually and consistently, to be its principal 

evaluation of the potential U.S. human spaceflight plans. 

The Integrated Options were prepared in order to understand 

the interactions of the decisions, particularly with regard to 

cost and schedule. By formulating the Integrated Options, 

the Committee did not mean to constrain the possible 

final decision, but only to inform it. Other reasonable 

and consistent combinations of the choices are obviously 

possible (each with its own cost and schedule implications), 

and these could also be considered as alternatives. The 

Integrated Options evaluated are intended to represent the 

families of options, yet without presenting an unmanageable 

number of alternatives. The Committee, in keeping with its 

charter, expresses no preference among these families, but 

does discuss the various advantages and disadvantages with 

respect to the evaluation criteria (without weighing those 

attributes).

6.2.2 Integrated Options

The Committee has defined five principal Integrated 

Options for human spaceflight. These have been selected 

from the more than 3,000 possible alternatives. Even after 

defining the choices for the five key decisions, 62 different 

options are possible. Not all of these combinations are 

worth considering—for example, it makes little sense to 

extend the Shuttle life if the heavy lift will be based on 

EELV heritage.

The five Integrated Options considered by the Committee 

are: one Baseline case, founded on the current Constellation 

Program, plus four alternate options, summarized for 

reference in Figure 6.2.2-1. The first two Integrated 

Options represent attempts by the Committee to develop 

alternatives that are compatible with the FY 2010 budget 

profile. Each follows an approach that is principally aimed 

at lunar exploration. Option 1 uses the content of the 

Program of Record, while Option 2 extends the ISS, uses 

commercial crew delivery, skips development of the Ares 

I, and uses the Ares V Lite as the sole NASA launcher. (See 

Figure 6.2.2-2.) The Baseline (Option 3) and the remaining 

two options are all fit to the same, less-constrained budget 

profile. Options 3 and 4 are also lunar-orientated strategies. 

Option 3 is an implementable version of the Program of 

Record, with nearly exactly the content of the Constellation 

Program, but with two minor changes in funding that the 

Committee found necessary: to extend the Shuttle into 

Note : Program-of-Record-derived options (Options 1 and 3) do not contain a technology program; all others do.

Figure 6.2.2-1. A summary of the Integrated Options evaluated by the Committee. Source : Review of U.S. Human Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 81

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

FY 2011, and to deorbit the ISS in 2016. Option 4 again 

extends the ISS, Lite and commercial crew. Option 5 is the 

one based on the Flexible Path. Integrated Options 4 and 

5 are explored in several variants that principally examine 

the sensitivity to the heavy-launch systems. A more visual 

representation, showing a possible decision logic among 

these options, is shown in Figure 6.2.2-3.

6.2.3 Methodology for Analyzing the Integrated 

Options

The committee used a synthesized cost-schedule-value 

methodology to assess the Integrated Options. In the 

first step, the Committee created the Integrated Options 

that have been presented in Figure 6.2.2-1. These 

options were intended to link together representative 

combinations of the outcomes. The Committee 

included the Baseline case of the Program of Record 

in the mix. The other Integrated Options were chosen 

to allow some of the key trades (destination, launch 

vehicles, etc.) to be contrasted.

The Committee used two candidate budget profiles 

for examining the Integrated Options. In the first, the 

guidance of the FY 2010 budget was enforced. This is 

called the “Constrained Case” or simply FY 2010 Budget 

Case, as shown in Figure 6.2.3-1. It became apparent to 

the Committee that options were needed that were not 

constrained to the FY 2010 budget. For planning and 

evaluation purposes, the Committee created a second 

budget profile that rose from the FY 2010 budget number 

to a sum $3 billion higher in 2014, and then rose at an 

expected inflation rate of 2.4 percent thereafter (Figure 

6.2.3-1). Thus, by combining the five key decisions and the 

two budgetary scenarios, the Committee produced the five 

Integrated Options, with variants, that are listed in Figure 

6.2.2-1.

Figure 6.2.2-2. Principal elements developed or used in the Integrated Options. Source : Review of U.S. Human Spaceflight Plans Committee

Figure 6.2.2-3. Suggested Integrated Option decision tree, showing the 

principal features of the options. Source: Review of U.S. Human Spaceflight 

Plans Committee

Figure 6.2.3-1. Two budgetary assumptions used by the Committee: the 

constrained budget which follows the guidance in the FY 2010 budget, and 

a less-constrained planning budget developed by the Committee. 

Source : Review of U.S. Human Spaceflight Plans Committee
8 2 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

Figure 6.2.3-2. Cost and Schedule methodology used by the Aerospace Corporation for affordability analysis of Integrated Options. Source: Aerospace Corporation
Review of U.S. Human Spaceflight Plans Committee 8 3

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

To assess the benefits and risks of these Integrated Options, 

the Committee next applied the evaluation criteria that had 

been selected (Section 6.1). In order to assess cost and 

schedule implications, the Committee then examined the 

Integrated Options using the affordability analysis tool. The 

Committee created a set of assumptions and ground rules 

for this analysis. These included budget profiles for the 

constrained and less-constrained budgets and input manifests 

for each option. 

The costs used by the Committee are intended to show the 

full cost of a program, and do not take into account any 

potential contribution by international partners. Much of 

the cost data input into the analysis originated from the 

Constellation Program. In those cases where the program 

cost estimates already contained a credit for an international 

contribution, this credit was removed by the Committee in 

order to show full cost. In other cases, the Committee itself 

or other sources helped to define the input. For example, the 

EELV super-heavy-launcher costs were based on Aerospace 

Corporation examination of the EELV development plans. 

The organizational transition costs in Option 5B were 

provided by NASA Headquarters. The in-space habitat in 

Options 5 was the result of an assessment of comparables 

performed by Aerospace. The Committee provided 

estimates for the commercial crew-to-low-Earth orbit costs, 

as discussed in Section 5.3.3.

The Aerospace team conducted the affordability analysis 

using the process described in Figure 6.2.3-2. This analysis 

outputs key dates and element costs at the 65 percent 

confidence level. It also estimates the uncertainty on dates 

and costs. Output manifests are derived based on the 

65th percentile confidence level, and are illustrative of the 

pace of missions and elements utilized. The affordability 

analysis corrects the input cost in several ways. First, it 

estimates a range of expected growth of the cost for each 

program element from System Design Review (SDR, Start 

of Phase B) to completion, based on historical data of NASA 

programs. At the average, this introduces a 51 percent growth 

from the estimate held at SDR in the cost for development 

(DDT&E costs). For elements that have not reached their 

SDR, such as the Ares V or commercial crew service, this 

full correction was applied. For elements that have passed 

their SDR, credit was given for subsequent development and 

maturity of the design. For example, the mean cost of the 

Orion in the analysis, due to this factor, is only 25 percent 

higher than would be reported by the Program of Record at

the mean. Other, more mature programs, such as the Ares 

I, receive credit by a similar process. In operations, a 26 

percent growth factor was applied to unproven systems, and 

no growth factor at the mean was applied to existing systems 

such as the Shuttle or the ISS, or to defined budget items 

such as the technology program.

NASA Headquarters asked the Program of Record to report 

cost and schedule at the 65 percent level, and the Committee 

attempted to report in a consistent manner. Note that on 

average, the difference between the mean of expected costs 

and the 65 percent confidence costs adds about 10 percent 

to all program costs calculated. Finally, the affordability 

analysis combines the development schedule of all the 

elements of the program. This process accounts for the 

additional cost to one element if another element it depends 

upon slips in its schedule. This integration of elements 

typically adds about an additional 10 percent to the total 

program costs, higher in more-constrained budgets, and 

lower in less-constrained budgets.

The Committee then examined the outputs of the affordability 

analyses, and it made interpretations to extract from them 

the primary information of interest, recognizing the inherent 

uncertainty in the analysis. The reporting by the Committee 

attempts to focus on its interpretation of the key milestones 

and associated uncertainties, and the pace of events after the 

initial milestone.

6.2.4 Reference Cases of the Entirely 

Unconstrained Program of Record

Unconstrained Program of Record: As an example of 

the affordability methodology applied to an actual integrated 

scenario, the reference case of an “implementable” version of 

the current Constellation Program of Record, unconstrained 

by any budget whatsoever, was analyzed. This implementable 

version contains only two slight variations from the actual 

program, instituted by the Committee: the provision for 

the Shuttle to be flown out in 2011 and additional funds 

for the deorbit of the ISS in 2016, after withdrawal of U.S. 

participation at the end of 2015. Note that the ISS is not 

extended to 2020 in this particular reference case. 

As assessed by the Committee, this case delivers Ares I/

Orion in late 2016, achieves human lunar return by the 

early 2020s, and a human-tended lunar outpost a few years 

later. These are very close to the dates held internally by the 

Constellation Program. However, the Committee’s analysis 

indicates that in order to achieve the milestones on that 

schedule, the implementable Program of Record requires, in 

real-year dollars (stated at 65 percent confidence):

• About $145 billion over the period from 2010 to 2020, 

which is:

• About $45 billion over the guidance of the President’s 

FY 2010 budget through 2020, and 

• About $17 billion more than what is provided in the 

“less-constrained budget.” 

• The expenditures reach $14 billion per year in FY 

2016, about $2 billion above the “less-constrained 

budget” and $5 billion over the FY 2010 budget for 

that year.

• The expenditures reach over $16 billion per year at 

their peak in FY 2019, $3 billion above the “lessconstrained budget” and $7 billion over the FY 2010 

budget for that year.

Thus, both the Program of Record, as assessed by the 

Constellation Program, and the unconstrained implementable 

version of the Program of Record, as assessed by the 

Committee, deliver Ares I and Orion in the mid-to-late 

2010s, and they both have human lunar return in the early 
8 4 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

2020s. Neither provides for extension of the ISS, or a space 

technology program of significance. The Committee’s 

finding is that the totally unconstrained implementable 

version of the Program of Record would significantly exceed 

even the “less-constrained budget.”

Unconstrained Program of Record with the ISS

Extension: This case would be identical to the above version 

of the Program of Record, but with the extension of the ISS 

to 2020. Since the budget for this case is unconstrained, no 

milestones slip, but more funds must be added to the NASA 

budget to operate the ISS in the years between 2016 and 

2020.

In this reference case, the Ares I/Orion again are delivered in 

late 2016, human lunar return is accomplished by the early 

2020s, and a human-tended lunar outpost is developed a few 

years later, again close to the dates held internally by the 

Constellation Program. The ISS is extended to 2020. But in 

order to achieve these milestones, this variant of the Program 

of Record requires, at a 65 percent confidence level, and in 

real-year dollars:

• About $159 billion over the period from 2010 to 2020, 

which is:

• About $59 billion over the guidance of the President’s 

FY 2010 budget through 2020, and 

• About $31 billion more than provided in the “lessconstrained budget.” 

• The expenditures reach $15 billion per year in FY 

2016, about $3 billion above the “less-constrained 

budget” and $6 billion over the FY 2010 budget for 

that year.

• The expenditures reach about $19 billion per year 

at their peak in FY 2019, $6 billion above the “lessconstrained budget” and $10 billion over the FY 2010 

budget for that year.

Furthermore, the technology budget is a small fraction of a 

billion dollars each year.

Although these two reference options represent the greatest 

continuity from the existing Program of Record, the 

Committee did not include them in the Integrated Options 

because they greatly exceed the FY 2010 budget profile 

and because the Committee does not consider them to be 

programmatically competitive with the Integrated Options 

discussed below.

n 6.3 INTEGRATED OPTIONS CONSTRAINED 

TO THE FY 2010 BUDGET

6.3.1 Evaluation of Integrated Options 1 and 2

The Committee was asked to provide two options that fit 

within the FY 2010 budget profile. That funding profile is 

shown in Figure 6.2.3-1 It is essentially flat or decreasing 

through 2014, then increases at 1.4 percent per year 

thereafter, which is slower than the 2.4 percent inflation rate 

used by the Committee.

Option 1. Program of Record as assessed by the 

Committee, constrained to the FY 2010 budget.

This option is the Constellation Program of Record, with 

only three changes: providing funds for the Shuttle into FY 

2011; including sufficient funds to de-orbit the ISS in 2016, 

and constraining the expenditures to the FY 2010 budget. 

Under this option the Shuttle retires in FY 2011, and until 

its retirement in 2015, international crew carriers are used 

to rotate U.S. crews to the ISS. When constrained to the 

FY 2010 budget profile, Ares I and Orion are not available 

until the latter years of the 2010s, after the ISS has been 

de-orbited, as shown in Figure 6.3.1-1. Starting in the late 

2010s, piloted flights in the Ares I and Orion could begin 

at a pace of several flights per year, but with no specific 

destination defined. The heavy-lift Ares V is not available 

until the late 2020s, allowing only orbital flights to the Moon. 

In addition, there are insufficient funds to develop the lunar 

lander and lunar surface systems until well into the 2030s, 

if ever. (See Figure 6.2.2-2.) In short, this program operates 

within current FY 2010 budget constraints, but offers little 

or no apparent value.

Option 2. The ISS and Lunar Exploration, constrained to 

FY 2010 budget. This option extends the ISS to 2020 and 

begins a program of lunar exploration using Ares V Lite in 

the dual launch mode. The option assumes Shuttle fly-out in 

FY 2011, and it includes a technology development program, 

a program to develop commercial crew services to lowEarth orbit, and funds for enhanced utilization of the ISS. 

As shown in Figure 6.3.1-1, the Shuttle retires in FY 2011, 

and international providers rotate crew to the ISS until U.S. 

commercial crew services become available in the mid-to-late 

2010s. Those providers are used to rotate the ISS crew until 

the Space Station’s retirement in 2020. This option does not 

deliver heavy-lift capability with the Ares V Lite plus Orion 

until the late 2020s and does not have funds to develop the 

systems needed to land on or explore the Moon. (See Figure 

6.2.2-2.) 

Figure 6.3.1-1. Timelines of the two Integrated Options constrained to the 

FY 2010 budget-milestones (above the line) indicate pace of activity, while 

ramped bars (below the line) indicate approximate range of uncertainty in 

the date at which the capability becomes available. Source: Review of U.S. 

Human Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 8 5

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

The Committee applied its evaluation criteria to assess 

Integrated Options 1 and 2, as shown in Figure 6.3.1-2. The 

analysis shows that Option 2, the ISS and Lunar Exploration, 

outperforms or equals Option 1 in all criteria. It has an equal 

(but low) Exploration Preparation rating, and performs 

equally on Science Knowledge, Public Engagement, 

Schedule Performance, Mission Safety Challenge, and 

Workforce Impact criteria. Option 2 is more highly rated 

under several criteria:

• The technology investment provides a higher rating in 

Technology. 

• The extension of the ISS improves its ratings in Human 

Civilization because of the added micro-gravity 

human physiology experience gained aboard the ISS, 

and in Global Partnerships because of the continued 

engagement of the international partners.

• Use of the commercial crew produces higher scores for 

Economic Development, and an improved score due to 

lower Life Cycle Costs.

• The resulting stronger advocacy increases the rating 

for Sustainability. 

6.3.2 Examination of alternate budget 

guidance

The first two Integrated Options allow examination of the 

underlying question: what meaningful exploration program 

beyond low-Earth orbit could be executed within the budget 

constraints represented in the FY 2010 budget? The Committee 

concludes that two executable alternatives comply with FY 

2010 funding guidance. Option 2 is scored on the evaluation 

criteria more highly than Option 1, which provides for neither 

the ISS extension nor technology development, but neither 

alternative provides for a viable exploration program. 

In the process of developing these options, the Committee 

conducted a sensitivity analysis to determine whether any 

reasonable exploration program (e.g., with different heavylift vehicles, or a different exploration destination) would 

fit within the FY 2010 budget guidance. The Committee 

could find none. In addition, the Committee tried to develop 

a variant of the Flexible Path that fit within the FY 2010 

budget, and such a variant looked no more promising than 

Option 2, with the first missions beyond low-Earth orbit in 

the late 2020s.

This analysis led the Committee to its finding that human 

exploration beyond low-Earth orbit is not viable under the 

FY 2010 budget guideline. It would be possible to continue 

the ISS and a program of human activity in low-Earth orbit 

within this budget guidance, and to develop the technology 

for future exploration, but the budget limitation would delay 

meaningful exploration well into the 2020s or beyond.

n 6.4 MOON FIRST INTEGRATED OPTIONS 

FIT TO THE LESS-CONSTRAINED 

BUDGET

6.4.1 Evaluation of Integrated Options 3 and 4

Option 3 and Option 4 (and its variants) pursue the Moon 

First exploration strategy, but are not constrained to the 

FY 2010 budget profile. Rather, they are fit to the “lessconstrained” planning budget that the Committee developed. 

That budget profile, shown in Figure 6.2.3-1, increases to 

$3 billion above the FY 2010 guidance between FY 2011 

and FY 2014, and then grows with inflation at an expected 

inflation rate of 2.4 percent per year. 

While it was formulating Integrated Options, the Committee 

quickly realized that viable options could not be found within 

the constrained budget. It then examined potential increases 

in the budget that would enable a sustainable and executable 

human spaceflight program. By examining several different 

potential expenditure profiles, the Committee arrived at the 

above investment level that would provide for the extension 

of the ISS, allow progress towards exploration beyond 

low-Earth orbit, and make an investment in technology. It 

provided a useful standard by which various options could 

be compared in a meaningful way.

Option 3. Baseline Case: Implementable Program 

of Record. This is an executable version of the Program 

of Record. (See Figure 6.2.2-2.) It consists of the content 

and sequence of that program: de-orbiting the ISS in 

2016; developing Orion, Ares I and Ares V; and beginning 

exploration of the Moon. The Committee made only two 

additions it felt essential: budgeting for the fly-out of the 

Shuttle in 2011 and including additional funds for the ISS 

de-orbit. The Committee then applied the less-constrained 

budget profile.

The Committee’s assessment of the schedule outcome for 

this option is shown in Figure 6.4.1-1. Under that schedule, 

the Shuttle retires in FY 2011, and international crew services 

Figure 6.3.1-2. Relative evaluation of factors under Option 1 (implementable 

Program of Record) and Option 2 (ISS + Lunar), both constrained to the FY 

2010 budget profile. Options closer to the center are of lesser value. Source: 

Review of U.S. Human Spaceflight Plans Committee
8 6 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

ferry U.S. crews to the ISS until its retirement in 2015. The 

option delivers Ares I/Orion in the mid–to-late 2010s, and 

flights to low-Earth orbit, but with no specific destination 

as yet definable. The Ares V becomes available, and human 

lunar return occurs in the mid-2020s. With a pace of about 

two flights per year, a lunar base begins to function about 

three years later.

Although not included by the Committee as an Integrated 

Option, a variant of Option 3 is possible that extends the ISS 

to 2020, adds the technology program, and maintains all of 

the other content of Option 3. Some would argue that this 

variant is actually the reference program on which NASA is 

embarked. But it should be emphasized that so far, no funds 

have specifically been allocated for continuing the ISS after 

2015. The Constellation Program, in its planning, assumed 

that funds that had been previously used for the operation of 

the ISS would become available to Constellation by 2016. 

Additionally, no funds were explicitly in the NASA plans for 

a robust, broad-based technology development program. 

The impact of extending the ISS to 2020 is to require the 

additional expenditure of about $14 billion between 2015 

and 2020. This additional expenditure, plus the technology 

program, combined with developing the Ares I and Orion 

within the “less-constrained budget,” causes significant slips 

to subsequent milestones. Orion and Ares I do not become 

available until the late 2010s, serving the last few years of 

the ISS. The development of heavy lift and its use in human 

lunar return slips to the late 2020s, so that the Ares I and 

Orion are left to either not fly at all for the better part of a 

decade, or fly in that interval in Earth orbit without the ISS as 

a destination. The Committee observed that the other options 

would be rated more highly by the evaluation process, so the 

Committee did not pursue this variant of Option 3.

Option 4. Moon First. This option preserves the Moon as 

the first destination for human exploration beyond low-Earth 

orbit. It also extends the ISS to 2020, funds technology 

advancement, uses commercial vehicles to carry crew to 

low-Earth orbit and funds the Space Shuttle into FY2011. 

There are two significantly different variants to this option. 

(See Figure 6.2.2-2.)

Variant 4A is the Ares V Lite variant. As shown in Figure 

6.4.1-1, this option retires the Shuttle in FY 2011 and relies 

on international launch support for crew delivery until the 

U.S. commercial crew services become available in the midto-late 2010s. The commercial crew provider ferries crew 

to the ISS until its retirement in 2020, after which there is a 

gap in human flight activity until the Ares V Lite in the dual 

launch mode is available for lunar exploration in the mid2020s. The beginnings of a lunar base follow about three or 

four years later.

Variant 4B is the Shuttle extension variant. This variant 

includes the only foreseeable way to close the gap in U.S. 

human-launch capability. As shown in Figure 6.4.1-1, this 

variant extends the Shuttle to 2015 at a minimum safe-flight 

rate. Shortly after the Shuttle is retired, commercial service 

picks up the ferrying of crew to the ISS until its retirement 

in 2020. This variant also takes advantage of synergy with 

the Shuttle by developing the more directly Shuttle-derived 

heavy-lift vehicle. However, even with the “less-constrained 

budget,” the more directly Shuttle-derived heavy launcher is 

not available until the middle of the 2020s, 10 years after 

the Shuttle retires. Therefore, the problems of continuity 

of systems and workforce skills are diminished in the early 

years, but reappear later. The more directly Shuttle-derived 

system has a higher recurring cost, so the flight rate within 

the “less-constrained budget” drops below two crew flights 

per year to the Moon, and a lunar base slips beyond 2030.

Again the Committee applied its valuation process to 

these Integrated Options and variants that fit within the 

Figure 6.4.1-1. Timeline of the two Integrated Options (and variant) that 

follow the Moon First strategy, fit to the less-constrained budget. Milestones 

(above the line) indicate pace of activity, while ramped bars (below the 

line) indicate approximate range of uncertainty in the date at which the 

capability becomes available. Source: Review of U.S. Human Spaceflight 

Plans Committee

Figure 6.4.1-2. Relative evaluation of factors in Option 3 (Baseline – 

Program of Record) and Option 4A (Moon First – Ares V Lite), subject to 

the less-constrained budget. Options closer to the center are of lesser value. 

Source: Review of U.S. Human Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 8 7

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

less-constrained budget and follow a Moon First strategy. 

The options can be compared in two steps. Figure 6.4.1-2 

shows the comparison between Option 3, the Baseline, and 

Option 4A, the Ares V Lite dual launch variant of the Moon 

First architecture. This shows that Option 4A matches or 

surpasses Option 3 in all metrics considered. The sources of 

these differences are:

• The use of the more capable Ares V Lite dual launcher, 

coupled with the extension of the ISS, providing for 

more Exploration Preparation.

• The technology investment causes a higher score on 

the Technology evaluation.

• The extension of the ISS improves the ratings on 

Human Civilization (more information on human longterm adaptation to space) and Global Partnerships.

• The availability of commercial crew launch gives an 

edge in Life-Cycle Costs and in Economic Expansion.

Thus the Committee finds that even with the Ares V family 

of launchers, and the Moon as the destination, there are ways 

potentially to extract more value from the program than to 

follow the Baseline.

In a second comparison, Figure 6.4.1-3 shows the relative 

valuation of the two variants of Option 4, the Moon First. 

Here the scores indicate some counts on which the Ares V 

Lite variant 4A scores better than the Shuttle-derived variant 

4B:

• The use of the more capable Ares V Lite dual launcher 

gives a higher score in Exploration Preparation.

• The use of the more economical Ares V Lite gives a 

better evaluation in Life-Cycle Costs.

• The more capable Ares V Lite dual launch allows 

simplification of launch and on-orbit operations, 

reducing Mission-Safety Risk.

In contrast, the more directly Shuttle-derived launcher in 

Option 4B scores better in Sustainability and Workforce 

Skills, both traceable to the continuation of the Shuttle 

system and workforce. This decision trades a more capable 

vehicle for more short-term benefit from advocacy and 

smaller workforce impact with the Shuttle-derived systems.

6.4.2 Examination of the key decision on the ISS 

extension

Comparison of Integrated Options 3 and 4A allow 

examination of the key decision concerning the future 

of the International Space Station: Should we stop U.S. 

participation in the ISS at the end of 2015, or continue 

U.S. participation, through at least 2020 (probably at an 

enhanced level of U.S. utilization)? The background for 

this question was presented in Section 4.2.

Extending the ISS would yield several benefits; chief 

among these is the support for global partnerships. By 

ending participation in 2015, the U.S. would voluntarily 

relinquish its leading role in this phase of international 

space exploration. By extending the ISS, we would 

further develop the international partnerships upon 

which the ISS is based, encouraging these ties to evolve 

into long-lasting relationships for space exploration. 

The return on investment on the part of the U.S. would 

be enhanced by 10 years of well-funded utilization 

in the 2010s, and by the operation of as a National 

Laboratory.

The ISS extension issue couples with Exploration 

Preparation. If properly used, the ISS could be a more 

effective testbed for development of the technologies and 

systems for exploration. Extending the ISS also leads to 

improved evaluation in Human Civilization. The extra 

years on the ISS would allow a better understanding 

of the adaptation of humans to micro-gravity, and the 

extension would produce more data for extremely long 

stays, important in planning for exploration.

The choice of ending U.S. participation in the ISS in 

2105 really provides only one benefit, that of freeing 

up the roughly $2.5 to $3 billion per year needed to 

run the ISS, which can then be invested in the more 

rapid development of the exploration systems. The 

Committee’s Integrated Option analyses show that if 

coupled to the choice of commercial crew launch system 

to low-Earth orbit and the Ares V Lite heavy lift choice, 

this expenditure on the ISS would delay the exploration 

of the Moon until the mid-2020s, only a few years 

after the most aggressive, unconstrained profile would 

accomplish it. (See Section 6.2.4.)

By applying the evaluation criteria it developed, the 

Committee finds extension of the ISS to 2020 to have 

greater value than the choice of ending U.S. participation 

in 2015.

Figure 6.4.1-3. Relative evaluation of factors in Option 4A (Moon First – 

Ares Lite) and Option 4B (Moon First – Extend Shuttle), subject to the lessconstrained budget. Options closer to the center are of lesser value. Source: 

Review of U.S. Human Spaceflight Plans Committee
8 8 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

6.4.3 Examination of the key decision on Ares 

V vs. Ares V Lite dual launch

Unlike the other four key decisions, each of which has been 

reduced in this chapter to two main choices, the decision 

on heavy lift is more complex, as indicated in Figure 5.2-1. 

The decision can be represented by three successive choices 

(Figure 6.4.3-1):

• At the highest level, the nation faces a choice of 

basing the heavy-lift capability on the NASA-heritage 

systems (Apollo and Shuttle) or on the EELV-heritage 

systems. 

• Within the NASA-heritage systems are those more 

directly based on the Shuttle, and those that belong to 

the Ares family. 

• Within the Ares family, there is the choice of Ares I 

plus Ares V system, currently planned, or the Ares V 

Lite (used in the dual mode for lunar missions) as the 

only vehicle developed. 

The issues behind this set of decisions were discussed in 

Section 5.2. In this section, the third choice will be examined. 

Because of the structure of the Integrated Options, the best 

head-to-head comparison of the other decisions is in the 

Flexible Path options in Section 6.5.

The Committee considered the comparison of the Ares V 

Lite, which for lunar missions would be used in dual mode, 

with the current architecture of Ares I plus Ares V. Setting 

aside the issues of crew launch on the Ares I, which will 

be discussed in Section 6.4.4, the principal distinguishing 

feature of the two alternatives is the extra-heavy cargo launch 

capability that would be provided by the Ares V Lite dual 

launch during lunar exploration. A secondary distinction 

is the relatively greater capability of the Ares V compared 

with the relatively lower performance demands placed on 

the Ares V Lite.

The main criteria involved in this comparison are 

Exploration Preparation, Schedule and Program Risks. The 

current Baseline Ares V has more launch capability than 

the Saturn V, but current NASA studies show that when 

used in combination with Ares I, it does not have enough 

launch capability to robustly deliver the currently planned 

landing and surface systems to the Moon. In order to deliver 

the greatest potential of the vehicle, many of the options 

to increase its performance have already been applied, 

including using 5.5-segment solid-rocket boosters (SRBs) 

and six RS-68-family engines (both of which require further 

development). There is a concern, expressed by some within 

NASA and by the Committee, that with performance already 

at the upper edge of what any Ares-V-family vehicle is likely 

to deliver, coupled with the potential weight growth of the 

payloads, the development will potentially face delays and 

added costs associated with weight-reduction campaigns. 

In contrast, the Ares V Lite backs off on proposed performance 

by using a five-segment SRB (already in development) and 

five RS-68-family engines. Thus the developmental risk 

of the Ares V Lite is somewhat reduced. The essential 

difference between the two options is the use of two heavy 

lifters that for a lunar mission will give substantial margin, 

and likely save development schedule and cost. The use of 

the two launch vehicles now decouples the operation of the 

Orion and Altair. The Ares V Lite dual launch allows a more 

robust Orion to be built, one that is capable of missions on 

its own—for example, launch with an Earth Departure Stage 

(EDS) to a near-Earth object (NEO), which will be discussed 

in Section 6.5. 

Programmatically, the choice of the Ares V (together with 

Ares I) unquestionably has less impact on current workflow 

or contracts. However, the Ares V Lite preserves some of 

the investment already made for Ares I, and would possibly 

allow some of the contract structure to stay in place. It 

would use the same five-segment SRB as the Ares I and 

the same J2-X engine for the Earth Departure stage. It 

would deliver a heavy-launch vehicle three to five years 

earlier than if the Ares I were built first (assuming the ISS 

is extended in both cases). Finally, construction of the 

Ares V Lite focuses NASA on the more challenging task 

of building the vehicle most needed for exploration, the 

heavy-lift booster.

The analysis performed for the Committee indicates that 

the Ares V Lite dual-launch scenario and the Ares I + Ares 

V scenario would have comparable operating costs. In a 

normal year of lunar exploration, for example, in the mid2020s, there would be four missions to the Moon, two with 

crew and two with cargo. In the Ares I + Ares V architecture, 

this would require two Ares I launch vehicles and four Ares 

Vs. In the Ares V Lite architecture, this same set of missions 

would require six Ares V Lites. Considering NASA’s high 

fixed recurring costs, the difference in total cost between 

four and six launches a year of the same system would be 

a small fraction of the annual cost. In the Ares I + Ares V 

architecture, NASA would have two of the six launches by a 

less expensive vehicle, but would have to operate two launch 

systems, with two processing flows at the Kennedy Space 

Center—offsetting the potential savings. While the Ares V 

Figure 6.4.3-1. Suggested launch vehicle decision tree, showing the decisions 

within the Ares family, between Ares and Shuttle-derived launchers, and 

between NASA and EELV-heritage launchers. Source: Review of U.S. Human 

Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 8 9

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

would nominally not have to be human-rated, the criticality 

of the payloads it would carry, and the NASA development 

culture, would likely (and appropriately) drive it to a nearly 

human-rated status. 

Ares I may have higher single-launch ascent safety than 

Ares V. Both would be high-reliability rockets, with the 

same capsule and launch escape system. The first stage of 

the Ares I is considerably simpler; however, because of the 

higher dynamic pressure in the flight profile of the Ares I, 

and its solid-rocket motor, a capsule on the Ares I would 

have a more challenging separation from the booster than 

a capsule on the Ares V. Ares I is not planned to launch at 

a rate higher than two per year, raising questions about the 

sustainability of safe operations. In contrast, up to six Ares 

V Lites are planned to launch each year, about the average 

rate of Shuttle launches throughout that program’s years of 

operation, contributing to a potentially higher demonstrated 

reliability.

There is widespread confusion about the findings of the 

Columbia Accident Investigation Board (CAIB) on the issue 

of mixing crew and cargo. The CAIB report said, “When 

cargo can be carried to the space station or other destinations 

by an expendable launch vehicle, it should be.” (page 211 

of the CAIB Report). That suggests that humans should not 

be put at risk to carry cargo (as they are in the Shuttle). The 

implication is not that humans should not be launched along 

with cargo if that makes sense (which was the case with 

Apollo).

Of the two vehicle choices, the Committee finds the Ares 

V Lite in the dual mode contributes to a higher score on 

the evaluation of options than does the Ares V. The critical 

difference is the use of the two Ares-V-family launchers 

for lunar missions. Even if the Ares I were to be built, the 

Committee’s findings indicate that the exploration missions 

would benefit from using the Ares V Lite in the dual mode 

as described.

6.4.4 Examination of the key decision on the 

provision of crew transport to low-Earth 

orbit

The key question pertaining to crew launch to low-Earth orbit 

is whether to carry the crews on systems provided by the 

U.S. government or on commercially provided systems (with 

eventual operational backup by a U.S. government system).

The Exploration Systems Architecture Study (ESAS) of 

2005 developed a plan to launch crew to the ISS, and to 

destinations beyond low-Earth orbit, using the Ares I. As 

discussed in the background on this decision in Section 

5.3, this would be a launch system with very high ascent 

safety, would have high component commonality with the 

Ares V, and would provide NASA organizationally with an 

opportunity to develop the Ares I before undertaking the 

more complex Ares V.

The alternative is to terminate the development of the Ares 

I and instead proceed with development of a commercial 

launch service to low-Earth orbit for crew. If based on a 

high-reliability rocket, and with a capsule and launch 

escape system, this approach too could have high ascent 

safety. It would also have the potential for significantly 

lower development cost, and therefore be available about a 

year sooner. Once operating, it would have the potential 

for significantly lower recurring costs, allowing the more 

rapid development of systems for exploration beyond lowEarth orbit in a constrained resource environment. The 

development of commercial crew service is not without 

significant programmatic risk, as discussed in Section 5.3. 

The choice of Ares I as the crew launcher was probably a sound 

choice in 2005. As is often observed, the rocket equation 

has not changed, so any reason that NASA would come to a 

different solution for crew transport to low-Earth orbit today 

than in 2005 would be due to changes in assumptions and 

constraints. The Committee in fact concludes that many 

of the assumptions on which the Ares I crew decision was 

based have changed. In contrast, the Committee found that 

the Orion should continue to be developed as a capable crew 

exploration vehicle, regardless of the decision on Ares I. 

Likewise, it should be emphasized that the Committee did 

not find any insurmountable technical issues with Ares I. 

With time and sufficient funds, NASA could develop, build 

and fly the Ares I successfully. The question is, should it?

First, from the perspective of schedule, the Committee 

observes that because of technological delays and the 

shortage of funds, Ares I will not effectively service the 

ISS, since the launch vehicle is expected to come on line 

in FY 2017, after retirement of the ISS. Even if the ISS 

is extended, within constrained resources, the Ares I and 

Orion will not be available until near the end of the decade, 

serving during only the last few years of the ISS. 

As noted, safety is paramount. 

It is unquestionable that crews 

need access to low-Earth orbit 

at significantly lower risk than 

the Shuttle provides. The 

best architecture to assure 

such safe access would be 

the combination of a highreliability rocket and a capsule 

with a launch escape system. 

While Ares I and Orion fit 

that description, so do other 

alternatives. The Committee 

was unconvinced that enough is 

Figure 6.4.4-1. Estimated total number of Ares I flights with different decisions on heavy lift and U.S. participation 

in ISS, assuming less-constrained budgets and no Earth-orbital flights other than those that service the ISS.

Source: Review of U.S. Human Spaceflight Plans Committee
9 0 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

known about the potential failures of any of the prospective 

high-reliability launchers plus capsule and launch escape 

systems to distinguish their safety in a meaningful way. 

The uncertainty in the safety models is large compared to 

the differences they predict, among competing systems, 

and it is clear that many of the failure modes observed in 

practice are not captured in the safety analysis. 

The budgetary environment today is significantly more 

constrained than in the assumptions used for the ESAS. 

Despite the significant architectural commonality of the 

Ares I and Ares V, the program now estimates that Ares I 

will cost $5 billion to $6 billion to develop, even assuming 

that all common costs are carried by the Ares V. Within 

existing budget constraints, that will delay the availability 

of the Ares V to the mid-2020s if the ISS is not extended, 

and another several years if the ISS is extended. When it 

begins operations, the Ares I and Orion would be a very 

expensive system for crew transport to low-Earth orbit. 

Program estimates are that it would have a recurring cost of 

nearly $1 billion per flight, even with the fixed infrastructure 

costs being carried by Ares V. The issue is that the Orion is 

a very capable vehicle for exploration, but it has far more 

capability than needed for a taxi to low-Earth orbit. 

Another understanding that has changed since the ESAS 

was performed is the traffic model. Figure 6.4.4-1 indicates 

the number of operational flights of the Ares I based on the 

choices made in two other decisions, and based on projected 

flight rates and the schedules estimated for the lessconstrained budgets. There are no Gemini-style missions 

included in this count that simply orbit and do not service 

the ISS. In none of the combinations are there more than 

about six Ares I flights in the next decade, or a dozen in the 

next two decades.

In the years since the ESAS, other conditions have changed 

as well. The NASA workforce has learned from the 

development of Ares I. With the approaching launch of the 

Ares 1-X flight test vehicle, much of what will be learned 

may have already occurred. The sunk costs in Ares I will 

be partially recovered in the development of the Ares V, due 

to the commonality of the SRB, J2-X engine, etc. Further, a 

commercial space industry has continued to develop, in part 

due to the investment of NASA in the Commercial Orbital 

Transportation Services (COTS) Program. Thus, the use of 

commercial vehicles to transport crews to low-Earth orbit 

is much more of an option today than it might have been in 

2005. 

Moving towards commercial crew services will also 

contribute to the evaluation on Economic Expansion. 

Together with commercial launch services for cargo to the 

ISS, and potentially in-space refueling, the commercial 

crew options could further stimulate the development of a 

domestic competitive launch capability. Eventually, it could 

stimulate a commercial service for human transport to lowEarth orbit that would be available to other markets.

In summary, the Committee found more potential 

contribution to the evaluation of Integrated Options due 

to the development of a commercial crew service to lowEarth orbit than in the continued development of the Ares I. 

Unfortunately, neither option is without problems. The Ares 

I would be safe, but late to serve the ISS and expensive to 

operate. It would not be operated very often, or many times 

in total. It would delay by years NASA’s start on a heavylift launcher. Although some of the development so far will 

be applicable to the Ares V, terminating Ares I would cause 

programmatic disruption. On the other hand, programmatic 

commitment at this time to commercial crew service to lowEarth orbit has benefits and risks. It has the potential to be 

safe, sooner and significantly less expensive. It would allow 

NASA to share operating costs with other customers. While 

the domestic development capability is demonstrated, some 

of the systems are largely notional. The Committee finds 

that if this alternative is pursued, the backup of a humanratable heavy launcher should be accelerated, as discussed 

in Section 5.3.

6.4.5 Examination of the key question on 

Shuttle extension

What should be the future of the Space Shuttle? A prudent 

fly-out of remaining flights (currently part of NASA policy, 

but FY 2011 funding for it is not part of the President’s 

budget) or an extension of the Shuttle through 2015 at 

minimum flight rate? A third option, discussed in Section 

4.1, of extending the Shuttle life by one flight is considered 

to be a variant of the 2011 fly-out option, which should be 

resolved by NASA.

The potential advantages of extending the Shuttle through 

2015 at a low but safe flight rate are to continue to support 

the ISS with heavy logistics, to smooth the short-term 

workforce dislocation of Shuttle workforce, and to help 

preserve the critical workforce skills associated with launch 

operations. Extending the Shuttle would also help “close the 

gap” by delaying the retirement of the only system the U.S. 

currently has, or is likely to have in the next five years, to 

deliver humans to low-Earth orbit.

When viewed in the Integrated Options, some of these 

potential advantages are conditional. Extending the Shuttle 

in combination with developing the Ares I and Orion would 

not entirely close the U.S. crew-launch gap. If the Shuttle is 

retired in 2011, the Ares I plus Orion would become available 

in 2017, producing a gap of about 7 years. If the Shuttle is 

extended, within a fixed budget, the funds that would have 

paid for the development of the Ares I and Orion will be 

further limited, and that will delay their availability until late 

in the 2010s, producing a gap of at least several years at that 

time. Additionally, the infrastructure changes and workforce 

transition required for Ares I would be delayed. The gap is 

not closed, but shifts to the future. The only way to close 

the gap in U.S. crew launch is to commission a commercial 

service for transporting crew to low-Earth orbit—which, 

because it is potentially less expensive to develop, may, 

at some risk, be available by 2016, even with extension of 

the Shuttle. Other than this scenario, the Committee found 

no way to close the gap. The inclusion in many Integrated 

Options of reliance on international crew launch services 

is an indication that the Committee found this to be an 

acceptable alternative as an interim measure. 
Review of U.S. Human Spaceflight Plans Committee 9 1

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

Extending the Shuttle would provide more up-mass and 

down-mass capability to the ISS in this interval, which would 

be a benefit. The current U.S. Space Transportation Policy, 

dated January 6, 2005, prohibits the government from taking 

actions that would put it in competition with commercial 

providers in space transportation. There is already a 

contract for NASA to buy commercial cargo launches, 

and it is not the Committee’s intent that a possible Shuttle 

extension disrupt plans for those commercial flights. Any 

additional Shuttle flights would supplement the ability of the 

commercial carriers to service the ISS; the one integrated 

option that includes a Shuttle extension specifically includes 

the full manifest of commercial cargo flights through 2015. 

Extension of the Shuttle would require that the recertification 

done by NASA be verified, to ensure it is consistent with 

the CAIB recommendation. Shuttle retirement is the current 

NASA plan, which is a position supported by the Aerospace 

Safety Advisory Panel. 

Extending the Shuttle would have a beneficial impact 

on the near-term workforce issues. Some workforce 

reductions would be indicated by the reduced flight rate 

proposed, but there would be several years in which to 

manage these reductions. In 2015, when the Shuttle finally 

retires, no NASA crew launch system would be available 

for several more years, and then the problem of maintaining 

key workforce skills would resurface. If, however, the 

commercial crew option were to be ready by 2016 or so, 

some national competence in crew launch would be nearly 

continuous.

Technically, extending the Shuttle makes the most sense 

if a directly Shuttle-derived vehicle is chosen to replace 

the Shuttle, which is the case in Option 4B. The relative 

advantages of this option are discussed below in Section 

6.5.2.

Taking all factors into consideration, the decision to extend 

the Shuttle or not is a complex trade. Consideration of nearterm access to low-Earth orbit, workforce and skills issues 

supports the extension. These benefits primarily materialize 

if the Shuttle extension is complemented by the development 

of commercial crew service to low-Earth orbit. The potential 

life-cycle costs and lower capability of the associated heavy 

launch system favor early retirement of the Shuttle.

n 6.5 FLEXIBLE PATH INTEGRATED 

OPTIONS FIT TO THE LESSCONSTRAINED BUDGET

6.5.1 Evaluation of Integrated Option 5

In the final family of options are those that pursue exploration 

using the Flexible Path strategy, discussed in Section 3.5. 

Like the Integrated Options in Section 6.4, these are not 

constrained to the FY 2010 budget profile. Rather, they 

are fit to the “less-constrained” planning budget that the 

Committee developed. As shown in Figure 6.2.3-1, that 

budget profile increases to $3 billion above the FY 2010 

guidance between FY 2011 and FY 2014, and then grows at 

a rate comparable to an expected inflation rate of 2.4 percent 

per year. 

Option 5. Flexible Path. This option follows the Flexible 

Path as an exploration strategy. It operates the Shuttle into 

FY 2011, extends the ISS until 2020, and funds technology 

development. In all three variants, as shown in Figure 6.5.1-

1, the commercial transport service becomes available in the 

mid-to-late 2010s to begin ferrying U.S. crew to the ISS. 

By the early 2020s, after the heavy-lift vehicle is developed, 

development of a small in-space habitat and an in-space 

restartable propulsion stage follows. All three variants also 

include a hybrid lunar lander that is smaller than the Altair. 

(See Figure 6.2.2-2.) The ascent stage is developed by 

NASA, but the descent stage is assumed to be commercially 

developed, building on the growing industrial capability 

pursuing NASA’s Lunar Lander Challenge and the Google 

Lunar X-Prize. The commercial lander could also use the 

NASA-developed, in-space restartable engine that would 

be used for missions on the Flexible Path. There are three 

variants within this option; they differ only in the heavy-lift 

vehicle.

Variant 5A is the Ares V Lite variant. It develops the 

Ares V Lite, the most capable of the heavy-lift vehicles in 

this family of options. Figure 6.5.1-1 shows the schedule 

for this option. The Ares V Lite becomes available in the 

early 2020s, and the Flexible Path missions—to the Moon, 

Earth escape to Lagrange points or near-Earth objects, and a 

Mars fly-by—occur at about one-year intervals. Initial lunar 

landing takes place in the mid-to-late 2020s. Lunar buildup occurs at a rate of about two flights per year with the 

more capable Ares V Lite. On-orbit refueling, or the use of 

a second Ares V Lite, is necessary for the most energetic of 

the Flexible Path missions.

Variant 5B employs an EELV-heritage commercial superheavy-lift launcher and assumes a different (and significantly 

reduced) role for NASA. It has an advantage of potentially 

lower operational costs, but requires significant restructuring 

Figure 6.5.1-1. Timelines of the three Integrated Options that follow the 

Flexible Path strategy, fit to the less-constrained budget. Milestones (above 

the line) indicate pace of activity, while ramped bars (below the line) indicate 

approximate range of uncertainty in the date at which the capability becomes 

available. Source: Review of U.S. Human Spaceflight Plans Committee
9 2 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

of NASA. It follows the same timeline as variant 5A up to 

the landing on the Moon. On-orbit refueling is used for the 

Flexible Path missions. Thereafter, the EELV-heritage Super 

Heavy flies two missions of three launches per year to the 

Moon, but does not carry as much load on each mission 

(unless on-orbit refueling is used). Thus a slower lunar 

development, or the development of a less massive lunar 

infrastructure, results. 

Variant 5C uses a directly Shuttle-derived, heavylift vehicle, taking maximum advantage of existing 

infrastructure, facilities and production capabilities. It, too, 

follows about the same timeline up to the first lunar landing, 

and uses on-orbit refueling for Flexible Path missions. When 

lunar missions begin, the higher recurring cost of the more 

directly Shuttle-derived heavy launcher causes a slower rate 

of lunar buildup. 

Comparison of the three Flexible Path valuations is shown 

in Figure 6.5.1-2. The distinguishing features are:

• The Ares V Lite Option 5A has an edge in Exploration 

Preparation, due to the more capable vehicle, and in 

Mission Safety Challenge because the more capable 

vehicle requires less complex ground and on-orbit 

operations.

• The EELV-heritage Super Heavy Option 5B has an 

edge in technology, because it includes a new U.S.-

developed large hydrocarbon engine, and the lowest 

(i.e. best) Life-Cycle Costs, due to the commercial 

nature of the operation. It does poorly in Sustainability, 

due to the disruption in contracts, workforce transitions 

and the new way of doing business that would be 

necessary at NASA.

• The more directly Shuttle-derived heavy launcher 

in Option 5C has an edge in Sustainability, due to 

advocacy for Shuttle-derived systems, but does poorly 

in Life-Cycle Costs.

6.5.2 Examination of the key question on Ares 

V family vs. Shuttle-derived heavy launcher

In Section 6.4.3, the decisions on heavy lift were outlined, 

and the comparison between the Ares V and Ares V Lite 

was discussed. In this section, the comparison between 

the Ares V family and the more directly Shuttle-derived 

launcher, as indicated by the decision tree of Figure 6.4.3-1, 

will be examined. The background for these decisions was 

presented in Section 5.2.

As discussed in Section 6.4.3 above, the two Ares V 

family launchers under consideration are the Ares V (with 

5.5-segment SRBs and six RS-68-family engines) and the 

Ares V Lite (with 5-segment SRBs and five RS-68-family 

engines). In comparison with the directly Shuttle-derived 

vehicles, these differences among the Ares V family are 

small. 

As also discussed in Section 5.2, the primary candidate for 

consideration from the more directly Shuttle-derived 

family is the in-line variant. This vehicle uses two 

4-segment SRBs, some number of Space Shuttle Main 

Engines (SSMEs) or the engine’s expendable derivative, 

the RS-25E (three or four, typically) on the bottom of a reengineered 8.3-meter-diameter tank, with an in-line EDS 

and, on top, a cargo payload or human-carrying capsule 

with a launch escape system. To the less-trained eye, such 

a vehicle would look much like an Ares V. In fact, at the 

end of the ESAS study in 2005, the candidate for the CaLV 

(Cargo Launch Vehicle) was exactly the Shuttle-derived 

variant just described. In the four years since ESAS, the 

design has evolved into the Ares V known today. Thus, the 

considerations for this choice of a more directly Shuttlederived vehicle vs. Ares V more or less exactly play out the 

trade studies conducted by NASA in the last four years.

The principal difference between the two families is the 

use of the SSMEs or their expendable derivative on the 

more directly Shuttle-derived launcher versus the use of 

the RS-68-family engines on the Ares V. The use of more 

Shuttle-derived components lowers the development cost 

somewhat, and accelerates by about a year the availability 

of heavy lift. But these dates of first availability of heavy lift 

are in the early 2020s at best, due to budget contraints and 

likely extension of the ISS. Therefore, even if a Shuttle–

derived vehicle is developed, and the Shuttle is extended, 

there is about a decade of gap in heavy-vehicle operations. 

This erodes the benefit of using the Shuttle extension and 

a more directly Shuttle-derived vehicle to close the critical 

workforce gap. 

Using the more directly Shuttle-derived vehicles does 

produce a somewhat less-capable vehicle (Figures 5.2-2 

and 5.2.1-1) and increases the recurring cost for a given 

mass launched to low-Earth orbit. For example, in a year 

Figure 6.5.1-2. Relative evaluation of factors in Option 5A (Flexible Path 

– Ares V Lite), Option 5B (Flexible Path – EELV Derived), and Option 5C 

(Flexible Path – Shuttle Derived), subject to the less-constrained budget. 

Options closer to the center are of lesser value. Source: Review of U.S. 

Human Spaceflight Plans Committee
Review of U.S. Human Spaceflight Plans Committee 9 3

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

of planned Constellation lunar operations in the mid-2020s, 

there would be three Shuttle-derived vehicle launches for 

each mission to the Moon, which would deliver a mass 

comparable to that of two Ares V-class launchers. Cargo 

missions would use one or two Shuttle-derived launchers. 

With two crew and two cargo missions per year, this would 

require eight to ten launches of the Shuttle-derived launcher, 

each with three or four SSMEs or derivatives, for a total of 

24 to 40 of the Shuttle engines being used, with a resulting 

high recurring cost.

Among the other notable differences between the Ares V 

family and the more-directly Shuttle-derived launcher family 

is the mission-launch reliability. Since the latter requires 

three launches for each planned Constellation lunar mission, 

there would be a somewhat lower reliability in any given 

time window than would be provided by the Ares V, which 

only would require two launches in the same time window. 

The Committee considered as an issue the commonality with 

the national space industrial base. The Ares V uses engines 

from the RS-68 family, with commonality in the industrial 

base with those used on the EELVs by National Security 

Space. Both the Ares V and the more-directly Shuttlederived vehicle have commonality in the solid-rocket motors 

with vehicles used in National Security Space.

In summary, the Committee viewed the decision between the 

Ares V family and the Shuttle-derived family as one driven 

by cost and capability. The development cost of the more 

Shuttle-derived system would be lower, but it would be less 

capable than the Ares V family and have higher recurring 

costs. There are potential workforce and skill advantages 

associated with the use of the more-directly Shuttle-derived 

system, but the long gap between when the Shuttle is 

retired in 2011, or even 2015, and when the Shuttle-derived 

heavy-lift launcher becomes available in the early to mid2020s would diminish the potential value of the workforce 

continuity associated with Shuttle derivatives. 

6.5.3 Examination of the key question on 

NASA heritage vs. EELV-heritage super-heavy 

vehicles

The highest-level decision on heavy-lift-launch vehicles 

is whether to base the launch system for exploration 

on these NASA-heritage vehicles or on the further 

extension of the EELV-heritage vehicles up to the 75-

mt range (Figure 6.4.2-1). It should be emphasized that 

this is not the existing EELV heavy launcher, which has 

a maximum payload to low-Earth orbit of about 25 mt, 

but rather requires the development of a substantially 

new vehicle, in part based on existing components and 

manufacturing facilities. 

The EELV-heritage super-heavy launch vehicle would 

be capable of launching about 75 mt to low-Earth orbit, 

significantly less than the Ares V family at 140 to 160 

mt, or the Shuttle-derived vehicle in the range of 100 to 

110 mt. However, the EELV-heritage super heavy is still 

larger than the Committee’s estimated smallest possible 

launcher to support exploration, which is in the range of 

40 to 60 mt. In a nominal piloted lunar mission, without 

in-space refueling, the EELV-heritage super heavy would 

require three flights, potentially with an additional crew 

taxi flight, versus two launches for the Ares V Lite. In the 

Flexible Path options, the EELV would not require more 

launches, but would involve more on-orbit operations 

than the Ares V-family approach. For these launch rates, 

the EELV would have a lower recurring cost than the 

NASA-heritage vehicles.

Initially, the EELV-heritage super heavy vehicle would 

use the Russian RD-180 hydrocarbon fueled engine, 

currently used on the Atlas 5. In the cost analysis 

utilized by the Committee, provision was made for the 

development of a new large domestic engine to replace the 

RD-180 for both NASA and National Security missions. 

This would have technology benefits, and would provide 

value to National Security systems.

While there are technical differences between the two 

families, the Committee intended the principal difference to 

be programmatic. The EELV-heritage super heavy would 

represent a new way of doing business for NASA, which 

would have the benefit of potentially lowering development 

and operational costs. The Committee used the EELVheritage super-heavy vehicle to investigate the possibility of 

an essentially commercial acquisition of the required heavylaunch capability by a small NASA organization similar to 

a system program office in the Department of Defense. It 

would eliminate somewhat the historic carrying cost of many 

Apollo- and Shuttle-era facilities and systems. This creates 

the possibility of substantially reduced operating costs, 

which may ultimately allow NASA to escape its conundrum 

of not having sufficient resources to both operate existing 

systems and build a new one.

However, this efficiency of operations would require 

significant near-term realignment of NASA. Substantial 

reductions in workforce, facilities closures, and mothballing 

would be required. When the Committee asked NASA to 

assess the cost of this process, the estimates ranged from 

$3 billion to $11 billion over five years. Because of these 

realignment costs, the EELV-heritage super heavy does not 

become available significantly sooner than the Ares V or 

Shuttle-derived families of launchers. The transition to this 

way of doing business would come at the cost of cutting 

deeply into a the internal NASA capability to develop and 

operate launchers, both in terms of skills and facilities.

There would be other consequences at the national level. 

Needless to say, the co-development of the EELV-heritage 

super heavy would require careful coordination between 

NASA and the Department of Defense to ensure joint 

value. 

In summary, the Committee considers the EELV-heritage 

super-heavy vehicle to be a way to significantly reduce the 

operating cost of the heavy lifter to NASA in the long run. 

It would be a less-capable vehicle, but probably sufficiently 

capable for the mission. Reaping the long-term cost benefits 

would require substantial disruption in NASA, and force the 

agency to adopt a new way of doing business. The choice 

between NASA and EELV heritage is driven by potentially 
94 Review of U.S. Human Spaceflight Plans Committee

SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

lower development and operations cost (favoring the 

EELV-heritage systems) vs. continuity of NASA’s system 

design, development and mission assurance knowledge 

and experience, which would provide higher probability of 

successful and predictable developments (favoring NASA 

systems). EELV-heritage launch systems, due to their lower 

payload performance, would require significantly greater 

launch and mission complexity to achieve the same total 

mass in orbit. The EELV option would also entail substantial 

reductions in the NASA workforce and closure of facilities 

necessary to obtain the expected cost reductions.

n 6.6 COMPARISONS ACROSS INTEGRATED 

OPTIONS 

6.6.1 Cross-option comparisons

A cross-family comparative evaluation is shown in Figure 

6.6.1-1, which contrasts the Baseline (Option 3) with the 

Ares V Lite variant of the Flexible Path (Option 5A). The 

Flexible Path option scores more highly than the Baseline on 

9 of the 12 criteria. The higher rankings include:

• Exploration Preparation (due to much more capable 

launch system)

• Technology (due to investment in technology)

• Science (because of more places visited)

• Human Civilization (due to the ISS extension) 

• Economic Expansion (because of commercial 

involvement in space elements and crew transport)

• Global Partnerships (gained by extending the ISS)

• Public Engagement (by visiting more new locations, 

and doing so each year)

• Schedule (exploring beyond low-Earth orbit sooner)

• Life-Cycle Costs (due to commercial crew services)

6.6.2 Examination of the key question on 

exploration strategy

The fifth and final of the key questions guiding the decisions 

on the future of human spaceflight is: What is the most 

practicable strategy for exploration beyond low-Earth orbit? 

In Chapter 3, three exploration strategies were presented, 

but the choice of exploration of Mars First was found not to 

be viable at this time. The two remaining choices are:

• Moon First on the Way to Mars, with surface exploration 

focused on developing capability for Mars

• Flexible Path to Mars via the inner solar system objects 

and locations, with no immediate plan for surface 

exploration, then followed by exploration of the lunar 

and/or Martian surface

This contrast can be highlighted by comparison of the 

reference variant for Moon First (Option 4A) and Flexible 

Path (Option 5A), as shown in Figure 6.6.2-1. These two 

options differ only in exploration strategy. The Flexible 

Path equals or exceeds the ratings of the Moon First option 

in all areas. It has an advantage in: Science, Economic 

Expansion, Public Engagement and Schedule. These four 

distinctions will be examined below.

From the perspective of Science Knowledge, the Moon 

First approach would allow better understanding of the 

evolution of the Moon, and use the Moon’s surface as a 

record of events in the evolution of the solar system. The 

Flexible Path would explore near-Earth objects, and also 

demonstrate the ability to service science observatories at 

the Lagrange points. The crews on such missions would 

potentially interact with robotic probes on the surface of 

Mars, returning samples as well. In some of its alternatives, 

including the one costed in Section 6.5, the Flexible Path 

also allows exploration of the Moon, though at a more 

limited scale than in the Moon First approach. Considering 

that we have visited and obtained samples from the 

Moon, but not near-Earth objects or Mars, and also that 

the Flexible Path develops the ability to service space 

observatories, the Science Knowledge criterion slightly 

favors the Flexible Path. Broadly, the more complex the 

environment, the more astronaut explorers are favored over 

robotic exploration. In practice, this means that astronauts 

will offer their greatest value-added in the exploration of 

the surface of Mars.

It is likely that the Flexible Path approach would engender 

more Public Engagement than the Moon First approach. In 

every flight, the Flexible Path voyages would visit places 

where humans have never been before, with each mission 

extending farther than the previous one, potentially leading 

Figure 6.6.1-1. Relative evaluation of factors in Option 3 (Baseline - Program 

of Record) and Option 5A (Flexible Path - Ares V Lite), subject to lessconstrained budget. Options closer to the center are of lesser value. Source: 

Review of U.S. Human Spaceflight Plans Committee
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to a full dress rehearsal for a Mars landing. A potential 

liability of the Moon First option is that it could appear to 

some stakeholders as a modern repetition of exploration 

that was accomplished 50 years earlier. 

Schedule also favors the Flexible Path scenario. The 

fundamental economics of the investment by NASA to 

begin flights on the Flexible Path and Moon First options 

are shown in Figure 6.6.2-2. Before lunar exploration can 

begin, NASA must complete four development programs: 

the heavy-lift launcher, the Orion capsule, the Altair lander, 

and at least some of the lunar surface systems. Even the 

well-funded Apollo Program only had to complete the first 

three of these. In contrast, exploration on the Flexible 

Path could begin with just the capsule and launcher, and 

then slowly develop much less costly in-space propulsion 

stages and habitats. After NASA explores on the Flexible 

Path for a half decade or so, it could then invest in the lunar 

lander and surface systems. In summary, the Flexible Path 

provides for exploration beyond low-Earth obit several 

years earlier, and allows a less demanding programmatic 

investment profile. 

Because the Flexible Path option contained a 

commercially developed lunar lander descent stage, it 

was evaluated more highly in Economic Expansion as 

well. The use of a commercial lander is not fundamental 

to the execution of the Flexible Path, but is more likely 

in this strategy. The lunar landing would be later, involve 

a simpler lander, and follow the development by NASA 

of the in-space re-startable engine, all of which would 

make a commercial system more viable in the Flexible 

Path than in the Moon First strategy.

Of the evaluation criteria on which the two strategies 

score equally, there are some distinctions. Under Human 

Civilization, both lead to better understanding of human 

adaptation to space, but the Flexible Path aids in the 

protection of Earth from near-Earth objects. From 

the viewpoint of Mission Safety Challenges, the two 

strategies are also about equal. Operations at the Moon 

are closer and allow return to the Earth more rapidly, but 

landing on and launching from a surface is a dynamic 

environment. In contrast, the Flexible Path missions are 

less dynamic, but occur farther from Earth.

There is no reason to believe that the remaining 

evaluation criteria favor one or the other strategy for 

exploration. They have more to do with how the strategy 

is implemented. For example, either the Moon First or 

Flexible Path could be the basis for a new or extended 

international partnerships in space.

In summary, 8 of the 12 criteria favor neither the Moon 

First nor Flexible Path strategies for exploration. 

However, of the four that do discriminate—Science 

Knowledge, Public Engagement, Schedule and LifeCycle Costs—all slightly to moderately favor the 

Flexible Path.

 

Finding on Evaluation of Program Options:

Options for human spaceflight should be evaluated by a 

set of criteria that are consistent with goals. The Committee identified 12 criteria which measure the capability of 

an option to satisfy its stakeholders, along the motivations 

listed above, along with programmatic issues of safety, 

cost, schedule, sustainability and workforce impact. It is 

the role of decision-makers to prioritize these measures.

Figure 6.6.2-2. Notional development cost (top and middle) and total program 

costs (development and operations - bottom) suggesting that the phasing of 

Flexible Path followed by the Moon First produces a more level budgetary 

profile. Source: Review of U.S. Human Spaceflight Plans Committee

Figure 6.6.2-1. Relative evaluation of factors in Option 4A (Moon First – 

Ares V Lite) and Option 5A (Flexible Path – Ares V Lite), subject to the lessconstrained budget. Options closer to the center are of lesser value. Source: 

Review of U.S. Human Spaceflight Plans Committee
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SEEKING A HUMAN SPACEFLIGHT PROGRAM WORTHY OF A GREAT NATION

Findings on Options for the Human Spaceflight 

Program: 

The Committee developed five alternatives for the Hu- man Spaceflight Program. In reviewing these, it found:

• Human exploration beyond low-Earth orbit is not 

viable under the FY 2010 budget guideline.

• Meaningful human exploration is possible under a 

less-constrained budget, ramping up to approximately 

$3 billion per year in real purchasing power above the 

FY 2010 guidance in total resources. 

• Funding at the increased level would allow either an 

exploration program to explore the Moon First or one 

that follows a Flexible Path of exploration. Either 

could produce results in a reasonable timeframe.
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The Space Act of 1958 calls on NASA to preserve the U.S. 

position as a leader in space technology. Today, the alternatives available for exploration systems are severely limited 

because of the lack of a strategic investment in technology 

development in past decades. Looking forward, NASA has 

before it an unprecedented opportunity to make an effective strategic technology plan. With a 20-year roadmap of 

exploration laid before it, NASA can make wise technology 

investments that will enable new approaches to exploration. 

Two recent reports of the National Academies have made 

recommendations in this regard.

The investments should be designed to increase the capabilities and reduce the costs of future exploration. NASA has 

conducted studies to demonstrate the mass reduction, and 

therefore operational cost savings, that are achievable with 

investments in technology. 

(See Fig 7.1-1.) As an illustration, it indicates an almost 

ten-fold reduction in mass 

required in mass required for 

future missions to Mars. If 

appropriately funded, a technology development program 

would re-engage the minds 

at American universities, in 

industry and within NASA. 

This will benefit human and 

robotic exploration, the commercial space community, 

and other U.S. government 

users alike.

n 7.1 FUNDAMENTAL UNKNOWNS

Three factors affecting long-duration human space exploration are of central importance, yet do not lend themselves 

to definitive assessment based on the available data: (1) the 

effects of prolonged exposure to solar and galactic cosmic 

rays on the human body; (2) the impact on humans of prolonged periods of weightlessness followed by a sudden need 

to function, without assistance, in a relatively strong gravitational field; and (3) the psychological effects on individuals 

facing demanding tasks in extreme isolation for well over 

year with no possibility for direct outside human intervention.

Critical Technologies for

Sustainable Exploration

Chapter 7.0

Figure 7.1-1. With technology investments, the mass required for a Mars exploration mission decreases from eight 

times the mass of the International Space Station to a mass comparable to the Station. Source: NASA
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While the specific technologies to address needed capabilities can and will be debated, if the United States wishes to 

conduct more and more capable missions in the future with 

nearly constant budgets, it is essential to develop and bring 

to flight readiness the technologies required. This will not 

happen without a sustained plan in which needed capabilities are identified, multiple competing technologies to provide that capability funded, and the most mature of them 

demonstrated in flight so that exploration architectures can 

then depend on them. For many technologies, it is less expensive to design a flight demonstration using the facilities 

on ISS than it would be to design a free-flying mission for 

each and every technology demonstration.

Radiation effects on humans: Beyond the shielding influence of the Earth’s magnetic field and atmosphere, ionized 

atoms that have been accelerated to extremely high speeds 

in interstellar space fill the solar system. The effects of such 

galactic cosmic radiation on crews on long-duration spaceflight far from the Earth are a significant concern. Additionally, normal solar flare activity also occasionally releases 

radiation potentially injurious to humans. On the Moon or 

on the surface of Mars, techniques are available to shield a 

human habitat from these sources of radiation, but the massive shielding is cost-prohibitive for a spacecraft. These 

radiation effects are insufficiently understood and remain a 

major physiological and engineering uncertainty in any human exploration program beyond low-Earth orbit. A 2008 

report by the National Research Council concluded, “Lack 

of knowledge about the biological effects of and responses 

to space radiation is the single most important factor limiting the prediction of radiation risk associated with human 

space exploration.” A robust research program in radiobiology is essential for human exploration. Research on these 

radiation effects on humans is limited on the ISS, since it is 

partly shielded by the Earth’s magnetic field.

In addition to studying the effects of galactic cosmic radiation (GCR), there are mitigation strategies, such as 

more effective shielding techniques, or the use of high 

shielding mass on a reusable habitat that cycles between Earth and Mars without being accelerated for 

each mission (cycler habitat), that need additional study.

Micro- and hypo-gravity effects on humans: While 

significant data on crew adaptation to micro-gravity now 

exists from extended ISS stays, there is a need to further 

develop countermeasures and build an understanding of the 

even longer profiles that will be encountered in exploration 

beyond low-Earth orbit. The ISS is a logical place to conduct such research, and the U.S. should obtain these data 

before the ISS is retired.

Psychological effects of extreme isolation on humans: 

While many experiments have been conducted on Earth to 

examine the effects of prolonged isolation on humans needing to continue to function at a high level, these experiments 

generally fall short of simulating the circumstance of extreme 

physical confinement in which the participant realizes there 

is no opportunity to “end the experiment.” In this regard, 

missions to Mars would be far more demanding than those 

to the Moon. Mars, at its closest, is 56 million kilometers 

from the Earth, whereas the Moon is 380,000 kilometers. 

In the latter case, return is generally possible within a few 

days. In contrast, Martian circumstances may require many 

months or years for an emergency return to Earth.

n 7.2 PROPELLANT STORAGE AND 

TRANSFER IN SPACE

Wernher von Braun wrote of the significant benefits to be 

gained from propellant transfer and storage in space. Up 

to this time, the normal approach for inserting payloads on 

trajectories away from low-Earth orbit towards the Moon 

or Mars is to use an upper stage called an Earth Departure 

Stage (EDS). In the conventional scheme, the Earth departure stage burns some of its fuel on the way to orbit and arrives at low-Earth orbit partially full. The remainder of the 

fuel is expended injecting the payload toward its destination beyond low-Earth orbit. An alternative, discussed in 

Chapter 5, is to re-fuel in space, so that the EDS can arrive 

in orbit mostly empty, and be refilled. After leaving Earth, 

exploration systems will still need to make one, two or three 

propulsive maneuvers, often after months in space. Again 

past experience is to use storable propellants for these maneuvers, but in human exploration, the cost of doing this becomes large.

The benefit of in-space cryogenic transfer and storage is that 

it enables refueling in space and the use of high-energy fuels for in-space propulsion. Using propellant transfer for the 

EDS, for example, allows more mass to be injected from the 

Earth with a given launch vehicle, or a smaller launcher for 

a given payload. 

Today, these technologies are considered ready for flight 

demonstration, according to both NASA and industry experts working in the field. (See Fig 7.2-1.) Nonetheless, 

legitimate questions remain as to the practical feasibility 

of the approach. These concerns generally center on cryogenic transfer and storage technology. Cryogenic transfer, 

storage and gauging in a micro-gravity environment create 

challenges that have been investigated by researchers in the 

laboratory for decades. Automated rendezvous and docking 

of delivery tankers has recently been demonstrated. Capabilities that remain to be demonstrated include:

• Long-term storage of very cold (cryogenic) propellant 

without excessive boil-off

• Transferring cryogenic propellant between tanks in a 

zero-g environment

• Making cryogenic fluid line connections

• Gauging the quantity of propellant in the tanks in a 

zero G environment

Fig 7.2-2 shows the maturity of various technologies based 

on the NASA Technology Readiness Level (TRL) system, 

summarizing the current assessment of capabilities required 

for propellant transfer and storage on orbit. 
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These cryogenic technologies have reached the point 

where a flight demonstration is the next logical step in development before this capability can begin to be designed 

into systems. The two technologies of liquid acquisition, collecting fluid in micro-gravity near the point from 

which it will be withdrawn from a tank, and automated 

fluid coupling cannot be tested in a realistic environment 

without in-space demonstration. Cryogenic coolers are 

needed for true zero-boil indefinite storage of liquid hydrogen (LH2), but other technologies listed in the table 

are intended to negate this problem for storage up to one 

year.

n 7.3 IN SITU PROPELLANT PRODUCTION 

AND TRANSPORT

After mastering the technologies for storing and transferring 

propellant in space, the next step is to manufacture propellant from resources already there. The lunar surface and 

some near-Earth objects are the only known sources of suitable resources that can be brought feasibly to cislunar space, 

such as to the Earth-Moon Lagrange Point L1, which was 

identified as a promising candidate for a cislunar propellant 

depot in a 2004 NASA study.

In situ propellant production requires the combination of 

two unique capabilities: (1) producing the propellant, and 

(2) transporting it economically. Oxygen is abundant in 

all lunar rocks and regolith (dirt without organic material), 

and a variety of chemical processes to extract it have been 

demonstrated in Earth-based laboratories. These propellant 

production methods must next be demonstrated on the lunar 

surface though robotic missions. Collecting lunar material 

and bringing it to a lunar-based processing station presents 

a great challenge. Laboratory work has shown that this will 

likely require both robotic and human-tended missions to 

mature the technology. 

In addition, it is also extremely important to produce hydrogen for fuel in space. If hydrogen can be economically extracted from the Moon, it will likely serve as a 

source of propellant for future exploration missions. If 

it cannot be produced, the 

case for exporting propellant from the Moon becomes 

less compelling, and nearEarth objects would rise in 

importance. Discoveries 

in recent years do suggest 

the availability of significant hydrogen deposits at 

the lunar poles. In addition, 

Apollo samples showed useful hydrogen deposits from 

the solar wind implanted in 

the regolith. These regolith deposits would require 

processing large amounts of 

material, comparable to coal 

extraction on Earth. Robotic exploration of the Moon 

continues today, and further 

interesting sources of resources may well be found. 

The composition of near-Earth objects is less well understood than the composition of the Moon because of the 

current dependence on telescope-based observations and 

inferences drawn from meteorites reaching Earth. These 

data suggest that almost any desirable resource can be 

found on near-Earth objects, but since each near-Earth 

object is a distinct body with its own orbit and properties, 

it is difficult to make generalizations about how resources 

would be extracted and returned to cislunar space. It is 

worth noting that in some cases, the energy required to 

return mass from a near-Earth object to near-Earth space 

is significantly less than to return mass from the lunar 

surface to Earth Moon L1 Lagrange Point. Therefore, further robotic exploration and human-tended pilot visits to 

near-Earth objects are particularly interesting subjects for 

future exploration. 

Reusable chemical rockets might also be used to deliver 

in situ propellant from the Moon to the Earth Moon L1 

Lagrange point. Space tugs carrying and using hydrogen 

are generally more compelling than tugs carrying and using other propellants. As an alternative, because of the 

Moon’s low gravity, non-chemical propulsion should also 

be considered. Catapults, tethers and beamed energy are 

likely to become practicable for Lunar-to-L1 transport 

long before they become practicable for Earth-to-orbit 

launch, and should continue to be investigated. Nonetheless, their application appears to be far off. 

Because about two-thirds of the mass on an Earth-to-Marsto-Earth mission would be propellant, cost-effective lunarproduced propellant could decrease the mass that must 

be lifted from Earth by a factor of two to three. Further, 

achieving industrial levels of oxygen and hydrogen production on Mars would greatly simplify the challenge of 

transporting fuel for the return trip from Mars to Earth.

In situ propellant produced on Mars has been considered as well. Oxygen could be extracted from the carbon-dioxide-based Martian atmosphere, and both oxygen 

Figure 7.2-2. Technology Readiness of Components for In-Space Refueling. Source: Review of U.S. Human Spaceflight 

Plans Committee
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and hydrogen could be extracted from Mars’ ample ice. 

Although laboratory work for extracting resources from 

Mars is promising, the technology remains to be demonstrated under realistic circumstances.

n 7.4 MARS ORBIT TO SURFACE 

TRANSPORTATION

The entry, descent and landing of cargo on Mars is difficult because Mars has sufficient atmosphere to drive the 

design of landing systems, but inadequate atmosphere for 

feasible parachutes or wings to safely land astronauts on 

the surface. Scientific probes landing on Mars have used 

a complex mix of aerodynamic braking and rocket propulsion. These techniques will have to be improved before 

larger robotic or crewed missions can be sent to Mars. 

This research and technology development program needs 

to be started soon, because it will require many iterations 

and increasingly larger missions before NASA is ready to 

demonstrate a safe, crewed Mars landing. Meanwhile, the 

intermediate results would greatly benefit future robotic 

missions. 

Because of the unique landing challenges posed by Mars, 

a robust human presence will require an advanced Mars 

orbit to Mars transportation system, most likely a reusable 

system that could transport cargo and people between the 

Martian surface and a depot located nearby. Nuclear thermal rockets, using in situ Martian-produced propellant, 

would fly to Martian orbit, collect a payload, and then use 

aerodynamic braking for the initial descent, followed by 

nuclear rocketry to land. Alternately, a chemical rocket 

would need to refuel on both Mars and in near-Mars space, 

such as on the Martian moon Phobos. Use of Phobos for 

propellant production would benefit transportation both to 

and from the Martian surface and provide the propellant 

for astronauts to return from Mars to Earth.

A Phobos-based teleoperated exploration of the Martian 

surface, returning with samples from that surface, would 

likely precede a crewed Mars landing mission, and would 

provide dramatically more responsive remote control than 

with the communication delays incurred between Mars and 

Earth. The use of Phobos- and/or Mars-produced in situ

propellant could likely reduce the flight cost of a crewed 

Mars landing expedition by a factor of two to three. 

n 7.5 ADVANCED SPACE PROPULSION

Since the 1950s, advanced space propulsion has been recognized as an extremely desirable technology for Mars 

missions, as is the possibility of aerocapture. (See Fig 

7.1-1.) The application of advanced space propulsion to 

crewed missions could significantly reduce the amount of 

propellant used, while providing sufficient thrust to build 

up interplanetary velocities relatively quickly—over days 

or weeks instead of months or years. Unfortunately, the 

physics of the problem are such that the more a vehicle 

tries to minimize propellant usage, the more power it consumes, yet since the power-supply weight increases with 

power generation requirements, a more substantial power 

supply can negate some or all of the benefits of lower propellant usage. 

Two promising advanced space propulsion technologies are 

based on solar and nuclear energy sources. 

• Solar: Current solar-power collectors are too heavy to 

deliver dramatic benefits in space propulsion. Solarelectric thrust is used today for some satellites and it 

may play a role in cargo transportation from LEO to, 

for example, L1 and back. Unfortunately, the acceleration it provides is so low that it would take months or 

years to get from Earth to the Moon, for example. As a 

result, for solar-powered advanced propulsion to provide revolutionary benefits, either far lighter, thin-film 

solar arrays must be matured, or the heavy solar power 

collector must be left off the space ship and the power 

from the collector beamed by lasers to lightweight collectors aboard the ship. 

 Theoretical studies indicate this latter technology is 

physically plausible, but it hasn’t made it out of the 

laboratory. In addition, the beam can only be held together over distances up to a few hundred thousand 

kilometers with a reasonable-sized transmitter. Solar 

technology requires research and development and 

flight demonstrations, as well as a large investment to 

build the solar-power collector and beam transmitter in 

space. However, such an effort might pave the way for 

transmission of power to the Earth for domestic use, 

although it is not known whether such systems will 

prove economical even if they were to be technically 

feasible.

• Nuclear: A more mature technology, nuclear-thermal 

propulsion reached advanced ground-firing demonstrations during the 1960s before the program was 

cancelled. With nuclear-thermal propulsion a nuclear 

reactor heats hydrogen and then ejects it to provide 

thrust. A nuclear-electric thruster, on the other hand, 

produces electricity to run an electric thruster, such as 

high power Hall effect thrusers or the variable specific 

impulse magnetoplasma rocket (VASIMR) thruster 

NASA is currently funding.

 Nuclear reactors today provide a substantial fraction 

of U.S. electricity production and other countries use 

nuclear reactors to produce an even larger fraction of 

their domestic power. For advanced space transportation, much lighter nuclear reactors are required. Although expensive to develop, this solution could cut 

the cost of missions from Earth by a factor of two or 

three. Alternately, it could be used to increase vehicle 

velocity for the same cost. Nuclear propulsion is probably essential for any crewed activity beyond Mars.

The space nuclear program is an excellent candidate for a 

multinational research effort because different countries 

have different capabilities and research interests. NASA 

would benefit from a coordinated multi-national research effort in this area. 
Review of U.S. Human Spaceflight Plans Committee 103

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n 7.6 TECHNOLOGY 

SUMMARY

In order to give future designers a rich 

and effective set of technologies to draw 

from, an investment in a broad-based 

space technology program is prudent. 

This should be done in a focused but 

long-term manner, with a clear metric 

of enabling and reducing the cost of future exploration. There are a number of 

potential technologies and approaches 

to be examined, as indicated in Figures 

7.6-1 and 7.6-2, which attempt to identify 

near- and longer-term benefits from the 

investment. Some of these technologies 

have been discussed above, and others 

throughout the report. NASA would not 

be the only beneficiary of these technologies. Other U.S. government and commercial users of space would benefit as 

well in terms of new capabilities or reduced cost. Consistent with administration planning, the Earth-based benefits 

to economic recovery, energy technology, biomedical science and health, and 

protection of our forces and homeland 

have been indicated.

FINDING ON TECHNOLOGY 

DEVELOPMENT

Technology development for ex- ploration and commercial space:

Investment in a well-designed and 

adequately funded space technology 

program is critical to enable progress 

in exploration. Exploration strategies can proceed more readily and 

economically if the requisite technology has been developed in advance. 

This investment will also benefit 

robotic exploration, the U.S. commercial space industry, the academic

community and other U.S.-

government users. 

Figure 7.6-1. Technology opportunities to impact near- and mid-term exploration capabilities and 

sustainability. Source: Review of U.S. Human Spaceflight Plans Committee

Figure 7.6-2. Technology opportunities impact longer-term capabilities and sustainability. 

Source: Review of U.S. Human Spaceflight Plans Committee
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Various forms of partnerships have been discussed throughout the report. This section examines in greater detail international partnerships (Section 8.1), as well as partnerships 

among elements of the U.S. government (Section 8.2).

n 8.1 INTERNATIONAL PARTNERSHIPS

The human exploration of space is historically intertwined 

with the recent evolution of America’s international relationships. The U.S. has moved from an era of competing with 

the Soviet Union in the Apollo era, to collaborating with our 

historical allies in Space Station Freedom, to embracing the 

Russians in the International Space Station, and now to engaging many potential new partners. 

Space exploration has become a global enterprise. Many 

nations have aspirations in space, and the combined annual 

budgets of the space programs of our principal partners are 

comparable to NASA’s. (See Figure 8.1-1.) If the United 

States is willing to lead a global program of exploration, 

sharing both the burden and benefit of space exploration in 

a meaningful way, significant accomplishments could follow. Actively engaging international partners in a manner 

adapted to today’s multi-polar world could strengthen geopolitical relationships, leverage global financial and technical resources, and enhance the exploration enterprise.

One means of reducing the funding demands of major human spaceflight programs is to join in partnerships with 

other nations that share common space goals. Thus far, 

three nations have by themselves placed astronauts in space: 

the U.S., Russia and China. International programs offer 

the added advantage of providing access to advanced technology not available in the U.S., an increasingly common 

circumstance (e.g., Russian-designed, hydrocarbon-(RP-1)-

fueled liquid rocket motors). Such arrangements also facilitate cost sharing. 

The principal disadvantage of international programs (excluding business-to-business arrangements based on enforceable contracts) is that nations are sovereign entities 

and, as such, can unilaterally change their plans—which 

can be very disruptive. Much of the international community, probably justifiably, faults the U.S. with regard to this 

practice. But perhaps an even greater impediment to U.S. 

involvement in international cooperative programs is the 

U.S. International Trafficking in Arms Regulations (ITAR). 

The Committee deems these laws to be outdated and overly 

restrictive for the realities of the current technological and 

international political environment. 

Partnerships 

Chapter 8.0

Figure 8.1-1. The annual budgets of civil space agencies in 2007. The sum of 

the budgets of potential partners is now comparable to NASA’s budget. Source: 

Various Sources
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International programs are generally more difficult to manage than national programs, in part because of the need for a 

greater degree of consensus and coordination; however, this 

can often be overcome when one of the participating nations 

serves in a leadership role—as distinct from a domineering 

role. The management structure that has evolved for the ISS 

has proven particularly effective and could serve as the basis 

for the next major international cooperative human venture 

into space. The Committee suggests that the President invite America’s international partners to join with America in 

discussions of this possibility.

The question occasionally arises whether the public would 

support space accomplishments shared among nations, as 

opposed to those representing purely “American” achievements. But the fact is that human spaceflight has always 

existed in an international context, first as competition and 

more recently as cooperation. It is difficult to argue against 

the latter. Moreover, the U.S. space program, at its height, 

had the self-confidence to emphasize that the United States 

was acting as a representative of all humanity. The Apollo 

11 plaque left on the Moon reads: “Here men from the planet 

Earth first set foot upon the Moon July 1969, A.D. We came 

in peace for all mankind.”

If international programs are to succeed (i.e., where a true 

partnership that benefits all parties exists), there will inevitably be some measure of dependency of the member nations 

upon one another. In some cases this may imply dependency with regard to capabilities that lie on a mission-critical 

path—witness the impending launch gap. Nonetheless, if 

effective and meaningful partnerships are to be established, 

some degree of such dependency is simply the price of admission—a price, the Committee concludes, that is worth 

paying in most instances.

International cooperation has been fruitful for both robotic 

and human space missions. The U.S. has enjoyed long, positive space exploration partnerships with several countries. 

The U.S. has participated in cooperative efforts with Europe 

for many years, both through independent European country 

agencies and through the European Space Agency. Similarly, the U.S. has excellent historical space relationships with 

Japan and Canada.

The U.S.-Russian space partnership has roots in the ApolloSoyuz Project of the early-to-mid 1970s. The current partnership began in the early 1990s with Phase I (Shuttle-Mir) 

and continues today with Phase II (ISS) programs. The advantages have been noteworthy: Mir was revitalized and 

extended because of the capabilities of the Space Shuttle, 

and Russian assets provided U.S. logistics and astronaut 

transport to the ISS following the Space Shuttle Columbia

accident.

In addition to synergies in space exploration, international 

civil space cooperation has provided positive grounds for 

fostering understanding between peoples and governments 

of partner countries. This Committee believes that the existing partnerships should be continued, and it urges the U.S. 

to consider expanding partnership by forming cooperative 

relationships with other countries, doing so within the current ISS partnership framework. This framework would 

serve as the foundation for international collaborations involving exploration beyond low-Earth orbit. This position is 

consistent with the recent National Research Council report 

“America’s Future in Space: Aligning the Civil Space Program with National Needs,” which calls for enhancement 

of overall U.S. global leadership through global leadership 

in civil space activities. Specific recommendations address 

aligning international cooperation with U.S. national interests, which include expanding international cooperation and 

partnerships for: the study of global climate change; the 

development of a body of law for a robust space-operating 

regime; rationalization of export controls; expansion of the 

ISS partnership; continuation of international cooperation 

for scientific research and human space exploration; engagement of nations in educating their citizens for sustainable 

space technology development; and support for interchange 

among international scholars and students. Partner countries could develop planetary landers, Earth departure stages, 

habitats, and other significant systems and sub-systems. As 

the lead partner, the U.S. could develop the heavy-lift launch 

vehicle. This scenario would help divide costs equitably and 

elevate the prominence of partner countries.

The Committee notes that China has had an operational 

human spaceflight program since 2003, and India has announced plans to launch astronauts into space using indigenous assets. The U.S. and India have already begun cooperative activities in space: the Chandrayaan-I spacecraft was 

flown to the Moon in October 2008 with U.S. instruments 

onboard. A number of nations are already developing capabilities that could significantly contribute to an international 

space exploration program. The U.S. has announced that 

it held preliminary discussions with China regarding joint 

space activities. It is the view of the Committee that China 

offers significant potential in a space partnership. China has 

a human-rated spacecraft and booster system and is only the 

third country to launch astronauts into space. It has demonstrated advanced capabilities, including extra-vehicular 

activity on a September 2008 mission. China plans to fly 

the heavy-lift Long March V vehicle before 2015, which it 

indicates will eventually be used to establish a space station, 

currently planned for initial launch in 2020.

8.1.1 International Space Capabilities. The following summarizes the extent of demonstrated activities in 

space by nations other than the U.S.

Canada. The Canadian Space Agency (CSA) is a partner 

in the ISS with significant experience in human operations 

in space. CSA has specialized in robotics and teleoperated 

systems, but also has extensive experience in remote sensing, radar, on-orbit servicing, communications and space 

science. 

China. As the third nation in the world to launch humans 

into space, the People’s Republic of China (PRC) has developed an indigenous capability for the technical requirements 

associated with human spaceflight. The PRC has a stable 

of space launch vehicles up to medium-lift capability (9 mt 

to low-Earth orbit, with upgrade to 25 mt envisioned), including the upper stage capability for geo-transfer orbit and 
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interplanetary trajectories. China has launched one robotic 

probe to the Moon and has follow-on missions planned. The 

PRC has robust capabilities in communications, navigation 

and Earth-observation satellites. Next on its announced human spaceflight agenda are demonstrations of rendezvous 

and docking and the construction of an orbiting space laboratory. The PRC has demonstrated capabilities in life support, power generation and storage, pressurized module construction, in-space propulsion and attitude control, guidance 

and navigation, communications and computation. 

India. The Indian Space Research Organization (ISRO) 

possesses two very capable launch vehicles, and an upgrade 

is underway to provide a medium-lift capability. India also 

has an indigenous capability to produce complex satellites 

and robotic scientific probes, as demonstrated by their first 

interplanetary robotic mission to the Moon in 2008. A human spaceflight program is being strongly recommended 

to the Indian government by ISRO, and is likely to be approved— which could lead to Indian human spaceflight capability as early as 2015. To date, the Indian space program 

has concentrated on telecommunications, Earth observation, 

and other low-Earth orbit satellite programs. 

Japan. The Japan Aerospace Exploration Agency (JAXA) 

conducts a robust space program and is a partner in the ISS. 

Its workhorse launch vehicle, the H-II, has been upgraded to 

the H-II Transfer Vehicle for use as a logistics carrier to the 

ISS. While the Japanese space program has a lower launch 

tempo than other major space-faring nations, it has extensive capabilities, as demonstrated by the ISS Kibo laboratory, which includes teleoperated robotics. Japan has extensive experience in Earth- and space-science missions and 

telecommunications satellites, as well as in-ground-based 

facilities for astronaut training, mission operations, communications and tracking. Japan launched the very successful Kaguya lunar robotic mission in 2007 and has plans for 

follow-on lunar missions. 

South Korea. The Republic of Korea has its first space 

launch vehicle, developed with Russian assistance, ready 

for flight. Korea has flown as a spaceflight participant to 

the ISS (via Russian launch and return), but has no other 

human spaceflight experience. The Republic of Korea has 

announced plans to develop a lunar orbiter by 2020. 

Russia. Russia has a complete suite of space capabilities, from a robust launch vehicle stable to a broad spectrum 

of spacecraft design, production and operation capabilities. 

Russia fields a number of space launch vehicles of proven 

design from small through medium (25 metric tons to lowEarth orbit) with various upper-stage combinations that can 

provide payloads not only to low-Earth orbit but also to geotransfer orbit and to interplanetary trajectories. Russia is 

one of three nations to demonstrate the capability to launch 

humans into space. The highly evolved Soyuz spacecraft is 

currently programmed to become the linchpin of the ISS in 

the immediate future. Russia has also demonstrated capabilities in: large space structures; pressurized modules; life 

support; power generation and storage; communications; 

thermal control; propulsion and attitude control; guidance 

and navigation; remote sensing; computation equipment; 

subsystems; and operations techniques. These are all elements necessary for both human and robotic space exploration. Currently, the Iran, North Korea and Syria Nonproliferation Act (INKSNA) has limited cooperation in space 

operations between Russia and the United States.

European Space Agency. The European Space Agency 

(ESA) and its member states possess very significant space 

capabilities. ESA is a partner in human spaceflight for the 

ISS and has demonstrated its ability to build large pressurized habitable modules for use as part of the ISS, as well as 

launch, rendezvous, and other critical capabilities. Through 

Arianespace (a French company owned by the French government), the Europeans possess the most active commercial space launch program in the world, with various launch 

vehicles up to medium capability (21 mt to low-Earth orbit). 

They have demonstrated the capacity to put significant payloads on interplanetary trajectories and have demonstrated 

space navigation and communications for both low-Earth 

orbit and interplanetary robotic probes. ESA possesses industrial and commercial capabilities to build complex spacecraft and robotic probes, including all subsystems. The Automated Transfer Vehicle has provided significant logistics 

support to the ISS and has the potential to be upgraded to 

a cargo return vehicle, and eventually a human-carrying 

spacecraft. Individual member states also have interest in 

and the capacity for cooperation outside the ESA structure. 

Cooperation with both ESA and individual European states 

allows access to significant technological capabilities.

Nations other than the above have very limited space programs, but could potentially play niche roles as their national industrial and technical capabilities allow.

n 8.2 U.S. INTRA-GOVERNMENT 

PARTNERSHIPS

The Committee has examined issues about the space programs managed by U.S. government agencies besides 

NASA, such as the Department of Defense (DoD) and the 

Commercial Space office of the Federal Aviation Administration (FAA). Their focus includes the potential impacts 

of “human-rating” the current Evolved Expendable Launch 

Vehicles (EELV) as one option to reduce the post-Shuttle 

launch gap. The FAA concentrates on the role commercial 

space companies can play in the space exploration program.

A study sponsored by the Congress in July 2008 titled 

“Leadership, Management, and Organization for National 

Security Space” described the total U.S. space enterprise as 

including civil space, commercial space, and national security space (military and intelligence focused). All of these 

elements have overlapping capabilities, share technologies 

and depend on a common industrial base. As a result, any 

examination of the U.S. human space program must consider its impact on the efforts of agencies responsible for 

these other U.S. space activities and vice versa.

The most obvious concern has been expressed by the DoD, 

particularly the U.S. Air Force, because of its unique role 
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today as the single agent for government expendable launch 

capabilities. The family of Evolved Expendable Launch 

Vehicles (EELV)—Atlas V and Delta IV—represent the 

primary heavy-lift capability for the DoD and intelligence 

communities. Any changes in configuration to these EELV 

systems, such as incorporating crew escape systems in order to human-rate them, raise concerns about the potential 

impacts on cost and the ability to reassign vehicles from the 

EELV production line to high-priority national-security missions.

The Committee reviewed the technical changes required to 

human rate an EELV. It also met with the National Security Space leadership in the Office of the Secretary of Defense, the Air Force, and the National Reconnaissance Office. Their views on this matter were consistent. None of 

the national security organizations would formally object to 

human rating an EELV, if that option were indeed chosen by 

NASA for its space exploration requirements. However, the 

concerns noted above were expressed and would need to be 

managed.

The EELV program was initiated in 1995 in response to the 

Space Launch Modernization Plan and a subsequent National Space Transportation Policy PDD/NSTC-4. In 1998, 

development agreements were awarded to Lockheed Martin 

and Boeing to incorporate government requirements (both 

civil and national security) into their commercially developed variants of the Atlas and Delta launch systems. Since 

2002, the Atlas V and Delta IV EELV vehicles have successfully demonstrated the ability to meet all of the key performance requirements of mass-to-orbit, reliability, and standardization of launch pads and payload interfaces. Because 

the low-Earth orbit commercial satellite market envisioned 

in the early-2000 time period never materialized, the U.S. 

government is still the primary customer for the EELV systems, which are now operated by United Launch Alliance, 

a joint venture of Lockheed Martin and Boeing. In 2005, 

an acquisition strategy change was made to maintain launch 

and launch-service capabilities for the Atlas and Delta, under a firm, fixed-price EELV launch services contract. This 

contract provides for a critical mass of sustaining engineering and launch production personnel, even when the launch 

tempo is low.

The DoD (Air Force) indicates that it is technically feasible 

to human-rate the EELV systems, as verified for the Committee by an independent Aerospace Corporation study. In 

doing so, there are several areas that must be addressed. 

These include:

 • Production Facilities – United Launch Alliance is currently consolidating its manufacturing capabilities in 

Decatur, Alabama. The possibility of human-rating the 

EELV systems may add complexity to the planning for 

this consolidation, though the Committee notes that 

United Launch Alliance has the experience and motivation to mitigate any production conflicts.

 • Launch Processing - The Aerospace study commissioned 

by NASA on Human Rating the Delta IV Heavy informed 

the Independent Assessment of Launch System Alternatives conducted for the Committee. The study on human 

rating the Delta IV heavy presented several options to 

minimize conflict between civil and national security 

space launch demands. The Aerospace options include 

the possibility of utilizing the Orbiter Processing Facility 

and Space Launch Complex 39 at the Kennedy Space 

Center for processing a first-stage human-rated EELV. 

Such options need to be further evaluated.

 • Cost – The increased production rates stemming from 

both a human-rated EELV and the national security systems variant of EELV should have a positive effect on 

United Launch Alliance hardware costs and reliability, 

as well as on the United Launch Alliance vendor industrial base. A more efficient procurement, surveillance, 

and mission assurance program should benefit both DoD 

and NASA programs. Further, the implementation of a 

human-rated EELV could accelerate the planned transition to a common upper stage for the Delta IV and Atlas 

V EELVs. Notwithstanding the cost opportunities, the 

implementation of a human-related EELV does introduce 

changes in the existing EELV baseline program. Therefore, a comprehensive management plan and structure, 

with clearly defined responsibilities, authorities and accountabilities, must be formulated if this option is pursued. A similar approach would be required for launch 

scheduling.

 • Industrial Base – If a decision is made to human-rate the 

EELV systems and NASA were to abandon the Ares I 

system but retain the Ares V heavy-launch capability, the 

solid rocket motor industrial base would need to be sustained until the Ares V generated demand. The DoD may 

have to consider support to the solid rocket motor industrial base in recognition of both civil and NSS needs. If 

both the Ares I and Ares V programs were abandoned, a 

detailed civil and military analysis would need to be accomplished to ascertain the interdependence of technical 

and production capabilities between large solid rocket 

motors that are needed to support the nation’s strategic 

strike arsenals and the large segmented solid-rocket motors supporting human-rated systems for NASA.

FINDINGS ON PARTNERSHIPS

 International partnerships: The U.S. can lead a bold new 

international effort in the human exploration of space. If 

international partners are actively engaged, including on 

the “critical path” to success, there could be substantial 

benefit to foreign relations, and more overall resources 

could become available. 

 National security space: A desirable level of synergy between civil space efforts and national security space efforts 

should be reached, taking into account the efficient sharing 

of resources to develop high-value components, as well as 

the potential challenges in joint management of programs 

and reliance on a single family of launch vehicles in a class 

(for example, heavy lift).
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No carefully considered human spaceflight plan, even 

when promulgated with the best intentions, is likely to 

produce a successful outcome unless certain principles 

are embraced in its formulation and execution. Some of 

the more important of these principles, generally derived 

from hard-earned experience, are summarized in this final 

chapter of the report. While not explicitly tasked to offer 

such observations, the Committee believes that it would be 

negligent in its duty were it not to do so.

n 9.1 ESTABLISHING GOALS

Planning a human spaceflight program should start with 

agreement about the goals to be accomplished by that 

program—that is, agreement about its raison d’être, not 

about which object in space to visit. Too often in the past, 

planning the human spaceflight program has begun with 

“where” rather than “why.” This is undoubtedly at least 

in part attributable to the fact that many of the benefits of 

human spaceflight are intangible (e.g., the positive impact 

the Apollo 11 landing had during a time of great tribulation for America). But this makes such intangible benefits 

and activities no less significant—witness the importance 

assigned to great literature, music and art in our nation’s 

history. 

n 9.2 MATCHING RESOURCES AND 

GOALS

Perhaps the greatest contributor to risk in the space program, both human and financial, is seeking to accomplish 

extraordinarily difficult tasks with resources inconsistent 

with the demands of those tasks. This has undoubtedly 

been the greatest management challenge faced by NASA 

in recent decades—even given the magnitude of technological challenges it has confronted. Consider the Constellation Program as a case in point. While it is not clear to 

the Committee what exactly was the official status of the 

funding profile NASA assumed in planning the program—

there are differing views on the subject—it is clear that 

the amounts are smaller today by about one-third. It is 

also clear that when initiating decades-long projects of a 

demanding technical nature, some baseline funding profile 

needs to be agreed upon and sustained to the greatest extent practicable. 

In the Constellation Program, the estimated cost of the 

Ares I launch vehicle development increased as NASA 

determined that the original plan to use the Space Shuttle 

main engines on the Ares I upper stage would be too costly, 

in part due to the need to add self-start. But the replacement engine had less thrust and inferior fuel economy, so 

the first-stage solid rockets had to be modified to provide 

more total impulse. This in turn contributed to a vibration 

phenomenon, the correction of which has yet to be fully 

demonstrated. This is the nature of complex development 

programs—with budgets that are far more likely to decrease 

than increase.

Complicating matters further, insofar as the Constellation 

Program is concerned, this Committee has concluded that 

the Shuttle Program will almost inevitably extend into FY 

2011 in order to fly the existing manifest (the extension 

largely attributable to safety considerations), and that there 

are strong arguments for the extension of the International 

Space Station for another five years beyond the existing 

plan. These actions, if implemented, place demands of another $1.1 billion and $13.7 billion, respectively, on the 

NASA budget. In addition, adequate funds must eventually be provided to safely de-orbit the ISS—funds that were 

not allotted in the current or original program plans.

Shrinking budgets and inadequate reserves—the latter not 

only in dollars but also in time and technology—are a formula for almost certain failure in human spaceflight. If resources are not available to match established goals, new 

goals need to be adopted. Simply extending existing ambitious programs “to fit the money” is seldom a solution to the 

resource dilemma. The impact of fixed costs and technological obsolescence soon overwhelms any such strategy. In 

Concluding Observations 

Chapter 9.0
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the Committee’s travels, it encountered widespread support 

for this policy of realism—although it is likely that most 

proponents were thinking of having more money, not less 

program. Should the latter turn out to be the case, much of 

that conviction is likely to vanish.

In the case of NASA, one result of this dilemma is that 

in order to pursue major new programs, existing programs 

have had to be terminated, sometimes prematurely. Thus, 

the demise of the Space Shuttle and the birth of “the gap.” 

Unless recognized and dealt with, this pattern will continue. When the ISS is eventually retired, will NASA have 

the capability to pursue exploration beyond low-Earth orbit, or will there be still another gap? When a human-rated 

heavy-lift vehicle is ready, will lunar systems be available? 

This is the fundamental conundrum of the NASA budget. 

Continuation of the prevailing program execution practices 

(i.e., high fixed cost and high overhead), together with flat 

budgets, virtually guarantees the creation of additional new 

gaps in the years ahead. Programs need to be planned, 

budgeted and executed so that development and operations 

can proceed in a phased, somewhat overlapping manner.

An additional action that would help alleviate the gap phenomenon is to reenergize NASA’s space technology program, an important effort that has significantly atrophied 

over the years. The role of such a program is to develop 

advanced components (for example, new liquid rocket engines) that can later be incorporated into major systems. 

Developing components concurrently with, or as a part 

of, major system undertakings is a very costly practice. A 

technology development program closely coordinated with 

major ongoing programs, but conducted independently of 

them, is preferable.

n 9.3 NASA MANAGEMENT CHALLENGES

In planning to reach these lofty objectives with constrained 

resources, the question arises how NASA might organize to 

explore. The NASA Administrator, who has been assigned 

responsibility for the management of NASA, needs to be 

given the authority to manage NASA. This includes the 

ability to restructure resources, including workforce and 

facilities, to meet mission needs. Likewise, managers of 

programs need clear lines of responsibility and authority. 

Management of unprecedented and complex international 

technological developments is particularly challenging, 

and even the best-managed human spaceflight programs 

will encounter developmental problems. Such activities 

must be adequately funded, including reserves to account 

for the unforeseen and unforeseeable. Good management 

is especially difficult when funds cannot be moved from 

one human spaceflight budget line to another, and where 

new funds can ordinarily be obtained only after a two-year 

budgetary delay (if at all). In short, NASA should be given 

the flexibility allowed under the law to acquire and manage 

its programs.

Fixed overhead and carrying costs at NASA are currently 

helping to undermine what might be accomplished in new 

space endeavors. A significant fraction of what appear to 

be program-related costs in fact cover fixed and carrying 

costs of employees, facilities and, in some cases, contractors. This reality affects NASA in several ways. When a 

program such as the Shuttle is terminated, not all of the 

program funds actually become available to new programs. 

In fact, the fixed costs often simply move to the new program, where they continue to accumulate. When discretionary resources comprise a limited portion of overall resources, even modest program disruptions can have greatly 

magnified impacts.

Significant space achievements require continuity of support over many years. One way to assure that no successes 

are achieved is to continually introduce change. Changes 

to ongoing programs should be made only for compelling 

reasons. NASA and its human spaceflight program are in 

need of stability, having been redirected several times in the 

last decade. On the other hand, decisions about the future 

should be made by assessing marginal costs and marginal 

benefits. Sunk costs can never be used as a reason not to 

change. The nation should adopt a long-term strategy for 

human spaceflight, and changes should be made only for 

truly compelling reasons. This report describes the advantages and disadvantages of each program option offered. 

The determination of whether, in balance, these exceed the 

“compelling reason” threshold is, of course, the essence of 

making a decision with regard to the future of the human 

spaceflight program.

There is an often-overlooked but vitally important part 

of the human spaceflight program that takes place here 

on Earth. This includes the contributions of the myriad 

engineers, technicians, scientists and other personnel who 

work in NASA and industry. As Buzz Aldrin famously 

said, “It’s amazing what one person can do, along with 

10,000 friends.” Special attention needs to be devoted 

to assuring the vitality of those portions of the workforce 

that represent critical and perishable skills that are unique 

to the space program. One example is the design and 

manufacturing of very large, solid-propellant motors. At 

the same time, it is demeaning to NASA’s professionalism 

to treat the human spaceflight effort as a “jobs” program. 

Only a modest fraction of jobs generally fits the “critical, 

perishable and unique” criterion. The NASA Administrator needs to be given the authority to tailor the size of the 

NASA workforce and the number of Centers employing 

that workforce to match foreseeable needs, much as is 

routinely done in the private sector under the pressure of 

competition. For example, when the end of the Cold War 

changed the role of the aerospace industry, some 640,000 

jobs were terminated. Work should be allocated among 

centers to reflect their legitimate ability to contribute to 

the tasks to be performed, not simply to maintain a fixed 

workforce.

NASA’s relationship with the private sector requires particularly thoughtful attention. The two entities should not be 

in competition. NASA is generally at its best when innovating, creating and managing challenging new projects—

not when its talents are devoted to more routine functions. 

Industry is generally at its best when it is developing, constructing and operating systems. 
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n 9.4 SYSTEMS ENGINEERING

If NASA is to successfully execute the complex undertakings to which it aspires, it must maintain a world-class systems engineering capability, a capability that this and other 

reviews have deemed to be marginal in its current embodiment. The dilemma is that the best systems engineers are 

often those with a great deal of experience—“scar tissue,” 

as it is often called by those in the aerospace industry. But 

how can one get scar tissue if one is confined to studying, 

analyzing and overseeing the work of others? The answer, 

by and large, is that one cannot.

One of NASA’s answers to this dilemma—which has generated criticism in the past—has been to assume responsibility for developing selected major items of hardware 

internally (e.g., the Ares I upper stage). This of course 

places the institution in the hazardous position of serving 

at once as judge, jury and potential defendant, as well as 

being in competition with those it manages in other arenas. Thus, NASA finds itself in the position of designing 

hardware, the engineering drawings for which are being 

produced by subcontractors to NASA to be handed over 

to a prime contractor to produce. This sort of formulation 

warrants exceptionally careful monitoring: it is fraught 

with opportunities for managerial conflict and technical 

incompatibility.

A preferred approach for NASA to acquire a strengthened 

systems engineering capability would be to encourage, or 

at least permit, the movement of particularly talented individuals back and forth between government and industry, 

as often occurred during the Apollo Program. This, however, is now discouraged or even precluded by today’s government personnel policies (e.g., the long time needed for 

hiring, well-intentioned but prohibitive conflict of interest 

policies, etc.). Given this circumstance, the Committee 

sees no ideal solution for maintaining a strong systems engineering capability at NASA. Perhaps the best among a 

generally limited array of choices is for NASA occasionally 

to take direct responsibility for relatively modest pieces of 

hardware, a responsibility that would not include making 

or subcontracting engineering or shop drawings for major 

items to be produced by others. It is noteworthy that the 

technology development program cited elsewhere in this 

report could be an effective training ground for systems 

engineers (as well as program managers), all while maintaining risk at a manageable level. 

n 9.5 PROCURING SYSTEMS

The Committee has examined various future NASA system options and has observed that in many instances, one 

of the more significant discriminators in development and 

operations costs is neither what NASA procures nor who 

supplies it—but rather how NASA procures and operates a 

system. The way NASA specifies, acquires, and uses systems; the tools NASA uses to manage its workforce; and 

the agency’s authority to make purchase commitments: all 

have a very large impact on what NASA can achieve for a 

given budget.

Currently, NASA labors under many restrictions and practices that impair its ability to make effective use of the nation’s industrial base. For example:

• NASA is commonly not allowed to change the size 

and composition of its workforce or facilities, which 

limits its ability to save money through the purchase 

of commercially available products.

• NASA has limited ability to shift funds between related projects to adapt to technical challenges without a protracted approval process.

• NASA is not permitted to make loan guarantees or 

employ other mechanisms by which it could create 

a market for commercial providers that might otherwise invest private funds in meeting some of NASA’s 

needs. (The Department of Defense has procurement 

rules that allow this.) For example, NASA could very 

likely acquire propellant depots by making a “bankable” commitment to purchase propellant from such 

a depot; but depending on a “promise” from NASA 

today would almost certainly not be viewed as a reasonable risk by private investors.

• NASA is expected to undertake long-term projects 

with little hope of budget stability.

With regard to human spaceflight, it is the Committee’s 

view that NASA can and should be the source of:

• Research and technology

• Technology maturation

• System requirements

• Systems architecture

• Procurement oversight

• Exploration operations

• Expensive, multiple-user facilities

NASA generally should not be its own supplier. Numerous 

studies have shown that any organization, public or private, 

that is its own supplier lacks much of the incentive to deliver 

the most cost-efficient product. Today NASA has many options available to procure systems innovatively. These include (but are not limited to): commercial purchases; Space 

Act agreements; COTS-like cost-sharing agreements; prizes 

for innovative technologies; and others.

Determining the requirements for an engineering project 

while it is being built inevitably leads to a very expensive 

result. Requirements should be clearly established prior to 

beginning engineering development. Work that contains 

significant risk or for which scope cannot be accurately defined is generally best performed under cost-reimbursable 

contracts. Work with scope that can be accurately defined 

should generally be conducted under fixed-price contracts. 
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The Committee is convinced that NASA can substantially 

increase the opportunities for entrepreneurial, commercial 

involvement in its space programs by more aggressively 

utilizing the commercial authorities already granted to the 

agency, and by adopting benchmarks in commercial practices utilized in other federal agencies.

n 9.6 MANAGING THE BALANCE OF 

HUMAN AND ROBOTIC SPACEFLIGHT

Although the Committee was tasked only to address the human spaceflight program, including robotic missions that are 

specifically encompassed within that program, it is appropriate to comment about the role and synergy of human and robotic exploration as a whole. The Committee believes that 

America is best served by a complementary and balanced 

space program involving both a robotic component and a human component. The robotic portion is often but not exclusively associated with science missions. Without a strong and 

sustainable science program—the means of acquiring fundamental new knowledge—any space program would be hollow. 

The same can be said of the absence of a human spaceflight 

program. Humans in space, on new and exciting missions, 

inspire the public. But so do the spectacular accomplishments 

of such robotic spacecraft as the Hubble Space Telescope, the 

Mars rovers, the Earth Observing System satellites, or the 

twin Voyager spacecraft that are poised to reach interstellar 

space. This is to suggest that both the human spaceflight program and the science program are key parts of a great nation’s 

space portfolio. 

Needless to say, robotic spaceflight should play an important 

role in the human spaceflight program itself, reconnoitering 

scientifically important destinations, surveying future landing 

sites, providing logistical support and more. Correspondingly, 

humans can play an important role in science missions, particularly in field geology, exploration, and the maintenance and 

enhancement of robotic systems in space. (See Figure 9.6-1.) 

It is in the interest of both science and human spaceflight that 

a credible and well-rationalized strategy of coordination between the two types of pursuit be developed—without forcing 

unwarranted intermingling in areas where each would better 

proceed on its own.

Robotic activity in space is generally much less costly than 

human activity and therefore offers a major inherent advantage. Of even greater importance, it does not place human 

lives at risk. Astronauts provide their greatest advantage in 

the most complex or novel environments or circumstances. 

This will be the case in the exploration of planetary surfaces 

and in repair or servicing missions of the type undertaken for 

the Hubble Space Telescope’s primary mirror. In contrast, the 

value of humans in space is usually at its minimum when they 

are employed transporting cargo. The bottom line is that there 

are important roles to be played by both humans and robots 

in space, and America should strive to maintain a balanced 

program incorporating the best of both kinds of explorers.

That said, there are nonetheless inevitable conflicts—

conflicts that arise from the competition among programs for resources, particularly financial resources. It 

is therefore of the utmost 

importance, if balance is to 

be maintained, that neither 

the human program nor the 

robotic spaceflight program 

be permitted to cannibalize the 

other. This has been a significant 

concern in the past, particularly 

given the size of the human spaceflight program. Difficulties in the 

human space program too often 

swallowed resources that had 

been planned for the robotic program (as well as for aeronautics 

and space technology). Robotics 

are generally, although not exclusively, considered to be of greater 

interest to the scientific community. It is essential that budgetary

firewalls be built between these 

two broad categories of activity. 

In the case of the International 

Space Station, one firewall should 

be the establishment of an organizational entity to select endeavors 

to be pursued aboard the Space 

Station. Without such a mechanism, turmoil is assured and program balance endangered.

Figure 9.6-1. Experience with the Hubble Space Telescope (shown here being placed onto orbit) and Space Shuttle 

offers an example of the potential synergy of human and robotic spaceflight. Source: NASA (STS-31 Mission 

Onboard photograph)
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FINDINGS

The right mission and the right size: NASA’s budget 

should match its mission and goals. Further, NASA 

should be given the ability to shape its organization and 

infrastructure accordingly, while maintaining facilities 

deemed to be of national importance. 

Robotic program coordination: The robotic and human 

explorations of space should be synergistic, both at the 

program level (e.g., science probes to Mars and humans 

to Mars) and at the operational level (e.g., humans with 

robotic assistants on a spacewalk). Without burdening 

the space science budget or influencing its process of 

peer-based selection of science missions, NASA should 

proceed to develop the robotic component of its human 

exploration program. 

Management authority: The NASA Administrator and 

program managers need to be given the responsibility 

and authority to manage their endeavors. This includes 

providing flexibility to tailor resources, including people, 

facilities and funds, to fit mission needs.

Stability in programs: In the most recent decade, NASA 

has spent about 80 percent of the GDP-deflated budget 

that it had in the decade of Apollo. Recurring budget ambiguities and reductions and redirections of policy, coupled with the high fixed-cost structure of NASA, have not 

optimized the return on that investment. 

Right job for the NASA workforce: NASA has a talented (but aging) workforce. NASA should focus on the 

challenging, long-term tasks of technology development, 

cutting-edge new concepts, system architecture development, requirements definition, and oversight of the development and operation of systems. 

Fixed operating costs at NASA: There are significant 

fixed costs in the NASA system. Given that reality, reducing the funding profile much below the optimum for the 

development of a given program has an amplified effect of 

delaying benefits and increasing total program cost. 

NASA’s fundamental budgetary conundrum: Within the 

current structure of the budget, NASA essentially has the 

resources either to build a major new system or to operate 

one, but not to do both. This is the root cause of the gap in 

capability of launching crew to low-Earth orbit under the 

current budget and will likely be the source of other gaps 

in the future.

Commercial involvement in exploration: NASA has considerable flexibility in its acquisition activities due to special provisions of the Space Act. NASA should exploit 

these provisions whenever appropriate, and in general encourage more engagement by commercial providers, allocating to them tasks and responsibilities that are consistent 

with their strengths.

n 9.7 CONCLUDING SUMMARY

NASA is the most accomplished space organization in the 

world. Its human spaceflight activities are nonetheless at 

a tipping point, primarily due to a mismatch of goals and 

resources. Either additional funds need to be made available or a far more modest program involving little or no 

exploration needs to be adopted. Various options can be 

identified that offer exciting and worthwhile opportunities 

for the human exploration of space if appropriate funds can 

be made available. Such funds can be considerably leveraged by having NASA attack its overhead costs and change 

some of its traditional ways of conducting its affairs—and 

by giving its management the authority to bring about such 

changes. The American public can take pride in NASA’s 

past accomplishments; the opportunity now exists to provide for the future human spaceflight program worthy of a 

great nation.
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Committee Member

Biographies

Appendix A

Norman R. Augustine

Norman R. Augustine graduated from Princeton University where he was awarded Bachelor’s and 

Master’s degrees in aeronautical engineering and was elected to Phi Beta Kappa, Tau Beta Pi and 

Sigma Xi. He is a retired Chairman and CEO of Lockheed Martin Corporation and has served as Assistant Secretary, Under Secretary and Acting Secretary of the Army and as an Assistant Director of 

Defense Research and Engineering. He has served as Chairman of the National Academy of Engineering, the Defense Science Board and the Aerospace Industries Association, and as President of the 

American Institute of Aeronautics and Astronautics. A 16-year member of the President’s Council 

of Advisors on Science and Technology, Mr. Augustine chaired the Aeronautics Committee of the 

NASA Advisory Council and served on the Air Force Scientific Advisory Board. He is an Honorary 

Fellow of the American Institute of Aeronautics and Astronautics and a Fellow of the American Society of Mechanical Engineers, the Institute of Electrical and Electronic Engineers and the International Academy of Astronautics. A former member of the faculty of the Princeton University Department of Mechanical and Aerospace Engineering, he has received the National Medal of Technology, 

awarded by the President of the United States, and holds 23 honorary degrees.

Wanda M. Austin

Wanda M. Austin earned a Bachelor’s Degree in mathematics from Franklin & Marshall College, 

Master’s degrees in systems engineering and mathematics from the University of Pittsburgh, and a 

Ph.D. in systems engineering from the University of Southern California. She is President and CEO 

of The Aerospace Corporation, a leading architect for the nation’s national security space programs. 

She is a member of the National Academy of Engineering, a Fellow of the American Institute of 

Aeronautics and Astronautics, and a member of the International Academy of Astronautics. She was 

a member of the National Research Council’s Committee on the Rationale and Goals of the U.S. 

Civil Space Program. She previously served on the NASA Advisory Council and the NASA Aerospace Safety Advisory Panel. Dr. Austin has received the National Intelligence Medallion for Meritorious Service, the Air Force Scroll of Achievement, the National Reconnaissance Office Gold Medal, 

the U.S. Air Force Meritorious Civilian Service Medal and the NASA Pubic Service Medal. She was 

inducted into the “Women in Technology International” Hall of Fame, and she has been named the 

2009 Black Engineer of the Year. Dr. Austin is internationally recognized for her work in satellite and 

payload system acquisition, systems engineering and system simulation. 

MEMBERS LISTED ALPHABETICALLY

CHAIRMAN
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Bohdan I. Bejmuk

Bohdan (Bo) I. Bejmuk is an aerospace consultant with in-depth knowledge of space systems 

and launch vehicles. He is Chairman of the Standing Review Board for the NASA Constellation 

Program. Mr. Bejmuk retired from the Boeing Company in 2006, where he was the Space Shuttle 

Orbiter Program Director, responsible for all Orbiter engineering efforts. During Space Shuttle development and early operations, he served as Program Manager for system engineering and integration. On Sea Launch, an international joint venture, he was the Executive Vice President and Chief 

Engineer, directing all aspects of the company’s development and leading a multinational workforce 

of several thousand engineers and shipyard workers. After completion of Sea Launch development, 

he was manager of operations at the California home port and at the Pacific Ocean launch region. 

Mr. Bejmuk also served in numerous senior positions at Rockwell International and Martin Marietta. He received a B.S. and M.S. in mechanical engineering from the University of Colorado. A 

member of the International Academy of Astronautics, he received the Lloyd V. Berkner Award, the 

Aviation Week Laurels Award, the National Public Service Medal, awarded twice by NASA, and 

the Rockwell International Presidents Award. He was also recognized as an Eminent Engineer by 

the California Institute of Technology. 

Leroy Chiao

In 15 years with NASA, astronaut Leroy Chiao logged more than 229 days in space, including 36 

hours in extra-vehicular activity. A veteran of four space missions, Dr. Chiao most recently served 

as Commander and NASA Science Officer of Expedition 10 aboard the International Space Station. He was a Space Shuttle Mission Specialist and also certified as a copilot of the Russian Soyuz 

spacecraft. Since leaving NASA in 2005, Dr. Chiao has worked with entrepreneurial business 

ventures in the U.S., China, Japan and Russia. Among these, he is Executive Vice President and a 

Director of Excalibur Almaz, a private manned spaceflight company. He serves as Chairman of the 

National Space Biomedical Research Institute User Panel and advisor and spokesman for the Heinlein Prize Trust. Dr. Chiao is a Director of the Challenger Center for Space Science Education and 

of the Committee of 100, an organization of prominent U.S. citizens of Chinese descent. Dr. Chiao 

earned a B.S. from the University of California at Berkeley and his M.S. and Ph.D. at the University 

of California at Santa Barbara, all in chemical engineering. Prior to joining NASA, he worked as a 

research engineer at Hexcel Corp. and then at the Lawrence Livermore National Laboratory.

Christopher Chyba

Christopher Chyba is Professor of Astrophysical Sciences and International Affairs at Princeton 

University. He previously was Associate Professor of Geological and Environmental Sciences at 

Stanford University, and held the Carl Sagan Chair at the SETI Institute. Dr. Chyba served at the 

White House from 1993 to 1995, entering as a White House Fellow on the National Security Council staff, and then in the Office of Science and Technology Policy. In 1996, Dr. Chyba received the 

Presidential Early Career Award for Scientists and Engineers. In 2001, he was named a MacArthur 

Fellow for his work in both international security and planetary science. Dr. Chyba serves on the 

National Academy of Sciences Committee on International Security and Arms Control and is past 

Chair of the National Research Council Committee on Preventing the Forward Contamination of 

Mars. He has served on NASA’s Space Science Advisory Committee, for which he chaired the Solar 

System Exploration Subcommittee, and he chaired the Science Definition Team for NASA’s Europa 

Orbiter mission. A physics graduate of Swarthmore College, Dr. Chyba holds an M.Phil. from Cambridge University, where he was a Marshall Scholar, and a Ph.D. in astronomy and space sciences 

from Cornell University. In 2009, President Obama appointed him to the President’s Council of 

Advisors on Science and Technology. 

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Edward F. Crawley

Edward F. Crawley is the Ford Professor of Engineering at MIT, and is a Professor of Aeronautics 

and Astronautics and of Engineering Systems. He received an S.B. and Sc.D. in aerospace engineering from MIT, and he holds an honorary Doctorate from Chalmers University. He has served as 

the Head of the MIT Department of Aeronautics and Astronautics, the Director of the Cambridge – 

MIT Institute, and the Director of the Bernard M. Gordon – MIT Engineering Leadership Program. 

His research has focused on the domain of architecture, design and decision support in complex 

technical systems. Dr. Crawley is a Fellow of the AIAA and the Royal Aeronautical Society (UK), 

and is a member of three national academies of engineering: in Sweden, the UK and the United 

States. Dr. Crawley served as Chairman of the NASA Technology and Commercialization Advisory Committee, and he was a member of the 1993 Presidential Advisory Committee on the Space 

Station Redesign. He recently co-chaired the committee of the NRC reviewing the NASA Exploration Technology Development Program. He served as a lecturer at the Moscow Aviation Institute, 

and as a Guest Professor at Tsinghua University in Beijing. In 1980 he was a finalist in the NASA 

astronaut selection. He has founded three entrepreneurial companies and currently sits on several 

corporate boards.

Jeff Greason

Jeff Greason, CEO of XCOR Aerospace, has 18 years of experience managing innovative, leadingedge technical project teams at XCOR Aerospace, Rotary Rocket and Intel Corporation. At XCOR, he 

leads a team that designs, builds and operates long-life, low-cost, reusable rocket engines and rocketpowered vehicles for government and private markets. During his work at XCOR, Mr. Greason has 

had final go/no-go authority on more than 20 manned rocket flights and hundreds of rocket engine 

tests. The company has won and successfully completed government contracts for NASA, the U.S. Air 

Force and DARPA. A recognized expert in reusable launch vehicle regulations of the Federal Aviation 

Administration’s Office of Commercial Space Transportation, he testified before the joint House/Senate subcommittee hearings on Commercial Human Spaceflight, which led to the Commercial Space 

Launch Amendments Act of 2004. He serves on the Commercial Space Transportation Advisory 

Committee (COMSTAC) and is a co-founder and Vice Chairman of the Personal Spaceflight Federation, a trade association for innovative launch companies. Mr. Greason was cited by Time magazine 

in 2001 as one of the “Inventors of the Year” for his team’s work on the EZ-Rocket. At Intel, he developed leading-edge processor design techniques and received the coveted Intel Achievement Award. 

He holds 18 U.S. patents and graduated with honors from the California Institute of Technology.

Charles F. Kennel

Charles F. Kennel earned his A.B. at Harvard University and his Ph.D at Princeton University, 

studying space plasma physics and astrophysics. After three years at the Avco-Everett Research 

Laboratory, he joined the UCLA Physics Department, eventually chairing the department, and TRW 

Systems. He served as: NASA Associate Administrator for Mission to Planet Earth; UCLA Executive Vice Chancellor; Director of the Scripps Institution of Oceanography; and Vice Chancellor 

of Marine Sciences, University of California, San Diego. Dr. Kennel is a member of the National 

Academy of Sciences, the American Academy of Arts and Sciences, the American Philosophical 

Society and the International Academy of Astronautics. He has chaired the National Academy’s Solar and Space Physics, Global Change Research, Fusion Sciences, and Beyond Einstein committees, 

as well as its Board on Physics and Astronomy. He was a member of the Pew Oceans Commission 

and both member and Chair of the NASA Advisory Council. He now chairs the California Council on Science and Technology and the NRC Space Studies Board, and is a Board member of the 

Bermuda Institute of Ocean Sciences. Dr. Kennel has received prizes from the American Physical 

Society, the European Geophysical Union and the Italian Academy, both the NASA Distinguished 

Service and Distinguished Public Service medals, and an honorary degree from the University of 

Alabama.

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Lester L. Lyles

Lester L. Lyles, a retired U.S. Air Force four-star general, graduated from Howard University with 

a Bachelor’s Degree in mechanical engineering. He began his 35-year career in the Air Force as 

a space vehicle engineer, after earning a Masters Degree in mechanical/nuclear engineering from 

New Mexico State University. Following the Shuttle Challenger accident, General Lyles directed 

the recovery operations conducted by the Air Force Space-Launch Systems Office. For this effort, 

the National Space Club recognized him as the Astronautics Engineer of the Year. General Lyles 

commanded the Ogden Air Logistics Center and the Space and Missile Systems Center, and he 

directed the Ballistic Missile Defense Organization. He served as the 27th Vice Chief of Staff of 

the U.S. Air Force and Commander of the Air Force Materiel Command. He served as a member 

of the President’s Commission on the Implementation of the U.S. Space Exploration Vision, and 

he chaired the National Research Council study on the Rationale and Goals of the U.S. Civil Space 

Program. He chairs the Aeronautics Committee of the NASA Advisory Council, and he is the Vice 

Chair of the Defense Science Board. His numerous honors include the Black Engineer of the Year 

Lifetime Achievement Award, as well as two honorary doctoral degrees.

Sally K. Ride

Sally K. Ride earned a B.S. in physics and B.A. in English, followed by her M.S. and Ph.D. in 

physics, all at Stanford University. She is a Professor of Physics (Emerita) at the University of 

California, San Diego, and the CEO of Imaginary Lines, Inc. Dr. Ride, the first American woman 

in space, was an astronaut for more than 10 years, flying on two Space Shuttle missions. She was 

NASA’s first Director of Exploration and first Director of Strategic Planning, and she is the only 

person to serve on both the Space Shuttle Challenger and Columbia accident investigation boards. 

A Fellow of the American Physical Society and Board Member of both the California Institute of 

Technology and the Aerospace Corporation, she has also served on the Space Studies Board, the 

Board of the Congressional Office of Technology Assessment, the President’s Commission on 

White House Fellows and the President’s Committee of Advisors on Science and Technology. Dr. 

Ride has received the Jefferson Award for Public Service, the Von Braun Award and the Lindbergh 

Eagle, and she has twice been awarded the National Spaceflight Medal. She is a member of the 

Aviation Hall of Fame and the Astronaut Hall of Fame. 

MEMBERS LISTED ALPHABETICALLY
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Designated Federal Official/

Executive Director

Philip McAlister, Special Assistant for Program Analysis, 

NASA Headquarters

NASA

NASA Chief of Staff 

George Whitesides, NASA Headquarters

NASA Review Team

Study Team 

Dr. W. Michael Hawes, HQ - Team Lead

Brent Jett, JSC - Deputy

Tricia K. Mack, HQ - Executive Officer

Program Risk Assessment Team 

David Radzanowski, HQ - Team Lead

Frank H. Bauer, HQ

Glenn Butts, KSC

Melek Ferrara, SAIC

Eameal Holstien, JSC

Charlie Hunt, HQ

Mahmoud R. Naderi, MSFC

Josh Manning, HQ

Stanley McCaulley, MSFC

Carey McCleskey, KSC

Arlene Moore, HQ

Krista Paquin, HQ

Tom Parkey, GRC

Frank A. (Andy) Prince, MSFC

Patrick Scheuermann, SSC

Daniel Schumacher, MSFC

Robert Sefcik, GRC

Christian Smart, Ph.D., SAIC

Edgar Zapata, KSC

Engineering Analysis

Ralph Roe, HQ - Team Lead

Mike Kirsch, LaRC - Deputy

Dawn Schaible, LaRC – Deputy

Reginald Alexander, MSFC

John D. Baker, JPL

Keith Brock, SSC

William M. Cirillo, LaRC

Scott Colloredo, KSC

John Connolly, JSC

Terri Derby, ATK Space Systems

Bret Drake, JSC

Dennis Hines, DFRC

Eric Isaac, GSFC

Michael A. Johnson, GSFC

Kent Joosten, JSC

Dave Korsmeyer, ARC

Steven Labbe, JSC

Rick Manella, GRC

Roland Martinez, JSC

Paul McConnaughey, MSFC

Pat Troutman, LaRC 

Engineering Analysis Support

Dan Adamo (ret’d), JSC

Rob Adams, MSFC

Faye Allen, Futron Corp.

David Anderson, MSFC

Mark Andraschko, LaRC

Michael Baine, JSC

Stanley Borowski, GRC

Robert Bruce, SSC

Sue Burns, JSC

Robert Cataldo, GRC

Grant R. Cates, Ph.D., SAIC

David Chato, GRC

Robert Christy, GRC

Kristine Collins, LaRC

John Cornwell, JSC

Nicholas Cummings, KSC

Dominic DePasquale, SEI

Ian Dux, GRC

Kevin Earle, LaRC

Walt Engelund, LaRC

Committee Staff

Appendix B
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Engineering Analysis Support (cont)

Robert Falck, GRC

James Fincannon, GRC

Brad Flick, DFRC

Joseph R. Fragola, Valador Inc

Joseph Gaby, ASRC

Ricardo Galan, SAIC

Dr. David M Garza, Aerospace

Leon Gefert, GRC

James Geffre, JSC

Justin Gelito, SAIC

Patrick George, GRC

John C. Goble, Aerospace

Reynaldo Gomez, JSC

Kandyce Goodliff, LaRC

Joe Grady, GRC

Brand Griffin, Gray Research

John Gruener, JSC

Gene Grush, JSC

Kurt Hack, GRC

Leon Hastings, MSFC

Edward Henderson, JSC

Stephen Hoffman, SAIC

Dr. Robert L. Howard, Jr., JSC

A. Scott Howe, JPL

Eric Hurlbert, JSC

Daniel C. Judnick, Aerospace

Kriss Kennedy, JSC

D.R. Komar, LaRC

Larry Kos, MSFC

Rob Landis, ARC

Jeffrey A. Lang, Aerospace

Roger Lepsch, LaRC

Dr. Marcus A. Lobbia, Aerospace

Gaspare Maggio, ISL

Richard Mattingly, JPL

Nicholas E. Martin, Aerospace

Daniel Mazanek, LaRC

Dave McCurdy, ARSC

Melissa L. McGuire, GRC

Pat McRight, MSFC

Raymond (Gabe) Merrill, LaRC

Michael Meyer, GRC

Glenn Miller, JSC

Dr. Inki A. Min, Aerospace

Nathaniel Morgan, LaRC

Jack Mulqueen, MSFC

Tri X. Nguyen, JSC

Steven Oleson, GRC

Tom Packard, Analex Corp.

Bill Pannell, MSFC

Robert Phillips, Futron Corp.

Charles Pierce, MSFC

Blake F. Putney Jr., Valador, Inc.

Shawn Quinn, KSC

David Reeves, LaRC

J.D. Reeves, LaRC

Joe Roche, GRC

Marianne Rudisill, LaRC

Joshua Sams, AMA, Inc.

Rudolph Saucillo, LaRC

Larry Schultz, KSC

Hilary Shyface, AMA, Inc.

Gary Spexarth, JSC

Jonette Stecklein, JSC

Chel Stromgren, SAIC

Phil Sumrall, MSFC

Ted Sweetser, JPL

Ted Talay, JF&A

William Taylor, GRC

Chris Teixeira, SAIC

Andrew Thomas, JSC

Ed Threet, MSFC

Larry Toups, JSC

Stephen Tucker, MSFC

Eugene Ungar, JSC

Timothy Verhey, GRC

Phil Weber, KSC

Robert Werka, MSFC

Charles Whetsel, JPL

Doug Whitehead, JSC

Jeff Woytach, GRC

Strategic Analysis and Collaboration

Tom Cremins, HQ - Team Lead

Dave Bartine, KSC

Dennis Boccippio, MSFC

John Casani, JPL

Doug Comstock, HQ

Jason Derleth, HQ

Karen Feldstein, HQ

Chris Ferguson, JSC

Lee Graham, JSC

Richard B. Leshner, HQ

Neal Newman, HQ

Mark Uhran, HQ

Science and Technology

Michael Meyer, HQ – Team Lead

Ariel Anbar, AZ State University

Dave Beaty, JPL

Francis A. Cucinotta, JSC

Jeffrey R. Davis, JSC

James Head, Brown University

Terri Lomax, NC State University

John Mustard, Brown University

Clive Neal, Univ. of Notre Dame

Edward Semones, JSC

Mark Sykes, Planetary Sci. Inst.

Meenakshi Wadhwa, AZ State Univ.

Programs, Legislative Affairs, Legal Counsel, 

Public Affairs, External Affairs

Susan Burch, HQ

Rebecca Gilchrist, HQ

Bill Hill, HQ

Margaret Kieffer, HQ 

Mary D. Kerwin, HQ

Doc Mirelson, HQ 

Diane Rausch, HQ

Kirk Shireman, JSC

Kathleen Teale, HQ

Astronaut Representatives 

Chris Ferguson, JSC

Don Pettit, JSC

Andy Thomas, JSC
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NASA Television

Fred A. Brown, Team Lead

Allard Beutel, KSC

Cliff Feldman

Mark Hailey 

Cedric Harris 

Bill Hubscher, MSFC

John Malechek 

Bob Moder, MSFC

Anthony Stewart

Jennifer Tharpe, KSC 

Robert Williams

Committee Site Visit Support

Sandra H. Turner MSFC

Patsy H. Fuller, MSFC

Valador, Inc. Support

Donna Connell, Team Lead

Dennis R. Bonilla

Lisa S. Connell

James Convy IV

Kathleen Gallagher

Sandra L. George

Matthew Kohut

Erek Korgan

Stephen F. Spiker

Kelly E. Stocks

Lester A. Reingold

Tate S. Srey

Patricia D. Trenner

Joseph A. Valinotti III

Executive Assistant to Norman R. Augustine

Laura J. Ahlberg

Aerospace Corporation Support

Gary P. Pulliam - Vice President

Matthew J. Hart - Team Lead

John P. Skratt - Team Lead

Dr. Inki A. Min - Team Lead

Debra L. Emmons - Team Lead

Dr. David A. Bearden - Team Lead

David S. Adlis

Joseph A. Aguilar

Dr. Kristina Alemany

Violet Barghe-Sharghi

Stephanie E. Barr

Robert E. Bitten

Garry H. Boggan

John J. Bohner

Daniel W. Bursch

Vincent M. Canales

Dr. Shirin Eftekhardezeh

Debra L. Emmons

Dr. Robert W. Francis

Jonathan P. French

Gregory Fruth

Larcine Gantner

Alisa M. Hawkins

Thanh D. Hoang

Thomas P. Jasin

Ray F. Johnson

Daniel C. Judnick

Randolph L. Kendall

Dr. Robert J. Kinsey

Jeffrey A. Lang

Dr. Tung T. Lam

Glenn W. Law

Dr. Austin S. Lee

Jeffrey R. Lince

Dr. Marcus A. Lobbia

Nicholas E. Martin

John P. Mayberry

Shannon P. McCall

Michael R. Moore

Elisha B. Murrell

Dr. Jon M. Neff

Daniel A. Nigg

Thomas Paige

Jay P. Penn

Dr. Torrey O. Radcliffe

Ernest Y. Robinson

Louis H. Sacks

Felix T. Sasso

Maria E. Sklar

Morgan W. Tam

Paul R. Thompson

E. J. Tomei, Jr.

Dr. Leslie A. Wickman

Justin S. Yoshida

Dr. Albert H. Zimmerman
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This Statement of Task establishes and informs a review to be conducted in support of planning for U.S. human space flight 

activities beyond the retirement of the Space Shuttle. The purpose of this effort is to develop suitable options for consideration by the Administration regarding a human space flight architecture that would: 

• Expedite a new U.S. capability to support utilization of the International Space Station 

• Support missions to the Moon and other destinations beyond low Earth orbit (LEO) 

• Stimulate commercial space flight capability 

• Fit within the current budget profile for NASA exploration activities

 

The review will be led by an independent, blue-ribbon panel of experts who will work closely with a NASA team and will 

report progress on a regular basis to NASA leadership and the Executive Office of the President. This independent review 

will provide options and related information to involved Administration agencies and offices in sufficient time to support an 

August 2009 decision on the way forward. As necessary and appropriate, the team may seek early decisions from the Administration on some of these options. A final report containing the options and supporting analyses from this review also will be 

released. 

Scope 

The review should: 

• Evaluate the status and capabilities of the agency’s current human space flight development program; 

• Evaluate other potential architectures that are capable of supporting the mission areas described above; 

• Evaluate what capabilities and mission scenarios would be enabled by the potential architectures under consideration, including various destinations of value beyond LEO; 

• Consider options to extend International Space Station operations beyond 2016; 

• Examine the appropriate degree of R&D and complementary robotic activities necessary to make human space 

flight activities affordable and productive over the long term; 

• Examine appropriate opportunities for international collaboration; and 

• Not rely upon extending Space Shuttle operations in assessing potential architectures. 

Review of U.S. Human Space Flight Plans 

Statement of Task 

Appendix C
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The review may evaluate architectures that build on current plans, existing launch vehicles and infrastructure, Space Shuttlerelated components and infrastructure, the two Evolved Expendable Launch Vehicle (EELV) families, and emerging capabilities. It may also consider architectures that vary in terms of the capability that would be delivered beyond low Earth orbit 

(e.g., the number of crew and the duration of these missions), while describing the implications of such choices for possible 

mission goals and scenarios. In addition to new analyses required in support of this effort, the review team should consider, 

where appropriate, other studies and reports relating to this subject. 

Evaluation Parameters 

The review should examine potential architectures relative to the following key evaluation 

parameters: 

• Crew (and overall mission) safety; 

• Overall architecture capability (e.g., mission duration, mass delivered to low Earth orbit and other selected destinations, flexibility); 

• Life-cycle costs (including operations costs) through 2020; 

• Development time; 

• Programmatic and technical risk; 

• Potential to spur innovation, encourage competition, and lower the cost of space transportation operations in the 

existing and emerging aerospace industry; 

• Implications for transition from current human space flight operations; 

• Impact on the nation’s industrial base and competitiveness internationally; 

• Potentially expanded opportunities for science; 

• Potential for enhanced international cooperation as appropriate; 

• Potential to enhance sustainability of human space activities;

• Potential for inspiring the nation, and motivating young people to pursue careers in science, technology, engineering and mathematics subjects; 

• Benefit to U.S. Government defense and intelligence space-related capabilities; and 

• Contractual implications. 

Budget 

Budget options considered under the review must address the development of a human space flight architecture, robotic 

spacecraft to support and complement human activities, and R&D to support future activities. The review should assume the 

following 2010-2014 budget profile for these activities: 

Based on the results of this review, the Administration will notify Congress of any needed changes to the FY2010 President’s 

Budget Request. 
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1. Official Designation: Review of U.S. Human Space Flight Plans Committee (“The Committee”)

2. Authority: Having determined that it is in the public interest in connection with the performance of Agency duties 

under law, and in consultation with the U.S. General Services Administration, the NASA Administrator hereby establishes the 

Review of U.S. Human Space Flight Plans Committee pursuant to the Federal Advisory Committee Act (FACA), as amended, 

5 U.S.C. App.

3. Scope and Objectives: The Committee shall conduct an independent review of ongoing U.S. human space flight 

plans and programs, as well as alternatives, to ensure the nation is pursuing the best trajectory for the future of human space 

flight – one that is safe, innovative, affordable, and sustainable. The Committee should aim to identify and characterize 

a range of options that spans the reasonable possibilities for continuation of U.S. human space flight activities beyond 

retirement of the Space Shuttle. The identification and characterization of these options should address the following 

objectives: a) expediting a new U.S. capability to support utilization of the International Space Station (ISS); b) supporting 

missions to the Moon and other destinations beyond low Earth orbit (LEO); c) stimulating commercial space flight capability; 

and d) fitting within the current budget profile for NASA exploration activities.

In addition to the objectives described above, the review should examine the appropriate amount of R&D and complementary 

robotic activities needed to make human space flight activities most productive and affordable over the long term, as well as 

appropriate opportunities for international collaboration. It should also evaluate what capabilities would be enabled by each 

of the potential architectures considered. It should evaluate options for extending International Space Station operations 

beyond 2016.

4. Description of Duties: The Committee will provide advice only.

5. Official to Whom the Committee Reports: The Committee reports to the NASA Administrator and the 

Director of the Office of Science and Technology Policy (OSTP), Executive Office of the President. The Committee will 

submit its report within 120 days of the first meeting of the Committee.

6. Support: The NASA Office of Program Analysis and Evaluation shall provide staff support and operating funds for 

the Committee.

7. Estimated Annual Operating Costs and Staff Years: The operating cost associated with supporting the 

Committee’s functions is estimated to be approximately $3 million, including all direct and indirect expenses. It is estimated 

that approximately 8 full-time equivalents will be required to support the Committee.

8. Designated Federal Officer: The Executive Director of the Committee shall be appointed by the NASA 

Administrator and shall serve as the Designated Federal Official (DFO). The DFO must be either a full-time or a permanent 

part-time employee, who must call, attend, and adjourn committee meetings; approve agendas; maintain required records 

on costs and membership; ensure efficient operations; maintain records for availability to the public; and provide copies of 

committee reports to the NASA Committee Management Officer (CMO) for forwarding to the Congress. 

Charter of the Review of U.S.

Human Space Flight Plans Committee

Appendix D
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9. Estimated Number and Frequency of Meetings: The Committee shall conduct meetings as appropriate at 

various locations throughout the United States. Meetings shall be open to the public unless it is determined that the meeting, 

or a portion of the meeting, will be closed in accordance with the Government in the Sunshine Act.

10. Duration: The Committee will exist for 180 days, unless earlier renewed.

11. Termination: The Committee shall terminate within 60 days after submitting its report.

12. Membership and Designation: The Committee shall consist of members to be appointed by the NASA 

Administrator. The Administrator shall ensure a balanced representation in terms of the points of view represented and 

the functions to be performed. Each member serves at the pleasure of the Administrator. The Committee shall consist 

of approximately 5-10 members. It is anticipated that the members will serve as Special Government Employees for the 

duration of the Committee, renewable at the discretion of the NASA Administrator. The NASA Administrator shall designate 

the chair of the Committee. 

13. Subcommittees: Subcommittees, task forces, and/or work groups may be established by NASA to conduct studies 

and/or fact-finding requiring an effort of limited duration. Such subcommittees, task forces and work groups will report their 

findings and recommendations directly to the Committee. However, if the Committee is terminated, all subcommittees, task 

forces and work groups will also terminate.

14. Recordkeeping: The records of the Committee, formally and informally established subcommittees, or other 

subgroups of the Committee, shall be handled in accordance with General Records Schedule 26, Item 2, or other approved 

agency records disposition schedule. These records shall be available for public inspection and copying, subject to the 

Freedom of Information Act, 5 U.S.C. 552.

15. Charter Filing Date: This charter shall become effective upon the filing of this charter with the appropriate U.S. 

Senate and House of Representatives oversight committees. 

___________________________________ __________________

Christopher J. Scolese Date

NASA Administrator (Acting)
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DATE MEETING

June 9, 2009 Preparatory Meeting (Teleconference) 

June 16, 2009 Preparatory Meeting (Washington, D.C.) 

June 17, 2009 Public Meeting (Washington, D.C.) 

June 18, 2009 Site Visit (Dulles, VA)

June 24-25, 2009 Site Visit (Huntsville and Decatur, AL; and Michoud, LA) 

July 2, 2009 Preparatory Meeting (Teleconference) 

July 8-9, 2009 Site Visit (Hawthorne, CA) and Fact-Finding Meetings 

(El Segundo, CA)

July 14, 2009 Preparatory Meeting (Teleconference) 

July 21-23, 2009 Fact-Finding Meetings (Denver, CO) 

July 28, 2009 Public Meeting (Houston, TX) 

July 29, 2009 Public Meeting (Huntsville, AL) 

July 30, 2009 Public Meeting (Cocoa Beach, FL) 

August 5, 2009 Public Meeting (Washington, D.C.) 

August 5, 2009 Preparatory Meeting (Washington, D.C.) 

August 12, 2009 Preparatory Meeting (Washington, D.C.) 

August 12, 2009 Public Meeting (Washington, D.C.)

October 8, 2009 Public Meeting (Teleconference)

List of Full Committee 

Meetings and Locations

Appendix E
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E.C. “Pete” Aldridge

Buzz Aldrin

Brett Alexander

Reginald Alexander

John D. Baker

Frank H. Bauer

Jeanne L. Becker

James M. Beggs

Dallas Bienhoff

Jack Bullman

Jack O. Burns

Frank Buzzard

Bob Cabana

Elizabeth Cantwell

Frank Chandler

Jim Chilton

Lynn Cline

Mike Coats

Cassie Conley

Doug Cooke

Ed Cortwright

Dick Covey

William M. Cirillo

Steve Creech

Chris Culbert

Danny Davis

Jean-Jacques Dordain

Bret Drake

Joseph Dyer

Antonio Elias 

Bob Ess

Kevin Eveker

Andrew Falcon

Kenneth Ford

Joseph R. Fragola

Louis Friedman

Robert E. Fudickar

Peter Garretson

Michael Gass

Bill Gerstenmaier

Mark Geyer

John Glenn

Mike Gold

Dan Goldin

Michael D. Griffin

Gene Grush

Jim Halsell

Jeff Hanley

Scott Horowitz

Matthew Isakowitz

Anthony Janetos

Tom Jasin

Chip Jones

Tom Jones

Tony Jones

Kent Joosten

John Karas

Mark Kinnersley

D.R. Komar

Dave Korsmeyer

Jeff Kottkamp

Donald Latham

Joo-Jin Lee

Matt Leonard

Dan Lester

Robert Lightfoot

Steve Lindsay

John M. Logsdon

Steve MacLean

Joanne Maguire

Ed Mango

John Marburger

Roland Martinez

James Maser

Steve Metschan

George E. Mueller

Elon Musk

Jack Mustard

Clive Neal

Scott Neish

Benjamin J. Neumann

Mike O’Brien

Sean O’Keefe

John Olson

Scott Pace

Anatoly Perminov

Pepper Phillips

Carle Pieters

Charles Precourt

Gary P. Pulliam 

David Radzanowski

John Rather

Diane Rausch

Keith Reiley

Marcia Rieke

Joe Roche

Harrison “Jack” Schmitt

John Schumacher

John Shannon

Brewster Shaw

Milt Silvera

S. Fred Singer

George Sowers

Jim Spann

Paul Spudis

Steve Squyres

Thomas Stafford

Szymon Suckewer

Mike Suffredini

Phil Sumrall

Jeffrey P. Sutton

Mark Sykes

Keiji Tachikawa

Harley Thronson

Pat Troutman

Mark Uhran

Julie Van Kleeck

Zack Warfield

Johann-Dietrich Woerner

Tom Young

Robert Zubrin

Briefers and

Committee Contacts

Appendix F

The following is a list of individuals who briefed the Committee or responded to its

requests for information:
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Representative Robert Aderholt

Representative John Culberson

Representative Davis

Representative Bart Gordon

Representative Parker Griffith

Representative Ralph Hall

Representative Suzanne Kosmas

Representative Dennis Kucinich

Representative Kendrick Meek

Representative Alan Mollohan

Representative Pete Olson

Representative Bill Posey

Senator John Cornyn

Senator Orrin Hatch

Senator Kay Hutchison

Senator Mel Martinez

Senator Barbara Mikulski

Senator Bill Nelson

Senator Jeff Sessions

Senator Richard Shelby

Senator David Vitter

Members of the Public 

During the course of the Committee’s inquiry and deliberations, more than 1,000 members of the public submitted comments, 

suggestions and questions, as well as documents for the Committee’s consideration. 

The Committee wishes to thank all who provided this valuable input.

Members of Congress
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The Committee undertook its task with a strong emphasis on 

receiving input from, and communicating openly with, the 

American public, the media, and a broad range of stakeholders in the spaceflight community. The Committee employed 

both traditional outreach activities as well an extensive array 

of Web-based and social media technologies in its efforts to 

facilitate maximum public engagement.

The Committee Chairman held seven press conferences at 

various locations throughout the United States. Two of these 

were teleconferences, enabling members of the media to dial 

in and participate from anywhere in the world. Transcripts 

and/or video of these press conferences were posted on the 

Committee’s website.

Prior to beginning work, the Chairman also met individually 

with seven members of Congress—both Senators and Representatives, Republicans and Democrats, authorizers and 

appropriators. Members of the Committee participated in 

two hearings, one in the Senate and one in the House. In addition, many Members of Congress submitted written, oral, 

and videotaped statements to the Committee, which were 

subsequently posted on its website.

The Committee held seven public meetings: three in Washington, D.C.; one in Houston, TX; one in Huntsville, AL; 

one in Cocoa Beach, FL; and one via teleconference. Attendance ranged from 100-300 people at these events. At all 

but the August 12 public meeting and the October 8 public 

teleconference, the Committee reserved time for members 

of the public to make comments and ask questions. All 

public meetings were videotaped and aired live on NASA 

TV, and the Committee subsequently posted the videos to 

its website. All public meetings were also transcribed, with 

the transcripts also subsequently posted to the website. In 

addition to the public meetings, the committee held a series 

of closed preparatory meetings, fact-finding meetings, and 

site visits. 

The Chairman and the Executive Director/Designated Federal Official from NASA provided periodic progress reports 

to senior officials from NASA, the Office of Science and 

Technology Policy (OSTP), and the Office of Management 

and Budget (OMB). Weekly teleconferences were also held 

with staff members from NASA, OSTP and OMB to provide 

status reports.

The Committee’s primary communications tool was its website: http://hsf.nasa.gov. The website enabled anyone with 

Internet access to interact with the Committee in a variety of 

ways. The site provided ready access to information about 

the Committee and its activities, including: meeting presentations; videos and transcripts of public meetings; and background and related documents. These documents included 

Communications and

Public Engagement

Appendix G

Figure G-1. The homepage of http://hsf.nasa.gov included several tools to 

enable public engagement with the Committee. Source: Review of U.S. 

Human Spaceflight Plans Committee
142 Review of U.S. Human Spaceflight Plans Committee

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the Committee Charter; Statement of Task; the Federal 

Register notices; press releases; meeting agendas; Congressional statements; and documents and comments submitted 

by the public.

The home page of the website also prominently featured a 

number of tools that enabled members of the public to contact and/or interact with the committee (see Figure G-1):

The homepage of http://hsf.nasa.gov included several tools 

to enable public engagement with the Committee.

• “Provide a Comment or Suggestion” – This enabled members of the public to submit a 500-character comment or 

suggestion to the committee. Committee staff received 

more than 1,500 comments and/or suggestions during its 

activities.

• “Provide a Question and Get an Answer” – This provided a 

means for members of the public to submit questions to the 

Committee. The Committee screened questions for general 

appropriateness and then posted them to the website. Members of the public could then vote on questions that were 

posed. The Committee received over 250 questions, for 

which it developed answers that it then posted to the website. 

The Committee added a search capability to this feature to 

enable users to search for their questions and answers.

• “Follow the Committee’s Recent Updates (Twitter)” – The 

Twitter “micro-blog” website provided a means for the 

Committee staff to send short, informal messages to members of the public who signed up to receive updates from 

the Committee. The Committee had over 2,000 “followers” through Twitter who elected to receive updates from 

the Committee. All public meetings were “live-tweeted,” 

meaning that the Committee posted real-time public updates during presentations.

• “View our Photo Gallery (Flickr)” – The Committee shared 

pictures and images related to its work through Flickr, a 

photo-sharing website. The public could make comments 

on the photos and share images of the Committee’s activities on their own Flickr accounts. Pictures of previous human spaceflight endeavors were also posted. The public 

viewed an average of about 500 pictures per day on the 

Committee’s Flickr account. (See Figure G-2.)

• “Share Your Opinion on Topics” – The Committee posed 

three topics to stimulate public comment:

– What do you find most compelling about NASA’s 

human spaceflight activities and why? (147 comments received) 

– What role should international partners play in 

future U.S. spaceflight plans, and why? (98 comments received)

– To what extent should NASA rely on the private 

sector for human spaceflight-related products and 

services? (147 comments received) 

• “Subscribe to the Committee’s Updates via RSS” – Like 

many online publications, the Committee used Real Simple Syndication (RSS) feeds as another means of keeping 

the public informed about the Committee’s activities and 

progress. The Committee staff posted RSS updates, each 

of which were approximately three to five sentences in 

length.

• “Join Us on Facebook” – The Committee staff developed 

a Facebook Fan page, which it filled with Committee information, pictures, and resources similar to the overall 

Committee website, as well as a Facebook Fan page public comment area, or “wall.” The “wall” was used to disseminate daily information and answer general questions 

regarding the events, documents, and videos posted to the 

Committee website. The Committee had approximately 

2,100 Facebook “Fans.”

• “E-mail a Document” – Members of the public could email files to the Committee, a public engagement feature 

that had never previously been used on a NASA website. 

The Committee received over 200 files through this channel. When the sender indicated that a particular file could 

be shared with the public, the Committee posted it to its 

website.

• The individual “Meetings” pages allowed the public to 

view and share the videos of all the public meetings. Internet users could also “favorite” and comment on the 

videos as well.

The Committee’s goal in employing this broad spectrum of 

communication avenues was to set a new standard for openness and public interaction for endeavors of the type it was 

undertaking. 
Review of U.S. Human Spaceflight Plans Committee 143

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Figure G-2. The Committee’s Flickr account enabled it to share photos of its activities with the public. Source: Review of U.S. Human 

Spaceflight Plans Committee
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Aderholt, Robert, Representative, video statement to the 

Committee, United States House of Representatives, 

29 July 2009

Advisory Committee on the Future of the U.S. Space 

Program [Augustine Committee], “Report of the 

Advisory Committee on the Future of the U.S. Space 

Program Executive Summary”, December 1990

Aerospace Safety Advisory Panel, “Annual Report for 

2008”, 2008

Altair Project Office, “Altair Project Status”, NASA 

Johnson Space Center, 24 June 2009

Altair Project Office, “Appendix A—Altair LDAC-3 

Spacecraft Configuration”, NASA Johnson Space 

Center, 6 July 2009

Altair Project Office, “Appendix B—Altair Configuration 

and Design Development”, NASA Johnson Space 

Center, 6 July 2009

Altair Project Office, Appendix C—Altair Operations 

Concept and Design Reference Missions, 

Requirements Analysis Cycle 1 Baseline, NASA 

Johnson Space Center, 31 March 2009; International 

Traffic in Arms Regulations (ITAR) controlled

Altair Project Office, “Appendix D—Altair Operations 

Timeline Document”, NASA Johnson Space Center, 6 

July 2009

Altair Project Office, Ares V Mission Planner’s Guide 

(Draft), NASA Marshall Space Flight Center, November 

2008

Ares I Crew Launch Vehicle System Description 

Preliminary Design Review (PDR) Submittal, NASA, 

Sensitive But Unclassified

Bibliography

Appendix H

Ares I Integrated Vehicle Design Definition Document 

CxP 72070 Rev B, 2 March 2009, Sensitive But 

Unclassified and International Traffic in Arms 

Regulations (ITAR) controlled

Ares V Integrated Vehicle Design Definition Document, 

Phase A, Cycle 1 Configuration, CxP 72359, NASA, 

27 April 2009; Sensitive But Unclassified

Ares V Operational Concepts Document Draft, CxP 72336 

and Errata Sheet, NASA Marshall Space Flight Center, 

27 April 2009

Ares V Phase A Cycle 1 System Description Document 

(SDD), Baseline Draft, NASA, 27 April 2009; 

Sensitive But Unclassified and International Traffic in 

Arms Regulations (ITAR) controlled

Astronaut Office, “Radiation and Astronaut Health Risk”, 

NASA Johnson Space Center

“ATK Presentation to the Review of U.S. Human Space 

Flight Plans Committee”, ATK Space Systems, 21 July 

2009

Baccus, Ronald, NASA Johnson Space Center, Corliss, 

Jim, NASA Langley Research Center, Hixson, Robert, 

Lockheed Martin, “Landing Assessments, Establishing 

the DAC-3 Landing Architecture” 

Bearden, David and Hart, Matthew, NASA Advanced 

Programs Directorate, Skratt, John, Space Launch 

Projects, Human Rated Delta IV Heavy Study 

Constellation Architecture Impacts, NASA and The 

Aerospace Corporation, 1 June 2009

Cabana, Robert, NASA Kennedy Space Center Director, 

“Human Spaceflight Review Kennedy Space Center”, 

NASA, 30 July 2009
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Cantwell, Elizabeth, Deputy Associate Laboratory Director, 

National Security, “Life and Physical Sciences in 

Microgravity and Partial Gravity”, Oak Ridge National 

Laboratory, 5 August 2009

Chilton, Jim, Vice President and Program Manger, 

Exploration Launch Systems, “Boeing Human 

Spaceflight Capability Overview”, Boeing, 24 June 

2009

Cline, Lynn, Deputy Associate Administrator of Space 

Operations Mission Directorate, “NASA Expendable 

Launch Services Current Use of EELV“, NASA 

Headquarters, 17 June 2009

Cline, Lynn, “Space Operations Mission Directorate 

Program Review”, NASA Headquarters, 20 May 2009

Coats, Mike, NASA Johnson Space Center Director, 

“Johnson Space Center Perspectives for Augustine 

Review Panel” [White Paper], NASA Johnson Space 

Center, July 2009 

Coats, Mike, “Johnson Space Center Perspectives, 

Augustine Review Panel”, NASA Johnson Space 

Center, 28 July 2009

Collection of 10 papers on Constellation Program Near 

Earth Object (NEO) Mission Study Collection of 33 

papers on in-space propellant transfer

Collection of 64 published papers on Other Microgravity 

Research Facilities 

Collection of 72 International Space Station published 

papers

Columbia Accident Investigation Board (CAIB), CAIB 

Report Volume 1, August 2003

Commercial Spaceflight Federation, Commercial 

Spaceflight in Low Earth Orbit is the Key to 

Affordable and Sustainable Exploration Beyond . . ., 

29 June 2009 

Committee on the Evaluation of Radiation Shielding 

for Space Exploration, National Research Council, 

Managing Space Radiation Risk in the New Era of 

Space Exploration, The National Academies, 2008

Committee on the Rationale and Goals of the U.S. Civil 

Space Program, National Research Council, America’s 

Future in Space: Aligning the Civil Space Program 

with National Needs, The National Academies, 2009

Committee to Review NASA’s Exploration Technology 

Development Program, Aeronautics and Space 

Engineering Board, National Research Council, 

A Constrained Space Exploration Technology 

Program: A Review of NASA’s Exploration 

Technology Development Program, The National 

Academies, 2008

Committee on the Scientific Context for Exploration of the 

Moon, National Research Council, Scientific Context 

for the Exploration of the Moon Final Report, The 

National Academies, 2007

Congressional Budget Office, “The Budgetary Implications 

of NASA’s Current Plan for Space Exploration”, April 

2009

Conley, Cassie, Planetary Protection Officer, “Planetary 

Protection and Human Exploration”, NASA, 9 July 

2009

“Constellation Alternate Scenario Early Ares V Dual 

Launch Options”, NASA, 28 July 2009 

“Constellation Launch Vehicles Overview Part 1”, NASA, 

29 July 2009

Constellation Program System Requirements for the Orion 

System, CxP 72000, Rev D, Errata Revision and 

History Page, NASA, 17 June 2009

Constellation Program System Requirements for the Orion 

System, CxP 72000, Rev D—Pre DQA, NASA, 17 

June 2009

Cooke, Doug, Associate Administrator of Exploration 

Systems Mission Directorate, “Commercial Crew and 

Cargo Program Overview”, NASA, 17 June 2009

Cooke, Doug, “Exploration Systems Mission Directorate: 

FY 2010 Budget Request to Congress”, NASA 

Headquarters, 14 May 2009

Cooke, Doug, “Global Exploration Strategy (GES): 

Highlights on Progress and Future Opportunities”, 

NASA, 16 June 2009

Cooke, Doug and Hanley, Jeff, “Review of Human 

Spaceflight Plans Architectural Drivers”, NASA, 16 

June 2009

Cooke, Doug and Hanley, Jeff, “Review of Human 

Spaceflight Plans Constellation Overview”, NASA, 17 

June 2009

Cooke, Doug and Hanley, Jeff, “Review of Human 

Spaceflight Plans Implementation”, NASA, 17 June 

2009

Coonce, Tom and Gunderson, Johanna, Office of Program 

Analysis and Evaluation, “Cost and Schedule Growth 

and Containment at NASA”, NASA Headquarters, June 

2009

Cornyn, John, Senator, video statement to the Committee, 

United States Senate, 28 July 2009
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Covey, Dick, President and CEO, United Space Alliance, 

“United Space Alliance (USA), Response to the 

Review of the U.S. Human Space Flight Plans 

Committee”, USA, 21 July 2009

Craig, Douglas, “ESR&T Support of the Assessment of 

Alternatives (AOA) - Development of a Modular 

Reusable Advanced Technology Architecture”, NASA, 

March 2005; For NASA Internal Use Only—PreDecisional 

Crew Exploration Vehicle Project Flight Dynamics Team, 

Trajectory Design and Performance Requirements for 

Human Lunar Missions Using the Mission Assessment 

Post-Processor (MAPP) Final Report, NASA Johnson 

Space Center, February 2009; Export controlled 

information

Cross, Robert and Turner, John, “Constellation Program 

LOC/LOM [Loss of Crew/Loss of Mission] Process 

and Status”, NASA, 6 April 2009 

Cucinotta, Francis, “Radiation Protection Assessment for 

One-Year ISS Missions”, NASA

Cucinotta, Francis, Clowdsley, Martha, Kim, Myunghee, Qualls, Garry, Simonsen, Lisa, Sulzman, 

Frank, Zapp, Neal, “Phase III Constellation 

Architecture Trade Study Space Radiation Analyses 

for Lunar Outpost Variations in Risk Postures to 

Enable Exploration Final Data Package”, NASA, 

12-14 January 2008

Cucinotta, Francis, Kim, Myung-Hee, Willingham, 

Veronica, George, Kerry Physical and Biological 

Organ Dosimetry Analysis for International Space 

Station Astronauts, Radiation Research Society, 

2008

Culberson, John, video statement to the Committee, United 

States House of Representatives, 28 July 2009

Culbertson, Frank “Oribtal’s ISS Commercial Resupply 

Service”, Orbital, 17 June 2009

Defense Contract Management Agency Industrial Analysis 

Center, Liquid Rocket Engines Industrial Capability 

Assessment, Department of Defense, 25 September 

2006, Business Sensitive, Government Proprietary—

For Official Use Only

“Depot Architecture for Lunar Exploration and Beyond”, 

NASA, 9 July 2009

Dordain, Jean-Jacques to the Augustine Committee, 

“Statement by Jean-Jacques Dordain, Director General 

of the European Space Agency”, ESA, 17 June 2009

Drake, Bret, Mars Design Reference Architecture 5.0 Study 

Executive Summary, NASA, 4 December 2008

Dyer, Joseph, NASA Aerospace Safety Advisory Panel 

(ASAP) Chair, “ASAP Puts and Takes”, NASA, 14 

July 2009

Ess, Bob, “Ares I-X Status”, NASA, 30 July 2009

Evans, Cynthia and Robinson, Julie, Office of the 

International Space Station Program Scientist, NASA 

Johnson Space Center; Tate-Brown, Judy, Thuman, 

Tracy and Crespo-Richey, Jessica, Engineering and 

Science Contract Group; Bauman, David and Rhatigan, 

Jennifer, NASA Johnson Space Center, International 

Space Station Science Research Accomplishments 

During the Assembly Years: An Analysis of Results 

from 2000-2008 Executive Summary, Houston, Texas, 

December 2008

Eveker, Kevin, “The Budgetary Implications of NASA’s 

Current Plans for Space Exploration”, Congressional 

Budget Office, 16 June 2009

Exploration Systems Architecture Study (ESAS) Team, 

“ESAS Executive Summary”, NASA, November 2005

Exploration Systems Mission Directorate, Lunar 

Architecture Focused Trade Study Final Report, Rev 

A, ESMD-RQ-0005, NASA Headquarters, 4 February 

2005

Exploration Systems Mission Directorate, Lunar 

Architecture Broad Trade Study Final Report, Rev A, 

ESMD-RQ-0006, NASA Headquarters, 4 February 

2005

Exploration Systems Mission Directorate, “Lunar Vehicle/

Lunar Architecture Analysis of Alternatives (AoA)”, 

NASA, 8 February 2005, Pre-Decisional, NASA 

Internal Use Only

Exploration Transportation System Strategic Roadmap 

Committee, Final Report, NASA, May 2005

Fragola, Joseph, “The Path to a Safer Crew Launch 

Vehicle, The Ares I Story”, Valador, 29 July 2009

Fragola, Joseph, “White Paper: Ares I, the Crew Launcher 

with Crew Safety Designed In”, Valador, Inc., June 2009

Friedman, Louis, Roadmap Team, “Beyond the Moon, A 

New Roadmap for Human Space Exploration in the 

21st Century”, The Planetary Society, November 2008

Gass, Michael, President and CEO of United Launch 

Alliance (ULA), “Briefing to the Review of U.S. 

Human Space Flight Plans Committee”, ULA, 16 June 

2009, ULA Proprietary Information

Gass, Michael, President and CEO of United Launch 

Alliance (ULA), “Briefing to the Review of U.S. 

Human Space Flight Plans Committee”, ULA, 17 June 

2009
148 Review of U.S. Human Spaceflight Plans Committee

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Gerstenmaier, Bill, Associate Administrator for Space 

Operations Mission Directorate, “International Space 

Station Extension and Utilization Planning”, NASA 

Headquarters, 9 June 2009

Geyer, Mark, Orion Project Office Manger, “Review of 

Human Spaceflight Plans Orion Crew Exploration 

Vehicle”, NASA, 28 July 2009

“Global Exploration Strategy (GES) Framework: 

Executive Summary”, NASA and Other Space 

Agencies, May 2007

Gordon, Bart, Representative, letter to Mr. Norm 

Augustine, United States House of Representatives, 17 

June 2009

Griffith, Parker, Representative, video statement to the 

Committee, United States House of Representatives, 29 

July 2009

Griffin, Michael, NASA Administrator, and Sega, Ronald, 

Department of Defense Executive Agent for Space, to 

John Marburger III, Director, Office of Science and 

Technology Policy, Washington, DC, 5 August 2005

Hall, Ralph, Representative, “Statement of the Honorable 

Ralph Hall (R-TX), Ranking Member, U.S. House 

Committee on Science and Technology”, United States 

House of Representatives, 17 June 2009

Hanley, Jeff, Constellation Program Manger, “NASA 

Constellation Projects Closing Comments”, NASA, 30 

July 2009

Hanley, Jeff, “NASA Constellation Projects Introduction”, 

NASA, 28 July 2009

Hawes, W. Michael, “Summary Description of Previous 

Studies”, NASA, 17 June 2009

“Human Exploration of Mars, Design Reference 

Architecture 5.0”, NASA, 29 July 2009

“Human Research Program Utilization Plan for the 

International Space Station”, NASA

“Human Space Flight Capabilities, pursuant to Section 

611(a) of the NASA Authorization Act of 2008 (P.L. 

110-422)”, NASA, April 2009 

Hutchison, Kay Bailey, Senator, “Statement by Senator 

Kay Bailey Hutchison for Submission to Augustine 

Review Panel”, United States Senate, 17 June 2009

Hutchison, Kay Bailey, Senator, “Statement by Senator 

Kay Bailey Hutchison for Submission to Augustine 

Review Panel Tuesday, July 28, 2009”, United States 

Senate, 28 July 2009

Impacts of Shuttle Extension, pursuant to Section 611(e) of 

the NASA Authorization Act of 2008 (P.L. 110-422), 

NASA, April 2009 

Innovative Partnerships Program, Spinoff: 50 Years of 

NASA-Derived Technologies (1958-2008), NASA, 

2008

“International Space Station, Research Facilities on ISS, 

International Partner Plans for Research”, NASA, June 

2009 

 Janetos, Anthony, “Earth Science and Applications from 

Space, National Imperatives for the Next Decade”, 5 

August 2009

Jones, Tom, “The Asteroid Opportunity: Human 

Exploration of Near Earth Objects”, Association of 

Space Explorers and NASA Advisory Council, 9 July 

2009

Joosten, Kent, “Constellation Lunar Architecture 

Overview”, NASA, 9 July 2009

Kinnersley, Mark, Director of Business Development, 

Orbital System and Exploration Division, “EADS 

Astrium Statement to the Review of U.S. Human 

Spaceflight Plans Committee”, EADS Astrium, 5 

August 2009

Kinnersley, Mark, “Statement by EADS Astrium”, EADS 

Astrium, 5 August 2009

Kosmas, Suzanne, Representative, “Statement of 

Congresswoman Suzanne Kosmas (FL-24), 

The Review of U.S. Human Space Flight Plans 

Committee”, United States House of Representatives, 

30 July 2009 

Kottkamp, Jeff, Lieutenant Governor of Florida, statement 

in person to the Committee, 30 July 2009

Kucinich, Dennis, Representative, letter to Mr. Norm 

Augustine, United States House of Representatives, 4 

August 2009

Le Gall, Jean-Yves, Chairman and CEO of Arianespace, 

“Presentation to the United States Human Space Flight 

Plans Review Committee”, Arianespace, 5 August 

2009

Leonard, Matt, Lunar Surface Systems, Deputy Project 

Manager, “Lunar Surface Systems (LSS) Briefing to 

Augustine Committee”, 9 July 2009

Lester, Dan, “Future of Human Space Flight and 

Astronomy”, the University of Texas, 9 July 2009

Lightfoot, Robert, NASA Marshall Space Flight Center 

(MSFC) Acting Center Director, “Marshall Space 

Flight Center Launching the Future of Exploration and 

Science”, NASA MSFC, 29 July 2009
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Lindsey, Steve, Chief of the Astronaut Office, “Human 

Spaceflight Review Astronaut Office Perspective”, 

NASA Johnson Space Center, 28 July 2009

MacLean, Steve, President, Canadian Space Agency 

(CSA), “CSA-NASA Human Space Flight 

Cooperation”, CSA, 16 June 2009

Manella, Rick “Shuttle Derived Heavy Lift Launch 

Vehicle”, NASA, 25 June 2009

Maguire, Joanne, Executive Vice President, “Review 

of the U.S. Human Space Flight Plans Committee, 

Committee Discussion”, Lockheed Martin Space 

Systems Company, 22 July 2009

Mango, Ed, “Constellation Space Transportation Planning 

Office”, NASA, 30 July 2009

Marburger, John, former Science Advisor to President 

George W. Bush and Director, Office of Science and 

Technology Policy (2001-2009), “Review of U.S. 

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NASA Space Shuttle Workforce Transition Strategy 

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2009
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CAIB: 

Columbia Accident Investigation Board

COTS: 

Commercial Orbital Transportation Services

CSA: 

Canadian Space Agency

DDT&E: 

Design, Development, Test, & Evaluation

DOD (or DoD): 

Department of Defense

EDL:

Entry, Descent and Landing

EDS:

Earth Departure Stage

EELV: 

Evolved Expendable Launch Vehicle

ESA: 

European Space Agency

ESAS:

Exploration Systems Architecture Study

ESMD:

Exploration Systems Mission Directorate

EVA:

extra-vehicular activity (spacewalk)

FAA:

Federal Aviation Administration

FY:

Fiscal Year

GDP:

Gross Domestic Product

GES:

Global Exploration Strategy

INKSNA:

Iran, North Korea, and Syria Nonproliferation Act

ISS:

International Space Station

ISRO:

Indian Space Research Organisation

ITAR:

International Traffic in Arms Regulations

JAXA:

Japan Aerospace Exploration Agency

KSC:

Kennedy Space Center

KM:

Kilometers

LEO:

low-Earth orbit

LH2:

liquid hydrogen

LOX:

liquid oxygen

Acronyms and

Abbreviations

GLOSSARY
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mt:

metric ton

NASA:

National Aeronautics and Space Administration

NEO:

near-Earth object

NSS:

national security space

NTR:

nuclear thermal rocket

OMB:

Office of Management and Budget

OSTP:

Office of Science & Technology Policy

PDR:

Preliminary Design Review

PRA:

probabilistic risk assessment

PRC:

People’s Republic of China

SDR:

System Design Review

SEI:

Space Exploration Initiative

SRB:

Solid Rocket Booster

SRM:

Solid Rocket Motor

SSME:

Space Shuttle Main Engine

STEM:

Science, Technology, Engineering and Mathematics

STS:

Space Transportation System (Shuttle)

TLI:

Trans Lunar Injection

TPS:

Thermal Protection System

TRL:

Technology Readiness Level

ULA:

United Launch Alliance

VSE:

Vision for Space Exploration
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