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VI Summary Responses to Questions Posed by the Vice President In his charge to the committee, the Vice President posed a series of specific questions. The committee's responses, taken from the body of the report, follow: SCOPE OF THE REPORT OF THE NASA 90-DAY STUDY 1. Does the report address the widest possible range of technically cred- ible approaches to meeting the President's exploration goals? If not, what additional areas warrant exploration? The NASA report addresses a reasonable set of technological and strategic approaches, but not all of the technically credible approaches have been analyzed. Other approaches have been discussed in the past, and many of those have been examined by NASH The National Commission on Space, for example, included in its recommendations cycling spaceships between Mars and Earth orbits using electric propulsion. Regarding additional areas that warrant consideration, the committee believes it prudent to await better understanding of significant life sciences issues before deciding the detailed architecture for sending humans to Mars. The committee further believes that precursor missions, such as the Mars ObseIver, are essential to understanding the Martian environment and to determining appropriate landing sites, for example for exploratory landers that might be sent from a Mars orbiter. 33

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34 HUMAN EXPLORATION OF SPACE 2. [Over the next 30 years] what are the likely areas for technical break- throughs relevant to space exploration? Has the report fully taken these into account? Likely areas for technical advances include nuclear power, propulsion, and conversion technologies for space applications; controlled environmen- tal life support systems; sophisticated human/machine systems; physiologi- cal and psychological countermeasures to the space environment; effective artificial gravity; and the intertwined technologies In computer science and artificial intelligence that provide for better information management. Technologies to lower the cost of access to space probably will become available, including advanced materials and a new generation of cryogenic engines. Some of the breakthroughs and evolutionary development will come principally from human exploration research and development; oth- ers will evolve whether or not humans explore space, but can benefit from the exploration initiative. The NASA report is prudently based largely on incremental advances in technology and does not depend on breakthroughs. Aerobraking tech- nology is scheduled for demonstration in the near future. Nuclear propul- sion, although not critical to the reference approaches, would represent a breakthrough and will require demonstration prior to commitment to its use. 3. Is the range of science goals and objectives commensurate with the proposed technical capability? Does the report distinguish between critical or enabling science and complementary science? Clearly, technical capabilities are of paramount importance to the HEI. Nevertheless, worthwhile research can be done in conjunction with the HEI if research strategies are developed by weighing (1) the scientific priority of a given research activity, and (2) whether that research might best be accomplished by another means. Although not well distinguished from complementary science in the NASA report, the enabling research in life sciences is crucial to productive and safe human occupancy of space. Other areas of enabling science include research on the nature of the Martian atmosphere and research and technology development for the use of in-situ resources. 4. Are there implications (infrastructure-institutional/other national in- terest) that have not been considered? The NASA study recognizes the need for personnel, facilities, and equipment to fulfill the HEI. As noted in the report, NASA's current facilities and civil service personnel complement may need augmentation

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SUMAL4RY RESPONSES 35 to address the HEI. The program, led by NASA, should be designed to draw on the resources of other federal agencies. The HEI needs to be conducted with greater efficiency than are most federal programs. As the NASA report notes, the HEI ". . . presents a unique opportunity to demonstrate the viability of streamlined administrative and management processes." Procurement and budgeting obstacles are also recognized in the report. NASA believes that international partners should be included in the early definition of HEI. While it is important to work together with other nations, the committee believes it is necessary to understand the HEI mis- sion designs and architectures before making commitments. The report de- fines varying approaches to international cooperation, including "separate, but coordinated," "augmentation through cooperation," "interdependence with clear interfaces," and "joint development and operation," but NASA will need policy guidance about the right approach to employ as the HEI progresses. CONTENT OF THE REPORT OF THE 90-DAY STUDY 1. What are the report's technical assumptions? Are they reasonable? The report assumes continuing dependence upon the space shuttle and shuttle-derived vehicles. Some of the reference approaches assume accel- eration of the availability of Space Station Freedom (SSF) and all assume that the station will become operational by the late 1990s. Operation of the station by the late 1990s appears to be a reasonable assumption. Present plans for the station, however, are not adequate to satisfy HEI life sciences needs. At this time, it is also uncertain whether the station will be the most appropriate staging base for the Moon and Mars. The report does not assume that the Advanced Launch System will materialize, but observes that such vehicles could be used to great advantage were they available. It does not assume nuclear rockets or power, but indicates that they could be useful were they available. 2. Are there innovative uses of existing technology that the report has overlooked? There undoubtedly will always be new ways to do things based on existing technology. That said, however, none were obvious in reviewing the NASA report and alternative scenarios. In considering this question, the committee did not regard paper studies to be existing technology, due to the uncertainties involved in experimentally proving the concepts. Inflatable space modules, on the other hand, have had several NASA prototypes; but the applications for which they can be used are uncertain. SSF modules

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36 HUAL4N EXPLORATION OF SPACE do not yet exist, but the nation has built a space station before and knows a lot about how to do it. Use of SSF modules for bases and orbiters is a concept based on use of existing technology. 3. Are the cost estimates and schedules reasonable? NASA has conducted exercises to estimate the order of magnitude of costs of the HEI using several cost models derived from experiences with past space systems. Accurate cost estimates, however, are only possible in circumstances where experience with the technologies exists and where objectives are clear. As a general rule, the greater the technical risk inherent in a mission approach, the larger the uncertainty. The HEI schedule will take into consideration other national resource commitments' which should be set by the social and political process, with scientific and technical input. The schedules presented in the NASA document are therefore not highly relevant, but do serve as a backdrop against which to assess various cost scenarios and mission options. It will not be possible to meet cost or schedule estimates without a clear, long-term commitment from the executive and legislative branches of government. In addition, a program subjected to repeated phasing and rephasing cannot meet schedule and cost targets. Are there alternative ways the schedule might be moved forward to provide visible, near-term accomplishments? NASA's Reference Approach B represents one option that advances Mars exploration from 2018 to 2011, but it depends upon accelerating completion of Space Station Freedom. For technical and cost reasons, such acceleration seems unlikely. Concepts such as the Great Exploration, using as yet unproven in- flatable technologies and expedited procurement procedures, and concepts based on using space station modules for orbiters and bases could poten- tially enable a return to the Moon and human exploration of Mars earlier than the NASA reference missions. However, an adequate infrastructure for potential future needs would need to be built separately. Another alternative is a scenario where initial missions to Mars would have limited capabilities. Beyond questions of technical feasibility, the question of how elaborate the initial human missions need to be should be examined. This could involve trade-offs between up-front investments for technology development (which can reduce long-term operating costs for many future missions) and low up-front investment focused on near-term objectives, an approach that will save money in the present but that may eventually lead to more expensive operating costs. The committee believes that almost any approach to HEI can have visible, near-term milestones. Humans living and working on the Moon,

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SUMALARY RESPONSES 37 construction of habitats, and scientific and mining facilities can all provide evidence of accomplishments in space. Similarly, are there alternate routes which could dramatically in- crease performance, lower costs, move the schedule forward, or reduce risks? If so, what levels of programmatic and technical risk do they have? The alternatives that the committee examined to move forward the schedule for lunar and Mars bases entailed higher levels of programmatic, technical, and human risk than the NASA reference approaches, as well as lesser capabilities. The levels of uncertainty in estimating costs for these alternatives are so high that it is not possible to determine which among the approaches reviewed offers the potential for lower costs. Once again, the most dramatic alternate route to increase performance would be the development of safe nuclear propulsion for interplanetary travel. 4. Are the overall approaches/architectures described in the report rea- sonable? For example, are the key elements of NASA's plan consistent, i.e., availability of the space station, heavy lift vehicles, etc.? Yes, the committee believes the overall approaches described in the report are reasonable. The treatment of nuclear power and propulsion, however, appears to be somewhat ambiguous. Nuclear power on the Moon is seen as essential in the 90-Day Study, but scenarios are also provided that rely on solar dynamic power. Nuclear propulsion is listed as a critical technology for development, yet none of the reference approaches call for it. Given the developmental and societal uncertainties concerning nuclear power, however, the treatment of this matter is not unreasonable. In general, the key elements of the NASA document are consistent. For example, a given scenario does not rely on the station or technology development without considering the time needed for it to be established or developed. A space station in LEO is considered essential for all of the scenarios; however, the requirements of the HEI may not be fully met by Space Station Freedom. Last, the committee believes that, whatever the selected architecture for HEI, there is a need for a new emphasis on advanced technology development and that it is highly desirable to continue to cast a wide net for innovative concepts.

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