|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 33
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
OCR for page 34
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
OCR for page 35
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
OCR for page 36
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,
OCR for page 37
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.
OCR for page 38
Representative terms from entire chapter:
nasa report
