Issues for Further Study

Hubert Davis


The mind-expanding nature of our future activities beyond Earth leads to a plentiful flow of new ideas and major improvements on earlier concepts. The recent discovery of numerous Earth-crossing asteroids, for example, adds greatly to the magnitude and diversity of the material resources in space of which we are aware. However, a serious question arises. Does there exist any orderly process for gaining general awareness of these new ideas or for evaluating their importance to society? Membership in a specific academic, government, or industrial group, coupled with persistence and eloquence, are today's means of hearing and being heard. These mechanisms may not, however, be the optimal means for flushing out and eventually implementing the best new ideas.

One small step toward achieving the goal of preserving for use the best of the suggested new concepts is the "systems study" approach. In this approach, a set of future needs and a straightforward means of satisfying these needs are described in quantitative terms as a "scenario." This scenario is then set forth as a benchmark case for testing the relative merit of new, alternative means of meeting one or more of these needs. This systems approach should be used to assess the merits of new concepts and to identify the most important advancements in technology needed to establish or enhance the merit of the concept. (The map of a lunar outpost illustrates the application of another kind of systematic study, known as ..general living systems" theory and analysis.)

Ideally, as needs change and new concepts and data become available, the "baseline" scenario should be revised to incorporate some of the new ideas. When that occurs, the technology development of the newly incorporated approaches should actively begin to remove residual uncertainties. But the effort should, in most cases, stop short of "prototyping."

It is very important to remain as generic or flexible as practical in order to be ready to adapt the scenarios and associated technologies to changes in the social norms, political climate, and economic health of the nation.

To further complicate matters, once a new "baseline" scenario is accepted for testing of new concepts, earlier conclusions must also be reexamined since former 11 new" ideas that were earlier rejected may be found to be highly desirable given the new scenario.

Some formalized means should be found for establishing, testing and refining, utilizing and maintaining a baseline scenario of long-range space activities and of supporting, refereeing, and reviewing the application of this scenario in system studies of new concepts. This process was begun by NASA's Office of Aeronautics and Space Technology (OAST) in the mid1970s, but it was abandoned in the late 1970s because of budgetary constraints and the press of nearer term needs, as perceived by NASA management. Total cost to NASA of restoring and enhancing these efforts would be only 0.01-0.02 percent of NASA's yearly budget.*

*Since this report was drafted, significant long-term planning activities have been undertaken, initiated by the work of the National Commission on Space. The commission's report, Pioneering the Space Frontier, is available from Bantam Press.

Lunar Resource Utilization

Resource Prospecting

Early priority should be given to an automated lunar polar spacecraft to perform a global survey of the Moon with instruments appropriate to detect the presence, location, and concentration of useful materials. This mission may have to be repeated or extended to follow up on areas of particular scientific and economic interest.

Lunar Assay

Automated surface rovers, with the capabilities of coring, assaying materials, and possibly returning samples to Earth, should be sent out to gather data. This activity should be completed several years before final commitment is made to the location of the initial lunar base. (See figure 26.)

Lunar Mining

Mining the Moon will present new challenges. Surface mining will probably be the norm, although subsurface mining may be necessary in some cases. The movement of large amounts of material will degrade the scientific utility of the mining site, alter its appearance, and release gases into the tenuous lunar atmosphere. Thus, the effect of lunar mining on the environment will have to be carefully evaluated before mining begins.

Process Development

Ideas for getting Oxygen from lunar materials have been generated since the 1960s and '70s.*

*See, for example,
Rosenberg, S. D.; G. A. Guter; and F. E. Miller. 1964. The On-Site Manufacture of Propellant Oxygen Utilizing Lunar Resources. Chem. Eng. Prog. 62:228-234.
Rosenberg, S. D.; G. A. Guter; and F E. Miller. 1965. Manufacture of Oxygen from Lunar Materials. Ann. N.Y. Acad. Sci. 123:1106-1122.
McKay, David S., and Richard J. Williams. 1979. A Geologic Assessment of Potential Lunar Ores. In Space Resources and Space Settlements, NASA SP-428, pp. 243-255.
Rao, D. Bhogeswara; U. V. Choudary; T. E. Erstfeld; R. J. Williams; and Y. A. Chang. 1979. Extraction Processes for the Production of Aluminum, Titanium, Iron, Magnesium, and Oxygen from Nonterrestrial Sources. In Space Resources and Space Settlements, NASA SP-428, pp. 257-274 .

Now, preliminary design studies and process engineering should be performed to derive a comprehensive plan involving laboratory experimentation, bench testing, and pilot plant development for the purpose of testing, developing, and refining the beneficiation and feedstock conversion steps necessary to produce useful products from lunar regolith material. (See figure 27.). This plan should permit examination and quantification of the optimal conversion pressure, temperature, and concentration, conversion efficiency, energy requirements, heat rejection, catalysts, carrier fluid consumption, and the scale effects so as to allow confident design of an operational chemical plant.

Ancillary Equipment Development

Equipment for automated mobility; solid material conveyance; feedstock material insertion and extraction (into and from the converter); water vapor condensation; electrolysis; gaseous oxygen and hydrogen refinement, movement, and storage; oxygen liquefaction; liquid oxygen storage and transport; and other purposes must be conceptualized, designed, tested, and developed for the minimum of human intervention. (See figure 28.).

A virtue of these activities is that each of these elements is individually a rather straightforward application of advanced automatic or teleoperative technology. And with the appropriate mix of this technology and the human element, the optimal manufacturing capacity can be placed on the Moon.

Development of Space Transportation Equipment

Large, automated orbital transfer vehicles and lunar landing vehicles must be better defined before we can quantify performance, life, and cost factors. Numerous technology developments will be needed before we can confidently begin full-scale development. The key technologies of these vehicles appear to be the following.

High performance oxygen/hydrogen rocket engine: A newgeneration rocket engine will be needed early. It should generate higher specific impulse than current engines (480-490 sec, as compared to 446 sec for the RL-10), produce a thrust of approximately 7500 lbf, provide moderate throttling capability, and be designed for long life with maintenance in space.

Owing to these requirements, an advanced space engine will have to be designed for a very high chamber pressure (1500-2000 psia) and a high expansion ratio (2000:1). (See figure 29.)

Cryogenic propellant handling and preservation: The ability to store, transfer, measure, and condition cryogenic fluids (including liquid oxygen, hydrogen, and argon) with zero loss requires extensive development and testing. (See figure 30.)

Aerobraking technology: Although theoretically very attractive for returning payloads to LEO, many uncertainties, including aerobraking equipment mass, must be resolved before aerobraking is practiced. (See figure 31.). Advanced concepts in guidance, navigation, and control will need investigation, particularly for uses that involve higher velocity return to Earth orbit. Early Shuttle-launched test missions should be considered.

Advanced composite structures:
Overall spacecraft systems design using advanced composite structures requires data on micrometeoroid impact effects, cryogenic fluid compatibility, equipment attachment, inspection and repair, and other aspects.

Operations technology: The infant art and science of maintaining, servicing, storing, and checking out complex space vehicles (both manned and automated) whose entire service life is spent in the space environment requires nurturing. (See figure 32.). Many facets of this problem require both hardware and software development. A design goal of operations technology must be efficiency. Current operation procedures for the Space Shuttle are so costly that, if applied directly to reusable orbital transfer vehicles, they could invalidate the cost-savings potential of these vehicles over expendable vehicles.

Debris control, collection, and recycling: Our future operations in space must not litter. Active measures are needed to prevent littering. A plan of action is needed to remove discarded objects from valuable space "real estate." (See figure 33.). And the technology for recycling waste materials in space needs to be developed. The Shuttle external tank represents a resource in space which can be employed perhaps early in the space station program. Thirty tons of aluminum structure available at negligible cost in LEO is simply too valuable to be discarded.

Asteroid Resource Utilization

The first step in asteroid utilization is making an inventory. Advanced Earth-based observation techniques and equipment can be economically fielded to gain quantum improvements in our knowledge of the number, orbits, size, composition, and physical properties of the Earth-crossing asteroids (see table 9). A subset of those asteroids inventoried might be further examined by spaceborne instruments with capabilities similar to those of the proposed Mars geochemical mapper (See figure 34.). A smaller subset might be identified as candidates for surface exploration and pilot plant operation.

TABLE 9. Physical Parameters of 17 Near-Earth Asteroids*
NAMEDiameter, km Semimajor axis of its orbit,
astronomical units
Inclination of its orbit
degrees from the plane of hte ecliptic
433 Eros 39.3 x 16.1a 1.458 0.219 10.77
887 Alinda 3.6b 2.50 .55 9.19
1036 Ganymed - 2.66 .54 26.45
1566 Icarus 1.04d 1.08 .83 22.91
1580 Betulia 6.3f 2.19 .49 52.04
1620 Geographos 2.4g 1.24 .34 13.33
1627 Ivar 6.2h 1.86 .40 8.44
1685 Toro 5.6i 1.36 .44 9.37
1862 Apollo 1.2 ± 0.1j 1.47 .56 6.26
1865 Cerbus - 1.08 .47 16.09
1915 Quetzacoatl 0.14h 2.53 .58 20.5
1943 Anteros 2.0k 1.43 .26 8.7
2100 Ra Shalom >1.4l 0.83 .44 15.7
2201 Oljato - 2.18 .71 2.5
1979 VA - 2.5 .61 2.7
1980 AA - 1.86 .43 4.1
1981 QA - 2.35 .49 8.95

a Lebofsky and Rieke (1979). h G.J. Veeder (personal communication).
b Zellner and Gradie (1976). i Dunlap et al. (1973).
d Gehrels et al. (1970). j Lebofsky et al. (1981).
f Tedesco et al. (1978). k Revised from Veeder et al. (1981; personal communication).
g Dunlap (1974). l Lebosky (personal communication)

* After Lucy A. McFadden, Michael J. Gaffey, and Thomas B. McCord, 1984, Mineralogical-Petrological Characterization of Near-Earth Asteroids, Icarus 59:25-40.

In parallel, advanced space propulsion and mission design techniques should be applied to come to understand the logistics for exploiting this potential space resource.

Space Energy Utilization

The petroleum crisis of the 1970s was not an anomalous, singular event. Even in the face of very effective energy conservation and increased petroleum exploration, the problem will return in the near future. The nearly infinite furnace of the Sun must eventually be used to provide the dominant portion of human beings' energy needs. Space is the best place to harvest and convert sunlight into more concentrated, continuous, and useful forms. Studies on the solar power satellite, a network of solar reflectors, and other means of enhancing the utility of sunlight on Earth should continue. However, the studies should be expanded to include use of such systems to provide energy from space in space.

Space "Real Estate" Utilization

If material and energy resources were both abundant and accessible to people, numerous human endeavors exploiting the attributes of space (nearly perfect vacuum, microgravity, and vantage point) would begin and greatly expand.

The communication relay function from GEO is only the first of an infinite series of useful and economically valuable activities in space. The ability to observe activities on Earth and, if necessary, to intervene in events may prove to be the means by which nuclear technology is reconfigured to benefit humankind rather than to threaten our existence.

Space as a place to go to and later as a place to live and work in will become of increasing importance in the decades to come. It is not too early to consider growth from NASA's 8- to 12-person space station to communities 2 or 3 orders of magnitude larger (See figure 35.). Life support technology will need to progress from merely preserving respiratory functions with some small degree of mobility for a handful of exceptional, highly trained people to providing comfortable and even luxurious accommodations for ordinary human beings at work, at school, or at leisure. (See figure 36.).

The potential of personally working and residing in space is perhaps the strongest single motivation for young people to excel. And it is important to the development of productive future generations motivated and trained to prove totally incorrect the gloomy "fixed sum game" scenarios for humankind's future. Needed are effective and serious technical and sociological studies, artistic representation of space architectures at both small and large scale, and use of the media to portray people's future in space more realistically as productive and peaceful rather than universally warlike and destructive.

In viewing works like Star Trek and Star Wars, we must wonder what precursor society and organization built the wonderful artifacts so wantonly destroyed in an hour or two. Some of us would be much more interested in the character and adventures of the builders than we are in those of the desperate defenders and destroyers. We think many young people might share our preferences.

One final thought: A Space Academy patterned after the military academies might be a very worthwhile national investment (See figure 37.). This academy might best be a 4- to 6-year institution which took in new students who had successfully completed 2 years of undergraduate work. The last 2 or 3 years might send some of the semifinished products into distinguished universities to gain their Ph.D.s under noted scholars, scientists, and engineers who had contributed to the state of the art in space.

Congressional appointments, paid tuition and salary, assured career entry, and other attributes of the service academies should be characteristics of this institution. A generation of fully prepared people is much more important than hardware or brick and mortar.

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