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III Other Critical Technologies for the Human Exploration Initiative Ongoing development of certain specific technologies is essential to the HEI and offers potentially high payoffs in capabilities and long-term cost savings. The committee assumes that HEI technology development will complement rather than displace the NASA program of basic research and technology development in such areas as materials and structures, sensors, air-breathing engines, and data processing. THE NASA 90-DAY STUDY The Technology Assessment section (Chapter 8) of the 90-lDay Study lists seven technologies (regenerative life support systems, aerobraking, advanced space engine, surface nuclear power, in-situ resource utilization, radiation protection, and nuclear thermal rocket propulsion). It continues with "other technology needs, briefly sketched" under titles like "humans in space." Although the NASA Figure 8-1 envisions focused research that does not continue after five years, ongoing advanced technology research will clearly be characteristic of the HEI for many years. The committee agrees that these technologies are important, but be- lieves that strategies for development of technologies should take account of the lead times required and incorporate priorities according to whether the technologies are essential to the HEI, or serve to enhance capabili- ties. For example, provision of radiation protection, life support, and crew safety are survival imperatives for all human space-based modes, and must be addressed as major architectural considerations. Research on artificial 17

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18 HUAL4N EXPLORATION OF SPACE gravity should be added to this list. On the other hand, aerobraking, ~n-situ resource utilization, and nuclear thermal rocket propulsion technologies may offer significant advantages In certain mission scenarios, but are not essential for human missions in general. There are other specific new technologies, not in NASAs list of seven critical technologies, that can profoundly simplify and enhance opera- tions In every mission scenario. Into clear examples are (1) advanced human/machine systems for tasks in space, in order to improve the ef- ficiency of humans, and (2) far more capable information management systems for mission decision making. While the 90-Day Study recognizes advances in information systems and automation and robotics as being im- portant to the success of the HEI, the emphasis should be on technologies that go one step farther, to greatly advanced computer-aided mechanical extensions of human performance, i.e., human/machine systems. ARTIFICIAL GRAVITY Artificial gravity was not included in the NASA list of critical tech- nologies. With the current state of knowledge, a multiyear exposure to weightlessness, even with on-board exercise and countermeasures and an intermediate stay on the surface of Mars, presents unacceptable risks to the crew. Adaptation to microgravity makes return to a gravity environ- ment dangerous and renders human performance on the surface of Mars problematical. The questions of whether artificial gravity will be required and, if so, how it will be provided are critical. The nation has no strategy for research to determine the need for or provide artificial gravity. Several alternative approaches to addressing the problem can be con- sidered. In one, an early commitment could be made to provide artificial gravity in the transfer vehicle to Mars. This option is not included in the 90-Day Study, but has been reviewed by NASA in the past and found to increase the mass of a Mars transit vehicle by no more than 20 percent, under the most conservative assumptions. Another alternative is to determine the requirements for artificial gravity by testing humans in a variable-gravity research facility in LEO. Such a facility should permit research on human physiological Reconditioning and countermeasures, including different artificial gravity radii and rotation rates, in order to determine the optimal combination of gravity levels and exposure times. Because of time considerations in human Reconditioning phenomena, an operational research period lasting two to six years must be anticipated before definitive answers about artificial gravity can be expected. Short of undertaking long-duration research on human performance in space, any research strategy for minimizing human risk of irreversible or incapacitating Reconditioning should make maximum use of ground and

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OTHER CRITICAL TECHNOLOGIES 19 space station facilities for relevant life science research. Ground bed-rest studies and incremental duration exposure of subjects in a space station must be integrated with animal research in orbit, including use of the SSF on-board centrifuge. In parallel with these tests, the effectiveness of several candidate countermeasures to Reconditioning should be evaluated in controlled experiments. If the Reconditioning is unacceptable and the simpler countermeasures are ineffective or onerous, full-scale space-based artificial gravity evaluation and facility development become imperative. Another alternative approach, which is less thorough than the use of a variable-gravity research facility but which could be carried out in parallel with a lunar base development, is an investigation of the effectiveness of lunar gravity as a long-term countermeasure. This approach would provide Reconditioning data at three levels: O. 1/6, and 1 g. It would not, however, help with the question of gravity gradient or contribute to any of the engineering issues regarding a spinning spacecraft for Mars transit.This approach is the most limited and time consuming. It also carries with it the risk of negative results that would require the eventual, but delayed, artificial gravity investigations described above. ADVANCED HUMAN/MACHINE SYSTEMS Mechanical and computer-aided extensions of human (astronaut) man- agers can provide enhanced efficiency in inspection, assembly, maintenance, repair, and exploration tasks. The most powerful approaches to human ex- ploration will integrate humans with machine systems to accomplish more than either can do alone. These approaches can range from low-level, hand-in-glove teleoperation, through higher-level object-motion commands, to planned task commands by a distant astronaut. Application of the many automation and robotic systems needed to integrate humans and machines can range from some of the early systems developed for space station man- agement and operations, to precursor nonhuman missions, to advanced synergistic systems of humans and machines operating on another planet. Advanced human/machine systems are not merely an enabling tech- nology, but a requirement for practical HEI operations. Technical advances can extend profoundly the human role as master of highly flexible human surrogates, but obtaining such potential benefits will require more than complex robotry and automation. NASA presentations based on the 90- Day Study implicitly recognize this by grouping operations in functional categories. Systems that integrate automation and robotics with humans permeate the arenas of vehicle maneuvering; vehicle servicing in space; in-space and surface assembly and construction; planetary rovers; surface operations; extravehicular activity and exploration; sample acquisition, anal- ysis, and preservation; and scientific probes and penetrators. Reduction of

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20 HUA~1N EXPLORATION OF SPACE EVA time alone probably will lead to increased efficiency and will increase safety. Most of the technologies discussed above and in the NASA plan require long lead times. In many cases the basic research has barely begun. make the HEI possible, the research foundation will have to be laid in the areas listed in the NASA report and in such fields as artificial gravity, more capable information systems, and human/machine systems. The time at which these technologies are successfully developed is important to the pacing of the progression from the Moon to Mars.