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9 Human Presence in Space SPACE AGE SCIENCE It is difficult to deterrn~ne which of the scientific projects contemplated in this study, other than those in space medicine, compel the presence of humans in space. ~ fact, there may be no others. With sufficient resources, we might devise automated systems that could substitute for people, performing all of the nec- essary functions usually associated with humans. People would, in turn, control the machines from Earth. On the other hand, it appears that under certain circumstances people are able to function productively ~ space and perform tasks In support of sci- entific investigations. At present, we lack enough "formation to judge where the balance between manned and unmanned missions should lie. Some space science rn~ssions at the beginning of the twenty- first century may be ~ntencled to pave the way for the expansion of humanity into deep space. For many reasons, not all scien- tific, human activities may extend into an increasing arena of space. With the advent of space stations, plans are already being made by a number of national space agencies for the continuous presence of men and women in low earth orbit, beginning in the 76

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77 l990s. Such activities ~ the next century may extend to geosyn- chronous orbit, and possibly to the regions of the I,4 and L5 points. The National Commission on Space has also expressed interest in establishing inhabited stations on the Moon and Mars. Space science practiced at the frontier requires a wide variety of inno- vations in observational and control capabilities, instrumentation, and propulsion methods. Thus, the pursuit of space science and its supporting functions should be a powerful driver of advanced technology, extending the capabilities of unmanned spacecraft. Advances In the technology of sensors, robotics, artificial mtelli- gence, and parallel computation may enable the development of a new generation of autonomous decision-making machines that will extend exploration ant] intensive study into remote parts of the solar system and eventually beyond without a human presence. Earth orbit can become a proving ground for the deployment of robots, automated observatories, and advanced data management systems. TEE SCOPE OF HUMAN PRESENCE IN SPACE The space stations of the United States and the Soviet Union are the first steps toward a sustained human presence in space. It is impossible now to predict either the pace or the ultimate extent of this expansion into space. The human-inhabited sphere may never extend beyond low earth orbit. Whether its boundaries are near Earth, on the surface of Mars, or somewhere else, this human-inhabited sphere wiD be the base from which many fu- ture space science investigations are conducted. Conversely, these investigations will provide the foundation needed for continued expansion of this sphere, if caned for. Space science experiments, tended in space by human beings, may provide the most important rationale for the staging, assembly, maintenance, repair, and oper- ation of major space facilities (e.g., space astronomical telescopes, earth science experunent payloads/platforms, launch vehicles for planetary missions). The steering group expects that the sphere of human presence in space will have relatively distinct boundaries. Within this sphere human presence unit be pervasive and well-supported. Many scien- ti~c investigations Urals be carried; out under direct human supervi- sion, much as they are on the ground; others will be conducted in

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78 a largely automatic mode, with general superv'mon from scientists on Earth or perhaps elsewhere within the inhabited sphere. This confinement of human activities to regions where they can draw upon a host of well-established facilities Is advisable for two reasons. First, the capability of humans to make judgments is optimized when there ~ an opportunity for adaptation, over a long period of tune, to the new environment. Second, human manipulative and observational skills can rarely be used electively without the support of a large array of sophisticated instruments, ma~hir es, and facilities. Neither of these two conditions is gener- aDy met by brief forays of human beings into regions far from the facilities that support their sustained presence. This applies to manned excursions to Mars, for example, if the human-inhabited sphere ~ restricted to space near the Earth. Further, it is important to recognize that the limitations on human survival in space are not weld known. At present, we are not certain that mission times can be extended greatly beyond those already experienced, even with considerable technological progress. Low gravity leads to loss of bone mass and other phyla ical effects. High-energy, heavy ion radiation causes irreversible damage to cells, including brain cells. Human relationships in a small, isolated group can badly deteriorate arch lead to the loss of functional capabilities. We have not demonstrated the feasibility of a closed ecological system yet, and resupply at a great distance for a long period could be formidable. We must address these issues before we can reach a final decision about the nature and extent of human involvement in expanding the frontier of space.