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more serious a limitation in the long run. It is already evident that even the shuttle's fuel-cell powerplant, basically an Apollo derivative, will limit several projected Spacelab and other missions. And fuel cells are only short-term power sources. The next commercial phase of space activity generally recognized as the development of new and improved communications functions will require substantially greater power than the maximum of a few kilowatts now available from current photovoltaic power supplies. Projections to more ambitious programs in the industrialization of space, which I will touch on later, identify on-board electric power as one of the principal limitations. Photovoltaic supplies might be able to be used up to perhaps 50 kW, but higher power levels, such as are needed, for example, by the space-based propellant processing system which General Dynamics has suggested as a means for expanding shuttle capabilities, probably require more compact systems. Yet, aside from one extremely high-risk 400 kWe heat-pipe-cooled reacter design employing even higher-risk thermionic converters, there are no nuclear reacter space power sources under active consideration today. And even the high-risk 400 kWe system study does not include a reacter technology development effort.

The final point of technical concern I wish to bring to your attention is the lack of a responsible, coherent research and technology program aimed at understanding the fabrication, deployment, utilization, evaluation, and maintenance of large structures in space. The preponderance of space activities which have been suggested for the late 1980's and 1990's will require not only the higher levels of onboard power I have already mentioned, but also the use of much larger

structures than those utilized heretofore.

These structures will be

too large to launch in prefabricated form, as was done with Skylab; they will need to be either assembled, deployed from prefabricated substructures, or actually manufactured in space, perhaps by servomechanisms in the early application stages, but eventually by people. And whereas there has been an impressive start made on the earliest conceptual formulation of such structural systems via a relatively miniscule NASA funding program, it now appear that the natural expansion of such promising early efforts is not to be implemented.

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The applications for such large structures are not limited to the far future. Our next generation of communications satellites are expected to perform a number of new functions in public service activities, in direct broadcasting, in navigation, in military reconnaissance and communications, and in many tight-beam communications applications, as we have described in a recent AIAA publication, "Space A Resource for Earth." These activities require not only more on-board power, as I said earlier, but also much larger antennas some perhaps hundreds of meters in diameter. Burton Edelson, in a recent article in the AIAA magazine Astronautics & Aeronautics, suggested an exciting concept to serve a multitude of these communications functions: the orbital antenna "farm".

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But we do not yet know whether our ideas on how to build, launch, control, maintain, and move these large antenna structures are feasible, practical, or cost-effective. And the use of space-bi

tions systems is not a wild-eyed dream of the future

communica

it is an area

of space activities that has been shown historically to be productive, profitable, and beneficial to people in every walk of life and in

virtually every nation on Earth. It would appear that a modest but growing NASA technology effort in this area would be well worthwhile.

Perhaps

The need for an active program on large space structures becomes even more significant for other areas of space industrialization, such as those described by many of the witnesses at these hearings. the most interesting of these longer-term prospects, the one having the most significant potential impact on the Earth's peoples, is the space-based solar powerplant. The magnitude of this concept tends to induce a severe case of "future shock" in many of the new Administration's officials, but even if actual deployment of such stations is still decades away, the preparatory research and technology problems associated with so large and so potentially important an effort should have already grown to a much larger portion of our federal energy budget than that which appears in the recently-approved Department of Energy "decision-making" study of the subject.

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But even if the power satellite concept should not prove out, there is a serious need for substantial activity beyond Spacelab to develop the in-space fabrication capabilities upon which so much of the projected future space effort depends. Thus, independently of the conclusions of the DOE space power satellite studies, NASA should substantially expand its efforts in this area of activity.

Before closing, I want to be sure to make clear one basic premise which is threaded throughout all the points I have attempted to make in this paper: the importance of a routine, reliable, reusable transportation system to get from the Earth's surface into orbit, namely the shuttle.

Without such a system, there can be little or

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no growth in our space activities, and therefore certainly not much in the way of "Future Space Programs".

Please also note that although I have touched on only four concerns which AIAA members have expressed, there are many other areas of NASA activity, particularly in advancing technological capability, in which too shortsighted a view can seriously prejudice the attainment of useful and viable space objectives.

BIOGRAPHY BRIEF FOR DR. JERRY GREY

Dr. Jerry Grey received his Bachelor's degree in Mechanical Engineering and his Master's in Engineering Physics from Cornell University; his PhD in Aeronatics and Mathematics from the California Institute of Tecnnology.

His early career included stints as a full-time Instructor of Thermodynamics at Cornell, an engine development engineer at Fairchild, a Senior Engineer at Marquardt, and a hypersonic aerodynamicist at the GALCIT 5-inch Hypersonic Wind Tunnel. He was a professor in Princeton University's Department of Aerospace and Mechanical Sciences for 15 years, where he taught courses in fluid mechanics, propulsion, and nuclear powerplants and served as Director of the Nuclear Propulsion Research Laboratory. He formed the Greyrad Corporation in 1959 and was its full-time President from 1967 to 1971. He is now Administrator of Public Policy for the American Institute of Aeronautics and Astronautics, where he spends half his time; the other half is devoted to consulting practice, writing, and lecturing. He is also Adjunct Professor of Environmental Science at Long Island University, where he teaches courses on energy, and President of the Calprobe Corporation, a supplier of high-temperature instrumentation based on Dr. Grey's patents.

Dr. Grey is the author of five books and over a hundred technical papers in the fields of solar energy, fluid dynamics, heat transfer, I ket and aircraft propulsion and power, plasma diagnostics, instrumentation, and the applications of technology. He has served as consultant to the U. S. Congress (as Chairman of the Office of Technology Assessment's Solar Advisory Panel), the Air Force, NASA, and ERDA, as well as over twenty industrial organizations and laboratories. He was Vice PresidentPublications of the AIAA for five years, and is listed in Who's Who in America, American Men of Science, Who's Who in Aviation, Engineers of Distinction, Contemporary Authors, and the United Kingdom's Blue Book and Dictionary of International Biography.