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Executive Summary In late 1988, at the request of the administrator of the National Aeronautics and Space Administration (NASA), the National Research Council formed the Committee on a Commercially Developed Space Facility to assess the scientific and commercial benefit to the nation of having a Commercially Developed Space Facility (CDSF) in place prior to Space Station operations. The committee was to examine planned and anticipated microgravity research and manufacturing requirements of the federal government and commercial users as well as the extent to which existing, planned, and proposed capabilities and infrastructure could support these requirements. (See Appendix A for the full charge to the committee.) The committee was not charged with assessing the implications of various approaches to commercial development of space facilities or with estimating the costs of a CDSF. Thus, the committee's findings concentrate on the desirability of having an additional space facility in service in the interim preceding Space Station Freedom. The committee also examined the potential use of a CDSF to test and demonstrate Space Station and other advanced space technology, but found few applications in this area. Thus, the focus of its deliberations was on using a CDSF for microgravity experiments. What is the status of microgravitv science in 1989? Microgravity science and applications represent a broad, interdisciplinary area, less than twenty years old, encompassing fluid dynamics, materials science and processing, combustion, biotechnology, and life sciences research. Virtually all microgravity experiments in the United States, both governmental and private, are supported by NASA's Office of Space Science and Applications (OSSA) or its Office of Commercial Programs (OCP). These offices exist for different purposes, one for the advancement of science and the other to promote the commercial uses of space. In the field of microgravity research, the committee believes enhanced interaction between these offices, for example in reviewing proposed experiments, would increase the effectiveness of the national effort.

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The committee considers that microgravity science is at an immature stage due to lack of understanding of the fundamental processes involved in this area of space research. As more experimentation takes place, a data base of results will be acquired, and it will become possible to strategically plan the future microgravity research program. What would be the benefit to the nation of providing an orbiting manufacturing facility as early as possible? The committee found no evidence to suggest microgravity research would lead to significant space-based manufacturing in the next five to ten years. Rather, the deeper understanding of fundamental phenomena obtained from orbit, in the short term, will primarily be used to improve terrestrial processes. Do existing Shuttle-based facilities meet anticipated microgravity needs? Important parameters in microgravity research are the magnitude and direction of gravitational acceleration, the amount of power available to an experiment (especially important for experiments requiring furnaces), and flight duration (important, for example, for growing large crystals). Lack of flight opportunities and funding for flight experiments have been major constraints on the national microgravity program. In the last few years, however, NASA has responded to recommendations of both internal and external advisory groups with increased emphasis on future flight opportunities and with enhanced budgets. The committee studied the capabilities of existing Shuttle-based facilities for microgravity experiments. These generally offer acceleration environments of approximately 10" g and microgravity duration of approximately one week, although longer durations will be made possible by the Extended Duration Orbiter (EDO). With an EDO, 16-day Shuttle missions will be possible, and 28-day missions are also under consideration. While the amount of peak power available would remain unchanged, the total energy available would increase in proportion to the increased duration of the Shuttle mission. The committee found that over 85 percent of proposed experiments could be accommodated with a 16-day mission, and that a 28-day mission would accommodate virtually all of the remainder. Experiments or processes needing on-orbit duration greater than presently available include such things as biotechnology research with living cells and crystal growth. An examination of the projected requirements of OSSA and OCP experiments revealed that fewer than four percent need peak power levels greater than 2.0 kW, less than will be available through Shuttle-based facilities in the 1992-1997 time frame. Higher power levels enable more experiments to be conducted simultaneously, however. Thus far, with careful mission planning, experimenters have been able to work effectively around restricted electrical energy and total peak power. Based on mathematical modelling, some important experiments are believed to require accelerations with magnitudes lower that 10" g, but little experimental evidence is yet available about the need for such very low accelerations. The presence of humans, spacecraft

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docking, and thruster firings cause perturbations that have disruptive effects on microgravity research. It appears that some compound and alloy-type electronic and optoelectronic crystal growth experiments may require very low microgravity levels that can only be provided by a free-flyer. The committee believes the data base in this area is too limited to provide adequate information to make a final judgment. The committee found that the available and tentatively manifested experiments, power levels, anticipated flight durations, and the microgravity environment of the NASA Shuttle-based facilities would not impose serious constraints on the experiments planned by OSSA and OCP in the period from 1990 to 1996, recognizing that planning for the later years is far from firm. Existing and planned facilities will accommodate the vast majority of anticipated experiments, assuming the space transportation system is able to carry out a substantial fraction of its planned missions. In addition, if any of the commercial facilities on the horizon materialize, the committee believes there will be room for growth in the national microgravity program. The committee explored many proposed or planned U.S. and non-U.S. facilities for microgravity experiments. Many of these capabilities, as described in Chapter 4, are innovative, and they have varying individual advantages. What is the status of space automation technology and what is its relevance to the capabilities for a CDSF? The present generation of microgravity experiments is largely designed to be tended by humans, and approximately 40 percent of experiments to date have required unscheduled human intervention. Advances in automation, robotics, and telescience have been demonstrated in laboratories and industrial applications, but typically it takes 24 to 48 months to adapt well-understood microgravity experiments so that they can be conducted in an automated fashion. Data from presently planned microgravity experiments will, in many cases, be required in order to properly design robust experiments incorporating automation and robotics (A&R) and telescience to take advantage of free-flyers. Full automation and telescience techniques are essential if experiments are to be performed in a vehicle such as a CDSF where man will not be present when many experiments are performed. The time and costs of developing such experiment capabilities must be taken into account in reaching a decision to utilize a free-flyer in NASA's programs. What are the implications of Space Transportation schedules for the microgravitv program? The current Space Shuttle manifest through 1994 contains no reserve for contingencies; the committee believes that the flight rate projected for 1991-1994 is higher than will be achieved and that there may be a loss of opportunities for microgravity payloads during this period. However, the possibility also exists that not all manifested payloads will materialize. For example, some Department of Defense (DOD) bookings may not be required, and therefore more opportunities may eventually be available than now appear.

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The committee discounts the notion of developing a CDSF as insurance against lower flight rates or against a delay in the deployment of the Space Station. The usefulness of a CDSF remaining untended in orbit for long periods between Shuttle visits is likely to be limited given the level of maturity of microgravity experimentation, automation, and robotics. In addition, the minimum cost to NASA of a CDSF as insurance has been stated to be $700 million over four to five years, which rivals the total national support for microgravity programs (approximately $150 million in FY 1989). Is a CDSF required prior to Space Station operations? No. However, in the era of the Space Station, a U.S. long-duration, human-tended free-flying spacecraft for microgravity research may well have merit. The committee believes free-flyers eventually will be needed for microgravity research, development, and applications. But their use will be predicated on developing the knowledge base, hardware systems, and appropriate A&R and telescience needed to make them practical. Results of on-going flight experiment programs will be used to define meaningful classes of future experiments. The needs of these experiments will then dictate the detailed design of the free-flying platform. As a minimum, such a facility for microgravity activities should be readily accessible from the Space Station and compatible with it, yet have the advantages of a "clean" microgravity environment, and should be able to take advantage of expected advances in A&R and telescience. If there should be a delay in the initial operations of the Space Station of one to two years, the committee's judgment would not change. However, if it should become apparent that there will be a much longer delay, the committee recommends reconsideration of the need for additional flight opportunities for microgravity activities. This reconsideration should be based on progress in understanding the basic scientific processes that are involved, the status of automation, robotics, and telescience, and upon whether requirements for manufacturing can be identified. In such a case, consideration should be given to some of the more modest facilities described in Chapter 4 in trying to match requirements with capabilities. Although the potential benefits to the nation of microgravity experimentation lie in the future, the committee believes it is important to continue to explore this new frontier of human knowledge and to begin to build the foundation for eventual commercial exploitation of the space environment.