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APPENDIX Compilation of Study Findings' Conclusions, and Recommendations Following is a compilation of the study findings, conclusions, and recommendations. FINDINGS The committee arrived at the following findings: Pending 1 (Chapter 2~: Of the three significantly different SDI modes of operation (housekeeping, alert, and burst mode), require- ments for the alert mode are inadequately defined, yet they appear to be a major design-deterrn~nant. For that mode, the unprecedented high power levels, durations, and unusual time-profiles-as well as the associated voltages and currents-which are envisioned will usu- ally make extrapolation from previous experience quite risky and unreliable. A possible exception is in the area of turbine technol- ogy, where an adequate range of power leveb has been validated for terrestrial applications, although not for flight conditions. Proposed space power systems will need to be space qualified for long-term unattended use. Finding 2 (Chapter 4~: The space power subsystems required to power each SDI spacecraft are a significant part of a larger, complex system into which they must be integrated, hence for obtaining a 129

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130 APPENDIX E valid analysis they cannot be treated completely separately. (See Conclusion 2 and Recommendation 1.) Finding 3 (Chapter 4~: Existing space power architecture sys- tem studies do not adequately address questions of survivability, reliability, maintainability, and operational readiness that is, avail- ability on very short notice. F~ndmg 4 (Chapter 4~: Existing SDI space power architecture system studies do not provide an adequate basis for evaluating or comparing cost or cost-e~ectiveness among the space power systems examined. Finding 5 (Chapter 2~: Among the power systems that are candidates for SD! applications, the least massive, autonomous self- contained space power systems currently being considered entail tol- erance of substantial amounts of effluent during system operation. The feasibility of satisfactorily operating spacecraft sensors, weapons, and power systems in the presence of effluent is still unresolved. Finding 6 (Chapter 3~: Beaming power upward from earth by microwaves or lasers (see Recommendation 6) has not been exten- sively explored as a power or propulsion option. Finding 7 (Chapter 6~: The present overall rate of progress in improving the capability of space power-conversion and power- conditioning components appears inadequate to meet SD] schedules or NASA needs beyond the Space Station. Finding 8 (Chapter 3~: The time needed for the development and demonstration of a U.S. space nuclear reactor power system currently exceeds the time required to plan and deploy a mission dependent upon that power source. CONCLUSIONS The committee reached the following conclusions: Conclusion 1 (Chapter 2~: Multimegawatt space power sources (at levels of tens to hundreds of megawatts and beyond) will be a necessity if the SD] program is to deploy electrically energized weapons systems for ballistic missile defense.

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APPENDIX E 131 Conclusion 2 (Chapter 43: Gross estimated masses of SDI space power systems analyzed in existing studies appear unacceptably large to operate major space-based weapons. At these projected masses, the feasibility of space power systems needed for high-power SDI con- cepts appears impractical from both cost and launch considerations. Avenues available to reduce power system costs and launch weights include (a) to substantially reduce SDI power requirements; (b) to significantly advance space power technology. Conclusion 3 (Chapter 3~: The amount of effluent tolerable is a critical discriminator in the ultimate selection of an SDI space power system. Pending resolution of effluent tolerability, open-cycle power systems appear to be the most mass-effective solution to burst-mode electrical power needs in the multimegawatt regime. If an open-cycle system cannot be developed, or if its interactions with the spacecraft, weapons, and sensors prove unacceptable, the entire SDI concept will be severely penalized from the standpoints of cost and launch weight (absent one of the avenues stated in Conclusion 2, Chapter 4~. Conclusion 4 (Chapter 2~: The rate of rme ("ramp-rate" ~ from zero to full burst-mode power level appears to be a critical require- ment. It is not apparent to the committee what relationships exist among elapsed time for power build-up and system complexity, mass, cost, and reliability. Conclusion 5 (Chapter 5~: Major advances in materials, com- ponents, and power system technology will be determining factors in making SDI space power systems viable. Achieving such advances will require skills, time, money, and significant technological innova- tion. The development of adequate power supplies may well pace the entire SDI program. Conclusion 6 (Chapter 6~: Refocusing SDIO resources toward near-term demonstrations could delay development of advanced po- wer technology, and thereby seriously jeopardize meeting long-term space power program objectives. Conclusion 7 (Chapter 3~: A space nuclear reactor power sys- tem, once available, could serve a number of applications- for ex- ample, in NASA and military missions requiring up to 100 kWe of power or more in addition to SDI.

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132 APPENDIX E Conclusion 8 (Chapter 2~: Survivability and vulnerability con- cerns for SDI space power systems have not yet been adequately addressed in presently available studies relevant to SD} space power needs. RECOMMENDATIONS The committee arrived at the following recommendations: Recommendation 1 (Chapter 4~: Usmg the latest available ~nfor- mation, an in-depth fuB-vehicle-eystem preliminary design study-for two substantially different candidate power systems for a common weapon platform-sho~d be perfonned now, m order to reveal sec- ondary or tertiary requirements and limitations in the technology base which are not readily apparent in the current space power ar- chitecture system studies. Care should be exercised in establishing viable technical assumptions and performance requirements, includ- ing survivability, maintainability, availability, ramp-rate, voltage, current, torque, effluents, and so on. This study should carefully define the available technologies, their deficiencies, and high-leverage areas where investment will produce significant improvement. The requirement for both alert-mode and burst-mode power and energy must be better defined. Such an in-depth system study will improve the basis for power system selection, and could also be helpful in refining mission requirements. Recommendation 2 (Chapter 3~: To remove a major obstacle to achieving SD] burst-mode objectives, estimate as soon as practicable the tolerable on-orbit concentrations of effluents. These estimates should be based to the maximum extent possible~n the results of space experiments, and should take into account unpacts of effluents on high-voltage insulation, space-platform sensors and weapons, the orbital environment, and power generation and distribution. Recommendation 3: Rearrange space power R&D priorities as follows: a. (Chapter 3) Give early, careful consideration to the regu- latory, safety, and National lDn~rironmental Policy Act re- qu~rements for Mace nuclear power systems Tom manufac- ture throw launch, orbital service, safe orbit requirements, and disposition.

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APPENDIX E 133 b. (Chapter 6) The SP-100 nuclear power system is applicable both to SD] requirements and to other civil and military space missions. Therefore SP-100 development should be completed, following critical reviews of SP-100 performance goals, design, and design margins. c. (Chapter 6) SOT burst-mode requirements exceed by one or more orders of magnitude the maximum power output of the SP-100. Therefore both the nuclear and nonnuclear SD! mult~megawatt programs should be pursued. Hard- ware development should be coordinated with the results of implementing Recommendation 5. Recommendation 4 (Chapter 6~: Consider deploying the SP- 100 or a chemical power system on an nn~nned orbital platfonn at an early date. Such an orbital "wall sockets could power a number of scientific and engineering experiments. It would concurrently provide experience relevant to practical operation of a space power system similar to systems that might be required by the SDI alert and burst modes. Recommendation 5 (Chapter 5~: Make additional and effec- tive m~restments now in technology and demonstrations leading to advanced components, inclu~mg but not limited to: thermal management, including radiators; . materials structural, thermal, environmental, and super- conductmg; electrical generation, conditioning, switching, transmission, and storage; and . long-term cryostorage of H2 and O2. Advances in these areas will reduce power system mass and environ- mental impacts, improve system reliability, and, in the long term, reduce life-cycle power system cost. Recommendation 6 (Chapter 3~: Review again the potential for ground-based power generation (or energy storage) with subsequent electromagnetic transmission to orbit. Recommendation 7 (Chapter 2~: After adequate evaluation of potential threats, *farther analyze the subject of ndnerabdity and survivability, mainly at the overall system level. Data resulting from implementing Recommendation 1 would be appropriate for this

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134 APPENDIX E analysis. Pending such analysis, candidate power systems should be screened for their potential to satisfy interim SDIO survivabil- ity requirements, reserving judgment as to when or whether those requirements should constrain technology development. Convey the screening results to the advocates of those candidate power systems, to stimulate their finding ways to enhance survivability an they de- velop the technology. Recommendation 8 (Chapter 6~: ICb further U.S. capabilities ant! progress In civil as well as military applications of power tech- nology, both on the ground and in space, and to maintain a rate of progress In advanced technologies adequate to satisfy national needs for space power, plan and implement a focused federal pro- gram to develop the requisite space power te~mologies and systems. This program-based on a umItlyear federal commitment~hould be at least as large as the present combined NASA, DOD (including SDIO), and DOE: space power programs, Independent of the extent to which SD! itself is funded.