Click for next page ( 87


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 86
6 Commentaries on the SDI Power Program COMM1 NTARY ON SDI SPACECRAFT SYSTEM NEEDS AND THEIR IMPACTS ON THE SPACE POWER SYSTEM There are several spacecraft-level SD! system needs that could well affect the space power system but could not be assessed by the committee because of the limited scope of available studies. This recognition underlies the committee's recommendation for represen- tative all-up prelirriinary spacecraft designs (Recommendation 1~. The following list of system needs that require better definition is meant to be representative but not all-inclusive: . vehicle maximum stewing rates, presumably established by needs for retargeting; verification of spacecraft operational readiness; . vehicle-maneuvering requirements, including replenishment of orbital-drag losses as well as needs for evasive actions; . elimination of torques produced by spacecraft interaction with the earth's magnetic field; and . modification of spacecraft thermal and radar signatures. COMMENTARY ON SD] PROGRAM ISSUES In this section, the committee has highlighted the programmatic 86

OCR for page 86
THE SDI POWER PROGRAM 87 concerns it believes to be most important among the recurring space power issues confronting SDIO management. These issues are a. Balancing investment of resources between the near term and the Tong term. b. Coordinating the investment in basic technologies and com- ponents to produce timely results and to emphasize high-leverage items. c. Integration of SDI power supply systems with overall SDI systems. The dilemma posed in (a) above is apparent in both large and small examples. In Chapter 3, the point was made regarding nuclear power that failing to initiate and carry out the development of a multimegawatt power source would Signet SDI options for very-high- power electrically energized systems. Not so immediately obvious is the potential referred to in (b) for crippling the future by failing to develop critical advanced technol- ogy components needed by SDI, such as resistors, insulating materi- als, high-temperature structural materials, thyratrons, transformers, and so on. The unstimulated rate of improvement is, in many in- stances, not rapid enough. Stimulating power-system-component development will probably have beneficial unpacts on many techni- cal activities in addition to SDI, a factor in motivating Recommenda- tion 8. Issue (c) expresses the committee's concern that the overall space platform will impose demands on the power supply system not im- mediately apparent when examining the space power supply system in isolation. Active Program Management and Integration at the vehicle level can address the issues cited, and should examine with skepticism all estimates of development times and costs. The length of time required to design, develop, and qualify new power sources- especially nuclear ones must be a key consideration, a factor moti- vating Recommendations 4 and 8. With this introduction, a more detailed commentary on SDIO budget allocation and strategy follows. REVIEW OF THE SDI SPACE POWER PROGRAM The SDIO fiscal year (FY) 1987 and 1988 budgets, future projected budgets, and interviews with staff in the SDIO Power Program Office were used as data to deduce the current SDIO investment strategy

OCR for page 86
88 ADVANCED POWER SOURCES FOR SPACE MISSIONS for its space power program. This present strategy includes five elements: 1. Provide power for initial deployment based on chemical rock- ets and passive sensor platforms. 2. Conduct technical research and development for providing power to directed-energy weapons for discriminating decoys interac- tively and for killing boosters, postboost vehicles, and warheads. 3. Demonstrate enabling long-term technology. (An "enabling" technology is one that satisfies an applications requirement.) 4. Formulate future requirements to guide development. 5. Provide power for near-term SD! experiments and tests. Providing for near-term requirements (item 1) means enhancing survivable solar power in FY 1988 and beginning an exploratory ex- amination of a small nuclear reactor power system at approximately 1 percent of the FY 1988 SDIO space power budget. This shift is a direct response to near-term requirements, and shows technically agile and responsive program management. The high priority SDIO has assigned for conducting technology development for powering directed-energy systems (item 2) is nec- essary to advance the rate of progress in pulsed-power development and to avert a century of development to attain gigawatt power lev- els for space missions. Substantial R&D is required to reduce that time from a century to 1() 20 years. The emphasis on technology development is appropriately placed, and can provide for long-term SDI needs. Demonstrating enabling long-term technology (item 3) has led to continuing support for the SP-100, which was 48 percent of the FY 1987 budget and will be 30 percent of the FY 1988 budget. The SP-100 project could provide enabling technology that is suited for powering many missions in space, on the moon, and for exploration of the solar system. History has shown that it takes longer to develop a nuclear reactor system, such as SP-100, takes longer than to de- velop a space mission. Hence today's civil and military space project managers cannot include any nuclear reactor space power system or any other system in their mission planning until that system has been developed and tested. This dilemma is frequently referred to as the "chicken-and-egg syndrome." Consequently, support of the SP-100 program by the SDIO Power Program Officc in the absence of a commitment for a specific space mission shows a farsighted perspective, and this committee strongly endorses that strategy. An

OCR for page 86
THE SDI POWER PROGRAM 89 operational SP-100 space power system would be a major product of and a major benefit tothe SDI effort. The power portion of the SDI program is currently in a com- ponent development and technology phase. Until SDI weapons sys- tems have been more clearly defined, more aggressive advanced de- velopment and engineering of SDI power systems would in most instances be premature. Based upon the personal experience of several of its members, this committee finds that investment in large, narrow demonstrations is generally wasted if it is accomplished more than 6 to 10 years before deployment. Accordingly, this committee strongly encourages the development of generic, scalable space power technologies for the future, but believes that advanced development of specific space power systems should await improved specification of SDI weapons. The SP-100 is an exception, and is justified by its having broad applicability to civil and military space power missions and by its potential for providing experience on how to integrate puIsed-power systems in space. Development of technology for superconducting magnetic en- ergy storage (SMES) is a response to the power requirement for the ground-based (free-electron) laser, and is also motivated by a poten- tial spinoff to load leveling of commercial power. Enabling SMES technology could also result in substantial overall economic benefits to this country, in addition to technical benefits to SDI. The pace of developing repetitive, high-powered, pulsed-power systems needs to be accelerated as much as possible. Over the last several decades, the power available from continuously oper- ated repetitive puIsed-power systems has increased every decade by a factor of approximately three. In the early 1980s, average power levels of accessible terrestrial power-conditioning technology were in the neighborhood of 1 MWe. Given that technologies can usually be adapted to space, one could envision a multimegawatt capabil- ity in the early 1990s; however, pulsed-power systems for hundreds of megawatts to several gigawatts may be required for some SD! weapons platforms. Their development could require 40 to 60 years at the demonstrated historical extrapolation rate, making them un- available until about 2030 to 2050. It may be possibile to dramatically accelerate this rate in some areas by developing new materials and by stimulating innovative technological approaches to space power system applications. Such acceleration has already been achieved in the capacitor development program, and similar approaches are needed in other power areas.

OCR for page 86
go ADVANCED POWER SOURCES FOR SPACE MISSIONS The current emphasis on mult~rnegawatt space power systems seems to be appropriate, but the goad of the SDI space power pro- gra~n require several hundreds of megawatts. The next round of power architecture studies and power system studies must address the need for aggressively advancing space power technologies to the multihundred-megawatt class. Formulating future requirements (item 4) to guide development is an essential part of every technically challenging program. The three Space Power Architecture System (SPAS) studies (1988) constituting about one percent of the SDIO power program budget in FY 1987 were an initial attempt to establish relative priorities of various candidate space power system concepts. However, during the course of the committee's study, the SPAS studies had still not been published. Because the architects studied a wide variety of power systems and employed differing assumptions, the committee found it exceedingly difficult to make direct comparisons among the results of the three studies. Nevertheless, the requirements definition for those studies identified some key total-system issues, such as the effluent-tolerability issue. There is substantial interaction within SDIO between its Power Program Office and its programs dealing with kinetic energy weapons, directed-energy weapons, and sensors, ~ order to provide quaTita- tive and quantitative guidance for emphasis within the space power program. The committee finds that the SDIO Power Program Of- fice is being responsive to the changing needs of the other SDIO directorates by shaping its program accordingly. Providing power for near-term SDI experiments and tests (item 5) is an ancillary strategy. Superconducting Magnetic Energy Stor- age would support near-term testing of a ground-based free-electron laser (FEI.) if an SMES system were sited at White Sands, and would provide technology for future FEL tests if one were located elsewhere. Magnetohydrodynamic (MHD) power generation was di- rected to near-term SD! power requirements because the resulting effluents may make the use of MHD in space unattractive in the long-term. In addition to these basic strategies, the committee notes that SDI requirements often change. Various weapons systems have waxed and waned in popularity, resulting in shifting SDI power system re- quirements. Such shifts in requirements will continue as the major technical aspects of each weapon concept become better defined. The pursuit of long-term power system demonstrations should be

OCR for page 86
THE SDI POWER PROGRAM 91 buffered from such short-term fluctuations because significant re- sources and continuity would otherwise be wasted in starting and stopping demonstration projects. This is a factor leading to Recom- mendation 8. The space power technology development program, which can lead to large advances in capability, should also be protected from shifting requirements, because it has large potential long-term ben- efits for a relatively low annual investment. Thus this program re- quires consistent year-to-year support during a protracted develop- ment cycle. Program management issues were also examined during the study. The committee found that the relative power program fund- ing allocations among the five major program investment strategies being pursued have been reasonable. The SDIO power program has been responsive to the needs of SD] users, both to share in the long- term benefits of space power development and to transfer technology to them in order to achieve near-term gains. It will be very difficult to supply space power with assured reliability, provide it in a form matching user needs, and make it available promptly on demand dur- ing periods when it is needed. This difficulty needs to be appreciated within the various SDIO directorates. A more detailed examination of the SDIO space power program investment strategy for the FY 1987 and FY 1988 budgets follows. COMMENTARY ON THE SDI SPACE POWER INVESTM1:NT STRATEGY The SDIO space power program budgets for FY 1987 and FY 1988 were reviewed to deduce the current SDIO investment strategy for space power. The raw data are presented in Figures ~1 through 6-4. The total space power program budget increased from $80 m~- lion in FY 1987 to $95 million in FY 1988, and is distributed as shown in Figure ~1. Funding for integrated demonstrations made up almost half the total budget in FY 1987, and a lesser fraction in FY 1988. Research on components received roughly the same percentage, about 20 percent, in both fiscal years. Funding for research on generation technologies increased substantially in FY 1988 as funding for power systems studies including programmatic support decreased. Although the committee regarded the increase in funding in the area of generation technologies as well warranted,

OCR for page 86
92 - - - w~ I ~1 ~ . C) A o ~ O ~ . O _

OCR for page 86
THE SDI POWER PROGRAM 93 additional studies of the space power subsystem as an integral part of a space weapons system are a high-priority need. This recognition is reflected in Recommendation 1. Development of SP-100 is a joint program of the DOD (through SDIO), DOE, and NASA. Joint funding of SP-100 by the three agencies totalled about $60 million in FY 1987 and $99 million in FY 1988. The SP-100 was essentially the SDIO Power Program's only integrated demonstration during FY 1987, and received $38 million of SDI funding. In FY 1988 the SDIO portion of SP-100 funding was $25 million, and a new SMES program is funded at $13 million to provide a near-term capability. Cost sharing of the SP-100 program by other agencies permitted the total SP-100 program to grow, even though the SDIO funding component declined. Since all orbiting platforms will require housekeeping power, and the versatile SP-100 system has been designed to provide the range of powers needed for that purpose, the committee regards demonstration of a space nuclear reactor power system as one way of implementing Recommendation 4, since it would provide valuable experience in how to integrate various components into a space power system. The committee cautions, however, that growth in SP-100 fund- ing should not consume the remainder of federal funds allocated for SDI space power development. Thus, the committee reluctantly recommends slowing down joint SDI/DOE/NASA development of SP-100 but not below a ~critical" rateif that step is essential to preserve the SDI power technology program at a viable level. If a substantial portion of SP-100 funding can be provided by the DOE and NASA, SP-100 development can proceed without consuming the entire SDI power program budget. The committee strongly encour- ages SDIO to pursue these project partnerships aggressively to avoid erosion of its power technology development program. The SDIO strategy for FY 1988 maintains a strong power technology develop- ment program along with SP-100. Although the committee favors SD! funding of SMES, it is concerned that this not be accomplished at the expense of SP-100 development. There are five multimegawatt power generation technologies be- ing pursued with the $13 million in FY 1987 and $26.7 million in FY 1988 devoted to technology development. The subdivision of that sum is shown in Figure ~2. The multimegawatt nuclear power program, in collaboration with the DOE, is the largest program, but has a decreasing budgetary share from SDIO in FY 1988. The electrochemical technologies enjoyed reasonable growth. The major

OCR for page 86
94 .o ~ CM ~ o 00 (D oo CM a) fig . . or ~ Z J A 11 \ J \ LL O \ / 1~ \ Cat . . CC ~ Z at: ~ in ' \ i` 6 \ O \ ~ ' - Z \ - a> o o _ Lo - - .2t ~ C) U3/ cn ~ . / - ~ \ ~ ~ U. \ in cM \ us \ ~ \ b4 ~ /~ ,c, \ of ~ \ / ~ o ~ \ / o LLlCM \/ ,_ To so 3 o by, \ ~ o - C> . _ a) c) o ~ <) to Lii Cat 3 ~o ~d ._ - \ o ._ 1 ~ I ~ CQ .o d o C~ 1 ~ :>, - ,= o a)

OCR for page 86
THE SDI POWER PROGRAM 95 growth in R&D on survivable solar power technology reflects near- term needs. Because of its potential as a compact multimegawatt power source for weapons (with only the hydrogen used for thermal management as an effluent), the committee understands why nuclear power was a major portion of the program. The electrochemical program may be justified by the potential of fuel cells to provide rechargeable power for system start-up at battle time. The fuel cells can be arranged in modular series parallel combinations to minimize power conditioning. Battery research is being funded aggressively for a short time to stimulate rapid maturation of that technology. The MHD program, which grew substantially from FY 1987 to FY 1988, appears to command a disproportionate amount of funding. Such a spending profile might be justifiable to satisfy a near-term program need for powering ground tests if the project would make available a power facility for ground tests at lower overall cost than that of more conventional alternative technologies and if that facility could be available with high reliability. The large investment for a short time appears to be regarded by SDIO as the most cost-effective way to produce this near-term power source. The committee regards the effluents associated with an MHD space power system or with other open-cycle power systems as potentially incompatible with long-term SDIO needs for space power. The major decrease in funds for chemical technology is justi- fied because it is an off-the-shelf technology. Should this option be selected for deployment in space, its development, integration, and space qualification will require a major program. Component development is being broadly pursued in the pro- gram, receiving approximately $14 million of the FY 1987 funds, and $20.8 ganglion in FY 1988, divided as shown in Figure ~3. The large portion going to radio frequency power sources is a program response to the current emphasis on the neutral-particle beam and the free-electron laser. In FY 1987 the second largest budgetary portion, 19 percent, was for R&D on inductive storage and switching, a program element that is a holdover from prior commitments when electromagnetic launchers were given high priority in SDI. Funding trends for FY 1988 reduced this commitment appropriately. Funding for research on rotating machinery technology for power conditioning grew from FY 1987 to FY 1988 because that technology permits reasonable pulse compression to the millisecond range. The committee understands that current-collection technology is a major

OCR for page 86
96 CO or oo ~ . . Z . ~ Z or ' in LL ~ o it_ 1 ~ `:,,c O Con C ~ ~ o .CD C CIo Cl) ~ w// \ - /,~ ._ c, ~ \ / oc OCR for page 86
THE SDI POWER PROGRAM 97 limitation and, as such, it represented 14 percent of the total budget in FY 1987. The effort on current collection associated with large inductive storage and switching is appropriately reduced in FY 1988. The current-collection work for general power conditioning may be continued if improvements in power conditioning capabilities are required. The capacitor development program, at 12 percent to 13 percent of total funding, has been an outstanding success. The application of science to enable creating materials for high-strength, high-energy- density capacitors in the current SD! program has been quite im- pressive. This successful and exemplary development of high-energy- density capacitors and the demonstration of their reliability are likely to have very broad applications in SDI, tactical defense, and a large number of significant civil and military programs. Budget allocations for exploration and development of thyra- trons, solid-state switches, and magnetic switches are reasonable. It would be highly clesirable for science to be brought to bear in cat- alyzing the development of these devices with the goal of successes sirn~lar to those achieved in capacitor development. In contrast to development of the above technologies, develop- ment of inverters, at 3 percent in FY 1987 and 0.7 percent in FY 1988, seems grossly underfunded, and the funding trend is in the wrong direction. In particular, there is currently no development of tech- nology for the high-duty-factor solid-state switches, transformers, and capacitors required for multimegawatt inverters. This deficiency should be corrected by implementing an aggressive inverter program, including the component development needed for those inverters. System and system technologies have three explicit subdivisions totaling approximately $12 million. As shown In Figure ~4, most of these funds are to define requirements, conduct surveys, fund pro- gram management of the SDIO Power Program Office, obtain pros gram advice, and support the independent evaluation group (IEG). Studies on thermal management are broadly applicable to aD candidate power system concepts, and are strongly supported by the committee. Although survivability ~ not explicitly caned out in any of the work package directives, it appears to be included in the work of the lEG. From FY 1987 to FY 1988, the 38 percent reduction of funding for resolving environmental concerns would be of concern if it were to result in delaying resolution of the effluent issue. The capability of SDI weapons platforms to function when immersed in their own

OCR for page 86
98 / ~ '\~ \ / a, \ / o ~ o . C) a) ~ ._ a' _ C oo E tic ~ ~ ~ ~ I f . . , ~ o -

OCR for page 86
THE SDI POWER PROGRAM 99 effluents will have a strong unp act on the selection of candidate mul- timegawatt technologies. If no effluent can be tolerated, the extra mass of closed-cycle systems will be costly. If hydrogen is the only acceptable effluent, then space power systems would be restricted to that effluent, and storage would be required aboard the spacecraft of chemical combustion products or of effluents from nuclear open-cycle power systems. As stated in Conclusion 3 and Recommendation 2 (Chapter 3), the committee recommends a concerted study of the effluent issue to discriminate among power options before selecting the most promising approaches. Of course, if some weapons plat- forms can tolerate substantial effluent, the improved power-per-unit mass from the open-cycle systems and the reduced reliance on the nuclear option with its associated environmental and survivabil- ity problems may justify developing several multimegawatt power options. PINDING, CONCLUSION, AND RECOMMENDATIONS Based on the discussion in this chapter, the committee arrived at the following finding, conclusion, and recommendations: Finding 7: The present overaB 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. Conclusion 6: Refocusing SDIO resources towarc] near-term weapons systems demonstrations could delay development of ad- vancec] power technology, and thereby seriously jeopardize meeting long-term space power program objectives. Recommendation 3b: The SP-100 nuclear power system is am plicable both to SD! requirements and to other civil ant] military space missions. Therefore, SP-100 development shouic] be completed, following critical reviews of SP-100 performance goals, design, ancl - c .eslgn margme. Recommendation 3c: SD] burst-mode requirements exceed by one or more orclere of magnitude the maxims power output of the SP-100. Therefore, both the nuclear and nonnuclear SD]

OCR for page 86
100 ADVANCED POWER SOURCES FOR SPACE MISSIONS mult~megawatt programs shoed be pursued. Hardware develop- ment should be coordinated with the results of implementing Rec- ommendation 5. Recommendation 4: Consider deponing the SP-100 or a chem- ical power system on an unmanned orbital platform at an early date. Such an orbital Swan sockets could power a number of scientific and engineering e~erimente. It would concurrently prwide experience relevant to practical operation of a space power system singular to systems that might be required by the SD! alert and burst modes. Recommendation 8: To farther U.S. capabilities and pro- gress m civil as well as military applications of power technology, both on the ground and in space, and to mamtam a rate of progress in advanced technologies adequate to satiny national needs for space power, plan and implement a focused federal program to develop the requisite space power technologies and systems. This program based on a multlyear federal commitment- shoed be at least as large as the present combined NASA, DOD (mchldmg SDIO), and DOE space power programs, independent of the extent to which SD! itself is funded.