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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
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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
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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
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THE SDI POWER PROGRAM
89
operational SP-100 space power system would be a major product
of and a major benefit to—the 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.
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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
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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,
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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" rate—if 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
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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
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Representative terms from entire chapter:
power program
96
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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
98
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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]
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.
