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11
Overall Findings and Recommendations
CURRENT EMPHASIS AND JUSTIFICATION
NASA currently is focusing on more frequent use of smaller, more technically
advanced, and less expensive scientific spacecraft to replace large, expensive, one-of-a-
kind spacecraft. This approach is intended to promote not simply a specific category of
technologies and missions with a lower cost, faster development ant} launch time, and
higher tolerance for risk but also a space program that enhances productivity and
economic competitiveness.
Small spacecraft already have server! a long-stanciing role in space physics,
astrophysics, and planetary missions, notably at GSFC and at JPL, which predates the
recent enthusiasm for small spacecraft. With decreasing NASA budgets projected for at
least the next five years and with over 50 percent of NASA's overall budget allocated for
the Space Station, the Space Shuttle, and Mission to Planet Earth, the Pane! on Small
Spacecraft Technology believes the increaser} emphasis on small spacecraft is well placed
if NASA is to have a meaningful science program in the future (Goldin, 19931. Although
small, less-expensive spacecraft cannot satisfy all potential mission requirements, such
as manned exploration ant! more demanding science missions, the pane! believes they can
contribute to the revitalization of the space program. Further, more-frequent ant! less-
expensive missions can help to promote structural and cultural changes that are vital to
the future of the space program considering the current budgetary and political
environment. These changes include increased opportunities for infusion of new
technology in ongoing programs, along with an increased tolerance for technological risk;
overall improvements in program responsiveness, versatility, and cost-effectiveness; and
economic competitiveness in both aerospace and nonaerospace industries.
SMALL SPACECRAFT CAPABILITIES
While the pane! believes that for many missions small spacecraft have the
potential to achieve the mission requirements with capability approaching that of tociay's
large spacecraft, it must acknowledge that even with the application of currently available
technology, today's small NASA spacecraft have limitations. Furthermore, not all small
83
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84
Technology for Small Spacecraft
spacecraft missions are simultaneously faster and less expensive, since technology
research and development for miniaturization can be expensive. However, the pane!
believes that with a vigorous technology-development and miniaturization program that
focuses on areas that provide the highest payoff, small spacecraft, either singular or in
constellations, can be used to achieve increasingly significant mission requirements.
RESPONSE TO TASK STATEMENT
The task statement for this study asked the pane! to
review the National Aeronautics and Space Administration's (NASA) plans
for a new small spacecraft technology-development program;
review NASA's current technology program and priorities for relevance
to small spacecraft, launch vehicles, and ground operations;
examine small spacecraft technology programs of other government
agencies;
assess technology efforts in industry that are relevant to small spacecraft,
launch vehicles, and ground operations; and
identify technology gaps and overlaps and prioritize areas in which greater
investments are likely to have high payoff, considering the current and
projected budgets, the NASA mission statement (see Appendix A), and the
needs of industries that utilize space.
Review of NASA's Small Spacecraft Technology Program
While NASA's technology program has not, until recently, been focused on small
spacecraft, NASA has had several development programs for small scientific spacecraft
in the past, which used advanced technology that was developed, to a significant degree,
by DoD and industry. The current NASA development programs for small scientific
spacecraft include the ongoing Small Explorer program at GSFC and NASA activities in
support of small DoD spacecraft, such as Clementine and MSTI.
In addition to the existing activities, OACT recently established the Small
Spacecraft Technology Initiative and the Office of Space Science initiated the Discovery
program to develop a series of smaller scientific spacecraft. The first two Discovery
missions, which are both scheduled for launch in 1996 are JPE's Mars Pathfinder and
the Applied Physics Laboratory's Near Earth Asteroid Rendezvous. Appendix D gives
a more complete summary of NASA small spacecraft programs.
The goals of the OACT Small Spacecraft Technology Initiative are to develop and
infuse technology into planned missions and to demonstrate a new approach to small
spacecraft technology integration through development and flight of several small
spacecraft. Because of the recent establishment of OACT's Small Spacecraft Technology
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Overall Fir~ings and Recommendations
Initiative, small spacecraft technology-development activities may receive greater
emphasis in the future.
It is the intent of OACT to infuse technology into proposed internal NASA
development programs for small spacecraft. A new ethos of technology infusion should
be actively promoted by NASA, and project managers should be encouraged to
incorporate new technology into all future small spacecraft missions. The pane} believes
that every space mission could contribute substantially to the achievement of NASA's
larger mission if every mission were also, to one degree or another, a flight test of new
technology.
The project management philosophies utilized for the GSFC and JPE small
spacecraft development programs and the one proposed for the OACT Small Spacecraft
Technology Initiative ant! the Of lice of Space Science's Discovery program are markedly
different. In the case of GSFC and JPL programs, spacecraft design and integration and,
in many cases' the manufacturing effort, are largely kept within NASA centers, while
inclustry's role is limited to that of support contractors and subsystem suppliers. Project
managers of the Discovery missions and the OACT Small Spacecraft Technology
Initiative propose to place responsibility for spacecraft concept, design, and integration
with a prime contractor ant! utilize NASA in a support and oversight role.
The pane! believes that each approach has merit. The internal NASA "prime
contractor" role provides NASA a means for conducting special missions where a NASA
lead is considered necessary and also provides an excellent training ground for future
NASA project managers. However, it tends to impede the transfer of technology to
industry, where it can be used in support of future NASA programs, and, perhaps more
importantly, to commercial initiatives and to programs of other agencies. Having an
industry prime contractor lead with support from other industry partners, universities,
anti NASA, places the technology in the hands of industry where it is more likely to be
applied commercially. The pane] believes that NASA should continue an active internal
technology development program for small spacecraft, as discussed in the following
section, independent of the project management approach.
Assessment of the NASA Technology Priorities for Relevance to Small Spacecraft,
Launch Vehicles, and Ground Operations
The establishment of the Small Spacecraft Technology Initiative appears to have
heightened emphasis, in NASA technology planning circles, on team operations involving
industry, university, and NASA interaction on specific space missions, with accentuated
industry leadership. "Customer needs," "user needs," anti technology transfer capability
have received considerable emphasis from NASA management as the primary strivers of
NASA's research and development efforts. While this emphasis is certainly healthy in
establishing relevant foci for NASA's technological activities and providing a vital
framework for intensive efforts, the pane! is concerned that overemphasis on this
approach may lead NASA to overlook its responsibility to the long-term development of
generic space technology. A mix of direct mission support, especially for NASA's own
85
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86
Technologyfor Small Spacecraft
space-science projects, and generic research on a variety of advanced technology special
topics should be pursued. Adequate funding for technology development is required for
NASA to successfully implement this approach. Especially since the defense budgets are
decreasing, NASA must be able to support its own requirements for technology research
and development.
The specific technology recommendations of this report are generally of a
relatively short-term nature and do not address the need for a more generic research and
development program that will support future generations of small spacecraft systems.
It is the opinion of the panel that the recommendations of this report, coupled with such
a generic technology-development activity would, over both the short and long term,
enable the execution of meaningful space-science programs and economically attractive
commercial space ventures using small spacecraft.
In recent years, several high-level study groups have been very critical of the
level of funding committed to NASA's technology development program. The groups
have recommended funding levels that range from a level of 7 to 10 percent of NASA's
total budget (NRC, 1987) to a factor of three increase of the 1990 technology budget
(NASA, 19901.
This panel recognizes that the level of expenditure for technology development
should be related to NASA's long-range plans for future programs. As of this writing,
several elements of NASA's overall plan are apparent to the panel:
.
.
an international space station that uses existing systems for placement in
orbit;
Mission to Planet Earth, which uses existing systems for orbit placement;
use of small spacecraft for future Earth and planetary science programs;
technology to support the commercial industry; and
technology development to support a later decision for manned exploration
of space.
As can be seen from this list, several different types of programs must compete
for technology development funds within NASA. The panel notes that although the
NASA Administrator strongly supports using small spacecraft for scientific missions, the
same support was not reflected in Congress' fiscal year 1994 budget, where the Small
Spacecraft Technology Initiative received only $12.5 million of the $30 million
requested. Since the fiscal year 1995 budget only recently was submitted to Congress,
it was not clear at the time of this report whether Congress would support NASA's $47.9
million request for the Small Spacecraft Technology Initiative. While small spacecraft
based on currently available technology have significant capability, their ability to
conduct more-meaningful science programs at affordable cost could be greatly enhanced
through technology development. Recognizing the great potential to be clerivec! from
research and development of advanced technology for small spacecraft, the panel
recommends that an adequate level of funding be provicled to ensure the achievement of
that potential.
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Overall Findings and Recommendations
The pane! has not made specific cost estimates for each of its recommendations.
This was considered to be beyond the panel's capability in the time it was able to
dedicate to the study. It is the paneT's belief that each of the recommendations that has
survived its critical review and appears in this report should be funded and carried to the
point where it is completed and the technology is ready for use or to the point where it
is apparent that there is a better course to follow.
The pane! leaves it to NASA to determine the cost of the recommended
technology program for small spacecraft, and to make evaluations of the potential
contributions of the recommendations to the health and vigor of the future NASA ant!
commercial space programs. In the event that it is determined that a substantial increase
in the NASA research and development budget is indicated in order to conduct the
program in a timely manner, NASA should rearrange its budget priorities to
accommodate the required level of funding for research and development and make the
case with the Administration ant! the Congress for the substantial increase.
Small Spacecraft Technologies of Other Government Agencies and Technology
Efforts in Industry that are Relevant to Small Spacecraft, Launch Vehicles, and
Ground Operations
The pane! was briefed by numerous government agencies and companies
regarding the activities of these groups in small spacecraft, launch-vehicle, and ground-
operations technology programs. While the survey of technology was not all inclusive,
due primarily to time constraints, the pane! believes that it developed a comprehensive
understanding of the small spacecraft technology development activities. A summary of
~. ~ - ~
.. .. ~ .. . . .. . . . . . . . . ~ ..
the panel's Endings and recommendations is provided below. In brief, it was apparent
that the DoD agencies, in particular the Naval Research Laboratory, BMDO, and ARPA,
~ ~ ~ ~ i' . i. · '' a,, ~ ~ ~ ~
have llad, in the past, very active programs in small spacecraft technology development.
These programs were supported by industry, both in contractual efforts for the DoD
agencies and with company-funded research and development projects.
Table ~ i-1 is a summary of the technologies that were identified by the pane! as
being currently available, that is, those technologies that could be used by small
spacecraft designers today with minimal risk, but with the unclerstancling that some
degree of further development and flight qualification may be required. The availability
was based on the experienced judgment of the pane! members. Table ~ I-! includes, in
addition to DoD and industry technologies, those technologies developed in the NASA
technology program, primarily at GSFC, JPL, and LeRC. Many of these technologies
currently are being used in ongoing programs such as in the Clementine spacecraft, in
the Small Explorer program, and in the Lockheed commercial spacecraft being developed
for the TRlDIUMT24/SM program.
87
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88
Technology for Small Spacecraft
TABLE Il-l Currently Available Technologies for Small Spacecraft within NASA, Other
Government Agencies, and industry
TECHNOLOGY
AREA
TECHNOLOGY
LOCATION*
SYSTEMS
ENGrNEERING AND
OPERATIONS
PROPULSION
POWER
MATERIALS AND
STRUCTURES
COMMUNICATIONS
Phase-change memory materials to replace
explosive devices on the spacecraft
Autonomous, on-board health monitoring of
launch vehicle and spacecraft
Autonomous determination of orbit
parameters and autonomous station keeping
Bipropellant thruster (756 newtons) with
high response valving and low weight (64
grams)
Monopropellant thruster (223 500
newtons) with high pulse rate, low weight
(184 326 grams)
Carbon composites and fiber overwraps on
aluminum propulsion tanks for reduced
weight
Arc jets for station keeping (less than 1-
kilowatt power levels)
SPT-70 electromagnetic Hall thruster
Silicon, Gallium Arsenide, and Gallium
Arsenide/Germanium solar arrays
U.S. Air Force Phillips Laboratory,
Industry, Naval Research Laboratory
U.S. Air Force, NASA, Industry, U.S.
Army
BMDO, JPL
BMDO, U.S. Air Force Phillips
Laboratory, Industry
BMDO, U.S. Air Force Phillips
Laboratory, Industry
BMDO, U.S. Air Force Phillips
Laboratory, Industry
NASA, U.S. Air Force Phillips
Laboratory
BMDO, JPL, U.S. Air Force Phillips
Laboratory, Industry
NASA, BMDO, DoD, Industry
Radioisotope thermoelectric generators DOE, NASA
Individual and common pressure vessel
nickel hydrogen batteries
Smart structures for jitter suppression
Aluminum-lithium alloys for primary
structures
Naval Research Laboratory
U.S. Air Force Phillips Laboratory
NASA, Industry
Polymer matrix composites for primary Industry
structures
High speed switching from the Advanced
Communications Technology Satellite (Ka
band)
Radio frequency satellite link components
Radio frequency phased array antennas
Solid-state amplifiers
NASA, Industry
NASA, Industry
NASA, Industry
NASA, Industry
.
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Overall Findings and Recommendations
89
TABLE 11-l Currently Available Technologies for Small Spacecraft within NASA, Other
Government Agencies, and Industry (Continued)
TECHNOLOGY
AREA
TECHNOLOGY
LOCATION*
GUIDANCE AND
CONTROL
SENSORS
LAUNCH VEHICLES
Ring laser gyroscopes
Focal-plane-array star trackers
Small, lightweight reaction wheels using Industry
conventional bearings
GPS receivers for position determination
Solid-state recorders, radiation hardened
32-bit computers, radiation hardened
Standard electro-optical bus (e.g., Military
Standard 1773)
BMDO-developed instruments using passive
and/or active sensors: star trackers, near
infrared camera, long-wavelength infrared
camera, ultraviolet/visible infrared camera,
laser imaging and detection ranger
Industry
BMDO, Industry
Industry, Naval Research Laboratory
Industry
Industry
U.S. Air Force Phillips Laboratory,
Industry, NASA
BMDO
NASA-developed instruments for the NASA
Mission to Planet Earth program
Aluminum-lithium alloys for propellant
tanks and other structures
Graphite epoxy for propellant tanks and Industry
other structures
NASA, Industry
* The location indicated is intended to be representative and may not include all sources.
in addition, since the pane] was tasked to survey small spacecraft technology in NASA,
industry, and other government agencies, work at universities was not thoroughly
assessed by the panel.
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go
Technology for Small Spacecraft
TABLE 1 1-2 Technologies Under Development within NASA, Other Government Agencies, and
Industry
TECHNOLOGY
AREA
TECHNOLOGY
LOCATION*
SYSTEMS Capability to use factory-to-launch sequencing BMDO, JPL
ENGINEERING AND
OPERATIONS Processors that enable significant on-board NASA, JPL
data processing to relieve ground data
processing requirements
Automated preparation of flight software
Industry, BMDO, JPL
PROPULSION XLR-132, advanced bipropellant orbit transfer U.S. Air Force Phillips Laboratory,
engine Industry
Iridium-rhenium thrusters, 445 newtons
Piston-pump propellant supply systems
Weight reduction and miniaturization of
propulsion system components
Carbon composites for thrust-chamber
structure and high-pressure propellant tangs
Xenon ion thrusters, 1-5 kilowatts
Solar thermal propulsion
POWER
LeRC, Industry
Lawrence Livermore Laboratory,
Industry
U.S. Air Force Phillips Laboratory,
NASA, Industry
BMDO, U.S. Air Force Phillips
Laboratory, Industry
NASA, JPL, Industry
Amorphous silicon, copper indium diselenide,
cadmium telluride, indium phosphide on
germanium, and multibandgap cells
Thin-film cells
Ultra-light flexible panels and flexible arrays
Nickel metal hydride batteries
Lithium batteries
Advanced energy conversion systems (Stirling,
thermophotovoltaic, and alkali metal
thermoelectric converters)
U.S. Air Force Phillips Laboratory,
Industry
LeRC, U.S. Air Force, Industry
BMDO, U.S. Air Force, JPL,
Industry
LeRC
LeRC, JPL
JPL, LeRC, DOE, BMDO, U.S. Air
Force
NASA, DOE, Industry
MATERIALS AND Inflatable structures Lawrence Livermore National
STRUCTURES Laboratory, Industry, U.S. Air Force
Phillips Laboratory
Smart structures for vibration and jitter control
Embedded sensors
U.S. Air Force Phillips Laboratory
U.S. Air Force Phillips Laboratory
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Overall Findings and Recommendations
TABLE Il-2 Technologies Under Development within NASA, Other Government
Agencies, and Industry (Continued)
91
TECHNOLOGY
AREA
TECHNOLOGY
LOCATION*
MATERIALS AND
STRUCTURES
(continued)
COMMUNICATIONS
GUIDANCE AND
CONE ROL
SENSORS
Advanced composite materials and
manufacturing methods
Metal-matrix composites for structures
Electro-emissive panels
Transponders
Superconducting communications components
Optical communications
Radio frequency space-to-space links and
associated components and antenna systems
New multiple-access schemes
Interferometric fiber-optic gyroscopes
Advanced, miniaturized small reaction wheel
GPS for three-axis control of spacecraft
Radiation-hardened, fault-tolerant electronics
Advanced electronics packaging techniques
GPS receivers for attitude determination
Advanced inertial measurement unit based on
emerging technologies
Technologies being developed for Mission to NASA
Planet Earth (see Appendix F)
Technology being developed for BMDO
programs
Indium antimonide detectors for midwave
infrared sensors
Arsenic-doped silicon for long-wave infrared
sensors
Multispectral imager
Superconducting materials
Solar-blind ultraviolet detectors
Analog processor
Industry
Industry, NASA, U.S. Air Force
Industry
Industry, NASA
Industry
NASA/GSEC, JPL, U.S. Air Force,
BMDO, U.S. Navy, Industry
U.S. Air Force Phillips Laboratory
Industry
JPL, DOE, Industry
Industry
NASA, Naval Research Laboratory
Industry, NASA
Industry, Naval Research Laboratory
Industry, NASA, Universities
Industry, Universities
BMDO, Industry, Lawrence
Livermore National Laboratory
BMDO, Industry
BMDO, Industry
ARPA
ARPA, Industry
Applied Physics Laboratory, Naval
Research Laboratory
Applied Physics Laboratory
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92
Technology for Small Spacecraft
TABLE ~ I-2 Technologies Under Development within NASA, Other Government
Agencies, and Industry (Continued)
TECHNOLOGY
AREA
TECHNOLOGY
LOCATION*
SENSORS Laser radar Industry, BMDO
(continued)
ROBOTICS Remotely programmed microrovers JPL
Tools for autonomous operation of NASA, ARPA, Industry
mlcrorovers
Spaceborne geophysical sampling device
LAUNCH VEHICLES Advanced composite materials for fabrication Industry
of intertank structure, skirts, and payload
shrouds
Lower-cost solid- and liquid-rocket motor
components through use of advanced
manufacturing methods
Hybrid propellant motors and stages
Reusable cryogenic and tripropellant
propulsion components (injectors, thrust
chambers, pumps) for application to single
stage-to-orbit
Clean propellants using higher-performance
ingredients such as ammonium dinitramide
Clean solid propellants exploiting ammonium
nitrate, solution propellant, and scavenged
approaches
NASA, Applied Physics Laboratory
U.S. Air Force Phillips Laboratory,
Industry
Industry, NASA, U.S. Air Force
U.S. Air Force Phillips Laboratory,
NASA, Industry
U.S. Air Force Phillips Laboratory,
Industry, U.S. Navy
Industry, U.S. Air Force Phillips
Laboratory
* The location indicated is intended to be representative and may not include all sources. In
addition, since the pane! was tasked to survey small spacecraft technology in NASA, industry,
ant! other government agencies, work at universities was not thoroughly assessed by the panel.
it should be noted that some technologies listed as being currently available in Table ~ I-!
may also appear in Table ~ I-2 as technology under development. The available technologies in
Table ~ I-} currently possess a specific level of capability that can be useful for small spacecraft,
but the technology may also be uncler development to expand! its mission capability or to
complete the flight qualification. Recommendations for future work on many of the technology
areas noted in Table Il-! ant} Table il-2 are presented in the last section of this chapter.
Based on its review, the Pane! on Small Spacecraft Technology believes that the
technologies noted in Table 11-] can be used, with an acceptable risk level, in
current NASA development programs for small spacecraft.
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Overall Firulings and Recommendations
· . . ~
Technologies currently under development in government and in industry are
shown in Table .:~-2. Table Il-2 was intended to serve two purposes: (~) to identify
ongoing technology programs that, if continued, are likely to result in available
technology that could be applied to future small spacecraft programs, and (2) to identify
ongoing developments in industry and government agencies to assist NASA in avoiding
duplication in their small spacecraft technology development program.
The Pane! on Small Spacecraft Technology recommends that NASA
monitor the progress being made in the technology programs listed in
Table 11-2 arm that the programs be evaluated to avoid possible
duplication. It is further recommended that, in the event that the
sponsoring agency is other than NASA, aM decides to discontinue the
development activity, NASA should consider completing the technology
development.
-
·
Again, tne panel does not intend the technology lists in Tables ~ i-! ant! ~ :~-2 to
be all inclusive. The tables do, however, reflect the results of the panel's fairly extensive
review.
Technology Gaps and Overlaps
The panel's review ctici not identify any overlaps of NASA's research and
development with that of DoD and industry that were considered to be serious. On the
contrary, the panel believes that the level of technology development underway in the
United States is deficient, considering the NASA objective of widely expancled use of
small spacecraft.
Although gaps in technology are difficult to (lefine, the panel believes that there
is a significant gap between the technology that is now available and that which is being
used in the NASA small spacecraft programs. This may be a result of the conservatism
of the NASA project managers, which is understandable because of the dire consequences
of failure engendered by the current, very costly large space programs. In acictition, the
pane! believes that there are gaps relating to the technology needed to achieve the
maximum return from small spacecraft in the future. These gaps are addressed in the
recommendations for technology development in the following section.
Prioritized Areas in Which Greater Investments are Likely to Have High Payoff
Considering Current and Projected Budgets, the NASA Mission Statement, and
the Needs of Industries That Utilize Space
As stated in Chapter i, the principal deterrent to an expanded space program,
both in NASA and commercially, is high cost. This is true for NASA because of today's
budgetary and political climate and for industry because of the high cost in providing a
93
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94
Technology for Small Spacecraft
potential service to a buyer, along with increasing international competition. If
technology can be developed that will enable small spacecraft to achieve increasingly
capable missions while maintaining the ability to produce the spacecraft at reasonable
cost, the utilization of space by both NASA and industry could expand.
The pane! believes that there are numerous opportunities in the development of
technology related to small spacecraft systems. The difficulty is in how to prioritize and
invest in technologies to achieve the greatest reduction in cost. In this section, the pane!
has assigned priority levels to the technology recommendations contained in the body of
the report. Three priority levels were chosen: high, higher, and highest. The pane!
applied criteria (not in priority order) that included the following:
the potential to reduce mission cost;
the cost to develop the technology;
the potential to reduce weight (permitting a higher payload mass fraction
or use of a smaller launch vehicle);
the likelihood of a successful development; and
the potential to enable key mission goals.
Since hard data regarding these criteria are not available, the qualitative judgment
of the pane! members, based upon their experience and background, was the determining
factor. In order to balance differences in judgments, the priority selections were made
independently by two separate groups of pane} members, and then a consensus was
reached by the entire panel.
The recommendations, in general, address applied research programs rather than
generic research activities. As discussed earlier, generic research also is an essential part
of a total technology program. Such programs not only continue to extend the state of
the art but also provide an opportunity for NASA to attract talented} college graduates to
work in NASA's laboratories and to engage universities, graduate students, and industry
in stimulating research and development activity under contract to NASA.
In addition, since many of the technologies that can be used on small spacecraft
have been developed by DoD and industry, the pane! believes that:
A normal part of NASA 's research and development activity should includle
the continual monitoring by NASA of research arm development activities
of other government agencies, foreign governments and organizations. and!
industry.
~- ,
The pane! believes that each recommendation is worthy of implementation.
However, recognizing the uncertainty of NASA funding for technology development, the
pane! has identified those areas as highest priority, which in its judgement, offer the
greatest potential for enhancing the mission capability and reducing the cost of small
spacecraft. The remaining areas were identified as either high or higher priority. The
assumption is that all of the recommended areas will be pursued at some point, with
those in the highest priority level being funded first. The fact that the development of a
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Overall Findings and Recommendations
particular technology may not come to fruition for several years should not bias a
decision regarding early funding.
The pane} believes that advanced technology has the potential to greatly enhance
the ability of small spacecraft to perform meaningful missions at Tow cost. It is the
opinion of the pane! that the totality of the recommendations, if executed, would enable
an important part of the United States' space-science program to be accomplished very
economically with small spacecraft. It would also provide a very strong technolo~v base
for the emerging small spacecraft commercial industry.
, ~i,
The technology recommendations were assigned priority levels as discussed above
and are listed at the end of this chapter. Discussions of the specific technologies can be
found in the appropriate sections of the body of the report. Some technologies that have
a particularly high potential to make a large impact on the cost and capability of small
spacecraft are
.
technologies to reduce cost ant! improve efficiency of up-front systems
engineering, launch, and mission operations;
GPS for precision guidance and control;
high-efficiency solar electric power generation and electric propulsion;
hybrid propulsion for launch vehicles; and
miniaturization of electronic devices.
Many launch and mission operations functions that now are performed by ground
personnel can be automated with lightweight, low-cost, on-board systems. For example,
on-board vehicle monitoring and, in some cases, defect correction can be automated,
enabling factory-to-launch operations without the requirement for extensive intermediate
ground testing. On-board launch trajectory monitoring for range safety purposes is
achievable using GPS on board the spacecraft, eliminating the need for ground-based
radar tracking during launch. Automated, on-board orbit determination and station
keeping is also possible using GPS, which simplifies the mission operations task. High-
density computers and memory devices combined with advanced software techniques
enable extensive on-board data processing and screening, reducing the amount of data to
be stored and transmitted to Earth. The compact memory devices reduce the requirement
for numerous data-reception locations on the ground. Communication systems can be
developed that will permit direct delivery of data, partially processed on board, to
researchers in their own laboratories, where they have powerful computing capability at
their desks. Chapter 2 provides more detail on these and other technologies that could
be applied to make substantial reductions in the personnel required to launch and operate
a space mission using a small spacecraft.
Two potential applications of GPS to small spacecraft, as noted above, are launch
trajectory monitoring and automated on-board orbit determination. The pane! believes
that GPS also has great potential in other applications. Use of GPS in various
combinations with other guidance components can determine position and attitude
accurately, probably at significantly reduced weight and cost. GPS also provides the
9s
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Technology for Small Spacecraft
capability to precisely fly clusters of small spacecraft in close proximity to one another,
simulating a much larger spacecraft.
Electric propulsion is a very promising technology that can enable more ambitious
missions in high-altitude orbits and at interplanetary distances. Such missions, however,
must be able to tolerate orbit transfer times of several days or even months. Small,
lightweight spacecraft are particularly suited to this technology because of the relatively
higher thrust-to-weight ratios achievable with these very-low-thrust electric propulsion
systems. In order to gain maximum potential from these high-specific-impuIse systems,
a high electric power level is required. Advanced technology in solar-generated power
could supply the required power levels with array sizes and weights compatible with
small spacecraft. Extensive development work on both the solar power and electric
propulsion technologies has been conducted in the past, but a concentrated, well-funded,
clevelopment activity is needled to bring these technologies to fruition.
Hybrid propulsion is a technology that has great potential for application to small
spacecraft launch vehicles and has been under development for some time. Hybrid
propulsion systems offer unique advantages over conventional solid-propuIsion systems
during manufacturing and shipping because of their inherent inertness and over both solid
and liquid systems during launch operations. The reduction in special safety requirements
should translate into reduced cost. Hybrid propulsion systems have the added advantage
of an environmentally acceptable exhaust product, which conic] be an important factor if
environmental restrictions increase.
Advances in miniaturization of electronic devices have the potential to increase
the payload mass fraction, lower the spacecraft weight, reduce the power requirements,
and reduce overall cost. These devices can be combined to form highly-capable systems
for remote sensing, guidance ant! control, communications, and on-board operations.
Continued investment in advanced design and ground testing techniques for adapting
commercial products for the space environment can assure the availability of up-to-date
technology for space application.
Table ~ I-2 lists those technology development programs currently underway that
were identified by the pane! during its review activity. Before NASA initiates programs
responsive to the recommendations in Table ~ 1-3, it shouIc3 review development
currently underway in other agencies and industry.
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Overall Findings and Recommendations
TABLE ~ i-3 Pnontized Technology Recommendations
97
HIGHEST
Systems Engineering and Operations
-
Capabilities and design tools should be developed that facilitate improved up-front concept development for low-cost
small spacecraft missions. These capabilities and tools should facilitate in-depth trades that result in improving the ability
to estimate and in lowering overall life-cycle costs. Key trades include:
Tools that would be useful are
operational mission concepts;
many small spacecraft versus larger, fully integrated systems;
the degree of autonomy on the spacecraft and on the ground;
the effect of launch strategy and vehicle selection;
the degree of acceptable risk and approach to reliability; and
dedicated versus shared mission operations facilities.
data bases and cost estimating software that address life-cycle cost of small missions; and
· nationally available data bases for existing parts, components, and new technologies.
Technologies and techniques should be developed that would reduce the required number of mission operations
personnel. These techniques include:
autonomous orbit determination and correction;
· on-board data screening to reduce the amount of data to be transmitted to the ground; and
· communication systems for distribution of mission data directly from the spacecraft to the data users.
.
Technologies and practices required to enable a factory-to-launch sequence with minimum checkout at the launch site
should be developed and demonstrated. These should utilize expert systems when appropriate, including, as a minimum,
the following:
on-board health monitoring and checkout and, where economical, fault correction, for both the launch
vehicle and the spacecraft;
techniques for remote system checkout;
automated preparation of flight software for guidance and control of both the launch vehicle and
spacecraft;
a set of standard hardware interfaces for small launch vehicles and spacecraft;
on-board launch trajectory determination for range safety tracking;
spacecraft accessibility late in the countdown; and
reduction of launch pad safety requirements through use of technologies such as hybrid propulsion and
nonexplosive separation devices.
Propulsion
-
An aggressive program should be established to demonstrate, in ground tests, the life of xenon ion propulsion systems
that operate at power levels in the range from about 0.5 kilowatt to about 2.5 kilowatts for lifetimes of up to 8,000
hours. Arc jet thrusters for small spacecraft applications also should be evaluated. The systems demonstrated should be
capable of being integrated into solar electric propulsion systems with total power levels in the range of 1 to 5 kilowatts.
Both the ion thruster and the arc jet should then be demonstrated in space flight tests in the near term.
The propulsion system requirements should be determined for precision station keeping of clusters of small spacecraft,
and the capability of currently available systems should be evaluated. If it is necessary, systems should be developed to
meet specific mission requirements.
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98
Technology for Small Spacecraft
TABLE il-3 Pnontized Technology Recommendations (Continued)
HIGJ~EST (Continued)
Power
An advanced solar array program should be initiated at a funding level that will allow reaching a goal of 200 watts per
kilogram with 5 to 10 kilowatts of total power within the next five years.
The development, characterization, and testing of NiMH batteries for low-power small spacecraft should be completed.
Building on the work already completed for the Clementine mission, the characterization and testing of CPV NiH2
batteries for mid- to high-power small spacecraft should be completed.
Communications
Development of the following technologies should be supported:
an electronically steered Ka-band phased array antenna;
a Ka-band solid-state amplifier; and
a Ka-band power module.
Guidance and Control
A high-priority program to realize the potential of GPS on small spacecraft should be established. The unique
combination of capability and small size made possible by integrating GPS receivers/processors with other existing and
emerging guidance components should be assessed.
The design, documentation, and appropriate qualification of the following components and subsystems should be
completed:
fiber-optic interferometric gyroscope;
miniature focal plane array star tracker;
space-hardened GPS receiver/processor with attitude capability;
advanced, miniaturized small reaction wheel;
hardened 32-bit processor; and
hardened solid-state recorder.
Sensors
The feasibility of achieving the required simultaneity of measurements of different instruments using a cluster of small
spacecraft should be evaluated, and, if feasible, technology should be developed. The employment of GPS and very low-
thrust and high-response attitude control thrusters might enable this technique.
Robotics and Automation
Technology work related to autonomous operations in unstructured environments should be supported and expanded.
Launch Vehicle Technology
Hybrid rocket motors that simulate operational requirements, thrust level, and burn duration for small launch vehicles
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Overall Findings and Recommendations
TABLE 1 1-3 Prioritized Technology Recommendations (Continued)
99
RIGGER
Systems Engineering and Operations
Data storage and transmission techniques should be developed that meet the needs unique to small spacecraft. These
techniques should utilize:
low-cost, miniaturized, high-capacity, reliable data storage devices;
efficient, high-data-rate transmission techniques;
better forward error-correction codes; and
efficient protocols for high-speed-data interactive transactions.
Standardized communications interfaces for mission control functions should be developed. Areas for standardization
include:
tracking and orbit data formats;
telecommunications characteristics;
standard-format data units;
time-code formats;
packetized telecommands;
packetized telemetry; and
telemetry channel coding.
Propulsion
A technology program should be established to demonstrate the Light Exo-Atmospheric Projectile propulsion technologies
at mission duty cycles and lifetimes consistent with small spacecraft mission life and operational requirements.
The 445-newton rhenium-iridium thruster should be evaluated for application to an apogee kick stage for small
spacecraft. This includes demonstration over a duty cycle typical of the missions envisioned for small spacecraft.
The suitability of the XLR-132 engine as an upper-stage propulsion system for launching small spacecraft with deep-
space propulsion needs should be evaluated.
Power
The development of lithium alloy (LiTiS2) batteries, particularly for low-energy-demand planetary missions, should be
continued.
The application of lithium ion batteries developed by the DOE should be evaluated for possible use in low-Earth-orbit
spacecraft. If found promising, the technology should be adapted for small spacecraft.
For mid- to far-tenn applications, the development of lithium polymer batteries should be accelerated.
In the long-term, work on other advanced solar cell and solar array technology, including thin-film cell development,
inflatable arrays, and flexible blanket wing APSA arrays, should continue at an increased funding level, with the goal of
achieving a specific power of 300 watts per kilogram.
Structures and Materials
Research on simple, low-cost deployable booms and surfaces should be emphasized. The objectives should include high
deployment reliability, compact stowage, and adequate precision. Ground-test proof of successful deployment in space is
essential.
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100
TABLE 1 1-3 Pnontized Technology Recommendations (Continued)
Technology for Small Spacecraft
HIGHER (Continued)
Structures and Materials (continued)
A joint NASA-industry program should be initiated to demonstrate developments of advanced small-spacecraft designs
that are based on polymer-composite components, exploiting available as well as novel technology as appropriate to meet
the paramount demands of low cost, low weight, reliability, and adaptability. The NASA Small Spacecraft Technology
Initiative may fulfill this objective.
In coordination with ongoing research at universities and other government agencies, research efforts should be
intensified in the area of smart structures and control-structures interaction. Research should be generic in character as
well as focused on specific needs for small spacecraft.
Communications
Optical frequency (laser) communications systems and components (e.g., electronically controlled antennas and signal
processing) should be developed for space-to-space links.
Radio frequency space-to-space links, the associated components, and spacecraft antenna systems for complex spacecraft
constellations in both low Earth orbit or other orbits should be developed.
New, multiple access schemes and the associated critical components should be developed, as well as optimization of
bandwidth utilization in the mobile satellite frequencies for low-Earth-orbit systems.
Guidance and Control
Design and ground-testing techniques should be developed that ensure acceptable performance in the space radiation
environment. Additional support should be provided for the work in this field. The payoff in reduced flight-test time and
funding will more than compensate for the investment in this effort. Further, the added assurance will encourage project
managers to use more current technology. These techniques could be applicable to a broad range of electronic
components and systems.
Sensors
.
A research and development program should be directed toward the development of miniaturized, power-efficient, high
performance instruments in the following areas:
multifrequency radar altimeter and scatterometer systems;
advanced coherent lidar systems;
multispectral Earth observation systems operating in the ultraviolet, visible, and infrared wavelengths,
employing lightweight optics and advanced detector array technology;
advanced, passive, larger-aperture, high-sensitivity, low-weight, microwave radiometry employing
lightweight deployable antennas, room-temperature superconducting sensors, and advanced on-board
processors; and
lightweight, deployable-mirror optical systems with deformable mirrors correctable to the diffraction
limit, for ultraviolet, infrared, and visible long baseline interferometry using several small spacecraft,
ultimately resulting in an extremely large-aperture phased array for astronomical observations.
_
Robotics and Automation
Autonomous systems and artificial intelligence should be developed for application to microrovers.
.
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Overall Findings and Recommendations
TABLE ~ i-3 Prioritized Technology Recommenclations (Continue(l)
Boa
HIGHER (Continued)
Launch Vehicle Technology
Although the Panel on Small Spacecraft Technology believes it has identified several areas with potential for reducing
small spacecraft launch vehicle costs, the panel was not able to identify a technology program that would achieve the
desired cost of $5 million to $7 million per launch. The panel, therefore, recommends that NASA conduct a study of
proposed, new launch vehicles targeted for the small payload market; with a goal of $5 million to $7 million per launch;
to determine the cost benefits associated with the introduction of new technology, including unique concepts, new
hardware designs, new materials, and manufacturing methods. This study should also include consideration of support for
launch and mission operations. NASA should initiate advanced demonstration programs for promising concepts identified
in the study, especially in propulsion technology. These demonstrations should be carried to the point that will allow
decisions for system development to be made by either the government or commercial ventures.
HIGH
Propulsion
Research and technology programs should be initiated to demonstrate fully the capability of solar thermal rockets, with
emphasis on concentrator/mirror, absorber-thruster, and feed-system technology. Space flight tests should be conducted
to explore deployment mechanisms and dynamics, validate packaging techniques, and demonstrate the performance and
durability of absorber-thruster operation with a deployable concentrator mirror.
Power
There is a small but important subset of small spacecraft missions that cannot use solar power or batteries and that are
enabled by radioisotope power systems. For those missions, development of more efficient conversion systems to reduce
heat source mass and cost would be beneficial. Radioisotope power system designs using Stirling, thermophotovoltaic,
and alkali metal thermal-to-electric converter conversion techniques should be jointly evaluated by NASA and DOE, and
the ability of these techniques to satisfy various NASA missions should be assessed. Based on the evaluation, NASA and
DOE should select one or more of these systems for experimental demonstrations of its performance against specific
pre-determined criteria that are peculiar to the approach selected. NASA and DOE should then select the most promising
approach for further development. A decision about flight demonstrations should be made contingent on future NASA
planning of missions that would utilize the technology.
Research on concentrator arrays, with a goal of reaching power densities in excess of 300 watts per kilogram at one-half
the cost of existing arrays, should be increased.
Structures and Materials
A short-term demonstration program with industry should be undertaken to design, construct, and qualify a small
spacecraft structure based primarily on current structural design configurations that exploit aluminum-lithium alloys in
lieu of aluminum in order to determine the feasibility of rapid weight savings with minimal effort and cost.
Sufficient expertise in polymer-matrix composite technology should be maintained within NASA to identify and pursue
opportunities for research aimed at improving strength, stiffness, thermal properties, and economy of fabrication, with
explicit attention to the possibilities of multiple-use components and the engineering of modular attachments and joints.
Communications
NASA should be the technical leader in developing the rationale for radio frequency reassignments in view of the new
optical communications developments.
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102
TABLE 1 1-3 Pnontized Technology Recommendations (Continued)
HIGH (Continued)
Technology for Small Spacecraft
Guidance and Control
The advantages and disadvantages of applying standardization to specific interfaces for electronic and electro-optical
components and subsystems (e.g., Military Standards 1553 and 1773) to simplify integration activities should be
evaluated, and standardization should be implemented as indicated by the evaluation.
Sensors
A continuous research and development program should be conducted to improve the performance and reduce the weight
and power required for infrared detector arrays; cryogenic detector coolers; and deployable antennas for radiometry and
radar.
Robotics and Automation
.
A research and development program focused on miniaturizing robotic devices, science instruments, and associated
computing power should be developed.
Robotic spacecraft systems incorporating the most advanced autonomous systems and artificial intelligence technology
currently available should be developed for demonstration in space on small spacecraft and on the Space Shuttle. The
technology should be applied to the development of a free-flying robotic spacecraft for inspection, maintenance, and
research support on the Space Station.
Launch Vehicles
The ongoing Solid Propellant Integrity Program should be supported with increased consideration toward those solid
propulsion units used in commercial small launch vehicles. Such action will help the commercial sector maintain or
improve reliability.
Development of advanced manufacturing methods directed toward producibility and cost reduction of small spacecraft
launch vehicles should be continued. This should include potential application of advanced composites.
Scavenged and solution propellants are possible near-term solutions to potential environmental limitations of propellants
and should be scaled-up and qualified for use.
A program to characterize the ammonium dinitramide-based clean propellants should be funded. If the results are
positive, a program to develop a pilot plant to scale-up the manufacture of ammonium dinitramide should be funded.
NASA should initiate technology efforts in support of a reusable single-stage-to-orbit vehicle for small spacecraft where
appropriate, to ensure the availability of the enabling technologies on a realistic time scale.
Representative terms from entire chapter:
launch vehicles
