3. TECHNOLOGY DESCRIPTION

3.1 Space Vehicles

3.1.1 Warfighter Needs

Space Vehicle technology goals translate into payoffs to the warfighter in terms of increased warfighter capabilities. Payoffs to satellite systems include higher performance, lower cost, longer life, and increased reliability for existing and new satellite families. This technology area also provides solutions to numerous AFSPC deficiencies. Examples of deficiencies include: inadequate near Earth coverage; high O&M costs; inadequate satellite element set accuracy; inadequate terminal mobility; insufficient communications capacity; accuracy of data; vulnerability of ground facilities; and slow deployment of space assets. Advanced space sensor, precision orbital structures, and cryogenic technologies will help provide all weather, day/night operation, and detection of airborne targets down to cruise missile size. GPS technology advances allow for improved targeting of Earth-based objects and precision strikes. Sensor, precision orbital structures, and cryogenic technologies are applicable to SBIRS, SMTS, NPOESS, space based JSTARS and AWACS alternatives and NASA EOS. Space power transition targets include NPOESS, GPS IIF, SBIRS, MILSTAR, space based JSTARS and AWACS alternatives, FLEETSATCOM, and SMTS. Communications transition targets are MILSATCOM (e.g., FLEETSATCOM and MILSTAR), as well as any mission requiring high data rate transmission. The USAF has taken steps to transition to a common core Telemetry, Tracking, and Control (TT&C) in the next few years which will support multiple satellite families. Satellite control technology is directed on evolving the Core to support existing and future warfighter needs and migrating autonomy for satellite control from the ground segment to the space segment. GN&C technology supports precision navigation and autonomy for the satellite relieving large O&M costs, as well as performing the guidance portion for global delivery of precision conventional warheads. Survivability technology advances include advanced hardening techniques, development of radiation and other environmental effects models, and a satisfactory method to allow COTS devices to operate properly in space. These will permit any space system to be produced at lower costs and to function longer and more reliably. In addition to the listed systems, advanced electronics technologies enable future space systems that are envisioned to support the warfighter into the 21st century.

3.1.2 Space Vehicles Overview

3.1.2.1 Goals and Timeframes

• Thermal Management: minimizing material stresses, mass, internal parasitics, and increasing the motor and cold interface heat transfer efficiencies; eliminating sources of contamination and friction; developing improved adaptive and passive structural damping; develop novel approaches to reduce cryocooler vibrations; the development of rapid, reliable start-up and long term operation capability of two phase capillary devices in zero-g and adverse-g environments; developing advanced materials to dissipate heat fluxes from microelectronic devices and capillary wicks with less than 1 micron pore size; and improving flexible or rotatable joints for deployable radiators.

• Structures: structural isolation without constraints on rattle space (clearance); understanding dynamics arising from interactions between the space environment, structural materials, individual components, control systems, the launch vehicle, and spacecraft; cost effective manufacturing techniques; development of rapid non-pyrotechnic release mechanisms and high fidelity, ground-based experimental simulations; increased reliability/durability of Multi-Functional Structure connections; and deployable, large lightweight structures.

• Survivability: develop radiation tolerant space devices and systems; reduce space-use COTS safety factor with improved understanding of basic radiation effects phenomena; improve reliable high precision survivability simulations; develop miniaturized laser and radar threat detectors, optical systems jamming protection; characterize space debris hazards.

• GN&C: mitigate or reduce radiation exposure and plasma effects; eliminate Ring Laser Gyro (RLG) mechanical dithering; improve RLG mirror durability; improve light sources, coil selection, and windings for interferometric fiber optic gyros (IFOGs); improve micromachining processes; laser tracking; obtaining accurate ephemeris data; and the hardware/software interface for autonomous navigation.

• Power: increased compatibility and applicability of advanced materials in the space environment; more efficient photovoltaics; viability of manufacturing; feasibility of solar thermal conversion; limits on high temperature power conversion; highly reactive chemicals; runaway electrochemical reactions; and life limiters in energy storage (e.g., electrode wear).

• Space Electronics: increasing space radiation hardness of recently available small feature size, high performance electronics technologies; advanced packaging to dissipate heat in a vacuum without out-gassing; advanced insulated device technologies; and integrated MEMs.
• Space Sensors: increase the operating temperature of sensors; improve manufacturability of large size focal plane arrays; and significant reduction of sensor readout noise.

• Satellite Communications: develop high capacity dynamic optical communications system area networks; develop a small, adaptable (to numerous wavefronts) and efficient modem; and improved ability to manufacture ultra light-weight, higher frequency antenna and GaAs PHEMT MMICs, and low power high speed CHFET (Complementary Heterojunction Field Effect Transistor) custom integrated circuits.

• Satellite Control: overcome vendor-specific dependencies in COTS software; exploiting distributed artificial intelligence capabilities; develop integration of an intelligent trainer with a multi-satellite ground system; use of model-based reasoning and machine learning for anomaly resolution; reducing development and sustainment costs when DoD does not drive the market; and reliable, verifiable artificial intelligence-based systems for autonomous satellites.

3.1.2.3 Related Federal and Private Sector Efforts. Outside of the DoD, the primary government organizations funding Space Vehicles technology development are NASA and DOE. National systems also make a huge investment in space vehicles technology. Formal coordination with NASA, DOE, DOC and DOT is provided through the Space Technology Interdependency Group (STIG). Historically, the NASA investment matches that of the DoD in many of the technologies, while the DOE investment is considerably smaller. Joint program planning and management of technology development (e.g., NASA/DoD IPT) is coordinated among these organizations and the user community to ensure maximum return on government investment of research and development funding. The related NASA programs of greatest relevance are the New Millennium Program and the Small Satellite Technology Initiative. Various pervasive technologies, such as space power, thermal management, and structures are closely coordinated with the responsible NASA technology centers. Industry is estimated to be investing $220 million of their IR&D funds in related space technology. This work is typically focused on developing a competitive capability for near and far term corporate goals. Additionally, there are focused commercial ventures for space-based systems, such as communication and imaging satellites, that complement these efforts. The recent appearance of a strong well-capitalized commercial presence in space allows DoD to leverage advances in these systems. Commercial space manufacturers' private capital, short development cycle, and frequent new starts permit a new arena for rapid maturation of space platform technology. The DoD has formed CRDAs (Cooperative Research and Development Agreements) with the commercial sector to provide opportunities for space demonstration of the technology and to jointly share in the cost of development in some areas, such as energy storage. Industry has plans for both highly autonomous spacecraft and architectures for large, distributed networks of satellites. Similar advances are occurring in the international arena as well.

3.1.3 S&T Investment Strategy

3.1.3.1 Technology Demonstrations. The Space Vehicles technology demonstration program is based on three major demonstration concepts as well as individual component and subsystem technology demonstrations in support of the DTOs for this subarea.

The first effort is the USAF Integrated Space Technology Demonstration (ISTD) program, which will demonstrate medium risk, high payoff system and payload concepts through the design, integration, test and evaluation of emerging technologies in real world environments. The focus is the demonstration of advanced technologies with maximum payoff to military space systems operators and users. Major elements of ISTD include the transition of new technologies from the laboratory to integrated systems, the employment of leveraged flight opportunities to address both technology and system level issues as economically as possible, and demonstration of laboratory technologies in support of specific military space objectives. Flights will occur every three to five years. Specific current objectives include: demonstration of the military value of near real time tactical imagery derived from commercial and civil providers; the design, development, and demonstration of an affordable space-based hyperspectral imaging payload for tactical target detection; and development of innovative ways to support future tactical imaging payloads on a wide range of commercial space platforms. Success will provide a >= 50% reduction in the time required to field a new imaging system, from more than 7 years to 3 1/2 years; an overall reduction in the time (from days to only a few hours) required to bring tactical imagery to the tactical users; and a potential 50% reduction in optical system payload weight (from 500 kg to 200-300 kg), which will in turn reduce launch costs. The first ISTD flight will demonstrate targeted FY00 goals within the following DTOs: Cryogenic Technologies (SP01), Space Structures and Control (SP03), Space Electronics (SE26), Space Sensors (SE22), and Satellite Communications (IS23). These goals include reduced cryocooler mass, reduce structured mass and advanced comm modems. These programs directly support the Air Force Space Command, including the Space Warfare Center, and military users of tactical space imagery.

The second part of the demonstration program is the USAF MightySat. This program is a fast-paced, aggressive series of space experiments and demonstrations that focus on experimenting with and demonstrating a small number of new, emerging Air Force technologies on each flight. Each MightySat mission focuses on three objectives: demonstrating emerging technologies, measuring the technologies' suitability, determining the reliability, and removing or reducing the risk of using new technologies for space acquisition. The MightySat approach of providing annual, low-cost access to space ensures the ability for emerging, space-ready technologies to acquire space heritage. Each MightySat mission will take about 24 months from conception to launch and provides for one year of on-orbit mission operations. The first MightySat is schedule to launch on the Space Shuttle in December 1996. This flight supports the following DTOs: Advanced Structural Components (SP03), Space Power Technology (SP08), and Space Electronics (SE26). The second MightySat is schedule for launch in Jan 98, with schedule launches every year thereafter. MightySat-2 supports Advanced Structural Components (SP03), Guidance, Navigation, and Control (SP07), and Space Sensors (SE22). MightySat-3 supports Space Systems Survivability (SP06). MightySat-4 supports Advanced Structural Components (SP03) and Guidance, Navigation, and Control (SP07). MightySat-5 supports Advanced Structural Components (SP03) and Space Electronics (SE26). Specific goals that will be demonstrated include: reduce structural mass by 40%, decrease on orbit vibrations by a factor of 10, autonomous satellite navigation capable of >50m positioning uncertainly 28% efficient solar cells. 120 whrl kg rechargeable battery and reduce electronics weight by a factor of 10.

Part three is the USAF Integrated Ground Demonstration Program. This demonstrates high risk / high payoff system and payload level concepts via the ground integration of emerging technologies. This is accomplished by characterizing technology interfaces and interactions in a simulated operational environment. This technology integration capability provides the ability to evaluate advanced payload, system, and mission concepts. A specific current objective, which supports Large Precise Structures (SP05), is to demonstrate (by FY98) the feasibility of a 50% reduction in large aperture imaging system weight. Such a capability will enable the deployment of large aperture telescopes (>2.5 meters), and enable long-dwell imaging from geosynchronous orbit. This program directly supports Air Force Space Command, Air Force Space Warfare Center, and Air Force Special Projects.

The fourth part of the demonstration program is component and subsystem technology demonstration. This program encompasses the many small flight experiments often placed in orbit through the DoD Space Test Program. The DoD Space Test Program (STP) is managed by the Space and Missile Test and Evaluation Directorate (SMC/TE); PMD guidance for STP calls for one small launch vehicle flight (Pegasus-class with satellite of less than 1000 pounds) every two years and one medium launch vehicle flight (Delta-class with satellite of 6000 to 10,000 pounds; note that ARGOS weighs roughly 6000 pounds) every four years. Experiments are selected through the Space Experiments Review Board (SERB) which meets annually to consolidate and prioritize space experiments proposed from all of the Services; experiments are ranked primarily by military relevance. STP funding is used to support experiments which don't have their own means of access to space; STP support can include providing the spacecraft bus, integrating the experiment payload, launch services, and one-year's on-orbit operations. STP also sponsors approximately 20 experiments/year on Space Shuttle flights and another two to four experiments/year on other host satellites. While these smaller experiments do not individually have significant funding or visibility, collectively they are the backbone of space vehicle S&T. An example of these small experiments is the Navy's Microelectronics and Photonics Test Bed currently in final assembly of flight hardware for launch during FY97. The objectives of the MPTB project are: (1) selection by SPOs of devices and subsystems for test; (2) perform ground-based radiation tests; (3) predict space results; (4) analyze space data and develop new radiation effects models. The MPTB experiment will space qualify devices and subsystems and demonstrate that COTS devices can operate in selected orbits. Another program is the Missile Technology Demonstration Flight. It will demonstrate Range Safety & Instrumentation to augment the use of range radar for safety and range metrics. Other examples which are currently manifested (and the flights they are on) are: Electromagnetic Propagation Experiment (STEP 4); Compact Environment Anomaly Sensor (TSX-5); Beryllium-7 Induced Radiation Experiment (Cosmos); and Polar Orbiting Geomagnetic Survey II (DMSP
S-15).

3.1.3.2 Technology Development. The Space Vehicles Subarea consists of six technology efforts: Thermal Management, Structures, Survivability, GN&C, Space Power, and Astronics. Technology advances in all of these efforts are required to achieve the overall goals of this subarea. The technology efforts and their respective activities are:

• The Thermal Management effort encompasses the development of cryogenic and conventional spacecraft bus thermal management technologies required for temperatures ranging from 10° to 900° K. Technology development includes: cryocoolers that satisfy a wide variety of missions; advanced thermal integration components; very high heat transfer, capillary wicking devices; ambient temperature thermal energy storage; passive and active thermal control devices for cooling of advanced microelectronic devices; and development of deployable radiators and coatings.
• The Structures effort is being conducted to discover new ways of making lightweight, low cost, and precise structures for launch vehicles and satellites and to develop new methods to prevent vibration and structural dynamics from degrading the performance of future DoD launch vehicles and satellites. The increasing DoD need to reduce launch cost has led to a significant investment increase in launch vehicle structural component and structural control technology. Programs are exploring active control, passive damping techniques, precision deployable orbital structures, and advanced mechanisms to reduce the structural load which satellites must survive during launch. Other efforts address technology for satellites and include: concepts for lighter weight, lower cost, higher performance solar array, radiator, antenna and electronic enclosure structures; Multi-Functional Structures; and smart mechanisms for deploying and moving solar arrays and other deployable structures.

• The Survivability effort includes advanced hardening techniques, models of device response to space radiation, and methods to allow COTS devices to operate properly in the lower dose space radiation orbits.

• The GN&C effort encompasses autonomous navigation GPS technology, star trackers, and navigation instruments with the primary objective being to increase navigation and attitude determination accuracy while reducing size, power, and mass and increasing reliability.

• The Space Power effort covers the development of all required components for satellite power subsystems including power generation, energy storage, and power management and distribution. Technology development includes non-photovoltaic energy generation, investigating alternate photovoltaic material and cell designs, and increasing the solar concentration ratio of arrays. For energy storage, programs include demonstrating life, performance, and safety of NaS cells while working to develop advanced lithium-based batteries. Investigations into flywheels and other non-electrochemical storage devices have also been started. High voltage solid state relays, hybrid control patches, and integrated power chips are key power management technology approaches for the next five years.

• Sensor technology developments include large space qualified staring arrays in MWIR MCT, LWIR MCT and VLWIR Si:As for near-term applications. QWIP technology and 2-color MCT is under development for mid-term M/L/VLWIR applications. Multicolor QWIP FPAs and photon multiplier devices are in early stages of development to enable future space-based multi- or hyperspectral theater surveillance, and space-based surveillance of cold space objects against dark space backgrounds, respectively. Active sensor technologies development will use an airborne radar test to collect amplitude and phase information on clutter backgrounds representative of those expected for a SBR system to experience on a world-wide, year-round basis. This will be combined with limited data from NASA experiments and other sources to improve the validity of SBR models and simulations. Upcoming studies of non-conventional radar processing against diverse clutter environments, and automatic target recognition tests utilizing small numbers of range-resolution cells, will be leveraged to compare against conventional SBR algorithm performance. Large antenna architectures will be developed and assessed to identify SBR sensor technologies with the highest performance payoffs.

• Space Electronics technology development focuses on increasing throughput and memory capacity; reducing weight, volume, power requirements and the cost of these systems; increasing autonomous operation of space electronics; increasing radiation hardening and survivability; and improving interoperability with other space and ground systems.

• Satellite Communications technology development focuses on GaAs, integrated optoelectronics, and laser devices to enable applications for a variety of areas including RF and optical crosslinks, and optical CDMA system area networks.

• Satellite Control technology development will investigate user friendly graphical data viewing, stored data for the life of the satellite, and extensive on-line data analysis tools; automate data in pass plan manuals, capture expert knowledge in computer based knowledge bases, and utilize model based reasoning and machine learning to resolve anomalies; support reactive, dynamic training integrated into the actual operational system with no human trainer in the loop. Trade studies will be performed to determine which functions are higher payoff for automating on-board from an O&M and satellite survivability perspective. Some on-going work in autonomous orbit control will be flight tested. Other high payoff areas will be developed further and readied for experimental flight testing.

3.1.3.3 Basic Research. Basic research to support the Space Vehicles

• Thermal management Basic research in this technology sub-area is focused on cryogenic technology. The objective of the cryogenic regenerator effort is to measure cryocooler regenerator performance under actual operating conditions. In addition, a numerical model for predicting regenerator performance will be developed. Numerical models do not currently exist for transient operation. The technology approach is to develop an experiment that incorporates a pulse tube cryocooler. Flow measuring and thermometer devices will be calibrated and data gathered in the 30-100 Hz range. Data will then be compared with existing models for both transient and steady state operation. Finally, an analytic model will be developed for the transient case and verified.
• Structures Two on-going basic research efforts are of particular interest in this area. One is developing fundamental understanding of how the different aspects of the space environment (atomic oxygen, UV, vacuum, protons, electrons, and hypervelocity debris) interact to effect space structures and structural materials. The other effort is exploring development of new mathematical control algorithms and approaches to structural control and vibration damping.
• Space Sensors Basic research on a Quantum Well Infrared Photon Multiplier (QWIPM) concept may lead to revolutionary passive sensor systems that are useful out to VLWIR wavelengths and operate at ambient temperatures. The QWIPM approach under study uses visible laser pumping to create a population inversion in asymmetric coupled quantum well pairs within the multiplier. With one quantum well in each pair tuned to an IR wavelength of interest, directional selection is used to discriminate and amplify the stimulated emission caused by signal photons. The QWIPM's output burst of IR photons can then be fed into an IR detector where it will greatly exceed the ambient temperature noise background. If successful, the QWIPM would greatly simplify present and enable new earthlimb and space surveillance applications.
• Satellite Communications The on-going basic research "critical path" efforts are for integrated optoelectronic materials and devices for avionic and ground dynamically reconfigurable Code Division Multiple Access (CDMA) system area network; lasercom; and low voltage, low power, high speed GaAs for communications processors, modems, and light weight crosslinks and multiband transceivers.

The Space Vehicles technology subarea also relies on the results of basic research from the Sensors and Electronics, Materials/Processes, and Information Systems and Technology area Panels.