Patrick Frye

Integrated Solar Upper Stage (ISUS) engine ground demonstration (EGD)

The Integrated Solar Upper Stage (ISUS) Engine Ground Demonstration (EGD) Program sponsored by the Air Force Phillips Laboratory (PL) conducted a full-up ground demonstration of a solar thermal power and propulsion system at NASA Lewis Research Center in mid-1997. This test validated system capability in a relevant environment, bringing ISUS to a Technology Readiness Level (TRL) of 6, and paving the way for a flight demonstration by the turn of the century. The ISUS technology offers high specific impulse propulsion at moderate thrust levels and high power, radiation-tolerant electrical power generation. This bimodal system capability offers savings in launch vehicle costs and/or substantial increases in payload power and mass over present day satellite systems. The ISUS EGD consisted of the solar receiver/absorber/converter (RAC), power generation, management, and distribution subsystems, solar concentrator, and cryogen storage/feed subsystems. Simulation of a low Earth orbit (LEO)-to-Molniya orbit transfer (30-day trip time) as well as characterization of on-orbit power production was planned for this ground test. This paper describes the EGD test integration, setup and checkout, system acceptance tests, performance mapping, and exercise of the system through a mission-like series of operations. Key test data collected during the test series is reported along with a summary of technical insights achieved as a result of the experiment. Test data includes propulsion performance as derived from flowrate, temperature, and pressure measurements and the total number of thermal cycles.The Integrated Solar Upper Stage (ISUS) Engine Ground Demonstration (EGD) Program sponsored by the Air Force Phillips Laboratory (PL) conducted a full-up ground demonstration of a solar thermal power and propulsion system at NASA Lewis Research Center in mid-1997. This test validated system capability in a relevant environment, bringing ISUS to a Technology Readiness Level (TRL) of 6, and paving the way for a flight demonstration by the turn of the century. The ISUS technology offers high specific impulse propulsion at moderate thrust levels and high power, radiation-tolerant electrical power generation. This bimodal system capability offers savings in launch vehicle costs and/or substantial increases in payload power and mass over present day satellite systems. The ISUS EGD consisted of the solar receiver/absorber/converter (RAC), power generation, management, and distribution subsystems, solar concentrator, and cryogen storage/feed subsystems. Simulation of a low Earth orbit (LEO)-to-Molniya orbit trans...

SOLAR THERMAL OTV-APPLICATIONS TO REUSABLE AND EXPENDABLE LAUNCH VEHICLES

Abstract The Solar Orbit Transfer Vehicle (SOTV) program being sponsored by the U.S. Air Force Research Laboratory (AFRL) is developing technology that will engender revolutionary benefits to satellites and orbitto-orbit transfer systems. Solar thermal propulsion offers significant advantages for near-term expendable launch vehicles (ELVs) such as Delta IV, mid- to farterm reusable launch vehicles (RLVs) and ultimately to manned exploration of the Moon and Mars. Solar thermal propulsion uses a relatively large mirrored concentrator to focus solar energy onto a compact absorber, which is in turn heated to > 2200 K. This heat can then be used in two major ways. By flowing hydrogen or another working fluid through the absorber, high efficiency thrust can be generated with 800 sec or more specific impulse (Isp), almost twice that of conventional cryogenic stages and comparable with typical solid-core nuclear thermal stages. Within a decade, advances in materials and fabrication processes hold the promise of the Isp ranging up to 1,100 sec. In addition, attached thermionic or alkali metal thermoelectric converter (AMTEC) power converters can be used to generate 20 to 100 kilowatts (kW) of electricity. The SOTV Space Experiment (SOTV-SE), planned to be flown in 2003, will demonstrate both hydrogen propulsion and thermionic power generation, including advanced lightweight deployable concentrators suitable for large-scale applications. Evolutionary geosynchronous-transfer orbit/ geosynchronous-Earth orbit (GTO/GEO) payload lift capability improvements of 50% or more to the Delta IV launch vehicles could be implemented as part of the Delta IV P4I plan shortly thereafter. Beyond that, SOTV technology should allow long-term storage of stages in orbits up to GEO with tremendous maneuvering capability, potentially 4 to 5 km/sec or more. Servicing of low-Earth orbit (LEO) and GEO assets and reusable (ROTVs) are other possible applications. Offering a combination of high Isp and high thrust/weight together with thrust levels from 10 to 100 lb or more, a large-scale SOTV offers a low-cost alternative to nuclear thermal or solar electric stages for cargo missions to the Moon and Mars. This paper describes the SOTV-SE as well as these and other potential applications of this integrated power/propulsion technology.

NERVA-Derived Concept for a Bimodal Nuclear Thermal Rocket

The Nuclear Thermal Rocket is an enabling technology for human exploration missions. The “bimodal” NTR (BNTR) provides a novel approach to meeting both propulsion and power requirements of future manned and robotic missions. The purpose of this study was to evaluate tie‐tube cooling configurations, NTR performance, Brayton cycle performance, and LOX‐Augmented NTR (LANTR) feasibility to arrive at a point of departure BNTR configuration for subsequent system definition.

Development of segmented thermoelectric multicouple converter technology

The Jet Propulsion Laboratory (JPL), Pratt & Whitney Rocketdyne, and Teledyne Energy Systems, Inc., have teamed together under JPL leadership to develop the next generation of advanced thermoelectric space reactor power conversion systems. The program goals are to develop the technologies needed to achieve a space nuclear power system specific mass goal of less than 30 kg/kW at the 100 kW power level with a greater than 15 year lifetime. The technologies required for such a power system include liquid metal cooled reactors with outlet temperatures ranging from 1125 K up to 1325 K, segmented thermoelectric multicouple converter (STMC) arrays which can achieve greater than 8 percent system efficiency and carbon-carbon heat pipe radiator panels to reduce the radiator subsystem areal density to a goal of 5 kg/m . The STMC programs development efforts focused on a highly compact conductively coupled modular thermoelectric converter assembly (TCA) design. STMC design efforts were based on a multicouple design similar to the SP-100 Programs design but using segmented thermoelectric (TE) legs rather than the single alloy silicon-germanium legs. Efforts have addressed in parallel the selection and optimization of the most promising high temperature thermoelectric materials, the development of the various STMC components and sub-assemblies, design, analysis, fabrication and assembly of subscale STMC devices as well as scale-up plans to the 100 kW-class power level. The performance of the selected high temperature TE materials and initial thermal, electrical and mechanical test results on several STMC demonstration devices are reported

Segmented Thermoelectric Multicouple Converter Technology Development

The primary objectives of the segmented thermoelectric multicouple converter (STMC) technology development effort are: to define a conceptual design for a passive, low mass (3000 kg), long life (15 years) thermoelectric advanced Space Reactor Power System that provides 100kWe 400 Volt dc power for a 6000 volt dc electric propulsion system, to prepare a preliminary design of the power conversion system and to prepare technology development plan to advance power conversion system technology to TRL 6. The SRPS consists of a heat pipe cooled reactor radiatively couple to high efficiency solid‐state segmented thermoelectric multicouple converters which are conductively coupled to a low mass heat pipe radiator. The SRPS conceptual design as well as the Power Conversion System preliminary design is complete and their description reported in this paper.

Solar thermal propulsion status and future

The status of solar absorber/thruster research is reviewed, and potential future applications and advanced solar thermal propulsion concepts are discussed. Emphasis is placed on two concepts, the windowless heat exchanger cavity and the porous material absorption concepts. Mission studies demonstrate greater than 50 percent increase in payload compared to chemical propulsion for a LEO-to-GEO mission. Alternative missions that have been considered for this concept include the Thousand Astronomical Unit mission, LEO-to-lunar orbit, and other SEI missions. It is pointed out that solar thermal propulsion is inherently simple and capable of moderate-to-high engine performance at moderate-to-low thrust levels. 15 refs.

Solar bimodal mission and operational analysis

Recent interest by both government and industry has prompted evaluation of a solar bimodal upper stage for propulsion/power applications in Earth orbit. The solar bimodal system provides an integral propulsion and power system for the orbit transfer and on‐orbit phases of a satellite mission. This paper presents an initial systems evaluation of a solar bimodal system used to place satellite payloads for Geosynchronous Earth Orbit (GEO), High Earth Orbit (HEO‐Molniya class), and Mid Earth Orbit (GPS class) missions with emphasis on the GEO mission. The analysis was performed as part of the Operational Effectiveness and Cost Comparison Study (OECS) sponsored by Phillips Laboratory (PL). The solar bimodal concept was investigated on a mission operational and performance basis for on‐orbit power levels ranging from less than 1 kWe to 20 kWe. Atlas IIAS, Delta 7920, and Titan IV launch vehicles were considered for injecting the solar bimodal upper stage and payload into initial orbits ranging from Low Earth Or...

Integrated Solar Upper Stage (ISUS) mission analysis

Solar thermal propulsion and propulsion/power systems were identified as key technologies by the Operational Effectiveness and Cost Comparison Study. These technologies were found to be pervasively cost effective with short transfer times and very good performance across a wide range of missions (Feuchter 1996). The on-going Integrated Solar Upper Stage (ISUS) Program sponsored by Phillips Laboratory represents development of one such solar thermal propulsion/power system. This paper presents conceptual designs, mission analysis results, and trade study results for a system evaluation of ISUS for future military payloads. These payloads primarily include high power communication satellites for geo-synchronous equatorial orbit (GEO) applications.

Integrated solar upper stage (ISUS) space demonstration design

High temperature solar thermal propulsion/power systems will enable the placement of higher power satellite systems launched from smaller, less expensive launch vehicles. The on-going Integrated Solar Upper Stage (ISUS) Program sponsored by Phillips Laboratory is one such solar thermal system. A system test of an engine ground test configuration of ISUS is planned for Spring, 1997. The next step in the development of the ISUS system will be a flight demonstration mission. This paper details the conceptual designs for two potential ISUS space demonstration configurations. These designs were developed with a design-to-cost philosophy for a LEO (low Earth orbit) to GEO (geosynchronous equatorial orbit) and LEO to HEEO (highly elliptical Earth orbit) flight demonstration missions. Design considerations included packaging within the selected launch vehicle fairings (Pegasus XL and SSLV Taurus), system performance, propellant selection (H2, CH4, or NH3), and 100–150 watts of power production using thermionic di...