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Quality Assurance Plan for Heat Source/Radioisotope Thermoelectric Generator Programs

Description: The purpose of this document is to serve as the Quality Assurance Plan for Heat Source/Radioisotope Thermoelectric Generator (HS/RTG) programs performed at EG&G Mound Applied Technologies. As such, it identifies and describes the systems and activities in place to support the requirements contained in DOE Order 5700.6C as reflected in MD-10334, Mound Quality Policy and Responsibilities and the DOE/RPSD supplement, OSA/PQAR-1, Programmatic Quality Assurance Requirements for Space and Terrestrial Nuclear Power Systems. Unique program requirements, including additions, modifications, and exceptions to these quality requirements, are contained in the appendices of this plan. Additional appendices will be added as new programs and activities are added to Mound's HS/RTG mission assignment.
Date: March 16, 1995
Creator: Gabriel, D. M.; Miller, G. D. & Bohne, W. A.
Partner: UNT Libraries Government Documents Department

Space nuclear power, propulsion, and related technologies.

Description: Sandia National Laboratories (Sandia) is one of the nation's largest research and development (R&D) facilities, with headquarters at Albuquerque, New Mexico; a laboratory at Livermore, California; and a test range near Tonopah, Nevada. Smaller testing facilities are also operated at other locations. Established in 1945, Sandia was operated by the University of California until 1949, when, at the request of President Truman, Sandia Corporation was formed as a subsidiary of Bell Lab's Western Electric Company to operate Sandia as a service to the U.S. Government without profit or fee. Sandia is currently operated for the U.S. Department of Energy (DOE) by AT&T Technologies, Inc., a wholly-owned subsidiary of AT&T. Sandia's responsibility is national security programs in defense and energy with primary emphasis on nuclear weapon research and development (R&D). However, Sandia also supports a wide variety of projects ranging from basic materials research to the design of specialized parachutes. Assets, owned by DOE and valued at more than $1.2 billion, include about 600 major buildings containing about 372,000 square meters (m2) (4 million square feet [ft2]) of floor space, located on land totalling approximately 1460 square kilometers (km2) (562 square miles [mi]). Sandia employs about 8500 people, the majority in Albuquerque, with about 1000 in Livermore. Approximately 60% of Sandia's employees are in technical and scientific positions, and the remainder are in crafts, skilled labor, and administrative positions. As a multiprogram national laboratory, Sandia has much to offer both industrial and government customers in pursuing space nuclear technologies. The purpose of this brochure is to provide the reader with a brief summary of Sandia's technical capabilities, test facilities, and example programs that relate to military and civilian objectives in space. Sandia is interested in forming partnerships with industry and government organizations, and has already formed several cooperative alliances and agreements. ...
Date: January 1, 1992
Creator: Berman, Marshall
Partner: UNT Libraries Government Documents Department

Fabrication and Testing of Full-Length Single-Cell Externally Fueled Converters for Thermionic Reactors

Description: The preceding paper described designs and analyses of thermionic reactors employing full-core-length single-cell converters with their heated emitters located on the outside of their internally cooled collectors, and it presented results of detailed parametric analyses which illustrate the benefits of this unconventional design. The present paper describes the fabrication and testing of full-length prototypical converters, both unfueled and fueled, and presents parametric results of electrically heated tests. The unfueled converter tests demonstrated the practicality of operating such long converters without shorting across a 0.3-mm interelectrode gap. They produced a measured peak output of 751 watts(e) from a single diode and a peak efficiency of 15.4%. The fueled converter tests measured the parametric performance of prototypic UO(subscript 2)-fueled converters designed for subsequent in-pile testing. They employed revolver-shaped tungsten elements with a central emitter hole surrounded by six fuel chambers. The full-length converters were heated by a water-cooled RF-induction coil inside an ion-pumped vacuum chamber. This required development of high-vacuum coaxial RF feedthroughs. In-pile test rules required multiple containment of the UO (subscript 2)-fuel, which complicated the fabrication of the test article and required successful development of techniques for welding tungsten and other refractory components. The test measured a peak power output of 530 watts(e) or 7.1 watts/cm (superscript 2) at an efficiency of 11.5%. There are three copies in the file. Cross-Reference a copy FSC-ESD-217-94-529 in the ESD files with a CID #8574.
Date: June 1, 1994
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Fabrication and Testing of Full-Length Single-Cell Externally Fueled Converters for Thermionic Reactors

Description: Paper presented at the 29th IECEC in Monterey, CA in August 1994. The present paper describes the fabrication and testing of full-length prototypcial converters, both unfueled and fueled, and presents parametric results of electrically heated tests.
Date: August 1, 1995
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Integration of Radioisotope Heat Source with Stirling Engine and Cooler for Venus Internal-Structure Mission

Description: The primary mission goal is to perform long-term seismic measurements on Venus, to study its largely unknown internal structure. The principal problem is that most payload components cannot long survive Venus's harsh environment, 90 bars at 500 degrees C. To meet the mission life goal, such components must be protected by a refrigerated payload bay. JPL Investigators have proposed a mission concept employing a lander with a spherical payload bay cooled to 25 degrees C by a Stirling cooler powered by a radioisotope-heated Sitrling engine. To support JPL's mission study, NASA/Lewis and MTI have proposed a conceptual design for a hydraulically coupled Stirling engine and cooler, and Fairchild Space - with support of the Department of Energy - has proposed a design and integration scheme for a suitable radioisotope heat source. The key integration problem is to devise a simple, light-weight, and reliable scheme for forcing the radioisotope decay heat to flow through the Stirling engine during operation on Venus, but to reject that heat to the external environment when the Stirling engine and cooler are not operating (e.g., during the cruise phase, when the landers are surrounded by heat shields needed for protection during subsequent entry into the Venusian atmosphere.) A design and integration scheme for achieving these goals, together with results of detailed thermal analyses, are described in this paper. There are 7 copies in the file.
Date: October 1, 1993
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design and Analysis of RTGs for CRAF and Cassini Missions

Description: This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications. The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. But subsequently JPL significantly increased both the power level and the mission duration for both missions, so that they can no longer by met by two standard RTGs. The resultant power gap must be closed either by reducing JPL's power demand (e.g., by decreasing contingency reserves) and/or by increasing the power system's output. One way under active consideration which more than meets the system power goal would be the addition of a third RTG for each mission. However, the author concluded that it may be possible to meet or closely approach the CRAF power demand goals with just two RTGs by relatively modest modification of their design and/or operating conditions. To explore that possibility, the effect of various modifications - either singly or in combination - was analyzed by Fairchild. The results indicate that modest modifications can meet or come very close to meeting the CRAF power goals with just two RTGs. Elimination of the third RTG would yield substantial cost and schedule savings. There are three copies in the file.
Date: November 30, 1990
Creator: Schock, Alfred; Noravian, Heros & Sankarankandath
Partner: UNT Libraries Government Documents Department

Design and Analysis of RTGs for CRAF and Cassini Missions; two copies - one dated 8/3/1990 and the other dated 11/8/1990.

Description: The paper describes the design and analysis of Radioisotope Thermoelectric Generators Integrated with JPL's CRAF and Cassini spacecraft. The principal purpose of the CRAF mission is the study of asteroids and comets, and the principal purpose of the Cassini mission is the study of asteroids, Saturn, and its moons (particularly Titan). Both missions will employ the Mariner/Mark-2 spacecraft, and each will be powered by two GPHS-RTGs. JPL's spacecraft designers wish to locate the two RTGs in close proximity to each other, resulting in mutual and unsymmetrical obstruction of their heat rejection paths. To support JPL's design studies, the U.S. Department of Energy asked Fairchild to determine the effect of the RTGs' proximity on their power output. As described in the paper, this required the development of novel analysis methods and computer codes for the coupled thermal and electrical analysis of obstructed RTGs with axial and circumferential temperature, voltage, and current variations. The code was validated against measured data of unobstructed RTG tests, and was used for the detailed analysis of the obstructed CRAF and Cassini RTGs. Also described is a new method for predicting the combined effect of fuel decay and thermoelectric degradation on the output of obstructed RTGs, which accounts for the effect of diminishing temperatures on degradation rates. For the 24-degree separation angle of JPL's original baseline design, and for the 35-degree RTG separation of JPL's revised design, the computed results indicate that the mutually obstructed GPHS/RTGs with standard fuel loading and operating temperatures can comfortably meet the JPL-specified power requirements for the CRAF mission and almost meet the specified requirements for the Cassini mission.
Date: October 8, 1990
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design and Analysis of RTGs for Solar and Martian Exploration Missions

Description: The paper described the results of design, analysis and spacecraft integration studies of Radioisotope Thermoelectric Generators (RTGs) for three unmanned space exploration missions. The three missions, consisting of the Mars Rover and Sample Return (MRSR) mission, the Solar Probe mission, and the Mars Global Net work (MGN) mission, are under study by the Jet Propulsion Laboratory (JPL) for the U.S. National Aeronautics and Space Administration (NASA). The NASA/JPL mission studies are supported by the U.S. Department of Energy's Office of Special Applications (DOE/OSA), which has commissioned Fairchild Space Company to carry out the required RTG design studies.
Date: May 1, 1990
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design and Spacecraft-Integration of RTGs for Solar Probe

Description: Presented at the 41st Congress of the IAF, October 6-12, 1990 in Dresden, FRG. The paper describes the design and analysis of Radioisotope Thermoelectric Generators integrated with JPL's planned Solar Probe spacecraft. The principle purpose of the Solar probe mission is to explore the solar corona by performing in-situ measurements at distances as close as four solar radii or 0.02 AU from the sun. This proximity to the sun imposes some unusual design constraints on the RTG and on its integration with the spacecraft. The results demonstrated that the obstructions result in significant performance penalties for the case of the standard GPHS-RTG design. Finally, the paper describes a simple empirical method for predicting the combined effect of fuel decay and thermoelectric degradation on the RTG's power output, and applies that method to predict the long-term power profile of the obstructed Solar Probe RTGs. The results indicate that the existing GPHS-RTG design, even without modifications can meet the JPL-prescribed EOM power requirement. There is also three copies in the file of an earlier version of this dated 8/3/1990 with the report number of FSC-ESD-217-90-470. The most current one is the IAF version (IAD-90-208) dated October 6-12, 1990.
Date: October 1, 1990
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design Modifications for Increasing the BOM and EOM Power Output and Reducing the Size and Mass of RTG for the Pluto Mission

Description: A companion paper analyzed the effect on source modules for three specific fuel options, and compared the predicted power output with JPL's latest goals for the Pluto Fast Flyby (PFF) mission. The results showed that a 5-module RTG cannot fully meet JPL's goals with any of the available fuels; and that a 6-module RTG more than meets those goals with Russian fuel, almost meets them with U.S. (Cassini-type) fuel, but still falls far short of meeting them with the depleted fuel from the aged (1982) Galileo spare RTG. The inadequacy of the aged fuel was disappointing,because heat source modules made from it already exist, and their use in PFF could result in substantial cost savings. The present paper describes additional analyses which showed that a six-module RTG with the aged fuel can meet JPL's stipulated power margin with a relatively simple design modification, that a second design modification makes it possible to recover all of the mass and size penalty for going from five to six heat source modules, and that a third modification could raise the EOM power margin to 16%. There are four copies in the file. Cross Reference ESD Files FSC-ESD-217-94-531 (CID #8572)
Date: June 1, 1994
Creator: Schock, Alfred; Or, Chuen T & Kumar, Vasanth
Partner: UNT Libraries Government Documents Department

Design Modifications for Increasing the BOm and EOM Power Output and Reducing the Size and Mass of RTG for the Pluto Mission

Description: Paper presented at the 29th IECEC in Monterey, CA in August 1994. A companion paper analyzed the effect on source modules for three specific fuel options, and compared the predicted power output with JPL's latest goals for the Pluto Fast Flyby (PFF) mission. The results showed that a 5-module RTG cannot fully meet JPL's goals with any of the available fuels; and that a 6-module RTG more than meets those goals with Russian fuel, almost meets them with U.S. (Cassini-type) fuel, but still falls far short of meeting them with the depleted fuel from the aged (1982) Galileo spare RTG. The inadequacy of the aged fuel was disappointing,because heat source modules made from it already exist, and their use in PFF could result in substantial cost savings. The present paper describes additional analyses which showed that a six-module RTG with the aged fuel can meet JPL's stipulated power margin with a relatively simple design modification, that a second design modification makes it possible to recover all of the mass and size penalty for going from five to six heat source modules, and that a third modification could raise the EOM power margin to 16%.
Date: August 1, 1994
Creator: Schock, Alfred; Or, Chuen T & Kumar, Vasanth
Partner: UNT Libraries Government Documents Department

Design of Small Impact-Resistant RTGs for Global Network of Unmanned Mars Landers

Description: Presented at the 42nd Congress of the IAF, October 5-11, 1991 in Montreal, Canada. This paper presents the results of Fairchild's work in support of DOE to perform RTG design studies for this mission. The key problem in designing these RTGs is how to enable the generators to tolerate substantially higher g-loads than those encountered on previous RTG missions. The Fairchild studies resulted in designs of compact RTGs based on flight-proven and safety-qualified heat source components, with a number of novel features designed to provide the desired high impact tolerance. The present paper describes those designs and their rationale, and a preliminary, quasi-static impact analysis that yielded very encouraging results. They indicate that these RTGs have sufficient impact resistance to enable survival of landers without retrorockets. This would result in significant cost savings. There are four copies in the file. Two copies of a presentation with the same title by Al Schock dated June 26/27, 1991 is attached. There are two copies of a Fairchild document, undated included. There is also two copies dated 6/26/1991 with the report number FSC-ESD-217-91-495 and one copy of a ducument, dated 7/11/191 with the report number FSC-ESD-217-91-495A. There are four copies with the same title in the file, but undated. These copies have a different Abstract and are similar, but not the exact version as the other copies.
Date: October 1, 1991
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design of Small Impact-Resistant RTGs for Global Network of Unmanned Mars Landers

Description: Ongoing studies by the National Aeronautics and Space Administration (NASA) for the robotic exploration of Mars contemplate a network of at least twenty small and relatively inexpensive landers distributed over both low and high latitudes of the Martian globe. They are intended to explore the structural, mineralogical, and chemical characteristics of the Martian soil, search for possible subsurface trapped ice, and collect long-term seismological and meteorological data over a period of ten years. They can also serve as precursors for later unmanned and manned Mars missions.; The collected data will be transmitted periodically, either directly to Earth or indirectly via an orbiting relay. The choice of transmission will determine the required power, which is currently expected to be between 2 and 12 watts(e) per lander. This could be supplied either by solar arrays or by Radioisotope Thermoelectric Generators (RTGs). Solar-powered landers could only be used for low Martian latitudes, but RTG-powered landers can be used for both low and high latitudes. Moreover, RTGs are less affected by Martian sandstorms and can be modified to resist high-G-load impacts. High impact resistance is a critical goal. It is desired by the mission designers, to minimize the mass and complexity of the system needed to decelerate the landers to a survivable impact velocity.; To support the NASA system studies, the U.S. Department of Energy's Office of Special Applications (DOE/OSA) asked Fairchild to perform RTG design studies for this mission. The key problem in designing these RTGs is how to enable the generators to tolerate substantially higher G-loads than those encountered on previous RTG missions.; The Fairchild studies resulted in designs of compact RTGs based on flight-proven and safety-qualified heat source components, with a number of novel features designed to provide the desired high impact tolerance. The present paper describes those designs and their ...
Date: June 26, 1991
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design, Analysis, and Optimization of a Radioisotope Thermophotovoltaic (RTPV) Generator, and its Applicability to an Illustrative Space Mission

Description: Paper presented at the 45th Congress of the IAF in Jerusalem, Israel, October 1994. The paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator (RTPV), to complement similar studies of Radioisotope Thermoelectric Generators (RTGs) and Stirling Generators (RSGs) previously published by the authors. To focus the design effort, it was decided to direct it at a specific illustrative space mission, Pluto Fast Flyby (PFF). That mission, under study by the JPL, envisages a direct eight to nine-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief flyby of the planet and its moon Charon, and transmission of the recorded science data to Earth during a six-week post-encounter cruise.
Date: October 1, 1994
Creator: Schock, Alfred; Mukunda, Meera; Or, Chuen T; Kumar, Vasanth & Summers, G.
Partner: UNT Libraries Government Documents Department

Design, Analysis, and Spacecraft Integration of RTGs for CRAF and Cassini Missions

Description: This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications.; The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. However, JPL subsequently raised both the power demand profile and the duration for both missions, to the point where two standard RTGs could no longer provide the desired power margin. Each mission can be satisfied by adding a third RTG, and in the case of the Cassini mission the use of three RTGs appears to be unavoidable. In the case of the CRAF mission, there appears to be a possibility that modest modifications of the RTGs' design and/or operating scheme and meet the missions' power demand without the addition of a third RTG. The potential saving in cost and schedule pressure prompted Fairchild to undertake a study of various obvious and not-so-obvious stratagems, either singly or in combination, to determine whether they would make it possible to meet the specified power demand with two RTGs.; The various stratagems investigated by Fairchild and their effect on performance are presented. The analytical results indicate that a combination of relatively modest RTG modifications could come very close to meeting the JPL-specified CRAF power demand goals. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use three RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power ...
Date: July 10, 1991
Creator: Schock, Alfred; Or, Chuen T & Noravian, Heros
Partner: UNT Libraries Government Documents Department

Design, Analysis, and Spacecraft Integration of RTGs for CRAF and Cassini Missions

Description: This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications.; The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. However, JPL subsequently raised both the power demand profile and the duration for both missions, to the point where two standard RTGs could no longer provide the desired power margin. Each mission can be satisfied by adding a third RTG, and in the case of the Cassini mission the use of three RTGs appears to be unavoidable. In the case of the CRAF mission, there appears to be a possibility that modest modifications of the RTGs' design and/or operating scheme and meet the missions' power demand without the addition of a third RTG. The potential saving in cost and schedule pressure prompted Fairchild to undertake a study of various obvious and not-so-obvious stratagems, either singly or in combination, to determine whether they would make it possible to meet the specified power demand with two RTSs.; The various stratagems investigated by Fairchild and their effect on performance are presented. The analytical results indicate that a combination of relatively modest RTG modifications could come very close to meeting the JPL-specified CRAF power demand goals. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use three RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power ...
Date: April 2, 1991
Creator: Schock, Alfred; Or, Chuen T & Noravian, Heros
Partner: UNT Libraries Government Documents Department

Design, Analysis, and Spacecraft Integration of RTGs for CRAF and Cassini Missions

Description: This report consists of two parts. Part 1 describes the development of novel analytical methods needed to predict the BOM performance and the subsequent performance degradation of the mutually obstructed RTGs for the CRAF and Cassini missions. Part II applies those methods to the two missions, presents the resultant predictions, and discusses their programmatic implications. The results indicate that JPL's original power demand goals could have been met with two standard GPHS RTGs for each mission. However, JPL subsequently raised both the power demand profile and the duration for both missions, to the point where two standard RTGs could no longer provide the desired power margin. Each mission can be satisfied by adding a third RTG, and in the case of the Cassini mission the use of three RTGs appears to be unavoidable. In the case of the CRAF mission, there appears to be a possibility that modest modifications of the RTGs' design and/or operating scheme and meet the missions' power demand without the addition of a third RTG. The potential saving in cost and schedule pressure prompted Fairchild to undertake a study of various obvious and not-so-obvious stratagems, either singly or in combination, to determine whether they would make it possible to meet the specified power demand with two RTSs. The various stratagems investigated by Fairchild and their effect on performance are presented. The analytical results indicate that a combination of relatively modest RTG modifications could come very close to meeting the JPL-specified CRAF power demand goals. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use three RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power ...
Date: April 2, 1991
Creator: Schock, Alfred; Or, Chuen T & Noravian, Heros
Partner: UNT Libraries Government Documents Department

Design and Analysis of RTGs for CRAF and Cassini Missions

Description: The design and analysis of Radioisotope Thermoelectric Generators integrated with JPL's CRAF and Cassini spacecraft are described. The principal purposed of the CRAF mission are the study of asteroids and comets, and the principal purposes of the Cassini mission are the study of asteroids, Saturn, and its moons (particularly Titan). Both missions will employ the Mariner/Mark-2 spacecraft, and each will be powered by two GPHS-RTGs. JPL's spacecraft designers wish to locate the two RTGs in close proximity to each other, resulting in mutual and unsymmetrical obstruction of their heat rejection paths. To support JPL's design studies, the U.S. Department of Energy asked Fairchild to determine the effect of the RTGs' proximity on their power output. This required the development of novel analysis methods and computer codes, described in this report, for the coupled thermal and electrical analysis of obstructed RTGs with axial and circumferential temperature, voltage, and current variations. The code was validated against measured data of unobstructed RTG tests, and was used for the detailed analysis of the obstructed CRAF/Cassini RTGs. Also described is a new method for predicting the combined effect of fuel decay and thermoelectric degradation on the output of obstructed RTGs, which accounts for the effect of diminishing temperatures on degradation rates. The computed results indicate that for the 24-degree separation angle of JPL's baseline design, the mutually obstructed standard GPHS/RTGs show adequate power margins for the CRAF mission, but slightly negative margins for the Cassini mission.
Date: January 1, 1991
Creator: Schock, Alfred; Noravian, Heros; Or, Chuen & Sankarankandath, Kumar
Partner: UNT Libraries Government Documents Department

Development and Use of the Galileo and Ulysses Power Sources

Description: Paper presented at the 45th Congress of the International Astronautical Federation, October 1994. The Galileo mission to Jupiter and the Ulysses mission to explore the polar regions of the Sun required a new power source: the general-purpose heat source radioisotope thermoelectric generator (GPHS-RTG), the most powerful RTG yet flow. Four flight-qualified GPHS-RTGs were fabricated with one that is being used on Ulysses, two that are being used on Galileo and one that was a common spare (and is now available for the Cassini mission to Saturn). In addition, and Engineering Unit and a Qualification Unit were fabricated to qualify the design for space through rigorous ground tests. This paper summarizes the ground testing and performance predictions showing that the GPHS-RTGs have met and will continue to meet or exceed the performance requirements of the ongoing Galileo and Ulysses missions. There are two copies in the file.
Date: October 1, 1994
Creator: Bennett, Gary L; Hemler, Richard J & Schock, Alfred
Partner: UNT Libraries Government Documents Department

Effect of Fuel and Design Options on RTG Performance versus PFF Power Demand

Description: Paper presented at the 29th IECEC in Monterey, CA in August 1994. The present paper confines its attention to the relatively conservative option employing standard thermoelectric unicouples, since that may be the only one flight-ready for the projected PFF launch in 2001. There are four copies in the file; also a copy in the ESD files. Included in the file are two previous documents with the same title dated 4/18/1994.
Date: August 1, 1994
Creator: Schock, Alfred & Or, Chuen T
Partner: UNT Libraries Government Documents Department

Analysis of Possible Stratagems for Enhancing the EOM Power of RTGs for the CRAF Mission

Description: Paper presented at the 26th IECEC in Boston, MA August 4-9, 1991. This paper describes the various stratagems investigated and discusses their drawbacks and their effectiveness. The analytical results indicated that a combination of relatively modest RTG modifications that could be implemented in time for the mission could come very close to meeting the CRAF power demand goals specified by JPL. However, since even with the modifications the two RTGs did not provide sufficient margin for possible further growth in power demand, the JPL project team ultimately decided to use 3 RTGs for the CRAF mission also. This had the decisive advantage of eliminating the need for load switching to reduce the power demand peaks. The purpose of this paper is to document the various power enhancement schemes analyzed and their computed effectiveness, for possible future applications. There are three copies in the file.
Date: August 1, 1991
Creator: Schock, Alfred; Or, Chuen T & Noravian, Heros
Partner: UNT Libraries Government Documents Department

Analysis, Optimization, and Assessment of Radioisotope Thermophotovoltaic System Design for an Illustrative Space Mission

Description: A companion paper presented at this conference described the design of a Radioisotope Thermophotovoltaic (RTPV) Generator for an illustrative space mission (Pluto Fast Flyby). It presented a detailed design of an integrated system consisting of a radioisotope heat source, a thermophotovoltaic converter, and an optimized heat rejection system. The present paper describes the thermal, electrical, and structural analyses which led to that optimized design, and compares the computed RTPV performance to that of a Radioisotope Thermoelectric Generator (RTG) designed for the same mission. RTPV's are of course much less mature than RTGs, but our results indicate that - when fully developed - they could result in a 60% reduction of the heat source's mass, cost, and fuel loading, a 50% reduction of generator mass, a tripling of the power system's specific power, and a quadrupling of its efficiency. The paper concludes by briefly summarizing the RTPV's current technology status and assessing its potential applicability for the PFF mission. For other power systems (e.g. RTGs), demonstrating their flight readiness for a long mission is a very time-consuming process to determine the long-term effect of temperature-induced degradation mechanisms. But for the case of the described RTPV design, the paper lists a number of factors, primarily its cold (0 to 10 degrees C) converter temperature, that may greatly reduce the need for long-term tests to demonstrate generator lifetime. In any event, our analytical results suggest that the RTPV generator, when developed by DOE and/or NASA, would be quite valuable not only for the Pluto mission but also for other future missions requiring small, long-lived, low mass generators. Another copy is in the Energy Systems files.
Date: June 28, 1994
Creator: Schock, Alfred; Mukunda, Meera & Summers, G.
Partner: UNT Libraries Government Documents Department

Closed-Form Solution for the Effect of Fuel Decay and Thermoelectric Degradation on Output of SiGe RTGs

Description: Presented at the 26th IECEC in Boston, MA August 4-9, 1991. The paper derives a closed-form solution for the long-term effect of fuel decay and thermoelectric degradation on the performance of Radioisotope Thermoelectric Generators employing silicon-germanium converter elements. RTGs of this type were used to power the recent Galileo and Ulysses space exploration missions, and are slated for use on the upcoming CRAF and Cassini missions. The method described applies not only to uniform-temperature RTGs, but also to RTGs with significant axial and circumferential variations in the couples' cold-junction temperatures and voltages (due to unsymmetrically obstructed heat rejection paths). This is important for the mutually blocking RTGs on the CRAF and Cassini spacecraft, and even more so for the reflector-blocked Solar Probe RTGs. The method for predicting RTG degradation that is dervied in this paper is based on both analytical and experimental data. It accounts for the effect of diminishing hot-junction temperatures on thermoelectric degradation rates. The method leads to an integral equation, for which the author was able to derive a closed-form solution. The solution was successfully validated by comparison with long-term test data. It enables the RTG designer to predict the power output profile throughout the mission, to ensure that it satisfies the mission's power demand profile. There are four copies in the file.
Date: August 1, 1991
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department