Dynamic power conversion offers the potential to produce Radioisotope Power Systems (RPS) that ge... more Dynamic power conversion offers the potential to produce Radioisotope Power Systems (RPS) that generate higher power outputs and utilize the Pu-238 radioisotope more efficiently than Radioisotope Thermoelectric Generators. Additionally, dynamic systems offer the potential of producing generators with significantly reduced mechanical degradation over the course of deep space missions so that more power will be available at the end of the mission when it is needed for both powering the science and transmitting the results. The development of dynamic generators involves addressing technical issues not typically associated with traditional thermoelectric generators. Developing longlife, robust and reliable dynamic conversion technology is challenging yet essential to building a suitable generator. Considerations include working within existing handling infrastructure, where possible, so that development costs can be kept low and integrating dynamic generators into spacecraft, which may be more complex than integration of static systems. Methods of interfacing to and controlling a dynamic generator must also be considered and new potential failure modes must be taken into account. This paper will address some of the key issues of dynamic RPS design, development and adaption.
Given increasing complexity of many safety-critical systems, many organizations like NASA need to... more Given increasing complexity of many safety-critical systems, many organizations like NASA need to identify when, where, and how inappropriate perceptions of risk and anchoring of trust affect technology development and acceptance, primarily from the perspective of engineers and related management. Using the adoption of Dynamic Radioisotope Power Systems (RPS) for space exploration as a backdrop, we define and explain factors that contribute to inappropriate risk perception of various stakeholders. Three case studies (Mars Science Laboratory, Parker Solar Probe, and Titan Mare Explorer) demonstrate how NASA considered Dynamic RPS but decided against the new technology for less efficient alternatives of solar power and solid-state RPS. In the case of Dynamic RPS, increased design complexity that differs from previous successful solid-state power systems flown on the Voyager probes and Cassini spacecraft is one contributing factor, but not the only one. Problems with system performance and incorrect technology readiness labeling of Dynamic RPS technology led to an increased perception of distrust in Dynamic RPS for future missions. We also find that the perception of risk for Dynamic RPS future development is exacerbated by ongoing organizational challenges requiring multi-agency collaboration and coordination. Difficulties in setting realistic 5. MITIGATION STRATEGIES…………………8 6. CONCLUSION………………………………9 ACKNOWLEDGEMENTS………………………10 REFERENCES…………………………………10 BIOGRAPHY………………………………….14
The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and availabl... more The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or impossible to meet the needs of the missions. To meet this goal, the RPS Program, working closely with the Department of Energy, performs mission and system studies (such as the recently released Nuclear Power Assessment Study), assesses the readiness of promising technologies to infuse in future generators, assesses the sustainment of key RPS capabilities and knowledge, forecasts and tracks the Programs budgetary needs, and disseminates current information about RPS to the community of potential users. This process has been refined and used to determine the current content of the RPS Programs portfolio. This portfolio currently includes an effort to mature advanced thermoelectric technology for possible integration into an enhanced Multi-Mis...
Real-time sensor validation improves process monitoring and control system dependability by ensur... more Real-time sensor validation improves process monitoring and control system dependability by ensuring data integrity through automated detection of sensor data failures. The NASA Lewis Research Center, Expert Microsystems, and Intelligent Software Associates have developed an innovative sensor validation system that can automatically detect automated sensor failures in real-time for all types of mission-critical systems. This system consists of a sensor validation network development system and a real-time kernel. The network development system provides tools that enable systems engineers to automatically generate software that can be embedded within an application. The sensor validation methodology captured by these tools can be scaled to validate any number of sensors, and permits users to specify system sensitivity. The resulting software reliably detects all types of sensor data failures.
Introduction: For more than five decades, Radioisotope Power Systems (RPS) have played a critical... more Introduction: For more than five decades, Radioisotope Power Systems (RPS) have played a critical role in the exploration of space, enabling missions of scientific discovery to destinations across the solar system by providing electrical power to explore remote and challenging environments some of the hardest to reach, darkest, and coldest locations in the solar system. The recently reissued National Space Policy of the United States (June 2010) directs that “The United States shall develop and use space nuclear power systems where such systems safely enable or significantly enhance space exploration or operational capabilities”[1]. Moreover, the National Research Council report “Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration” (2009) by the Radioisotope Power Systems Committee illustrates how important RPS availability is for reaching the outer solar system where sunlight is very faint [2]. RPS could enable many deep space missions whe...
Radioisotope Thermoelectric Generators (RTGs) have been used to power NASA missions of various ty... more Radioisotope Thermoelectric Generators (RTGs) have been used to power NASA missions of various types throughout the past five decades. The most recent RTG iteration, used for NASA's Mars Science Laboratory, is the Multi-Mission RTG (MMRTG), which is currently the only spaceflight-qualified system available. The U.S. planetary science community has expressed a desire for more power system options to be available to accommodate a range of ambitious future mission concepts across the solar system. Recent advancements in thermoelectric (TE) materials technology have raised a potential for significantly increased efficiency in future RTGs, which helped spur a recent in-depth NASA study of options for future systems. A “next-generation” RTG study was conducted to develop new RTG concepts that could meet the needs of planetary science missions through the 2030s and beyond. A Next-Generation RTG would aim to extend the types of potential NASA missions able to be supported, while fulfilling requirements related to technical risk and schedule. In this study, 21 potential thermoelectric couple configurations were analyzed by considering various high-performance, high-temperature TE materials and segmentation techniques that maximize convertor efficiency and power density. System modularity was explored, and found to be a promising means to offer improved flexibility for NASA mission concepts with varying scope and power requirements. This paper presents the results of the study, demonstrating the viability of developing an updated RTG system design, and defining conceptual system approaches for a new, potentially revolutionary RTG.
The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to... more The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or impossible to meet potential future mission needs. To meet this goal, the RPS Program manages investments in RPS technologies and RPS system development, working closely with the Department of Energy. This paper provides an overview of the RPS Program content and status, its collaborations with potential RPS users, and the approach employed to maintain the readiness of RPS to support future NASA mission concepts.
15th International Energy Conversion Engineering Conference, Jul 7, 2017
The NASA Radioisotope Power Systems (RPS) Program's goal is to make RPS available for the explora... more The NASA Radioisotope Power Systems (RPS) Program's goal is to make RPS available for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible to use to meet mission needs. To meet this goal, the RPS Program manages investments in RPS system development and RPS technologies. The RPS Program exists to support NASA's Science Mission Directorate (SMD). The RPS Program provides strategic leadership for RPS, enables the availability of RPS for use by the planetary science community, successfully executes RPS flight projects and mission deployments, maintains a robust technology development portfolio, coordinates RPS related National Environmental Policy Act (NEPA) and Nuclear Launch Safety (NLS) approval processes for SMD, maintains insight into the Department of Energy (DOE) implementation of NASA funded RPS production infrastructure operations, including implementation of the NASA funded heat-source plutonium production restart efforts. This paper will provide a status of recent RPS activities and accomplishments.
35th Joint Propulsion Conference and Exhibit, 1999
Real-time validation of rocket engine sensor data improves mission safety and reduces flight oper... more Real-time validation of rocket engine sensor data improves mission safety and reduces flight operations and ground test costs. NASA Glenn Research Center, in partnership with Expert Microsystems, Inc., has developed an innovative sensor validation software application enabling real-time, automated sensor failure detection for all types of mission critical systems. This technology is broadly applicable to any aerospace or industrial control and safety system where: 0 Time-critical, closed-loop control or safety monitoring depend on sensor input; e Unexpected process interruptions due to sensor failures or false alarms are unsafe or uneconomical. Testing performed to date has verified that these sensor validation algorithms enable highly reliable real-time data validation for mission critical Space Shuttle Main Engine performance sensors, including the turbine discharge temperatures on both turbopumps. In this paper, we describe the current development status of the Sensor Validation System software and its application to the production of an on-line Space Shuttle Main Engine telemetry data monitoring system.
Radioisotope Power Systems (RPS) have been and will be enabling or significantly enhancing for ma... more Radioisotope Power Systems (RPS) have been and will be enabling or significantly enhancing for many missions, including several concepts identified in the 2011 Planetary Science Decadal Survey. Some mission planners and science investigators might have concerns about possible impacts from RPS-induced conditions upon the scientific capabilities of their mission concepts. To alleviate these concerns, this paper looks at existing and potential future RPS designs, and examines their potential radiation, thermal, vibration, electromagnetic interference (EMI), and magnetic fields impacts on representative science instruments and science measurements. Radiation impacts from RPS on science instruments are of potential concern for instruments with optical detectors and instruments with high-voltage electronics. The two main areas of concern are noise effects on the instrument measurements, and long-term effects of instrument damage. While RPS by their nature will contribute to total radiation dose, their addition for most missions should be relatively small. For example, the gamma dose rate from one Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) would be an order of magnitude lower than the environmental dose rate at Mars, and would have a correspondingly lower contribution to instrument noise and to any permanent damage to payload sensors. Increasing the number of General Purpose Heat Source (GPHS) modules used in an RPS would be expected to increase the generated radiation proportionally; however, the effect of more GPHS modules is mitigated from a strictly linear relationship by self-shielding effects. The radiation field of an RPS is anisotropic due to the deviation of the modules from a point-source-geometry. For particularly sensitive instruments, the total radiation dose could be mitigated with separation or application of spot shielding. Though a new, higher-power RPS could generate more heat per unit than current designs, thermal impact to the flight system could be mitigated with shading and pointing if required by the mission. Alternatively, excess heat could prove beneficial in providing needed heat to spacecraft components and instruments in some thermal environments. Vibration for a new higher-power Stirling Radioisotope Generator (SRG) would be expected to be similar to the recent Advanced Stirling Radioisotope Generator (ASRG) design. While vibration should be low, it must be considered and addressed during spacecraft and instrument design. EMI and magnetic fields for new RPS concepts are expected to be low as for the current RPS, but must be considered and addressed if the mission includes sensitive instruments such as magnetometers. The assessment conducted for this paper focused on orbiter instrument payloads for two representative mission concepts - a Titan Saturn System Mission (TSSM) and a Uranus Orbiter and Probe (UOP) - since both of these Decadal Survey concepts would include many diverse instruments on board. This paper describes how the potential impacts of the RPS on science instruments and measurements were assessed and which impacts were addressed. Then, this paper suggests mitigation strategies against those impacts, and provides an overview of several topics that would benefit from further work.
Technology infusion means the pathway by which technologies, previously unused by space flight pr... more Technology infusion means the pathway by which technologies, previously unused by space flight programs, move from their current status onto space flight missions. The technology can be several generations old, the state-of-the-art or anything that is deemed useful to the accomplishment of NASA space missions.
13th International Energy Conversion Engineering Conference, 2015
NASA's Radioisotope Power Systems (RPS) Program continues to plan and implement content to enable... more NASA's Radioisotope Power Systems (RPS) Program continues to plan and implement content to enable planetary exploration where such systems could be needed, and to prepare more advanced RPS technology for possible infusion into future power systems. The 2014-2015 period saw significant changes, and strong progress. Achievements of near-term objectives have enabled definition of a clear path forward in which payoffs from research investments and other sustaining efforts can be applied. The future implementation path is expected to yield a higherperforming thermoelectric generator design, a more isotope-fuel efficient system concept design, and a robust RPS infrastructure maintained effectively within both NASA and the Department of Energy. This paper describes recent work with an eye towards the future plans that result from these achievements.
Dynamic power conversion offers the potential to produce Radioisotope Power Systems (RPS) that ge... more Dynamic power conversion offers the potential to produce Radioisotope Power Systems (RPS) that generate higher power outputs and utilize the Pu-238 radioisotope more efficiently than Radioisotope Thermoelectric Generators. Additionally, dynamic systems offer the potential of producing generators with significantly reduced mechanical degradation over the course of deep space missions so that more power will be available at the end of the mission when it is needed for both powering the science and transmitting the results. The development of dynamic generators involves addressing technical issues not typically associated with traditional thermoelectric generators. Developing longlife, robust and reliable dynamic conversion technology is challenging yet essential to building a suitable generator. Considerations include working within existing handling infrastructure, where possible, so that development costs can be kept low and integrating dynamic generators into spacecraft, which may be more complex than integration of static systems. Methods of interfacing to and controlling a dynamic generator must also be considered and new potential failure modes must be taken into account. This paper will address some of the key issues of dynamic RPS design, development and adaption.
Given increasing complexity of many safety-critical systems, many organizations like NASA need to... more Given increasing complexity of many safety-critical systems, many organizations like NASA need to identify when, where, and how inappropriate perceptions of risk and anchoring of trust affect technology development and acceptance, primarily from the perspective of engineers and related management. Using the adoption of Dynamic Radioisotope Power Systems (RPS) for space exploration as a backdrop, we define and explain factors that contribute to inappropriate risk perception of various stakeholders. Three case studies (Mars Science Laboratory, Parker Solar Probe, and Titan Mare Explorer) demonstrate how NASA considered Dynamic RPS but decided against the new technology for less efficient alternatives of solar power and solid-state RPS. In the case of Dynamic RPS, increased design complexity that differs from previous successful solid-state power systems flown on the Voyager probes and Cassini spacecraft is one contributing factor, but not the only one. Problems with system performance and incorrect technology readiness labeling of Dynamic RPS technology led to an increased perception of distrust in Dynamic RPS for future missions. We also find that the perception of risk for Dynamic RPS future development is exacerbated by ongoing organizational challenges requiring multi-agency collaboration and coordination. Difficulties in setting realistic 5. MITIGATION STRATEGIES…………………8 6. CONCLUSION………………………………9 ACKNOWLEDGEMENTS………………………10 REFERENCES…………………………………10 BIOGRAPHY………………………………….14
The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and availabl... more The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or impossible to meet the needs of the missions. To meet this goal, the RPS Program, working closely with the Department of Energy, performs mission and system studies (such as the recently released Nuclear Power Assessment Study), assesses the readiness of promising technologies to infuse in future generators, assesses the sustainment of key RPS capabilities and knowledge, forecasts and tracks the Programs budgetary needs, and disseminates current information about RPS to the community of potential users. This process has been refined and used to determine the current content of the RPS Programs portfolio. This portfolio currently includes an effort to mature advanced thermoelectric technology for possible integration into an enhanced Multi-Mis...
Real-time sensor validation improves process monitoring and control system dependability by ensur... more Real-time sensor validation improves process monitoring and control system dependability by ensuring data integrity through automated detection of sensor data failures. The NASA Lewis Research Center, Expert Microsystems, and Intelligent Software Associates have developed an innovative sensor validation system that can automatically detect automated sensor failures in real-time for all types of mission-critical systems. This system consists of a sensor validation network development system and a real-time kernel. The network development system provides tools that enable systems engineers to automatically generate software that can be embedded within an application. The sensor validation methodology captured by these tools can be scaled to validate any number of sensors, and permits users to specify system sensitivity. The resulting software reliably detects all types of sensor data failures.
Introduction: For more than five decades, Radioisotope Power Systems (RPS) have played a critical... more Introduction: For more than five decades, Radioisotope Power Systems (RPS) have played a critical role in the exploration of space, enabling missions of scientific discovery to destinations across the solar system by providing electrical power to explore remote and challenging environments some of the hardest to reach, darkest, and coldest locations in the solar system. The recently reissued National Space Policy of the United States (June 2010) directs that “The United States shall develop and use space nuclear power systems where such systems safely enable or significantly enhance space exploration or operational capabilities”[1]. Moreover, the National Research Council report “Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration” (2009) by the Radioisotope Power Systems Committee illustrates how important RPS availability is for reaching the outer solar system where sunlight is very faint [2]. RPS could enable many deep space missions whe...
Radioisotope Thermoelectric Generators (RTGs) have been used to power NASA missions of various ty... more Radioisotope Thermoelectric Generators (RTGs) have been used to power NASA missions of various types throughout the past five decades. The most recent RTG iteration, used for NASA's Mars Science Laboratory, is the Multi-Mission RTG (MMRTG), which is currently the only spaceflight-qualified system available. The U.S. planetary science community has expressed a desire for more power system options to be available to accommodate a range of ambitious future mission concepts across the solar system. Recent advancements in thermoelectric (TE) materials technology have raised a potential for significantly increased efficiency in future RTGs, which helped spur a recent in-depth NASA study of options for future systems. A “next-generation” RTG study was conducted to develop new RTG concepts that could meet the needs of planetary science missions through the 2030s and beyond. A Next-Generation RTG would aim to extend the types of potential NASA missions able to be supported, while fulfilling requirements related to technical risk and schedule. In this study, 21 potential thermoelectric couple configurations were analyzed by considering various high-performance, high-temperature TE materials and segmentation techniques that maximize convertor efficiency and power density. System modularity was explored, and found to be a promising means to offer improved flexibility for NASA mission concepts with varying scope and power requirements. This paper presents the results of the study, demonstrating the viability of developing an updated RTG system design, and defining conceptual system approaches for a new, potentially revolutionary RTG.
The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to... more The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or impossible to meet potential future mission needs. To meet this goal, the RPS Program manages investments in RPS technologies and RPS system development, working closely with the Department of Energy. This paper provides an overview of the RPS Program content and status, its collaborations with potential RPS users, and the approach employed to maintain the readiness of RPS to support future NASA mission concepts.
15th International Energy Conversion Engineering Conference, Jul 7, 2017
The NASA Radioisotope Power Systems (RPS) Program's goal is to make RPS available for the explora... more The NASA Radioisotope Power Systems (RPS) Program's goal is to make RPS available for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible to use to meet mission needs. To meet this goal, the RPS Program manages investments in RPS system development and RPS technologies. The RPS Program exists to support NASA's Science Mission Directorate (SMD). The RPS Program provides strategic leadership for RPS, enables the availability of RPS for use by the planetary science community, successfully executes RPS flight projects and mission deployments, maintains a robust technology development portfolio, coordinates RPS related National Environmental Policy Act (NEPA) and Nuclear Launch Safety (NLS) approval processes for SMD, maintains insight into the Department of Energy (DOE) implementation of NASA funded RPS production infrastructure operations, including implementation of the NASA funded heat-source plutonium production restart efforts. This paper will provide a status of recent RPS activities and accomplishments.
35th Joint Propulsion Conference and Exhibit, 1999
Real-time validation of rocket engine sensor data improves mission safety and reduces flight oper... more Real-time validation of rocket engine sensor data improves mission safety and reduces flight operations and ground test costs. NASA Glenn Research Center, in partnership with Expert Microsystems, Inc., has developed an innovative sensor validation software application enabling real-time, automated sensor failure detection for all types of mission critical systems. This technology is broadly applicable to any aerospace or industrial control and safety system where: 0 Time-critical, closed-loop control or safety monitoring depend on sensor input; e Unexpected process interruptions due to sensor failures or false alarms are unsafe or uneconomical. Testing performed to date has verified that these sensor validation algorithms enable highly reliable real-time data validation for mission critical Space Shuttle Main Engine performance sensors, including the turbine discharge temperatures on both turbopumps. In this paper, we describe the current development status of the Sensor Validation System software and its application to the production of an on-line Space Shuttle Main Engine telemetry data monitoring system.
Radioisotope Power Systems (RPS) have been and will be enabling or significantly enhancing for ma... more Radioisotope Power Systems (RPS) have been and will be enabling or significantly enhancing for many missions, including several concepts identified in the 2011 Planetary Science Decadal Survey. Some mission planners and science investigators might have concerns about possible impacts from RPS-induced conditions upon the scientific capabilities of their mission concepts. To alleviate these concerns, this paper looks at existing and potential future RPS designs, and examines their potential radiation, thermal, vibration, electromagnetic interference (EMI), and magnetic fields impacts on representative science instruments and science measurements. Radiation impacts from RPS on science instruments are of potential concern for instruments with optical detectors and instruments with high-voltage electronics. The two main areas of concern are noise effects on the instrument measurements, and long-term effects of instrument damage. While RPS by their nature will contribute to total radiation dose, their addition for most missions should be relatively small. For example, the gamma dose rate from one Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) would be an order of magnitude lower than the environmental dose rate at Mars, and would have a correspondingly lower contribution to instrument noise and to any permanent damage to payload sensors. Increasing the number of General Purpose Heat Source (GPHS) modules used in an RPS would be expected to increase the generated radiation proportionally; however, the effect of more GPHS modules is mitigated from a strictly linear relationship by self-shielding effects. The radiation field of an RPS is anisotropic due to the deviation of the modules from a point-source-geometry. For particularly sensitive instruments, the total radiation dose could be mitigated with separation or application of spot shielding. Though a new, higher-power RPS could generate more heat per unit than current designs, thermal impact to the flight system could be mitigated with shading and pointing if required by the mission. Alternatively, excess heat could prove beneficial in providing needed heat to spacecraft components and instruments in some thermal environments. Vibration for a new higher-power Stirling Radioisotope Generator (SRG) would be expected to be similar to the recent Advanced Stirling Radioisotope Generator (ASRG) design. While vibration should be low, it must be considered and addressed during spacecraft and instrument design. EMI and magnetic fields for new RPS concepts are expected to be low as for the current RPS, but must be considered and addressed if the mission includes sensitive instruments such as magnetometers. The assessment conducted for this paper focused on orbiter instrument payloads for two representative mission concepts - a Titan Saturn System Mission (TSSM) and a Uranus Orbiter and Probe (UOP) - since both of these Decadal Survey concepts would include many diverse instruments on board. This paper describes how the potential impacts of the RPS on science instruments and measurements were assessed and which impacts were addressed. Then, this paper suggests mitigation strategies against those impacts, and provides an overview of several topics that would benefit from further work.
Technology infusion means the pathway by which technologies, previously unused by space flight pr... more Technology infusion means the pathway by which technologies, previously unused by space flight programs, move from their current status onto space flight missions. The technology can be several generations old, the state-of-the-art or anything that is deemed useful to the accomplishment of NASA space missions.
13th International Energy Conversion Engineering Conference, 2015
NASA's Radioisotope Power Systems (RPS) Program continues to plan and implement content to enable... more NASA's Radioisotope Power Systems (RPS) Program continues to plan and implement content to enable planetary exploration where such systems could be needed, and to prepare more advanced RPS technology for possible infusion into future power systems. The 2014-2015 period saw significant changes, and strong progress. Achievements of near-term objectives have enabled definition of a clear path forward in which payoffs from research investments and other sustaining efforts can be applied. The future implementation path is expected to yield a higherperforming thermoelectric generator design, a more isotope-fuel efficient system concept design, and a robust RPS infrastructure maintained effectively within both NASA and the Department of Energy. This paper describes recent work with an eye towards the future plans that result from these achievements.
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Papers by June Zakrajsek