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NASA sometimes conducts robotic science missions to solar system destinations for which the most appropriate power source is derived from thermal-to-electrical energy conversion of nuclear decay of radioactive isotopes. Typically the use of a radioisotope power system (RPS) has been limited to medium and large-scale missions, with 26 U,S, missions having used radioisotope power since 19' 61. A research portfolio of ten selected technologies selected in 2003 has progressed to a point of maturity, such that one particular technology may he considered for future mission use: the Advanced Stirling Converter. The Advanced Stirling Radioisotope Generator is a new power system in development based on this Stirling cycle dynamic power conversion technology. This system may be made available for smaller, Discovery-class NASA science missions. To assess possible uses of this new capability, NASA solicited and funded nine study teams to investigate unique opportunities for exploration of potential destinations for small Discovery-class missions. The influence of the results of these studies and the ongoing development of the Advanced Stirling Radioisotope Generator system are discussed in the context of an integrated Radioisotope Power System program. Discussion of other and future technology investments and program opportunities are provided.I. Introduction Solar system exploration is a mainstay of the scientific program of robotic spacecraft missions conducted by NASA. To enable certain missions, power must be generated without the use of conventional photovoltaic methods. Use of radioisotope power systems has been finnl y established since 1961 as a means to fulfill the need for such power among a variety of missions. Twenty-six missions have taken advantage of the investments of radioisotope power systems development to allow scientific exploration of destinations such as the moon, Mars, Jupiter, Saturn, and Pluto. Because of the longevity of radioisotope power systems, some of these missions have even continued to perform extended mission operations beyond the farthest reaches of the solar system.The contemporary method of energy conversion for flight radioisotope power uses the Seebeck effect, in a thennoelectric (TE) energy conversion process. This method was first used in flight in 1961 , and continues today as the means to power the Mars Science Lab rover. MSL uses the Multi-Mission Radioisotope Thennoelectric Generator (MMRTG), and is scheduled for launch in 2011. Thennoelectric energy conversion technology investments over the years have yielded more robust components that have a longer life. IE power systems have now been seen to demonstrate over 30 years of spaceflight operation on the two Voyager spacecraft, for example. While thermoelectric technology is well proven. it also has fairly poor conversion efficiency.Investments seeking alternative energy conversion methods have been made over the years at both NASA and DOE. Most recently, NASA invested in a radioisotope power conversion technology program. A gas...

NASA's Radioisotope Power Systems (RPS) Program began formal implementation in December 2010. The RPS Program's goal is to make available RPS for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible to meet mission needs. To meet this goal, the RPS Program manages investments in RPS system development and RPS technologies. The current keystone of the RPS Program is the development of the Advanced Stirling Radioisotope Generator (ASRG). This generator will be about four times more efficient than the more traditional thermoelectric generators, while providing a similar amount of power. This paper provides the status of the RPS Program and its related projects. Opportunities for RPS generator development and targeted research into RPS component performance enhancements, as well as constraints dealing with the supply of radioisotope fuel, are also discussed in the context of the next ten years of planetary science mission plans.

NASA's Radioisotope Power Systems (RPS) Program began formal implementation in December 2010. The RPS Program's goal is to make available RPS for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible to meet mission needs. To meet this goal, the RPS Program manages investments in RPS system development and RPS technologies. The current keystone of the RPS Program is the development of the Advanced Stirling Radioisotope Generator (ASRG). This generator will be about four times more efficient than the more traditional thermoelectric generators, while providing a similar amount of power. This paper provides the status of the RPS Program and its related projects. Opportunities for RPS generator development and targeted research into RPS component performance enhancements, as well as constraints dealing with the supply of radioisotope fuel, are also discussed in the context of the next ten years of planetary science mission plans.

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.