RECOMMENDATION. Flight Readiness. The RPS program and mission planners should jointly develop a set of flight-readiness requirements for RPSs in general and Advanced Stirling Radioisotope Generators in particular, as well as a plan and a timetable for meeting the requirements.

RECOMMENDATION. Technology Plan. NASA should develop and implement a comprehensive RPS technology plan that meets NASA’s mission requirements for RPSs while minimizing NASA’s demand for 238Pu. This plan should include, for example:

  • A prioritized set of program goals.

  • A prioritized list of technologies.

  • A list of critical facilities and skills.

  • A plan for documenting and archiving the knowledge base.

  • A plan for maturing technology in key areas, such as reliability, power, power degradation, electrical interfaces between the RPS and the spacecraft, thermal interfaces, and verification and validation.

  • A plan for assessing and mitigating technical and schedule risk.

HIGH-PRIORITY RECOMMENDATION. ASRG Development. NASA and the Department of Energy should complete the development of the Advanced Stirling Radioisotope Generator (ASRG) with all deliberate speed, with the goal of demonstrating that ASRGs are a viable option for the Outer Planets Flagship 1 mission. As part of this effort, NASA and the Department of Energy should put final design ASRGs on life test as soon as possible (to demonstrate reliability on the ground) and pursue an early opportunity for operating an ASRG in space (e.g., on Discovery 12).


JPL (Jet Propulsion Laboratory). 2009. Outer Planets Flagship Mission. Available at

Mankins, J.C. Advanced Concepts Office, Office of Space Access and Technology, NASA, Technology Readiness Levels, A White Paper, April 6, 1995.

NASA (National Aeronautics and Space Administration). 2009. NASA and ESA Prioritize Outer Planet Missions. Available at

NEPA (National Environmental Policy Act). 1970. National Environmental Policy Act of 1969, as amended, 42 USC Sections 4321-4347. Available at

Ross, R.G., Jr. 2008. Cryogenic Cooling in Space: 50-years of Lessons Learned. Second meeting of the Radioisotope Power Systems Committee, Pasadena, Calif., October 28.

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