technologies with an eye toward future generations of RPSs, subsequent to the ASRG. This includes advanced thermoelectrics research, led by JPL with support from GRC, and thermophotovoltaics (TPV) research, led by GRC. The technology portfolio also includes funding for outside organizations through NASA Research Announcements.

  • The goal of advanced thermoelectric research is to develop thermoelectric materials that are much more efficient than traditional thermoelectric materials. Success in this area could ultimately lead to the development of an advanced thermoelectric converter, which could then be used in an advanced RTG.

  • A TPV RPS would be a relatively simple device that uses an array of photovoltaic material adjacent to a GPHS to generate electricity. The basic device (without the cooling fins) is not much larger than the GPHS itself. The converter efficiency is expected to be at least 15 percent, so that a TPV RPS powered by a single GPHS module would produce at least 38We at beginning of life.

PROGRAM BALANCE

Figure 4.1 shows the relative magnitude (in terms of NASA’s budget) of each element of the RPS program. Until 2007, the RPS program was a technology development effort. At that time, the focus shifted to development of a flight-ready ASRG, and that remains the current focus of the RPS program. The program received no additional funds to support this new tasking, so funding to develop a Brayton-cycle converter and a milliwatt-scale thermoelectric converter was eliminated. In addition, the budget for the remaining RPS technologies (advanced thermoelectrics and TPV) was cut. As a result, the development of new generations of RPSs that use these technologies has been delayed.

With the development of the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), the manufacture of GPHS RTGs was discontinued, and it would be very difficult

FIGURE 4.1 Relative magnitude of key elements of NASA’s radioisotope power system program. NOTE: Actual budget shown for fiscal year (FY) 2008 and 2009. Budget shown for FY 2010 to 2014 not yet enacted. ASC, Advanced Stirling Converter; ASRG, Advanced Stirling Radioisotope Generator; LAE, launch approval engineering. SOURCE: Modified from L.A. Dudzinski, NASA, “Radioisotope Power Systems. Power Systems Program. Historical Overview and Current Content,” presentation to the Radioisotope Power Systems Committee, September 18, 2008, Washington, D.C.

FIGURE 4.1 Relative magnitude of key elements of NASA’s radioisotope power system program. NOTE: Actual budget shown for fiscal year (FY) 2008 and 2009. Budget shown for FY 2010 to 2014 not yet enacted. ASC, Advanced Stirling Converter; ASRG, Advanced Stirling Radioisotope Generator; LAE, launch approval engineering. SOURCE: Modified from L.A. Dudzinski, NASA, “Radioisotope Power Systems. Power Systems Program. Historical Overview and Current Content,” presentation to the Radioisotope Power Systems Committee, September 18, 2008, Washington, D.C.



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