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NASA Pulls the Plug on Plutonium Power Source

Jim Green. Credit: NASA photo

NASA has cancelled work on a troubled radioisotope power system intended to help the next generation of spacecraft reach the planets, moons and comets of the outer Solar System.

In a blog posted [editor's note: see below] on November 15, NASA’s planetary science division director Jim Green said that NASA is ending work on two Advanced Stirling Radioisotope Generators (ASRG) being built by the US Department of Energy (DOE).

“Our decision is based purely on budgetary constraints,” Green tells Nature. The move will save NASA $170 million over three years; the planetary science budget was cut by $300 million to $1.2 billion in fiscal year 2013. 

Jim Green's Nov. 15 blog post:

Important Changes in the NASA Planetary Science Division’s  (PSD) Radioisotope Program

James Green, Director, Planetary Science Division NASA

For the last several years PSD has been investing in Advanced Stirling Radioisotope Generator (ASRG) technology with the intent to fabricate flight units for deep space missions. The advanced Stirling technology was selected to take advantage of its increased efficiency over the Multi-Mission Radioisotope Thermal Generator (MMRTG), since the supply of Plutonium-238 (Pu-238) was limited at the time.   Now, with the restart of the Pu-238 production project this year, we expect to have a sufficient supply of Pu-238 for radioisotope power well into the future.

With an adequate supply of Pu-238, and considering the current budget-constrained environment, NASA has decided to discontinue procurement of ASRG flight hardware.  We have given direction to the Department of Energy, which manages the flight procurement, to end work on the flight units.  The hardware procured under this activity will be transferred to the Glenn Research Center to continue development and testing of the Stirling technology.

For future planetary missions that require radioisotope power systems the flight-proven MMRTG will be made available.  It is important to note that the MMRTG and the ASRG were designed to provide the approximately the same electrical power output.    

I am happy to discuss this decision at all the upcoming Assessment Group meetings and at the American Geophysical Union meeting next month where I will address any questions that you may have. 



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