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ARCHIVAL CONTENT: Advanced Stirling Radioisotope Generator (ASRG)

An ASRG produces electricity by a triple energy transformation: it first turns the thermal energy from the hot radioisotope fuel into the high-speed kinetic motion of a small piston and its companion displacer.
Development of ASRG flight units was cancelled in late 2013.
Credit
NASA/U.S. Department of Energy