The agency will be considering mission concepts that can carry an Advanced Stirling Radioisotope Generator (ASRG).

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The suggestion is to use similar radioisotope thermoelectric generators like the one found in the Curiosity rover.

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As the radioisotope decays, it produces heat energy that is converted by thermoelectric materials into the electricity that powers the space probe.

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Finally, a 1 kW electric radioisotope power supply running on Plutonium 238 (Pu-238) would kick in to power an ion thruster engine.

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Instead, NASA imbeds a nuclear material in a radioisotope thermal generator.

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This is a plutonium-driven device that produces power far more efficiently than the traditional Radioisotope Thermoelectric Generators (RTGs) used hitherto on space missions, such as on Cassini.

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It also likes companies that are working on making smaller batteries, like Qynergy, a New Mexico-based company working on radioisotope batteries, and Infinite Power Solutions, a Colorado developer of thin-film batteries that can power RFID (Radio Frequency Identification) tracking chips.

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Although solar panels will work on spacecraft at that distance, the desire for sufficient energy to drive many instruments means any mission would really need to go with radioisotope thermal generators (RTGs) - solid state electrical generators powered by the heat of radioactive decay.

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