Enhanced Multi-Mission Radioisotope Thermoelectric Generator (eMMRTG) Concept

Illustration of radioisotope thermoelectric generator.
Illustration of radioisotope thermoelectric generator.

The conceptual eMMRTG would preserve all MMRTG envelope, volume, interfaces and mounting points while offering significant increases in power:

Chart showing transition from MMRTG to eMMRTG
Concept: Direct retrofit of TE couple technology into proven MMRTG
  • > 25% at beginning of life (BOL)
  • > 50% at end of 14-year mission (EOM)
  • Multi-mission capability (vacuum and Mars atmosphere) preserved

The eMMRTG would retrofit the MMRTG with new thermo- electric (TE) couples:

  • Substitution of current MMRTG PbTe/TAGS couples with skutterudite (SKD) couples
    • Technology developed with NASA support at the Jet Propulsion Laboratory over the last 20 years
    • Key industry partners include Teledyne Energy Systems and Aerojet/Rocketdyne
  • Addition of a surface oxidation layer to the heat source liner

Stirling Converter Technology

Stirling Converters are a high efficiency engine which converts heat into electricity.

Inside a Stirling converter, a moving piston is driven by the heat of a fuel source. The piston would move a magnet back and forth through a coil of wire to generate electrical current in the wire. To prevent physical wear, the piston is suspended in a helium gas bearing, meaning it does not actually touch the inside of the mechanism.

Because the process used to convert heat energy into electricity, known as the Stirling cycle, is more efficient than the thermoelectric and solar powered systems, generators using Stirling technology could provide a more efficient means of producing power for spacecraft than existing power systems.

NASA had planned to complete development of two Advanced Stirling Radioistope Genertor (ASRG) units for flight by 2016, but chose to discontinue development of a system in late 2013. NASA's Glenn Research Center will continue development and testing of Stirling technology for potential use by future space exploration missions.

This 3D animation shows the main components of the Advance Stirling Radioisotope Generator—a different type of radioisotope generator that was previously considered by NASA to provide power for some missions that explore the solar system.

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