NASA's Mars 2020 rover has received its nuclear power plant developed by Aerojet Rocketdyne and Teledyne. The Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) unit will provide the robotic spacecraft with 125 W of electricity to operate the drive motors and power the onboard systems, as well as provide heat to keep the electronics warm during the sub-arctic Martian nights.

Currently undergoing final testing and assembly at NASA's Kennedy Space Center in the runup to its July 2020 launch, the Mars 2020 rover is an updated version of the space agency's highly successful Curiosity rover. Like Curiosity, Mars 2020 is a six-wheeled autonomous robot about the size of a 4X4 and its primary mission will be to seek out areas that may once have been habitable and collect soil and rock samples for analysis or stored for recovery and return to Earth by a future mission.

The MMRTG is a key component of this mission. It's not a nuclear reactor, but more of a nuclear battery similar to those first used by NASA in 1962 and a direct descendant of the ones used on the Viking, Pioneer, Voyager, and New Horizons missions. Instead of using a full-blown nuclear reaction, the MMRTG uses plugs of plutonium 238-dioxide fused into a ceramic and sealed in a special armored container for safety during launch from Earth.

Once activated, the plutonium naturally undergoes radioactive decay and heats up. Thermocouples inside the generator convert this heat into electricity and the excess heat is used to either warm the rover or is dumped using radiators. With a service life of at least 14 years, the MMRTG makes the rover independent of outside power sources like sunlight – making it highly resistant to cold and Martian dust storms like the one that is currently keeping the solar-powered Opportunity rover in hibernation.

According to Rocketdyne, the MMRTG was delivered to the US Department of Energy's (DOE) Idaho National Laboratory (INL) for installation of the plutonium fuel. It will then be sent on to the Kennedy Space Center to be integrated into the Mars 2020 rover. The company is contracted to build an additional generator, though this has not been assigned to any mission yet.

"We're best known for propulsion, but our role in supporting space programs certainly does not end there," says Eileen Drake, Aerojet Rocketdyne CEO and president. "We've built lithium-ion batteries for the International Space Station, provide nuclear generators for deep space missions like the Mars rovers, and are building the electrical power system for Sierra Nevada's Dream Chaser."

The video below shows the interior design of the MMRTG.

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