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To save money, NASA management has shut down a troubled program to build a more efficient plutonium power supply for its deep space missions.
The cancelled ASRGs would have generated electrical power from the expansion of gas warmed by the radioactive decay of plutonium-238. NASA says that the devices have the same power output as its current generation of Multi-Mission Radioactive Thermoelectric Generators (MMRTG) but use four times less plutonium-238, a scarce resource. One MMRTG with 4.8 kilograms of plutonium is currently powering the Curiosity rover on Mars.
The United States has less than 40 kilograms of plutonium-238 left, but the DOE restarted production this year. Green says he is confident that the DOE will be producing plutonium-238 at a rate of 1.5 kilograms per year by 2019. He says that the stockpiled plutonium-238, along with the new supply, will be enough to send another planned rover to Mars in 2020 and to complete other missions in the 2020s – without any need for the extra efficiency of the ASRGs.
The ASRG program had been a year and a half behind schedule and had had its management team replaced at one point.