NASA received permission to use RTG with plutonium-238 in another mission

Plutonium-238 in the iridium granule glows red and generates a large amount of heat for decades. These pellets are installed in radioisotope thermoelectric generators (RTGs) that generate electricity.
NASA Director of Planetology, James Green, sent out a memo regarding radioisotope heat generators (RTGs).

“After analyzing and consulting with the Department of Energy, the NASA Planetology Division is pleased to announce the lifting of the ban on the use of Radioisotope Power Systems (RPS) by applicants who intend to participate in the upcoming Discovery program,” the memo said.

After obtaining permission, applicants may include in their tenders up to two radioisotope heat generators, and thus significantly expand the concept of Discovery missions.

Discovery is a program of relatively low-budget highly specialized space missions for the scientific study of the solar system. "Low budget" compared to the missions of the New Frontiers or Flagship programs, of course. In absolute terms, their budget is quite decent. The Discovery program prepared missions for NEAR Shoemaker (the very first mission in 1996 to study the asteroid 433 Eros), Mars Pathfinder (the lander that delivered the planet rover Sojourner to Mars), Stardust, Deep Impact, Dawn, Kepler and many others.

Back in December The “long-term planning information” for the Discovery program was reported to be prohibited from installing RPS radioisotope sources. Only radioisotope heaters (RHUs) with a very small amount of plutonium-238 were allowed to heat scientific instruments and other elements of the spacecraft. Now the restriction has been removed.

The full-scale use of plutonium-238 was made possible by assessing the projected reserves of this fuel based on consumption in future missions such as Mars 2020, Space News reports. . Dragonfly, one of two finalists of the middle-class planetary scientific mission under the New Frontiers program, and future devices that will have to work on the lunar surface during a two-week moonlit night, when the soil freezes to −170 ° C, claim to be its rare material.

Plutonium-238 is still in very large short supply. Only around 2022 the Ministry of Energy will reach a production volume of about 1.5 kg per year, and until that time it is necessary to severely limit the consumption of isotope. With austerity, James Green explained why they initially banned the use of radioisotope sources of energy for the mission: “The last thing we would like to encounter is to choose a mission and then not be ready to fly.”

After the publication of “long-term planning information”, Green returned to the Department of Energy again to recalculate current and forecasted plutonium-238 reserves. Such perseverance brought success: in the end, the numbers converged in the right way - and it turned out that the fuel would really be enough for another mission.

A more optimistic forecast for plutonium reserves appeared due to the progress that the US Department of Energy made in the extraction of this valuable isotope. Apparently, American nuclear physicists will be able to reach a volume of 1.5 kilograms per year at the scheduled time.

Plutonium-238 production in the United States was halted in the late 1980s, and production is now recovering at a slow pace. Since 1992, plutonium-238 was purchased from Russia, but in 2009 the deal fell through, which put the United States in a difficult position . At the beginning of 2015, 35 kg of plutonium remained in the reserves, of which only 17 kg corresponded to the required quality for creating power sources for spacecraft, which roughly corresponds to the three atomic elements installed in the Curiosity rover.

The Oak Ridge National Laboratory produced the first plutonium-238 in the last 30 years by December 2015, and now the United States is gradually recovering the isotope that is needed for space missions. Plutonium-238 is obtained from neptunium-237, which is extracted from the fuel of nuclear reactors.

But because of such a trifle, the USA could lose its world leadership in space research, because without plutonium-238 there is nothing to do in deep space: “It will not be a great exaggeration to say that the future of the undisputed leadership of the USA in the field of planetary research in the 21st century depends on plutonium -238, said then in an interview with the online newspaper, Alan Stern, the head of the New Horizon mission. - We can still undertake one research mission after Curiosity, but that’s all. Some kind of madness. Irresponsible to come so close to the edge of the abyss. We need to contact the Russians to get to the orbital station, we can no longer explore the moon like in the days when I was a boy, and now we also lose the ability to explore the solar system to its very borders. "

But now the situation is close to a successful resolution. The Department of Energy has managed to scale production - and soon, NASA will receive plutonium-238 in the required quantity.