The shortage of plutonium threatens NASA's future mission to explore deep space, the US government has warned.

The break in production of plutonium 238 (Pu-238) between 1988 and 2015 could result in a bottleneck situation where there is not enough of this scarce resource to power spacecraft during long-duration missions, reported this week citing a government report.

NASA has long used radioisotope power systems (RPS) to generate reliable electrical power and heat energy for long-duration space missions, the US Government Accountability Office (GAO) report said.

But given NASA's current plans for solar system exploration, the supply of this critical resource could be exhausted within the next decade, putting in jeopardy its future missions that would require this fuel, it warned.

RPS can operate where solar panels or batteries would be ineffective or impossible to use, such as in deep space or in shadowed craters, by converting heat from the natural radioactive decay of plutonium-238 (Pu-238) into electricity.

Missions such as the Mars Curiousity rover and the Voyager 1 and 2 spacecraft use radioisotope thermoelectric generators as power source.

Planetary orbiter
[Representational image]Creative Commons

The production problems of Pu-238 and subsequent risks to NASA have been known for several years.

The US Department of Energy (DOE) and its predecessor agencies have been providing Pu-238 and fabricating RPS for NASA and other federal agencies for more than five decades decades

DOE currently maintains about 35 kgs of Pu-238 isotope designated for NASA missions, about half of which currently meets the power specifications for spaceflight.

However, given NASA's current plans for solar system exploration, this supply could be exhausted within the next 10 years.

Specifically, NASA plans to use about 3.5 kg of Pu-238 isotope for one RPS to power the Mars 2020 mission, the Government Accountability Office report said.

NASA may also use an additional 10.5 kg of Pu-238 isotope for its New Frontiers #4
mission if three RPS are used.

If DOE's existing Pu-238 supply is used for these two missions, NASA would be forced to eliminate or delay future missions requiring RPS until DOE produces or acquires more Pu-238, the report said.