Tucked away in U.S. President BarackObama’s 2010 budget request for the U.S. Department of Energy was a piece of good news for NASA and deep space exploration: $30 million to lay the groundwork for resuming production of plutonium-238, the nuclear fuel that has been used to power deep space probes from Voyagers 1 and 2, launched in 1977 and now venturing beyond the solar system, to the Pluto-bound New Horizons craft, launched in 2006.
Plutonium-238, or pu-238, is the central ingredient of radioisotope power systems, which convert heat from radioactive decay into electrical energy to power spacecraft that venture too far from the sun to effectively tap its energy with solar arrays. The
, in a shortsighted decision, shut down production of the material in the late 1980s, opting to rely instead on Russian stockpiles for the occasional NASA mission that required nuclear fuel.
‘s stockpile has dwindled, however, and NASA has found itself in competition for the remaining
supplies with unspecified national security customers.
The National Research Council warned in May that NASA’s Mars Science Laboratory, a golf-cart sized rover slated for launch in 2011, and a flagship-class mission to Jupiter targeted for launch around the end of the next decade, stand to consume the last of the pu-238 currently available to the space agency.
Without pu-238, NASA faces a future with no means to conduct meaningful exploration of planets or asteroids beyond Mars, the report said. This would be highly unfortunate: some of the most intriguing objects in the solar system – the moons of Jupiter and Saturn, for example – are inaccessible by anything other than nuclear-powered spacecraft.
The problem isn’t just NASA’s:
, for example, has ambitions for deep space exploration but no independent means of producing radioisotope power sources.
Previous administrations had delayed action on resuming pu-238 production for so long that, in the words of the National Research Council, “the day of reckoning has come.”
With no time left to lose, the Obama administration acted. The funding request for pu-238 production, if approved by Congress, will start a process that according to the National Research Council will cost at least $150 million and take eight years, meaning production would resume about the time the planned mission to Jupiter begins its journey.
The use of highly toxic pu-238 on space probes has generated controversy in some circles, despite studies showing that the odds of contamination resulting from a launch or re-entry accident are infinitesimal. The administration’s request should not be controversial; Congress should not make an issue of it in marking up the Energy Department’s funding bill.
NASA and the Energy Department, meanwhile, should continue development of new radioisotope power systems that use pu-238 more efficiently than current-generation nuclear batteries. Once proven, such systems would help ease the impact of any future interruptions or hiccups in pu-238 production while enabling NASA and its international partners to do more with less in deep space.