from the non-glowing-assessment dept.
A Government Accountability Office report has found that the U.S. is unlikely to produce enough Plutonium-238 for NASA missions about a decade from now. The isotope has been used in radioisotope thermoelectric generators (RTGs) on missions such as Voyager, Cassini, and the Mars Science Laboratory:
Another GAO report notes: "[...], DOE currently maintains about 35 kilograms (kg) [77 pounds] of Pu-238 isotope designated for NASA missions, about half of which meets power specifications for spaceflight. However, given NASA's current plans for solar system exploration, this supply could be exhausted within the next decade."
[...] To address the plutonium problem, in 2011 NASA provided funding to the Department of Energy (DOE) to restart domestic production of the substance. The program is called the Pu-238 Supply Project. So far, the Project has produced ∼3.5 ounces (100 grams) of Pu-238. DOE identified an interim goal of producing 10 to 17.5 ounces (300 to 500 grams) of new Pu-238 per year by 2019. The goal is to produce 1.5 kilograms of new Pu-238 per year—considered full production—by 2023, at the earliest.
GAO is questioning the Supply Project's ability to meet its goal of producing 1.5 kilograms of new Pu-238 per year by 2026. For one thing, the oversight agency's interviews with DOE officials revealed that the agency hasn't perfected the chemical processing required to extract new Pu-238 from irradiated targets to meet production goals.
Only one DOE reactor is currently qualified to make Pu-238:
NASA's plutonium will be produced at two of these reactors, but only one of them is currently qualified to make Pu-238. GAO reported that initial samples of the new Pu-238 did not meet spaceflight specifications because of impurities. However, according to DOE, the samples can be blended and used with existing Pu-238.
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Astronomers are still hoping for another mission to Pluto, or perhaps another Kuiper belt object:
A grassroots movement seeks to build momentum for a second NASA mission to the outer solar system, a generation after a similar effort helped give rise to the first one. That first mission, of course, was New Horizons, which in July 2015 performed the first-ever flyby of Pluto and is currently cruising toward a January 2019 close encounter with a small object known as 2014 MU69.
[...] Nearly three dozen scientists have drafted letters in support of a potential return mission to Pluto or to another destination in the Kuiper Belt, the ring of icy bodies beyond Neptune's orbit, Singer told Space.com. These letters have been sent to NASA planetary science chief Jim Green, as well as to the chairs of several committees that advise the agency, she added. "We need the community to realize that people are interested," Singer said. "We need the community to realize that there are important, unmet goals. And we need the community to realize that this should have a spot somewhere in the Decadal Survey." That would be the Planetary Science Decadal Survey, a report published by the National Academy of Sciences that lays out the nation's top exploration priorities for the coming decade.
New Horizons 2 was already cancelled due to a shortage of plutonium-238, which still reportedly persists. One proposed target was 47171 Lempo, a trinary system. The trans-Neptunian dwarf planets Eris, Haumea, Sedna, Orcus, Salacia, Makemake, and 2007 OR10 (the largest known body in the solar system without a name - with an estimated 1,535 km diameter) have all been discovered since 2002. Several of these TNOs have moons and Haumea was recently found to have a ring system.
Now that Cassini is dead, most new NASA missions are focused on Mars and Jupiter, leaving the solar system's "ice giants" relatively unstudied: