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NASA has released a long-awaited Nuclear Power Assessment Study that examines the prospects for the use of nuclear power in civilian space missions over the next 20 years.
The Study concludes that there is a continuing demand for radioisotope power systems, which have been used in deep space exploration for decades, but that there is no imminent requirement for a new fission reactor program.
The 177-page Study, prepared for NASA by Johns Hopkins University Applied Physics Laboratory, had been completed several months ago but was withheld from public release due to unspecified "security concerns," according to Space News. Those concerns may have involved the discussion of the proposed use of highly enriched uranium as fuel for a space reactor, or the handling of plutonium-238 for radioisotope power sources.
"The United States has spent billions of dollars on space reactor programs, which have resulted in only one flight of an FPS [fission power source]," the new NASA report noted. That was the 1965 launch of the SNAP 10-A reactor on the SNAPSHOT mission. It had an electrical failure after a month's operation and "it remains in a 1300-km altitude, 'nuclear-safe' orbit, although debris-shedding events of some level may have occurred," the report said.
In any case, specific presidential approval is required for the launch of a nuclear power source into space, pursuant to Presidential Directive 25 of 1977.
Original Submission
(Score: 2, Informative) by khallow on Friday June 05 2015, @12:50PM
I don't know enough about physics or engineering and I can't see anything easily mentioned in the linked report. What would happen in a Challenger/Columbia type event -- catastrophic failure and disintegration upon exit or re-entry? Would that be like setting of a nuke in the atmosphere? Which sounds kinda bad.
As I understand it, there are three things a RTG capsule would have to withstand. First, the forces tearing apart a rocket in flight. This isn't actually that hard to survive. Then there's the thermal input from being for a short time in the middle of a fireball, possibly combined with some heating from reentry into the atmosphere. The latter can be difficult, if the vehicle was almost to orbital velocities when it failed. Finally, there's the impact from hitting ground or water. They have RTGs that are thought to survive all that without releasing their plutonium cargo.
The plutonium (or other radioisotope component) is subcritical (well below what it would need for a self-sustaining cascading fission reaction( with a well known and nearly fixed heat output. It won't blow up or melt down.