When will NASA finally use a nuclear reactor?

NASA has in the past developed and flight certified a nuclear reactor called (Systems for Nuclear, Auxiliary Power) SNAP-10a. This small space reactor was flown in 1965 and operated for 43 days when a non-reactor electrical component (power supply regulator) failed which led to the termination of the satellite’s mission. SNAP-10a was intended to produce over 500 watts of electrical power for one year.

Picture of 500 watt SNAP-10a space reactor prior to launch

In 2012 LANL National Lab designed and built a small 24 W space nuclear reactor called DUFF for NASA in less than six months at a total project cost of less than $1 million dollars. This was only a demonstration reactors and did not become flight certified (that would be a longer process) but the small DUFF reactor included some really novel, untried technology like use of heat pipes to remove heat from the reactor core – something never previously demonstrated. DUFF used sterling engine power conversion technology to turn nuclear heat into electricity. LANL reviewed for safety and then built the prototype reactor in a span of 6 months. The same reactor design group at LANL has received funding to design and build another somewhat larger, but still fairly small, space reactor called KRUSTY that is intended to produce kilowatt levels of power output. KRUSTY has been designed and physically constructed at LANL and is now being field tested and operated at the Nevada Nuclear Security Site. Testing of this larger kilowatt power space reactor is expected to be complete in January of 2018.

Picture of the KRUSTY space reactor currently under test

Some people worry about the safety and wisdom of launching small space reactors into space on rockets that have a operational record of failing n out of 100 times. It should be remembered that small space reactors have a very low radiological inventory at launch — less than 5 curies total in the uranium-zirconium-hydride fuel — so space reactors are actually fairly benign … There are no highly radioactive fission products inside a small space reactor until such time as it goes critical on command from earth. It is only once the space reactor goes critical that there will be some moderate level of radiation generated inside the reactor.

[1] – LANL DUFF Space Reactor – Interplanetary mission fission

[2] LANL Kilowatt Reactor Using Stirling Technology KRUSTY – Nuclear and Stirling engines spur space exploration

I can’t say when it will be used, but NASA is in fact developing a 40kw “Small Fission Power System.”

Instead of Pu238 and themocouples like traditional RTGs, this is a true, if simple, fission reactor that generates power using a Stirling engine.

Unlike traditional RTGs, which could never be buried as shown in The Martian, the SFPS is buried, but its radiator remains above ground.

It can also be used in space to power long duration plasma drives.

A nuclear reactor is necessarily heavy (the special nuclear material used for fuel is heavy). Then, all a nuclear reactor does is make heat. To generate thrust, some gas or liquid would need to be heated, so the rocket would still have to carry this fuel. Simply put, there are far more efficient ways to generate thrust than a nuclear reactor. Then there is the concern that if the rocket blows up, the nuclear fuel would spread radioactive contamination over a wide area. As I said, there are better way to get a rocket into space.

Right now the only kinds of missions where a nuclear reactor (not a nuclear rocket, that’s a different story) are long duration missions in places where either the sun is too weak (beyond jupiter) or there is no sun (under europan ice) or where the night is too long (luna). And lots of power is needed even without sun. Usually but not always this means manned missions

You need to troll for the guys who work at Plumbrook (near what’s now called Glenn in Cleveland, OH). Or try looking for web sites.