Wednesday, October 6, 2010

Nuclear fission in space

"SNAP-10A was launched from Vandenberg AFB by an ATLAS Agena D rocket on April 3, 1965 into low Earth orbit. Its nuclear electrical source, made up of thermoelectric elements, was intended to produce over 500 watts of electrical power for one year. After 43 days, an onboard voltage regulator within the spacecraft—unrelated to the SNAP reactor itself—failed, causing the reactor core to be shut down. The reactor was left in a 700-nautical-mile (1,300 km) earth orbit for an expected duration of 4,000 years.

An anomalous event in November 1979 caused the vehicle to begin shedding an eventual 50 pieces. A collision has not been ruled out and radioactives may have been released."

A long lasting nuclear reactor will prove essential for missions like JIMO, that use powerful radars or Ion drives past the range of good solar energy (around Mars or so.) Reactors of these kinds will supplement RTGs when more power is needed, but are unlikely to replace RTGs totally for all missions designs. Some probes may need a combination of both technologies.


"Safe Affordable Fission Engine (SAFE) are NASA's small experimental nuclear fission reactors for electricity production in space. Most known is the SAFE-400 reactor producing 400 kW thermal power, giving 100 kW of electric energy using a Brayton cycle gas turbine. The fuel is uranium nitride in a core of 381 pins clad with rhenium. Three fuel pins surround a molybdenum-sodium heatpipe that transports the heat to a heatpipe-gas heat exchanger. This is called a Heatpipe Power System. The reactor is about 50 centimetres (20 in) tall, 30 centimetres (12 in) across and weighs about 1,200 kilograms (2,600 lb). It was developed at the Los Alamos National Laboratory and the Marshall Space Flight Center under the lead of Dave Poston. A smaller reactor called SAFE-30 was made first."


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