Nuclear power in space

Nuclear power in space is the use of nuclear power in outer space, typically either small fission systems or radioactive decay for electricity or heat. Another use is for scientific observation, as in a Mössbauer spectrometer. One common type is a radioisotope thermoelectric generator, which has been used on many space probes and on manned lunar missions, and another is small fission reactors for Earth observation satellites such as the TOPAZ nuclear reactor. A radioisotope heater unit provides heat from radioactive decay of a material and can potentially produce heat for decades.

Russia has sent about 40 reactors into space and its TOPAZ-II reactor can produce 10 kilowatts. The Romashka reactor family uses uranium and direct thermoelectric conversion to electricity, rather than using a heated fluid to drive a turbine. The United States tested a nuclear reactor in space for 43 days in 1965. While not yet tested in space, the test of the Demonstration Using Flattop Fission (DUFF) on September 13, 2012 was the first test of a nuclear reactor power system for space since then.

Examples of nuclear power for space propulsion systems include nuclear electric rocket (nuclear electric propulsion), radioisotope rocket, and radioisotope electric propulsion (REP). One of the more explored is the nuclear thermal rocket, which was tested in the NERVA program. See also Category:Nuclear spacecraft propulsion (category link). Nuclear pulse propulsion was the subject of Project Orion (nuclear propulsion)

While solar power is much more commonly used, nuclear power offers great advantages in many areas. Solar cells, although efficient, can only supply energy to spacecraft in orbits where the solar flux is sufficiently high, such as low Earth orbit and interplanetary destinations close enough to the Sun. Unlike solar cells, nuclear power systems function independently of sunlight, which is necessary for deep space exploration. Nuclear reactors are especially beneficial in space because of their lower weight-to-capacity ratio than solar cells. Therefore, nuclear power systems take up much less space than solar power systems. Compact spacecraft are easier to orient and direct in space when precision is needed. Estimates of nuclear power, which can power both life support and propulsion systems, suggest that use of these systems can effectively reduce both cost and flight time.

...
Wikipedia