Did you know that nuclear technology has been used in space almost since the beginning of human exploration in space?  That’s right – nuclear energy has been used to power science experiments, satellites, and space probes.  It may even be used someday to propel vessels with people on board to other planets.  Let’s take a look at three basic kinds of nuclear space technology!
This kind of space power has a long name; Radioisotopic Thermal Generator.  This really just means that radioactive materials, which get hot when they decay, are used to generate electricity directly using something called the “thermoelectric effect.”  This effect is simply the generation of voltage when two different kinds of wires are connected to each other and heated up.  The power produced isn’t much, but it can be produced reliably for a fairly long time.  That’s why this source is good for very long flights – like that of the Pioneer probes that photographed Jupiter in the 1970’s.
The Apollo moon landing missions from Apollo 12 on carried a small SNAP-27 nuclear electric generator to power the science stations that were left on the moon. These stations contained various sensors which radioed data back to scientists on the earth. The little SNAP-27 generators, one of which is seen here in the right foreground, provided about 60 watts of power and were expected to last about five years. All of the science stations, known as “ALSEP” (Apollo Lunar Surface Experiment Package) were turned off from Earth in 1977 after the end of the Apollo program.
RTG devices have been used on satellites orbiting the Earth too. Here we see a weather satellite, used to photograph clouds and storm structures such as hurricanes. This satellite, called Nimbus-B, had solar panels for its main power but also had two 30-watt SNAP-19 nuclear

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