The Mars Science Laboratory, carrying the SUV sized Curiosity Mars rover, is due to lift off from the Kennedy Space Center this Saturday. One of the features of the newest Mars rover is the Radioisotope Thermoelectric Generator that powers it.
While many space probes use solar panels to power them, some use RTGs, which use the decay of plutonium 238 to provide heat and power. RTGs are used when the probe in question is slated to explore far away from the sun, such as the Outer Planets, or, as in the case of the MSL, the probe is large enough to need to power generated by the RTG.
While there has been some controversy surrounding the safety of launching space craft with RTGs, the only serious contamination occurred when a Russian probe crashed in the Canadian wilderness in 1978, spreading radioactive fuel over the landscape.
RTGs have provided power for space missions since the Apollo program. Some examples include:
Apollo Lunar Surface Experiment Package
Apollo Lunar Surface Experiment Package was an instrument package placed on the lunar surface by the crews of Apollo 12, 14, 15, 16, and 17. The instruments measured seismic activity on the lunar surface, as well as other phenomenon such as solar wind and magnetic activity. The ALSEPs were powered by a single RTG that generated 70 watts of power.
Galileo
Galileo, which was launched in October 1989, orbited Jupiter from 1995 to 2003, exploring the largest planet in the solar system and its various moons. Galileo was powered by two GPHS-RTGs that carried just over 17 pound of plutonium. The RTGs provided 570 watts of power at launch, which had decreased to 493 watts when it had arrived at Jupiter.
Ulysses
Ulysses, launched in October 1990, orbited the sun, studying its properties between 1994 and 2009, when communications was lost with the vehicle. The RTG power source on the vehicle generated about 285 watts.
Cassini
Cassini, currently orbiting Saturn, was launched in 1997 and arrived at Saturn in 2004. Cassini is powered by three RTGs, contained 72 pounds of plutonium. The RTGs provide 600 to 700 watts of power.
New Horizons
New Horizons was launched in January 2006, with a planned flyby of Pluto in 2015. The single RTG, which was actually a spare from the Cassini mission, contained 24 pounds of plutonium. It generated 240 watts at launch, but will put out 200 watts by the time it encounters Pluto.
Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals, including The Houston Chronicle, The Washington Post, USA Today, the L.A. Times and The Weekly Standard.
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