The Mars Science Lab, with its Curiosity rover, is powered by a Radioisotope Thermoelectric Generator that uses decaying plutonium 238 to provide power and heat. A shortage of the nuclear fuel may mean that the MSL will be one of the last of its kind.
What are radioisotope thermoelectric generators?
Radioisotope thermoelectric generator or RTGs use the heat generated by decaying plutonium 238 to provide heat and electricity. The RTGs use electronic parts to convert the heat into electricity. The RTGs have been called "nuclear batteries" and have been used in a variety of NASA space craft since the Apollo program. The space craft include the two Voyagers, Galileo, Ulysses, Cassini, Pluto New Horizons, and now the Mars Science Lab.
Why use RTGs instead of solar panels?
Solar panels generate only a limited amount of electricity as compared to RTGs. For missions that voyage far from the sun, such as to the Outer Planets, and/or are large and complex, such as the Mars Science Lab, RTGs are perfectly suited.
Why are RTGs considered controversial?
Some environmental and anti-nuclear groups oppose the use of RTGs for safety and ideological reasons. They have expressed the fear that a launch accident would scatter radioactive plutonium across a wide area of South Florida and even beyond. NASA replies that the plutonium 238 used in RTGs are well shielded and have been tested against the forces that would be exerted in a launch accident. NASA has given assurances that even a launch accident would fail to breach the containment of the plutonium, thus making the fears of the environmental protestors groundless.
What about the shortage of plutonium 238?
During the Cold War, plutonium 238 was derived as a by-product from the building of nuclear warheads. As the Cold War ended, the supply of plutonium 238 has dried up. Some amount has been bought from the Russians, but that source of supply has just about depleted as well. While the government has not revealed how much plutonium 238 it has in its stockpile, it is suggested that there is just enough for one more mission on the scale of Mars Science Lab/
What is the problem with producing more?
Plutonium 238 would be produced by the Department of Energy for NASA. Bothe agencies are willing to enter into this arrangement. The cost is not very great, about $50 million or so over the next five years. Unfortunately, the effort to restart production of plutonium 238 is being blocked in the Congress. The issue is complicated by the fact that the cost would be shared by DOE and NASA and therefore has to be approved by two sets of committees.
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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