Deep-space exploration missions are in jeopardy

Oct 1, 2009 10:04 GMT  ·  By

The American space agency NASA usually makes use of solar panels for its exploration missions in the solar system, such as for instance on Mars, the Moon, Saturn, Mercury, Vesta, Ceres, and so on. But these explorations take place in the relative vicinity of the Sun, so the amount of electricity produced by the solar panels is sufficient for the small spacecraft. In the case of deep-space missions, however, things are a bit different. Freezing temperatures and the lack of sunlight mean that probes need to be fueled by plutonium-238, whose heat is converted into electricity aboard the probes.

The latest, long-duration mission to Pluto, for instance, is powered by an ion thruster, but the technology is still relatively new and expensive to implement. At this point, plutonium-238 remains the only feasible option that combines the best of life span and costs. But, because the chemical isotope has been so extensively used, NASA is currently reaching the limits of its supplies. This type of plutonium is not to be mistaken for plutonium-239, which is the variety used to manufacture nuclear weapons.

According to a new NPR report, the situation is growing increasingly critical, and its remedy lies with the Congress. If representatives approve the $30 million required to restart plutonium-238 production, then things could fall back on track shortly. More than two dozen space probes have been powered by this chemical isotope over the years, including the 1970 Voyager and the current Cassini mission to Saturn. Things have grown so desperate because plutonium-238 production in the United States stopped in the 1980s. They then borrowed it from Russia, but the country has stopped production too recently.

According to Johns Hopkins University Applied Physics Laboratory expert Ralph McNutt, quoted by Technology Review, “We've been living off of the material that we had produced up until that time, and if you keep using material and you have a finite supply, eventually you run out, and that's where we are right now. It's kind of like having a car, and if all the gasoline stations are closed and are out of gasoline, and you're out of gas, you're not going to go anywhere.”

“NASA has enough plutonium-238 for its next Mars rover, called the Mars Science Laboratory, and the next planned major mission to the outer planets. The agency could also potentially have a relatively low-cost, Discovery-class mission that would use only a small amount of the stuff, to test a new power-generation technology that could more efficiently convert the heat of plutonium-238 to electricity,” the NPR report says.