Nuclear Energy Insight Winter 2012
—Wending its way through space before touching down on the red planet, Mars rover Curiosity will be the first of the rovers to run on nuclear energy, allowing it to be larger and capable of a broader range of projects than its solar-powered predecessors. The rover, launched in November from Kennedy Space Center, is a large mobile laboratory that will investigate whether conditions on Mars have favored the development of microbial life.
Electrical power and heat for the lab’s instruments will be provided by a radioisotope thermoelectric generator, a “space battery” that uses plutonium fuel to provide 110 watts of electricity for the rover’s 23-month mission. Curiosity is expected to land on Mars in August.
NASA is using a nuclear power source for the mission because, unlike solar power alternatives, the radioisotope-based system will allow full-time communication with Earth during all phases of the mission, including descent and landing. Solar panels on earlier missions proved to be vulnerable to dust and debris that would cause communications to go silent until the panels cleared.
“You can operate with solar panels on Mars; you just can't operate everywhere,” says Stephen Johnson, director of the Space Nuclear Systems and Technology Division at Idaho National Laboratory, which developed the spacecraft’s power system. Using nuclear energy “gives you an opportunity to go anywhere you want on the planet, not be limited to the areas that have sunlight, and not have to put the rover to sleep at night.”
A space battery can last for many years. As the radioactive fuel naturally decays, it gives off heat. Electric voltage is produced by using thermocouples, which exploit the temperature difference between the heat source and the cold exterior.
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