Lockheed Martin, one of the bigger companies behind NASA’s 3 billion-million journey to Pluto, has posted a timely reminder of its efforts on the New Horizon spacecraft’s power system.
Launched in 2006, New Horizons was set to send back dramatic new video of its long-awaited approach to the icy dwarf planet Pluto and its moons on July 14.
Lockheed Martin helped build the special radioisotope power source for the spacecraft — which unlike most solar-powered spacecraft can’t rely on sunlight, as the sun is so far away from Pluto.
“A radioisotope power system can take you places far away from the sun or to a remote location where solar power isn’t feasible, such as locations beyond Jupiter’s orbit or parts of the moon where the sun does not reach,” said Tim Hoye, a member of Lockheed Martin’s engineering team for New Horizons.
The radioisotope power source aboard New Horizons is known as a radioisotope thermoelectric generator. This particular RTG is roughly 17 inches in diameter and 42 inches long, yet it is capable of powering the spacecraft for decades.
“The very desirable quality of RTGs is that they are solid state, meaning they have no moving parts,” Hoye said. “You can install the plutonium fuel and it goes. There is nothing to wear out. It has very high reliability and the design has a demonstrated long life.”
Still, though RTGs are extremely reliable, they operate at low efficiency, with just 7 percent of the thermal energy produced gets converted into electrical energy. Lockheed Martin says the next evolution in radioisotope space power systems involves what is known as a Stirling conversion system.
The Stirling cycle engine — named for the developer of the thermodynamic cycle engine — is a heat engine that drives an oscillating piston coupled to a linear alternator. That, in turn, generates alternating current power, forming a system four times more efficient than the RTG.
As for New Horizons, Hoye is hoping the mission will be extended to probe a group of celestial objects beyond Pluto, known as the Kuiper Belt. That would mean traveling billions of miles beyond New Horizons’ original destination, but Hoye believes the RTG is well capable of producing sufficient power.