NASA’s Psyche mission fires up its futuristic electric engines

NASA has fired up the electric Hall thrusters of Psyche, a spacecraft now gently heading toward a metal-rich asteroid embedded in the main asteroid belt beyond Mars. He agency says Psyche is now in “full cruise” mode, six months after its launch on October 13, 2023, on a conventional SpaceX rocket.

Along the way, NASA used Psyche to test laser-based deep space communications. The spacecraft fired a communications laser at Earth from about 10 million miles away, a first for NASA. It is expected to reach its target and namesake, the asteroid Psyche, by 2029 and will orbit it for two years, observing and sending data to NASA. Scientists suspect that Psyche is actually the initial core of a planet, also called a planetesimal.

Ion propulsion is relatively new and quite old for NASA. The agency has been working on the technology since before American astronauts first flew to the Moon, having tested its first ion thruster in 1964. They also have no moving parts; instead, they generate thrust by exciting xenon particles, pushing them out of the propellant. You can read more about them in this NASA article (PDF) that describes ion propulsion.

There are many different types of ion propulsion, including the Hall magnetic thrusters used by Psyche. In 2018, the chief engineer of the Psyche spacecraft wrote this detailed explanation of the differences between those and other ion thrusters, as well as other types such as arc jets and microwave thrusters.

NASA first used ion propulsion as primary spacecraft propulsion in 1998’s Deep Space 1, a mission conducted specifically to test «several advanced technologies for future interplanetary missions.» In 2007, Dawn became NASA “First purely science-focused mission” to use ion thrusters and fly until ran out of hydrazine, the fuel it used for its guidance thrusters. Without them, he wouldn’t be able to backtrack to maintain communication with NASA.

Ion propulsion is not powerful enough to launch a rocket from Earth, but they can still reach very high speeds over time. Right now, NASA says Psyche is traveling at 23 miles per second, or about 84,000 mph, and will eventually reach 124,000 mph. Thrusters like Psyche’s are generally useful because the lack of moving parts makes them durable and they use less fuel, so they are lighter and can be used in smaller spacecraft. Plus, they look great when lit.