NASA probes propulsion problem in Psyche's thrusters

Mission to a metal asteroid lacks xenon pressure

NASA is looking into propulsion problems experienced by a probe on its way to orbit the asteroid Psyche.

The Psyche mission uses solar electric propulsion to generate thrust using charged atoms of the neutral gas xenon. The cause of the problem - first detected in April - is a pressure drop in the line feeding the xenon gas to the thrusters. It went from 36 pounds per square inch (psi) or 248 kilopascal (kPa) down to approximately 26 psi (179 kPa), which resulted in the spacecraft shutting off the thrusters.

Engineers are working to understand the pressure decrease and have the option of switching to a backup line to resume thrusting. The team has until mid-June to come up with answers and a mitigation before the probe's trajectory is affected.

The vehicle is currently approximately 148 million miles (238 km) from Earth, and the plan is to slingshot around Mars to send the spacecraft to the asteroid belt between Mars and Jupiter. The probe is set to begin orbiting the asteroid Psyche in 2029.

The mission had a troubled start in life – its launch in 2022 had to be postponed until 2023 thanks to late delivery of the spacecraft's flight software and testing equipment. The delay followed earlier woes caused by compatibility issues with the software testbed simulators.

The plan had been to carry along a pair of small satellites, a mission named Janus, which was put on hold after the Psyche delay. Another payload, the Deep Space Optical Communications demonstration, was carried onboard the spacecraft and has shown data rates peaking above 8 Mbps from 240 million miles (386 kilometers) from Earth.

A damning report into issues at NASA's Jet Propulsion Laboratory (JPL) was published following the delays. We'd also recommend a read of Mars Rover Curiosity: An Insider Account from Curiosity's Chief Engineer by Rob Manning for insight into the pressures engineers and scientists face.

NASA's post on the pressure issue is light on details. We asked the agency how much xenon gas remains and the contingency plan if the spacecraft has to operate on reduced thrust. We'll update this article if we receive a response.

The joint ESA and JAXA mission to Mercury, BepiColumbo, is having to operate with slightly reduced thrust due to electrical power problems. Controllers have had to develop mitigations to ensure the spacecraft arrived in orbit around the planet as planned. ®