NASA’s Psyche Probe Faces Propulsion Glitch on Way to Asteroid

Overview of the Propulsion Anomaly

NASA’s Psyche spacecraft, currently about 150 million miles from Earth on its six-year journey to the metal-rich asteroid Psyche, experienced an unexpected drop in its xenon feed-line pressure earlier this month. On April 1, onboard sensors recorded a decline from ~36 psi to ~26 psi inside the line that delivers xenon propellant to the spacecraft’s four Hall effect thrusters. In response, the flight software automatically shut down the plasma engines to protect the system from potential damage.

Solar Electric Propulsion: System Architecture

The Psyche mission relies on solar electric propulsion (SEP), which combines large, deployable solar arrays (each wing spans ~12 m and can generate up to 20 kW at 1 AU) with high-efficiency Hall effect thrusters. Each Fakel SPT-140 thruster delivers ~250 mN of continuous thrust by ionizing xenon gas in a 30 cm discharge chamber, using magnetic coils to shape the plasma plume. Xenon is stored in seven titanium-lined composite tanks (82 L each), with a total propellant load exceeding 1 000 kg. Propellant regulation is handled by dual-redundant pressure regulators, mass flow controllers, and a network of isolation valves built by Maxar Space Systems in California.

Diagnostic Efforts and Redundancy Protocols

Engineers at JPL have begun a step-by-step troubleshooting sequence. Initial steps include cross-checking the pressure transducer calibration, commanding manual valve cycling, and introducing a controlled back-pressure to isolate potential leaks. If the primary feed-line is confirmed compromised, mission controllers will activate the parallel redundant manifold, which routes xenon through an alternate line equipped with separate regulators and filters. All commands are uplinked via NASA’s Deep Space Network (DSN) and executed in real time during dedicated communication passes.

Trajectory Implications and Gravity Assist Maneuver

With thrusters offline, Psyche’s trajectory remains within mission tolerances. The next critical maneuver is a Mars gravity assist scheduled for May 2026, which requires precise SEP burns to target the flyby corridor. According to navigation data from the DSN, Psyche can coast without thrust until mid-June before course deviations exceed 100 km. Should the pressure anomaly persist, engineers plan to perform attitude-controlled wheel-offloads to maintain pointing accuracy, ensuring the spacecraft reaches the Mars window.

Scientific Payload and Mission Objectives at Asteroid Psyche

Upon arrival at the ~225-km–diameter asteroid Psyche in August 2029, the spacecraft will enter a series of polar orbits to map the surface and subsurface. Key instruments include a multispectral imager (0.4–1.0 µm bands), a gamma-ray and neutron spectrometer for elemental abundances, and a magnetometer to detect remnant metallic core fields. Data will test hypotheses that Psyche is an exposed proto-planetary core, shedding light on early Solar System differentiation.

Expert Insights and Future Outlook

“Anomalies like this illustrate the complexity of operating electric propulsion in deep space,” says Dr. Nicky Fox, NASA’s associate administrator for science. “But redundancy and rigorous testing give us confidence that Psyche will resume nominal operations.” Dr. Sarah Houston, a plasma physicist at Caltech, adds: “Hall thrusters have flown on dozens of missions, but each system has its own quirks. Diagnosing a xenon feed issue at 1 AU sets the stage for future SEP missions to the outer planets.”

Broader Implications for Solar Electric Missions

The Psyche anomaly underscores the importance of advanced SEP for large payloads. Upcoming flagship missions—such as Europa Clipper’s supplemental SEP module and proposed cargo tugs for lunar logistics—will build on Psyche’s lessons. Engineers are already evaluating pressure-sensing fiber-optic lines and next-generation ionic liquid propellants to reduce leak risks and improve long-term storage.

Next Steps and Expected Resolution Timeline

• Telemetry analysis and sensor cross-calibration: complete by mid-May 2025
• Backup manifold activation tests: early June 2025
• Resumption of SEP burns to prepare for Mars flyby: June–July 2025
• Gravity assist trajectory confirmation and fine-tuning: Q2 2026

If all goes according to plan, Psyche’s propulsion system will be back online in time to execute the burns that set up the critical Mars gravity assist, preserving the spacecraft’s ambitious schedule and scientific promise.