NASA Lunar Flashlight Mission Failed Due To Clogged Propellant Lines

NASA's Lunar Flashlight mission came to an end on May 12, 2023, after mission teams worked to overcome technical challenges for five months.The mission, which aimed to place a cubesat into lunar orbit to search for water ice in the moon's shadowed craters, was hindered by the blockage of propellant lines for the spacecraft's thrusters.

Credit : NASA

The Lunar Flashlight mission launched on a SpaceX Falcon 9 rocket, as a secondary payload with ispace's HAKUTO-R M1 lunar lander. 

Troubles with the cubesats thrusters, which utilized a green propellant called ASCENT, emerged shortly after launch. Only one of the four thrusters, designated as thruster four, performed as expected, while the others failed to achieve their intended thrust levels.

Engineers at NASA's Jet Propulsion Laboratory (JPL) developed innovative techniques to counteract the propulsion system's deficiencies. Initially, they managed to perform trajectory corrections using a single thruster, a method that temporarily kept the mission on track. However, during the ninth maneuver of this nature, the thrust from the lone functional thruster dropped to zero, rendering any hopes of achieving lunar orbit unattainable.

The mission teams  explored alternative trajectories, pinning their hopes on thruster three, which managed to produce only 25% of its intended thrust. Regrettably, this thruster also faltered shortly thereafter.

In an attempt to salvage the mission, engineers considered high-risk strategies to restore the thrusters, including reversing the propellant pump and increasing pressure to the limits of another thruster. These efforts initially yielded positive results, but a subsequent test resulted in a dramatic drop in temperature and pressure, likely caused by a ruptured propellant line.

Throughout the troubleshooting process, suspicions mounted that foreign object debris within the propulsion system was responsible for the persistent thruster malfunctions. Post-mission investigations substantiated these concerns, ruling out other explanations. Missions teams believe that titanium particles, potentially loosened by vibrations during launch and pressurization cycles, were a likely source of the debris. The propulsion system had undergone additive manufacturing, and sintered particles within the propellant lines may have become dislodged.

JPL has suggested that proper cleaning procedures and additional filters might have averted the issue, but the project's tight schedule and limited resources posed significant challenges. The propulsion system's development had been marked by intense time pressure, as the mission was initially intended to launch as part of the Artemis 1 mission on NASA's Space Launch System.

Despite the Lunar Flashlight mission's failure to achieve lunar orbit and its primary scientific objectives, NASA emphasizes the accomplishments achieved throughout the endeavor. The mission showcased successful demonstrations of the laser reflectometer science instrument, a new flight computer, and upgraded radio communication systems.

"Our Lunar Flashlight spacecraft unfortunately did not make it to the moon...But we learned a lot from that mission." - Chris Baker, Program Executive for Small Spacecraft Technology Programs in NASA's Space Technology Mission Directorate