SpaceX recently reported that a Falcon 9 upper stage, which reentered over Europe, experienced a propellant leak that hindered its controlled reentry. This event highlights ongoing challenges faced by the aerospace company.
The incident occurred following a February 1 launch from Vandenberg Space Force Base in California. The mission successfully deployed 22 Starlink satellites as part of the Group 11-4 mission. However, the upper stage was expected to perform a controlled reentry burn over the ocean, a standard procedure for most Falcon 9 launches to low Earth orbit.
According to U.S. Space Force tracking data, the stage did not execute the burn and remained in orbit. Due to atmospheric drag, its orbit decayed, and it reentered over Europe on February 19. Debris, including composite overwrapped pressure vessels, landed in Poland near Poznań. The falling debris caused minimal damage, such as a broken light fixture. A Polish farmer expressed intent to seek compensation for a crater left in his field by one of the tanks.
SpaceX confirmed that the upper stage failed to perform its deorbit burn due to a liquid oxygen leak. “During the coast phase of this Starlink mission, a small liquid oxygen leak developed, which ultimately drove higher than expected vehicle body rates,” SpaceX stated. The company passivated the upper stage to prevent breakup by venting propellant tanks and discharging batteries.
This marks the third incident involving a Falcon 9 upper stage in just over six months. In July 2024, a similar liquid oxygen leak prevented a circularization burn during a Starlink satellite launch. The payload deployed, but high atmospheric drag caused it to reenter prematurely. SpaceX identified that the leak led to ice buildup on the upper stage’s Merlin engine, causing excessive cooling and a hard start during the engine's second burn. Launches resumed 15 days later.
Another anomaly occurred during the Crew-9 mission to the International Space Station in September. The upper stage experienced an “off-nominal deorbit burn,” leading to reentry outside the designated zone in the South Pacific Ocean. SpaceX paused Falcon 9 launches to investigate, and the Federal Aviation Administration approved resumption nearly two weeks later, with a waiver for the Hera asteroid mission launch.
These incidents, along with a failed Falcon 9 booster landing in August, have attracted attention from the Aerospace Safety Advisory Panel, NASA’s independent safety committee. Kent Rominger, a former astronaut and panel member, emphasized the importance of attention to detail as hardware ages and operations increase.
Only the July incident resulted in a mission failure. The Crew-9 Crew Dragon spacecraft and the Starlink satellites from the February 1 launch were deployed before the stage deorbiting anomalies. SpaceX stated that teams are actively assessing the root cause of the leak and have implemented mitigations for future flights, though additional details were not provided.
