WASHINGTON — SpaceX said that a Falcon 9 upper stage that reentered over Europe earlier this week suffered a propellant leak that prevented it from doing a controlled reentry.
The upper stage was placed in orbit on a Feb. 1 launch from Vandenberg Space Force Base in California. After deploying its payload of 22 Starlink satellites on the Group 11-4 mission, the upper stage was expected to perform a burn to enable a controlled reentry over the ocean, a standard procedure on most Falcon 9 launches to low Earth orbit.
The stage, though, did not appear to perform the burn and remained in orbit, according to U.S. Space Force tracking data. Its orbit decayed from atmospheric drag and, early Feb. 19 (local time), the stage reentered over Europe. Debris from the stage, including composite overwrapped pressure vessels, fell in Poland, landing near the city of Poznań.
The falling debris caused only very minor damage, such as a broken light fixture. A Polish farmer told Polish television that he would seek compensation for a crater left in his field by one of the tanks.
SpaceX, in a statement added to the page about the mission on its website after the upper stage’s reentry, confirmed that the stage was unable to perform its deorbit burn, which the company blamed on 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 instead passivated the upper stage, removing sources of energy that could cause the stage to break up. That is typically done by venting propellant tanks and discharging batteries.
This is the third incident involving a Falcon 9 upper stage in a little more than six months. In July 2024, a Falcon 9 launch of Starlink satellites suffered a liquid oxygen leak that prevent the upper stage from performing a circularization burn. Its payload of Starlink satellites deployed from the upper stage, but high atmospheric drag caused them to soon reenter.
SpaceX found that a liquid oxygen leak caused ice to build up the upper stage’s Merlin engine and resulted in “excessive cooling of engine components,” resulting in a hard start of the engine for its second burn. Falcon 9 launches resumed 15 days after the failure.
A second anomaly involving the Falcon 9 upper stage took place during the launch of the Crew-9 mission to the International Space Station in September. SpaceX said the upper stage had an “off-nominal deorbit burn” that caused the upper stage to reenter outside the designated zone in the South Pacific Ocean. SpaceX again paused Falcon 9 launches to investigate the issue.
The Federal Aviation Administration gave its approval for Falcon 9 launches to resume nearly two weeks later, after giving a waiver for one Falcon 9 launch, of the Hera asteroid mission, that did not include a deorbit burn.
Those two incidents, as well as a failed landing of a Falcon 9 booster in August, caught the attention of the Aerospace Safety Advisory Panel, NASA’s independent safety committee. “When you look at these recent incidents over the last handful of weeks, it does lead one say that it’s apparent that operating safely requires significant attention to detail as hardware ages and the pace of operations increases,” Kent Rominger, a former astronaut who is a member of the panel, said at an Oct. 31 committee meeting.
Only the July incident caused a mission failure, with both the Crew-9 Crew Dragon spacecraft and the Starlink satellites on the Feb. 1 launch deployed before the stage deorbiting anomalies. The latest incident also did not result in an extended pause in SpaceX launches.
“The teams are actively assessing root cause of the source of the leak and have already implemented mitigations for future flights,” SpaceX stated on its website, but did not provide additional details about those mitigations.
