Frozen propellant is visible on the second stage Falcon 9 engine during the launch failure on July 11. Screenshot via SpaceX

SpaceX’s Falcon 9 rocket suffered an engine failure during a Starlink mission on July 11, losing 20 Starlink satellites and triggering a Federal Aviation Administration (FAA) investigation. This is a rare incident for the rocket which hasn’t had a major failure since 2015. 

The mission took off from Vandenberg Space Force Base at 7:36 p.m. PT on July 11, carrying 20 direct-to-cell Starlink satellites. During launch, stage separation was successfully and the first stage returned to Earth. The Starlink satellites were deployed 3 minutes and 11 seconds into the mission, which is in line with another recent direct-to-cell launch.  

SpaceX issued a statement on July 12, reporting that after stage separation and a nominal first burn, a liquid oxygen leak developed on the second stage. The Merlin Vacuum engine experienced an anomaly and was unable to complete its second burn. While it did deploy the satellites, the engine did not circularize its orbit.

Pieces of the second stage engine were visibly breaking off during the launch broadcast, and frozen propellant could be seen as well. 

SpaceX said the satellites were released to an an eccentric orbit with a very low perigee of 135 km, which is less than half the expected perigee altitude. SpaceX said this is a high-drag environment and maximum available onboard thrust would be unlikely to raise the satellites orbit. The satellites will re-enter the atmosphere.

After the launch, SpaceX founder Musk detailed efforts to raise the satellite orbits on X.  “We’re updating satellite software to run the ion thrusters at their equivalent of warp 9. Unlike a Star Trek episode, this will probably not work, but it’s worth a shot,” he said. 

The FAA said in a statement that the failure requires an investigation. 

“A return to flight is based on the FAA determining that any system, process, or procedure related to the mishap does not affect public safety. In addition, SpaceX may need to request and receive approval from the FAA to modify its license that incorporates any corrective actions and meet all other licensing requirements,” the FAA statement reads. 

SpaceX said it will work with the FAA throughout the investigation.

“This event is a reminder of how technically challenging spaceflight is,” SpaceX said in a statement. “SpaceX will perform a full investigation in coordination with the FAA, determine root cause, and make corrective actions to ensure the success of future missions. With a robust satellite and rocket production capability, and a high launch cadence, we’re positioned to rapidly recover and continue our pace as the world’s most active launch services provider.”

A grounded Falcon 9 will likely impact a number of upcoming missions, including the Polaris Dawn human spaceflight mission set for no earlier than July 31, and Space Norway’s Arctic Satellite Broadband Mission (ASBM) set for mid-July.

Seradata, a Slingshot Aerospace company that tracks launches and satellites in orbit, noted that Falcon 9 has not had a major failure since 2015 when the second stage tank exploded in a Dragon cargo mission for NASA.

Facon 9 has had four failures — two minor launch dispenser failures in 2023, the 2015 Dragon mission, and a 2012 first stage engine shutdown. Seradata reports the Falcon 9 and Heavy family has flown 363 times.