SpaceX aims to resume launching the Falcon 9 rocket tomorrow after the Federal Aviation Administration (FAA) agreed to let the company return to flight operations.

An FAA spokesperson told The Register: "After a comprehensive review, the FAA determined no public safety issues were involved in the anomaly that occurred during the SpaceX Starlink Group 9-3 launch on July 11.

"This public safety determination means the Falcon 9 vehicle may return to flight operations while the overall investigation remains open, provided all other license requirements are met."

SpaceX made a public safety determination request on July 15 following an upper-stage mishap earlier this month. The FAA spent a few days considering it and determined there wasn't a risk to public safety - so Elon Musk's rocketeers could continue launching their rockets while the overall investigation rumbled on.

SpaceX posted an explanation of the incident. The upper-stage leak, which was clearly visible during the mission broadcast, was identified as a crack in a sense line for a pressure sensor attached to the vehicle's oxygen system. This resulted in the spewing of oxygen around the upper-stage engine.

"This line cracked due to fatigue caused by high loading from engine vibration and looseness in the clamp that normally constrains the line," according to SpaceX.

The first burn of the engine went fine, but the liquid oxygen leak resulted in what SpaceX described as "excessive cooling" of engine components, such that when the engine was restarted to circularize the orbit before deployment of the satellites, there was an explosion.

Even following the "hard start" and a loss of attitude control, the stage was still able to deploy the satellites (just into the wrong orbit) and passivate itself.

The solution? Get rid of the line and sensor. SpaceX said: "For near term Falcon launches, the failed sense line and sensor on the second stage engine will be removed. The sensor is not used by the flight safety system and can be covered by alternate sensors already present on the engine."

Thus, according to SpaceX, it is "poised to rapidly return to flight as soon as Saturday, July 27."

The Register asked NASA if this return to flight would include humans launched on behalf of the agency but were told that an announcement would be made later today. Making a change in a human-rated system would raise a few eyebrows, assuming the upper-stage that experienced the mishap was of the same design as that used to send astronauts to the International Space Station (ISS).

The next launch of the Crew Dragon is set for August. As for the other imminent crewed mission on SpaceX's books - Polaris Dawn - the mission's commander, Jared Isaacman, paid tribute to the efforts of Musk's rocket company but noted: "Turns out we have a little bit of time before Polaris Dawn launches." ®

https://www.theregister.com//2024/07/26/spacex_falcon_9_flight/