It was only about 10 days ago that the Falcon 9 rocket's upper stage failed in flight, preventing the rocket from delivering its 20 Starlink satellites into a proper orbit. Because they were released lower than expected—about 135 km above the Earth's surface and subject to atmospheric drag—these satellites ultimately reentered the planet's atmosphere and burnt up.

Typically, after a launch failure, a rocket will be sidelined for months while engineers and technicians comb over the available data and debris to identify a cause, perform tests, and institute a fix.

However, according to multiple sources, SpaceX was ready to launch the Falcon 9 rocket as soon as late last week. Currently, the company has a launch opportunity for no earlier than 12:14 am ET (04:14 UTC) on Wednesday for its Starlink 10-4 mission.

A quick fix?

In a summary of the anomaly posted shortly afterward, SpaceX did not identify the cause of the failure beyond saying, "The Merlin Vacuum engine experienced an anomaly and was unable to complete its second burn."

Officially, the company has provided no additional information since then. However, the company's engineers were able to identify the cause of the failure almost immediately and, according to sources, the fix was straightforward.

SpaceX was confident enough in this determination to resume launches of the Falcon 9 rocket one week after the failure. However, it is precluded from doing so while the US Federal Aviation Administration conducts a mishap investigation.

To that end, a week ago on July 15, SpaceX submitted a request to the FAA to resume launching its Falcon 9 rocket while this investigation into the anomaly continues. "The FAA is reviewing the request and will be guided by data and safety at every step of the process," the FAA said in a statement at the time.

Crewed missions on deck

So, as of today, SpaceX is waiting for a determination from the FAA as to whether it will be allowed to resume Falcon 9 launches less than two weeks after the failure occurred.

The company plans to launch at least three Starlink missions in rapid succession from its two launch pads in Florida and one in California to determine the effectiveness of the fix. It would like to demonstrate the reliability of the Falcon 9 rocket, which had recorded more than 300 successful missions since its last failure during a pad accident in September 2016, before two upcoming crewed missions.

There is still a slight possibility that the Polaris Dawn mission, led by commercial astronaut Jared Isaacman, could launch in early August. This would be followed by the Crew-9 mission for NASA, which will carry four astronauts to the International Space Station.

Notably, neither of these crewed missions requires a second burn of the Merlin engine, which is where the failure occurred earlier this month during the Starlink mission.