SpaceX reveals the cause of the Starship anomaly while overcoming an FAA hurdle

Just over three months after Starship's last launch, which ended with the loss of both the booster and upper stage in flight, the Federal Aviation Administration has closed its investigation into the mishap.

“SpaceX has identified the root causes and 17 corrective actions documented in the SpaceX Incident Report, and the FAA has approved them,” the federal agency said in a statement issued Monday. “Prior to the next launch, SpaceX must implement all corrective actions and obtain a license modification from the FAA that addresses all applicable safety, environmental and other regulatory requirements.”

SpaceX still must provide additional information to the Federal Aviation Administration, which is responsible for the safety of people and property on Earth, before the agency completes its review of the request to launch Starship for a third time. FAA Commercial Space Transportation Administrator Kelvin Coleman said last week that early to mid-March is a reasonable timeline for concluding the regulatory process.

A launch attempt will likely follow shortly after.

What happened

Coinciding with Monday's announcement, SpaceX released for the first time details of what happened to the November 18 launch failure.

In this update, SpaceX noted that the Super Heavy rocket's first stage performed nominally, with all 33 Raptor engines on this massive rocket successfully firing up. The booster then performed a full-duration burn to reach the separation phase. At this point, the upper stage executed a successful “hot staging” maneuver in which the spacecraft stage separated from the booster while some of the booster's engines were still running.

For the super-heavy rocket, the next step was to perform a series of burns to make a soft landing in the Gulf of Mexico. As part of the initial burn, 13 of the rocket's engines were intended to be fired.

“During this burn, several engines began to idle before one engine failed hard, quickly resulting in a rapid, unscheduled disassembly of the booster.” SpaceX said. “The disintegration of the vehicle occurred more than three and a half minutes into the flight at an altitude of approximately 90 kilometers above the Gulf of Mexico.”

The problem was later linked to a problem supplying liquid oxygen to the Raptor's engines.

“The most likely root cause of the boosted RUD was determined to be a clogged filter where liquid oxygen is supplied to the engines, resulting in a loss of inlet pressure in the engine's oxidizer turbo pumps and ultimately resulting in one engine failing in a manner that resulted in the loss of the vehicle,” the company said. “SpaceX has since implemented hardware changes within future booster oxidizer tanks for improved propellant filtration capabilities and enhanced operations to increase reliability.”

Spacecraft hatches

As Super Heavy was experiencing these problems, the six Raptor engines in the spacecraft's upper stage were nominally burning and propelling the vehicle along a flight path intended to travel approximately two-thirds of the way around Earth before touching down near Hawaii. However, about seven minutes after liftoff, a significant vent of liquid oxygen occurred. SpaceX said there is a surplus of liquid oxygen in the vehicle, to collect data representative of future payload deployment missions. It had to be launched before the spacecraft fell.

The company said: “A leak in the back section of the spacecraft that occurred when the liquid oxygen vent was activated led to subsequent combustion and fires that led to the loss of communication between the spacecraft’s flight computers.” “This resulted in all six engines shutting down before the ascent was completed, followed by the autonomous flight safety system detecting a mission rule violation and activating the flight termination system, resulting in the vehicle malfunctioning.”

At that time, the vehicle reached an altitude of 150 kilometers in outer space, and achieved a speed of about 24 thousand kilometers per hour. This is slightly less than the orbital speed, which is 28,000 km/h.

SpaceX said in its statement that it is implementing changes to the Super Heavy and Starship stages to account for these issues. The company is also seeking to improve the Starship's overall performance, adding a new electronic propulsion control system for the Raptor engines in the Starship's upper stage and faster pre-launch fuel loadings.

SpaceX has four spaceships in the full or nearly complete construction stages. If the next flight goes smoothly, the company could begin launching the world's largest rocket repeatedly.