What caused the Starship engine failure on SpaceX's final mission?

On Saturday, the Starship spacecraft succeeded in reaching its orbit successfully and without any major problems. This is a big change compared to the 14th flight that took place in September, as SpaceX continued carrying out that mission, and gave the green light for the vehicle to reach orbit despite the failure of one of the rocket engines on the spacecraft.

Starship did not need that engine for any subsequent operations, but the decision was surprising given the company's conservative standards. “When smart minds come together in one room, using all the information available to make informed decisions about risks, where the bet is total, those moments become milestones in the company’s journey,” says Jeremy Pedro, director of Starship propulsion systems at SpaceX.

At a conference in October, Elon Musk, the company's CEO, explained that the engine's cessation was due to "a glitch in the engine's computer software." We asked a former SpaceX employee about that moment.

“Sometimes the tolerances in that software are too tight,” said Austin Spiegel, formerly chief software engineer at SpaceX and co-founder and CEO of software startup Sift. He emphasized that this is why previous flight data is important, as flight controllers can “refer to that test data to understand the performance characteristics of the engine, which gives them a much deeper understanding of how the engine will operate at the moment of launch.”

Spiegel adds that this understanding gives engineers the confidence to move forward, even under less than ideal conditions. The only problem with Flight No. 15, which SpaceX revealed during the live broadcast on Friday, is related to the Super Heavy rocket booster, as one of its 33 engines stopped working prematurely.

It is not yet clear whether other problems arose that prompted SpaceX to jettison the booster into the ocean rather than attempt to recover the vehicle by guiding it back to the launch tower on Earth.