SpaceX’s historic capture of a rocket earlier this month was even more dramatic than it seemed.
This capture took place on October 13, during the fifth test flight of SpaceX’s Starship megarocket. Starship’s massive first stage booster, known as Super Heavy, returned to Earth about seven minutes after liftoff, nestled next to its launch tower, which attached the rocket with its “wand” arms.
But this epic moment almost didn’t happen: Super Heavy was just a second away from aborting the launch tower’s landing and crashing into nearby land, SpaceX engineers recently told founder and CEO of the company, Elon Musk.
Musk revealed part of this conversation on X on Friday, October 25, in a post showing the billionaire’s progress in the online game Diablo IV. That post described three minutes of Musk playing Diablo IV, which occurred while he was talking to three anonymous SpaceX engineers about the Starship test flight.
“I wanted to be really candid about the scary things that happened and what we’re doing about it, because I think that’s our goal to get to Flight 6,” one of those engineers told Musk at the start of the post. conversation. This objective, adds the engineer, is “on the reduction of the risks associated with boosters, rather than on the expansion of the envelope of the ship”. (The ship is the upper stage of the spacecraft 165 feet tall or 50 meters.)
Related: Starship and Super Heavy explained
The engineer then goes into detail about the “scary shit.”
“We had a poorly configured spin gas shutoff that didn’t have quite the right ramp-up time to increase the spin pressure,” he explains. “And we were a second away from that firing and telling the rocket to abort and try to crash into the ground next to the tower instead of [landing at] the tower – like mistakenly telling a healthy rocket not to attempt this capture. “
“Wow,” Musk said upon hearing the news.
“We knew that we had a whole bunch of new abandonments and validation criteria that we tried to verify very well,” continues the engineer. “I think our concern was well-placed, and one of them almost bit us.”
“This is one of the reasons why we considered delaying the launch,” adds another engineer.
“If we delay a day, we’d like to go check things out again,” says one of the engineers, speculating on how preparations for Flight 5 might have been different. “I don’t know if we would have found that one, but just so…”
“We were afraid of that before the launch,” intervenes the third engineer.
“Well, we were worried about the fact that we had 100 aborts that weren’t super trivial but super well-founded, and we didn’t do as good a review as we did for takeoff before flight 1,” a- he declared. engineers respond.
Work to prepare for Starship’s sixth test flight aims to achieve “a reasonable balance between speed and risk mitigation, on the booster in particular,” one of the engineers said later.
The conversation also touches on some damage Super Heavy suffered during Flight 5. A cover protecting a longitudinal structure on the booster, called a chine, came loose during its descent – and this could easily have scuttled the tower hook as well.
“We were worried about these spot weld margins on the chine skin before the flight,” explains one of the engineers. “We wouldn’t have predicted the exact right location, but that cover that came off was right above a group of single-point-of-failure valves that need to operate during landing. Fortunately, none of those Neither harness was detected as damaged, but we ripped off that chine cover on some really critical equipment just as the landing burn was starting.
SpaceX is developing the 122m-tall Starship, the largest and most powerful rocket ever built, to help humanity colonize the Moon and Mars.
The stainless steel vehicle is designed to be fully and quickly reusable, which is key to what SpaceX sees as its transformative potential. The launch tower captures are a big part of this grand vision; the company aims to lower both the Super Heavy and the Ship directly onto the launch pad, enabling faster and more efficient inspection, refurbishment and reflight.