by SpaceX’s historic rocket capture earlier this month was even more dramatic than it seemed.
That capture occurred on October 13, during the fifth test flight of SpaceX’s Starship mega-rocket. Starship’s massive first-stage booster, known as Super Heavy, returned to Earth about seven minutes after liftoff and settled next to the launch tower, which held the rocket with its “chopstick” arms.
But that epic moment almost didn’t happen: Super Heavy was just a second away from aborting the launch tower landing and crashing into a patch of nearby ground, SpaceX engineers recently told company founder and CEO Elon Musk.
Musk revealed part of that conversation on Friday (October 25) on X, in a post showing the billionaire’s progress in the online game Diablo IV. That post depicted three minutes of Musk’s Diablo IV gameplay, which took place while he was talking to three unnamed SpaceX engineers about the Starship test flight.
“I wanted to be really honest about the scary things that happened and what we’re doing about it, because I think this is our focus on getting to Flight 6,” one of those engineers tells Musk at the start of the post. conversation. That focus, the engineer added, is “on reducing the risk of boosters, rather than expanding the ship’s envelope.” (The ship is the upper stage of the 165-foot or 50-meter spaceship.)
Related: Starship and Super Heavy explained
The engineer then goes into detail about the “scary sh*t.”
“We had a misconfigured spin throttle cutoff that didn’t quite have the right ramp time to increase spin pressure,” he explains. “And we were a second away from tripping and telling the rocket to abort and try to crash into the ground next to the tower instead of [landing at] the tower – for example, wrongly telling a healthy rocket not to attempt that catch.
“Wow,” Musk says as he hears the news.
“We knew we had a whole new set of abort and commit criteria that we were trying to control very carefully,” the engineer continues. “I think our concerns were justified, and one of these came very close to biting us.”
“This was one of the reasons why we thought about postponing the launch,” added another engineer.
“If we postpone it for a day, we would double-check things,” said one of the engineers, speculating on how preparations for Flight 5 could have gone differently. “I don’t know if we would have found this one, but just to…”
“We were afraid of that before the launch,” the third engineer interjects.
“Well, we were scared of the fact that we had 100 aborts that were not super trivial, but ultra-well-founded, and we didn’t make as good an assessment as we did at the launch before Flight 1,” said one of the researchers. of engineers respond.
Preparatory work for Starship’s upcoming sixth test flight is aimed at achieving “a reasonable balance between speed and risk mitigation, specifically on the booster,” one of the engineers said moments later.
The conversation also turns to the damage Super Heavy sustained during Flight 5. A cover protecting a longitudinal structure on the booster, called a chine, came loose during the descent – and that could easily have sunk the tower catch as well.
“We were concerned before the flight about these spot weld edges on the jaw skin,” says one of the engineers. “We didn’t predict exactly the right spot, but this cover that tore off was right on top of some single-point failure valves that have to work during landing. Luckily none of these or the armor were damaged. damaged, but we ripped this buckling protection over some very critical equipment just as the landing fire started. We have a plan to address that.”
SpaceX is developing the 400-foot spacecraft, the largest and most powerful rocket ever built, to help humanity colonize the moon and Mars.
The stainless steel vehicle is designed to be completely and quickly reusable, which is key to what SpaceX sees as its transformative potential. Launch tower captures are a big part of this grand vision; The company aims to bring down both Super Heavy and Ship directly at the launch pad, allowing for faster and more efficient inspection, refurbishment and reaeration.
