Daily Kos by Mark Sumner 4/22/2023
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Now, let’s walk through the actual flight.
The short life of Starship
After a hold at T-40 seconds, SpaceX seemed satisfied that all issues had been addressed and walked down to the launch. However, right from the beginning there was a bit of weirdness. The engines should have fired up at around T -6. They didn’t. Instead, it wasn’t until about one second before the clock hit zero that the first flames appeared. Then the clock actually hesitated for a moment before moving the other way. Five seconds later, Starship was still sitting on the pad. It would be 15 seconds before it cleared the tower.
What’s also visible on close inspection of these image is some absolutely enormous pieces of debris. It’s not just ice falling from the sides of the tank, its massive chunks of concrete sent flying into the sky, some of it coming up right alongside Starship. Images from other angles show large chunks of concrete flying to the waters on all sides of the tower. In fact, the reason that the cloud here is brown rather than the white usually seen at Cape Kennedy launches is because it’s not smoke. Most of it is sand, rock, and shattered concrete being hurled up from the ground.
Much of Stage Zero was terrifically damaged at this point.
Sixteen seconds in, just after clearing the tower, SpaceX rolled out a graphic that provides a lot of nice information about the progress of the flight. But one of the first things that’s visible is that three of the Raptor 2 engines on the flight are already out. That’s likely because they were damaged by rocks or concrete chunks flung upward while Starship was still on the pad.
Remember those clamps? On a rocket like the Saturn V, they would actually hold the rocket in place for a couple of seconds while the rocket came fully up to power. Then the clamps let go.
SpaceX did it another way. They opened the clamps before the countdown even began. Then they slowly throttled up the rocket on the pad. That’s why it took Starship, with twice the power of a Saturn V, almost twice as long to clear the tower. It just sat there for a lot longer, blasting away at the ground. That was all part of the plan — but it was also part of what doomed the flight.
A minute into the flight, Starship was approaching “Max Q,” the point of maximum stress on the airframe. The announcer certainly sounds happy in the video of the flight at this point, but the truth is that Starship is gaining velocity more slowly than expected, and is several seconds behind in reaching this critical point. Looking at the infographic, it’s not hard to see why.
That graphic shows four engines out, but there are good reasons to disbelieve the infographic by this point. Here’s a closeup on the rear of Starship just a few seconds later.
It’s not missing four engines. It’s missing six.
Starship is still going, but it is rising more slowly and gaining speed with more difficulty than it should. Which isn’t surprising, with 18% of its engine power missing. Not only have there been a number of engine failures, when the first images come from the rocket, they show that it is both rotating and also repeatedly changing its attitude. The first probably represents a loss of some flight control, possibly damage to a second stage fin or the ability of the booster to gimbal its engines. The second is probably software struggling to put the rocket onto the designed flight path, but failing because of those missing engine.
Also, the engine exhaust to this point has been very yellow — not the expected color for a methane rocket. Starship is likely not getting the correct balance of fuel and oxygen, possibly because of damage to lines or valves while it was still on the ground. In rocketry terms, it looks as if it is burning “engine rich,” eating up the metal of its own systems as it goes.
Two and a half minutes into the flight, Starship is nearing what should be main engine cut off and stage separation. Only this is where things go finally, terminally wrong. Because the main engines don’t cut off.
By this point, the infographic shows five boosters out, but as we’ve already seen, that graphic isn’t accurate. A look at the flame pattern suggests that Starship is now down by eight engines — it’s lost almost a quarter of its thrust.
Even so, Starship does begin the pitch over maneuver that should separate the two stages. That camera view on the left should show the first stage dropping away and the second stage kicking in. Only it doesn’t.
That’s because, even as Starship pitches, and pitches, and pitches, eventually going through a full 360 degree loop, the main engine just keeps firing. Down by eight engines, the rocket hasn’t reached the speed or altitude it was supposed to attain. It also hasn’t burned through the amount of fuel that it should have consumed. Some part of the booster’s software seems to be insisting that it has to keep going, even as another part has signalled time for separation.
That continued thrust from the first stage keeps the two parts of the ship pressed together. They can’t separate, because the first stage keeps on pushing and won't stop. The first stage keeps pitching, and thrusting, and by now Starship is in a full head over heels tumble. It’s also stopped gaining altitude, somewhere around 37km, and has begun to fall back. The first stage is still burning.
SpaceX lets it keep tumbling until it has fallen about a kilometer, then it finally opens the plastic cover no one wants to open and presses the big red button.
More:
https://www.dailykos.com/stories/2023/4/22/2165317/-A-Starship-Post-mortem-Why-the-giant-rocket-failed-and-why-it-s-Elon-Musk-s-fault?utm_campaign=recent
