SpaceX
In a wide-ranging talk on Saturday night, SpaceX founder Elon Musk reviewed the debut launch of the Starship rocket on April 20. The underside line, he said, is that the vehicle’s flight barely exceeded his expectations and that damage to the launch site was not all that extensive. He expects Starship to fly again in as few as two or three months.
“Mainly the final result was roughly kind of what I expected and perhaps barely exceeded my expectations,” he said. “And I’m glad to report that the pad damage is definitely quite small, and it looks like it will probably be repaired quite quickly. It was actually just good to get this vehicle off the bottom because we have made so many improvements in Booster 9 and beyond.”
Musk spoke for about an hour during a Twitter spaces event, responding to questions from several journalists and spaceflight enthusiasts. For those unable to listen, what follows is a summary of what Musk said.
On the flight
When the rocket lifted off, there have been three engines whose ignition was terminated since the flight software didn’t deem them “healthy enough” to bring to full thrust. That left 30 of the Super Heavy first stage’s 33 engines in good condition, which is the minimum allowable number for liftoff. Musk said he didn’t imagine these three engines were damaged by the gravel and concrete kicked up by the immense thrust created by the rocket because it slowly lifted off from the pad.
“Weirdly, we didn’t see evidence of the rock tornado actually damaging engines or heat shields in a cloth way,” he said. “It could have been, but now we have not yet seen evidence of that.”
At 27 seconds into the flight, engine 19 lost communications concurrent with some sort of “energetic event,” Musk said. This also liberated the outer heat shield from 4 nearby engines. SpaceX engineers are still assessing exactly what this energetic event was.
“So something bad happened at T-plus 27 seconds since the engine 19 lost all communications, and a few sort of explosion happened to knock out the warmth shields of engines 17, 18, 19, and 20,” Musk said. “There have been visible fires seen from the aft end of the vehicle for the rest of the flight, however the rocket kept going. At T-plus 62 seconds, we see additional aft heat shield damage near engine 30; nevertheless, the engine continues to run. After which T-plus 85 seconds is where things really hit the fan.”
At that time, the rocket began to lose its thrust vector control, or the power to steer itself. This led to the initiation of the flight termination system.
Flight termination system
Just before a minute and a half into its mission, the rocket’s flight termination system was initiated to interrupt up the vehicle before it veered too far off target. Essentially, the ordnance on board the rocket detonates to rupture its fuel tanks, resulting in a breakup. Nevertheless, on this case, there was a few 40-second delay between the initiation of the system and the rocket breaking apart.
This time lag posed no questions of safety with the rocket safely offshore, nevertheless it is an unacceptable lag for a system that’s purported to terminate flight almost immediately.
Musk said the issue could possibly be solved with a “longer detonation cord” to be sure the propellant tanks are fully unzipped rapidly. Nevertheless, he acknowledged that working through this issue with the Federal Aviation Administration may take a while.
“The longest lead item might be requalification of the flight termination system,” Musk said. “That is obviously something that we would like to be sure of before proceeding with the following flight.”
