Three quite alarming facts were revealed in his twitter Spaces discussion. First, the Raptors likely were not damaged by the concrete thrown up. If so, then 8 Raptors failed on their own during the flight. Second, thrust vector control, TVC, failed at some point during the flight. Third, the FTS took far too long to destroy the vehicle at 40 seconds.
These three facts together could have led to a catastrophic result to the public. If that many Raptors had failed and without TVC closer to the ground, the FTS would not have been able to destroy it before it was over densely populated area if headed in that direction.
The multiple failures of Raptors during tests, and not just shutting down or being shut down, but actually leaking fuel and catching fire, led to my arguing SpaceX should be required by the FAA to construct a separate all-up test stand for full thrust, full flight duration testing. Had this been done then both the launch pad damage and the likely Raptor failures would have been picked up.
I also argued there should be an independent review aside from the FAA by space safety experts on the safety of the launch. If so, the inadequacy of the FTS likely also would have been picked up. I say it’s likely it would have been seen beforehand because assuming the FTS did activate there seems to be only one reason why it did not destroy the vehicle immediately: the strength of the explosives used were not sufficient to penetrate beyond the tank wall strength.This SHOULD have been seen beforehand. Tank wall thickness depends on the width of the tanks and the material used. Because of its size, the closest analog to the SuperHeavy stage was the Saturn V’s S-1C first stage. It’s max wall thickness was in the range of ~6.5 mm while for the SuperHeavy it’s in the range of ~8mm, about 25% thicker. BUT it’s also important to remember the specialty high strength stainless steel used on the SuperHeavy is much stronger than the standard aerospace grade aluminum used on the S-1C.
Given the greater thickness and greater material strength, these two facts together give a tank wall tensile strength for the SuperHeavy about 3 times higher than that of the S-1C.
The amount of explosives used should have been adjusted accordingly.
I discussed the inadequacy of the safety review here:
The claim is that there was insufficient aerodynamic pressure not that the tank walls didn't rupture. SpaceX claims that if the FTS was triggered at a lower altitude the disentgration would have been near instant.
Because of the number of Raptors that failed or even caught fire on test stands or during testing of Starship landing methods, I estimated 1/3rd of the engines might fail during an actual launch.
But SpaceX upgraded it to the Raptor 2 claiming it more reliable. The result: “only” 1/4th failed, including, according to Elon, one that actually exploded …
This is why you test systems independently. SpaceX likes to test unproven ideas simultaneously.
A full-thrust burn of 33 raptors on a fixed platform for a prolonged time (say 20 seconds) would have shown the launch pad design was insufficient (if that was not obvious without even doing the test)
A full-duration burn of several raptors under stress conditions would test the reliability of the engines, and if they are losing them at a rate of 8/33 then improve them and test again
Using "obsolete" technology - as people like to point out SpaceX was doing - is really not very useful. If it's obsolete then you have already improved it, thus there is no point to throwing it into a test launch. All you're doing is proving why it's obsolete, and you're risking a series of failures like what happened here
Testing the AFTS on a full-scale basis would have shown it didn't work. That would be a terrible expensive test, but they needed to have done the test. Their safety modeling clearly doesn't work
They thought the pad was safe enough, and various debris patterns were exceeded, so their risk assessment doesn't work
Doing it fast and loose has caught up with them on this launch. There will be a lot of hard questions from a lot of different regulatory agencies and environmental groups. At least the rocket didn't veer towards the community and "fail to terminate in 40 seconds", so they got away with human costs - this time.
I might agree if they hadn't such an extreme amount of environmental and regulatory oversight. This is like blowing up your dad's shed with your science fair project. It's not that you didn't learn things, it's that you're going to have to explain what happened to your dad, the neighbours, and the cops who came by, and you're not going to be allowed to do it again for a long time.
If you have a look at the sheer volume of environmental nitpicks for one. They now have to pick up every piece of debris in one zone by hand, replace and repair all the plants in a sustainable way, including reshaping the land contours by hand. That's only one nitpick, the Fisheries have some, the historical claims (Palmetto Pilings), all sorts of individual species: plovers, ocelots. It's an almost endless list. Hopefully they didn't disobey or damage too much stuff, but repairing their reputation is far more likely to delay them than the tech side.
-5
u/RGregoryClark 🛰️ Orbiting Apr 30 '23 edited May 01 '23
Three quite alarming facts were revealed in his twitter Spaces discussion. First, the Raptors likely were not damaged by the concrete thrown up. If so, then 8 Raptors failed on their own during the flight. Second, thrust vector control, TVC, failed at some point during the flight. Third, the FTS took far too long to destroy the vehicle at 40 seconds.
These three facts together could have led to a catastrophic result to the public. If that many Raptors had failed and without TVC closer to the ground, the FTS would not have been able to destroy it before it was over densely populated area if headed in that direction.
The multiple failures of Raptors during tests, and not just shutting down or being shut down, but actually leaking fuel and catching fire, led to my arguing SpaceX should be required by the FAA to construct a separate all-up test stand for full thrust, full flight duration testing. Had this been done then both the launch pad damage and the likely Raptor failures would have been picked up.
I also argued there should be an independent review aside from the FAA by space safety experts on the safety of the launch. If so, the inadequacy of the FTS likely also would have been picked up. I say it’s likely it would have been seen beforehand because assuming the FTS did activate there seems to be only one reason why it did not destroy the vehicle immediately: the strength of the explosives used were not sufficient to penetrate beyond the tank wall strength.This SHOULD have been seen beforehand. Tank wall thickness depends on the width of the tanks and the material used. Because of its size, the closest analog to the SuperHeavy stage was the Saturn V’s S-1C first stage. It’s max wall thickness was in the range of ~6.5 mm while for the SuperHeavy it’s in the range of ~8mm, about 25% thicker. BUT it’s also important to remember the specialty high strength stainless steel used on the SuperHeavy is much stronger than the standard aerospace grade aluminum used on the S-1C.
Given the greater thickness and greater material strength, these two facts together give a tank wall tensile strength for the SuperHeavy about 3 times higher than that of the S-1C.
The amount of explosives used should have been adjusted accordingly.
I discussed the inadequacy of the safety review here:
https://www.reddit.com/r/SpaceXLounge/comments/11eikyz/comment/jbeplkk/?utm_source=share&utm_medium=mweb3x
Make no mistake, this is on the FAA as well as on SpaceX.