Jack56 Ars Scholae Palatinae
7y
607
julesverne said:
Upside:Engine bay leak issue, solved.
Downside:Booster exploded.
Payload bay doors balked.
Ship attitude control lost.
No data on payload deployment.
No data on engine relight on orbit.
No data on Ship reentry.
The list goes on.

I'm sure SpaceX will solve these issues. But the root causes of the failures may negatively affect max payload mass to orbit. And the cadence of failure is picking up. Reason: unknown. But losing key engineers can cause outsized problems. I have no info on this, but given the recent series of backslips, I wonder if any of the most creative thinkers may have jumped Ship(sorry) following Musk's "Roman Salute" and other scumbag actions. I sure as fuck wouldn't want to work for him, despite intense interest in the SpaceX vision.

The main problems have been propellant system & engine leaks. It's new engineering territory. The engine chamber pressure is ~300 bar. The preburners are at >600 bar (>9,000 psi). The turbopumps higher again than that. The wonder is that most things don’t leak. //

Erbium68 Wise, Aged Ars Veteran
3m
1,070
Subscriptor
DistinctivelyCanuck said:
What I'm finding fascinating about the current failure modes on the block two starship is that obviously spacex thought they had a full handle on these from block one: and so many "solved problems" have spiraled into challenging fixes.
Leak issues causing loss of control were obvious in the very first flight that made it to sub orbital: but resolved on the subsequent flights.
Vibration issues causing RUD's: quickly resolved in the very first flights and are back again.
The other interesting aspect: the ground burns at massey's that were designed to identify these failures aren't doing it at ground level. (remember that there was a ground burn test with a near ten minute burn with extensive throttling:
I think we can expect another couple of iterations of those long burn tests soon.

My limited experience in the field of engine development tells me that this is perfectly normal for such projects. The solved problems always come with unexpected caveats. Especially vibration.
An example from ship practice is early reduction gear failures in turbines. All sorts of things were considered, lubrication was improved and the things worked perfectly on long term dyno tests. And then broke up at sea even under good sailing conditions.
The cause was eventually traced to the vibrations from the props caused by interference from the rudders. It was difficult to fix, but fixes were found (flexible shafts, basically).
Despite being so well understood the problem recurs over and over again as new bearing, hull and rudder designs come into use.
There was also a major vibration problem that hit Luftwaffe fighters in WW2. Arguments about defective bearings, reduction gears etc. duly took place. It was eventually traced to the fact that the fuel being used by the test labs was better than that often used at the front, which was messing with spark plugs and causing misfires which resulted in the vibration.
In engines, whether piston, turbine or rocket, just about everything interacts in ways beyond the scope of computer modelling - because until the mechanism is identified, it can't be modelled.