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SpaceX Starship - Integrated Flight Test #2 - Starbase TX - Including Post Launch Dissection
- Thread starter Grendal
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Both at 00:52 and at 01:18 we see shots from a camera mounted on top of Booster looking down. This is the only one released so far that I believe has shots from the rocket itself.
LOVE IT. As @Electroman noted we briefly got some new views from the vehicle, and at the end a much clearer image of the ship explosion; just the expanding gases but better than before. Really laughed out loud at the happy smiles in the control room when the vehicles did their RUDs.
It only occurred to me when I watched those sections again that they show the grid fins, and they are not stowed / stowable. Would seem to add a lot of air resistance even when aligned axially!
From Elon's talk: the reason Starship didn't reach orbit was that they vented liquid oxygen to match a payload carrying profile. And the oxygen caused a fire and explosion.
I thought he meant that they vented O2 during the burn to orbit because there was no payload and there was going to be too much LOX onboard at the planned end of the burn; if there had been a payload there would have been no need to vent.
Remember that we were wondering why the oxygen in the Starship was falling so fast right at the end? I assume that's the venting they were talking about. I'm not sure what significance having extra oxygen onboard has to the flight, but they clearly didn't want it in the tanks. Perhaps something about how the tanks pressurize. Anyway, the oxygen level fell quickly and shortly afterwards we saw a big puff, which I assume was Starship losing its lower half.
The velocity vs propellant use was off due to less mass, so they were venting to match the values expected during reentry. Since it's autogenously pressurized they had to do this while the engines were running.
Fire, then explosion. Dumping large quantities of LOX could generate a local atmosphere to support combustion of any oxidizable materials. Engines cut off first so maybe wiring/ avionics were taken out?
Nah, wouldn't breakup on reentry
Ah. I wasn't thinking about the role of mass during reentry. Having extra mass would retain a bit more velocity, and the center of mass would be screwed up, with the latter probably the greater concern. I can see how that would be bad.
The statement about autogenous pressurization is saying that they wouldn't be able to generate enough pressure in the tanks to vent unless they had the heat from the engines to boil it off?
I also thought that they could have put a partial propellant load into Starship from the start, but that would probably throw off the entire launch, and it wouldn't give them the data that they actually want anyway.
Yeah, screws up ballistic coefficient and terminal velocities. Plus slosh. Main tanks would theoretically be empty at landing and only the headers would have propellant. (is reentry on headers?)
Right, they need the bleed gas from the engines to pressurize the tanks. Without that, pressure collapses quickly even without dumping volume.
Right. Need as close to normal stack mass at launch. 100 tons difference at liftoff is a much smaller fraction than 100 tons at second stage burnout (booster may be a bit overweight also)
This is just another case of my not thinking something through. They can't just flow LOX past hot engines. Something has to cause that flow, and something has to oppose the cooling that the LOX would apply to anything it touched. So you run the engines to make sure the LOX flows and so that it constantly has a source of heat to boil it.
When you say pressure collapses quickly without it, I assume that you mean that it would drop as the volume of LOX in the tank goes down while the engines are running.
There's no reason to use an expensive mass simulator (remember, 100 tons or so - the dry mass of a Starship) when all you have to do is vent some oxygen. The best mass simulator is no mass simulator.
Clever in retrospect. Carry 100 extra tons of oxygen and vent to simulate payload delivery.
Well, unless it blows your ship up. lol.
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