Yes, that's why I asked. I'm going for a sanity check. It seems like they cant over immediately after staging, and the Starship exhaust splashes all over the leading end of the booster, turning it at a really good clip. I can't see another reason for it to turn so rapidly/violently.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
SpaceX Starship - Integrated Flight Test #2 - Starbase TX - Including Post Launch Dissection
- Thread starter Grendal
- Start date
dhanson865
Well-Known Member
So it looks like 3 engines on stage 1 at 50% throttle isn't enough to keep the velocity from dropping after hot staging. So maybe up those 3 engines to 55% or 60% throttle to give just a little more stability to the push?
Maybe higher than 60% if the starship has a higher mass due to cargo or any other changes for future flights?
Buckminster
Well-Known Member
I think they have to throttle up the booster's three engines to 50% plus enough additional thrust to oppose the roughly 0.7g of pushback that it gets from the Starship at staging. If the booster has 9% of its propellants at staging, then it masses about 500 tons. So we want to give the booster at least 0.7g of additional acceleration to that 500 tons of mass. That's 350 tons of thrust above and beyond. It works out that 350 tons is 50% of three sea level Raptor 2s (ignoring reduction in performance due to altitude). So if they ran six engines at 50%, that would mean that the booster wouldn't decelerate when pushed on by Starship at staging.
They'd have to run six at a bit over 50% because they'd want positive acceleration.
All numbers are suspect, but I think the general idea holds - the booster has to stage with a lot more thrust because Starship pushes back on it with the equivalent of 350 tons of thrust (from Starship's 1464 tons of nominal thrust). The pushback probably starts higher and then fades as the booster turns away from Starship. So SpaceX may have a touchy throttle issue, starting high and quickly throttling back down again. I don't know how precise all this has to be.
As an aside, I noticed that the stack is decelerating by about 0.05g before Starship fires its engines, then maintains velocity while the engines are running and the two ships are connected. So Starship's engines are generating 0.05g while firing through the hot staging ring.
Another chart and analysis from the same poster on Starship ascent profile. His conclusion: When the Ship was terminated, it was at the correct expected speed, altitude and inclination.
Yeah, engines were performing fine... until they weren't.
If it's the front chunk could be header tank sourced fire. S24 onward had both in the nose.
I've also got a 1440 vertical display, and full screen I seem to be able to make out the grid fins rotating rapidly just as the exhaust flare dies down at 7 secs in...
At 6 secs they are still "flat":
And then they quickly rotate... hard to see as the flare goes from being so bright as to obscure the view, to providing high-contrast backlighting, to dying out and making it harder to see the fin, but a second later it looks rotated substantially:
Watching it in motion from seconds 6-8 makes it easier to see...
No major revelations, but good summary of the test: Ars IFT-T Article
Some inersesting tidbits:
Some inersesting tidbits:
- They call it Orbital Flight Test-2 (OFT-2)
- Consumes 40,000 pounds of propellant per second!
- A Raptor has " higher efficiency and lower operating temperatures. This means an engine like Raptor, theoretically, is easier to reuse than any other large rocket engine." Hmm.... Given the incredibly high chamber pressures, and full LOX flow, I wonder how true that is? feels like those might be considerations...
- Deluge system dispenses 100,000 gallons of fresh water in a few seconds... wow.
- FAA has declared a mishap (obvious, but will be interesting to see how long this takes...)
I took it to be the front half of Starship, slowly rolling (not tumbling), venting propellant of some sort. Perhaps from the methane tank, perhaps only the header tank(s). The video shows the flaps coming and going as it rolls. This is a still that I think shows Starship pretty clearly.
Similar threads
- Article
