The telemetry shows 1-1.5 second delay. However, clamp release is after some (all?) are lit.
OK so there was a delay/staggered engine lights... I thought I had seen that, with the discussion that the engine bells for the SL Raptors are practically touching the HSR dome, so it's nice to avoid blasting them at point blank range.
I think it aligns with clamp release. Likely, all engines were running then with sea level splayed outward.
Ah, so the engines lights were staggered by 1-1.5 secs, but all prior to release.
1) It seems they might have been high output. Really rough numbers: Starship loaded = 1500 tons, Booster 500 tons, with 350 tons thust, 2G momentary deceleration = 2*500+350 = 1350 tons from Ship. Could also look at Manley's slow mo for Ship acceleration
I did a spreadsheet based on the telemetry. Rough numbers at two second intervals suggest that they were throttling up for roughly 10 seconds after staging. The initial thrust looks to be about 30%, then it jumps to 60% after two seconds, then ramps linearly to 100% over the next eight. The 30% number would be contributed to by the gimballed sea level Raptors, but it could also be that SpaceX wanted them that low, and there's undoubtedly sampling error.
Cool, did that take into account pitch and gravity?
50 years ago I could do integrals but then I stopped thinking about calculus so not going to attempt it now!
The acceleration numbers are just based on change in velocity. I was only interested in the ability of Starship to move away from the booster. I didn't even notice the Starship pitch diagram.
I don't follow. I tracked changes in velocity at the point where it started increasing after staging (stack acceleration dropped to zero at one point). Starship fired its engines, which accelerated the stack a touch, then separation. The velocity increased for 10 seconds, then leveled off. What other data are we unable to extract?
Throttle levels at separation. One second at 50%, one second at 80% looks like 65% on a 2 second scale (illustratively).
How did you figure this out? Hopefully not from the animation !
Well, sure. I was content to just get into the ballpark. I could have gone frame by frame for more accurate numbers, but I didn't figure we cared that much.
Screen grab, then use GIMP to measure the angle. It was the most straightforward way to get it.
From the animation on the bottom, correct? That animation I believe is not even close to reality. It is a a very coarse approximation just to give an idea.
Why do you believe it to be so inaccurate? What other source of information would I use?
All true. There are lots of factors at play here. Booster needs to keep its acceleration high enough to keep the propellant settled, which requires less thrust if Starship is also at reduced throttle during separation. Conveniently (and counterintuitively), halving Starship's acceleration relative to Booster does not double the amount of time it needs to achieve a given separation distance; it only increases it by about 40%. There's a wide variety of parameters SpaceX can play with, and probably a wide range of solutions that will be reasonably close to optimal. I'm looking forward to seeing their analysis and how they choose to solve it for IFT-3.
To be clear, when you say "initial thrust looks to be about 30%", that's 30% of the total thrust, not those engines throttled at 30%, which I assume you are saying, as I don't believe Raptors can throttle that low.
Correct. I was specifying thrust, not throttle. There's no way for me to know the throttle level based on acceleration in such a complex environment.
