SpaceX 'Star series' simulations

[eriblo]

The numbers currently on the SpaceX website are 230 t_f for SL and 258 t_f for RVac which lines up fairly well with the I_sp split.

[OneSpeed]

Here is a 'CompariSim'™ of the first two Starship Integrated Flight Tests (OFT-1 and IFT-2), and Crew-7.

Attached are plots from the IFT-2 webcast telemetry, and this simulation, which utilises the IFT-2 events timeline, including all engine start-ups and shutdowns. To produce the simulations, I had to vary the pitch and throttle settings until they matched the telemetry. The fact that the real and simulated plots are so similar, suggests that there were no significant drop-outs or errors in the IFT-2 webcast telemetry.

The simulation confirms that the pitch was ≈ 30° at hot staging, and AoA only 0.2°. From that we can conclude that free-fall would have been -sin(30) or -0.5g on the plots. We can see that the booster experienced ≈ -0.7g for a couple of seconds, so around -0.2g in the reference frame of the booster, enough to cause propellant slosh.

Increasing the booster throttle to around 80% during those couple of seconds may well be sufficient to ameliorate the slosh (it works in the sim ).

[ATPTourFan]

Thank you, OneSpeed, for these excellent sims. So informative!!

[daveglo]

Really appreciate the confirmation (via a darn good sim) that:

1) the booster probably did see negative g, and the associated propellant slosh, which likely contributed to the loss of engines during the boostback burn, and

2) that there is a reasonable expectation that this staging method can certainly be tuned via engine settings to improve the odds for success.

Nice work as always!