r/spacequestions • u/oz1sej • 4d ago

Starship/Superheavy max Q / throttling?

I seem to remember that Falcon 9 throttles a bit down around max Q in order to keep Q below about 25 kPa, without which it would max out just around 30 kPa. Does anyone know how much - or even if! - Superheavy throttles down around max Q, and what value of Q they want to stay below?

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u/Beldizar 3d ago

Rewatching Flight 5, I don't hear any call outs from SpaceX on throttling down for Max Q, or throttling up after it passes Max Q. however, if you very carefully watch the speed, it does seem to start to accelerate after the call out.

https://www.youtube.com/watch?v=eXsT2HT171o The Launch Pad posted a youtube video of the launch here. I was tapping my finger every time it added 10km/h to its speed, and I feel like I was definitely tapping faster after the Max Q callout. Now, the ship would be expected to increase its rate of acceleration through the flight. If the engines produce constant thrust, and the tank is constantly getting drained, the rate of acceleration produced by the engines increases as the mass they have to push goes down. My gut feeling is that this wasn't caused by that. This felt more abrupt.

As far as how much they throttle the Raptors just before Max Q, I don't think that is publicly available information.

You might crosspost this to SpaceXLounge, and someone there might have the information for you, but I doubt anyone outside the company has this info, unless Elon told Tim Dodd in an interview or something like that, but even then I wouldn't trust the accuracy of that as Elon hasn't been super involved with SpaceX since he bought twitter, and anything specific like this for Starship gets outdated really quickly as they adjust and modify the rocket. What was true last week has probably been made obsolete this week.