I'm puzzled why Falcon 9 throttles down through Max Q. I can understand why Falcon 9 Heavy (as well as Shuttle, Delta IV Heavy, etc.) does this to reduce aerodynamic loads on the booster attach points. But F9 is single stick. My best guess is that the vehicle velocity approaching Max Q dictates the need for throttle down. Or this is required by Dragon, not the booster? Or if Space X built Dragon and Falcon 'beefy' enough to endure full Max Q, there would be a weight penalties.Sidebar coments:- I just watched the last Delta IV Medium (two SRBs) launch. Didn't hear an RS-68A throttle down comment.- I think the Shuttle was first vehicle to utilize throtte down simply because it had the first throttleable engines.- The original Atlas rocket is an interesting case. It was famous (or infamous!) for it's thin-skin construction. As far as I know it survived Max Q every time with its fixed-thrust engines.Thanks
keeps max q to less than 1000 psf (I think around 700, the same as the Saturn V).
Why does the SpaceX Launch Director give his GO for every Falcon launch at T-45 seconds? Shouldn’t it be earlier in the count?Also, I noticed before the Falcon Heavy Test Flight, the Launch Director gave his GO at T-25 seconds. That’s cutting it close, right?
With the recent weather scrubs of Falcon it got me wondering, is there a limit on how many tankings it can do?
Quote from: penguin44 on 09/17/2022 02:41 amWith the recent weather scrubs of Falcon it got me wondering, is there a limit on how many tankings it can do?Since Elon has said there are no obvious limits to Falcon 9 reuse, then tankings should be included.The number is high, but not infinite. My guesstimate is about 100?
It appears the external cameras on the first stage have some method of clearing the view after entry burn fouling. I can think of a few ways this might be accomplished, but not sure what is used. Rotating shield that moves to a clean spot? That would require a servo or similar which seems odd to me. Is there a reference for how this is done?
Does SpaceX ever put previously flown engines on unflown expendable cores?
What is the use of a entry burn for RTLS, especially FH boosters?The RTLS entry burn start speed (4000km/hr) is less than the ASDS (barge) landing entry burn end speed (~6000km/hr).Info I've gathered from webcast telemetry.RTLS One Web 16 Jan 9 2023Payload mass kg 5900 40x 147.5 = 5900 plus dispenser (1000kg??)Entry Burn start speed 4473Entry Burn end speed 2926FH side booster RTLS USSF-67 Jan 2023Payload mass kg to GEOEntry Burn start speed 4472Entry Burn end speed 3690F9 RTLS ISI EROS C-3 Dec 29 2022 VandenburgPayload mass kg 470Entry Burn start speed 4651Entry Burn end speed 2616F9 ASDS Starlink Dec 17th 2022 CapePayload mass kgEntry Burn start speed 8152Entry Burn end speed 6074 Distance to ASDS km est 656F9 ASDS Starlink 5-1 Dec 28th 2022 CapePayload mass kg 16200 54x300kg Starlink 1.5Entry Burn start speed 8026Entry Burn end speed 5627Distance to ASDS km 660
The altitude and duration of the entry burn is carefully calculated to use the least possible amount of fuel while keeping the heating of the rocket below the safe limit.