At engine start and the first meter of liftoff, is the tower still pumping fuel into the rocket?

[EzinX]

At liftoff (16 minutes), you can see flexible hoses still attached to the rocket. Is the rocket still being provided with fuel/oxidizer (to replace that burned up at engine start and the fuel/oxidizer to get it the first meter up) and power (so you can use smaller batteries) until the very instant the hoses break loose?

This would make logical sense, to eek out that last little bit of dV by making sure the tanks are at capacity as it clears the tower, but the fuel flow rate is so immense I'm not sure how practical it would be. Edited January 14, 2015 by EzinX

[xenomorph555]

I highly doubt it, that would be very dangerous and difficult. Probably just electrical cables.

[Mazon Del]

I'm pretty sure those are fuel hoses, but they only disconnect them at a point of no return because there are a variety of scenarios under which the launch could be scrubbed and they need to empty the tanks in a hurry.

Thinking about it, I'm actually pretty unaware of any major launch that was given an in flight problem because say, the fuel hoses failed to detach. I know one of the early SpaceX launches scrubbed in the last seconds (the engines lit and everything) because of an issue with the hoses detaching incorrectly.

[Bill Phil]

Aren't the engines ignited first, then clamps release? Then the hoses probably aren't pumping fuel for the last few minutes of the countdown.

[Nuke]

this is probibly because of boiloff. you need the hoses to constantly top off the tank. at some point in the countdown the valves are closed and the tanks sealed. i think they leave the hoses attached in case there is a hold up and they need to top off the tanks some more.

[FishInferno]

pretty much all rockets wait until the point of no return to detach from the fuel supply. If the hoses on a F9 didn't detach they would probably be ripped off by the force of the rocket

[meve12]

That sounds like the exhaust would set the hoses (and the fuel inside) on fire if they did that. So probably no.

[magnemoe]

Aren't the engines ignited first, then clamps release? Then the hoses probably aren't pumping fuel for the last few minutes of the countdown.

Problem is that the engines uses far more fuel than the pipes can provide.

[Nuke]

much of those tubes are insulation so their flow rate is miniscule. it probibly takes hours to fuel up a rocket.

[Bryce Ring]

Can anyone else see a Stormtrooper.

[softweir]

this is probibly because of boiloff. you need the hoses to constantly top off the tank. at some point in the countdown the valves are closed and the tanks sealed. i think they leave the hoses attached in case there is a hold up and they need to top off the tanks some more.

My guess is they are there to carry boiloff away, rather than to replace it. After all, you really don't want clouds of high-concentration oxygen and fuel hanging around if you can avoid it.

[EzinX]

My guess is they are there to carry boiloff away, rather than to replace it. After all, you really don't want clouds of high-concentration oxygen and fuel hanging around if you can avoid it.

What's the big white cloud of mist, then? With the Falcon 9 launches, that rocket uses kerosene(RP-1) and LOX. RP-1 is just a more refined variant on jet fuel (according to Ignition, specs are very loose and it's just been tweaked to have less clogging of the nozzles). So the fuel must stay in it's tank. I don't think letting LOX boiloff into the air causes any harm.