SpaceX launch Thursday - using used booster, a milestone

[PottedMeat]

What's all that smoke from coming out of multiple vents in the rocket shortly before takeoff?

liquid oxygen boiling off from the 1st and 2nd stage tanks - they load it as close to launch as possible so its as dense as it can be

 

[Darwin333]

What's all that smoke from coming out of multiple vents in the rocket shortly before takeoff?

Pretty sure it's liquid O2 boiling off but that is just a guess.

 

[Darwin333]

They've said they might try it when they test-launch Falcon Heavy.

Wow, that would be awesome. I would have thought the 2nd stage was going too fast and not have enough room for the extra fuel to make it feasible.

 

[Thebobo]

What's all that smoke from coming out of multiple vents in the rocket shortly before takeoff?

Not my words I just copied from a google search with your words. I'm a lazy typer copy paste is easier. :0

"This occurs when cryogenic boosters are used (Liquid Oxygen / Liquid Hydrogen) - as these warm up on the launch pad, some of the liquids boil and to release pressure, bleeder valves allow this gas to escape. If it remained within the boosters, there is a risk of the pressure blowing seals or damaging other components."

http://space.stackexchange.com/ques...-smoke-that-comes-from-a-rocket-before-launch