Vacuum of space and a balloon

[Rakaydos]

One way to think of a rocket... the rocket isnt "Pushing off" anything the way a swimmer might. But when the fuel explodes (and it is exploding, in very controlled fashion), the fuel pushes off the rocket, pushing the rocket away from the fuel.

When you shoot a gun, you get a kick of recoil- not because the bullet is "pushing off the air", but because the bullet is pushing off the rifle. the GAU8 is a aircraft mounted weapon so powerful and firing so fast, it's recoil acts like a rocket that can stop the aircraft (A10 warthog) in flight.

Edit: related reading: http://what-if.xkcd.com/21/

Edited July 10, 2014 by Rakaydos