In the vacuum of space, aerofoils like those on planes are useless. Instead, propulsion and steering are achieved with rockets. With no air molecules to push on, you may wonder how the shuttle’s rockets keep it moving. But Newton’s Third Law says that every action has an equal and opposite reaction. So, the force created by the shuttle’s engines in expelling the burning fuel produces an equal thrust in the opposite direction. This thrust acts on the spacecraft and propels it along.