You must work out some way to have a net external force exerted on your ship.
-- If you're close enough to the sun or another star, then you can put up a big sail,
and take advantage of all the electromagnetic radiation or stellar wind it catches.
-- Otherwise, you must eject mass in the direction opposite from the way you want
to accelerate. You can do that by burning rocket fuel and ejecting the hot gases, by
electrically accelerating ions and letting them shoot out the back, by firing bullets
out the back, by spitting, etc.
Yes, that is why they are used in space.
Yes, rockets can accelerate in space. When the exhaust accelerates away in one direction, the rocket accelerates away in the other, as any reaction is balanced by an equal and opposite reaction.
Spacecraft make use of jet propulsion.
much less air resistance.
Energy enough to accelerate the object to an orbital velocity.
The answer is a space-shuttle. So cool, right!
a sponge will have more matter packed in the same space
... to accelerate.... to accelerate.... to accelerate.... to accelerate.
Weightlessness
Weightlessness
Weightlessness
... then it won't accelerate.... then it won't accelerate.... then it won't accelerate.... then it won't accelerate.