Think about it this way. Suppose you have a tube closed at one end,
other end open, and you have a source of gas that has enough flow and
pressure to maintain a fair pressure in the tube.

Now, the force on the tube walls on the cylindrical part (the part
without the end pieces) all cancel out because the force on every piece
is cancelled out by the same force on the piece diametrically opposite.

However, the pressure on the closed end creates a force that is NOT
cancelled out by the open end. So the gas goes roaring out of the tube,
but the force on the closed end 'pushes' the rocket forward.

Now, real rockets have a 'nozzle' that makes better use of the gas
flowing through it, pushing on walls of nozzle. So thrust of rocket
comes from forces on nozzle, and on end of chamber opposite opening in
nozzle.

George Kinley wrote:

Hi,
if there is no Atmosphere, where do rockets that go in Space get thrust from

--
Don Stauffer in Minnesota

webpage- http://www.usfamily.net/web/stauffer