> >*>In space there will be no matter to push against
> >*>and it won't work. :o)
> >
> >I agree.

The *suggestion* (NASA patent ?)  is that it DOES work at a reduced level in
a matterless environment but by an as yet unknown mechanism.

> SO WHAT DO THE ROCKET ENGINES  PUSH AGAINST?
> HOW DO THEY WORK?

As Jinx says, rockets effectively push against themselves.
The momentum change in the mass thrown out as "exhaust" is matched by an
equal and opposite momentum change in the rocket itself.

Simple experiment.
Obtain wheeled platform (shopping trolley, luggage dolly or whatever.
Obtain LARGE mass that a person can lift.
Stand / sit /crouch whatever in /on platform holding mass.
Throw mass away from trolley along axis the trolley can move in.
Note that the trolley and the thrower move in the opposite directions.
This will of course work as well in space (ir better as there is no
friction).
This is exactly the principle on which a rocket works.

A gun can be thought of as a rocket where the bullet is the same as the
"fuel" being ejected and the gun is the equivalent of the rocket. The
"recoil" is the transfer of an equal amount of momentum to the gun as is
imparted to the bullet by the chemical reaction of firing. In "space" the
gun would gain velocity in a direction opposite to the bullet direction. On
earth this energy is transferred to the environment. Face West when firing
and the earth spins slightly faster :-)



        Russell McMahon

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