robert nelson wrote:

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


They push mass of gas out the back, when there
is no more gas (fuel) left they are worthless.
An ideal solution is to provide thrust from energy
alone, so thrust can be maintained indefinitely
provided the vehicle has energy. To date it
hasn't been done, although many are trying...
-Roman

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