[Ol' Dan Tucker]

in atmosphere the speed is determined by the power of thrust against basicly air resistance. in space there is no resistance. so is it safe to assume that as long as the rocket is thrusting, the craft will continue to gain speed? and if so, to what end? i cant imagine if there was enough fuel for lengthy burn for the craft to reach light speed... ...or could it??

No.

The speed with which the burned fuel is ejected is finite, so the spacecraft cannot go faster than the exhaust.

[sit-rep]

im just asking... that makes sense in atmosphere, but in space how does a total vacuum determine/receive exhaust pressure/speed?? how does a total vacuum determine if that craft is doing 3 mph or 30,000 mph??

[Neverlift]

“The speed with which the burned fuel is ejected is finite, so the spacecraft cannot go faster than the exhaust.”

Totally wrong.

Thrust is the amount of force NOT SPEED. Rocket engines have pounds of thrust, that is a force. Never heard of speed of thrust. If you indefinitely apply 5 lb. of force on an object in outer space that is beyond any gravity forces, it will keep accelerating, indefinitely.

Force = Mass x Acceleration. Period