I was in a discussion regarding the time it took to get to the speed of light with a constant acceleration of 1g, and the time was something close to a year. (ignoring all the other major factors ). Just from a Newtonian perspective, if you have a 100kg rocket putting out 900N of thrust, you will get 1g of acceleration. now, say you get up to 10,000mps and you shut down... you are in spacing going 10,000mps.......(ignoring any pull of gravity) now, you fire up the engine... you instantly produce 900N of thrust , but do you still have 1g of acceleration? if so, how does the rocket know it is going 10,000mps or if it is at a stand still? and if it doesn't... then how does it figure that if you are going 10,000mps, it going to take a LOT more energy to produce that thrust at speed than if it was at standstill, relative to its starting point. the equations say this ... we know this to be on the surface of the earth with vehicles with limits to power (acceleration and force go down with velocity if power is constant) So, do rockets have the same issues in following laws . and if so, can i get a good explanation? It just seems like if im at 10,000mps and i push a bowling balll rear ward with 100N of force, i should cause 1m/s/s of acceleration of my 100kg rocket added to however fast we are traveling. ... i know this is not correct, so im asking you all why. thanks!