So I just learned what Terminal Velocity is, that gravity pushes down as much as the air molecules are pushing up, meaning that it reaches as fast as it can when it reaches that point (terminal velocity) and will not go any faster.
With no air in space to stop the “pushing up” can things increasingly build up speed with not cap point?
I tried googling and it says this “The only terminal velocity in space is the speed of light. For anything moving more slowly than the speed of light the limiting factors are the specific impulse (the force applied multiplied by the time it acts) and the mass of the object, which together determine the acceleration and the time that acceleration acts.”
But I don’t really understand that, I don’t understand “specific impulse (the price applied multiplied by the time it acts)” what does “acts” mean?
Also I understand there is also no gravity in space, but I know that planets can exert gravity without actually pulling the object into its atmosphere…..
Can someone explain this to me in layman’s terms??
In: Physics
> With no air in space to stop the “pushing up” can things increasingly build up speed with not cap point?
Other than the speed of light being an absolute limit, yes. Spacecraft travel at speeds very much higher than any Earth based vehicles could achieve; the ISS is orbiting at about 7.6 km/s or about 17000 mph.
> the specific impulse (the force applied multiplied by the time it acts)
That is the definition of *impulse*, not specific impulse. The specific impulse is the impulse per unit mass of fuel/propellant burned. Another way of putting this is that the propellant burn rate multiplied by the specific impulse gives you the thrust created by a rocket. Specific impulse is therefore a measure of the fuel efficiency of a rocket engine.
The specific impulse doesn’t provide an absolute limit on how fast a spacecraft can go but it does impose a practical limit. The reason is that the amount of fuel required [goes up exponentially](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) with the desired velocity. Therefore, for a given rocket engine, there’s only so fast you can make it go before the rocket becomes impracticably large.
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