- aditya mehrotra.

# some fun facts: rocket engines! [funsies]

So remember a few posts ago where I was trying to simulate like how much force comes out the bottom of a rocket engine, trying to determine force of thrust on a skycrane-like spacecraft.

Turns out this isn't really the right way to think about rocket science. __https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation__

So rockets work by shooting out some mass from the engine at a certain amount of velocity, this mass and this velocity is usually know, so what happens is most rocket engines are rated in terms of the *impulse *delivered. Not the *force of thrust *they generate. We talk about force of thrust because it's easier to conceptually understand like, okay force pushes rocket up, but that's not exactly what happens right? What happens is rocket science is really conservation of momentum and we need to think about it in that way more than in the force of thrust way. Now of course, we can convert the impulse into a force*time and get the acceleration of the rocket and etc...

We can use this simple equation to size rocket engines: remember it's *design *we want a certain change in velocity in a certain change in time (average acceleration), so we can design engines that way.