Not very many.
Uh, there's a Newtonian law of physics about equal and opposite reactions... the fact that it is Newtonian probably means that it's wrong because this other guy came along and corrected his math or something? But I think it holds in the general case and explains why you can explode yourself upward.
People invented airplanes first. That may have been important. I remember seeing something about airplanes on a list of common misconceptions so you should not assume strongly that anything I know about airplanes is accurate as opposed to plausible falsehood.
There is no air in space and it's kind of hard to make a capsule that will not let all the air you brought along out but I think maybe less hard than making a deep-diving submarine since that's more atmospheres of pressure, just the other way.
There's also no gravity and this makes drinking and going to the bathroom and writing with pens difficult and also tends to make people throw up.
I don't remember the gravitational constant and since I don't even know how I got here or how far away here is I couldn't assume it was the same anyway but I think you can use that and the masses of celestial objects and... stuff... to figure out where they will be, so you can land on the moon if that is what you are trying to do.
Everything in space is really far away from everything else in space, it takes a long time to get to the moon and way longer to get anywhere else.