[ELI5] Why do rockets have to go around in orbit and do a bunch of squiggly maneuvers to get to the moon? Why cant they just go in a straight line?

Question

And by straight, i mean, just… Point the nose of the rocket towards the moon and keep steering till you get there….

In: Physics

Answer 1

They could but it’s harder to do.

One of the biggest problems with rockets is that fuel weighs a lot. Any fuel you want to use during the flight has to be lifted up off the earth. If you want to lift more weight then you need more fuel. But that extra fuel adds weight so you need more fuel to lift it.

For every kg of fuel you want to get into orbit you need 5kg more fuel at the start of the flight. (Not an exact number, the maths behind the exact increase gets complicated). More fuel means a bigger, more expensive rocket.

If you want to keep the size of the rocket under control you want to minimise the fuel used once you are in space. Those curvey line routes use less fuel because they let gravity do a lot of the work.

Edit-A quick Google indicates that it’s closer to 10kg of fuel at the start for every extra kg of fuel/people/ship you want to get into orbit.