apollo 13 style slingshot?

Question

if you slingshot you r way around a planetoid you have to use the planets gravity to gain speed, this means that u increase kinetic energy, now since you gotta actually break free from its pull of gravity does that mean that whatever kinetic energy u gain would be lost in potential nrg trying to break free? does the planet actually move a little to combat this force?

Answer 1

In a way, yes, the planet moves a little.

You need to know a bit more about how the slinghot effect works.

All planets (in fact everthing) moves in a orbit.

In a perfect slingshot manuver, you approach the planet as the planet approaches you (head on), now, as you circle the planet, you will be captured in it gavational pull, and as you leave the planet, you will have to escape that pull, so you should have the same velocity, right.

No, you also pick up the velocity of the planet in it's orbit, which can be rather significant.

That is a very simplified explination, and unfortunaly, I can't do any drawing show it better, but you should get the idea. . .

Answer 2

The increase or loss of velocity depends on how much time the planet pulls on you, So if you approach the planet while orbiting the sun in the same direction and at the same speed as the planet, go a little past it and slingshot around so your orbit heads more away from the sun, the planet will recede from you in a lot less time than it approached you, and you won't be slowed down as much as you were sped up.

Answer 3

That stumps me too, i did that experiment in a physics class and it didnt work, with the planet being stationary, the rocket or the model i was using to slingshot around ended up falling into the moon about 3/4 of the way around, so i think the moon was moving towards them as they passed it on the left side which allowed them to basically just get around to the back side then just sit there and let the moon walk by in the window and eventually let it fall away as they separate and head for earth.