Where does a space probe get energy from in a slingshot maneuver?

[simon009988]

when space probes pass planets and gains speed via the slingshot effect; where does the extra energy come from? will it not violate the laws of thermodynamics? I know it doesn't but why?

 

[mathman]

The extra energy comes from the planet it's passing. It will be essentially umeasurable since the planet is so much bigger than the probe.

 

[Intuitive]

If a butterfly is flying against the Earths rotation it will have the influence of slowing the Earths rotation by the Butterfly's drag coefficient while flying on the micro scale, the spin loss is so small that it would be difficult to detect but not mathmatically, but the reverse can also happen in which if the Butterfly is traveling with the Earth's rotation.

 

[Integral]

As the probe falls into the planets gravitational well it is pulled along with the planet in its orbital motion. It is this extra velocity that the probe takes with it as it leaves the planets gravitational well. All velocity gained due to the gravatational well is lost on exit, the orbital velocity remains, this is the slingshot effect.

 

[Tide]

BTW - it is entirely possible for a spacecraft to lose speed as it passes by a planet. You need to set up the right conditions for it to acquire energy.