Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Gravitational catapult and a spacecraft

  1. Nov 3, 2003 #1

    "Another notable thing is that Pioneer 10 used the gravitational catapulting effect of Jupiter. That was the first time that was ever done for interplanetary light. Pioneer 11 followed in its footsteps about seven years later to go out of the solar system."

    That text was taken from:

    Can anyone explain how such a GRAVITATIONAL CATAPULT works?


    Last edited by a moderator: Apr 20, 2017
  2. jcsd
  3. Nov 3, 2003 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It is a fact of physics that if a free body moving through space approaches a massive object, such as a planet or star. The free moving object will be accelerated toward the (shall we say) planet. The path followed by the moving body (say satellite) could be either hyperbolic or parabolic, depending upon its speed and (I believe) angle of approach to the massive body. Both of these paths have the satellite exiting the planet with the SAME speed with which it approached. The satellite will have changed its direction therefore will have a different velocity due to the acceleration of the massive body.

    Now consider what happens as the satellite approaches the planet when planet is itself moving, as in a orbit. Now while the satellite is being accelerated toward the planet it will gain speed due to its path through the planets gravitational well and it will pick up a bit of the planets ORBITAL velocity. This is the sling shot. That bit of planetary orbital velocity that is gained in the trip past. The satellite will lose any velocity gained due simply to the gravity of the planet, but will not lose the fraction of orbital velocity aquired durning the fly by.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook