Posted by Jonathan (68.14.212.239) on October 23, 2003 at 01:52:27:
Hi all, this just occured to me today. Have any of you watched any discovery channel shows on space travel? Ever heard of gravity assit(-ence in launching space craft)? Well, it is well known that to save money on space craft one can give a space craft the appropriate velocity at the appropriate time so that it will fall toward the heavenly bodies (plural because it often uses more than one body during one trip) and end up farther from that body than it started. This means that with tiny energy input one can achieve huge increases in gravitational potential energy! And I have proof too! NASA does it all the time, the most striking being the Voyager and Pioneer space craft, both of which are barely in the solar system any more! Do you know how much rocket fuel that would have taken had they not used gravity assit?! And yet these same scientists call gravity a conservative force field! Addition: I just found these sites that back me up: An oversimplified view at:
http://voyager.jpl.nasa.gov/mission/images/f23.gif
Scoll down to 'History of the Voyager Mission', it's the first paragraph under that heading:
http://voyager.jpl.nasa.gov/science/planetary.html