Re: [Phys-l] conservation versus constancy

["David Bowman" <David_Bowman@georgetowncollege.edu>]

Regarding bc's wonderment:

> ...
> bc, who wonders what the KE loss is in the case of "sling shot"
> space probe manoeuvres.

Actually, while the spacecraft is gravitationally interacting with
the intermediate planetary body there is *no* KE "loss" but rather a
KE *increase* as the mutual gravitational potential energy is reduced
and the KE is temporarily increased.  After the interaction is over
and the gravitational PE goes back to the level at large separations
then the total kinetic energy goes back down to its initial
asymptotic value.

Depending on which side of the sun-orbiting planet the spacecraft
passes the planet by on (either passing in front of the planet's path
or passing behind it on the way in to its temporary periapsis) there
can be a net transfer of kinetic energy from the spacecraft to the
planet or from the planet to craft when it and the planet are again
asymptotically far apart.

David Bowman