Re: Slingshotting ships with gravity wells in SJ

> >The so-called "slingshot maneuver" is a spectacular and dangerous trick
>to
> >gain extra speed by dipping into a planet's gravity well, orbiting the
> >planet for a short time, and then escaping it at just the right point
>that
> >it adds momentum to your flight. It was popularized by 2001: A Space
> >Oddyssey, and Star Trek at certain points. It's not the sort of thing you
> >want to do on a regular basis.
>
>NASA has utilised planetary slingshots on most missions that go past a
>planetary body (or even the moon).  The savings are enormous.  I can't
>exactly remember the first mission on which this was done (I think it may
>have been Voyager, around Saturn), but I do remember something like the
>mission time being cut from 7 years to about 3 years (to reach a particular
>point further out in space).

Though, the ones that go past planetary bodies (everything but the moon so
far) are all unmanned. It is probably less likely that they'd use it for a
manned flight, or so I assume in my ignorance.

>One thing wrong with your basic ideas of 'a certain time in orbit give a
>certain Interstellar Speed' is the amount of speed you can get out.  This
>has *nothing to do* with the amount of time spent in orbit around a body.

Minor details...Keep in mind I'm no physicist, and I was preaching what I
remember from reading  the 2001 book. Notice I didn't say escaping at the
right time, but the right point. It is all a matter of gravity, and it's not
like you're absorbing gravity like a sponge or anything, you're letting it
pull you in the right directions. Making it let go is tricky...

>It has everything to do with how close you approach the body.  The increase
>in speed comes from the force the craft feels as it approaches the body,
>and the closer you get, the faster you go.  Also, as you move away from the
>body afterwards you lose speed as it is trying to pull you back.  *IF* you
>do it right then you can come out of the whole encounter with more speed
>than you went in (basically, you come out in roughly the same direction as
>the planet is moving through space, and you get a bit of extra speed
>because of relative motions).

Ah...The perfect machine...output = input + X...


~George Lavalle

"Caelum videre iussit, et erectos ad sidera tollere vultus."

He bid them look at the sky and lift their faces to the stars.

~Ovid.

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