@S1-A.ARPA:host.MIT-MC.ARPA (05/10/85)
From: king@Kestrel.ARPA In what follows I will assume that the traveler wants to enlarge his/her/its orbit (No Carbon Chauvanism!) Heuristically, you gain in two ways from a gravity slingshot: 1> Suppose you don't ignite your rocket, but you pass the massive object on its trailing side in its orbit. You get a forward component to your velocity vector. In the object's frame of reference, your speed remains the same but your direction has shifted "forward". 2> If you accelerate at perigee, you add to your speed. You could have done that burning anywhere, but in addition to the additional speed YOU LOSE LESS SPEED CLIMBING OUT OF THE GRAVITY WELL THAN YOU GAINED GOING IN, BECAUSE YOU CLIMB OUT FASTER THAN YOU WENT IN. -dick
brent@phoenix.UUCP (Brent P. Callaghan) (05/14/85)
Jupiter must be a very attractive gravity well to NASA mission
planners. I remember a couple of years ago a NASA/ESA combined
mission using two identical spacecraft was planned and
subsequently canned.
The spacecraft were to investigate to solar magnetosphere from
above and below the north and south poles of the sun
( out of the plane of the solar system).
So where did they plan to launch the spacecraft ? ... out to Jupiter !!
Each spacecraft was to get a combined plane change and slingshot
in opposite directions back to Sol.
I hope they made arrangements for mutual overtaking on the
back side of Jupiter. :-)
--
Made in New Zealand --> Brent Callaghan
AT&T Information Systems, Lincroft, NJ
{ihnp4|mtuxo|pegasus}!phoenix!brent
(201) 576-3475pearse@hound.UUCP (S.PEARSE) (05/14/85)
I have read a lot of sci-fi books which use the principle of "Gravity Slingshots". Could someone explain from a net-energy point of view how this works? I know you don't get something for nothing. When a satellite approaches Jupiter, it gains energy from the approach, but as it departs, it loses just as much. Where is the net gain in velocity=energy? Is it from Jupiter's orbital velocity? Thanks, -- Steve Pearse ihnp4!hound!pearse
henry@utzoo.UUCP (Henry Spencer) (05/16/85)
> Jupiter must be a very attractive gravity well to NASA mission > planners. I remember a couple of years ago a NASA/ESA combined > mission using two identical spacecraft was planned and > subsequently canned. No, only NASA's half of it was canned, unilaterally and to the great displeasure of the Europeans, who had thought that a US promise meant something. The European probe, now named Ulysses (used to be International Solar Polar Mission) is going ahead. The US is supplying the launch free as a consolation prize. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry