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Ira
Carpal Tunnel
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Reged: 08/22/10

Loc: Mitzpe Ramon, Israel
Re: Sling Shot Theory new [Re: groz]
      #6248086 - 12/11/13 11:13 PM

Well wait...in your example it is the gravitational force of the planet that creates the slingshot effect, not the orbital motion of the planet. So, a more massive planet like Jupiter is more efficacious in creating the slingshot effect than a faster orbiting planet like Mars.

/Ira


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Rick Woods
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Reged: 01/27/05

Loc: Inner Solar System
Re: Sling Shot Theory new [Re: Mister T]
      #6248190 - 12/12/13 12:35 AM

Quote:

I always thought "Sling Shot Theory" was:

If you shoot a sling shot at a 700lb. Bengal Tiger often enough you will get him mad enough that he will scale a 20ft wall and eat your *BLEEP*.




That's no theory!


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dan777
professor emeritus
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Reged: 11/16/07

Loc: Indiana
Re: Sling Shot Theory new [Re: Ira]
      #6248992 - 12/12/13 12:44 PM

Quote:

I thought the slingshot effect was due to the gravity of the massive planet, not its speed in orbit around the sun. In that case, why not use a faster moving planet like Mars to create the slingshot, rather than the more massive but slower moving Jupiter?



The term "gravity assist" comes from the fact that the spacecraft must move through the gravitational field of the planet.

The spacecraft picks up velocity because of a transfer of angular momentum from the planet to the spacecraft. If the planet had an enormous gravitational field but was stationary (no velocity relative to the sun) the spacecraft could not increase its speed because the angular momentum of the planet is zero. The final velocity of the spacecraft is based on the vector addition of the planet's velocity and the spacecraft's velocity relative to its trajectory around the planet.

Indeed Mars can be used for gravity assist, but there are several variables to consider. Here's one to ponder, if you want to send a spacecraft (Voyager for example) out of the solar system, then you need to exceed the escape velocity of the sun. At Mars the sun's escape velocity is 34.1 km/s and at Saturn it's 13.6. Voyager used both Jupiter and Saturn for assists.


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llanitedave
Humble Megalomaniac
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Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Sling Shot Theory new [Re: Rick Woods]
      #6250097 - 12/12/13 11:28 PM

Quote:

Quote:

I always thought "Sling Shot Theory" was:

If you shoot a sling shot at a 700lb. Bengal Tiger often enough you will get him mad enough that he will scale a 20ft wall and eat your *BLEEP*.




That's no theory!




I was going to post exactly that, but I deleted it!


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llanitedave
Humble Megalomaniac
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Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Sling Shot Theory new [Re: Ira]
      #6250114 - 12/12/13 11:38 PM

Quote:

Well wait...in your example it is the gravitational force of the planet that creates the slingshot effect, not the orbital motion of the planet. So, a more massive planet like Jupiter is more efficacious in creating the slingshot effect than a faster orbiting planet like Mars.

/Ira




With a more massive planet you can get more of a full slingshot effect at a greater distance. It's still the orbital velocity of the planet that's accelerating you relative to the Sun, but you can get more of that effect from a larger planet without passing quite so close to it. You have more leeway in the precision of your encounter that way -- the aiming requirements aren't quite as unforgiving. Also, being farther from the Sun, there's more bang for your buck from the extra acceleration that you do get.

In principle, there's no reason why you can't use Mars to get you where you need to go, if your timing and precision is right.


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Rick Woods
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Reged: 01/27/05

Loc: Inner Solar System
Re: Sling Shot Theory new [Re: llanitedave]
      #6250670 - 12/13/13 10:46 AM

Quote:

Quote:

Quote:

I always thought "Sling Shot Theory" was:

If you shoot a sling shot at a 700lb. Bengal Tiger often enough you will get him mad enough that he will scale a 20ft wall and eat your *BLEEP*.




That's no theory!




I was going to post exactly that, but I deleted it!




Eh, no guts, no glory.
No pain, no gain.
No... ow!


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medic32v
member


Reged: 09/05/13

Loc: East Tip Long Island (North Fo...
Re: Sling Shot Theory new [Re: Mister T]
      #6251521 - 12/13/13 06:43 PM

Ok let's figure this out. If Mercury was in the same orbit as Jupiter, and they were opposite ends of their orbits. Will each maintain the same velocity. Or would catch up with the other. Or would each have the same velocity.and if not who would overcome whom. And does mass have any involvement in this case. And Groz this mane a tough one.a lot of Pysiics invoked

c. Clear Skies Mike
Thanks all and Clear Skies mikeq


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llanitedave
Humble Megalomaniac
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Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Sling Shot Theory new [Re: medic32v]
      #6251589 - 12/13/13 07:25 PM

If Mercury and Jupiter were exactly the same distance from the Sun, in exactly opposite directions, and moving at exactly the same angular velocity, and there were no other gravitational influences involved, the orbits would not be stable over a long period, because the center of mass of the entire system would change relative to the three. The system's mass would be the sum of the three bodies, and the center of that mass would be offset slightly towards Jupiter since its mass is greater than Mercury's. Therefore Jupiter would be closer to the center of mass of the system, and orbit slightly faster, so it would catch up with Mercury.

If both bodies were the exact same distance from the center of mass, then they would orbit at the same velocity in a stable orbit, although Mercury would always be thousands of miles closer to the Sun than Jupiter would.


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PhilCo126
Post Laureate


Reged: 01/14/05

Loc: coastline of Belgium
Re: Sling Shot Theory new [Re: llanitedave]
      #6254303 - 12/15/13 11:29 AM

To find out more: read " Ambassadors From Earth - Pioneering Explorations with Unmanned Spacecraft " by Jay Gallentine ( University of Nebraska Press)

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StupendousMan
super member


Reged: 08/21/05

Re: Sling Shot Theory new [Re: PhilCo126]
      #6255386 - 12/15/13 10:25 PM

Here is a very simple -- but pretty accurate -- analogy.

a) stand by the side of an empty road with a tennis ball. Gently toss the tennis ball straight across the road toward the other side. The ball will move straight across the road.

b) now, hold the tennis ball again, but this time wait for a truck to approach. Just as the truck passes you, toss the tennis ball in front of the truck. The truck and ball will bounce off each other ... but because the mass of the ball is so much smaller, it will end up flying down the road, ahead of the truck, while the truck slows down by an imperceptible amount.

Ball = spacecraft, truck = planet.

As long as you can arrange things so that a planet is moving in the direction you want to go, this is a really good method of picking up extra speed.


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llanitedave
Humble Megalomaniac
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Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Sling Shot Theory [Re: StupendousMan]
      #6255514 - 12/16/13 12:05 AM

Try not to break the truck's headlight.

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