5 ms·

Isn't there some way to stockpile the kinetic energy in several passes, instead of only one slingshot, then finally use all of that for a final throw?

guelo 7y ago
The limit is the escape velocity of the orbit.
- hinkley 7y ago
  Not if you have time. And three bodies. If you've achieved escape velocity from the 2nd body (eg, Earth) but not the first body (eg, the Sun) you can keep swinging around the 1st body stealing speed off of the 2nd one each time. Takes some careful orbits and a long time, but NASA does it all the time.
  - dvdkhlng 7y ago
    It would be very cool to have a binary black hole system somewhere in the solar-system. I.e. two black holes in a tight orbit around each other at very high orbital velocities. This could allow for very powerful slingshots to bring probes to interstellar speeds.
    - hinkley 7y ago
      If you have the energy to get to black holes rotating around each other, you probably can build ships that don't need to slingshot. 'Cept perhaps for braking maneuvers.
lukeschlather 7y ago
Not really. The thing is, you're not so much stockpiling kinetic energy as you are using the mass of the body to amplify the force you apply. There is an optimal time to apply that force, which is when you are closest to the body you are orbiting. So what may happen is if you have a low-thrust engine, you will do a burn at the optimal time, then stop and wait an orbit until you reach the optimal time again. But you're not "stockpiling" anything so much as you are just thrusting at the optimal time. And once you reach escape velocity you have to keep thrusting, there is no more opportunity to do another pass.
fsagx 7y ago
You could make multiple passes, if needed, gaining a + delta V each time by designing the orbit such that the spacecraft is on a transfer orbit back to PBH to make another pass. (If, as guelo mentioned, you did not at some point reach escape velocity of the solar system at that orbit.) It would be a very long wait between passes though... Seems like a Jupiter gravity assist would always be much more practical.
hinkley 7y ago
I can't recall which probe, but NASA has used the same body for multiply slingshots. But that's stealing orbital energy from the body you pass in the same direction it's orbiting. I think the mass of the body only matters in how much momentum it has. If you fly by an asteroid you will deflect its course. You could convert the entire mass of earth into spaceships and slingshot them past Jupiter and it would barely register.

guelo 7y ago

The limit is the escape velocity of the orbit.

hinkley 7y ago
Not if you have time. And three bodies. If you've achieved escape velocity from the 2nd body (eg, Earth) but not the first body (eg, the Sun) you can keep swinging around the 1st body stealing speed off of the 2nd one each time. Takes some careful orbits and a long time, but NASA does it all the time.
- dvdkhlng 7y ago
  It would be very cool to have a binary black hole system somewhere in the solar-system. I.e. two black holes in a tight orbit around each other at very high orbital velocities. This could allow for very powerful slingshots to bring probes to interstellar speeds.
  - hinkley 7y ago
    If you have the energy to get to black holes rotating around each other, you probably can build ships that don't need to slingshot. 'Cept perhaps for braking maneuvers.

lukeschlather 7y ago

Not really. The thing is, you're not so much stockpiling kinetic energy as you are using the mass of the body to amplify the force you apply. There is an optimal time to apply that force, which is when you are closest to the body you are orbiting. So what may happen is if you have a low-thrust engine, you will do a burn at the optimal time, then stop and wait an orbit until you reach the optimal time again. But you're not "stockpiling" anything so much as you are just thrusting at the optimal time. And once you reach escape velocity you have to keep thrusting, there is no more opportunity to do another pass.

fsagx 7y ago

You could make multiple passes, if needed, gaining a + delta V each time by designing the orbit such that the spacecraft is on a transfer orbit back to PBH to make another pass. (If, as guelo mentioned, you did not at some point reach escape velocity of the solar system at that orbit.) It would be a very long wait between passes though... Seems like a Jupiter gravity assist would always be much more practical.

hinkley 7y ago

I can't recall which probe, but NASA has used the same body for multiply slingshots. But that's stealing orbital energy from the body you pass in the same direction it's orbiting. I think the mass of the body only matters in how much momentum it has. If you fly by an asteroid you will deflect its course. You could convert the entire mass of earth into spaceships and slingshot them past Jupiter and it would barely register.