Timeline for Is there any limit to how many times you can increase velocity by repeated sling shot manoeuvres?
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17 events
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| Aug 7, 2021 at 11:55 | comment | added | Raffles | @Peter-ReinstateMonica It's a good point. I agree that three planets (suitably placed) would allow you to keep cycling round the entre system, and gain speed every on every slingshot. However, 2 planets is actually enough, because of the following two effects. Firstly, you can approach the inner planet roughly at a tangent, so maximum gain from that planet (i.e. more or less a 180 turn around, in the direction of orbit), whereas the corresponding loss from the outer planet will be smaller because you approach it at more of a right-angle. Secondly, the inner planet has a higher orbital velocity | |
| Aug 7, 2021 at 11:50 | comment | added | Raffles | @Peter-ReinstateMonica on your point about needing mega-Earths, certainly a dense rocky planet would give a better max speed (surface escape velocity) than a gas giant of the same mass... however in order to ping-pong you only need that the planetary escape velocity exceeds the solar escape velocity. Once you get out as far as Saturn, the solar escape velocity is around 14 km/s, which is far overpowered by Saturn, which has a surface escape velocity of 36 km/s, allowing you to swing all the way round the planet and back again (or even drop into orbit) e.g. at 20 km/s - way above solar escape | |
| Aug 7, 2021 at 8:46 | comment | added | Mast | @LorenPechtel How about a binary star system? Would it work around both suns there? | |
| Aug 7, 2021 at 1:39 | comment | added | Loren Pechtel | @Peter-ReinstateMonica Two problems. First, bouncing back and forth requires planets with enough gravity that you can make basically a 180 during your turn. That's basically mega-Earths. Second, bouncing back and forth between two worlds isn't going to do much for you anyway. Head on, a 180 is the best gravity maneuver possible. Side on, a 180 just turns you around but you gain nothing. You need at least three bodies to play that dance. We don't have even one such planet here. | |
| Aug 6, 2021 at 7:59 | comment | added | Peter - Reinstate Monica | Your argument is good but I wonder whether it is absolute. If you maneuver accurately enough you could "sling bounce" with ever tighter encounters between planets inside the Solar System; an orbit around a planet that is tight enough should still change your vector. Enough to reach another planet? | |
| Aug 6, 2021 at 7:03 | comment | added | gerrit | @jamesqf I know; my comments were not entirely serious for getting to Alpha Centauri. | |
| Aug 5, 2021 at 19:57 | comment | added | jamesqf | @Michael: The Voyagers are pretty good examples. Both had exceeded solar escape velocity by the time they passed Saturn. Voyager 2 was only able to go on to Uranus & Neptue because of a fortuitous orbital alignment. (See "Grand Tour".) It would have been just about impossible to go back to Jupiter. | |
| Aug 5, 2021 at 19:51 | comment | added | jamesqf | @gerrit: But the question's about just getting to Alpha Centauri. Presumably the OP wants to stop there, rather than just doing a quick flyby - Galileo/Cassini vs Voyage/New Horizons. | |
| Aug 5, 2021 at 19:11 | comment | added | zephyr | This is the best answer. You're limited by the number of slingshots before you reach the solar system escape velocity. You might be able to sneak one or two more in after that, but once you reach escape velocity you have nothing more to gain really. | |
| Aug 5, 2021 at 15:56 | comment | added | gerrit | @jamesqf Exploring the galaxy is not a business for those in a hurry. It may take half a million years to get up to speed, but it will save time and fuel getting to the other end of the galaxy ;-) | |
| Aug 5, 2021 at 15:51 | comment | added | jamesqf | @gerrit: But the problem with that is that it takes 10K years or whatever before you reach the next system :-( | |
| Aug 5, 2021 at 14:34 | history | edited | Loren Pechtel | CC BY-SA 4.0 |
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| Aug 5, 2021 at 9:12 | comment | added | CuteKItty_pleaseStopBArking | It just becomes even more inconvenient. You might need to slingshot off planets (or better, stars) of other systems. | |
| Aug 5, 2021 at 8:34 | comment | added | gerrit | You could slingshot around the next system! | |
| Aug 5, 2021 at 8:07 | comment | added | Michael | They did those slingshot maneuvers on their way out, so to speak. Once you’ve reached escape velocity you’ve (by definition) left orbit and can’t stay in orbit to do more and more slingshot maneuvers. | |
| Aug 5, 2021 at 7:35 | comment | added | Raffles | If that was true Mariner / Voyager wouldn't have been able to sling-shot after they reached solar escape velocity, but they did. E.g. see en.wikipedia.org/wiki/Gravity_assist#/media/… | |
| Aug 5, 2021 at 5:30 | history | answered | Loren Pechtel | CC BY-SA 4.0 |
