Timeline for How can I move a planet?
Current License: CC BY-SA 3.0
21 events
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| Apr 28, 2017 at 11:29 | comment | added | Steve can help | There's another major problem with this concept - what do you do about the fact the earth needs its moon in its current orbit in order to stabilise its spin? Even if you're technically capable of moving the earth with gravity-assist maneuvres like this, you would not be able to do that without radically interfering with the moon's orbit, especially given that you'll probably want to be shifting the earth along the solar system's normal plane of motion. You'd accidentally annihilate the earth not long after your first or second pass. | |
| Jan 26, 2017 at 18:20 | comment | added | Bill K | Given enough time, there is an awesome story line in this solution. With good enough computer model of your system you should be able to calculate that if you were to set off a bomb at a specific time and location on a specific comet the comet would bump these asteroids out of place in such a way that they will disturb these two moons which will alter their planet's trajectory in such a way that it will slingshot your planet in the specified direction--a giant chain-reaction. There are a whole bunch of problems with this (like taking centuries to set up), but it seems interesting as a story. | |
| Jun 23, 2016 at 22:16 | comment | added | JDługosz | The idea of transferring between two planets, rather than supplying all the energy, needs to be made clear in the text. Your illustraction and all but one burried statement are just about slingshots in general. | |
| Jun 23, 2016 at 22:01 | vote | accept | HDE 226868♦ | ||
| Jun 22, 2016 at 1:02 | comment | added | Aron | @user21914 The kinematic equations are teh same as if you bounced it off the planet. Newtonian mechanics is Newtonian mechanics. I used the word bounce because the momentum change is EXACTLY the same as if you bounced the New Horizon off the planet. This highlights a) How many flybys you need b) You can't reuse the probe, because they get SMACKED out of the star system in a few fly bys. The result is that you need a planet's worth of mass in probes to do it. | |
| Jun 21, 2016 at 23:25 | comment | added | ckersch | @user21914 Yes, but 'adjusting the trajectory' of a ball of rock that size takes a tremendous amount of energy, and you need to do it thousands of times. Making all of those momentum transfers requires precision flying a ball of rock that's only four orders of magnitude less massive than the Earth. | |
| Jun 21, 2016 at 22:56 | history | edited | user21914 | CC BY-SA 3.0 |
Optimal to all.
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| Jun 21, 2016 at 21:43 | comment | added | user21914 | @Aron there is no bouncing off the planet. This is the transfer of momentum. Look at the possible 2016-2020 jupiter flyby and return mission linked in the example query. It goes outbound with 6.28 km/s velocity and returns with 20.13 km/s velocity. The gravity assist could then donate 14 km/s velocity (on a probe, that's not much momentum - on an asteroid, its a bit more) back to Earth and head back out to Jupiter again. | |
| Jun 21, 2016 at 21:40 | comment | added | user21914 | @ckersch you don't. You send it out once. You slingshot it around Jupiter. It picks up some momentum. It slingshots around Earth and loses some momentum. You adjust the trajectory so that it will head back out to Jupiter (or Saturn or further out if the orbits aren't in alignment), and then repeat the process of slingshot and return and slingshot and outbound. It is transferring momentum from one body to another. | |
| Jun 21, 2016 at 14:06 | comment | added | ckersch | How do you propose attaining the necessary velocity changes needed to get something like Vesta into Jupiter's orbit thousands of times? | |
| Jun 21, 2016 at 13:03 | comment | added | Jim2B | Thanks for this answer user21914! I thought I was going to have to write it, lol. Rather than energy transfer, this is more a momentum transfer issue. Theoretically we could start Solar System engineering using this technique right now. But we won't see any obvious benefits for a thousand years or more. Also no need to limit ourselves to just a single working planetoid. Use many asteroids flying through the Solar System to speed up the project. While you're at it, you can move water bearing bodies around and put Venus somewhere that it will be useful. | |
| Jun 21, 2016 at 4:04 | comment | added | Aron | In effect your "solution" is to throw a planet size object at your planet to push it towards the right direction. I feel a catch 22 coming on here... | |
| Jun 21, 2016 at 3:54 | comment | added | Aron | -1 There is nothing magical about gravity assists, they still obey Newtonian Kinematics (restitution etc etc). Give that, you need to "bounce" your satellite off your planet with enough momentum to move it. Randall Monroe sums it up beautiful here what-if.xkcd.com/146 | |
| Jun 21, 2016 at 2:16 | comment | added | JDługosz | Oh, ok, you are moving 2 planets in opposite directions, and just need to be a middleman. I missed that, as your animation focuses on just single slingshots. You burried the lede :) if that's the main idea, with a brief mention in the middle paragraph. | |
| Jun 21, 2016 at 1:27 | comment | added | user21914 | You supply the energy to adjust the orbit of a minor celestial body. You are transferring the energy for moving the major celestial body from another one. Momentum is conserved. You are not spending millions of kg m^2/sec to move the planet but rather picking up a a small amount in a gravitational assist from Jupiter and then donating it to the Earth. And then doing it again. As part of this process, Jupiter will slowly orbit closer to the sun, though it has lots of angular momentum to spare. | |
| Jun 21, 2016 at 1:10 | comment | added | JDługosz | You have to supply all the energy. You just spread it out over more passes. | |
| Jun 21, 2016 at 1:05 | comment | added | user21914 | @JDługosz it doesn't take significant amounts of energy (when compared to the overall expenditures) to grab say, Ceres, Vesta and Pallas and put them on the proper flyby orbit for Earth / Jupiter. The less massive the body transferring the momentum it actually gets easier (less delta V needed to do adjustments) - it just takes longer as you don't transfer as much with each pass. But with sufficient time you can transfer momentum from the gas giants to an inner planet. io9.gizmodo.com/5923828/… suggests 1M passes needed. | |
| Jun 21, 2016 at 0:45 | comment | added | JDługosz | So you still need the energy to be supplied by some means, and you hqve to move the other object. So how do you move that and how's it different from the original question? | |
| Jun 21, 2016 at 0:35 | history | edited | user21914 | CC BY-SA 3.0 |
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| Jun 20, 2016 at 23:42 | review | First posts | |||
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| Jun 20, 2016 at 23:39 | history | answered | user21914 | CC BY-SA 3.0 |