08/21/18 at 21:20:53 News: Registration for new users has been disabled to discourage spam. If you would like to join the forum please send me an email with your desired screen name to tony at gravitysimulator dot com.

 Pages: 1
 EDG Ultimate Member oh, crumbs!!! Posts: 611 Gender: Lagrange points? 01/28/11 at 11:42:18   I guess this is more a science question, but if I can simulate it in GS then all the better   For the SF background I'm working on, I want to have 'jump points' located at the L4 and L5 points of the most massive objects in a planetary system. This has a few implications:   1) If there are no planets in the system, then it contains no jump points at all. This is OK, but I'm wondering what happens if you just have a system full of dust and rocks - would there be any L4/L5 points in there? If the only massive object of note was a small 10-100km diameter asteroid that had 'cleared out its orbit', would its lagrange points be stable at all? What would be the smallest object that can have stable L4/L5 points? I'm figuring that the jump points themselves are massless objects, but at really small scales I guess the mass of the spaceship itself might disrupt things!   2) If there were no planets, but multiple stars (e.g. a Binary or trinary system) then you wouldn't have L4/L5 points unless the mass ratio of the stars was below about 25:1 (so in most cases they'd be unstable you had a very massive star and a low mass star, such as a 10 solar mass star and a 0.4 solar mass star, which would be unlikely).     3) In a solo or multiple system containing planets, the jump points would be found at the L4/L5 points of the most massive planet in the system. The jump points can exist in a system as long as stable L4/L5 points are located anywhere within it.     How could I test this in GS? I'm not sure how one makes an object orbit an L4/L5 point, do I just create the lagrangian object with the same orbital parameters as the planet but with a mean anomaly of +60 or -60 degrees relative to the planet? (I guess it might drift a bit and go into an orbit around the L4/L5 point over time?). And if I put other planets in different orbits in the system, would they affect the stability of the L4/L5 points? Back to top (formerly known as Mal)   IP Logged
 EDG Ultimate Member oh, crumbs!!! Posts: 611 Gender: Re: Lagrange points? Reply #1 - 01/28/11 at 14:22:26   Quote from EDG on 01/28/11 at 11:42:18:How could I test this in GS? I'm not sure how one makes an object orbit an L4/L5 point, do I just create the lagrangian object with the same orbital parameters as the planet but with a mean anomaly of +60 or -60 degrees relative to the planet?   I guess not, since if I do that I get two objects in the same orbit, with one 60 behind of the other, but if I switch it to a view centred on the planet then I just see the lagrange object orbiting the stationary planet (on an interior orbit relative to the sun). I suppose the problem is that I have no idea how to do those nice lagrange animations that others do here. Back to top (formerly known as Mal)   IP Logged
 Tony YaBB Administrator Posts: 1057 Gender: Re: Lagrange points? Reply #2 - 01/28/11 at 15:49:21   It should work if you create objects 60 +- from a massive body.  Create all three of the objects at the same time though.  Don't look at your planet's mean anomoly in the Orbital Elements interface and add or subtract 60 from that.  The problem is that mean anomoly is measured from the ascending node, and if your planet is orbiting in the ecliptic then there is no ascending node, and mean anomoly is arbitrairly reported.   I don't think there's any lower limit to the mass of the planet.  But the lower it gets, the more likely that other bodies will perturb your objects out of L4/5.  In a 2-body system (2 bodies with mass) and 2 more massless bodies, there should be no lower limit as long as you maintain a ratio greater than about 25:1 Back to top IP Logged