4 ms·
L2 is unstable, so you need some amount of active thrust to stay in the orbit. The point is relatively close to the moon, and changes enough to not collect natu
by dexwiz 3y ago
L2 is unstable, so you need some amount of active thrust to stay in the orbit. The point is relatively close to the moon, and changes enough to not collect natural bodies. Same with L1 and L3. Once the James Webb runs out of fuel it will leave the point quickly, probably within 30 days.
L4 and L5 are way out from the Earth Moon system and are very stable. They collect natural satellites, and once parked there you would remain indefinitely.
The actual math is pretty complex, and has to do with mass ratios of bodies involved, but all the major bodies in our solar system have their own Lagrange points.
- actinium226 3y ago> L2 is unstable, so you need some amount of active thrust to stay in the orbit True > The point is relatively close to the moon, and changes enough to not collect natural bodies. This is awkwardly written. Let's get some background first: the Lagrange points are derived by assuming the Moon's orbit around the Earth is circular. In actual fact it's elliptical, so the distance from the Earth to the Moon changes and consequently the distance from the Moon to L2 changes. The distance from the Earth to the Moon averages 384,400km and at that point L2 is 64,000km away from the Moon. But the reason no natural bodies (like asteroids) collect around L2 is because it's unstable, not because it moves. > L4 and L5 are way out from the Earth Moon system L4 and L5 form an equilateral triangle with the Earth and the Moon, meaning they are (on average) 384,400km away from both the Earth and the Moon at any given time. > and are very stable. No, they are "meta-stable." If you drift away from L4/5 you will not be drawn back to the Lagrange point itself, but you can orbit those points without extra fuel. We see asteroids gathering at Sun-Jupiter L4/5, so that suggests they are weakly stable, but when you do the linearized stability analysis of those points you find that they are neither stable nor unstable. > The actual math is pretty complex It is. I made an effort to create some educational videos on the topic: https://www.youtube.com/watch?v=8q9in-VfpUM https://www.youtube.com/watch?v=8q9in-VfpUM
- ttyprintk 3y agoMy understanding is that earth-sun L4/5 also collect; not asteroids but dust https://en.wikipedia.org/wiki/Kordylewski_cloud https://en.wikipedia.org/wiki/Kordylewski_cloud I believe you’d have to avoid the point itself and orbit around it. Edit: apparently, there are two Earth Trojans: https://en.wikipedia.org/wiki/List_of_objects_at_Lagrange_points https://en.wikipedia.org/wiki/List_of_objects_at_Lagrange_po...
- dexwiz 3y agoI was confusing points using the Earth and Moon and those using the Sun and Earth. You are right in a given system the points draw an equilateral triangle. But JWST orbits the Sun Earth L2 point, so the moon is not directly involved. Of course it influences, but it’s different than the Earth Moon L2.
- bobbylarrybobby 3y agoDoes this mean that you don't need to occupy the centers of L4 and L5, but could instead orbit them at a smallish distance?