![]() ![]() It took a little while though, something like 1/3 to 1/2 of a Mun orbital period, which could be sped up with more dV.įrom there, it was a burn much like leaving Munar orbit for Kerbin. So this ended up behaving as if I had simply slid out the back of L4. This actually set up for a bit of a retro slingshot inbound with a prograde slingshot outbound to ~30Mkm (think like an elliptical horseshoe). This caused the craft to enter the Mun's SOI slightly outside the Mun's orbit and pass in front. (It actually took about a 45deg burn to slow and go wide.) I spent about 30 dV and ended up in what would have been an elliptical orbit, except the Mun was there to catch me. Instead of sliding out the back of L4, I misaligned the orbit slightly so that my craft swung outside the Mun's orbit. Instead of thinking like Lagrange points, I thought about it like I was trying to rendezvous with the Mun. ![]() You might be able to just slide out the back if you can get the station just in front of the SOI, but that's tough in addition to getting a perfect orbit. It was cheaper to just burn and drop straight back onto Kerbin. If I really wanted to slide out of L4 it was going to be too much dV. I figured this was probably inefficient and I verified my thought above. I started playing with the maneuver node, thinking as if I was trying to slide out of L4 (which KSP doesn't really simulate). I set myself up in front of the Mun, just outside of it's SOI (2.4Mkm). (I chose the Mun because I didn't feel like dealing with Minmus' inclination and it's easier to deal with transfer timing.) I had been wanting to try having a station or something like this, but I had (in my head) already settled on leaving whatever it was in Munar orbit. Okay, so I went ahead and tried this out on the Mun. (So I suppose my guess without math is around 650 to 700m/s.) Then whatever dV to correct the slingshot velocity. So since Minmus has an orbital velocity of about 274 m/s, you would need twice that to reverse your orbit for a retrograde slingshot back to Kerbin. You can sort of simulate L4/5 by being there, but you're not actually in a Lagrange point from a physics standpoint. But the reality is that it will probably take a lot more than that because KSP doesn't really support Lagrange points. My guess is that it would be in the neighborhood of 150 m/s. If your goal is to hit Kerbin's atmosphere, you can calculate all that out (as there would be an optimal Mun altitude) but this one is probably easier to just try out and see. So there's no best launch location to constantly point at an L4/5.ĭelta V to slingshot past Minmus back to Kerbin will depend on a variety of things how low you want to slingshot. Minmus' rotation isn't synchronous with it's orbital period. How much deltaV would it take to slingshot a cargo past minmus such that it drops to low kerbin orbit to the east? and how much to the west? ![]() What would be the longitude (laditude would presumably be 0) of the best minmus launch site to reach the station? (presumably the point directly under the station, but minmus's rotation may throw this off) It might save you some math getting to/from Minmus or into Minmus orbit.īTW: I haven't done much with Lagrange points myself, but I hear they don't work very well yet. You can do this math backwards to figure out how much it costs to lower your orbit. To leave the elliptical orbit at r=r_2 to the r_2 circular orbit where r_1 and r_2 are, respectively, the radii of the departure and arrival circular orbits the smaller (greater) of r_1 and r_2 corresponds to the periapsis distance (apoapsis distance) of the Hohmann elliptical transfer orbit. To enter the elliptical orbit at r=r_1 from the r_1 circular orbit Therefore the delta-v required for the Hohmann transfer can be computed as follows, under the assumption of instantaneous impulses: Mu = GM is the standard gravitational parameter of the primary body (Kerbin) You can use the wiki page for calculating delta V and combine with the delta V map below (or this one if you prefer it a little simpler). ![]()
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