90m/s enough for Eve encounter in KSP? (reading delta-v maps)



  • I'm trying to understand https://i.imgur.com/yO0bQax.png , in particular I don't get how 90m/s delta-v should be enough to go from a transfer orbit to an Eve encounter:

    Eve encounter in 90m/s

    In my attempt, I go to a transfer orbit by burning straight up against Kerbin's orbit until I get an escape:

    enter image description here

    This escape burn already gives us about half the required orbital transfer to Eve:

    enter image description here

    But it's not even close to the 90m/s that is allegedly sufficient for an encounter. For that, I need about 400m/s:

    enter image description here

    So what's going on?



  • The starting point is "elliptical orbit around Kerbin with Pe of 10 km above atmosphere (80km ASL) and Ap at the edge of SOI", not solar orbit. If you try to do the burn while in solar orbit, it's much less efficient (because of Oberth effect).

    In theory this means you should be in a (correctly aligned) elliptical orbit around Kerbin, and do the burn of 90m/s at the periapsis.

    In practice such an orbit is a pain to align, and it's easier to read as 930+90=1020m/s burn from LKO to Eve intercept.

    Experimentally, I see a burn of ~1030m/s from LKO to Eve intercept, which seems in line with the map. Screenshot of planned maneuver from LKO to Eve intercept (Mechjeb was used to plan this one specifically)


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