I would like a swing-by/Gravity assist maneuver planer to minimize dV for e.g. planet transfers.
http://en.wikipedia.org/wiki/Swing-by

Not saying its impossible but this may be more difficult than it sounds due to the nature of KSP only simulating gravity from the SOI you're currently in. Again I'm not saying there isn't a clever way to do this but the math will probably be harder than you'd expect.

MechJeb isn't using KSP to calculate orbits as far as I know, it's doing that itself. Even KSP can show you the results of a gravity assist maneuver though, passing into and out of a moon or planet's SOI, if your patched conics setting isn't too low. This is not the same as finding the optimal time to launch to get a gravity assist that takes you where and when you want to go, however. That might be a fairly complex problem, even for a single assist. Even with the nearby, relatively quick orbit of the Mun, there's no guarantee that an interplanetary departure window will overlap with a time at which the Mun would be in the required position to assist.

That said, it would be awesome to have such an addition to the rendezvous planner!

Thinking about what's needed, at least in the case of the Mun, I realized it's basically just a matter of having the angle between the Mun and Kerbin's prograde / retrograde be at 90 degrees at the approximate time you reach a prograde periapsis around the Mun. Instead of burning retrograde to brake, you burn prograde to further increase your escape velocity, until your orbit escapes from Kerbin's SOI parallel to its prograde or retrograde orbital path (depending on if you're going to an outer or inner planet). Or if a single burn at Mun periapsis would take too long, you can do some or all of it as you coast toward Munar escape instead.

It might be possible to write something that would at least check whether the orbit of any moons of your current planetary SOI would place it in a useful position for an escape gravity assist.

as far as i understand this it should not be to complicated for a single gravity assist... hohmann transfer is doing half of the job - you should just add (radius + savety zone) instead heading for the middle of the planet/moon...
the other part is tracing for a window when you will reach the next target with your gravity assist maneuver (but this is backtracking i think) this should be not to hard if you use hohmann again but backwards from the target to the leave point of planet/moon gravity...

atm i try it with planing hohmann to moon, planing min distance at radius (+ 1km) and then hope you will hit the real target and get window right...(and maybe if all fails - then use hohmann again direct to target) (so the most stuff is allready in the mod..)

@lotzofgibberish: i don't see a problem there if you use gravity assist you aim for a planet/moon in the same system you are in.. while gravity assist you are in the system of the planet/moon and after you are in the system you started (at least for a while)...

edit: minimizing dV is the hardest thing about this (and if you use more then one gravity assist)

Good point. An issue I forsee is mechjebs infinite desire for perfection. Optimal assists only come once every so many revolutions around the sun. If you use some sort of life support mod and it just began a super speed time warp for several years, all your kerbals would die.

On May 16, 2013, at 11:18 AM, DEvil0000 [email protected] wrote:

as far as i understand this it should not be to complicated for a single gravity assist... hohmann transfer is doing half of the job - you should just add (radius + savety zone) instead heading for the middle of the planet/moon...
the other part is tracing for a window when you will reach the next target with your gravity assist maneuver (but this is backtracking i think) this should be not to hard if you use hohmann again but backwards from the target to the leave point of planet/moon gravity...

atm i try it with planing hohmann to moon, planing min distance at radius (+ 1km) and then hope you will hit the real target and get window right...(and maybe if all fails - then use hohmann again direct to target) (so the most stuff is allready in the mod..)

@lotzofgibberish: i don't see a problem there if you use gravity assist you aim for a planet/moon in the same system you are in.. while gravity assist you are in the system of the planet/moon and after you are in the system you started (at least for a while)...

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then you could still send probes/drones/satelites to such missions... or mechjeb could plan an optimal start window from kerbin - so they can wait on kerbin and minimize orbiting times this way...

This, I would like this even if it sucks

You can add it personally using the maneuver node planner and some messing around. Idk if it'll be an official feature or not though

On Jun 3, 2013, at 12:22 PM, andyhoffman12 [email protected] wrote:

This, I would like this even if it sucks

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2,868.75 km is the magic number... lowering the returning to the orbit will
change your position along your track, the only other maneuver you need is
a change of inclination, because you are seeing such a large footprint you
should only need fairly inaccurate positioning with only a small number of
satellite (3-4) to cover the whole planet...

On 3 June 2013 21:39, lotzofgibberish [email protected] wrote:

You can add it personally using the maneuver node planner and some messing
around. Idk if it'll be an official feature or not though

On Jun 3, 2013, at 12:22 PM, andyhoffman12 [email protected]
wrote:

This, I would like this even if it sucks

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Reply to this email directly or view it on GitHubhttps://github.com//issues/92#issuecomment-18869523
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Duplicate of #1051