How do I get on the same plane as Minmus? With and without Mechjeb?

[khenness]

Title says it all really.

I usually use the 'trans' setting on mechjeb to get to the Mun, but I can\'t seem to get in right with Minmus. Can anyone help me out?

[vexx32]

I don\'t use MechJeb, so i can\'t help you with that. Without it, though...

First of all, achieve an orbit at the same altitude as Minmus. There are two ways you can achieve this:

1. Slingshot off the Mun, using the patched conics as a guide. Then, just burn until your apoapsis is at 46,400,000m or thereabouts.

2. From a low-Kerbin orbit, burn until the apoapsis reaches 46,400,000m

Then, once you get to the new apoapsis, you have two options. To make it easier and quicker to get to Minmus without waiting for ages to catch up with it in its orbit, I suggest you burn retrograde at your apoapsis to change the direction of orbit entirely. If you want to, you can just burn prograde, but then timing is far more important, or else it\'ll take forever to catch up to Minmus. If you\'ve got your apoapsis this high from a low-Kerbin orbit, the velocity you\'ll need to cancel will be around 50m/s. Continue burning until your orbit is very close to circular.

Once you have a nearly-circular orbit at Minmus\' altitude, you\'ll want to look at your map view. At certain angles, you can see points where the slanted orbit of minmus 'crosses' yours. Warp until you reach one of these. Depending on your orbital direction, you\'ll want to burn either North or South to change the plane of your orbit until it matches closely to that of Minmus. If your orbit is opposite to the direction of Minmus\', the patched conics should already see an encounter by now.

Now comes the rather difficult part. Perhaps. Wait until you encounter Minmus, being very careful not to slingshot past it (it\'s very easy to miss it, particularly if you\'ve orbited opposite Minmus\' direction). You may (or may not, depending on whether you orbited opposite to it or not) want to burn retrograde if the patched conics sees you leaving Minmus SOI. It shouldn\'t take too much fuel. Just burn retrograde untl you have a stable orbit around Minmus, or you\'re heading on a collision course to it.

After that, it\'s like landing on the Mun, only a ton easier, because the gravity\'s so low.

[Nibb31]

Do it the same way as for the Mun, except that you aim for an Apoapsis of 46400km.

Once you\'ve got your apoapsis, you need to move your orbit up or down so that it intersects with the orbital plane of Minmus. To do this, point your ship north or south relative to the orbital plane (Normal + and - in MechJeb) and burn until your orbit intersects.

Once it does, you should see the yellow orbital prediction provided by the patched conics system in the orbital map. From there, you can adjust the periapsis of your arrival in the SOI of Minmus.

[vexx32]

Keep in mind that if you\'re orbiting in the same direction as Minmus, it can take a long time to catch up with it if you don\'t time it properly.

[Endeavour]

I\'ve played with mechjeb before. I\'d say use the acsent autopilot and set the inclination for 6 degrees higher than 90, and have the orbit circularize at 46400 km. But I\'m no expert with it, and this is probably a terrible way to do it.

[Temstar]

You could just wait till Minmus is in such a position that when you reach your 46400km apoapsis it will be there right on the ascending node / descending node above the Kerbin equatorial plane, this will happen twice (and so two launch windows) per Minmus month.

I think adjusting your orbital inclination to match Minmus in LKO before trans-Minmus injection is actually really inefficient. Maximum efficiency of inclination change is achieved at apoapsis right? So if you want to match Minmus\'s inclination it\'s actually better to perform the inclination change at the 46400km apoapsis than it is in LKO.

If it was NASA planning a manned mission though they will probably go for inclination change in LKO because it\'s safer. If the inclination change fails for any reason in LKO then the spacecraft could fairly easily be deorbited to bring the crew back or a rescue mission could be mounted since crew will have enough provisions to survive for days/weeks in orbit. If the engine doesn\'t work at 46400km for the inclination change then the crew is going to die a slow and painful death in Kerbol orbit.

[khenness]

Cheers guys, going to try it out now and i\'ll post back

[Tarmenius]

Something else you can try is waiting until KSC intersects Minmus\' orbit and launching to 96 degrees (or 84 depending on which intersection you\'re at), saving yourself a plane-change maneuver. Then just time your Trans-Minmus Injection burn the same way you would for the Mun.