I can't get to minmus

[czarniecki]

It's just impossible for me and i don't know why. I set a nice orbing around kerbin, i set a maneuver node, so that my apoapis is the same height as minmus orbit, but to actually get near minmus, it's literally case of one pixel, and even if i get that pixel right, instead of being where i should be, i get on the same orbit around sun, as kerbin

[Streetwind]

Are you sure you're transferring at the right time?

The Mun may have taught you that it is pretty much irrelevant when you transfer. As long as you have a craft in a reasonably equatorial orbit, you can make a node somewhere that gets an encounter, and transfer immediately. However, the Mun is the only destination the game for which this works. All other destinations require better timing, called a "transfer window".

Minmus is a bit of an edge case. If you launch into an equatorial orbit, like you normally do, there are technically two perfect transfer opportunities for each complete orbit of Minmus around Kerbin. You can transfer at any other time too, and probably fudge things in place with a mid-course correction, but it's less than ideal. You can also launch directly into Minmus' inclination, and then you have a similar situation like with the Mun, where you can just make your node and go - but launching into Minmus' inclination is, again, only possible at two specific times for each of its orbits.

It sounds to me like you're trying to make a node at a point in time where the transfer is not ideal, probably because Minmus is too far above or below the equatorial plane at the point you try to intercept it. You can just barely get a tiny sliver of an encounter, but it's a poor one, and easily missed.

Your options: 1.) perform a mid-course correction to finetune your encounter; or 2.) wait until a more convenient time. But without knowing where Minmus currently is in your game, I cannot tell you when that time will be.

 

Edited July 20, 2020 by Streetwind

[bewing]

It sounds to me like you have 3 issues here.

The first is, if you are ending up in orbit around the sun, then you are burning too long. You have to stop burning when your Ap gets just above Minmus -- even if it doesn't look like you have an intercept.

The second is, the orbit of Minmus is not in the same plane as Kerbin's equator. Since you say your maneuver node is very delicate, that makes me think you are not adjusting your Kerbin orbit to be in the same plane as Minmus. If you do that, it will be much easier for you to make a maneuver node that works. However, it is not necessary to adjust your plane in order to get to Minmus. Doing that just makes the maneuver node easier.

The third is that it is not necessary to reach your destination with just one burn. There is a very important concept called a mid-course correction burn. With your first burn (your "ejection burn"), all you really need to do is get close. Then once you are halfway to your destination you can make a few tiny burns to give yourself a really good intercept.

 

 

[king of nowhere]

i also think your problem is orbital plane. to get to minmus, you need to change your inclination. set minmus as the target, so you can see the ascending and descending nodes. then correct your inclination, and then getting an intercept is not a big deal. that's the easy way.

the efficient way is to change your orbital inclination later. it's much cheaper to change inclination when you're farther away from kerbin. i found the best place to do so is after passing mun's orbit. that's harder to set up because, if you want to visualize the intercept, you need to set up two manuever nodes while you are still in LKO.

anyway, since minmus is much farther than mun, it is only natural that slight modifications of your original trajectory will have a bigger impact on your destination. you have 5-10 days of travel for those small deviations to accumulate, instead of just one for mun. so, to get a precise insertion you really need a course correction manuever halfway from your target. it's not a bug, it's just how things are.

[MrSystems]

The easy (and fuel-inefficient) way that @king of nowhere was talking about:

1. Get to circular Kerbin orbit.
2. Click Minmus and Set Target.
3. Look for the AN / DN (Ascending/Descending Node) markers on your current orbit, and set a Antinormal/Normal maneuver node there such that the AN/DN readout shows 0.0°. It should be about ±230 m/s dV, depending on the height of your orbit and how close to equatorial it is.
4. Burn that node.
5. You're now in the same orbital plane as Minmus. Aim ahead of the planet and set a node (about 920-925 m/s dV) the same way you would do for the Mun. Move the node ahead or behind in time to get an encounter.

[Joe Kerbal]

It's definitely orbital plane. 

I forgot about it the last time I was getting there just due to the fact you never check it while getting to mun. Align the plane as first manouver (6 degree roughly) and then it will be ok.

[betweenthelines1]

I always have a mid course correction when I go to Minmus. 

This is what I do.  Get a equatorial orbit, open up the map mode.  make Minmus my target.  I put my insertion burn at the point of my orbit where Minmus would be rising above Kerbin.  Set the Ap at about 42 M.  I then move the start time of that burn to get the closest encounter markers as close as possible.   Then I select my plane change node.  if the an/dn are close to Kerbin use that point.  Otherwise I just pick a burn 10-20 minutes after my first burn.    

Once I have both nodes created I focus on Minmus, and tweak the two burns.   The first burn controls the height of the PE above Minmus.  The second burn moves the PE towards/away from Minmus orbital plane,