I can't get to Minmus

[phantom000]

I got there once but i can't seem to get back. It's navigation. I can get to Minmus orbit just fine but getting into Minmus gravity is something else. When i set up a maneuver node i can never get it to show 'Minmus Encounter' am i doing something wrong or is this some kind of bug?

[bewing]

No, I'm afraid you are doing something wrong. Do you want to figure out how to get a maneuver node set properly? Or do you just want to get there? It's pretty easy to get there without using a maneuver node.

Part of the problem with maneuver nodes is that Minmus is not in an equatorial orbit -- so if your ship is equatorial (which it almost certainly is) then you will usually miss Minmus by at least 2Mm, and you won't ever show an encounter. This is probably what is happening. One answer is to set Minmus as your target, and then set the maneuver node so that you are as close as you can reasonably get, then do the burn, and then after that burn north or south to get your Ap into Minmus' orbital plane.

It is also possible to add the normal/antinormal bit into the maneuver node itself, and then you will see an encounter. It is also possible to get close with the first maneuver node, and then put a second maneuver node on your projected flightpath, with the small normal/antinormal burn in it.

Or, you could waste a whole bunch of fuel and adjust your ascending/descending nodes to match Minmus first, and then set your maneuver node like you normally do.

If you just want to go there, then launch straight up when KSC is 30 to 45 degrees ahead of Minmus. Get your Ap up to 44Mm or so, burn north or south to adjust to Minmus' orbital plane, and then add just enough prograde to get an encounter.

Edited July 2, 2016 by bewing

[CSE]

I think the easiest way is to launch into an equatorial orbit just as for going to the Mün. Target Minmus and perform a prograde burn with the closest approach you can get. This will take you out to Minmus' orbital distance just as you have been doing. In the map view, your orbital path will take you above or below Minmus, which is why your closest approach doesn't make an encounter.

Now put a new node on your path about half-way to Minmus. Burn normal or anti-nomal (up or down when you're looking at your orbit as horizontal) at this point to give you a course correction that is so cheap in propellant / dV that it normally doesn't affect mission planning at all.

This isn't quite as efficient as launching straight into the correct plane and burning all the way to Minmus encounter before you've left Kerbin's atmosphere. But it's close - much more efficient than trying to match planes in low Kerbin orbit or correcting at the last minute as you fly past your goal. And it lets you do one thing at once: launch east; circularize east; burn prograde from LKO; burn normal from half-way.

Edited July 2, 2016 by CSE

[Vaporized Steel]

I always go 90degrees orbit. The I open map view. Then I zoom out and change camera orientation that my blue orbit line becomes straight by camera angling exactly parallel to the vessels orbit. 

Then I zoom out and keep rotating the camera. I do this by keeping the camera parallel to my vessels orbit until minmus orbit line also becomes parralel to my vessels orbit line.

At this point they cross. This is where I want to put a maneuver node. All I need to make sure is that minmus is one quarter orbit from this position which is the an/dn. You can easily eyeball this. 

[Waxing_Kibbous]

Here is a video that may be helpful:

 

[Mjarf]

I usually enter a regular equatorial orbit around Kerbin 100km or so high, then set Minmus as target and match the orbital inclination. Once the orbital inclinations are parallel it's very easy to set up a maneuver node to get an encounter.

[FullMetalMachinist]

2 hours ago, Mjarf said:

I usually enter a regular equatorial orbit around Kerbin 100km or so high, then set Minmus as target and match the orbital inclination. Once the orbital inclinations are parallel it's very easy to set up a maneuver node to get an encounter.

While this is probably the simplest way to get to Minmus (and the easiest way to grasp the orbital mechanics involved), it's probably the least efficient way to do it in terms of dV. Inclination changes at low Kerbin orbit are crazy expensive. 

It's much more efficient to burn prograde to raise your AP to roughly Minmus' orbit, then make a mid-course burn that fixes your inclination and gets you an intercept at the same time. 

[Geschosskopf]

On 7/1/2016 at 7:17 PM, phantom000 said:

I got there once but i can't seem to get back. It's navigation. I can get to Minmus orbit just fine but getting into Minmus gravity is something else. When i set up a maneuver node i can never get it to show 'Minmus Encounter' am i doing something wrong or is this some kind of bug?

The trick to hitting Minmus encounters is to leave Kerbin orbit at either the ascending or descending node of Minmus relative to Kerbin..  What you do is launch into a low parking orbit at Kerbin, then set Minmus as your target.  This will show its ascending and descending nodes on your LKO orbit.  Then look where Minmus is.  It will be closer to 1 of those nodes or the other, and on its way to the next.  Create a maneuver node on the opposite node and pull prograde until your trajectory crosses Minmus' orbit near the node Minmus will reach next.  You should see a closest approach marker at this time.  Move the node forwards or backwards on your LKO orbit and adjust the burn as necessary in all directions EXCEPT normal +/-.  The goal is to get an encounter pretty much at one of Minmus' nodes so that you don't need to change inclination.

it could well be that getting this type of encounter sends you pretty far beyond Minmus' orbit nearly to the edge of Kerbin's SOI.  But no matter.  You're moving so slow out at Minmus that it really doesn't affect your capture burn even if you encounter it at about 90^ to its direction of travel..