2 questions

[JackBush]

I'm trying to get an orbit around the moon but keep ending up with this:

http://imgur.com/YmqssLT 

I get the same result whether I use MJ's maneuver planner or do it myself. Mind you, I did get into Kerbin orbit using MJ's ascent guidance. Anyway, why does it happen? How do I get a better result?

Second question: when I use MJ the little icons beside the navball (prograde, retrograde, etc) disappear. Is there any way to get them back when I want to do something on my own?

[Hupf]

@question 1: maybe this video will clarify: https://www.youtube.com/watch?v=IcTQ4YwxLGc

What you see as an interruption of the trajectory is due to the way KSP handles the concept of "Sphere of Influence" (SOI) and renders the trajectory preview as "patched conics" which can be done in different modes, i.e. from different viewpoints (it's explained in the video).

If you end up too close to the Mun, then you should try very carefully to fine-tune your maneuver node (e.g. burn a little more/less prograde). The blue line gives you a preview of your Mun flyby, so you should make sure that your Periapsis will be higher than the Mun's radius

@Q2: MJ sometimes automatically starts time accelerating. Try resetting it to 1x ("," key) and then try hitting the "t" key again to re-enable SAS

[Starhawk]

You've completed the first step in orbiting the Mun.

The second step is to burn retrograde when you are closest to the Mun (Munar periapsis) until you have closed your orbit around the Mun (captured).  You can then adjust the orbit as desired.

Sorry, I can't remember how MJ works.  Someone else will know that one.

Happy landings!

[ElWanderer]

You have no periapsis, so are on a collision course. You can fix this by plotting a radial (the blue circles) manoeuvre as soon as possible. You should only need a small burn to raise your periapsis from under the Munar surface.

I don't know about MechJeb. But in Kerbin orbit very minor changes to your escape burn can have a very big impact on where your course ends up. Burning a manoeuvre node never works out exactly as plotted. If burning manually, switch to the map and watch how your course plot changes during the burn. When you get near to the end of the burn, throttle right back and be ready to kill the engines when your predicted path is in the right place, not necessarily when you've burnt exactly as per the manoeuvre node. If you end up slightly off-course, you'll only need a small correction.

[Hupf]

If you have trouble with overshooting on burns or with tuning maneuver nodes just right, maybe try the following: only use a node to get the right burn direction / ship orientation figured out (radial in this case, as mentioned by ElWanderer, i.e. the cyan marker in the navball). Then open the map view, focus on the Mun and start burning very slowly (i.e. one quick "Shift" press). Observe the trajectory change very carefully and only increase acceleration if you're comfortable with the speed of the trajectory change. This way you can end up with quite precise Pe/Ap target values without Mods like PreciseNode.

[JackBush]

Great. Thanks, guys.

[Plusck]

I second Hupf's advice. I generally click on the delete node button when it's down to the last few m/s of a burn and watch what is happening on the map. Removes clutter from the map view, stops me overshooting, and in most cases lets me get closer to where I was actually wanting to go in the first place. 

From the picture, it looks like your burn from LKO to the Mun was perfect to have you arrive at Mun's orbit just as the Mun is catching up on you. The trouble is you don't actually want to raise your Ap quite as high as Mun's orbit, but a little lower so that the Mun pulls you into an spinwards orbit (i.e. the same eastwards direction as orbiting Kerbin), or a bit higher and further ahead so that you get pulled anti-spinwards the other side (but this means you need to lose more speed to land). 

[MircoMars]

for 1)

right click on mun and select "focus view", now you see the flight trajectory in relation to mun. plan and execute transfer burn, notice, you can see in dotted line which way you'll pass mun. PE at mun between 10 and 20km. after SOI change, put your capture maneuver at the PE and burn retro until the egg-shaped orbit, an AP and the lack of a SOI-exit confirms your perpetual free fall around your destination.

2

MJ has the "Smart A.S.S." module, which is stock sas' big sister on steroids and comes in it's own windows. my favorite feature is surface mode where you can hack in pitch, yaw, roll in degrees. also it has more directions to point at than stock sas, e.g. target's docking port orientation, which is unbelievably helpful. for anything else (sas wise) I either use stock or no assist. stock and MJ control cannot run side by side, thus MJ disables SAS if it's active.

On 9.12.2015, 15:40:17, Hupf said:

@Q2: MJ sometimes automatically starts time accelerating. Try resetting it to 1x ("," key) and then try hitting the "t" key again to re-enable SAS

MJ only does that if it's allowed to. there must be a "Auto warp" checked somewhere, even if it's checked for "ascent guidance" it will trigger in "maneuver planner" as well. If anything strange is happening with MJ on board, check the MJ menu for green highlighted modules. they are currently controlling something. most often you'd find the usual suspects all chilling in the "utilities"...

[Snark]

By the way:  From that screenshot, you actually have a very good approach, because the shape is close to a U and your periapsis is close to ground level..

I define "good" as "efficient use of dV", i.e. you don't have to burn a lot to capture to orbit.

What does the theoretical ideal Mun approach look like?

• It enters the SoI boundary at very low Mun-relative speed.  You can tell a good orbit if the path around the Mun is close to a 180-degree U-turn, rather than flying past and only getting bent by a shallow angle.
• It has a periapsis that is as low as possible to the munar surface without scraping toes.

That's the ideal approach orbit, and the ideal burn is then to do a retro-burn right at periapsis.

If you have a "bad" approach, there are two ways it can be bad:  1. your velocity is too high (i.e. you're deflecting just a few degrees, not making a U-turn), or 2. your periapsis is nowhere near the surface.

Look at your orbit there:  You're already a near-U, so that's great.  And yes, you're on a collision course with the Mun, so your periapsis is underground... but from the looks of it, it's not very far underground, so just a little correction burn radially outwards (as early as possible) should be enough to raise it above-ground.  Leave it low, raise it just enough so it won't smack into any inconvenient mountains.

Then do your retro-burn at periapsis to capture, and you're golden.