Munar Orbit - I did it... but I don't know how! How to recreate confidently?

[JoeSchmuckatelli]

I've been following Wiki tutorials - and they helped get me close and then I panic-tried everything until I had both an apoapsis and a periapsis around the Mun... which I am calling orbit.

Problem is - success through panic is not a reliably recreatable method.

What I'm not finding online is an explanation of what's happening on the orbital map: as I approached my Mun encounter, everything changed abruptly, and I simply did not know what was going on.  There were orange lines, purple lines, and my craft's projected path took it through the Mun.  Instant information overload.  I figured the blue path going through the Mun was not a good thing - and I just spun the ball around until whatever input I had seemed to be widening the purple orbit plane until it showed a periapsis - well, I think that's what happened; eventually the purple disappeared and now I have a nice blue path around the Mun.

 

The weird thing is that I now have this orange arc - and I don't know what that is.  (It goes to the surface).  It may be a maneuver node I inadvertently established - but I cannot figure out how to clear it.

 

So - given that some of the vids I've watched were made quite a few iterations ago - is there a newer or still applicable resource to show me how to do this again, without all the panic?

 

Thanks!

[Plusck]

The basic mechanics haven't changed in .. forever mostly. So most videos will be correct about manouvre nodes and whatnot.

Post a pic from your map view and I (or someone else) can annotate it, if you want. I have to leave in about 40 minutes so ...

 

 

I should also add - when you transition from one SoI to another, the map goes through a phase of refocussing itself. There is a short time in the middle when you are effectively shown in the middle of space with an arc going nowhere. That is normal.

Edited December 14, 2015 by Plusck

[Superfluous J]

1. Get your orbit line intersecting Mun's SOI.
2. Time warp to Periapsis around Mun.
3. Burn backwards (aka retrograde) until your flyby becomes an orbit.

There are far more steps if you want to be efficient, but this is getting into an orbit in a nutshell.

[Plusck]

Won't have time to look at a pic if you post it but:

- dotted orange: where you will go if you do what the manouvre node tells you to do

- solid orange: where you are currently going in the next SOI (so from Kerbin to the Mun, solid orange is what happens when you enter Mun's influence)

- purple: where you are currently going to go when you leave the next SOI (so from Kerbin to the Mun, your resulting orbit around Kerbin after leaving the Mun's influence is purple).

Actually now I think about it I'd have to check that orange/purple is with respect to SOI changes or major/minor SOI changes...

Edited December 14, 2015 by Plusck

[JoeSchmuckatelli]

Okay - that bit about 'purple telling you where you will go after you leave the SOI' makes sense now.  Trying to get a Minimus flyby, I found a weird purple circle - and after studying the map I figured out that (because I was going to miss minumus this pass) that my return trip toward periapsis would take me past the Mun - and it was going to throw me into a really disadvantageous orbit around Kerbin (for someone trying to get to Minimus).  So I accelerated Prograde - and the purple circle disappeared.

It's starting to come together - thanks for the responses!

[Hysterrics]

To improve upon @5thHorseman's steps...

Well, actually it's pretty spot on, but sometimes you won't have a periapsis. That's will be represented by the blue line (Your current orbit) going right into the Mun. That is an issue. Set up a node not to far from your vessel, but not too close where you miss it while still adjusting it, and just kinda mess around with the prograde marker and the blue markers. If you get a periapsis, that's good, but make sure it's above 6,000m, or it's very likely that you will crash and not land on the Mun today. Now, congratulations! You know have a flyby of the Mun. To get into orbit, just warp to Periapsis and burn retrograde, and that will bring down you orbit. When you see the apoapsis sign, you're in orbit. You can keep burning retrograde until periapsis and apoapsis switch sides, which will mean you are in a circular orbit.

Now, don't freak out when you switch SOIs. It is a lot of information to take in, but you have time on your side. Look at it and just process the information. Just think about it logically. Remember...

Blue - Your current orbit

Dotted Orange Line - Your new orbit if you follow your maneuver node.

Orange Line - Your new orbit if you keep going and don't change anything. The reason why your new orbit is usually so large is because you're getting a gravity assist around to Mun, which is picking up energy from the flyby. This is an advanced concept that can be used to your advantage, but don't worry about it right now.

I'll quote The Hitchhikers Guide to The Galaxy to make a point, Don't Panic, You have time! If you need to pause and look at some posts here you can do that. You can also use F5 to quick save if it makes you feel a bit safer. If you mess up then hold F9 to load that quicksave. If you want to be more organized with your quicksave then you can press ALT F5 to save your quicksave with a name and hold ALT F9 to load a specific quicksave.

Hope this helps!


 

[JoeSchmuckatelli]

Holy noodley appendages!  I didn't know you could save a named game from space.  I've been reverting flights and praying Jeb survives my decision making the next try.  Well, given the time investment getting to a Lunar orbit, I'll be a bit more confident trying things with a save game to work with!

 

Minimus has been giving me fits trying to match the orbit, meet up with it, and not have the Mun throw me into Kerbin.

 

It's fun, Tho!

[JoeSchmuckatelli]

Okay - quick question - I've added a maneuver node that looks like it will achieve insertion into Minimus' orbit.  Can I not 'warp time' to right before that - or am I limited to warping to that maneuver?

[Snark]

31 minutes ago, JoeSchmuckatelli said:

Okay - quick question - I've added a maneuver node that looks like it will achieve insertion into Minimus' orbit.  Can I not 'warp time' to right before that - or am I limited to warping to that maneuver?

Well, you need to actually do the maneuver, right?  If I understand correctly, what you're saying is this:

1. you're on some orbit around Kerbin that doesn't intersect with Minmus' SoI
2. you just now added a maneuver node and twiddled it until you get a Minmus intercept
3. you want to timewarp to get to Minmus and need advice

Well, the game will happily let you warp right past the node, but then of course that means you didn't do the maneuver that gets you the Minmus intercept.  So typically what you'd do is warp up to just before the maneuver, do the burn, and then warp the remainder of the way to Minmus.

 

[Snark]

Regarding your original question:  Here's a typical sequence for getting orbit around the Mun (or Minmus):

1. Get into LKO
2. Set up a burn to take you to the target's SoI and put you in as "good" a trajectory as possible to make it easy to capture when you get there
3. Once you're in the target's SoI, do the necessary maneuvering to achieve capture

I'll assume that you have #1 down pat. 

#2 is full of little subtleties and could be a lengthy post in its own right, but for the moment I'll assume that you can at least get an SoI intercept even if it's not the most ideal one.

#3 is what I think you're currently asking about, yes?

"So I've just entered the Mun's SoI and want to be in orbit around it.  What do I do?"

The simple answer is:  Wait until you're at periapsis, then burn retrograde until your orbit closes.

The only potential wrinkle is :  what if your current trajectory (when you enter the SoI) would cause you to impact the Mun?  In that case, what you do is this:  as early as possible (e.g. right when you enter the SoI), point your nose in the orbit radial outward direction and do a gentle burn.  That will raise your Pe.  Do just enough burn to raise your Pe out from undeground, and bring it up to the lowest possible altitude where you don't have to worry about smacking into a mountain (anything over 8000m should be fine).  Once you've done that, wait until you get to Pe and then do your retrograde burn, as described above.

[Reactordrone]

4 hours ago, JoeSchmuckatelli said:

What I'm not finding online is an explanation of what's happening on the orbital map: as I approached my Mun encounter, everything changed abruptly, and I simply did not know what was going on.  There were orange lines, purple lines, and my craft's projected path took it through the Mun.  Instant information overload.  I figured the blue path going through the Mun was not a good thing - and I just spun the ball around until whatever input I had seemed to be widening the purple orbit plane until it showed a periapsis - well, I think that's what happened; eventually the purple disappeared and now I have a nice blue path around the Mun.

 

The weird thing is that I now have this orange arc - and I don't know what that is.  (It goes to the surface).  It may be a maneuver node I inadvertently established - but I cannot figure out how to clear it.

 

 

The projected orbital paths appear to change when you change to another body's sphere of influence (SOI). When you're in Kerbin's SOI your Mun encounter will appear in brown and as you cross into the Mun's SOI that part of the orbit will change to the blue orbital path around the Mun. If you're in Kerbin's SOI and you want to see the orbit as it will look in the Mun's SOI you can click on the Mun and select focus view. This view can be very handy for fine tuning your approach since you can set up a manoeuvre node near Kerbin and see how small changes can effect your approach to the Mun.

Edited December 14, 2015 by Reactordrone

[Plusck]

OK, graphical demonstration of what this all means.

This is me in LKO. Planning a Mun fly-by:

So what you can't see here is my orbit in solid blue around Kerbin.

Orange dotted line is what my manouvre node gives me (if I burn correctly to follow it). However, I'm going to enter into the Mun's sphere of influence (so I'll be moved by Mun's gravity, not by Kerbin's). Therefore the green dotted line is what will happen AFTER leaving the Mun's influence.

Next pic is after making the burn. I've made the potential orange dotted line into a real blue line:

I've switched focus to the Mun, because I want to plan the fly-by better.

Because I haven't entered the Mun's SOI yet, the path is solid orange. I'm still right at the start of the solid blue line, just leaving low Kerbin orbit (LKO).

So orange is what happens when I enter the Mun's sphere of influence. However I'm just going to fly right past in a curve, so I'll return to Kerbin's SOI on a slightly different orbit. This post-SOI-change orbit is in solid purple.

Also important to note is that the solid orange line is at an odd angle to the Mun compared to my blue trajectory, because this is my flyby trajectory in the future, and the Mun won't be in the same place. When I reach the Mun it'll be a quarter of the way around Kerbin. If you transplant this picture of the Mun and my orange trajectory to where the blue line shows the encounter will happen, you can see that the Mun is going to come up behind me and I'll whizz past it on Kerbin's side (or rather, the Mun will whizz past me on the opposite side from Kerbin, since I'm the one going slowly with respect to Kerbin just after my blue Ap), and the Mun's gravity will pull me back up and away from Kerbin.

I was quite proud of this one because it put me exactly where I wanted it to be: return into Kerbin's atmosphere at just the right height to re-enter without burning up. I had hardly any fuel and this gave me a free return to splashdown without using any more fuel at all.

However, rounding errors can add up and in reality, the purple line wasn't quite where I ended up being. I had to correct to bring my reentry altitude lower. But it was close.

Edited December 15, 2015 by Plusck

[GarrisonChisholm]

4 hours ago, Sequinox said:

"...ALT F5 to save your quicksave with a name..."

 

*hears a celestial chorus ring out the golden C chord from Blue Beard*

 

Eureka!!!!!  What a discovery THIS is!

Thank you, you have given order to chaos.  Saves may now actually be useful.

[Snark]

1 hour ago, GarrisonChisholm said:

*hears a celestial chorus ring out the golden C chord from Blue Beard*

 

Eureka!!!!!  What a discovery THIS is!

Thank you, you have given order to chaos.  Saves may now actually be useful.

It really is amazing how many things are in this game that significant numbers of players simply don't ever find out about because they're not very discoverable.

I was playing the game for over a year and a half before I found out about the absolute snap toggle in the editor (the F key).

[GarrisonChisholm]

16 minutes ago, Snark said:

It really is amazing how many things are in this game that significant numbers of players simply don't ever find out about because they're not very discoverable.

I was playing the game for over a year and a half before I found out about the absolute snap toggle in the editor (the F key).

"absolute snap"?  *...  ponders, decides he will experiment with 'F' in the VAB when he gets home from work...*

[DBowman]

Call out if you are not able to 'effortlessly' lay down an 'LKO to Mun Encounter' maneuver node. It sounds like you are okay, but it might just be you are focusing on interpreting the map view for now.

[JoeSchmuckatelli]

I've figured out some brute force LKO to lunar orbits.  I probably start losing efficiency in my gravity turns, and just keep muscling from there... But I have a probe in Munar orbit and another at Minimus, in orbit.

 

Playing with a wide circumpolar orbit mission, atm.  Learned that WHEN you launch is as important as the direction of launch.

 

Very slowly, I'm getting a feeling for normall / antinormal (have a pretty good understanding of how pro and retrograde burns affect the orbit) as well as some of the other maneuvers.  But preplanning and maneuver node work is coming on slow.

Edited December 15, 2015 by JoeSchmuckatelli

[DBowman]

In case it's useful for you, the way I go about Mun shots is:

• get to LKO
• put down a maneuver node. Doesn't really matter where, just ahead enough I won't over run it while I'm fiddling
• add prograde DeltaV until the predicted Kerbin orbit just kisses the Mun's orbit
• drag the node forward in time until a Mun encounter pops up
• by fine tune / fine fiddle with the time and prograde DeltaV you can arrange a free return, or just something with a periapsis you like.
• place a second manoever node at the Mun periapsis add retrograde deltaV until you get an orbit prediction.
• burn the nodes...

[Hysterrics]

2 hours ago, GarrisonChisholm said:

*hears a celestial chorus ring out the golden C chord from Blue Beard*

 

Eureka!!!!!  What a discovery THIS is!

Thank you, you have given order to chaos.  Saves may now actually be useful.

Haha You're welcome! I remember reading this a while on Reddit. It was some thread on things people didn't know about the game or something.

[Hysterrics]

35 minutes ago, JoeSchmuckatelli said:

I've figured out some brute force LKO to lunar orbits.  I probably start losing efficiency in my gravity turns, and just keep muscling from there... But I have a probe in Munar orbit and another at Minimus, in orbit.

 

Playing with a wide circumpolar orbit mission, atm.  Learned that WHEN you launch is as important as the direction of launch.

 

Very slowly, I'm getting a feeling for normall / antinormal (have a pretty good understanding of how pro and retrograde burns affect the orbit) as well as some of the other maneuvers.  But preplanning and maneuver node work is coming on slow.

Now, this is directly related to what you're trying to do, but I'm saying it just because it might be that last piece of the puzzle you need.

Prograde is the direction you are going. Retrograde is the opposite of the direction you are going. Burning Prograde will raise the direct opposite of you orbit(if you burn at your Ap you raise your Pe and visa versa). The fastest way to get to the Mun is to raise your orbit beyond the Mun's orbit, then move the node around until you get an encounter. Then you can just mess around with the markers until you get a nice flyby that you like. Without adjusting the flyby you might get something like you were talking about(the flyby that goes through to Mun), and this will cost you more Delta V and more to worry about.

[Snark]

3 hours ago, GarrisonChisholm said:

"absolute snap"?  *...  ponders, decides he will experiment with 'F' in the VAB when he gets home from work...*

Will keep this short, since it's off topic for the main conversation.  The rotator widget's snap is, by default, relative to the part you're attaching it to. If you turn on absolute mode, it snaps to absolute angle increments in world space, ignoring the shape of what it's attached to.  This is hugely useful for aligning landing gear.  If you've had airplanes that mysteriously want to swerve off the runway, this is why (and how to fix it).

[JoeSchmuckatelli]

Huh.  And I've been Shift+Adjusting them.  - Appreciate the info!