Why does my ship have two trajectories?

[Motokid600]

Im on a ballistic return from the Jool system and I managed a 30,000,000km Kerbin periapsis after the ejection burn. But now I have a massive problem. For some reason in the map view there is a purple trajectory plotting my orbit around the sun which doesn't match up with the crafts actual heading. The blue trajectory leads right to my periapsis meeting the purple. And for some reason it will only let me select the purple line when I go to add a maneuver node. Once I do this it gets even more wacky and instantly shows the dotted green line on yet another different trajectory.

The truly crippling part is the fact that no matter how much I edit a maneuver node my Kerbin periapsis will not change what so ever. Since I cannot see the changes I make to my path my mission has a real problem. Any advise? Ive been using the new advanced maneuver node mod and its been a god send, but if anyone thinks that could be the issue let me know. Ill post a pic real soon.

This is what happens the moment I add the node.

Edited August 23, 2013 by Motokid600

[Rhomphaia]

Blue trajectory is your current trajectory. Purple one is the one you will have after Kerbin encounter and escape.

[kurja]

You see two trajectories because your path enters kerbin's soi? That encounter will put you on the purple trajectory, blue being your current path. If you put a node on the purple trajectory the maneuver is being planned for your next orbit so the Pe shouldn't change, as far as I can tell.

As for why you can't put a node on your current path... I've no idea. Do you have a bit of fuel to spare? Just burn a tiny amount in radial in direction and see if your Pe comes down?

[Motokid600]

As for why you can't put a node on your current path... I've no idea. Do you have a bit of fuel to spare? Just burn a tiny amount in radial in direction and see if your Pe comes down?

This is the true problem. Yea I can change it by burning engines. I guess im just going to have to manually adjust it. Going to be hard to fine tune.. NO idea whats going on I just cannot select the blue line.

[Yasmy]

I have had the same problem selecting the current (blue) trajectory for placing nodes,

when the post-encounter trajectory is very similar to the pre-encounter trajectory.

The purple trajectory is the post-Kerbin encounter trajectory,

which is useful for planning gravitational assists and various other things.

There are two potential remedies:

1) Zoom way in, and mouse around until a blue sphere appears on the trajectory,

rather than a purple sphere. Then click as usual.

You may have to swing the camera around a bunch and zoom in and out.

Sometimes it helps to create the node a few hours away from your vessel, then

drag the node to where you want it.

2) I haven't used that particular maneuver node editor that you are using, but it looks like

you could change the time in the top box.

I'm sure there is a quick way to find the current time in the game, but I don't know it at the moment.

You can quicksave, then open the quicksave.sfs file and find current time.

Right after FLIGHTSTATE in the quicksave there is a line which says something like:

UT = 546698.584827724

Add a couple thousand to that number, and enter it into the maneuver node editor.

Happy trails

[Stratoroc]

The lines are so close that kerbal can't resolve which trajectory you intent to click on, try zooming in on your ship as much as you can while the trajectory separation is greatest and see if you can select the blue line then.

[RSwordsman]

My relative inexperience would tell you to burn retrograde once you get into Kerbin's SOI in the hope that you get under escape velocity and don't fly out again.

[CoriW]

This actually happens to me quite often when navigating interplanetary space, pretty much what happens is because an interplanetary scale is so big KSP's Patched Conics has trouble trying to plot an exact trajectory.

You'll notice if you zoom in as close as you can to your ship on the map view while in interplanetary space your current trajectory (the blue line) will typically be somewhat distant from the actual location of your ship, this is a perfect example of the current limit of the Patched Conics accuracy. Now what this also means is that when you try to select your trajectory to place a maneuver node, your not actually clicking directly on the trajectory, but instead clicking somewhere approximately where the trajectory is; Due to this if you have two trajectories (the blue and purple lines in your case) that are relatively close to each other in interplanetary space, these inaccuracies and approximations overlap causing only one of the two trajectories to be selectable for placing a maneuver node.

So that is why your seeing this happening, however there is one work around.

Inside of your KSP root folder there is a file called "settings.cfg", if you open this file with Notepad or Notepad++ you can edit KSP's current settings. Now the reason this overlap is happening is because the Patched Conics are projecting 2 SoI changes ahead of your current trajectory, however this can be easily changed in the "settings.cfg" file, simply find the setting called "CONIC_PATCH_LIMIT" and change it to 2.

So the up side to this fix is that you will no longer have any issues with multiple interplanetary trajectories overlapping and causing problems, however the down side is the Patched Conics will only display 1 SoI change ahead of your current trajectory, instead of the previous 2.

I hope this helps.

EDIT: On a related note, here is a link to a YouTube video by xPDxTV explaining the "CONIC_PATCH_DRAW_MODE" and "CONIC_PATCH_LIMIT" settings. (

) Edited August 23, 2013 by CoriW

[LeadMagnet]

My relative inexperience would tell you to burn retrograde once you get into Kerbin's SOI in the hope that you get under escape velocity and don't fly out again.

yup......in fact, I would get the apoapsis to under 50K meters and aero-brake in Kerbina atmo. The purple path will definitely vanish then!

If your finding these "extra" path's confusing, you could edit your KSP configuration file to reduce the number of paths projected. Look for the entry CONIC_PATCH_LIMIT. It should be set to 3, I set mine to 5 (more paths). Try a 2 or even 1.

[LeadMagnet]

...Inside of your KSP root folder there is a file called "settings.cfg"...simply find the setting called "CONIC_PATCH_LIMIT" and change it to 2...

Like minds!

[kurja]

My relative inexperience would tell you to burn retrograde once you get into Kerbin's SOI in the hope that you get under escape velocity and don't fly out again.

That would use huge amounts of fuel/delta v in comparison to adjusting the orbit where the ship is now.

[Tiron]

That would use huge amounts of fuel/delta v in comparison to adjusting the orbit where the ship is now.

Huge is distinctly relative: Such a change at the outskirts of Kerbin's SOI is going to take very, very little Delta-V to accomplish. Yes, it'd take even less now. But it's harder to make the adjustments accurately at this point.

To the OP: What you're seeing, and the reasons they're different colors, is the result of the game predicting your orbit assuming you don't make any maneuvers. You've successfully set up a Kerbin Encounter, and what's happening is that Kerbin's gravity is going to alter your orbit somewhat: The Purple is a prediction of what it'll end up as. The points where you enter and leave Kerbin's SoI are indicated by small circles on either side of it in your screenshots. If you were to change focus to Kerbin and Zoom in, you would find that your trajectory inside its SoI is indicated with a third color: A yellow line that bridges your current trajectory and the purple one.

[Motokid600]

Thanks again everyone. All turned out well. I was able to finally get a node in the blue trajectory after messing around with manual burns. Took a 30km periapsis for an aerobrake capture. O.o

You can change conics on the spot with that mod by the way. The red buttons at the bottom. If you don't have it I highly recommend it. That mod paired with kerbal alarm clock takes away all the frustration with nodes.