Craft Has Lost Ability to Create Maneuver Node...?

[Srpadget]

Background: Career Mode, fully-upgraded buildings. Lightly modded: EVE, KAC, KJR. Several missions going on simultaneously; one is a probe on its way to Minmus to fulfill a stationary-orbit contract--so the transfer burn was set up to give a very high Minmus Pe during flyby.

About 4 days away from Minmus SOI, roundoff error reached that critical value where it stopped being "intercept Minmus with high Pe" and became "no intercept at all". Sigh. This happens, I'm used to it, that's why I checked up on the vessel. I go to map view to set up a correction burn, and ... I cannot for the life of me get the little "put a maneuver node here" blue sphere to appear (or, obviously, the node-creation popup). Went back to KSC, reselected the craft in the tracking station. No joy. Picked a different vehicle that also happens to be Minmus-bound, and it's perfectly happy to set up a maneuver node. Back to the problem-probe, and nada.

Quit out of KSC, restarted the game. That one specific probe doesn't seem to recognize that maneuver nodes exist at all. Other vehicles are fine.

I note that I had a KAC alarm set up for the Minmus SOI entry. The map view widgets for that (Warp to SOI, Warp to PE, etc.) are still there in map view, but they're scattered all over the background...presumably because there is no change of SOI anymore? Makes me wonder if this is perhaps a bug associated with KAC, which I've only recently installed.

Is this a known bug? Is there a workaround/fix? Is there something I should look for (and edit) in my persistance file? Or will I have to tweak my orbit 'blind', as it were? (Such an annoyance, targeting Minmus's itty-bitty SOI with no maneuver nodes...)

The future of all Kerbaldom (or at least the future of this mission's profit margins!) depends on you!

Edited January 28, 2015 by Srpadget
Change thread to 'Answered'

[FleshJeb]

I had the same issue last night. Exiting to the tracking center and switching ships didn't fix it. Quitting the game and restarting did. I suspect it may be KAC. It keeps throwing me SOI warnings for ships that don't exist, or are landed.

FYI, I'm still playing 0.23.5

[Perry Apsis]

I have this behavior frequently, both in stock and with numerous mods, and for any number of versions up through .9, but quick-saving and reloading generally fixes it. I've never had it persist for a single craft.

[Kryxal]

Try making a node past periapsis and dragging it back into position.

[Agifem]

Confirming that i have this problem too. I can only create nodes for the next orbit. Only fix is to restart the game. It seems to be a new bug from 0.90.

Try making a node past periapsis and dragging it back into position.

I'll have to try that.

[Srpadget]

Shutting down and restarting the game Did Not Help. Still had a persistent inability to set a node for that ship. However, a variation on the theme of setting a node past Pe did: I happened to have an encounter with Mun during the descent back to Kerbin. I was able to set a node on the post-encounter conic, and drag it back around to where I needed it.

I don't think we know what causes this, nor do we have a GOOD solution... but this is probably the best we'll do. I'm going to call this Answered.

[LethalDose]

I've seen this issue many times on my Minmus transfers, and I don't think it's a bug exactly. Though, that doesn't mean it's working as intended.

I think what is happening in these situations has to do with how the the game renders predicted trajectories. If you get really big, ecliptic orbits, you can start to see that the predicted trajectories aren't rendered as smooth curves, but as line segments drawn between points (aka vertices; probably every so many radians/degrees around the orbit). The points seem to get further apart near Ap and closer together in Pe. I think what happens is that the game gets confused about how the cursor and the rendered trajectory interact when the points are far apart, resulting in the player's inability to create nodes near Ap. The vertices being far apart may also be partly responsible for the 'disappearing' intercepts as was described in the OP.

Or I'm totally off and rambling.

Regardless, you got the best advice possible: create a node elsewhere on the trajectory and drag it to the desired location. Panning to different camera angles can help occasionally, but I can't give any advice about how to reliably fix the problem this way. PreciseNode is a mod that may help, though I don't use it personally.

[NASAHireMe]

To answer, this is a known bug. KSP for some reason doesn't let you create a maneuver node after you get an encounter. Only workaround is with something like PreciseNode or MechJeb (you've gotta create a node, then null the values in the node editor, then drag it to where you want it).

[Srpadget]

Hrm...Not sure the bug is as straightforward as NASAHireMe implies. As noted in the OP, I've gotten accustomed to the here-now, gone-tomorrow nature of Minmus intercepts (especially high-Pe intercepts). And I frequently am able to create a node for an adjustment burn. Other times, it gets wonky and requires multiple attemps, or changing focus away from the ship then back, or or or...

If this is a known bug, it appears to be an intermittent one.