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Orbits sometimes change after time warp


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I've been playing KSP since 0.23.5, initially without any mods, now with the following:

Editor Extension

Enhanced NavBall

Kerbal Engineer

Precise Node

TAC Fuel Balancer

Kerbal Alarm Clock

The problem I'm talking about here is returning to a ship that's been on rails for a while, only to discover that it's way out of its original orbit. I'm all but certain that I saw this in 0.23.5 with no mods installed. At a minimum, it would be with only KAC installed, which I now consider essential to sanity.

I recently had it occur twice within a couple days in the same career. The first time, a ship was on course from Duna to a Kerbin intercept, but after controlling a number of other ships and time-warping, I found it was no longer on that course at all, but instead was in a strange orbit with perihelion inside of Eve's orbit and aphelion inside of Kerbin's orbit. I backtracked among the available saves (KAC's backup on ship jump feature comes in handy) until the orbit was back where it belonged, and proceeded from there (with plenty of repeat burns and time-warps, each followed by checking the return ship's orbit). The second time, it was a different ship which was on course from Kerbin to Duna, with a maneuver node at an inclination node to adjust the intercept. When that node came up in KAC, I found the orbit was changed significantly, so that the ship was no longer intercepting Duna. I again backtracked until I found a save with the correct orbit, and when warping a particular ship to redo its burn, found that the orbit changed again. I was able to repeat this process several times - reload the save, warp at top speed for 30 days, see changed orbit. It only happened when in ship view mode. When in map view, the orbit did not change.

Here are the before and after orbit characteristics as shown by Kerbal Engineer:

161nrxt.jpgslppqr.jpg

I'll link to the graphical map view sections, since they're a bit on the large side: Before Warp and After Warp. As you can see, the ship was on an intercept course with Duna before the time warp, and falling far short of Duna afterwards. The change to the orbit was the same each time I repeated it.

Figuring I had a reproducible case, I decided to exit KSP and deactivate all mods to see if I could replicate the bug in stock. Unfortunately, I could not. I tried several times to do a 30d time warp with the same ship in view, but the orbit didn't change. Moreover, when I reactivated all the mods and relaunched, the same save game no longer let me reproduce the orbit change. So it seems it was tied to the running game state.

Has anyone else encountered this problem?

If I find a repeatable situation again, would it be useful to get a process dump of KSP in that state?

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Yes, KAC halted the warp. Can you explain what you mean by higher than normal and stock warps? I don't have any mods that affect warp speeds.

My Time Control mod allows you to set up custom warp rates, which can be much higher than stock. When KAC exits warp, it does so in a manner that is a bit more "crude" than how the game typically exits warp, and the combination results in a glitch where orbits would be thrown off. I'm surprised that this effect is triggering with the standard warp rates, the best thing to do is inform TriggerAu about it on the KAC post: http://forum.kerbalspaceprogram.com/threads/24786

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Hey there guys... this happens quite often if you transfer between two SOI while warping... this particular problem that I'm talking about can be fixed by returning from warp to normal speed a bit before the transfer occurs... then you have to wait until the transfer to the other SOI happens and when you hit the other SOI, you can time warp again :)

(why do I get the feeling that I made this explanation too hard to understand? :D)

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I know what you're talking about, which is why I let KAC add SOI alarms by default, and try to go through them with the active ship at normal speed.

However, in this case, neither the ship I'm controlling nor the ship that has its orbit changed undergo any SOI changes during the time warp in question.

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Did add some notes about one alarm type that can cause it in KAC v2, but if I'm reading you right it sounds like the orbit is changing when you slow the warp your self?

From my understanding whenever you drop a vessel out of warp KSP sets up the orbit in physical from Rails - if you jam it from a hi warp level to 1x (by not having the transition period) then rounding of values vs time can jump the orbit a bit.

Any chance you have a save file still with the issue?

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The orbit changed without me adjusting warp speed - KAC did all the adjustments. And it only happened when in ship view, not on the map. And it wasn't the controlled ship which had its orbit changed.

I do still have the save, but I can no longer replicate the orbit change. It was apparently tied the running game state.

All the other cases I've encountered (somewhere around a half dozen) in the past were also with ships not undergoing SOI changes and on rails the entire time. I'm leaning towards it being some kind of buffer overrun. If I ever find a reproducible case again, I'll run through more scenarios, and also dump the process memory.

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Cool Thanny, I have been working yesterday on reversing the maths that occur during warp changes so as to make KAC have as little impact as possible as well as catering to non-standard warp rates (sorry it took so long @Xaiier).

Hopefully that will remove any other ways KAC could be the cause of this kind of behaviour, but as others point out that orbit change stuff has been seen in stock games too

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I know what you're talking about, which is why I let KAC add SOI alarms by default, and try to go through them with the active ship at normal speed.

However, in this case, neither the ship I'm controlling nor the ship that has its orbit changed undergo any SOI changes during the time warp in question.

It may be the case that warping through any SOI change, of any craft, anywhere in the save, can have deleterious effects on any other orbit in the save. If so, then it would therefore be irrelevant that the craft in question experienced no SOI changes during your warp period. Your steps taken, by your description, seem to account for this however.

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Cool Thanny, I have been working yesterday on reversing the maths that occur during warp changes so as to make KAC have as little impact as possible as well as catering to non-standard warp rates (sorry it took so long @Xaiier).

Hopefully that will remove any other ways KAC could be the cause of this kind of behaviour, but as others point out that orbit change stuff has been seen in stock games too

Good to hear!

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I have sometimes experienced strange changes on orbits. However, not during couple of last versions. Typically orbit changes so little, that it is difficult to see if you do not focus to ship and you notice it too late when KAC stops time for SOI change or correction node, and need hundreds of meter per sec corrections. Couple of times the orbit have changed to ridiculous. One time ship changed its velocity almost negative on transfer orbit to Jool. I did not notice it immediately, but at some point I noticed that hell, my ship is on retrograde orbit around Kerbol.

It is very annoying to notice that this bug have ruined some mission, but because these have been very rare events (once per several hundreds of playing hours), I have not tried to find out what causes it. I asked once here but nobody had solutions.

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I'm not so sure that it's all that rare.

Due to some glitch I have to attribute to 0.25 coming out while I was loading the game (I launch outside of Steam), I found myself losing a ship due to a spurious missing part. After going back to a previous save, I found that the ship in question had actually missed a maneuver node. In going backwards previously to reverse an orbit change bug, I went back far enough to undo that node for that ship, but because KAC stores its alarms in a separate file, the alarm didn't come back with it (which will be a problem of the past when I switch to v3). So now I had to go back further, and the first save I found before that maneuver node (3h+ before it) had the orbit bug. That is, the orbit for that ship was off where it was, and it would no longer intercept Kerbin after the maneuver. The next nearest save was 60 days previous, where the orbit was on track. So that's three cases of a changed orbit in this career that I noticed.

The best strategy I can see to avoid it is to always do high speed warps on the map screen, and look for screwed up orbits afterwards - the ones that matter will typically be obvious intercepts that no longer reach their targets.

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