Kerbal Space Program

I tested this today after noticing my two space stations in my main save decaying without any inputs (all engines shutdown, RCS / SAS off).
There does appear to be some kind of phantom force that is causing both Pe and Ap to decay together, slowly but surely.
It stops decaying when time warp is engaged and immediately begins decaying again once back to 1x.
It seems to occur on all of my vessels when taken control of.

It also appears to be happening around non atmospheric bodies as well.
My Mun satellite test was harder to tell for sure, but it did appear over a longer period of time to drop slightly. I then decided to switch the test to a satellite I have around Tylo instead to see if non atmospheric bodies were affected, and it did the same as the Kerbin / Eve test.

Was able to reproduce on a mod free sandbox game in 1.1.1. This issue still persists with 1.1.2.

Happened to me in 1.1.1. The priority should not be LOW. This is a serious bug.

Apparently this is a known bug from NathanKell's Center of Mass update. Quoting from Dev Tuesday blog, "PhysX integrator has some issues with velocity at orbital speed so the Apoapsis and Periapsis are not constant when off rails".

I'm seeing something similar (v1.1.2), where a highly elliptical orbit (out to around Minmus's orbit) seems to be experiencing drag while at ~700km altitude. My apoapsis is falling by about a hundred meters per second. The anomalous drag goes away when I look through the tracking station or under time warp.

I haven't tested to see if lower orbits have it too, but this sounds just like what I'm seeing (it's just more obvious in a long elliptical orbit, I imagine).

I just saw a raising orbit (it was a satellite with ~P10000km ~A12000km), and the periapsis raised slowly ~1km per second.

Apollo13 wrote:

The priority should not be LOW. This is a serious bug.

Docking with this bug is horrible. Priority has to be raised.
Happens to me in 1.1.2 around the Mun a lot. Kerbal Engineer shows positive thrust while there is no engine on the vessel or reaction wheels.

I have this issue a lot... i send something to Mun with a PE of 25 k and when I slow down and configure some stuff on my craft or take some pictures, it has now dropped to 22k....

this happens on return too... my injection to Kerbin at 80 k ends up being 75 k by the time i get there and it continues to decay even in circular orbit

and it persists in 1.1.2

@everybody: Discussion is fine, but what is really needed here are save files demonstrating it happening, one is okay, multiple is even better. Heck, having too many uploaded to a bug report isn't really a thing.

I have a save that's experiencing this on both a near-circular orbit and a Munar injection transfer. Which files do I upload for you to see? is it the persistent.sfs?

The categorization "Aerodynamics" is misleading.
Even if drag is completely disabled in the debug menu the orbits still decay. Also the aero-information in the debug menu shows no lift or any other aero-forces.

krimsalt wrote:

I'm actually just going to upload the persistent file... that way if it is the one, you dont have to waste time waiting for me to reply

There are two things in flight doing this: (1) the MPL station, which is at about 150 km Kerbin orbit (but the PE has dropped now to 149); and (2) a Mun lander called Secunda Lander Mk1 which is on its way to Mun.

Go to each craft and watch the PE/AP from map view. For me, they decay about 1 km ever few seconds. This doesn't occur when viewed in the tracker

A quicksave would be preferred, but that's ok. Then again, a quicksave is just a named persistent save.

theonlyme wrote:

The categorization "Aerodynamics" is misleading.
Even if drag is completely disabled in the debug menu the orbits still decay. Also the aero-information in the debug menu shows no lift or any other aero-forces.

Yea, the physics category might be better, but I'll take a look first.

What I need you to do is to compare to 1.0.5, and in particular compare to single part vessels in 1.0.5.

smjjames wrote:

so, we'll just have to wait until they get back from vacation...

XD oh good lord...

Also I might add this makes getting into spherical orbits on one burn near impossible

krimsalt wrote:

smjjames wrote:

so, we'll just have to wait until they get back from vacation...

XD oh good lord... lol call them back!!

Also I might add this makes getting into spherical orbits on one burn near impossible

I get that it's a rather big issue and I would like to see it fixed myself, but I can't exactly make them come back from vacation.

Gonna bump the priority slightly higher, though IMO it would be medium-high, between absolutely game breaking and not gamebreaking. In an absolute sense, it is gamebreaking because it screws with the orbits of your active craft.

smjjames wrote:

I get that it's a rather big issue and I would like to see it fixed myself, but I can't exactly make them come back from vacation.

Gonna bump the priority slightly higher, though IMO it would be medium-high, between absolutely game breaking and not gamebreaking. In an absolute sense, it is gamebreaking because it screws with the orbits of your active craft.

ya i realized that. I was joking lol... in retrospect I guess it's difficult to portray sarcasm over text XD

In version 1.0.5, the energy in an orbit was conserved. The Ap and the Pe would shift on the focused vessel -- but when one was losing altitude, the other would gain an equal amount of energy and rise. The effect would swap back and forth between the two during an orbit.
Now, both the Pe and Ap decay simultaneously. One more than the other depending on your point in orbit. This is the difference.
But my 1.0.5 is gone gone gone, and I cannot do direct comparisons.

1.1.2 and noticed that the Ap drop (at about 5min to a 52km Pe (with a 52minute orbit) seems to be the same at both x1 and x4 physics warp.

edit - But on the next orbit it seemed to be the proper 4x higher. :/

smjjames wrote:

Just clarifying the ubject title to match the problem.

has there been any updates from the devs?

krimsalt wrote:

smjjames wrote:

Just clarifying the ubject title to match the problem.

has there been any updates from the devs?

No, they're still on vacation. I was just clarifying it to make it a bit easier to find as there was a duplicate and the atmospheric drag part was inaccurate anyway.

mbrouillard wrote:

I have noticed this bug as well. Additionally, I believe it is causing a problem with Maneuver Nodes as well.

Any Maneuver Node I create does not maintain a constant dV value as observed on the Nav HUD. The dV value increases at steady rate which seems to correspond with the decrease in value of the periapsis and apoapsis. The farther in the future the maneuver node exists, the more prominent the increase becomes. I believe the game is somehow trying to compensate for the expected future decrease in orbital altitude.

I've included a brand new save file in an unmodded install which contains a single craft orbiting Kerbin. A maneuver node with a starting dV of 0.1 m/s is set for a few hours in the future, and it will slowly increase over time. The increase is accelerated when physics time warp is utilized, but stays constant under normal time warp. Finally, if you mouse over the maneuver node in map view, it maintains the original dV value of 0.1 m/s.

I have very little experience with computer programming, but I believe these bugs are one in the same. If I'm wrong, I'll happily open a new bug file.

I'd say keep it here so that all of the relevant information is kept together. At least until it's proven that it's a completely separate bug rather than just a manifestation of this one.

Orbital Decay
I'm also experiencing this issue. My save file is here: https://gist.github.com/andytcox/0c8b6005e37de7477674af766e97c292 My install has a ton of mods, but the problem only cropped up recently. "Eden 1" is the craft that is my best example, its orbit decays .001 kms roughly every 5 seconds - its easy to see in the orbit info from Mechjeb. This also happens with other craft on Kerbin/Mun/Duna at varying rates(nothing wild yet but they are all high orbits).

VAB - Possibly Separate Issue
Around the same time this cropped up I also started to experience issues in the VAB where by the UI would become completely unresponsive, it seems like it happens as I'm going to launch or exit. UI hover effects still work and the kerbals continue to move around, but nothing you click has any effect, I still get a noise when selecting a part but no other response.

Timeline
I believe it started with the "Orbital Decay" bug and then the VAB happened in quick succession. I quit out of the game when I noticed the orbital decay and verified my game cache through Steam. On relaunching and going to the same vessel(Eden 1) the problem persisted, I figured it might just be some goof with the one station. I went back to the VAB and started assembling a new craft but needed to exit and verify something in mission control - when I got to exit the UI problem pops up. Reload and check orbital decay, reenter VAB - same issue. Reload go straight to VAB, at some point if I'm in there long enough - same issue.

Not sure these are related, but hoping this helps. I'll upload a CKAN list of mods as well once I'm back in Windows. I know these aren't directly supported, but the problems similar enough, I figured it might help.

Edit
I just copied everything over to Mac and verified the orbital decay appears to be the same as it is in Windows.

I'm having orbital decay problems as well. I'm getting a g force being reported by several mods that decays orbits over time. Burn nodes placed in the future show a gradual increase in delta v. If I time warp both the reported g force goes to 0 and the decay stops. I'm also having a lot of trouble with re-entry, all of my impact attempts come up short of predictions.

Yeah. This bug is still happening, and is not fixed in 1.1.3.1289. I haven't played in at least 9 months and came back to find that i can't orbit Mun without my AP and PE dropping rapidly together. It seems to vary from one burn to the next. I've also seen AP and PE increase steadily after a burn, albeit slowly (around 1m every couple seconds. There's no way to have multiple missions going on at once anymore and you waste fuel just to try and maintain an orbit. I'm not sure if it was a fluke, but one time i took it out to about 200k from the Mun in a circular orbit and it seemed to have no issues at all.

This is a pretty game-breaking deal.

You guys who report it still happening in 1.1.3(1289) -- you need to tell us for sure that you have gone into your main settings menu and turned on the "Orbital Drift Compensation" -- otherwise, OF COURSE its still happening to you. But it's no longer a bug unless you clicked that button.

bewing wrote:

You guys who report it still happening in 1.1.3(1289) -- you need to tell us for sure that you have gone into your main settings menu and turned on the "Orbital Drift Compensation" -- otherwise, OF COURSE its still happening to you. But it's no longer a bug unless you clicked that button.

Still occurs for me in 1.1.3(1289) with "Orbital Drift Compensation* selected. On another note, the option cannot be de-selected and is always returned to active when applying setting chnages.

Is this expected to work with existing saves, new games, or both?

bewing wrote:

You guys who report it still happening in 1.1.3(1289) -- you need to tell us for sure that you have gone into your main settings menu and turned on the "Orbital Drift Compensation" -- otherwise, OF COURSE its still happening to you. But it's no longer a bug unless you clicked that button.

Yes, I have orbital drift compensation turned on. It helps, but the problem is still there. Sometimes it doesn't cause a problem and other times it is very apparent. Besides the dancing orbital numbers I also get some form of drag in space. I have not been able to determine a pattern to why it's better sometimes and worse others. I have to play the game in time warp to get any sort of consistency, and spend as little time as possible in real time. Makes accurate re entry almost impossible.

gloriouscult & blackgold: there is a slightly different form of this issue that involves landing legs. Landing legs seem to give your craft small random pushes around. On the craft that you are seeing this on -- do they have landing legs?

bewing wrote:

gloriouscult & blackgold: there is a slightly different form of this issue that involves landing legs. Landing legs seem to give your craft small random pushes around. On the craft that you are seeing this on -- do they have landing legs?

Yes, usually, although craft without them have the problem too. Phantom forces are always reported but only sometimes effect orbit. I recall reading that orbital drift compensation could be adjusted in the cfg? Maybe I need to make mine stronger.

bewing wrote:

gloriouscult & blackgold: there is a slightly different form of this issue that involves landing legs. Landing legs seem to give your craft small random pushes around. On the craft that you are seeing this on -- do they have landing legs?

I've got orbital draft compensation enabled too and the specific craft I'm seeing the issue with has landing legs. Not sure yet if it happens without them.

Have a lots of mods here, and landing legs, and i get a lot of orbital decay in orbit around dres. I thought this bug was closed.

Just checked for orbital drift compensation. It is switched on, i never changed it. And there is no way to switch it off.