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Maztrim

Orbit constantly decaying

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Hello everyone,

     So this started after 1.1.2. Basically any craft I put into orbit, after cutting engines and turning off SAS, will continually drop in orbit. 

At first I thought it was one of the mods I was using, so I deleted all mods and did a fresh install.  The problem still persists, regardless of craft. 

 

Is this the "Floating Point Error" bug I'm experiencing? If so, why did it show up with 1.1.2?  I've had KSP since .90 and this is the first time I've experienced this bug. If it's inherent in 1.1.2, is it possible to switch back to a previous version?  

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I note that 'bewing' marked this as fixed 11 days ago, and then 'alexanderweiss' reported having the same issue in 1.1.3 ten days ago.

I'm just commenting to note that I am also having this issue under 1.1.3, although it's far more pronounced in my experience (my 30x30km Munar orbit dropped to a 30x9km orbit in about two minutes!).

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I can also confirm. Orbits are still decaying/behaving wildly on my install.

Unsurprisingly, the issue seems to only occur when I'm flying a craft that has (sigh) wheels on it.

Sadly, with Devs dropping like flies around here, I'm starting to worry that KSP is never going to get fixed and "this is it." Especially with the console versions being worked on. It all feels very "swan song" to me.

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Please provide more specifics. In general, orbital stability has been reportedly better on 1.1.3.

"It's worse for me" is somewhat useful, but doesn't allow us to actually look into the issue. A save file is the best bet for this case, or maybe a .craft file.

Cheers

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Can't get you any files at the moment (work), but basically what's happening is that any craft with wheels on it is experiencing either rapid (I'm talking FAST) orbit decay or wildly behaving orbits (big, then small, then huge, then sub-orbital, then big, etc etc)

I suspect the wheels are creating some kind of phantom force similar to the "Kraken Drive" because so far this issue has been limited to crafts with wheels. My theory is that wheels that have their brakes disabled but are still powered are causing some form of incorrect and random thrust.

Also, really embarrassed about making a comment about devs leaving left and right and then having one reply directly after me. Oh internet, you cruel mistress, you.

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10 hours ago, Claw said:

Please provide more specifics. In general, orbital stability has been reportedly better on 1.1.3.

"It's worse for me" is somewhat useful, but doesn't allow us to actually look into the issue. A save file is the best bet for this case, or maybe a .craft file.

Cheers

Ok, here's my persistent.sfs filehere's my quicksave.sfs file, player.log file, and KSP.log file.

My experience varies from what @Greenfire32 is having...

(side note: my craft don't have wheels on them.)

 

 

Just last night, I was flying past the Mun on the way back from some other mission, and a contract popped up to plant a flag on the Mun, so I figured I'd accept the contract and do it with the returning vehicle. Of course, this meant that I had to build and send an actual lander to dock with the returning spacecraft so that the spacecraft actually could land on the Mun (it only has a nuclear engine, so I needed engines with higher thrust...)

Anyway, both the original spacecraft and the lander itself were both in stable Munar orbits. It's just once the two craft got close together (i.e. within a kilometre, I'm guessing) that the periapse of the lander itself began to decay. Interestingly, the original spacecraft (which was built and launched in v1.1.2) is having no issues whatsoever - its orbit isn't decaying at all.

 

Having thought about it, this is also the first spacecraft I have built, launched, and sent to the Mun in 1.1.3.

Would it be worthwhile testing to see if a new craft orbiting Minmus has the same problem?

 

Thanks in advance for your help. :) 

 

Update: I quit and reloaded KSP. Interesting to note the orbits don't change in the tracking station - only when you're actually in control of the vessel.

Also interesting - I had a probe in orbit around Duna. It has somehow managed to take itself out of Duna orbit and is now floating around interplanetary space... god only knows how that happened, because the orbit was definitely stable to begin with.

I'm gonna downgrade to 1.1.2 for the moment...

Edited by DavidHunter

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Also noticed this problem popping up again the other night. Haven't had a chance to do thorough testing and this is all from memory but I had a small probe in a low, slightly eccentric and inclined orbit (<30km) around minmus.

I noticed while at/near the periapsis and apoapsis, the opposite side would vary in altitude while in normal time mode. Over the course of 30 seconds it swung wilder and wilder up and down to the point where it was gaining or losing hundreds of meters every few seconds. On rails time warp would stop it and seem to temporarily dampen the wobble after returning to normal time.

My craft in this case had no wheels as the others have suggested might be the cause. It was a okto1 probe core with two oscar-b fuel tanks and an lv-1 ant engine. tri-symmetry lt-05 micro landing struts, tri symmetry 1x1 solar panels, some small science attached to the probe core and a z-200 battery attached to the top node. Only odd thing is a tt-38k radial decoupler than remained on the side of the probe after detaching from a larger probe launcher. I only say odd because it makes the probe slightly off balance and causes minor issue with holding a course during a long burn.

Edited by bb12345

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I had probe with weird fluctuations with both AP an PE.  I thought both were acting a little wonky at the same time but it was weird.  I had to go look up to make sure the Mun really didn't have an atmosphere added or something.  But both numbers were going up and down but not by a huge amount.  I think my orbit was around 55km or something?  Though I might have noticed it after dropping my PE, I can't be certain.  I was able to land the probe ok though.  I had landing legs but no wheels.  Unless you all are talking about reaction wheels and I may have had one of those on it.

My install is not unmodded, just saw this thread like I did with the EVA bug thread.  This was a probe though, so a different ship than in the other thread obviously.

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I think I may have found a possible source for this bug.

I had a vehicle in Minmus orbit that was exhibiting this behavior.  When I zoomed out in map view enough that Kerbin was also visible, and watched the orbital period on MechJeb, I noticed something. If my ship was moving towards Kerbin in its orbit of Minmus, its orbital period (and apoapsis) would steadily increase.  However, when it was moving away from Kerbin the orbital period decreased and the periapsis dropped.  It's almost as though the ship is getting a gravitational tug from both Minmus and Kerbin.

Here's the cool part.  I sent the ship back to Kerbin.  The orbit decay bug stopped the moment the ship left the SOI of Minmus.  Orbital period has not changed by even 1/100th of a second.

If my ship was indeed getting a tug from Kerbin as it orbited Munmus, then most of that acceleration would be canceled out by virtue of co-orbiting Kerbin with Minmus.  However,  the closer the ship is to Minmus, the more its velocity relative to Kerbin would differ from an orbital velocity at Minmus's distance from Kerbin.

Likewise, if a ship orbiting Duna was also getting a tug from Ike or the Sun, it's pretty easy to see it getting flung right out of the Duna system.  Or if a ship orbiting Kerbin is also getting a tug from Mun or the Sun, there goes your finely-tuned 73 km orbit.

So, if you're seeing this bug, zoom out and have a look at the location of the primary around which whatever body you're orbiting is itself orbiting.  That is, if you're orbiting Eve and see this bug, zoom out and check to see if the Sun might also be affecting the orbit.  If I'm right and this behavior is consistent with this bug, then that will give Nathan and the other devs a place to start looking.

Edited by edrobotguy

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FAR uses doubles everywhere and calculates drag based on total ship form not hierarchy - perhaps this could be worth checking out with problematic craft...

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4 hours ago, Kerbal101 said:

FAR uses doubles everywhere and calculates drag based on total ship form not hierarchy - perhaps this could be worth checking out with problematic craft...

Sorry, I'm not exactly sure what you mean.

Do you mean FAR could be causing the issue, or do you mean it may be able to fix the issue?

If you mean FAR might fix the issue, I can confirm that it cannot - I haven't played Kerbal without FAR installed for several years...

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On 7/23/2016 at 5:33 PM, DavidHunter said:

@Claw, has there been any news about a fix for this issue by any chance?

Thanks. :)

No, sorry. I lost track of this thread so I haven't looked into this yet. I will keep this thread open here and try to take a look at the saves soon! Thanks for the reminder. :) 

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13 hours ago, Claw said:

No, sorry. I lost track of this thread so I haven't looked into this yet. I will keep this thread open here and try to take a look at the saves soon! Thanks for the reminder. :) 

Thanks. Let me know if you need any further data. I haven't opened KSP since encountering this problem so my save game state is in the exact same state it was in before. :)

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Well, I tried to load the save but it's full of mods. That in itself isn't a big deal, but I haven't taken the time to install the mods in question to have a look.

We are tracking the bug report, however, there's not much to report at the moment.

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