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Gordon Fecyk

Landed craft bounces on saved game load, KSP 1.3.1

Question

This seems to have been introduced in KSP 1.3.1. Some wheels bounce harder than others, but all have some bounce.

Spoiler

 

The large gear seems to have the least noticeable bounce, but it's quite noticeable at Minmus. The others are very noticeable back at KSC. The small gear seems the most stable.

To avoid scrolling down, here are current bug reports filed on this problem. Please upvote these.

https://bugs.kerbalspaceprogram.com/issues/16159 <- Surface collisions on physics start

https://bugs.kerbalspaceprogram.com/issues/16090 <- Related to prerelease bug #15796 Non-active vessels jumping on load still happening on 1.3.1

A workable workaround to this problem, courtesy of @whale_2

 

Edited by Gordon Fecyk
Added link to add-on that works around problem

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@dark_reef

Yep, I can reproduce it mod free, fresh copy of KSP.  My earlier complaints in this thread were with a GameData full of mods, but just for this I used a fresh copy of KSP. 

I also ran a fresh copy of KSP, used the same stock vessel but with Vens revamp. Same issue. Then I restarted KSP, started a new sandbox game (still with Vens) made the same vessel and no issue. So it seems the bug is inconsistent. This may explain why you think you found a solution when really it was an inconsistency. My bet is that you will see it again on another vessel later on.

Thanks for going through the trouble, but your testing just proves that the issue happens with and without mods, which considering it’s in the stock game, is no surprise. 

Also, next time you troubleshoot, remove half of your mods, if the problem persists, remove half of the remaining mods etc etc rinse and repeat... when the problems stop, the mod causing issues will likely be in the last batch of mods you removed. Now all you have to do is rummage through a handful of mods as opposed to 60. No way should it take 6 hours to troubleshoot something pertaining to mods. 

 

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I can also confirm in stock 1.3.1.1891(x64).

I also noticed that when you retract/extend the landing gear of a stationary vehicle, the wheels collide through the surface, and the craft appears to rest on the wheel axles rather than the wheels themselves. Whenever the gear is extended and locked, the craft bounces up from the axle height to the wheel height, sometimes quite violently. The change in surface interaction from axle to wheel may also be happening during loading of a save, resulting in this bouncy behaviour.

EDIT: On further investigation, the behaviour I described above seems to happen only with the "Large" and "Extra Large" landing gear. The "Small" and "Medium" landing gears don't clip through the ground during retraction/extension, however they do bounce on completing the extension sequence, particularly the "Medium" landing gear which also seems to hover above the ground during retraction/extension.

Edited by Yakuzi

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I did remove them in sections to help speed up the process. But my drive is not the fastest so most of the time was just waiting at the splash screen :) And yes it was one of the last ones that I tried.

I did figure out a few more things. The problem does not see to be there when not on landing legs or having the drills retracted. So if I raise the legs and is it sitting on the engines or if it falls over it does not seem to do it.

I guess my question is what can I do in the meantime? I love playing this game and have quite a bit of time in it so far so is there any workarounds? I noticed that there are some stabilizer legs that have the ability to be attached to the ground that I have not tested yet. Or is there a way to build the crafts that I land on low gravity planets so they dont kerbounce?

Obiviously you guys see that it is a bug so do you guys know what the time frame of it possibly getting fixed or if it is even being worked on? I was even thinking of restarting my career in 1.3.0. I noticed that mechjeb landing seems to actually work in 1.3.0 also. 

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1 hour ago, Yakuzi said:
1 hour ago, Yakuzi said:

may also be happening during loading of a save,

It also happens when flying another craft from say orbit and landing near the one(s) that are on the surface. As soon as you come into view all of them jump and you get to watch the destruction from a far. I had 4 landed in the same location on Minimus when when I tried landing a 5th they all jumped and most landed on their sides.

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1 hour ago, Yakuzi said:

On further investigation, the behaviour I described above seems to happen only with the "Large" and "Extra Large" landing gear. The "Small" and "Medium" landing gears don't clip through the ground during retraction/extension, however they do bounce on completing the extension sequence, particularly the "Medium" landing gear which also seems to hover above the ground during retraction/extension.

The Falcon Landing Gear Small will do it also.

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I may have a solution for the landed craft for now. I tested the "Landing Stabilizer" legs and they have a "Toggle Ground Tether" option. So they are somewhat bolted down and cannot bounce???

Is there another way to bolt stuff down with something like KAS or putting down something like the asphalt that interacts differently? 

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@dark_reef   even if you bolted them down, something else I've noticed...  

We notice the gear drops down into the ground and then gets thrust up.  What also occurs is, sometimes the bounce up appears to be not as bad for some reason.  What actually happens in those cases, is the landing gear actually gets thrust up into the craft and becomes permanently assigned to a new position as if the craft had incurred a particularly rough landing and damaged it's gear.  So basically as you play, and your craft bounces around...  it is also randomly taking damage that compounds over time.

I've noticed that at the KSC on the tarmac, I can retract the offending gear on some craft and let them sit on the ground and it does seem to avoid the issue.  On low-G planets I've tried similar tactics with other craft and the results were unfortunately catastrophic.

As the 1.3.1 update did absolutely nothing for me but introduce problems...  My best course of action (and recommendation for others) is to rollback to 1.3.0 until the next update comes out and hopefully fixes it.

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So far the Landing Stabilizer legs seem to be working. I was able to land on IOTA, "Toggle Ground Tether" and time warp until all tanks were full. You can see the craft try to jump when coming out of warp but is suppressed by the ground tether. Not sure exactly what the ground tether is doing but it seems to work at least for now. I also noticed that they do not retract with G so they are not considered gear and are not treated the same by the physics engine???

Is it possible to make a mod for all gear to have a "ground tether option"?

46 minutes ago, XLjedi said:

On low-G planets I've tried similar tactics with other craft and the results were unfortunately catastrophic.

I noticed that as well. On low g planets the gear would usually just explode instead of bouncing.

Edited by dark_reef

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59 minutes ago, XLjedi said:

My best course of action (and recommendation for others) is to rollback to 1.3.0 until the next update comes out and hopefully fixes it.

I only started playing recently so I am stuck on 1.3.1 unless there is a way to move a save back to 1.3.0.

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52 minutes ago, dark_reef said:

I only started playing recently so I am stuck on 1.3.1 unless there is a way to move a save back to 1.3.0.

Yeah, not much you can do there... except hope they fix it soon, and avoid the offending parts.

For now, maybe just focus on craft design and tinkering around in sandbox mode until we get a stable version to advance career mode saved games.  Maybe even participate in a challenge or two? 

Would be nice to get an update on this here... but I guess I'll have to go open an account on their bug tracker system to see what (if anything) is being acknowledged and worked on.

 

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I did some testing and the landing stabilizers seem to work after they are "tethered " to the ground. So I restored an older save and will redo some of the big lander with a design that uses the stabilizers instead of landing legs and see how it goes.

From the sounds of it the problem can come and go but for me has always been (at least on low grav worlds).

I am still learning how everything works so I have already restarted a few times but I will see if I can keep this career going.

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I am finding that being on a completely flat surface is EXTREMELY important. If you are not a a flat surface facing straight up do not save, do not time warp, and do not change focus back to the space center or a ship out of viewing range. If you need to save just bump into the air before saving or find a large flat area. I am building a base right now on Iota and I found a large completely flat area that has ore so we will see how it goes.

Edited by dark_reef

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One trick I've used with refueling to manage the Ker-bounce damage is...

As mentioned previously, when you come out of accel time the craft does not always appear to bounce as much, but only because the gear got jammed up into the hull and absorbed the bounce with damage.  For me it seems to happen most often coming out of accel time after refueling.  I have noticed there is less chance for gear damage if coming out of a save, as opposed to accel time.  Sooooo...  if you accel time to refuel, just make sure to do a save AFTER you harvest the fuel, but BEFORE you come out of accel time!  Then to exit accel time, just press ESC and load the save.  You get your fuel, and the Ker-bounce is less likely to damage your gear.

 

 

 

 

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On 11/16/2017 at 6:06 AM, dark_reef said:

I am finding that being on a completely flat surface is EXTREMELY important. If you are not a a flat surface facing straight up do not save, do not time warp, and do not change focus back to the space center or a ship out of viewing range. If you need to save just bump into the air before saving or find a large flat area. I am building a base right now on Iota and I found a large completely flat area that has ore so we will see how it goes.

That does seem to be a problem although I don't know if it is the main cause. The steeper the inclination, the bigger the jump. 

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On 11/15/2017 at 10:06 PM, dark_reef said:

I am finding that being on a completely flat surface is EXTREMELY important.

The only time I ever got a wheel-jump was after parking on a 30-degree incline, so I think you're onto something.

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Why are we arguing the incline of the terrain when my video clip demonstrates this occurring right beside the runway on KSC grounds? It doesn't get flatter than this, except for the runway itself. And yes, craft bounce quite happily off that as well.

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On 12/20/2017 at 9:33 PM, Gordon Fecyk said:

Why are we arguing the incline of the terrain when my video clip demonstrates this occurring right beside the runway on KSC grounds? It doesn't get flatter than this, except for the runway itself. And yes, craft bounce quite happily off that as well.

In support of the topic I submit that there are circumstances and degrees of bounce thereof. see clip https://www.twitch.tv/videos/211503705##
In my clip when entering the scene, If The landing gear has springs, then there is plenty of bounce, wheels especially. But a solid landing leg next to none. You can see with the landing legs5:00 (with springs set to normal) how they start under the terrain and then bounce even though that is a light craft. And it shouldn’t bounce at all. it is worse on Duna and any other body than on Kerbin if that helps.
The cargo haulers both loose the front steering landing gear, 10:47 if I let it bounce and don't help. (all wheels were aligned to the same height) and were tested on Kebin to be fine and able to handle a bounce during test landings and unloading where I switch to the cargo vehicle, all On terrain that is Way less than 30degrees it has happened.
I am very convinced this issue is understood, but maybe not what combinations are needed to correct it just yet. as it is a collison's issue, we deal with this in editors like unreal all the time when planting anything even spawn points can be set below terrain world and bam things get crazy. the the calculation appears to be off on items that can have expanding contracting features, maybe it cannot determine what state it is in upon entry.
It has gotten worse in versions but I had bounces in 1.22 as well. So much so a rover flipped out when I left the flexing joint loose and that thing bounced and got destroyed.. Fun to watch. So for me flat surface is always best. it was just a rover on Duna 

hope this info helps

Jammer

Edited by Jammer-TD

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On 16-11-2017 at 5:06 AM, dark_reef said:

I am finding that being on a completely flat surface is EXTREMELY important.

In my experience there has always been a small bump when loading or time-warping a craft on the surface. It is only now that I had a rover jump +-200m from the surface. Said rover was parked on a 30 degree incline on Bop.

I managed to halve the jump height to about 100m by spamming the escape button when loading the craft. (Which luckily enabled me to finally land it without bits exploding.) During the pause of the escape menu I could see the wheels (TL-2R wheels) sink in the ground for about 60% before the jump.

Another rover of mine on Ike landed at a 2 degree incline only jumped 2m upon loading. Having said that, the 2 rovers differ immensely in terms of weight. The Bop truck is about 35-40 tons and the Ike rover about 10-15 tons I guess. Both use the TL-2R Ruggedized Vehicular Wheels. (Bop=16wheels Ike=4wheels). 

EDIT: Did some testing with the beforementioned Bop Rover. I loaded 2 saves which allowed me to test the rover at +-45 tons and at +-60 tons and did 5 quickloads on different levels of inclination on Bop. This is supposed to give some insight on the effects of inclination and mass of parked rovers/wheeled outposts and their jumps upon quickloading. 

---------------------------------------------------------------------------------------------------------------------------

+-45 tons

10° -3x No noticable bump.
       -2x Front wheels jump 2m.

15° -4x 3m-6m jump.
       -1x 12m jump.

20° -1x front wheels jump 3m.
       -4x jump 14-18m.

25° -180m jump.
I stopped after this since it would take quite some time driving the rover up the hill over and over.

---------------------------------------------------------------------------------------------------------------------------

+- 60 tons

10° -2x No noticable bump.
       -3x Front wheels jump 2m.

15° -1x No noticable bump.
       -4x 3m jump.

20° -1x Front wheels jump 2m.
       -4x 10m jump.

25° -1x 100m jump.

---------------------------------------------------------------------------------------------------------------------------

I know this data doesn't prove anything. It's just meant to help you prevent your rover/wheeled outpost  jump in the air upon quickloading. Also I don't have any knowledge of game mechanics or anything more than basic physics so I probably can't interpret this data to its full extent. All I can do is give some advice.

Quick-saving/-loading above a 15° inclination is ill advised. (The jump height seems to grow exponentially after 15°) 
Time warping tends to have the same effect as quickloading but to a much lesser degree (Less than half the height in my experience).

Installing some small engines at your center of mass allows for a soft landing in case of tremors.
Save your game before landing on the celestial body of choice and/or before climbing hills.

Lower weight might lead to higher jumps. (But there's little evidence to back this and let's be honest. You're not gonna make your vessel twice as heavy just so it jumps less high in case of tremors. Also due to gravity you'll still crash in the surface with about the same speed as a lightweight I guess.)

TL;DR ONLY USE QUICKSAVE AND TIMEWARP WHEN LOWER THAN 5°.

No mods were installed during this test. Rover was parked without SAS or RCS, only the brakes were active. Effects of drilling during tremors were not tested.

 

Edited by Zieke Matroos
Image was unnessecarily big, switched to text

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Perhaps I am a bit late to stumbling upon this issue, but it seems there was a desire for a workaround until we get an official update. I had success in removing the jump all together when I did my time warps at the Tracking Station and then returned to my ship when I was ready. This resulted in the typical small "ker-bounce" as someone else dubbed but it didn't send my ship off the Mun's surface.

Hope this helps someone!

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@whale_2 appears to have crafted a good workaround for this jumping craft problem:

Just with cursory tests, it appears to work as intended, by slightly raising landed craft above the ground and letting it drop back down on physics load. Matt's Blunderbird 6 no longer jumps off the ground north of the runway.

I haven't yet tested all use cases, such as approaching a landed craft. Though I was able to approach a craft landed on the launch pad from a craft at the back of the runway and have it not explode. Said launch pad craft was on the 'space age toothpicks' landing gear.

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Confinming this. A craft with medium landing gear jumps on un-warp or when I come close to it in another vessel. Please write that to the report. This happens on any terrain, the runway or other planets.

The other craft with large landing gear stands down there where I hyperedit my crafts, and nothing has happened to it ever.

 

I don't know if it's related, but medium landing gear, when it's being retracted under load, also bounces the host craft.

Edited by Kulebron

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Definitely installing this tonight! Thank you! I can affirm that this was seen with stock 1.3.1. And it appeared to get much worse about the time 1.3.1 showed up but it's hard to remember. I didn't even install MechJeb until about 6 weeks ago. Turns out it's pretty handy.

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Landing gears like LY-35 and LY-60 is kicked into the air by the ground after time-warp.

It's 1.4.2, no serious mods added.

You can also use the stock plane "Stearwing A300" to reproduce this issue.

 

 

Edited by HeleleMama
Add more info.

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