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Bug #28603

LT-05 landing legs bounce in violation of Newton's 3nd Law

Added by jjansen almost 3 years ago. Updated almost 3 years ago.

Status:
New
Severity:
Low
Assignee:
-
Category:
Parts
Target version:
-
Start date:
01/21/2022
% Done:

0%

Version:
1.12.3
Platform:
Windows
Expansion:
Breaking Ground, Core Game, Making History
Language:
English (US)
Mod Related:
No
Votes:
Arrow u r green
Arrow d r red

Description

ISSUE: deploying the LT-05 Micro Landing Strut on any surface causes a massive launch with a lightweight craft and standard strut values. Bounces after are HIGHER than the previous bounce's maximum height, breaking the law of the conservation of energy.

This post led me to do some investigation: https://www.reddit.com/r/KerbalSpaceProgram/comments/s92hah/are_micro_landing_struts_bugged_for_anyone_else/

I initially thought it was the fault of an interaction with the L3 Launch Pad as seen in the above link's video, but trying it on the runway revealed the same problem.

I took it to the next level however, showing that each bounce is higher than the last maximum height, going as high as 310m into the sky before it will crater.

screenshot1481.png (2.76 MB) screenshot1481.png 2 - gear deployment caused dV of 30+m/s jjansen, 01/21/2022 05:34 AM
screenshot1482.png (2.49 MB) screenshot1482.png 3 - 9 seconds, 100m apex jjansen, 01/21/2022 05:34 AM
screenshot1483.png (2.41 MB) screenshot1483.png 4 - 16 sec, 171m apex jjansen, 01/21/2022 05:34 AM
screenshot1484.png (2.64 MB) screenshot1484.png 5 - 27 sec, 310m apex jjansen, 01/21/2022 05:34 AM
screenshot1485.png (2.69 MB) screenshot1485.png 6 - 34 sec, impact jjansen, 01/21/2022 05:34 AM
screenshot1480.png (2.72 MB) screenshot1480.png 1 - Predeployment jjansen, 01/21/2022 05:34 AM
Screen Recording 2022-01-20 at 23.35.40-Zoomish Quality.mp4 (5.33 MB) Screen Recording 2022-01-20 at 23.35.40-Zoomish Quality.mp4 Example 1 mkwarman, 01/21/2022 06:05 AM
Screen Recording 2022-01-21 at 00.16.44-Zoomish Quality.mp4 (3.55 MB) Screen Recording 2022-01-21 at 00.16.44-Zoomish Quality.mp4 Example 2 mkwarman, 01/21/2022 06:05 AM
Screen Recording 2022-01-21 at 00.24.17-Zoomish Quality.mp4 (1.67 MB) Screen Recording 2022-01-21 at 00.24.17-Zoomish Quality.mp4 After reducing spring and damper mkwarman, 01/21/2022 06:05 AM
1_11_2 QuickSave LT-05.sfs (65.7 KB) 1_11_2 QuickSave LT-05.sfs Anth12, 01/21/2022 11:38 AM
screenshot58.png (2.18 MB) screenshot58.png Anth12, 01/21/2022 11:51 AM
1.12.3 More Mass No Problem.png (2.23 MB) 1.12.3 More Mass No Problem.png Anth12, 01/21/2022 12:11 PM
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History

#1 Updated by jjansen almost 3 years ago

The original reddit thread operates on Mac OS, found this on a clean install (I replicated it on my modded Win10 install) and revered to different versions to check. He said it looks like the change happened between 1.11.2 and 1.12.1 https://www.reddit.com/r/KerbalSpaceProgram/comments/s92hah/are_micro_landing_struts_bugged_for_anyone_else/htk5v6t/

#2 Updated by mkwarman almost 3 years ago

I'm the OP of the post jjansen linked. Enabling advanced tweakables and turning down the spring and damper on the micro landing struts helped a bit, but there definitely seems to be a regression in behavior since 1.11.2. I'll attach a couple screen recordings to this note. I had to compress them a bit to get them to upload, but higher quality versions are available here:

#3 Updated by jjansen almost 3 years ago

mkwarman wrote:

I'm the OP of the post jjansen linked.

can confirm

#4 Updated by Anth12 almost 3 years ago

(Removed 2 previous posts)

Happens from 1.12.0

If I do it in 1.11.2 and max the dampeners and then max the springs I can get a similar result to 1.12

#5 Updated by Anth12 almost 3 years ago

58859

KSP 1.11.2 + MH + BG
KSP 1.12.0 + MH + BG
KSP 1.12.3 + MH + BG

1_11_2 QuickSave LT-05.sfs is from 1.11.2 for testing.

The screenshot is of 1.12.3 with the test craft acting like its 1.11.2 but the spring/damper are a lot lower than they should be to stop the bouncing.

mkwarman: Agreed. Enabling advanced tweakables and turning down the springs/dampers is how to counter the problem

Lowering the spring/damper seems to counter the problem entirely.

#6 Updated by Anth12 almost 3 years ago

58860

Great...and then a reload of the craft with those settings makes it go wonky in a different way, upping the dampers stopped that

And a craft with more mass does get different results correct?

1.12.3 More Mass No Problem.png This has more mass with less of an issue. the only thing that shows its still having a similar issue is because the legs are extended to nearly their max

#7 Updated by Anth12 almost 3 years ago

This for some reason feels a lot like the springs are bottoming out when the settings are too high. The springs when set to 0 used to cause the legs or wheels to push out to their maximum if memory serves.

The only thing I can suggest is to do what you are already doing. Manually set the spring/dampers

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