landing gear bounce upon docking or undocking
The attached ground-craft has two parts, that sit level before and after docking, but upon decoupling, docking or later undocking, the LT-2 landing gear bounces.
Half-load or more of fuel overstresses and destroys the LT-2 gear.
Likely duplicate of 18380.
#1 Updated by MOARdV almost 3 years ago
I see a similar issue when entering a spaceplane that's parked on Kerbin (not spawning a new craft, but returning to it from the Tracking Station or directly from the Space Center) - the landing gear (small aircraft landing gear) bounce slightly, and only taking off and landing seems to reset them. In my case, it is not reproducing 100% of the time, maybe closer to 30% of the time.
#2 Updated by cpcallen almost 3 years ago
I have a similar set-up, but with a more extreme result: massive explosions.
If I undock the two halves of the craft in the attached .craft file and then re-dock them, all landing struts are destroyed and wheels damaged.
#3 Updated by [email protected] almost 3 years ago
- Status changed from New to Confirmed
- % Done changed from 0 to 10
The example at the top post will also show massive explosions, if you use full fuel tanks.
Possibly, though, this bug is being worked on. Something similar is referenced at the weekly announcement.
#4 Updated by Tomator over 2 years ago
The issue might be more general: it seems that stresses in construction are reset on docking when the model is probably rebuilt (pipes or winch connection using KAS plugin do the same) which causes sometimes "launching" entire base into the sky (on Minmus) if it stands on struts. It's less dangerous when struts were removed and the base lays just on tanks. Similarly, the likes to jump when it enters the physics range. When stress state isn't saved, also reloading while atmospheric flight causes quite violent stress resolving - while I didn't notice plane destruction, the smooth flight is disturbed in such case (so I never do quick save during final approach)
#5 Updated by [email protected] over 2 years ago
The bounce is much less in version 1.4.5, now the craft from the initial report survives even with full tanks.
It was true even in version 1.3.1 that the stresses and flexing of craft were not saved in the save-file, so that upon physics loading the wings on air-craft initially appeared un-flexed, and suffered an initial sometimes dangerous bounce as they took the weight of the aircraft. However, the initial example (attached now in 1.3.1-format) shows no bounce on the landing legs, and only a small bouncy roll on the wheels, upon undocking in version 1.3.1.
The 12-m/s speed of the initial fall on the example craft in version 1.4.5 is more than gravity could do in one or two time-steps. So even with the limitation of stress-forgetting save-files, significant further reduction in these bounces seems possible.
#6 Updated by [email protected] over 2 years ago
Now I see that version 1.3.1 does save the compressed state of landing legs and gear, while version 1.4.5 does not.
1.3.1 quicksave.sfs records ModuleWheelSuspension : suspensionPos = (0, 0, 0.44) where the final number gets larger with less weight, more extension.
1.4.5 quicksave.sfs records ModuleWheelSuspension : suspensionPos = (-1, -1, -1)
So I can imagine that upon docking the physics engine is told that the leg was fully compressed, then 0.02 seconds later is extended to whatever is needed to reach the ground, interprets that as something pulling the landing leg at some tens of m/s, and generated a damping force that pulls the craft rapidly down.