Bug #27286

Physics changes after reverting to launch

Added by meltingSnowdrift 13 days ago. Updated 9 days ago.

Target version:
Start date:
% Done:


Breaking Ground
English (US)
Mod Related:
Arrow u r green
Arrow d r red


KSP version information
KSP 1.11.1 on Windows with breaking ground expansion, 64-bit, not Steam

Steps to reproduce
Launch the attached craft file at the runway from the spaceplane hangar with a kerbal in the command seat.
Activate the abort action group.
Wait until the parachute opens, which should occur 5 seconds after activating the action group.
Revert to launch.
Activate the abort action group again.

Expected behaviour
What happens upon activating the abort action group after launching from the spaceplane hangar should be identical to what happens upon doing so after reverting to launch.

Observed behaviour
See this video:

After reverting to launch, it appears to me that there occur changes to the physics of the game. Repeatedly reverting to launch does not further affect this behaviour and will repeatedly produce the altered behaviour. Reverting to the spaceplane hangar and launching again will produce the original behaviour, which can again be turned into the altered behaviour by reverting to launch.

bug demonstrator.craft (32 KB) bug demonstrator.craft Use this craft file to reproduce the bug. meltingSnowdrift, 02/16/2021 06:38 AM
Player.log (801 KB) Player.log This is the closest thing I could find to the "output_log.txt" file described in the instructions. meltingSnowdrift, 02/16/2021 06:43 AM
DxDiag.txt (103 KB) DxDiag.txt meltingSnowdrift, 02/16/2021 06:45 AM


#1 Updated by [email protected] 13 days ago

I do think it doesn't change physics but it might be related KSP forgetting absolute rotation of vessel, or if reverting to back to launch vessel isn't physically locked anymore when its at stability enchancers. It feels when you have fresh vessel it is more sturdy standing than it is when coming back to it later. It feels too that if you have vessel at launching pad it is more sturdy than vessel with same conditions at runway. So there might be some in-game parameter which stands for pre-launch condition, which it forgets when you revert back to launch.

#2 Updated by meltingSnowdrift 12 days ago

I am not convinced about that interpretation. Here is another video I made earlier demonstrating that something similar occurs in a way that is less likely to involve launch clamps:
I originally did not include that video because the procedure to reproduce was not as perfectly repeatable as the one I eventually made. I am including it now because it may help in distinguishing between potential causes of the problem.

#3 Updated by [email protected] 9 days ago

There is good odds that it's KAS bug too. Can you check KAS values before launch, and after revert? KAS have some bugs, related to it forget some commands and sometimes even mixing commands with other vessel nearby, it can be possible there is timing bug too.

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