Kerbal Space Program

Edit:

I did more testing and it seems like the game raises the mass of low-mass parts to be at least 0.03t.
Empty dumpling tanks, empty oscar-B tanks, small grip pads, and small robotic parts apparently weigh 0.03t despite editor info.

Reported in this thread https://forum.kerbalspaceprogram.com/index.php?/topic/198851-111-part-mass-bug/&tab=comments#comment-3896452
where Stamp 20 points out the new line in Physics.cfg:

partRBMassMin = 0.03 // Minimum mass that a parts RigidBody can have - If this is too small then PhysX will not behave when it is dropped as a vessel, this is the default if minimumRBMass is not defined in the part cfg.

This observation inspires the obvious edit to 'Physics.cfg'
partRBMassMin = 0.005
which solves the problem for me. (I tried a Module-Manager patch but it did not take effect on KSP startup.) The adjusted minimum mass was 5kg, to match the minimum mass of all parts that have their mass attached to their body (as opposed to the smallest parts, flagged PhysicsSignificance=1, for which KSP adds their mass to the parent part).

The obvious potential side-effect, based on the comment in physics.cfg, would be if parts with mass in the range 5kg to 30kg start behaving badly when dropped on the ground during EVA construction.

However, some mods have lighter parts that can be independent rigid bodies, specifically the GP-004 grip pad from Breaking Ground used in some examples posted above. So for games including these parts, a lower minimum

  partRBMassMin = 0.002

New bug-report #26939 might have the same cause, but shows a different symptom in that the trajectory plotter sees a different center-of-mass than the physics engine.

[email protected] wrote:

However, some mods have lighter parts that can be independent rigid bodies, specifically the GP-004 grip pad from Breaking Ground used in some examples posted above. So for games including these parts, a lower minimum
[...]

My mod add 0.625 rocket parts to the game, so all my parts have a really small mass. In 1.11 with this mass added to all small parts, my mods is just broken, Rocket can't reach space anymore with a huge amount of False DeltaV showed. A lot of work broken with this update. Could be great to think about modders when you update things like that, Playing with KSP physics is never a good idea. I hope this could have a fix, i suggest the lower min mass possible to avoid any more problem, even if i think adding "virtual" mass to a parts wich is not defined to have this mass is not a good idea.