Stock in-flight assembly causes acceleration?

[MalneyKerman]

On the ground, stock engineer assembly works fine (I built a little beacon with the Stamp-O-Tron on the Mun with no problem).  In orbit, I can attach parts just fine.  But when I enter construction mode, do my work, and leave construction mode, I notice that my orbital parameters have changed.  This is aggravated when I have my engineer try to return to the ship, causing premature deorbits.  In addition, the engineer can't move much relative to the ship.

Why does this happen?  Are there workarounds or solutions?  (KAS/KIS doesn't have this problem, but it doesn't allow adding struts in-flight.)

[18Watt]

I haven’t seen this.  However, I believe recently there was a bug where Kerbals on ladders could cause vessels to accelerate.  I thought it had been fixed though.

• What version of KSP are you using?
• Which OS do you use?  (Windows, Linux, etc..)
• What mods are in use?  (Please list all of them)
• How much acceleration are you seeing?
• What body were you orbiting, and how high?
• Are you only noticing this while on ladders?

[MalneyKerman]

10 hours ago, 18Watt said:

I haven’t seen this.  However, I believe recently there was a bug where Kerbals on ladders could cause vessels to accelerate.  I thought it had been fixed though.

• What version of KSP are you using?
• Which OS do you use?  (Windows, Linux, etc..)
• What mods are in use?  (Please list all of them)
• How much acceleration are you seeing?
• What body were you orbiting, and how high?
• Are you only noticing this while on ladders?

I am using the latest version of KSP.  Linux.  I first noticed this problem on my main save with an immense number of mods, but it also occurs with no mods at all except DPAI and KJR.  I couldn't give a figure in m/s², but I saw that my Kerbin orbit went from 71km circular to 71 by 41.  My engineer was not on a ladder.

ETA: I noticed a similar problem with building a rover on the Mun.  Once my engineer leaves construction mode and boards it and tries to accelerate, it won't move.  The only additional mod I have installed is Kerbal Planetary Base Systems.

Edited February 19, 2022 by MalneyKerman
New information, corrigendum re mods.

[DeadJohn]

On 2/18/2022 at 4:27 PM, MalneyKerman said:

KJR

I think that's your problem. Neither fork of KJR (-Next or -Continued) works well in 1.12.x. Turn on advanced tweakables and use autostruts as a workaround.

My experience is that KJR triggers massive acceleration during construction mode. It can change your orbit and sometimes causes parts of the vessel to impact against one another and explode. I also had some cases where doing an EVA and re-boarding would cause a capsule to get 0 m/s velocity, plummeting from low orbit towards the surface. I haven't seen any of these problems since uninstalling KJR.

P.S. This thread is in the "unmodded install" subforum. It should probably be moved to "modded".