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[BUG: VAB] Launch displays incorrect delta-V when adding parts after adding a fuel line (has workaround)


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Not sure if this is considered a repost (please remove if it is). I saw a few other posts related to issues with the delta-V calculation generally, but I found a current workaround that may be helpful figuring out some of the particular delta-v issues.

KSP Version: v.1.1.0 (latest as of today)
Operating System and version: Windows 10 (Version 10.0.19044 Build 19044), also tested on Debian sid
CPU: Intel i7-6700 @ 3.40GHz
GPU: Nvidia GeForce RTX 3060 Ti (driver version 531.29)

Description of the bug: 

The launch panel seems to incorrectly calculate delta-V after a fuel line is added, once additional parts are brought into the mix.

For example, a Mun lander might be built with small boosters on the side with fuel lines to bring its delta-V to 3000 m/s. If you want to add landing gear, your delta-V instantly drops to 2000 m/s. A small drop is expected, but not that much. Surprisingly you can get the delta-V back just by rebuilding the fuel line. This short clip I recorded shows how you can get inconsistent readings for the same set of parts

I didn't see a way to embed webms here so, here's a direct link instead: https://drive.google.com/file/d/1wWtzLFNOE5H7kJz-58PTuRyS63Wl0WbI/view?usp=share_link.

Expected Behavior

Fuel Lines should not be discounted from delta-V in Trip planner if additional parts are added. The delta-V should stay close to 3000 m/s.

Observed Behavior

Displayed delta-V drops to its "pre-fuel line" value when modifications are added.

Steps to Replicate

1. Build any craft with fueled boosters that feed into a central fueled tank.

2. Make adjustments or additions to the craft to observe inconsistent readings of delta-V. 

Fixes / Workarounds: Rebuild the fuel line (note: this is pretty difficult to do if you have a smaller craft behind fairing)

Other Notes:

In the video posted, my craft starts from the "expected" delta-V after I applied the workaround.  I remove a landing leg and LOSE 900 m/s (removing weight should be a gain). I remove all parts and attempt to rebuild the craft I started with. Everything builds as expected until I add the landing gear. When I add a landing leg, I again LOSE 900 m/s. I can get this lost speed back simply by removing and adding the fuel line.

Edited by mezzo_forte
Did not understand that was a code tag, not embedded HTML
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