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Bug #2031

Fuel feeds to radially mounted engines when attached to a part other than a fuel tank.

Added by jasool over 10 years ago. Updated over 7 years ago.

Status:
Closed
Severity:
Normal
Assignee:
-
Category:
Gameplay
Target version:
-
Start date:
01/12/2014
% Done:

100%

Version:
0.23
Platform:
Any
Expansion:
Language:
English (US)
Mod Related:
No
Votes:
Arrow u r green
Arrow d r red

Description

When a part that is not a fuel tank is radially mounted with an engine underneath it, the engine will use fuel from the center fuel tank.

This issue only manifests when the part that is radially mounted is not a fuel tank. I have tested with a fuselage and a Science Jr.

See attached screenshots and craft files for further explanation.

screenshot3.png (1.29 MB) screenshot3.png Fuselages mounted radially. Radial tanks are out of fuel and the engines are running using fuel from the center tank. jasool, 01/12/2014 04:15 PM
screenshot5.png (1010 KB) screenshot5.png Issue does not happen if it is the fuel tanks that are mounted to the radial decouplers. jasool, 01/12/2014 04:15 PM
screenshot8.png (1.65 MB) screenshot8.png Here you can see that you don't even need a fuel tank for the radial engines. They are running on fuel from the center tank. jasool, 01/12/2014 04:15 PM
Fuel feed bug test II.craft (15.2 KB) Fuel feed bug test II.craft Test craft with fuel lines. jasool, 01/12/2014 04:15 PM
Fuel feed bug test V.craft (12.8 KB) Fuel feed bug test V.craft Test craft with no radial fuel tanks (the radial engines still run using fuel from the center tank). jasool, 01/12/2014 04:15 PM
Fuel FeedBug Control Case.craft (23.7 KB) Fuel FeedBug Control Case.craft Problem NOT present -- fuel tank radially mounted directly. newnard, 10/23/2014 11:45 AM
Fuel FeedBug Example Case.craft (32.5 KB) Fuel FeedBug Example Case.craft Problem present -- fuel tank below radially mounted science jr. newnard, 10/23/2014 11:45 AM
2014-11-24_00002.jpg (249 KB) 2014-11-24_00002.jpg Center tank unused newnard, 11/24/2014 05:34 PM
2014-11-24_00003.jpg (228 KB) 2014-11-24_00003.jpg Center tank used newnard, 11/24/2014 05:34 PM
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History

#1 Updated by newnard over 9 years ago

Just wanted to confirm that this bug persists in stock 0.25.0.642 (tested with Science Jr). Craft files attached.

#2 Updated by Padishar over 9 years ago

This is not really a bug. It is a well understood and well documented (here: http://forum.kerbalspaceprogram.com/threads/64362-Fuel-Flow-Rules-%280-24-2%29) consequence of how the "fuel flow" mechanism works.

#3 Updated by newnard over 9 years ago

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Padishar, thank you very much for the link. I have learned much today.

I still think this is a bug. It turns out to be a bug that behaves in accordance with the rules you linked; that just means that the rules you linked are an accurate description of the current behavior of the software, not that the current behavior is correct.

I'm attaching two screen shots. The craft are as simple as I could make them and identical with the exception of one part (the Science Jr., which is present in one but not the other).

It is my rather strong opinion that the fuel flow SHOULD be identical in the two cases; but it is not. (Using the most excellent post you linked, the fuel search terminates in step 5 in one case and step 7 (nested, from step 4) in the other) Why should you gain access to double the fuel, in this case, by adding a science part? Or why do you lose access to the center tank if you remove the science part?

If the devs agree with me that the fuel feed behavior shouldn't change so drastically just because you insert or remove one non-fuel-related part, fine. If they don't, then my fallback position is that the VAB should provide SOME means for the player to visualize or determine how fuel will flow through the craft so they can learn the (rather unintuitive) rules.

My first impulse after reading the linked rules is that rule 4 should maybe be modified so that rule 7 is not invoked as a child of it; or put another way, rule 7 shouldn't fire in the process of checking rule 4.

But clearly this is a complicated system and it won't be a trivial change, and without extensive testing I can't say what unintended consequences my suggestion would have.

#4 Updated by Squelch over 9 years ago

There are plans underway for an editor overhaul, and some specifics regarding fuel lines may mean this behaviour is affected as a consequence. Once 0.90 is released, this issue may need revision.

Ref HarvesteR's Devnote

#5 Updated by TriggerAu almost 8 years ago

  • Status changed from New to Needs Clarification

#6 Updated by TriggerAu over 7 years ago

  • Status changed from Needs Clarification to Closed
  • % Done changed from 0 to 100

Closing this report out for now. If you find it is still occuring in the latest version of KSP please open a new report (and this one can be linked to it.) For best results, the wiki contains really useful info for when creating a report http://bugs.kerbalspaceprogram.com/projects/ksp/wiki.

You can also ask questions about the bug cleanup in the forum here: http://forum.kerbalspaceprogram.com/index.php?/topic/143980-time-to-clean-up-the-bug-tracker/ and tag @TriggerAu to get my attention

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