Part Category: Propulsion?

[Superfluous J]

While working on a contract pack, I separated out my parts by the categories they are in, in the part files. The categories seem to match up perfectly with their tabs in the VAB, so much that I assumed that that's what they're for.

Then I noticed that a handful of parts are in the category "Propulsion", and now I'm confused.

Note that there is already a category for "Engines" and another for "FuelTanks" so this is not one of those. Nor is it for jet engines or RCS or anything like that. It contains - among others - the parts:

• The Rhino
• Mk2 Bicoupler
• NCS Adapter
• S3-14400 Fuel Tank

It seems on a first glance that this category is for all the SLS parts. Okay, fine. Weird, but fine. But how does the game know to put them in their correct places? The Rhino isn't in the fuel tanks tab and the 14400 tank isn't in engines.

What is the propulsion category for, and why is it inconsistent with the rest of the categories? And is there an actual way to - by looking at the part cfgs - determine what VAB tab a given part will be in?

[nightingale]

This should be from before engines and tanks were split.  I think it was left for backwards compatibility with logic to put stuff in the right category (only guessing at the criteria, but presence of ModuleEngines or ability to hold fuel are two likely candidates).

[Superfluous J]

Oh wow I totally forgot that engines and fuel tanks used to be in the same category.