2 Questions...

1) To scrap facilities you go to the Cargo tab for the planet and select 'Jettison Cargo' - the facilities are towards the bottom of the list according to other players

2) They are a researchable technology, you research Weapon Mounts and then can choose one for a ship that meets the size criteria. Weapons that can utilize the mount will display a letter on their picture that corresponds to the mount (L for large, H for huge, M for massive) - weapons that are on mounts do 200% the damage of non-mounted weapons.

-Currently subjecting multiple galaxies to the doom of conquer or blackholes

You can Use the Scrap Cargo Order, in the Cargo Order submenu, to scrap your facilities...

I don't think the previous posters really answered your question on mounts.

When you are designing a vehicle for which you have researched mounts, the list of eligible mounts will appear in the "mounts" window on the design screen, along with "none". While a given mount is selected on that window, the size, cost, and stats of eligible weapons in the components-to-add list will be changed to show their stats with that mount applied, and weapons added will be added using the mounts. Note that most mounts only apply to direct-fire weapons, and that mounts have a minimum vehicle size before they are allowed. So for example a small satellite will never be able to use weapon mounts because it will never be big enough to qualify for large satellite mounts.

The smallest weapon mount can be used on a Frigate, but the FG has to be at least 400 tons (iirc). Research up enough levels so your FG's are 400 tons, then you will see the Mount show up as an option on the left when you design the FG.

Sometimes I can't remember what the requirements are for a component so I'll save the game, then use the cheat:

~alltech~

Then you can see everything and right click the component you want (or mount) and it will tell you what its requirements are.

Then you can load the save game.

or you can just look at the data file in notepad or something and search for the component in question.

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an se5a is a ww1 fighter, it is also a car.