[Suicide Junkie]

Some additional stuff:

retrofitting units:
You can't retrofit units, just jettison and build new ones.
That is considered the price you pay for not having to pay maintenance on them each turn.

Minesweepers:
Multiple sweepers on a hull, and multiple sweeperships in a fleet all stack. Five minesweeper V components can clear the first 25 mines that you hit in each sector. The rest of the mines bLast your ships.

Capture ships:
The marine with red shield is actually the security station (boarding defense)
Multiple boarding parties can only help you overcome more defenders. It is an all-or nothing deal.
The best strategy is probably to use lots of small hulls like destroyers to carry the marines, and let your bigger ships smash the shields on the enemies independantly.

Facility upgrades:
You can upgrade the facilities on a single planet as Val said, but the only way to upgrade one facility at a time is to scrap and rebuild.

Star exploding:
The only way to stabilize a star that is about to detonate is to build a ringworld or sphereworld around it.
By the time you get the warning, it is probably too late to start a project that big.

Repair bays:
The total number of repair ability points is all that matters. All the points are applied to one ship, then the next.
So, one repair bay can fix eight minimally damaged ships at once, or ten can work on one massive wreck of a ship at once. Or anything in between.