Just like my nuke launcher ship idea, this would b amazing!! This also requires friendly fire to work.
All you would need is 2 tractor beams, a long and thin gap, and a slab of armor (or anything else). You place the tractor beams facing toward each other. You then need to have a long but thin entry (or exit point) for your ships to leave or enter. Make sure there is enough room on one side ( not the entry/exit point) to fit your door. After that, you need to hav a slab of armor in the center, just make sure it's small enough (or big enough) to fit through your door gap. After that, make sure (for closed doors) to keep the tractor beam farthest from your entry point on push. If you want to open it, simply turn off the push tractor beam.
Now yes, this does have flaws. If any part of it is destroyed, the door could jam, or could be flung into space. However, this could be good for:
Blocking superweapons from damage (if door is thick enough)
Allowing parts of a ship to "shift" ("Doorframe" would have to be modified)
Allowing fighters to leave without leaving massive gaping holes in your ship
And could be used with other designs, like my nuke launcher idea or @Sombreroman 's melee beam.
Now there is another kind of door out there that was just pointed out. The thruster door. This door is simpler and less bulky then mine. So I'm going to list th pros and cons of both doors.
PROS FOR BEAM DOOR
1. Can be expanded for cheap
2. If jammed, the door is cheaper to Replace
3. The door itself can be replaced with other pieces.
PROS FOR THRUSTER DOOR
1. Can be made small or thin
2. If jammed, door could/would be easier to fix.
3. Th door is can b made to go faster or slower.
CONS FOR BEAM DOOR
1. Is Bulky
2. Cannot be made into a double-door variant
3. Can be expensive
CONS FOR THRUSTER DOOR
1. Can be destroyed easier
2. Can't be enlarged without being pricey
3. Can be harder to build due to engine dead zones.