During combat S and M size ships have a chance to bail leaving the ship abandoned and able to be claimed by other faction or the player. To claim bailed ships the player can either claim it from their Spacesuit or order a Marine to do it. To personally claim an abandoned ship, <player> must spacewalk to it, and then locate and scan a signal leak. After the ship becomes player property, the player can dock with the ship and fly it away.
Alternatively select the abandoned ship and then right click it to order a Marine on board the playership to go and claim the craft using a Boarding Pod (<playership> crew must have at least 1 marine assigned to use this option); the Marine will become the Pilot of the new ship once ownership has been transferred. If you intend to keep the ship, finding at least a one-star pilot is recommended to replace that random marine.. or you could set them to 'explore' for several hours to level up their piloting skill..
Marines will cause damage to onboard systems while boarding, so expect losses of (eg) weps, shields etc on <target> once claimed via marine. Personal <player> boarding via 'hacking' the signal leak may not cause (as much) damage..
Large and XL ships need to be boarded to be captured. Boarding requires sufficient Marine crew across the player-owned ships participating in the action. Boarding involves Scanning the target to gain intel, planning (using the intel), choosing a Behviour for your boarding ship(s) and initiating the 3-stage operation.
Either before or during the Op (via Behaviour), the target needs to be nullified (taking out the engines, turrets and shields; reducing crew levels through hull damage). To initiate boarding, select the desired player-owned ship(s) and then right click the target and order Marines to Board the target.
Within the Boarding Menu (see below), plan:
Approach (getting Boarding Pods safely to the target)
Infiltration (breaching the hull)
Assault (Defeating the crew)
Stages 1 options instruct their boarding ship(s) how weakly-defended the target should be before launching Boarding Pods. Stages 2 options instruct their Marines how strong the target hull should be before breaching (weaken hulls reduce risk to marines but increase risk of destroying the target). Finally during Stage 3, your surviving Marines will attempt to defeat the target's crew.
Try to keep the subsystems destroyed, and work on reducing hull levels but not to the extent that the boarding marines will destroy the ship. Once the target hull is sufficiency low to reduce boarding resistance below the boarding strength of the players forces (20 or more is good) the ship is as good as captured. If successful, a Marine can be assigned as the captain for the ship or the player can move to the ship personally.
Administrative Centre modules, when completed at a player station, grant ownership of an unowned sector on a first come first served basis, revealing all ships and stations in the sector and imposing the illegal wares list of the owning faction.
If the Administrative Centre module is destroyed, sector ownership will change over to the next faction with an Administrative Centre. Warring NPC factions are constantly playing a turf war to replace the Defence Platforms of their enemy with one of their own. Once the player has acquired Blueprints for an Administrative Centre, they too can conquer entire sectors if they are willing to defend it.
If a faction is about to challenge you for the ownership then there will be a warning "(Contested)" behind the name of your system indicating a construction of a station with an admin module has commenced.