Construction ship

Construction Ship: Once mainly used to make refueling depots or other niche structures, such as refueling stations.

In the sector zero DLC they are seemingly only used for building in hexes where there are no planets or asteroid belts. The space station will only be built in the exact center of the hex, the ship must be moved into the hex first before the option to build it will show up. After the initial unfortified station is built (essentially a refueling station), a space station (like ones that guard planets) can be built, or a listening post that gives sensor info on nearby sectors. Once the fortified station is built, it can be upgraded with listening post sensors as well. The construction ship must remain for the build duration of these, and is not destroyed by building anymore.