Schleuderschiffe - catapult ships - were used by Germany since the 1920s. Their most famous use before the war was their usage as floating bases in the South Atlantic to enable flying boats to cross the Atlantic for mail delivery. Stationed at the at the African and South American coast, they were used to refuel and resupply the small flying boats like the Dornier Wal on their way across the ocean.
Equipped with a catapult, they were able to launch the flying boats instead of doing a manual takeoff from the water. This allowed the flying boats to carry more fuel and allowed a higher range to fly.
Based on the experience with the civilian catapult ships, additional ships were build during the war for military purposes only. Together with thier civilian counterparts, they were used to maintain and launch reconaissance flying boats in areas outside of fixed installations.
and its sister ship Bussad
were mainly used in Denmark and Norway during the war, which both survived. Their crane was able to lift aircraft up to 20t. Their catapult was able to launch aircraft of the same weight, enableing the ship to carry Dornier Do18, Dornier Do24 or Blohm &Voß BV138 aircraft.