The final, post war, carrier invention was the steam catapult. Aircraft had, up until this time, left the carrier’s flight deck by a number of different means, the most obvious being the free take off, which was still being employed by the Skyraider AEW1 in the 1950’s. Rocket assisted takeoffs (RATOG) was also used quite effectively by aircraft participating in Korean operations during 1950-1953.
Catapults had been around since the 1930’s (when they were fitted to the carriers Glorious and Courageous) however these early devices were powered either by compressed air or cordite. It was Commander C C Mitchell RNVR who first suggested taking steam from the ship’s main boiler to power the catapult. Trails on HMS Perseus during 1950-1952 showed an aircraft weighing 30,000lbs could be launched with a speed of over 90 knots, which was a considerable increase over the air hydraulic catapults then in service. The steam catapult also proved to be considerably more reliable. By the time the RN's last fixed wing carrier was retired in 1978 (HMS Ark Royal), the steam catapult was regularly launching aircraft weighing over 60,000lbs at 110+ knots.
It is only now that the Americans are looking to replace Steam Catapults, on their next generation carriers, with electromagnetic catapults.