This month in 1955: the steam catapult

Regular readers of The Engineer will have noticed that we’re following the project to build the Royal Navy’s two new aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales, with great interest. Our guest blog from the Aircraft Carrier Alliance’s chief engineer, David Downs, keeps us up to date with the latest news from the Rosyth shipyard, where Queen Elizabeth has now become the Navy’s largest ever ship.

Back in 1955, our predecessors were also following aircraft carrier developments closely, with first test of an important new technology, the steam catapult. Using steam from the ship’s boilers to act directly on the catapult itself, these had been tested aboard the carrier HMS Perseus since 1950, and had just started to be installed aboard the British and American carrier fleet.

Prior to the use of steam catapults, aircraft had been propelled into the air using a hydro-pneumatic system which used steel wire ropes to drag a small trolley along the flight deck, with the aircraft towed along behind. This was fine for the relatively small and lightweight aircraft carried by naval vessels in World War II, but with the advent of jet engines, carrier-borne aircraft became heavier and needed to be launched at greater speed. For a while, naval architects just increased the power of the hydrodynamic system, but the heavier aircraft — along with the heavier cables and pulleys — meant that eventually the catapults were growing too large to be installed even on the biggest ships.