A prototype of a World War II airplane bomber catapult has been excavated by a team from the Museum of London Archaeology (MOLA) in Harwell, Oxfordshire. The site is slated for a new development of the Harwell Science and Innovation Campus, and the existence of the catapult was known from historical records, but as a failed experiment shut down in 1941, it was not documented in detail, so MOLA archaeologists were enlisted to reveal its secrets. This is the first time the catapult has seen the light and been studied in detail since early in the war.

Design work began on the catapult in 1935, the year Germany rearmed in defiance of the Treaty of Versailles. After three years of planning, catapult construction began in 1938, the year Germany invaded Czechoslovakia. It was completed in 1940, the year of the Battle of Britain when 3,000 men of the Royal Air Force kept control of British skies under the brutal onslaught of Hitler’s Luftwaffe.

The advantages to catapulting a bomber plane into the air included saving the fuel expended in takeoff and requiring a much shorter runway than the conventional variety. Even after this project was shut down, the idea of the airplane catapult survived and was deployed with success to launch aircraft from ships.

The circular central pit, 10 feet deep and 100 feet in diameter, contained most of the catapult’s machinery and engines. The catapult was powered by 12 Rolls-Royce Kestrel aero engines which took up all that space in the pit, hence its depth and breadth. Above the mechanics a turntable was mounted into a slot at the top of the pit’s wall. Two concrete runway channels extended 270 feet north and south from the pit.

The way it was supposed to work was that airplanes would drive onto the turntable which would turn towards one of two runway arms extending north and south. On the south arm, the plane would be hooked onto an underground pneumatic ram would be driven down the channel by a blast of compressed air from the 12 Rolls Royce engines. The plane was supported by a trolley on wheels. The ram would drag the plane to top speed at ground level and launch it into the air. The north runway arm has a different design, perhaps for experimental purposes, which archaeologists are still studying to determine how it was meant to be used.

In the end, the Mark III catapult was ever used. Only the prototype was built, and it failed in big ways. Its engines kept wearing out, and most bumblingly, the design did not actually fit the bomber planes that already existed. It never successfully launched a single plane. In 1941, it was filled in and a conventional airstrip built on top.

The construction work at the site will continue and the catapult remains have been dismantled, alas. Before it was removed, the catapult facility was thoroughly photographed and scanned and a 3D digital replica created for future research.