We’ve recorded an experimental World War Two catapult in incredible detail ahead of a Harwell Science and Innovation Campus development.

Named the Royal Aircraft Establishment (RAE) Mark III Catapult, this device was developed to literally catapult bomber planes into the air. There are several reasons why these kinds of catapults were being developed, including being able to launch planes using shorter runways and loaded with more fuel.

This excavation, done on behalf of Carter Jonas and Bidwells, will help us understand and shine a light on this extraordinary piece of history.

Photo of archaeologists excavating the metal rail in one of the catapult arms

How did the catapult work?

This prototype was built 1938-1940 at Harwell, Oxfordshire after three years of design work. The catapult was made up of a large rotating turntable which directed aircraft towards one of the two concrete track runways that were just 82 metres long. To launch, the aircraft would be attached to an underground pneumatic ram using a towing hook.

12 Rolls-Royce Kestrel aero engines, sitting underneath the turntable, compressed air to 2,000 psi to drive the ram. This high-pressured air was then forced into the pneumatic ram, which rapidly expanded to the length of the guided track - literally catapulting the large bomber planes into the sky.

Collage of reconstructions of the plane sitting on the trackway as it would have looked when built

This catapult was part of a series of innovations and experimentations that happened in the lead up to and during World War Two. Unfortunately, this was one idea that literally never took off. The prototype catapult had several problems, including engines wearing out and the design not fitting the bomber planes it was meant for.

Never actually launching an aircraft, the project was quickly abandoned. Once abandoned, the mechanism was taken out, the structure was filled in and by 1941 a normal runway was built across the end of the southern arm. However, it paved the way for other launching designs such as the CAM system used in the early part of World War Two to protect merchant ships.

What did we find?

As part of the recent works, we fully excavated the concrete remains of the catapult – which had been mostly buried since the 1940s. Although its existence was known about through historical records, this work meant the structure could be recorded in incredible detail for the first time.

Susan Porter, MOLA Project Officer, says: “This fascinating structure reminds us of the rapid experimentation and innovation of the interwar years and World War Two. Crucially, recording the location and appearance of every inch means that the catapult is preserved by record for future generations.”

Now, bringing together hundreds of photos and thousands of data points, we have faithfully recreated a 3D digital replica of the remains. This allows the public and future researchers to explore the Mark III Catapult from the comfort of their own home.

The excavations also uncovered finds from a later runway nearby, including large runway lights, roughly 1m square, and a previously unknown gun emplacement that originally defended the runway from attack.

Photo of three archaeologists inside the circular gun emplacement excavating it

What happens next?

The catapult has now been dismantled to allow construction works to continue. However, we are still carefully working through all the information we’ve captured and the finds we’ve excavated. Once this work is complete, everything will go into an archive providing a permanent and detailed record of this unusual piece of early World War Two history.