Читать книгу Engineering Hitler's Downfall - Gwilym Roberts - Страница 56

While the RAF concentrated most of its research and development efforts on Bomber Command, to the detriment of aerial defence and Fighter Command (and, to an even greater extent, maritime warfare and Coastal Command), brains were already at work on the kind of defensive shield Baldwin had been unable to imagine.

It was thought possible, for example, that the noise made by aircraft might be used to detect their direction and range, and experimental acoustic mirrors were erected around the coast, some of which are still standing. Measuring up to 70 metres wide and 5 metres high, they were made of concrete to spherical, not parabolic, concave shapes and had a microphone near the focal points which could be moved so as to determine the aircraft’s direction. While partially successful, they became less effective with increasing aircraft speed and were abandoned when electronic systems were developed.

Following discussions between Sir Henry Tizard, the chairman of the Aeronautical Research Committee, and Robert Watson-Watt, the superintendent of the radio research station then based at Slough, Berkshire, Watson-Watt investigated the feasibility of developing and using damaging radiation – commonly known as ‘death rays’ – as a defence. He concluded that they would not damage the crew or equipment inside a metal aircraft, which would in effect act as a Faraday cage (a mesh of conductive material around a person or object which shields the contents from external electromagnetic fields).

However, his assistant, Arnold (Skip) Wilkins, suggested that it might be possible to detect an aircraft by bouncing radio waves off it. Following experiments using radio waves generated by the BBC shortwave transmitter at Daventry, in February 1935 they were able to detect an RAF bomber at a distance of 12 km. This was the first time that this had been achieved in Britain and the event is now commemorated by a plaque at Stowe Nine Churches, Northamptonshire.

Acoustic mirrors, Denge, Kent. © Paul Russon

Commemorative Plaque, Stowe Nine Churches, Northamptonshire. Peter Mallows