In the Second World War, the Germans developed a crude aircraft detection system that was based on infra-red radiation. The German system was called Kielgerat. Most often used to detect the exhaust from an engine, it could work out the direction of any heat source. Researchers at the Royal Aircraft Establishment in Farnborough, Hampshire, seized a Kielgerat system at the end of the war and increased its sensitivity and paired it with a 'lock-follow' system so it could home in on a target. The combined system was fitted to 'Firestreak', Britain's first infra-red guided misile, in 1953, and this method of infra-red homing has been used widely on guided misiles ever since. The head top featured here is from a heat-seeking misile called 'Red Top'.
© Science Museum / Science & Society Picture Library