Black Knight re-entry head, c 1960.
© Science Museum / Science & Society Picture Library
The Black Knight ballistic vehicle was used to test prototype re-entry heads for the proposed Blue Streak strategic misile. This head is made of Durestos, a composite of asbestos held in a phenolic resin. As it re-entered the atmosphere the head's surface would have grown hot and burned or 'ablated' away, so preserving a lower internal temperature. A section of the head has been removed to reveal instrumentation that measured the head's temperature, its acceleration and the accuracy of signals received from the ground. The Blue Streak project was cancelled in 1960.