Engineers of Victory: The Problem Solvers Who Turned the Tide in the Second World War by Paul Kennedy Page B

one had defied all British and American efforts for basic physical and technical reasons: there seemed to be no device that could hold the power necessary to generate the microwave pulses needed to locate objects much smaller than, say, a squadron of Junkers bombers coming across the English Channel, yet still made small enough to be put on a small escort vessel or in the nose of a long-range aircraft. There had been early air-to-surface-vessel (ASV) sets in Allied aircraft, but by 1942 the German Metox detectors provided the U-boats with early warning of them. Another breakthrough was needed, and by late spring of 1943 that problem had been solved with the steady introduction of 10-centimeter (later 9.1-centimeter) radar into Allied reconnaissance aircraft and even humble
Flower
-class corvettes; equipped with this facility, they could spot a U-boat’s conning tower miles away, day or night. In calm waters, the radar set could even pick up a periscope. From the Allies’ viewpoint, the additional beauty of it was that none of the German systems could detect centimetric radar working against them. 35
    Where did this centimetric radar come from? In many accounts of the war, it simply “pops up”; Liddell Hart is no worse than many others in noting, “But radar, on the new 10cm wavelength that the U-boats could not intercept, was certainly a very important factor.” 36 Hitherto, all scientists’ efforts to create miniaturized radar with sufficient power had failed, and Doenitz’s advisors believed it was impossible, which is why German warships were limited to a primitive gunnery-direction radar, not a proper detection system. The breakthrough came in spring 1940 at Birmingham University, in the labs of Mark Oliphant (himself a student of the great physicist Ernest Rutherford), when the junior scientists John Randall and Harry Boot, working in a modest wooden building, finally put together the cavity magnetron.
    This saucer-sized object possessed an amazing capacity to detect small metal objects, such as a U-boat’s conning tower, and it needed a much smaller antenna for such detection. Most important of all, the device’s case did not crack or melt because of the extreme energy exuded. Later in the year important tests took place at the TelecommunicationsResearch Establishment on the Dorset coast. In midsummer the radar picked up an echo from a man cycling in the distance along the cliff, and in November it tracked the conning tower of a Royal Navy submarine steaming along the shore. Ironically, Oliphant’s team had found their first clue in papers published sixty years earlier by the great German physicist and engineer Adolf Herz, who had set out the original theory for a metal casement sturdy enough to hold a machine sending out very large energy pulses. Randall had studied radio physics in Germany during the 1930s and had read Herz’s articles during that time. Back in Birmingham, he and another young scholar simply picked up the raw parts from a scrap metal dealer and assembled the device.
    Almost inevitably, development of this novel gadget ran into a few problems: low budgets, inadequate research facilities, and an understandable concentration of most of Britain’s scientific efforts at finding better ways of detecting German air attacks on the home islands. But in September 1940 (at the height of the Battle of Britain, and well before the United States formally entered the war) the Tizard Mission arrived in the United States to discuss scientific cooperation. This mission brought with it a prototype cavity magnetron, among many other devices, and handed it to the astonished Americans, who quickly recognized that this far surpassed all their own approaches to the miniature-radar problem. Production and test improvements went into full gear, both at Bell Labs and at the newly created Radiation Laboratory (Rad Lab) at the Massachusetts Institute of Technology. Even so, there were all sorts of delays—where