Читать книгу Blood, Tears and Folly: An Objective Look at World War II - Len Deighton - Страница 29

During the 1930s scientists in Germany, France, the USA and Britain, working independently and in secret, discovered that a beam of very short pulses, sent and reflected from a target back to a cathode ray tube, would define that object’s bearing and range. It was not advanced technology, and it certainly wasn’t a British invention. Even the Russian armed forces were equipped with radar by the time war began.

The German battleship Graf Spee had excellent gun-laying radar and the Scharnhorst and Gneisenau both used radar to evade HMS Naiad in January 1941. Naiad’s Type 279 radar was outranged by the German radar, so that after one brief visual sighting by the British (who never made radar contact) the German ships were able to keep clear of their pursuers. In the Norwegian campaign the same two German ships had surprised HMS Renown by using gun-laying radar to hit her while remaining concealed in a snow squall.

The Royal Navy began to equip its ships with Type 79 radar in 1939, although at the outbreak of war only HMS Rodney and HMS Sheffield had been fitted with it. These sets were intended for the location of enemy aircraft, and were given to the big ships and to anti-aircraft cruisers such as HMS Curlew, HMS Carlisle and HMS Caracoa. In May 1940 two hundred Type 284 (50-centimetre) gun-laying radar sets were ordered. New urgency was given to radar development when, in the Mediterranean in 1941, ships without it were found to be at a grave tactical disadvantage. The US navy had been fitting radar to its ships since 1940, and in the August of that year, long before the United States went to war, the USN and RN began to share their technology.

At the start of hostilities, German radar was more accurate and sophisticated than that of any other nation. The first radar success of the war was on 18 December 1939 when a formation of 22 RAF Vickers Wellington bombers was detected 70 miles off the German coast. Only ten of the bombers returned.

While British designers concentrated on longer-range sets, the Germans wanted accuracy and, where possible, mobility. In the summer of 1940 a German mobile unit on the Cherbourg peninsula fixed the position of an RN destroyer near the British coast and it was sunk by a Luftwaffe attack.

Radar – or Radio Direction Finding as the British called it at that time – was cumbersome, and the use of delicate glass vacuum tubes, known as valves, made it fragile. Such apparatus was regarded as a land-based, or shipborne, anti-aircraft weapon that could also be used against ships. It was probably the British who first tried another idea. A team under Dr Edward Bowen put an early EMI television receiver into an old Handley Page Heyford bomber and was encouraged by getting a flickered reception from a transmitter. From this they went on to design a small high-frequency set to go inside an Avro Anson aircraft. By 3 September 1937 it could detect big ships at about five miles.

The vital factor in the development of British radar was a willingness to improvise. Priority was given to radar – and other scientific ideas – when radar was credited with having saved Britain from defeat in the Battle of Britain. The Nazi creed gave emphasis to rural traditions and old ‘Germanic’ customs; and the political leaders of the Third Reich were apt to be antagonistic to modern science, sometimes defining it as Jewish. German scientists were not automatically exempted from military service, and civilian scientists assigned to work with the armed forces did not find the welcome that their British counterparts were given. Britain invented the technique of ‘operational research’, which meant scientists (cheerfully nicknamed ‘boffins’)¹⁴ advising the armed forces on the most effective way to use existing weapons rather than having to devise new ones.

Operational research boffins demonstrated that you could double the size of a convoy without doubling the length of its perimeter; in fact the perimeter of an 80-ship convoy was only one seventh longer than a convoy of 40 ships. Thus big convoys meant more effective use of escort vessels. Moreover average losses decreased from 2.6 per cent to 1.7 per cent when convoys comprised more than 45 ships. This was partly due to the fact that a wolf pack’s activities were limited by the availability of torpedoes, reloading time, stress and fatigue, whatever the size of the convoy.

Operational research also helped decide at what depth a depth charge should be set to explode. The scientists suggested that, given enough time, a U-boat crash-diving usually turned away to escape. Such targets should be abandoned as a lost cause. Depth charges dropped from aircraft should be set to explode near the surface, ensuring the more certain kill of those U-boats attacked early enough. Such ideas brought an immediate and dramatic benefit to British anti-submarine tactics.

When war began, Coastal Command had 12 Lockheed Hudson aircraft fitted with ASV (Air to Surface Vessel) Mark I radar. Better sets – fitted in the larger Armstrong Whitley bombers and Sunderland flying boats – followed. At its best, airborne radar could pick up a U-boat at 25 miles, but these valuable aircraft, with their ineffective anti-submarine bombs, seldom sank U-boats.

The boffins were asked why out of 77 U-boat sightings from aircraft in August and September 1941 only 13 were originated from airborne radar contact. The hastily built equipment was poorly serviced, they said, and operating it was a job assigned to anyone with time to spare. Better training gave aircrews faith in their equipment, and towards the end of 1941 airborne radar became more and more effective. Swordfish biplanes of 812 Squadron Fleet Air Arm showed what it could do by patrolling systematically by day and night against U-boats trying to get through the narrow Strait of Gibraltar in to the Mediterranean. One U-boat was sunk and five damaged so badly that they had to return to base.¹⁵

In addition, the Royal Navy’s big ships were being fitted with its own more sophisticated gun-laying as well as air-warning radar, yet the range of British radar sets was still less than that of an alert lookout on a clear day. The urgent problem was to develop something that could be fitted into an escort vessel, such as a corvette, and detect the conning tower of a surfaced U-boat at night.

Dr S. E. A. Landale was one of the team that set up a short-wave centimetric radar on the cliffs at Swanage and traced a submarine seven miles away. He found practical difficulties when fitting his radar into a ship: ‘Corvettes are very wet and in rough weather the discomforts, inconvenience and inflow of water whenever the office door was opened had to be experienced to be believed.’¹⁶ Antenna systems had to be protected against the weather. More problems arose from the rolling and pitching and the effects of engine vibration and of gunfire. Even so, by the end of 1941 the Type 271 radar had been designed, one hundred were built and fifty ships were equipped with it. This was the first operational magnetron-powered centimetric radar in the world. In use it was a revelation: it could even locate the top of a periscope. No longer could a surfaced U-boat sail at night with impunity.