Читать книгу Engineering Hitler's Downfall - Gwilym Roberts - Страница 47

As Britain’s fate hung in the balance, a crucial engineering challenge was presented to Allied scientists: how to counter the menace of the mines sown on the bed of Britain’s shallow coastal waters by German ships and submarines or parachuted there by the Luftwaffe. So serious was the problem that the Port of London, then Britain’s busiest port, was nearly closed.

These mines were detonated by the magnetic field of a ship passing over them, and it is notable that before those 800 ‘little ships’ sailed from Kent ports to rescue the troops stranded in Dunkirk, they had to be ‘wiped’ by teams from HMS Vernon to make them magnetically neutral.

Sinkings off UK’s east coast September 1939–December 1940. Chatham Historic Dockyard

HMS Belfast. Now moored near Tower Bridge. IWM

The importance of the ensuing engineering feat was later expressed by one of its heroes, Commander Sir Charles Goodeve: ‘Although in the technical achievement the human effort was not in the same class as the radar or U-boat battle, it was the first technical battle in which we won a decisive victory over the enemy; but more important still, it was one which brought science fully into the war in the very early days.’

The earliest casualty of the magnetic mines, the SS City of Paris, was damaged on 16 September while among naval casualties before the end of the year were the battleship HMS Nelson, which was put out of service for nearly a year; the newly commissioned cruiser HMS Belfast, which broke its back and took two years to be repaired; the destroyer HMS Blanche, which was sunk; Captain Lord Louis Mountbatten’s ship, the destroyer HMS Kelly, which had her stern blown off; and the minelayer HMS Adventure, which suffered serious damage.

Caught unawares, and ignorant of how they operated, the Navy’s experts had to wait for mines to be dropped until they could be recovered and dismantled before they exploded. Two such mines were dropped by the Luftwaffe on the mud flats at Shoeburyness, Essex, in November 1939, and defused and dismantled by Lt Cdrs John Ouvry and Roger Lewis RN, and by CPOs Charles Baldwin and Archie Vearncombe of HMS Vernon. The pairs were awarded DSOs and DSMs respectively for their bravery.

Thereafter, it was generally possible for the mines that could be found to be recovered and made safe, although sometimes things went wrong, with tragic results for those attempting to defuse them. The Germans also sometimes used delayed-action mines or booby-trapped the fuse mechanisms, adding to the hazards faced by the naval defusing teams. Among naval officers engaged in such work was Sub-Lieutenant (Sp) Peter Danckwerts RNVR, who was awarded the George Cross for his bravery. Detailed accounts of the mechanisms involved (which he described as ‘a miracle of ingenuity’) are contained in Danckwerts’ biography.

Exploded view of magnetic mine fuse mechanism. Peter Varey

Solutions also had to be found to protect ships from the mines that had been successfully dropped on the sea bed. A variety of counter-measures were investigated as a matter of urgency, but the two systems developed by Lieutenant Commander Charles Goodeve FRS RNVR proved most effective and were widely adopted. The first was to develop a system of detonating the mines which did not damage the vessels involved, and the second was to demagnetise ships.

The former aim was achieved by the Double L Sweep, which involved two small wooden-hulled minesweepers towing a long loop-shaped buoyant electric cable between and behind them, through which strong electric DC currents were passed; the magnetic fields then induced in the sea were sufficient to detonate the mines.