The Great War saw the first large scale introduction of submarines able to attack naval and merchant shipping. In the first sixteen months of World War One Allied losses exceeded 2.5 million tons of merchantmen. To combat this threat a depth charge was developed by the Navy although credit is shared across several individuals and the Thornycroft Company. Herbert Taylor, an engineer from South London, was invited to join HMS Vernon as engineering officer in 1915 after inventing a detonation pistol for underwater use to be used in a depth charge designed by a naval officer Alban Gwynne.
The role of Thornycroft and Company was to work on a means of propelling the charges from their ships. John I. Thornycroft took this task seriously and according to the post-war Royal Commission on Rewards for Invention he had a prototype ready in 10 days, and within three weeks a device was on a motor torpedo boat. By the end of the War 2,760 throwers had been delivered.
The depth charge itself was an explosive device with a hydrostatic fuse capable of being set so that the bomb would explode at a given depth in the water thereby destroying any enemy submarines present. The charge initially of TNT but later Amatol, weighed 140 kilos and as the fuses were susceptible to changes in air pressure great care had to be exercised in handling and deploying them.
Early Depth charges were dropped from a platform rigged on the stern of a warship, however the explosion of the charge could cause damage to the ship and this method was also limited in its accuracy. The Thornycroft launcher resulted in a patent which would propel a depth charge 37 metres away from the firing ship without a premature detonation of the charge.
Information collected for this topic page was through the ARHC funded project ‘Business, government and the workplace: John I. Thornycroft & Company Limited, and the Great War', and research conducted by Dr. Roy Edwards, University of Southampton and Keith Harcourt