motor launches carrying hydrophones, it was hoped that a U-boat could be detected before it was in a position to attack a merchant ship. The hunting group, now in pursuit and working in concert with a destroyer, could locate the submarine’s position and drop its limited supply of depth charges. The destroyer, in wireless contact with the hunting group, would then steam at full speed to the location and launch a barrage of depth charges. That was the hope. “The tactical methods of anti-submarine attack” expected of the motor launches, as Domville-Fife had described, “proved impracticable for the more heavily armed but slow-moving trawlers and drifters.”6
British motor launch assembly in Canada. (Nutting, 1920)
The contract for the 550 motor launches was completed on November 3, 1916. An order for an additional thirty was placed in July, 1917, all of which were launched the following year. Because the United States was considered a neutral country, orders were placed via the Canadian company Vickers, although Electric Boat Company, through Elco at its Bayonne, New Jersey, shipyard was the primary builder of the component parts. The final motor launch assembly was accomplished at shipyards in Quebec.7 The vessel was an American design, that of naval architect Irwin Chase. The engines for the twin screw, nineteen-knot vessel were produced by the Standard Motor Construction Company. This same engine would be used on the U.S. Navy’s submarine chasers, which began production when America entered the war and soon after the British motor launch contract had been filled.
Domville-Fife described the motor launch as “an avenger upon the seas … to whom the world appealed to save the lives of their seamen … it fought by day and by night, in winter gale and snow, and in summer heat and fog, in torrid zone and regions of perpetual ice to free the seas of the traitorous monster who had, in the twentieth century, hoisted the black flag of piracy and murder.” A bit dramatic, but for Domville-Fife, the motor launch, his “avenger upon the seas,” and the U-boat were the adversaries in a “guerrilla war at sea.”8
British motor launch ML-369. (www.naval-history.net)
This may have been an overstatement, though the MLs, as they were referred to, certainly played a major role in British antisubmarine efforts. Until improvements were made in the listening devices, detection and destruction of submarines was a difficult mission; the heroic actions by these small warships would continue to be handicapped. According to Captain C. V. Usborne, RN, in spite of having obtained upgraded devices during the summer of 1917, there were still significant problems. His comments were summarized in The German Submarine War, 1914-1918 (1931):
[In] June 1917 I obtained twelve sets of directional hydrophones and thirty to forty sets of ‘plate’ or ‘shark-fin’ hydrophones for use in the Mediterranean, the latter pattern then being ‘the latest thing’ in acoustic detection. Various craft were fitted out with these instruments, but the hydrophones were very crude, and the submarine-detection by sound-listening could only be carried on very slowly.9
Until reliable, directional listening devices were developed and deployed, hydrophone flotilla tactics with the early British hydrophones remained inefficient. Domville-Fife described the process when a German submarine was heard:
It was the call to action. The microphone was hauled to the surface and the chase began, a halt being made every half-mile or so for a further period of listening on the hydrophone. If the sound was louder the commander of the pursuing vessel knew that he was on the right track, and if the sound came up from the sea more indistinct the course was changed and a run of a mile made in the opposite direction, when the vessel was again stopped and the instrument dropped overboard.10
Regardless of any tactical inefficiencies associated with the listening devices carried by British motor launches and American subchasers, hunting with hydrophones was a constant concern of U-boat captains. If a submarine was detected, a destroyer with its supply of depth charges would often be called to the area. When faced with the presence of hydrophone flotillas and other hunting groups, U-boats, also equipped with hydrophones, might quietly head for the bottom and listen to the sounds of the surface vessels. Ernst Hashagen, commanding officer of U-62, recalled his experiences while operating just outside the English Channel near the Cornish coast. They had been aware of the distinct sounds of a destroyer’s propeller and, in keeping with the game of hide and seek, had settled onto the seabed at a depth of 150 feet. As they prepared to surface after several hours, this from the control room:
… the order [is passed] through all voice pipes: “Silence in the boat: listen for propeller noises: surfacing in ten minutes time.” The stern compartment repeats “Attention! Report if propeller noises are heard.” The coxswain puts on an under-water telephone connected to a diaphragm in the outer hull. But all is quiet.11
Listening with what Hashagen called their “bigger ear,” which could detect the destroyer’s propellers far in the distance, allowed U-62 to surface and continue on toward the shipping lanes and potential targets while charging their batteries. This tactic, however, could spell disaster for an unwary U-boat captain. Operating in groups of three or more, the hunters might leave one vessel adrift in the area, while the U-boat would hear the rest motoring away. Surfacing could place the submarine in its most vulnerable position, with its hull and conning tower exposed to inevitable shelling by the hunter before the U-boat’s gun crew could return fire. In spite of the risks, bottoming the submarine became a common practice when depths allowed. There was nothing for the listeners patrolling on the surface to hear.
Ernst Hashagen served on U-22 in 1915, took command of UB-21 in May, 1916, and later U-62 in December, surviving the war in that submarine. His exploits certainly allow him the credibility to describe the effect listening devices had on U-boat operations, particularly during the last two years of the war. In 1915, listening technology had yet to significantly deter the Imperial German Navy’s undersea raiders, and the U-boat was then very capable of winning that game of hide and seek.
FROM FRANCE, A SUPERSONIC IDEA, BUT TOO LATE
Another device capable of detecting a lurking submarine half a mile or more away by the use of a beam of sound waves of very high frequency was perfected too late to be of use …12
What Robert Millikan described in 1920 became the basis of “active” echo-location for submarine detection. That “beam of sound waves” was based on the piezoelectric properties of quartz crystals, where the crystal expands and contracts when subjected to an alternating electrical current. Throughout the war, the listeners on board submarine hunters relied on “passive” detection by hydrophones of sounds generated by a submarine’s machinery and propellers when underway. Now, it appeared that there was a possibility of transmitting sounds from the hunting vessel, those sounds striking a target—the U-boat—and bouncing back in the form of an echo to a receiving hydrophone, which the listener would hear. Knowing the direction of that beam of sound waves and the time it took for the echo to return gave a direct reading of the bearing and distance to the submarine. Had this been available during the war, a U-boat could no longer hide on the bottom.
Soon after the war began, France established a Ministry of Inventions, led by mathematician Paul Painlevé (later serving as prime minister from September 12 to November 13, 1917). Painlevé became interested in one of the many suggestions made to the ministry by French citizens, and in February, 1915, passed one of particular interest to Paul Langevin, physics professor at the Collége de France in Paris. Early experimentation with echo detection in the Seine having been promising, Langevin’s operation shifted in 1916 to the naval base at Toulon, where the French had established
