Читать книгу The Listeners - Roy R. Manstan - Страница 14

CHAPTER 5 A GAME OF HIDE AND SEEK

[V]essels were formed into special hydrophone flotillas, whose duties consisted of listening in long lines for submarines and when a discovery was made attacking them in the most approved tactical formation, with the aid of depth charges … Nearly all U-boats were fitted with a number of hydrophones and therefore were as well able to receive timely warning of an approaching surface ship as the surface ship was of the presence of the submarine … [allowing] a game of hide and seek to be played between a hunting vessel and a hunted submarine.

—Charles Domville-Fife, Submarine Warfare of Today, 1920.¹

In his 1920 book Submarine Warfare of To-Day, Charles Domville-Fife related his experiences as commander of a British hydrophone flotilla engaged in antisubmarine operations. German submarines had enjoyed the ability to disappear beneath the sea after an attack on an unarmed merchant ship, becoming nearly undetectable once they submerged. It would be more than a year before the Royal Navy would have a vessel designed specifically for submarine hunting—fast, maneuverable, and capable of operating far off shore. Success as an antisubmarine asset, however, was dependent on the hydrophone and the listeners on board.

During the first two years of the war, as Commander Ryan, who had been promoted to Captain, continued to develop hydrophones for shore-based listening posts, the only vessels available in any significant numbers for submarine patrols around the British Isles were commercial trawlers and what were referred to as “drifters” because of the drift nets used for fishing. Once commissioned, the vessels’ crews became members of the Royal Navy Reserves (RNR) or the Royal Navy Volunteer Reserves (RNVR). The trawlers and drifters, according to Domville-Fife, each numbering well over one thousand, were initially employed in minesweeping and coastal patrols. The ships carried armament in the event they encountered a surfaced U-boat, but were often out-gunned by the submarine. “[Trawler] losses were heavy, both in ships and men, amounting to about 30 per cent,” as indicated by Domville-Fife, while drifter “losses amounted to about 20 per cent.”²

Domville-Fife quoted an article in an American magazine, Rudder, written by Henry R. Sutphin, vice president at Electric Boat Company and manager of Electric Launch Company (Elco), one of the businesses purchased by Electric Boat in 1899.

It was February, 1915, that we had our initial negotiations with the British Naval authorities. A well-known English ship builder and ordnance expert [Sir Trevor Dawson] was in this country, presumably on secret business for the Admiralty, and I met him one afternoon at his hotel…. I suggested the use of a number of small, speedy gasoline boats for use in attacking and destroying submarines. My idea was to have a mosquito fleet big enough to thoroughly patrol the coastal waters of Great Britain, each of them carrying a 13-lb. rapid-fire gun.³

Sutphin was asked how many of the 80-foot vessels could be delivered within a year. “I told him I could guarantee fifty.” A short time later, Sutphin was informed that the British Government was interested, and on the 9th of April, a contract for fifty of these “chasers” was signed. A month later, however, the submarine U-20 torpedoed and sank the Cu-nard Liner Lusitania. According to Domville-Fife, Sutphin’s British contact asked him if a larger order could be managed; Sutphin’s response: “I told him that I could guarantee to build a boat a day for so long as the Admiralty might care to name.” The Admiralty’s reply was soon forthcoming, and a contract for an additional five hundred “Chasers” was signed on the 9th of July.⁴

The Admiralty designated these as Motor Launch (ML) class vessels, with a desired speed of nineteen knots. The speed was simple arithmetic. A submerged U-boat may have been capable of as much as ten knots, although most were limited to about six to eight knots. A submarine on the surface, however, could run at nearly seventeen knots, eluding most of the patrol craft available to the Admiralty.⁵ Pursuit by a destroyer, however, was a different matter. With speeds over thirty knots, a U-boat risked ramming if spotted on the surface, or if, having fired a torpedo, the destroyer could follow the track of the torpedo back to the submarine.

The USS Aylwin (DD-47) represents the type of destroyer used by American and British forces in the war zone. (NHHC NH 77908) Before the development of effective listening devices, destroyers would follow the track of a torpedo

in an attempt to ram the U-boat. (Sims, 1919-1920)

With 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 a facility for submarine research, and where he concentrated his efforts on the advantages of using quartz crystals as the transmitting source.¹³

By April 1917, Langevin was able to test a powerful quartz transmitter at his Toulon laboratory, operating at a “supersonic” frequency of 150 kHz (150,000 cycles per second). During this time, he also experimented with the size of the transmitter surface, the width and intensity of the sound beam, and the frequency. It wasn’t until February 1918, however, that Langevin would successfully test his transmitter at sea, receiving an echo from a submerged submarine for the first time.¹⁴

The work Langevin and other French researchers had completed throughout 1915 and during 1916 aroused the interest of British scientists who, representing the British Admiralty’s Board of Invention and Research, established a cooperative relationship with the French Ministry of Inventions. There were indications of a bit of envy by the BIR scientists of the excellent oversight of the research by the ministry, and the importance to the war effort placed on the work of the French scientists.¹⁵ From its inception, the BIR, with its emphasis on science, was often at odds with the pragmatic, make-it-happen-now approach of the military.

When America entered the war on April 6, 1917, an ally with a strong scientific tradition took a leading role in the antisubmarine effort. Exchanges of scientific missions began immediately, and the potential importance of Langevin’s transmitter was recognized as a critical topic. The Ames mission from America arrived in France in April, followed by a European mission to America, organized by Painlevé and arriving in Washington at the end of May (chapter 12). The French delegates included two physicists, Charles Fabry and Henri Abraham, who had received commissions as Majors in order that the civilian scientists might better interact with the French military. Several conferences were held in June, where Langevin’s work was discussed, although he was not able to participate in the mission. The conferences resulted in a great deal of enthusiasm among the American scientists, followed by the participants taking immediate action. From Admiral Griffin (1922):

[T]he supersonic work which had been begun in France by professor Langevin was presented in full by Majs. Fabry and Abraham. The New York group, under the direction of Dr. M. I. Pupin, of Columbia University, selected at this time supersonic work at its major activity and continued work on this problem at New York, Key West, and New London, under the direction of the [Special Board on Antisubmarine Devices], during the continuation of the war. The San Pedro group, under Mr. Harris J. Ryan, also started work about this time on supersonic and kindred lines of research.¹⁶

Scientists and engineers from universities and industry continued their research on “supersonics” throughout the remaining eighteen months of the war, often bringing their ideas and devices to the Naval Experimental Station in New London. The early experimental work on echolocation is discussed in the epilogue, as this technology would prove to be essential to antisubmarine warfare in the future. The French had planned to install Langevin’s latest device on submarine hunting vessels assigned to the Offensive Division of Torpedo-Listeners and on larger vessels beginning in 1919.¹⁷ Armistice intervened.

At the beginning of this section, it was noted that supersonic submarine detection systems using “a beam of sound waves of very high frequency” were not ready for use before Armistice. The British and French antisubmarine efforts had continued throughout the first two-and-a-half years of the war without American help. During those years, U-boats continued their unrelenting pursuit of commercial shipping, which, after their declaration of a war zone around the British Isles in February 1915, resulted in the loss of untold numbers of civilians, including Americans who risked the Atlantic crossing.