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.
CHAPTER 6 LUSITANIA
NOTICE!
TRAVELLERS intending to embark on the Atlantic voyage are reminded that a state of war exists between Germany and her allies and Great Britain and her allies; that the zone of war includes the waters adjacent to the British Isles; that, in accordance with formal notice given by the Imperial German Government, vessels flying the flag of Great Britain, or of any of her allies, are liable to destruction in those waters and that travellers [sic] sailing in the war zone on ships of Great Britain or her allies do so at their own risk. IMPERIAL GERMAN EMBASSY Washington, D.C., April 22, 1915.
—New York Times, May 1, 1915.1
This warning was published in many newspapers, along with a list of the Cunard Line Lusitania’s European destinations, prior to her departure at 10 a.m. on Saturday, May 1, 1915. The German embassy warning was unambiguous—passengers would be traveling “at their own risk.”
On April 30, one day prior to Lusitania leaving New York, Captain Lieutenant Walther Schwieger, in command of U-20, left Wilhelmshaven on Germany’s North Sea coast. Bound for the open seas west of Ireland, his orders were to participate in an aggressive, predatory submarine campaign against merchant vessels. A week later, nearly two thousand passengers and crew of the 787 foot long, 44,060 ton passenger ship would sit in the cross hairs of U-20’s periscope. According to the entry in Schwieger’s log, at 3:10 p.m. on May 7, 1915, “Torpedo shot at distance of 700 meters, going 3 meters below the surface. Hits steering centre behind bridge. Unusually great detonation with large cloud of smoke and debris shot above the funnels. In addition to torpedo, a second explosion must have taken place.”2 It would take only eighteen minutes for Lusitania to plunge to the bottom, just eleven miles from her Liverpool destination, bringing nearly 1200 passengers and crew with her. There were only 761 survivors.3
U-boat flotilla at their base at Keil. U-20, the submarine that sank Lusitania, is in the front row, second