One hundred years ago, as the international conflict that became known as World War I began, most Europeans were predicting a quick victory. Within a few months, it became clear their optimism was unrealistic. As the fighting spread and grew more deadly, the role of engineering and invention took on new urgency. Eventually, the Great War became known in certain circles as an “inventor’s war.” To be sure, many of the inventions people now associate with World War I—submarines, torpedoes, fighter and bomber aircraft—had actually been conceived earlier. However, the pressures of war pushed their advancement. Here are four such technologies that still influence our world today.
SONAR: Making the Sea Safe for Democracy
In the years leading up to the war, navies that had submarines used them mainly for coastal defense. Germany changed that by developing its U-boats into long-range offensive weapons. That shift in military strategy compelled the Allies to 1) also begin using submarines offensively and 2) develop countermeasures to protect cross-Atlantic shipping.
The work of Reginald Fessenden proved crucial. After an iceberg sank the RMS Titanic in 1912, the Canadian radio pioneer began conducting underwater acoustic experiments in search of a way to protect ships from submerged obstacles. This led him to invent an electro-mechanical oscillator, a device carried aboard a ship that would transmit sound through the water at a specified frequency and then listen for reflections from any objects in the vicinity. He developed the technology first as a means of communicating with (friendly) submarines and later as a warning device that could be attached to navigation buoys to alert approaching ships of shoals and other hazards. In October 1914, the British Navy purchased Fessenden oscillator sets for underwater signaling, and in November 1915 decided to equip all of its submarines with them.
French physicist Paul Langevin designed an electronic version of Fessenden’s device that was much better at detecting moving objects. It included a quartz transmitter and receiver, which greatly improved the range and clarity of the signal. In February of 1918, he achieved a transmission range of 8 kilometers and clear echoes from a submarine.
The Fesseden oscillators continued to be used as late as World War II for detecting stationary objects such as mines. And Fessenden’s and Langevin’s inventions laid the foundations for what would become SONAR (Sound Navigation and Ranging). For more on Fessenden’s oscillator, see the IEEE Global History Network’s “Inventors’ Responses to the Sinking of the RMS Titanic.”]
The Superheterodyne Receiver: Better Tuning for Radio
Radio technology existed before the war, but two wartime inventors greatly improved them. In 1917 and 1918, respectively, a French officer named Lucien Lévy and an American officer named Edwin H. Armstrong independently came up with what would become known as the superheterodyne receiver—a way to tune radios and to allow them to pick up distant signals. The receiver basically superimposed one radio wave on another and greatly amplified and filtered the resulting intermediate frequency, which was then demodulated to generate an audio signal, which was in turn amplified for output to loudspeakers or earphones.
Initially, Lévy sought a way to increase the secrecy of radio transmissions. He had been working at the Eiffel Tower—which the French military began using for radio experiments when the war broke out. Lévy had the idea that a supersonic wave could be superimposed upon a radio frequency carrier wave, which would itself be modulated by an acoustic wave. He refined that idea, producing the supersonic wave in the receiver and then heterodyning the received signal against a local oscillator. He applied for a French patent on 4 August 1917.
Armstrong was made a captain in the U.S. Army Signal Corps shortly before he was sent to France in 1917 to work on Allied radio communications. By then, he was already famous in the radio world for his regenerative feedback circuit (a device that greatly amplified a signal), for which he received the first Medal of Honor from the Institute of Radio Engineers. While in Paris in early 1918, Armstrong witnessed a German bombing raid. He thought that the accuracy of the antiaircraft guns could be improved if there were a way of detecting the extremely short electrical wavelengths emitted by the ignition systems of the aircraft engines. That led him to invent his superheterodyne receiver, for which he filed a French patent application on 30 December 1918.
After the war, Armstrong’s and Lévy’s competing claims on the superheterodyne receiver did not prevent it from being used widely, helping transform the radio into a hugely popular consumer product. [For more on Lévy, Armstrong, and the controversy surrounding their inventions, see Alan Douglas’s “Who Invented the Superheterodyne?”]
Air-to-Ground Communication: Radiotelephony Takes to the Skies
As early as 1910, experimenters demonstrated wireless transmissions between aircraft and the ground. These trials all involved the pilot tapping out Morse code on a transmitter held in his lap. There were a few problems, however. Engine noise tended to drown out any received messages. And pilots were usually far too busy to be operating a code key.
Clearly, voice radio would be necessary for wireless communication to become practical in the air. But voice transmissions required higher frequencies than did Morse code, and the radios and their power sources were too big and heavy to fit into the aircraft of the time.
Engineers on both sides of the conflict succeeded in making those improvements. In 1916 the French successfully tested air-to-ground voice communication during the battle of Verdun; one year later, they demonstrated air-to-air voice communication at Villacoublay. Transmitters became standard aboard German aircraft in 1916 and, by the end of that year, so were receivers. On 17 May 1918 a U.S. airplane squadron was successfully commanded by voice from the air for the first time. [For more on early airborne radio, see George Larson’s “Moments and Milestones: Can You Hear Me Now?”]
Analog Fire-Control Calculators: Precursors to Digital Computing
As the range of large caliber guns increased, aiming them became more difficult. The World War I naval engagements of Coronel (off the coast of Chile) and Dogger Bank and Jutland (both in the North Sea) saw gunnery ranges from 13,000 to 15,000 meters. To hit another ship from those distances required precise calculations of the target ship’s range, course, and speed, as well as the wind's speed and direction, which in turn were used to determine the gun’s elevation and direction, the wind’s effect on the shell in flight, and any corrections for the motion of the ship doing the firing.
In 1912, the British Royal Navy pioneered a system in which all the guns on a ship were directed from a single position (usually the highest part of the ship). The fire-control officer and rangetakers used a T-shaped optical rangefinder containing prisms to ascertain the distance, bearing, and change-of-bearing to the target by means of triangulation. The fire-control officer then communicated—usually via telephone, but with voice tubes as backup—this information to the sailors in the control center deep in the ship. They in turn moved cranks and levers to input the information into large mechanical calculators (some the size of three or four refrigerators), which used this constantly changing data to plot firing solutions for the guns. The guns would then be fired in salvoes, with a slightly different trajectory from each gun, thereby increasing the chance of hitting the target.
During the course of the war, the navies of the Allies and the Entente made significant improvements to these fire-control calculators, and there is still scholarly debate as to which navy had the most advanced system. The British Navy’s Dreyer Tables were probably the best documented of these devices, while the German battlecruiser SMS Derfflinger was widely regarded for the accuracy of its gunnery at sea. Derfflinger was scuttled at Scapa Flow in 1919, and what is known about its fire-control system emerged mostly through Allied intelligence interviews with its gunnery officers.
The range of land artillery also increased significantly during World War I. By the end of the war, for instance, the Germans were bombarding Paris with a massive gun mounted on a railroad car. Known as the Paris Gun or the Kaiser Wilhelm Geschütz, it had a range of 130 kilometers. Although it was not very accurate, it could hit something the size of a city, and so its effect was primarily psychological.
The analog mechanical calculators used to target artillery guns led directly to electronic computers. In fact, one of the most famous of the early electronic computers, ENIAC, did essentially the same tasks during World War II as the analog fire-control calculators of World War I.
About the author: Robert Colburn is the Research Coordinator at the IEEE History Center.