Milestones:Sonar, 100th birthday of Paul Langevin Invention 1917-2017

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Invention of Sonar, 1915-1918


From 1915 to 1918, Paul Langevin demonstrated the feasibility of using piezoelectric quartz crystals to both transmit and receive pulses of ultrasound and thereby detect submerged submarines at ranges up to 1300 metres. The system, later called sonar, validated Constantin Chilowsky's proposal to use ultrasound for this purpose. The technology was used successfully during World War II, and led to other applications including depth sounding and medical echography.

Justification for inclusion of Prof. Paul Langevin’s name in the Milestone Plaque Citation:

The invention strongly relies on the careful design and the experimental skills of Paul Langevin who invested his time and energy in solving the problem. It is to be noted that it was not part of a regular Laboratory work but was only performed upon his own initiative. It is his privileged knowledge of electromagnetism, electricity, wave propagation and piezoelectricity that enabled this invention.

See for instance [2] : p 43-44

Chilowsky’s proposal:

Constantin Chilowsky had originally submitted a patent indicating the « possibility of producing the desired elastic high frequency waves by transforming the electric oscillations of high frequency commonly used in wireless telegraphy. » However Paul Langevin who was made aware of this application immediately realized that the use of magnetic fields was highly problematic. He writes [2]: « To effect this result, M. Chilowsky proposed to utilize the medium of magnetic attraction produced by the current, acting synchronously on all points of the internal face of a plate of soft iron, finely laminated, in contact with the water at its external face, and of a proper size in relation to the wave-length of the elastic vibrations in the water, so as to produce an emission almost entirely confined to a central cone of diffraction, in accordance with the phenomena of the distant diffraction of plane waves through an opening of the same shape as the plate employed. No method of receiving, however, was indicated. »

Paul Langevin will have to reconsider the device and will consider a vibrating capacitor in order to have the necessary power to provide sufficient sensitivity. In his presentation, partially transcripted below, at the Interallied Conference on the search for submarines by the ultrasonic method: History of research carried out in France (19 October1918), Paul Langevin writes : « When this proposition came before me, l was struck by the insurmountable difficulties involved in the magnetic field, and thought that the chances of success, although still small, would be increased by having recourse, in effecting the transformation to the electrostatic attraction between the armatures of a plain condenser, periodically charged by the high-frequency current. The internal armature of this condenser being insulated, and the other armature in contact with the water by its exterior face, the periodic attraction between them is transmitted to the water, giving rise to the emission of elastic waves of a frequency double of the electric frequency and with the maximum of radiation, obtained either by making the external armature sufficiently thin, or by giving it a thickness equal to half the wavelength of the longitudinal elastic vibrations in the metal used. » « I proposed, in March 1915, to the Navy Department that this research work be undertaken, and that it be initiated in my Laboratory at the School of Physics and Chemistry… When the development of the work justified it, the military authorities consented to place at my disposition as collaborators, the services of M. Marcel Tournier, Director of Practical Work at the School of Physics and Chemistry, and of M. Fernand Holweck of the Sorbonne; the former since September 1915, the latter since July 1917. I [Paul Langevin] applied with M. Chilowsky for a patent on the principle of the method, and on the apparatus actually constructed. »

This first patent was filed in May 1916. Procédés et appareils pour la production de signaux sous-marins dirigés et pour la localisation à distance d'obstacles sous-marins, Constantin Chilowsky et Paul Langevin. [P1]

The divergences between Langevin and Chilowsky:

In spring 1916, as a result of disagreements with Langevin, Chilowsky left the research, leaving the French physicist in full charge. (See [1])

In [3], one can find the following text: « Chilowsky’s proposal was forwarded by the under-secretary of state for inventions to Professor Paul Langevin, an early supporter of the theory of relativity and an expert on paramagnetism, diamagnetism, secondary X-rays and the behaviour of ions. Langevin concluded that Chilowsky’s basic idea had merit, but that his means to produce a suitable sound wave was unlikely to succeed. Langevin decided to begin research into developing a practical means to create an intense pulse of high-frequency sound. He asked Chilowsky to join him and a small team of scientists working at his laboratory at the School of Physics and Chemistry in Paris. By April 1916 results were so promising that the French Navy transferred their work to Toulon so that experiments could be undertaken at sea. At about this time, Chilowsky parted ways with Langevin and left to pursue other military research. Although it is reported that Chilowsky’s departure was not cordial, in the years ahead Langevin was careful to give the inventor equal credit for the discovery of sonar. Despite having taken no active part in the post-war legal proceedings, Langevin insisted Chilowsky be treated as an equal partner in the claim for compensation. »

The invention of the SONAR: Paul Langevin and the Quartz transmitter and receiver: If the use of ultrasound was the fundamental principle, the realization through the use of the piezoelectric effect was the real paradigm shift. It enabled both emission and detection.

« In spite of these encouraging results, it was still very difficult to use the apparatus. Beside the disruptive accidents already mentioned in the mica condensers, which l was trying at that time to avoid by substituting heterodyne lamps for the arcs used in the sending apparatus, the microphone gave very irregular results, and required delicate regulations in order to keep the sensibility of the carbon contacts approximately constant against the variations in outside pressure due to the movement of the sea. In order to avoid these difficulties, l thought (February 1917) of utilizing the piezoelectric properties of quartz, first of all for receiving… This success in the use of quartz as a receiver led me to try (April, 1917) if it would not be possible to utilize it as well for sending supersonic waves, thanks to the inverse phenomenon of piezoelectricity »[2]

The SONARs that were then used during WWII and later on, untill nowadays are indeed based on the use of the piezoelectric effect, whose idea, design and practical realization were entirely due to Paul Langevin (with technical and experimental help from M. Tournier and F. Holweck), according to the second patent filed in 1918, under his sole name.

Patent applied in September 1918: Procédé et appareils d'émission et de réception des ondesélastiques sous-marines à l'aide des propriétés piézo-électriques du quartz. Paul Langevin. [P3]

Street address(es) and GPS coordinates of the Milestone Plaque Sites

ESPCI Paris - 10 rue Vauquelin -75005 Paris France, ESPCI Paris - 10 rue Vauquelin -75005 Paris France

Details of the physical location of the plaque

On the wall outside of Langevin's laboratory, next to the building where he had his office.

How the intended plaque site is protected/secured

The plaque site will be on Rue Vauquelin, out of reach of pedestrians but visible by all public. It will be on the outside wall of the laboratory where Paul Langevin worked on the sonar in a sink that is still visible inside the Lab.

Historical significance of the work

Historical context:

 In 1912 the Titanic sank after colliding an iceberg. A few months later, an English scientist Lewis Richardson filed a patent for echolocation of icebergs in water. The detection of undermarine objects was also investigated by Alexander Belm in Austria and Reginald Fressenden in the US. 

The First World War had created a maritime blockade around Great Britain, that was the allies base for logistics. Aware of this situation, the German Minister von Brettreich declared: "Our submarines will have completed their glorious task in a few months and we will have won the war". The considerable extent of the maritime losses inflicted on the Allies by the German submarines made therefore necessary all scientific and technological efforts to detect them.

The birth of modern ultrasonics: The period beginning around 1916 can be considered as the start of modern ultrasonic development. Indeed , the idea of using high-frequency elastic waves to detect obstacles through echo technique was first proposed by M.L. Fry Richardson in 1912, in an English patent. In 1915, Constantin Chilowski submitted to the French government a project using submarine ultrasound waves to detect submarines and mines. The aim was to use a vibrating antenna of such dimensions that it could, on reception, provide sufficient directional localisation to have usable telemetry. The French Ministry of the Navy commissioned Paul Langevin to examine this proposal. The latter gave up his previous research interests to fully investigate the use of piezoelectric transducers in order to design an ultrasonic detection device able to detect both distance and direction. Two different technologies were then studied: the vibrating capacitor (1916 Chilowski-Langevin patent) and the quartz capacitor (1918 Langevin patent). The latter proved to be the most promising.  At this time, E. Rutherford in UK was also working on devices using ultrasound, as well as R.W. Boyle in Canada, who built a quartz ultrasound transducer in 1917. Exchanges of information concerning French work on ultrasonics began in 1917, during which M. Langevin visited England twice. At the end of May 1917, after the successful tests of quartz both in reception and emission, Sir Ernest Rutherford and Commander Bridge came to Paris where M. Langevin informed them of the latest results. Sir Ernest Rutherford and the British officer then joined Professors Abraham and Fabry on a scientific information mission to the USA. In August 1917, the American physicist Wood visited Langevin to show him the effects of high intensity ultrasound on fish. Dr R.W. Boyle of the Admiralty Experimental Station of Harwich came to Toulon in July 1917 and returned in June 1918 at the time when the US equipment with steel quartz triplet and triodes was ready for a first practical implementation. After two convincing official tests in front of the Commission d'Etudes Pratiques des Armes sous-marines in June and July 1918, the results of which are recorded in a report by M. de Broglie on July 10th 1918, the French Navy manufactured 6 ultrasonic devices for submarines search. These will only be ready after the armistice. In October 1918 an inter-allied conference on SONARs met under the presidency of M. Cels. See[4].

Impact of the invention: While these efforts had little effect during the first world war since they were mature only by the end of the conflict, they had a considerable impact during the Second World War. These developments also paved the way for civil applications such as, for instance the use of medical ultrasound to visualize the interior of a non-transparent environment in echography. Developments in this field are still very active, and still noticeably rely on the use of piezoelectric materials. The same technology also contributed to the early development of depth sounding, that was particularly important for the laying of underwater cables by telegraph companies and the establishment of marine charts by military hydrographic services, with an improved patented sounder developed by Langevin and Florisson from 1919 to 1924. See [5]. This work is also pioneering in its use of applied and basic science (and not just empirical approach) to solve military problems. It helped proving that scientific advance can result in military advantage.

The acronym SONAR means « Sound Navigation And Ranging », and was used for the first times during WW2. One can make a distinction between passive SONARs, such as microphonic devices and active SONARs, which emit a sound in the water to detect an echo from the obstacle and determine its direction and distance, of the type that was invented by Langevin and Chilowski. The word SONAR is also used for dolphins and some whales which use an active echolocation technique.

Features that set this work apart from similar achievements

The need to detect an obstacle, such as an iceberg in the case of the Titanic sinking in 1912, had boosted research in the field of radio waves. However in order to detect underwater obstacles, electromagnetic waves were no longer an option, and sound waves were considered. And in this context, Langevin and Chilowski built together the first active SONAR, that was shortly after improved thanks to Langevin’s detailed knowledge of piezoelectricity.  In the first patents, the transmitter was a vibrating capacitor associated with a granular carbon microphone [P1, P2]. However the accurate detection of underwater obstacles required the optimization of the transmitter diameter and transmission frequency. This led Paul Langevin to take an interest in piezoelectric quartz and to use it as a receiver [P3]. Since the amplifier associated with quartz in echo reception has a high gain, it was necessary to find a way to avoid blinding it during emission and several "electronic" difficulties had to be solved. The problem of signal recording was solved later on. This achievement was the first realization of an ultrasonic echo detection (active SONAR). It was elaborated in a war context where its inventor, Paul Langevin gave up completely his current research to contribute to this invention. The novelty of this work was to use piezoelectric effect for emission and reception of ultrasounds with sufficient sensitivity and in a way that both distance and direction of the undermarine object could be inferred [P1,P2, P3]. Langevin and Chilowski’s SONAR represented a breakthrough compared to other techniques that were used for submarine detection at that time. Indeed, around 1917, the Royal Navy tried to train sea lions to track German U-boats. They were trained in pools by Joseph Woodward, a famous sea lion trainer at that time, but unfortunately they were not very focussed while in the open water. Once, while supposed to chase a Royal Navy Submarine, they opted for chasing fishes instead and went missing for hours!

Significant references

Langevin Patents :

[P1] Chilowsky CM, Langevin MP. Procédés et appareils pour la production de signaux sous-marins dirigés et pour la localisation à distance d’obstacles sous-marins. French patent #502913, 1916 File:Patents, 1916-17 Chilowsky and Langevin.pdf French version of the following patent.

[P2] Chilowsky CM, Langevin MP. Production of submarine signals and the location of submarine objects. US Patent #1471547, 1917 File:Patents, 1916-17 Chilowsky and Langevin.pdf

[P3] Langevin MP. 1918 ‘Procédé et appareils d’émission et de réception des ondes élastiques sous-marines à l’aide des propriétés piézo-électriques du quartz’ (Brevet francais, No. 505703, 17 Septembre 1918)File:Brevet 505.703 1918.pdf File:Translation Résumé French patent 1918.pdf

[P4]: Langevin, Paul, 'Piezoelectric signaling apparatus', US Patent 22498870, N° 390,542, June 21rst 1920 File:US2248870.pdf

References: [1] Shaul Katzir, Who knew piezoelectricity? Rutherford and Langevin on submarine detection and the invention of sonar, Notes and Records, The Royal Society Journal of The History of Science, March 7, 2012 File:Rsnr.2011.0049.pdf [2] David Zimmerman, Paul Langevin and the Discovery of Active Sonar or Asdic, The Northern Mariner/Le marin du nord, XII, No. 1, pp. 39-52, January 2002 File:Tnm 12 1 39-52.pdf [3] David Zimmerman, “‘A more creditable way’: The discovery of active sonar, the Langevin–Chilowsky patent dispute and the Royal Commission on Awards to Inventors. War in History 2018, Vol. 25(1) p 48–68 [4] Interallied Conference 1918 p13 and its partial translation. File:Text from Interallied conference 1918 P13.pdf Interallied conference 1918 Page 13.jpg [5] Benoit Lelong:"How to coordinate labs and open sea experiments ? Forms of innovation in the French and English navies", in Documents pour l'histoire des techniques (2011) File:Benoit Lelong's paper (translated).pdf

Supporting materials

File:Patents, 1916-17 Chilowsky and Langevin.pdf File:US2248870.pdf File:Brevet 505.703 1918.pdf File:Translation Résumé French patent 1918.pdf File:Rsnr.2011.0049.pdf File:Tnm 12 1 39-52.pdf File:Text from Interallied conference 1918 P13.pdf Interallied conference 1918 Page 13.jpg File:Benoit Lelong's paper (translated).pdf