Tesla’s Reflections on Radar and Ships Wrapped in Coils of Wire

Just after receiving the AIEE’s Edison medal (May 18, 1917), Nikola Tesla granted an interview to H.W.

Secor of the Electrical Experimenter magazine. (Secor’s article was published in August of 1917).

The topic of discussion turned to the detection of German U-boats (U-boat = Unterseeboot = submarine), which had caused so much distress to the allies.

The US had entered the war in April of 1917. Tesla’s concerns centered around the detection of submarines, in particular the possibility of non-ferrous hull detection.

Listen as, filtered by the pen of a journalist, Tesla narrates the electrical preparation of the ship:

«Now, suppose that we erect on a vessel, a large rectangular helix or an inductance coil of insulated wire. Actual experiments in my laboratory at Houston Street (New York City), have proven that the presence of a local iron mass, such as the ship’s hull, would not interfere with the actions of this device. To this coil of wire, measuring perhaps 400 feet in length by 70 feet in width (the length and breadth of the ship*) we connect a source of extremely high frequency and very powerful oscillating current».(24)

We think that Vannevar Bush was aware of this suggestion, and it is our thesis that these words are the seed that later blossomed as the “Philadelphia Experiment”.

The article then goes on to describe an RF technique which subsequently became quite popular (though not on such a grand scale) for metal detectors and for tuning the reactance of RF coils in transmitters and receivers.

Upon further prodding by Secor, Tesla discussed a high peak power microwave radar for operation at wavelengths “… of but a few millimeters”. (X-Band radar at 10 GHz has a wavelength of 30 mm).

Tesla desired that the ship be able to provide sufficient electrical power, and he states this in the interview:

«The average ship has available from say 10,000 to 15,000 HP…. The electric energy would be taken from the ship’s plant for a fraction of a minute only, being absorbed at a tremendous rate by suitable condenser and other apparatus, from which it could be liberated at any rate desired».


*According to Jane’s Fighting Ships (1967-68, pg. 408), the Eldridge (DE-173) was 306 feet long by 37 feet at the beam, and had a draft of 14 feet. Its main engines were GM diesel, electric drive, 2 shafts, 4.5 Mw.

Clearly, Tesla was contemplating the use of pulsed currents* in the coils around the ship. Remarkably, vessels wrapped in coils were observed during WW-II (perhaps for mine sweeping or even degaussing studies). [According to Moore, Francis Bitter, of MIT, recalled witnessing “a relatively large ship carrying … a bar magnet going from the bow … way aft. This bar magnet had coils wound around it which passed current produced by motor generators.”(25)] By the way, the Eldridge’s generator was rated at 4,600 KVA and coul deliver 6,000 HP. Two generators, as described in the book, could deliver more than 12,000 HP (almost 9 Mw).

It is not clear that Mr. Secor even fathomed what Dr. Tesla was speaking about. How much of what was published in the article were Tesla’s ideas and what was added (or deleted) by Secor is not transparent. (We have the same problem with ONeill’s colorful biography.) After Tesla’s brief discussion of sonar, Secor mixes together the RF magnetic detection process and the “electric ray” radar technique. While Secor’s version of Tesla’s disclosures might sound, today, like oversimplified impractical popularizations, Secor was quick to conclude his 1917 article with the disclaimer,”… several important electrical war schemes will shortly be laid before the War and Navy Departments by Dr. Tesla, the details of which we naturally cannot now publish.”(26) Margaret Cheney has observed that, at the time, Thomas Edison

“… had been named to direct the new Naval Consulting Board in Washington, with the primary job of finding a way of spotting U-boats. Tesla’s idea, if even brought to Edison’s attention, would almost certainly have been discounted.”(27)


*”I will tell you the secret of all these wonderful displays. … Consider a large gun which hurls a projectile of a ton a distance of 18 or 20 miles. If you figure the horsepower at which the gun delivers energy, you will find that it amounts to from 6 to 12 or 15 million horsepower. … With the methods which I have devised, with my transformer, it is not at all difficult to get rates of energy many times that. … in the plant on Long Island, if I wanted to operate, I could have just reached a rate of 1 billion horsepower. … That wonderful thing can be accomplished through a condenser. The condenser is the most wonderful electrical instrument … You store less energy in the condenser than in the gun, but whereas a gun will discharge … all these effects which elicited great wonderment of the profession, were always produced by damped waves, because with the undamped waves it would not have been possible to attain any such activities.” [Tesla on His Work With Alternating Currents, by L.I. Anderson, 1992, pp. 112-113.]

It should also be noted that Vannevar Bush was involved in the same endeavor:

“During 1917-18 [Bush] was engaged in research on submarine detection in connection with the United States Navy special board on submarine devices.”(28)

In 1917, Bush, fresh out of graduate school,* was a newly appointed assistant professor of electrical engineering at Tufts College in Medford, Massachusetts and consulting for the American Radio and Research Corporation. [AMRAD was a J.P. Morgan venture, built on the Tufts campus, which manufactured “thousands of transmitters and receivers” during WWI.(29)] Bush was one of the guiding lights for a spin-off company which, in 1925, was renamed Raytheon.** (In 1941 Raytheon became the prime source for the new Navy Search Radar.(30)) Bush joined the MIT EE Department faculty (his specialty, initially, was electrical power and subsequently operational calculus and analog computers (the famous network analyzer)) and became Dean, and then Vice-President of MIT in 1931.*** He accepted the position of President of the Carnegie Institution of Washington in 1938 (and held the position until 1955). He was Science Advisor to the President and was appointed by Roosevelt as chairman of the National Defense Research Committee (July, 1940),****as director of OSRD – the Office of Scientific Research and Development (1941), and as Chairman of the Joint Committee on New Weapons and Equipment of the Joint United States Chiefs of Staff (1942).(31)

*Bush received a BS and an MS from Tufts College (1913), Doctor of Engineering jointly from MIT and Harvard (1916), and eventually 10 honorary doctorates from various colleges and universities. During his remarkable career, he was science advisor to several Presidents. He was Vice-President and Dean of Engineering at MIT in 1931, the year that he wrote to Tesla.

**Raytheon, in fact, (with 25% of the EE department involved) came to be known by the grad students at MIT in the late 1920’s as “an extension of the Electrical Engineering Department.” (See Reference 29.)

***Ever the entrepreneur, when Bush heard A.F. Joffe of the Polytechnic Institute of Leningrad present his ideas on a new superdielectric for HV insulation, he rallied his investor friends and went to Leningrad and Moscow. (As described in his autobiography, Pieces of the Action (Morrow, 1970), the enterprise resulted in failure.)

****Recall that John G, Trump, accompanied by three Naval personnel, examined Tesla’s personal papers when he died in January of 1943. Trump was Secretary of the Microwave Committee of the National Defense Research Committee from 1942 until 1944 when, as a member of General C.A. Spaatz’s Advisory Special Group on Radar, he went to Europe as the Director of the British Branch of the (MIT) Radiation Laboratory. (See Electrical Engineering, Vol. 80, No. 5, May, 1961, pp. 364-365.) [General Spaatz, by the way, was Air Force Chief of Staff and headed the “very secret” committee on UFO’s. According to Irving Langmuir, (Physics Today, October, 1989, pg. 48) Spaatz had confided, “You Know it’s very serious. It really looks as though there is something there.” (Also see Physics Today, March 1990, pg. 13 and April, 1990, pg.13] Vannevar Bush guided much of the Nation’s weapons research during WWII. According to Frank B. Jewett* (President of the National Academy of Sciences), as head of OSRD Bush

“… directed the mobilization of the entire civilian scientific and technical power of the nation and welded it together into the military establishment in the greatest industrial research and development man has ever known.”(32)

Recall that Vannenar Bush, while Vice President of MIT, had sent Tesla birthday greetings in 1931:

“Dear Dr. Tesla … I wish to join to my own tribute of admiration for your unique career the congratulations of the Massachussets Institute of Technology, where the contribution which your original genius has made for the benefit of mankind is fully appreciated.”(33)

In 1943, Bush, like Tesla in 1917, received the AIEE’s highest honor (at that time the Edison Award). Bush held about 50 US patents for various inventions. Let us move ahead from Tesla’s suggestion, to place coils of wire on a ship, to radar and radar counter-measures (stealth).


1994 Tesla Symposium at Colorado Springs


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Sommerfeld on Electromagnetic Stealth During WW-II

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