Note:  This is an article about the history of electromagnetic pulse based on material that I originally wrote for Wikipedia.  The "Electromagnetic Pulse" article in Wikipedia occasionally gets trashed, sometimes by people with good intentions, other times as the result of vandalism.  So I think it is important to keep this information here in a well-referenced and authenticated style.  I will be adding more to this later.

Earliest History

The fact that an electromagnetic pulse is produced by a nuclear explosion was known since the very first days of nuclear weapons testing, but the magnitude of the EMP and the significance of its effects were not realized for some time.¹

During the first United States nuclear test in 1945, electronic equipment was shielded due to Enrico Fermi's expectation of an electromagnetic pulse from the detonation.  The official technical history for that first nuclear test states, "We can understand the difficulty of transmitting signals during the explosion when we consider that the gamma rays from the reaction will ionize the air and other material within hundreds of yards.  Fermi has calculated that the ensuing removal of the natural electrical potential gradient in the atmosphere will be equivalent to a large bolt of lightning striking that vicinity. . . .  All signal lines were completely shielded, in many cases doubly shielded.  In spite of this many records were lost because of spurious pickup at the time of the explosion that paralyzed the recording equipment."⁴  During British nuclear testing in 1952-1953 there were instrumentation failures that were attributed to "radioflash," which was then the British term for EMP.^{5, 6}

The high altitude nuclear tests of 1962, as described below, increased awareness of EMP beyond the original small population of nuclear weapons scientists and engineers.  The larger scientific community became aware of the significance of the EMP problem after a series of three articles were published about nuclear electromagnetic pulse in 1981 by William J. Broad in the weekly publication Science.^{1, 2, 3}

Starfish Prime

On July 1962, a 1.44 megaton United States nuclear test in space, 400 kilometers (250 miles) above the mid-Pacific Ocean, called the Starfish Prime test, demonstrated to nuclear scientists that the magnitude and effects of a high altitude nuclear explosion were much larger than had been previously calculated.  The detonation time was July 9, 1962, at 09:00:09 Coordinated Universal Time, (which was 8 July, Honolulu time, at nine seconds after 11 p.m.).  The coordinates of the detonation were 16 degrees, 28 minutes North latitude, 169 degrees, 38 minutes West longitude.⁷  The actual weapon yield was very close to the design yield, which has been described by various sources at different values in the very narrow range of 1.4 to 1.45 megatons.

The Thor missile carrying the Starfish Prime warhead actually reached a maximum height of about 1100 kilometers (just over 680 miles), and the warhead was detonated on its downward trajectory when it had fallen to the programmed altitude of 400 kilometers.  The nuclear warhead detonated at 13 minutes and 41 seconds after liftoff of the Thor missile from Johnston Island.⁹

Starfish Prime also made EMP effects known to the public by causing electrical damage in Hawaii, about 1,445 kilometers (898 miles) away from the detonation point, knocking out about 300 streetlights, setting off numerous burglar alarms and damaging a telephone company microwave link.⁷

Starfish Prime was the first successful test in the series of United States high-altitude nuclear tests in 1962 known as Operation Fishbowl.  The subsequent Operation Fishbowl tests gathered more data on the high-altitude EMP phenomenon, especially the Bluegill Triple Prime and Kingfish test of October, 1962.⁸

The EMP damage of the Starfish Prime test was quickly repaired because of the ruggedness (compared to today) of the electrical and electronic infrastructure of Hawaii in 1962.  Realization of the potential impacts of EMP became more apparent to some scientists and engineers during the 1970s as more sensitive solid-state electronics began to come into widespread use.

The relatively small magnitude of the Starfish Prime EMP in Hawaii (about 5600 volts/meter) and the relatively small amount of damage done (for example, only 1 to 3 percent of streetlights extinguished)¹⁰ led some scientists to believe, in the early days of EMP research, that the problem might not be as significant as was later realized.  Newer calculations⁷ showed that if the Starfish Prime warhead had been detonated over the northern continental United States, the magnitude of the EMP would have been much larger (22 to 30 kilovolts/meter) because of the greater strength of the Earth's magnetic field over the United States, as well as the different orientation of the Earth's magnetic field at high latitudes.  These new calculations, combined with the accelerating reliance on EMP-sensitive microelectronics, heightened awareness that the EMP threat could be a very significant problem.

Operation K, including Soviet Test 184

See the separate comprehensive and referenced article covering The Soviet Nuclear Tests in Space.

Non-nuclear history

The concept of the explosively pumped flux compression generator for generating a non-nuclear electromagnetic pulse was conceived as early as 1951 by Andrei Sakharov in the Soviet Union,¹²  but nations have usually kept their most recent work on non-nuclear EMP highly classified until the technology was old enough that similar ideas were widely conceived by physicists in other nations.

References:

1. Broad, William J. "Nuclear Pulse (I): Awakening to the Chaos Factor," Science. 29 May 1981. Vol. 212. pp. 1009-1012

2. Broad, William J. "Nuclear Pulse (II): Ensuring Delivery of the Doomsday Signal," Science. 5 June 1981. Vol. 212 pp. 1116-1120

3. Broad, William J. "Nuclear Pulse (III): Playing a Wild Card," Science. 12 June 1981. Vol. 212. pp. 1248-1251

4. Bainbridge, K.T., Trinity (Report LA-6300-H), Los Alamos Scientific Laboratory. May 1976. Page 53.

5. Baum, Carl E., From the Electromagnetic Pulse to High-Power Electromagnetics. Proceedings of the IEEE, Vol.80, No. 6, pp. 789-817. June 1992.

6. Baum, Carl E., "Reminiscences of High-Power Electromagnetics," IEEE Transactions on Electromagnetic Compatibility. Vol. 49, No. 2. pp. 211-218. May 2007.

7. Vittitoe, Charles N., Did High-Altitude EMP Cause the Hawaiian Streetlight Incident?. Sandia National Laboratories. June 1989.

8. Longmire, Conrad L., "Fifty Odd Years of EMP", NBC Report, Fall/Winter, 2004. pp. 47-51. U.S. Army Nuclear and Chemical Agency.

9. Dyal, P., Air Force Weapons Laboratory. Report ADA995428. Operation Dominic. Fish Bowl Series. Debris Expansion Experiment. 10 December 1965. Page 15.

10. Rabinowitz, Mario (1987) Effect of the Fast Nuclear Electromagnetic Pulse on the Electric Power Grid Nationwide: A Different View. IEEE Transactions on Power Delivery, PWRD-2. pp. 1199-1222.

11. Longmire, Conrad L. Theoretical Notes - Note 353 - March 1985 - EMP on Honolulu from the Starfish Event. Mission Research Corporation.

12. Stephen Younger, et al.  Scientific Collaborations Between Los Alamos and Arzamas-16 Using Explosive-Driven Flux Compression Generators. Los Alamos Science, No. 24, pp. 48-71, 1996.