In 1958, at the height of the Cold War, the U.S. carried out an experiment in the South Atlantic aimed at testing an innovative defense system. This system involved creating a radiation belt in the outer layer of the atmosphere, over the country, so that missiles launched in a potential Soviet nuclear attack would have their electronic systems disrupted by the interaction with electrons, rendering them useless. Based on the so-called Christofilos Effect, these tests were named Operation Argus.

Nicholas Christofilos was an American electromechanical engineer of Greek descent who, during World War II, worked in Athens for an elevator company. At the same time, he taught himself physics using American and German textbooks. By 1946, he had begun developing advanced ideas about particle acceleration, eventually discovering that when free electrons fell into a magnetic field inside a vacuum chamber, they seemed to follow the path of that magnetic field.

Three years later, Christofilos conceived the strong focusing principle or alternating gradient (the use of electromagnets to make a particle beam converge simultaneously in both directions perpendicular to its travel), laying the groundwork for the creation of the first AGS or Alternating Gradient Synchrotron (a particle accelerator) at New York’s Brookhaven National Laboratory. It was the largest in the world for a long time, capable of reaching an energy of 33 billion electron volts, and is still in operation.

Nicholas Christofilos explaining the Van Allen belts during the preparation of Operation Argus
Nicholas Christofilos explaining the Van Allen belts during the preparation of Operation Argus.Credit: Public domain / Wikimedia Commons

Christofilos did not publish his work in a scientific journal but patented it, so it went unnoticed for a while, and other scientists eventually arrived at the same conclusions, though they acknowledged his prior discovery. In 1956, he was hired by the Lawrence Livermore National Laboratory to work on the Astron, a nuclear fusion reactor, while also participating in several military projects, becoming a member of JASON, a group of young scientists advising the U.S. government on science and technology.

Within that institution, Christofilos became the lead researcher of a project conceived by the DTRA (Defense Threat Reduction Agency), a Department of Defense agency that worked on programs to counteract attacks with weapons of mass destruction—be they atomic, chemical, biological, etc. Specifically, his focus was on the first of these, and in 1957, Christofilos developed the effect that bears his name, based on the capture of charged particles along magnetic field lines. Shortly thereafter, he proposed that this effect could be used to protect the U.S. from a nuclear missile attack.

How? By producing atomic explosions at high altitude, in the outer layer of the atmosphere, to create a radiation belt that would function similarly to the Van Allen belts. These belts, discovered by American physicist James Alfred Van Allen just a short time earlier, in January 1958, thanks to the launch of Explorer I, are two zones in the Earth’s magnetosphere where large quantities of protons and electrons from the solar wind, captured by the Earth’s magnetic field (and to a lesser extent, cosmic rays), accumulate.

The Van Allen belts
The Van Allen belts.Credit: Booyabazooka / Public domain / Wikimedia Commons

By trapping the solar wind, the magnetic field diverts these energetic particles and protects the atmosphere from destruction. However, it endangers satellites, whose sensitive components must be properly shielded. Consequently, Christofilos deduced that the same could happen to intercontinental missiles. It is important to note that once these missiles are launched toward their target, they do not continuously fly through the sky but instead enter space and follow a suborbital trajectory before reentering the atmosphere.

Thus, if they had to pass through a radiation belt filled with beta particles (electrons), these particles would enter the missiles as massive electrical currents and damage the electronic arming mechanisms of their warheads, rendering them harmless. The way to implement this defensive shield was to trigger a series of nuclear fission reactions at the edge of space, generating these particles. Since they would be at altitudes above a hundred kilometers, they would descend to the point where the atmosphere reaches a critical density (50 to 60 km).

That would lead to the formation of a large disk of ionized air beneath the point of the explosion, as the particles would remain parallel to the Earth’s magnetic field, traveling along the lines of force (which are curved and meet the ground near the magnetic poles). In fact, the Department of Defense was concerned with the idea that the Van Allen belts were not natural but the product of high-altitude Soviet atomic tests. It was necessary to send satellites to study them and conclude that there was no reason for concern.

Diagram of the Christofilos effect
Diagram of the Christofilos effect.Credit: Heriberto Arribas Abato / Wikimedia Commons

However, it was enough to spur Operation Hardtack, a series of nuclear tests carried out between April and August of 1958 in Pacific test sites, several locations in Micronesia used for such experiments since 1946. One of them, known as Hardtack-Teak, involved the launch of a Redstone missile (the first U.S. ballistic missile model) from Johnston Atoll, which was detonated at an altitude of 76.8 km with a yield of 3.8 megatons. The result: a disruption of high-frequency radio communications for hours due to persistent ionization.

No radiation belt was created, but the experiment demonstrated the utility of the concept to neutralize enemy communication systems; it could even blind their radars if low-altitude detonations were carried out over the Indian Ocean (where the USSR concentrated its tracking systems), rendering the Soviet A-35 anti-ballistic missile system inoperative and unable to respond to a U.S. attack. So, the next step was to create a radiation belt.

Christofilos proposed conducting nuclear detonations in the upper regions of the atmosphere, as was done with Hardtack-Teak, thus avoiding the effects on people of the bomb’s electromagnetic pulse, radiation, and subsequent fallout. The epicenter was to be the South Atlantic so that the resulting particles would drift towards U.S. territory and form the expected protective umbrella. It had to be done quickly, as at that time the superpowers were negotiating a ban on atmospheric and exoatmospheric atomic tests starting in October.

USS Norton Sound, the ship that launched the three missiles of Operation Argus
USS Norton Sound, the ship that launched the three missiles of Operation Argus. Credit: Marine Photos / Public Domain / Wikimedia Commons

Thus, between August and September of that year, 1958, barely a few months after its conception (under normal conditions, it would have taken much longer, perhaps one or two years), Operation Hardtack-Argus was launched, later renamed Floral but ultimately kept as Operation Argus for security reasons. A budget of $9.023 million was assigned, funded by the AFSWP (Armed Forces Special Weapons Project), predecessor of today’s DTRA (Defense Threat Reduction Agency), but the implementation was a joint responsibility of the Defense Agency, the Atomic Energy Commission, and Lockheed Corporation.

They carried it out using Task Force 88, an anti-submarine squadron created in April that gathered nine warships: the aircraft carrier USS Tarawa; the seaplane tenders USS Albemarle and USS Norton Sound; the destroyers USS Warrington, USS Bears, USS Hammerberg, and USS Courtney. Two other units of Task Force 88 were the USS Salamonie, a supply ship that returned to port without participating, and the USS Neosho, a tanker that refueled the others. In total, 4,500 people, with the entire operation disguised as a scientific test by using International Geophysical Year equipment to collect hydrographic data.

Also, in July, the Explorer 4 satellite was launched into orbit (in August, the launch of the next one, Explorer 5, failed), with a battery that lasted for two months. It was to assist in monitoring the test along with about forty stations scattered across the globe. The launch site was chosen as a point in the ocean south of the Falkland Islands, due to the presence of the so-called South Atlantic Anomaly, a region where the Van Allen belt is at a lower altitude (about 200 kilometers) due to a depression in the magnetic field caused by the fact that its center is offset from the Earth’s geographic center by 550 kilometers.

Location of Taske Force 88 ships during launches during Operation Argus.
Location of Taske Force 88 ships during launches during Operation Argus. Credit: U.S. Defense Nucelar Agency / Public domain / Wikimedia Commons

The spotlight was on the Norton Sound, captained by Arthur R. Gralla—who would be decorated for this mission—which, after World War II, had been converted into a floating missile platform. This ship was responsible for launching the three X-17A missiles, armed with 1.7-kiloton nuclear warheads (one kiloton equals one thousand tons of TNT; the Hiroshima bomb had 16 kilotons), over the course of three days. Argus I was detonated on August 27 at an altitude of 200 kilometers; Argus II on the 30th of the same month at 256 kilometers; and Argus III on September 6 at 539 kilometers (the highest-altitude nuclear explosion ever).

These altitudes were set to prevent the operation’s personnel from being exposed to ionizing radiation, along with other complementary measures. As expected, the explosions created artificial electron belts and demonstrated that they indeed disrupted radar signal transmission and reception, as well as radio communications. Consequently, it was deduced that they would also interfere with the electronic mechanisms of intercontinental ballistic missiles and their warheads.

The theory was proven: a layer of electrons resulting from neutrons and the beta decay of fission products and the ionization of device materials in the upper atmosphere could generate the Christofilos effect. Unfortunately, its practical application fell short of being satisfactory. The belt wasn’t strong enough to guarantee success in the event of an attack—perhaps because the explosions were too limited—and it only lasted a few weeks, making it a weak and short-lived shield. On the bright side, it could be more effective against spy satellites.

The X-17 Argus 3 missile prepared for launch from the aft deck of the USS Norton Sound
The X-17 Argus 3 missile prepared for launch from the aft deck of the USS Norton Sound. Credit: AEC / USDE / Public Domain / Wikimedia Commons

Upon the conclusion of Operation Argus, Task Force 88 returned to the U.S., stopping in Rio de Janeiro, and didn’t officially announce the tests until the following year. Specifically, the documents were declassified in April 1959, although the previous month, two New York Times journalists, Hanson Baldwin (an arms specialist) and Walter Sullivan (a science specialist), had published the scoop under the headline, The greatest scientific experiment ever conducted. They caused a sensation, as even within the academic world there was significant ignorance about the Van Allen belts.

As an epilogue, we can add that Nicholas Christofilos shifted his research to ELF (Extremely Low Frequency), the radio frequency band between 3 and 30 hertz, to apply it to communications with submerged submarines, a system adopted by both the U.S. and Soviet navies and still in use today; he even invented the terrestrial dipole, a transmission antenna to put it into practice.

Christofilos’ ideas, who died of a heart attack in 1972, were not always good (one of his most bizarre was to build a runway stretching across the country from east to west so that a Soviet attack wouldn’t catch all planes grounded), but, as nuclear physicist Herbert York (one of Frank Oppenheimer’s collaborators on the Manhattan Project and director of the Lawrence Livermore National Laboratory) said, Nick was really a genius in a very important sense: he often invented things that required two new ideas simultaneously, something almost no one ever does.


This article was first published on our Spanish Edition on October 8, 2024: Operación Argus, el proyecto estadounidense para crear un cinturón de radiación en el espacio que impidiera un ataque de misiles soviéticos

SOURCES

N. C. Christofilos, The Argus Experiment

Defense Nuclear Agency, Operation Argus, 1958

Defense Nuclear Agency, Operation Hardtack I, 1958

Clayton K.S. Chun, Shooting down a “star”. Program 437, the US Nuclear ASAT System and present day copycat killers

A. C. Melissinos, Nicholas C. Christofilos: his contributions to physics

Lawrence Livermore National Laboratory, Operation Argus

Wikipedia, Operación Argus


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