Misty Castle: High-Explosive Nuclear Effects Simulations at White Sands Missile Range

History of Nuclear Effects Testing and Simulations

Even before World War II concluded with the surrender of Japan in 1945, the victorious Allied Powers had already begun to split apart into the pacts and alliances that would come to define the Cold War. With the United States and the Soviet Union as the two world superpowers, the potential of anthropogenic Armageddon, in the form of nuclear weapons, came to dominate politics, international relations, and even the everyday life of people all around the world. Each side would come to spend decades investing in evermore numerous and powerful nuclear bombs and missiles. The technological sophistication and complexity required to harness the power of the atom had never been seen before. However, even something as complex as a nuclear bomb could not stop the race between arms and armor that has been ongoing throughout humanity’s entire history.

Once military officials began to understand the many hazards and variables that accompany a nuclear blast, such as intense heat, radiation and fallout, and the explosion itself, they initiated programs designed to protect their own forces and citizens. Protective personal equipment, hardened shelters, and radiation-resistant armored vehicles became a standard part of a military unit’s table of equipment. However, in order to ensure that this equipment is actually able to do what it is designed for, rigorous testing is required.

Large-scale nuclear environment simulation began before it was known if it was even possible to split the atom and cause a nuclear explosion. During World War II, the US Army’s Manhattan Project was preparing a site out in the middle of the New Mexican desert on the Jornada del Muerto. This site, which we now know as Trinity Site, would be the test location of the first atomic weapon, called “the Gadget.” As a precursor to the actual Trinity Test, engineers and technicians needed to calibrate the equipment that would record the Trinity detonation. To do this, personnel chose to create a platform that would hold 100 tons of trinitrotoluene, more commonly known as TNT.

“On 7 May 1945, soldiers and technicians stacked 100 tons of TNT on a 20-foot platform for a calibration and procedures check. The known explosive quantity provided a benchmark for seismographs, blast gauges, and other instruments. A small amount of radioactive material was threaded through the stack in tubing to calibrate other instruments that would be used to measure the amount of radiation released by the bomb.”

“Although it was understood that the atomic bomb’s yield could be as high as 20,000 tons, test plans were based on yield limited to 10,000 tons with the most probable yield estimated as 4,000 tons, if it worked at all. Much was learned and refined for what was to be the first field, rather than laboratory, atomic test.”

In the first decades of the Cold War, nuclear effects testing was typically conducted during nuclear detonation events. Testing efforts became a matter of national security following the Soviet test of their own nuclear weapon in 1949. The outbreak of the Korean War in 1950 only served to increase the pace and urgency of US testing events. Notable tests included Castle Bravo (1954), Coulomb-C (1957) as a part of Project 58/58A (1957-1958), Operations Hardtack I and II (1958), Operation Nougat (1961-1962), and Operation Sunbeam (1962).

Following the adoption and ratification of the 1963 Partial Test Ban Treaty by the Soviet Union, United Kingdom, and United States, high-explosive field testing began to rise in importance for the Department of Defense. Although most high-explosive testing could be done with TNT, producing or procuring enough TNT for multiple large-scale field tests with a yield similar to even a small nuclear weapon would become prohibitively expensive.

Although many different types of explosives were created and tested before and after the discovery of TNT, which is classed as a secondary explosive, many of the problems with these and similar materials revolved around safety and scalability. Primary explosives such as nitroglycerin are far too sensitive to be used on a large scale, as they could be set off by interacting with relatively minute amounts of electricity, impacts, friction, or heat. Explosive gases proved just as unreliable. An attempt to use 20 tons of an oxygen-propane mixture as a large-scale explosive ended in failure after the hemispherical balloon holding the mixture experienced structural failure.

A possible solution would be found in 1966 and came in the form of Ammonium Nitrate – Fuel Oil, or ANFO, a tertiary explosive. Although ANFO had been used in the mining industry for years, it was not until L. D. Sadwin and J. Petes, both scientists with the Naval Surface Weapons Center, proposed its use in explosives testing that ANFO came to dominate in the world of large-scale high-explosive testing. Ammonium nitrate is a common commercial fertilizer and is used so heavily that its production can be measured in terms of millions of pounds per day. Number 2 Fuel Oil is mixed in with the ammonium nitrate, resulting in an extremely stable and insensitive mixture that is safe to handle.

While the idea of using ANFO was being batted around various research offices, departments, and organizations, the Department of Defense continued using TNT for simulation purposes. Operations Snowball (1964) and Sailor Hat (1965) used 500 tons of TNT in multiple test events. Following these successful tests, 500-ton charges would be used as the standard configuration in multiple tests that included Operations Prairie Flat (1968), Mine Shaft (1968-1969), Dial Pack (1970), and Mixed Company (1972).

The cost of using TNT became apparent quickly, with 500-tons of TNT costing upwards of $1,000,000 (almost $10,000,000 in 2023 when adjusted for inflation according to the Bureau of Labor Statistics CPI Inflation Calculator). With multiple smaller, but still successful tests under their belts, the DoD’s testing and research community grew evermore confident that ANFO was the appropriate substitute for TNT. Experiments using shaped charges and different configurations of initiator charges also showed promising results. By 1974, the Defense Nuclear Agency (DNA), as a part of its upcoming Dice Throw (1976) community testbed pilot, began to consider the possibility of using ANFO instead of TNT. With the date of the test rapidly approaching, the DNA decided to conduct a number of pre-test events. On White Sands Missile Range, the first series of tests were named Pre-Dice Throw I and Pre-Dice Throw II (both 1975).