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

Misty Castle I: Mill Race (1981)

Date: 16 September 1981
Location: Approximately 3.5 miles south of Trinity Site, White Sands Missile Range
Explosive Charge: 600 tons, ANFO

Section of video that shows the Mill Race test event. Thanks to the Atomic Tests Channel for this video.

Primary Objective: Provide and record an airblast and ground motion environment designed to determine the response of various DoD-sponsored experiments, including tactical and strategic weapons systems, communication equipment, aircraft vehicles, radar and antenna systems, and a variety of structures.

Secondary Objective I: Record damage to DoD-sponsored experiments.
Secondary Objective II: Record combined thermal/airblast effects.
Secondary Objective III: Increase the nuclear weapons effects database.

Experiment and Measurement Types

In general, most of the experiments fielded as a part of the Misty Castle series fell into one of four categories. Categorizing different experiments helped project planners place each one in an appropriate zone surrounding ground zero. These zones, bounded by roads used as radials, allowed for different preparatory work, such as building bunkers or shelters, in a way that enabled each experiment to be carried out without interfering with others on the testbed.

Phenomenology: Conduct ground motion and airblast measurements, test of stress gauge design, elevated airblast and airflow measurements, source characterization, and measurements of magnetic field perturbations.

Structures: Determining the vulnerability and investigating the response of scale model steel, wood, brick, and concrete block buildings, silos, and other types of shelters.

Systems: Investigating the survivability and vulnerability of various type of ships antennae, van mounted shelters, trailer disk antennae; tank and armored fighting systems and vehicles, airblast effects on simulated crews in vehicles and shelters and in the open, clothed in protective clothing; and determining the hardness of a Seawolf launcher, communications box body, and Ptarmigan masts.

Dust and Debris: Measuring dust density and particle size, measuring the attenuation/degradation of optical systems due to dust/cloud formation, and defining the impact, breakup, and redistribution of debris.

By the Numbers
  • 136 cameras of various types
  • 862 sensors to record raw data
  • 490 miles of cables and wires (roughly the distance from Albuquerque, New Mexico, to Denver, Colorado)
  • 100 airblast gauges to record overpressures
  • Over 200 personnel with skills ranging from carpentry, masonry, and machinery to technicians, scientists, and program managers
Event Summary

Mill Race was the first high-explosives test in the Misty Castle series and occurred on 16 September 1981. The Misty Castle program consisted of several large scale, high-explosives weapons effect field tests run by the United States Defense Nuclear Agency (DNA). Like all of the other Misty Castle tests, Mill Race was located on the northern portion of White Sands Missile Range (WSMR), New Mexico, only a few miles from Trinity Site, where the first atomic device was tested in 1945 as part of the Manhattan Project. WSMR proved to be an ideal location for large-scale explosive testing due to its flat terrain, varying geological conditions, and distance from population centers, all while still being close enough for logistical support.

Prior to Mill Race, the US conducted several similar high-explosive tests. Dice Throw (1976) was also conducted at White Sands Missile Range, while Misers Bluff (1978) was conducted at Planet Ranch, Arizona. These high-explosive test events were designed to mimic the explosive yield of a nuclear weapon without the residual fallout that the weapon produces. Simulations using conventional explosives became the primary way to test the effects of nuclear weapons after the Soviet Union, the United Kingdom, and the United States signed and ratified the 1963 Partial Test Ban Treaty, which prohibited nuclear weapons testing in the atmosphere, in outer space, and underwater. While underground nuclear weapons testing was still permitted, the confines of an underground space made nuclear effects testing sub-optimal.

The Mill Race test used 600 tons of ammonium nitrate – fuel oil, abbreviated as “ANFO,” as the primary explosive. This amount of ANFO produced the equivalent of approximately 500 tons of TNT and was expected to simulate the blast and shock of a one-kiloton nuclear bomb. Additionally, multiple arrays of a nozzle-dispensed aluminum powder and liquid oxygen mixture provided a strong heat source for experiments designed to evaluate the combination of blast effects and thermal radiation produced by a thermonuclear weapon.

In order to create the desired detonation effects, approximately 24,000 fifty-pound bags of ANFO, with loose ANFO filling the spaces between the bags, were stacked in a cylindrical shape with a hemispherical dome. The 37.4-foot high and 30-foot diameter dome was located at the center of a 100-acre test bed.

24,000 bags of ANFO were stacked in a cylindrical shape and topped off in a hemispherical dome. In the background are various types of equipment to be used on the testbed during the detonation.

Approximately 106 individual experiments were conducted as a part of Mill Race. These experiments, taking place on the ground, under the ground, and in the air, included tests on:

-Above-surface and partially buried shelters, blast shelters, and industrial buildings
-Various radomes and antennas
-Communication vans
-Anthropomorphic dummies in protective gear
-Pillow tanks and bladder tanks
-Cloud and atmospheric conditions immediately after the explosion
-Ship deck houses
-Ejecta and other debris
-Armored and hardened vehicles
-Remote pressure sensors
-Flying aircraft

Mill Race was detonated at 1236 MDT on 16 September 1981 after a hold of 2 hours and 36 minutes due to computer problems with two of the drones participating in the test. Approximately 400 people observed the test from an observation point located on the rise to the Oscuro Mountains. Unlike future test events in the Misty Castle series, Mill Race was an unclassified event. Experiment damage evaluation, analysis, and recovery commenced immediately after the test. The crater left by the explosion was back-filled and the entire site was restored in a way so that the site could be reused for other high-explosive tests.

Starting from the initial planning phase that began in August 1980 to the end of the site restoration phase in January 1982, Mill Race was completed in 17 months. In March 1982, the Mill Race Test Group Staff held a Results Symposium for the participating agencies and organizations to share the findings from the many experiments conducted during the test.

After Mill Race, White Sands Missile Range created a site with permanent office buildings, equipment storage, electrical power, and communications systems. Designated as the Permanent High Explosive Test Site (PHETS), this site is still manned and maintained by the Defense Threat Reduction Agency (DTRA).

One thought on “Misty Castle: High-Explosive Nuclear Effects Simulations at White Sands Missile Range

  1. I enjoyed reading the information provided and researched for all the Misty Castle projects. I appreciate the Museum putting this together for all the men and women who worked on the Stallion side of the range on these projects.

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