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

Misty Castle VI: Distant Image (1991)

Date: 20 June 1991
Location: Permanent High-Explosive Test Site (PHETS), White Sands Missile Range
Explosive Charge: 2,650 tons, ANFO

Objectives

Primary Objective: Provide a testbed for airblast, ground shock, dust loading, and thermal radiation effects for DoD-sponsored experiments. These experiments were designed to determine the response of tactical and strategic weapon systems, communications equipment, vehicles, and a variety of structures to a simulated nuclear environment.

Secondary Objective: Provide a thermal environment (in addition to airblast) for several experiments.

By the Numbers

1. 400 personnel
2. 117 experiments
3. 1,795 active and passive gauges
4. 1,395 recording channels
5. 124 miles of cable
6. 95 experiment response cameras
7. 11 unmanned instrumentation bunkers

Event Summary

Planning for the Distant Image event began soon after the completion of the Misers Gold event in 1989. Experiment selection was conducted in December 1989 by a Defense Nuclear Agency Technical Review Committee. As in every previous event in the Misty Castle test series, Distant Image planned to use a high-explosive charge to produce a shockwave and airblast environment to test various hardened structures, equipment, and vehicles. Additionally, Distant Image would use thermal radiation source units to add a thermal variable to the test environment.

The explosive charge was planned to consist of 2,440 tons of ANFO loaded into a hemispherical fiberglass container 35 feet in radius. However, with a change in fill procedures, the final fill weight totaled 2,650 tons. The detonation of this charge provided the approximate equivalent airblast of a 4-kiloton nuclear device. This was the first test in which the ANFO charge was larger than planned. This was primarily due to a change in the location of the initiating charge, which allowed for more ANFO to fill the vacated space.

For Distant Image, test planners opted to use many of the same facilities used during the Misers Gold event. Distant Image ground zero was located 500 feet southwest of the Misty Picture ground zero. This location allowed the reuse of nearby roads, the instrumentation bunkers, the instrumentation radials, and some of the diagnostic camera mounds. The majority of the diagnostic gauge cables from Misers Gold had been left in place and were reused for Distant Image.

In addition to the many US contractors and organizations participating in the event, Canada, France, Norway, Sweden, Switzerland, and the United Kingdom fielded their own experiments. There were a total of 117 experiments placed around the testbed. Although most of the experiments were located in the vicinity of ground zero, the farthest experiment from ground zero was located in Abilene, Texas, a distance of more than 400 miles. Other airblast sensors in New Mexico were located in San Antonio, Socorro, Bingham, and Carrizozo.

As opposed to the previous events in the Misty Castle series, airborne operations did not play a large part in Distant Image. Only a single Cessna 180, flying from Socorro Municipal Airport, was used to monitor and document fireball, shockwave, ejecta, and cloud development of the event.

The ANFO mixing plant built for use in Minor Scale was used again for Distant Image. Filling the hemispherical container began on 10 June and was complete by 17 June. The only setback occurred on 11 and 12 June, when thunderstorms over the northern range forced a pause in outdoor events. Aside from these weather-related issues, preparations proceeded normally, with a total of 95 cycles of dump trucks carrying 30.2 tons of ANFO each cycle.

The crater was predicted to be about 230 feet in diameter and 55 feet deep. The crater was measured to be 274 feet in diameter and 68 feet deep. Post-event analysis revealed that the Distant Image crater was larger than expected and around 20% larger than the crater created by Misers Gold. A possible explanation for the size of the crater was that the earth used to fill in the crater from Misers Gold was less dense than the earth it replaced. However, this is a speculative explanation and was not studied in detail before site cleanup began.