In October 1976 the Dice Throw test detonated 600 tons of ammonium nitrate & fuel oil (= to 1 kiloton). The results of the Dice Throw Series of high explosives tests were used to substantiate the TAB VEE and the Modified TAB VEE designs and to obtain test data to support further HAS structural design improvements.
The successful deployment of an MX missile system would require a careful consideration of ground shock effects which were of secondary importance in previous applications. For example, with the system sited in a valley and under a multiple attack scenario, untargeted points can be expected to experience a significant ground motion environment as a result of the superposition of motions originating from attacks on a variety of surrounding aimpoints. Furthermore, reflections of outgoing energy from the valley boundaries can be expected to complicate the ground motion environment within the valley, particularly at late times. The objective of this work was to develop a better quantitative understanding of these late time, long period ground motions in order to provide a firmer basis for scaling to new geologic conditions. Particular emphasis was placed on the identification of the characteristic mode of propagation associated with these arrivals.
A theoretical model was used to compute the surface waves produced by a propagating airblast load acting on the surface of a multilayered, elastic half-space. This model was then applied to the analyses of both the observed data and finite difference simulations of the Pre-Mine Throw and Pre-Dice Throw 100 ton HE surface blasts. Mine Throw was a series of tests conducted by the Defense Nuclear Agency using small conventional charges to simulate the blast effects of nuclear weapons.
The program was multi-faceted with many agencies involved each in its own field of experience and competence. The general objectives of this pre DICE THROW effort was to design an ANFO charge that would provide a one to one correlation with the surface tangent sphere configuration (as used an DIAL PACK and MIXED COMPANY) in cratering and blast efficiency and would minimize blast anomalies.
In the early 1960s, the AF began an intensive effort to develop a protective arch shelter for tactical aircraft. The impetus for this was the need to protect parked aircraft at Southeast Asia (SEA) installations. Beginning in 1967 with the Concrete Sky test program, the AF began developing and testing various elements of the aircraft shelter in order to optimize the arch and protective cover configuration. A hardened version of the original SEA aircraft shelter was developed as a result of those tests - the TAB VEE hardened aircraft shelter (HAS). This HAS was also known as the 1st Generation (TAB VEE). Later, when NATO specified requirements for hardened shelters for use within the European theater, the TAB VEE HAS design was modified and re-named the 1st Generation (modified TAB VEE). This design was constructed at NATO installations throughout Europe.
In 1977, new proposed siting criteria were developed for Group I (1st Generation), II (2nd Generation), and III (3rd Generation) HAS relative to ECM. The proposed criteria were based on the results of the Concrete Sky Phase IXB test of explosive propagation between HAS and the 1/3-scale model HAS testing conducted during Dice Throw.
The UH-1B helicopter blast test during the DICE THROW event provided processed structural and motion response data from the hovering and droned helicopter. They are correlated with corresponding analytical predictions based primarily on the helicopter code HELP and the aircraft structural code NOVA-2. The monitored blast-induced responses include: (1) flapwise bending moments and the flapping angles of both the tail and main rotor blade systems; (2) latera bending moments at two fin and two tail boom stations; (3) overall rigid-body motions of the vehicle consisting of the altitude variations, the attitude and angular rate variations in the yaw, pitch, and roll degrees-of-freedom; and (4) strains at selected points on a tail boom panel, a stiffener, and a longeron.^Considering the qualities of the available input data for the analyses and of the measurements, the experimental results are generally in reasonable agreement with the predictions from the HELP code. The NOVA-2 predictions for panel, stiffener, and longeron strains fare poorly when compared with experiment. In some instances, significant differences are found between experiment and analysis.
Structural response tests of Canadian ships masts to blast loading were evaluated in event Dice Throw, a 600-ton explosive trial carried out in October 1976. The test structures were a) a 30 ft Antenna Lattice Mast at 10 psi overpressure, b) a UHF Polemast Antenna at 7 psi and, c) 35 ft Whip Antennas at 7, 10 and 12.1 psi. In addition, aerodynamic drag was measured on cyl-inders of 3.5, 9.5 and 18 inch diameters at 7, 10 and 20 psi. All structures were analyzed prior to test and response predictions made for comparison with field test results. A total of free-field overpressure gauges were distributed in the target area to provide blast wave data. Instrumentation for the structures included high-speed cameras, strain gauges and accelerometers.
As part of Oak Ridge National Laboratory's participation in Defense Nuclear Agency's "Dice Throw" blast test, two Russian Pole- Covered Trench Shelters were tested. Each lacked a trapdoor and filter. As anticipated, so little air flowed through these essentially dead-ended test shelters that temperatures soon became unbearable. Russian earth-covered expedient fallout shelters are based on military dugouts designed for brief occupancy during a conventional attack. Subsequently, they were improved for fallout protection but were made much less habitable by Soviet civil defense specialists. Apparently these specialists were ignorant of ventilation requirements, and almost certainly they did not field-test small expedient fallout shelters for habitability. Tens of millions of Russians had been taught to build such shelters.
Various Department of Defense organizations used the Army standard medium tactical radio relay system for a variety of battlefield communication needs. The U.S. Army Ballistic Research Laboratory (BRL), in conjunction with the Army Engineer Waterways Experiment Station (WES), Agbabian Associates (AA), and the U.S. Army Electronic Research Development Command (ERADCOM), is conducting a research program to develop data and criteria for determining the vulnerability of this system to the effects of tactical nuclear and high-explosive weapons. The system, which was not designed to survive these threats, consists of electronic radio equipment, its protective shelter, and associated antennae. The system was subjected to large-scale high-explosive tests (events DICE THROW and MISERS BLUFF) and acceleration time histories were obtained at various points on the equipment racks containing the electronic gear.
After several meetings conducted by DNA in 1974 where target requirements end options for charge material and configuration were reviewed by representatives of the DoD test community, the decision was made to tentatively plan on using ANFO for the new test. And because of the intriguing possibility that cylindrical charges could satisfy ground motion requirements. DNA initiated an intensive program in 1975 to explore this charge shape and its application to the ANFO explosive. A program very similar to the one proposed by NSWC in November 1970 was started. The press of time--DICE THROW was scheduled for 1976 dictated quick action. If the ANFO cylindrical charge investigation did not prove successful, DICE THROW would have to revert to TNT; it took a long lead tine to process the 500 tons required.
Pre DICE THROW II, Event II, the 120 ton ANFO shot, was an unqualified success. DNA and DNA/FC now proceeded in full gear on Operation DICE THROW with ANFO. This operation was, "designed to meet two primary objectives: 1) provide a simulated nuclear blast and shock environment for target response experiments that are vitally needed by the military services and defense agencies concerned with nuclear weapons effects, and 2) confirm empirical predictions and theoretical calculations for shock response of military structures, equipment, and weapons systems." All the U.S. military services, 28 agencies, and six foreign countries participated in DICE THROW.
A large field operation such as DICE THROW requires a large organization to plan, coordinate, and carry out all the activities. The Field Command/DNA had this responsibility. They assembled a knowledgeable and capable staff made up of experienced and dedicated persons. Field operations at the WSMR started in early 1976 with site preparation and continued through the ANFO charge construction and firing in October to the end of the year when post shot dates recovery and sits clean up were completed. The test site was at the Giant Patriot location about 25 miles northwest of the Queen 15 site where the 120 ton ANFO Pre DICE THROW event took place.
The DICE THROW charge was scaled to the pre DICE THROW II 120 ton charge in all its significant features. The cylindrical portion of the DICE THROW charge had an L/D = 0.75 with a diameter of 29.8 ft and a length of 22.5 ft. This was capped with a 14.9 ft radius hemisphere so that the total height of the charge was 37.4 ft. The charge was constructed from 24,903 bags of premixed ANFO obtained locally in New Mexico. Of this total, 1,755 bags were opened and the loose ANFO used to fill the spaces between the other bags. The total weight of the ANFO in the charge was 621.771 tons. The paper bags, the booster explosives, and miscellaneous material in the charge brought the total weight to 628.27 tons.
The interlocking bag stacking plan developed on pre DICE THROW II was again used but with an added feature; the outer bags of ANFO were glued together to increase the structural integrity of the charge. One other feature was added to charge construction; a protective housing was built in which the charge stacking took place. Neither rains nor storm, nor winds, of which there were ample number at the White Sands Missile Range test site, deterred or harmed the stacking task. The housing was designed so that it could be removed easily prior to the shot, be stored, and be ready for use as needed for other charge stacking jobs.
The seven point initiation/boostering design was 'the same as used on the 120 ton ANFO event except that the construction tube around the MBA was eliminated as not necessary. The shot was fired on 6 October 1976 a short duration bright flash, a long, loud bang, and a large gray cloud was all that was seen from the distant observation point. The flash was somewhat disappointing to many observers who had never before seen an ANFO explosion; missing was the red orange roiling and boiling fireball sized with dense black smoke so familiar on TNT shots. "Did the ANFO charge fail to detonate properly?" they wondered during the fifteen seconds it took the blast to arrive at the observation station. The magnitude of the blast that was felt put to rest these momentary doubts, and a later survey of the test site indicated that, indeed, the charge went off properly. A large crater was seen and many targets responded to the blast to the point of severe structural damage. The ANFO fireball was characteristic of stoichiometric explosives that have no afterburning.
Airblast measurements along three different blast lines, radiating approximately 120° apart from GZ, and at about two dozen outer points in the test area indicate the propagation of a relatively symmetrical blast front; the data points scatter around the BRL prediction curve. A spread is normally experienced on large TNT shots. The scatter, where multiple data points are available, for the 100 ton TNT tangent sphere control shot of pre DICE THROW II, Event 1; is considerably larger than for the much larger DICE THROW ANFO shot. Even after more than a half dozen shots with 100 ton and 500 ton TNT tangent spheres, there still were two prediction curves for the event and the data fell below each of the predictions. That the data scatter and do not fall on the prediction curves is interesting but not surprising. The long history of explosion effects studies has demonstrated amply that on any one given shot, the data will show scatter around (hopefully!) some hydrodynamic code or empirically derived curve. The real explosion is not constrained by the niceties of ideal, theoretical ,conditions postulated in the prediction schemes.
On DICE THROW scatter between 2 and 2,000 psi is well within that usually found in field experiments. The scatter around the 1 psi level may be attributable to the influence of local wind and temperature variations at the long distances where the low blast pressures occur. At the 3,000 psi level, the scatter may result from the difficulties of gages following a high transient pressure in an air field perturbed by detonation products and thermally induced air instabilities, or this scatter may be true representations of the pressure field close in to the charge real non symmetries or anomalies. Although anomalies are not particularly discernible in the pressure distance, the pressure time records at several blast measuring stations and high speed photographs of the fireball and shock front do give evidence that some anomalies occurred.
The presence of these anomalies is disturbing even though they are less extensive and severe than those produced on the earlier employed block built TNT charges; no ready and conclusive explanations are available to account for them. Indeed, it may be that as stated earlier, there is evidence that most, if not all, condensed explosives produce anomalies such as jetting. If this is so, then the ANFO charge performance furthers this view, and it has to be lived with; c'est la vie. Or it may be that uneven fuel oil distribution and possible air pockets within the charge (resulting from inadequate filling of the inter bag spaces with loose ANFO) may lead to a sufficiently inhomogeneous explosive charge so that non symmetrical detonation occurs. Swisdak's measurements of fuel oil content made during charge construction shows average fuel oil percentages ranging from 4.96 to 7.02 in the layers, although the average for the whole charge is 6.12.
Additional in-homogeneities within the charge could be caused by density variations of the ANFO. Again, Swisdak's data indicates that on a layer to layer basis, theme were density differences (and that the average density for the whole charge was 0.914 g/cm3, a much higher value than normally encountered). Explosive diagnostic measurements by B. Hayes and R. Bost (Lawrence Livermore Laboratory) with rate sticks and time interval gages within the charge show that "while the explicit relationship for ANFO is not known, both the measured detonation velocity and pressure confirm there were density gradient regions within the stack. As a consequence, it is not unreasonable to expect a hydrodynamic instabilities to develop since the change in detonation velocity with respect to a change in density is like a factor of seven. This effect will lead to considerable internal turbulence which does not smooth out. More probably, cellular disturbances are generated festering multiple interactions which disrupt the smooth isentropic expansion of the detonation products".
Still another source of in-homogeneities within the charge may be the presence of the bags in which the ANFO is contained. The average weight of a bag is 0.54 lbs; this constitutes a little more than 1 percent of the total weight of a bag of ANFO. On the DICE THROW charge, this 1 percent translates into about 12,500 lbs of extraneous, non explosive bag material.
Another reason for the anomalies may be the rather rough outer contour of the charge with reentrant-like corners noted earlier. And still another reason could be the non simultaneous detonation of the seven boosters. Unfortunately, most of the probes for determining simultaneity did not function properly so no clue is available from this source. In short, blast anomalies were observed but their source or sources of origin are not evident.
Although in this section of the report much emphasis has been placed on the characteristics of the pressure distance curve as a legitimate criteria to evaluate ANFO performance, the other hydrodynamic parameters of blast waves have been used also as criterion. As reported by G. Teel (BRL), he measured blast arrival times, positive phase durations, positive phase impulses, horizontal dynamic pressures, and dynamic pressure impulses all compare with pre test predictions.. The predictions were based on the LLL developed equation of state for ANFO, AFWL HULL code calculations, and BRL data obtained from the Pre DICE THROW II, Event 2, 120 ton ANFO shot. The predicted inflection points in the duration and impulse distance curves are not as pronounced on the DICE THROW event as predicted; this may be because a clear demarcation between fireball and shockwave separation for an ANFO explosion is a they reduced or eliminated.
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