SCOPE Blast phenomena are dangerous to animals and man primarily because of the large variations in pressure which are induced by an explosion in soil, water, and air and because of the mass movement of material that surrounds the explosive at the time of detonation, be this earth, water, or air. In the case of the latter, blast produced winds of considerable magnitude can be involved. It is useful to categorize biological blast hazards under four headings, namely: 1. Primary blast effects which are those associated with the various patterns of pressure variation induced by an explosion and the interaction of the pressure pulse with structures around or near the biologic target; 2. Secondary blast effects which are those caused by the impact of penetrating and nonpenetrating missiles that are secondary to the blast; 3. Tertiary effects incorporating the consequences of physical displacement by blast-produced winds; and 4. Miscellaneous effects which are those involving ground shock and sharp accelerations imparted to a buried structure, dust whether airborne or arising from the walls of an above- or below-surface structure and high temperatures associated with compression, aerodynamic heating, dust and debris and blast-produced fires rather than thermal phenomena attributed to thermal radiation per se. OBJECTIVES Three main objectives have guided the laboratory and field investigations. The first has involved the desire to thoroughly and completely understand the primary, secondary, tertiary, and miscellaneous effects of blast on man. Secondly, elucidation was sought of the relative relation of blast hazards to those associated with other environmental alterations produced by a nuclear explosion, not the least of which concerns prompt ionizing and thermal radiation, residual induced and fallout radiation and fire storm. Thirdly, last research was influenced by the need and desire to support the practical needs of architects and engineers for biological data essential to the functional design of structures adequate for the complete protection of man. THE 1951-54 PERIOD FIELD WORK During the Upshot-Knothole test series in 1953 biological material was exposed on two occasions in a pair of "open" but instrumented long tubular underground structures, without doors, located about 1,500 feet from ground zero. Recovery of animals following the detonation of a nuclear device approximately 15 kilotons in explosive yield was accomplished and damage was assessed by routine pathological methods. Some mice were fatally injured by the pressure variations that occurred inside the structure which, in terms of peak pressure varied from about 7 to 25 p. s. i. (pounds per square inch). Of 44 trained dogs, restrained from being displaced by using custom-fit heavy harnesses, 15 exhibited significant lung hemorrhage and damage in others involved sinus hemorrhages, eardrum rupture, tearing of the lining of the bladder and spotty hemorrhages in other abdominal viscera. Too, ataxia, a staggering gait, was noted which evidenced some damage to the nervous system. Two anthropometric dummies exposed inside the structures were violently displaced by blast-produced winds. Mr. HOLIFIELD. Is this the effect of the shock or the blast on the animal organism? Dr. WHITE. Yes. These were open structures, Mr. Chairman, and the winds and pressure pulses were allowed to enter. This gives one the opportunity to create a pressure environment and winds which are realistic. Mr. HOLIFIELD. Without hurling the animal against the wall. Dr. WHITE. That is right. These animals were restrained deliberately because it was appreciated that there would be winds and we wanted to try and segregate the different blast effects and study them as independently as possible. Mr. HOLIFIELD. How far were they from point zero? Dr. WHITE. 1,500 feet. Mr. HOLIFIELD. What size was it? Dr. WHITE. 15 kilotons, approximately. Mr. HOLIFIELD. So it is reasonable to suppose that this effect could be extrapolated into the effect on human beings? Dr. WHITE. Well, possibly. I think we might discuss that later if you like. Mr. HOLIFIELD. All right. Dr. WHITE. It is significant that the underground structures were so designed and located as to structurally survive and shield the animals from ionizing and thermal effects. However, the internal environment, otherwise adequate, was hazardous because of blastassociated phenomena: For example, (1) blast winds measured in the center of the shelters created a dynamic pressure (Q) on one occasion as high as 3.0 pounds per square inch equivalent to a wind at sea level of almost 300 miles per hour, and (2) long duration (up to 1 second) overpressures complicated by reflections which resulted in higher peak pressure inside the structures than existed outside. Further, it was noted that severe damage to dogs was associated with the greater (12-25 pounds per square inch) and faster rising overpressures (>440 pounds per square inch per second), whereas minor damage involved lesser overpressures (7-13 pounds per square inch) and the slower-developing pressure (<440 pounds per square inch. per second). 1 This fact suggested that experimental animals blastwise might well survive primary blast damage in an "open" properly designed shelter even though the outside pressures were 100 pounds per square inch or greater, provided the rate of development of the pressure inside the structure could be controlled to rise slowly enough. 1 The symbol ">" means "greater than" while "<" means "less than." Such thinking stimulated activities in two directions; for example, (1) planning full-scale biological experiments from very low to very high pressures for the 1955 Teapot test series, and (2) attempting to design a laboratory pressure source capable of producing the overpressure-time patterns known to be associated with the detonations of nuclear and thermonuclear devices and to exist inside protective structures. Laboratory work: Laboratory investigations up to 1954 covered studies mostly related to the missile problem. The pathology of building debris was investigated and studies were organized to explore low-velocity missile effects, both penetrating and nonpenetrating in nature. From such studies it became obvious that full-scale missile information was needed to give a background for understanding secondary blast effects. No data covering the weight, size, were available. Fortunately, from the laboratory work came information which allowed a full-scale missile program to be planned for the 1955 test series. Missile traps using appropriate absorbers were fabricated and calibrated. The technique, if successful in the field, promised to yield quantitative missile information of considerable value. During the 1955 spring test series over 270 experimental animals ranging in size from the mouse to the dog, located inside 15 separate, instrumented structures comprising 6 different types of above- and below-ground construction, were exposed to the environmental variations associated with nuclear blast. Range of the several structures varied from 1,050 to 5,500 feet. The most severe alterations in the pressure environment inside the structures followed the detonation of a nuclear device the yield of which was about 50 percent greater than nominal. This weight of explosive produced a side-on ground pressure outside the most forward underground structure which was between twofold to threefold that estimated to exist near the epicenters of the near nominal yield explosions at Hiroshima and Nagasaki. Physically environmental pressures inside structures varied from 1.3 to 85.8 pounds per square inch and, depending on circumstances, were from about one-third to two times those existing outside the shelters. All animals were recovered after the detonation. In the forward underground structure tested "open" blast-produced fatalities were limited to mice, 1 guinea pig and 1 dog, the latter as a result of violent displacement caused by high velocity winds. Primary blast damage was observed in a few of the other large and small animals, but with the exception of ears and sinuses, was minimal or absent in the larger species. The overpressure patterns though much higher in peak pressure (up to 85.8 pounds per square inch) were less damaging to animals than the lower overpressures (25 pounds per square inch maximum) of the 1953 experiments, apparently because of changes in design which altered the configuration of entryways and the shape of the innermost compartments. In contrast, however, the dynamic_overpressures near the entryways (Q equaled 12.25 and 12.7 pounds per square inch maximum) proved potentially more damaging. Of interest to those who contemplate the feasibility of adequate protective construction other observations made during the 1955 field experiment are quite significant as listed below. 1. Dogs, except for rupture of one eardrum, were recovered from a reinforced bathroom and simple leanto shelter located in completely destroyed houses 4,700 feet from ground zero. 2. Rats suffering no blast damage were recovered from a "closed" underground structurally adequate shelter 1,050 feet from ground zero. 3. Even the "open" underground structure at 1,050 feet from ground zero was adequate structurally, functioned fairly well in protecting larger animals from primary blast effects, but was inadequate to avoid tertiary blast effects (displacement) even to strongly tethered dogs. 4. Thermal effects not due to thermal radiation, but probably to aerodynamic heating, compression temperatures, hot gases and dust carried into the forward "open" structures were observed. 5. A few animals from the shelters located at 1,050 feet which were not sacrified in the blast studies were later afflicted with radiation sickness that proved fatal. This was contrary to the 1953 experience though biologic material was exposed at greater range. Thus, the 1955 forward structures were not adequate for radiation protection at "close" range, though they might well have been had they been placed deeper in the ground. It will now be clearly obvious to the committee that the provision of protective structures, the internal environment of which is safe for humans, requires the continuous and close cooperation of a group of knowledgeable individuals, including physicians and biologists who are informed in biological blast effects, radiation and thermal effects; radiation physicists who understand nuclear detonations in relation to yield, distance and shielding; instrumentation engineers whose efforts are necessary to monitor the environmental variations needed to aid proper interpretation of the biological data; and the architect and engineer who must develop adequate design from a synthesis of the best available information, both physical and biological. Likewise, it certainly seems clear that considerable progress has been made in the past in integrating the efforts of scientists trained in diverse fields. Since there is yet much to learn, a simple fact deserves strong emphasis; namely, physical and biological research in the field of weapons effects must continue both in the laboratory-as will be further supported by later remarks and full-scale in the field if man is to master the environmental problems created by the advent of nuclear detonations and realize the maximum in protection at reasonable cost. SECONDARY MISSILES In 1955 some secondary missile studies were done and the missiletrapping technique mentioned earlier was quite successfully employed in the Teapot Operation and blast energized missiles were captured inside houses and in the open. Over 2,600 missiles were recovered, weighed and their impact velocities determined from calibration data and measurements of their depth of penetration in the absorber-styro foam plastic and cork. Fragments of window glass in houses located at 4,700, 5,400, and 10,500 feet from ground zero ranged in velocity from about 70 to 370 feet per second and in weight from near 0.01 to 11 grams. All field data were completely analyzed and a theory, applicable at least to the lower regions of overpressure, was developed which if verified will allow approximate missile velocities to be computed given information concerning distance and the magnitude of a detonation. Missiles LABORATORY RESEARCH Following the 1955 test series laboratory experiments were arranged to reveal the probabilities of glass fragments entering the abdominal cavity of a dog as function of the missile mass and velocity. For fragments near 0.04 grams in weight penetration velocities ranged from near 300 to 1,000 feet per second while for 3-gram particles penetration velocities ranged from only 160 to 400 feet per second. With these data, assessment of the biological implications of the field data was undertaken. One surprising and interesting outcome of this study was the fact that hazard from flying glass appeared to be greater at a range of 5,500 feet-4 pounds per square inch-than it was at 4,700 feet-5 pounds per square inch-for an explosive yield of about 1.5 nominal. This was true because glass fragments at both 4 and 5 pounds per square inch had about the same mean velocity, but the average mass of missiles was greater at 5,500 feet-4 pounds per square inch-than at 4,700 feet-5 pounds per square inch. The consequence of the mass difference was to increase the probability of a glass fragment penetrating a biological target. Work on nonpenetrating missiles was continued in the laboratory covering missile weights from near 0.8 down to 0.2 of a pound impacted against the thoracic cavity of experimental animals. Surprisingly enough, and particularly for the lighter missiles traveling at higher velocities, lung lesions closely resembling those of blast were noted in both lungs even though the missile impact was unilateral. PRESSURIZATION SOURCE Design of a pressurization source for laboratory blast studies was completed. With funds provided by the Division of Biology and Medicine of the AEC a modified blowdown wind tunnel was installed and instrumented. The blast facilities was and is located on South Sandia Base near the mountains and evaluation of the performance characteristics and the biological potential of the source were undertaken simultaneously. The blast tube proved highly successful, there being no difficulty in creating a variety of pressure-time phenomena involving peak pressures over 200 pounds per square inch and overpressures as long as 20 seconds. The tub was operated also in physical testing for Sandia Corp. personnel who wished to evaluate the pressure tolerance of rubberized and plastic sheeting to be used in field tests planned for 1957. TERTLARY BLAST EXPERIMENTS (IMPACT LOADING) Exploratory experiments with mice, rats, guinea pigs, and rabbits were undertaken to determine their tolerance to dynamic decelerative |