Operation Ivy, Project 6.1 - Air Shock Pressure-Time VS Distance, Pacific Proving Grounds, November 1952 (Deleted)

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Pacific Proving Grounds - Joint Task Force 132 This is an extract of WT-602, which RESTRICTED DATA as of this date. Extract version prepared for: DEFENSE NUCLEAR AGENCY Approved for public release;

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This report has had classified material removed in order to make the information available on an unclassified, open publication basis, to any interested parties. This effort to declassify this report has been accomplished specifically to support the Department of Defense Nuclear Test Personnel Review (NTPR) Program. The objective is to facilitate studies of the low levels of radiation received by some individuals during the atmospheric nuclear test program by making as much information as possible available to all interested parties. The mate'rialwhich has been deleted is all currently classified as Restricted Data or Formerly Restricted Data under the provision of the Atomic Energy Act of 1954, (as amended) or is National Security Information. This report has been reproduced directly from available copies of the original material. The locations from which material has been deleted is generally obvious by the spacings and "holes" in the text.. Thus the context of the material deleted is identified to assist the reader in the determination of whether the deleted information is germane to his study. It is the belief of the individuals who have participated in preparing this report by deleting the classified material and of the Defense Nuclear Agency that the report accurately portrays the contents of the original and that the deleted material is of little or no significance to studies into the amounts or types of radiation received by any individuals during the atmospheric nuclear test program.

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Air-pressure measurements on Operation Ivy were unique in two respects: Detonation of the first “superbomb” on Mike shot presented an opportunity to verify experimentally the applicability of the WS scaling law at larger yields than ever before; and on King shot it was possible to observe simultaneously the development of the shock waveform over land and over Measurements on Mike shot were successful, with the exception that no overpressure data were obtained at pressure levels greater than 20 psi. It is recommended that efforts to repeat these measurements be made at the earliest opportunity. Measurements on King shot were quite successful in that it was found that the waveform over water was nearly ideal, whereas that over land obviously was subject to some deterioration as a result of the thermal effect and Analysis of the results made possible several significant conclusions, the most important of which were 1. The scaling law is apparently valid for radiochemical (RC) yields as great as 10 Mt. 2. Overpressures from Mike shot are evidently in agreement with the assumption that the ! ! overpressures to be expected from a yield, W, burst at the surface of a perfect reflector, are the same as would be observed from a yield of 2W, burst in free air. 3. Agreement of the results from both Mike and King shots with those predicted from the height-of-burst chart published in TM 23-200 justifies extension of this chart to yields of the order of 500 Kt. The correction applied in this chart for thermal effects also appears valid. Appendix A to this report describes semiquantitative measurements of shock symmetry, and from all indications the shock wave was symmetrical along the two radii chosen for these

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Shock-pressure measurement8 for Operation Ivy were planned by representatives of JDivision of the Los Alamos Scientific Laboratory and the Weapons Effects Department (5110) of Sandla Corporation. The author wishes to express his appreciation for the fine cooperation among the participating agencies and the personnel and contractors of the Pacific Proving Installation of the measuring equipment and field measurements were ably executed by personnel of the Pacific Proving Ground Division (5233) of the Field Test Organization of the Sandia Corporation. A list of all participating personnel is presented as Appendix B to this The author wishes to acknowledge also the assistance of Miss Sally Langenstein in preparing this manuscript for issuance.

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2 OBJECTIVE AND SCOPE ...s.... 4 CONFIGURATION AND INSTRUMENTATION OF THE BUST LINE 5.1 Performance of Instrumentation and Recording System 6 RESULTS SCALED ‘l-t3 1 KT AT SEA LEVEL . APPEND= A SHOCK SYMMETRY MEASUREMENTS 2 Wiancb Gauges in Ground Baffle .... 2 Station Noah (Lower Right), Showin#Bogon in Background 5 Goal-post Towers; Side-on Baffle and Pitot Static Tube at Right 6 Blast Linen for King Shot ........

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Pressure-Time Curves (Mike Shot) for Stations on Engebi, Muzin, Pressure-Time Curves (Mike Shot) for Stations on Aomon, Runit, Positive-phase Duration vs Distance from Ground Zero Peak Negative Pressure vs Distance from Ground Zero Negative-phase Duration vs Distance from Ground Zero Time of Arrival vs Horizontal Distance from Ground Zero Peak Overpressure vs Horizontal Distance from Ground Zero Positive-phase Duration vs Horizontal Distance from Ground Positive Impulse vs Horizontal Distance from Ground Zero Peak Negative Pressure vs Horizontal Distance from Ground Negative-phase Duration vs Horizontal Distance from Ground Negative Impulse vs Horizontal Distance from Ground Zero Time of Arrival of the Second Shock vs Horizontal Distance from Peak Overpressure in the Second Shock vs Horizontal Distance from Time of Arrival vs Distance from Ground Zero (Mike Shot); Data Peak Overpressure vs Distance from Ground Zero (Mike Shot); Data Data Reduced to 1 Kt (RC) at Sea Level ...... Positive Impulse vs Distance from Ground Zero (Mike Shot); Data

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Time of Arrival vs Slant Range (King Shot); Data Reduced Height Burst vs from Ground for Various Overpressures on Surface [Scaled 1 Kt at Sea Locations of Measuring Stations for Blast Line on Mike Shot . Locations of Measuring Stations for Blast Lines on King Shot . Elevations of Footings for Stations over Water Above Mean Low Results of King Shot (Nov. 16, 1952) ..... Data on Second Shock (King Shot) ...... Characteristics of Ivy Shots ....... Results of Mike Shot Reduced to 1 Kt (RC) at Sea Level . . Results of King Shot Reduced to 1 Kt (RC) at Sea Level . . Locations of Gauges ........

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Full-scale tests of atomic weapons at the AEC Pacific Proving Grounds on Eniwetok Atoll and the continental test site at the Nevada Proving Grounds have yielded valuable information”’ on the pressure-Ume-distance pattern for shock waves from air and tower bursts of weapons of various yields. Overpressures measured at or near the ground on three test series, Operations Greenhouse, Buster-Jangle, and Tumbler-Snapper, have been used to construct a height-of-burst chart based entirely on experimental data. Data on experimentally measured overpressures from nuclear bursts, used in conjunction with those from analogous forts in this direction are planned with the ultimate objective of gaining an understanding of blast-wave propagation that will take into account factors such as the effects of thermal radiation, mechanical disturbance of the surface soil, and variations in terrain. 2 OBJECTIVE AND SCOPE The two shots of Operation Ivy presented an unparalleled opportunity to measure blast pressures and study the propagation of shock waves under conditions such that thermal and mechanical effects were essentially minimized. Mike shot was the first experimental burst of a “superbomb.” Since it was only the second surface burst (the first was the Jangle Sugar shot) of a nuclear weapon, experimental data from this burst would have been expected to aid in fixing the zero intercepts of the experimental height-of-burst chart for nuclear weapons. The overpressures of interest occurred at comparatively great radial distances from ground zero, and the shock wave traveled a large percentage of its path over water to reach the majority of the measuring stations on the blast line, the locations of which were dictated by the geographical configuration of the island chain. Measurements on King shot were unique in that two blast lines were used, one entirely over water and the other predominantly over land. The only previous measurements of shock overpressures over water were those made on Bikini shot Able. The land line was intended to provide useful data for comparison not only with data from the blast line over water on King shot but with previously compiled blast data on shots at the Nevada Proving Grounds. It was hoped also that the results of these tests would provide supplementary information on optimum heights of burst. Ordinarily, thermal effects from a surface burst over either land or water would be expected to be negligible because of the glancing angles of incidence. As a result of the size and thermal pulse duration of the fireball from a superbomb such as was used on Mike ever, some thermal energy might be incident upon the surface in the area in which cursor Is usually observed, causing a slight thermal effect upon the shock wave. Thus it was believed that since the yield of Mike shot was considerably larger than that of

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any previous nuclear explosion, any attenuation of pressure (as compared with that predicted) or any appreciable deviation of the observed pressure-time-distance curve from the “ideal” could possibly be attributed to phenomena arising out of the size of the explosion. Effetcta of ambient pressure and temperature gradiente, such aa are characteristic of the upper atmosphere of the earth, upon a passing shock wave are virtudiy unknown, After the shock wave has degenerated into a ~~~undwave, its path may of course be calculated. Any existent theories regarding the effects Of these temperature and pressure gradients on shock mation doe8 make poesible some qualitative deducUons’~lo about the possible distortion of a epherical 8hock wave in a nonhomogeneous atmosphere which might explain a decreaee in peak overprescrure as measured at ground level, an attenuation which could conceivably become increaeingly effective at greater dhtMCe8 from ground zero. Since it ia known that Water ie nearly an ideal reflecting Burface, it was predicted that overpressures meaeured on the blast line over Water On King ahot would be nearer the ideal or estimated overpreesures than thoee mea8ured on the land blast line. Not only doe8 water reflect a much greater percentage of the thermal energy incident upon it, but, in addition, any thermal energy abeorbed by water t8 abeorbed not juti in the firet fraction of an inch at the surface but over the entire path length of the refracted ray. As contrasted with observed behavior over land blast lines, one would expect to find no evidence, on bursts over a water surface, of precureor formation, ****i*the thermal-mechanical effect in which the surface layer of soil ie heated to the point of exploding or forming Cloud8 Of dust which move in the path of the rhock wave. It would be virtually impO88ible to heat the huge ma88 of water involved to the vaporizing point under the condition8 of this test. 1 Strictly speaking, the land blast line used on King ehot differed somewhat in configuration from tholre used on similar teeta at the Nevada Proving Grounds. Because it wa8 necessary to place the measuring etationa at different azimuth8 from the reference line paesing through ground zero and because of the &ape of the island on which 8tatiOn8 were placed, Borne water wa8 interspersed among the land areas; thue the paths traversed by the shock wave in reaching the varioue etations had different ratio8 of land to Water. Neverthelees it wa8 believed that conditions were similar enough to thoee in Nevada to warrant valid conclueions regarding the effect8 of different type8 of terrain on blast-wave propagation. It wae hoped that comparison of meaeuremente on the land blast line With thoee made at correeponding distances over water would give some indication of the degree to which preesuree were attenuated as the shock wave passed over land areas and would 8erve as a eemiquantitative meaeure of the deterioration of the preseure-time curves from the ideal waveforms as a reeult of thermal and terrain effects. Inasmuch aa the scaled height of burst on King shot waa low -178 ft-the results of these measurements are not particularly 8ignifiCaIit so far as eupplying additional point8 for the experimental height-of-buret chart ir concerned. Actually it would have been preferable to have made thie burst at a greater height, i.e., a acaled height nearer the “bmeee” of the height-ofburst chart, had data on height of burst been a primary objective. Requirement8 for other measurements, however, necessitated the limitation on burst height. The unprecedented 8ize of the burrrt and the inherent uncertainty in predicting the yield posed come new problems in estimating blast overpreesures and associated thermal effect8 from Mke 8hOt. Since it wa8 to be a surface buret over Water, it was felt that a reflection factor of 2 could eafely be a8eumed, Le., that the bla8t wave would take the form of a hemisphere having peak pressures, waveform8, and radii equivalent to thoee of a yield of twice the eize in free air. The set ranges to be used far the pressure gauges, and consequently their locations, were directly dependent upon the anticipated overpreseuree; So it was necessary to formulate a

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more or less arbitrary method for predicting these overpressures. Because it was fairly certaln that the yield of Mike shot would be at least 5 Mt, or the equivalent of a burst of 10 Mt in foee air, a pressure-distance curve for 10 Mt, scaled directly from Greenhouse George and Easy shots,” seemed to be a feasible starting point. This lo-Mt curve from Greenhouse George and Easy shots is by no means a free-air curve. In fact, because of the comparatively low burst heights of these two shots, it might more properly have been considered as representative of surface burst conditions. Consequently, when allowance was made for variations in yield and for indeterminate factors causing variation in shock overpressure at great ciistances, this method of prognostication seemed as valid as any. Prediction of overpressures on King shot was less uncertain, since the anticipated yield (500 Et) was more nearly of the order of previously fired weapons. Not only could the yield be estimated more accurately, but set ranges for the gauges in the overpressure region of interest were derived from a pressure-distance curve scaled from experimental data on Greenhouse tower shots.15 A factor of 20 per cent was added as a safety factor. 4 CONFIGURATION AND INSTRUMENTATION OF THE BLAST LINE The magnitude of the anticipated yield from Mike shot made it mandatory that pressuremeasuring stations be placed at considerably greater distances from ground zero than on earlier tests at Eniwetok and the Nevada Proving Grounds (Table 1). Predicted overpressures at the eleven station locations (Fig. 1) ranged from a maximum of approximately 320 psi to a minimum of 0.8 psi, and spacing was such that the predicted overpressure at each station was !’ approldmately half that at the preceding station. Actually, factors such as suitable island locations and existing recording shelters had to be considered in choosing these locations, making it necessary in some instances to deviate slightly from the basic plan. One station was on a man-made island (Noah) between Bogon and Engebi. As pointed out earlier, the crescentshaped configuration of the island chain made it impossible to align ail stations of the blast line on a …