Documentary (1954) 39 minutes ~ Color
The United States Department of Energy, in cooperation with the Department of Defense, has declassified a series of historical films on the nuclear weapons program.
This documentary deals with the Operation Castle, a series of high-energy (high-yield) hydrogen / nuclear tests by Joint Task Force SEVEN (JTF-7) at Bikini Atoll beginning in March 1954. It followed Operation Upshot-Knothole and preceded Operation Teapot.
Conducted as a joint venture between the Atomic Energy Commission (AEC) and the Department of Defense (DoD), the ultimate objective of the operation was to test designs for an aircraft-deliverable thermonuclear weapon.
Operation Castle was considered by government officials to be a success as it proved the feasibility of deployable "dry fuel" designs for thermonuclear weapons. There were technical difficulties with some of the tests: one device had a yield much lower than its predicted yield (a "fizzle"), while two other devices detonated with over twice their predicted yields. One test in particular, Castle Bravo, resulted in extensive radiological contamination of nearby islands (including inhabitants and U.S. soldiers stationed there), as well as a nearby Japanese fishing boat (Daigo Fukuryū Maru), resulting in one direct fatality and continued health problems for many of those exposed. Public reaction to the tests and an awareness of the long-range effects of nuclear fallout has been attributed as being part of the motivation for the Partial Test Ban Treaty of 1963.
The United States Department of Energy, in cooperation with the Department of Defense, has declassified a series of historical films on the nuclear weapons program.
This documentary deals with the Operation Castle, a series of high-energy (high-yield) hydrogen / nuclear tests by Joint Task Force SEVEN (JTF-7) at Bikini Atoll beginning in March 1954. It followed Operation Upshot-Knothole and preceded Operation Teapot.
Conducted as a joint venture between the Atomic Energy Commission (AEC) and the Department of Defense (DoD), the ultimate objective of the operation was to test designs for an aircraft-deliverable thermonuclear weapon.
Operation Castle was considered by government officials to be a success as it proved the feasibility of deployable "dry fuel" designs for thermonuclear weapons. There were technical difficulties with some of the tests: one device had a yield much lower than its predicted yield (a "fizzle"), while two other devices detonated with over twice their predicted yields. One test in particular, Castle Bravo, resulted in extensive radiological contamination of nearby islands (including inhabitants and U.S. soldiers stationed there), as well as a nearby Japanese fishing boat (Daigo Fukuryū Maru), resulting in one direct fatality and continued health problems for many of those exposed. Public reaction to the tests and an awareness of the long-range effects of nuclear fallout has been attributed as being part of the motivation for the Partial Test Ban Treaty of 1963.
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Short filmTranscript
01:00One March, 1954, seventy miles from the first shot of Operation Castle, a device with one
01:23thousand times the energy of the bomb that shattered Hiroshima, exceeding the power of
01:28that bomb as vastly as it exceeded the greatest high-explosive giants of World War II.
01:34Multi-megaton weapons are here, stockpile items as of today, with potentialities that
01:40compel revision of previous military concepts.
01:44But without full knowledge of those potentialities, intelligent revision is impossible.
01:49To gain such knowledge, the Armed Forces Special Weapons Project conducted extensive military
01:54effects tests for the three services during Castle.
01:58The data obtained will serve as factual tools to shape our strategic and tactical planning
02:03to warfare's new dimensions, a transition which will take us from the familiar ground
02:08of low-yield capabilities into an era of new problems as well as new power.
02:16Castle was a two-atoll operation because the program was too big and the devices too powerful
02:22for convenient staging at a single atoll as in the past.
02:26Five of the six Castle shots were fired at Bikini Atoll, two near Namu Island, two on
02:34barges in the north side of the lagoon, and one shot down on Inanman Island.
02:40At any Wetok Atoll some 200 miles to the west, only one shot was fired, number six, on a
02:46barge in the old Ivy Mike crater.
02:51Occupation space in the Pacific Proving Grounds is scanty in the form of small islands and
02:55many of Castle's projects were handicapped by this fact.
02:59For one thing, it was not practical in most cases to lay out instrument lines involving
03:04runs over dry land alone for any sizable distances.
03:09It should also be remembered that all Castle shots, like Ivy Mike, were surface bursts.
03:14Two of them fired in ground surface cabs and the other four fired on barges.
03:20We therefore do not as yet have any empirical data on effects of multi-megaton air bursts.
03:27Looking now at the data we did obtain, we may first consider the nuclear radiation aspect.
03:36Initial gamma measurements on this operation employed orthodox techniques with chemical
03:40and film dosimeters and scintillation detectors at a number of island and reef stations.
03:46Recent studies confirmed Ivy Mike's indications that initial gamma from a high-yield device
03:51differs considerably in delivery timing from that of a weapon in the kiloton range.
03:57Roughly 50 percent of the initial gamma dose from kiloton weapons arrives within the first
04:02half second after the burst, allowing no time for target personnel to take cover.
04:08With a multi-megaton bomb, however, some 80 or 90 percent of initial gamma will not arrive
04:13on target until after arrival of the shock front.
04:17At fair distances, this could provide a number of seconds for target personnel to take such
04:22cover as may be available.
04:24This timing differential becomes of academic interest only in view of another Castle finding.
04:30It developed that initial gamma dosage at ranges of concern reached only about one-tenth
04:35of the predicted level.
04:38This means that initial gamma from the big weapons drops off to military unimportance
04:42at ranges at which blast and thermal will still cause almost 100 percent casualties
04:47outside of heavy bunkers.
04:51Measurement of neutron spectrum and flux were made indirectly by study of nuclear changes
04:55in threshold detector elements exposed on sample mounts at various distances.
05:00It developed that the neutron flux, while heavy, attenuated so rapidly with distance
05:05that in comparison to other effects, it too may be considered to have little military
05:10value.
05:11We come next to a field in which the radiological effects of megaton surface bursts are far
05:16from negligible, are, in fact, of profound importance.
05:25Ever since the one kiloton surface burst of Jangle in Nevada, we have recognized that
05:30such bursts may produce widespread residual contamination of significant intensity.
05:36Limited investigation on Ivy gave us scanty data, so our biggest Castle project was in
05:41this area.
05:44Further knowledge was a military necessity as well as grimly relevant to the defense
05:48of American cities.
05:50It is worth emphasis that only surface or subsurface bursts produce important fallout,
05:55and for the moment we will consider only land surface bursts reasonably approximated by
06:00the first Castle shot.
06:02The seawater involved in this fireball did not significantly alter the radiation levels
06:07or distribution of local fallout from what would be expected of a land surface burst.
06:19Fallout history begins with the scores of millions of tons of earth vaporized by such
06:24a detonation.
06:25This material, which rises with the fireball, has neither original nor induced radioactivity
06:30of any consequence, but during condensation, it traps radioactive bomb products significant
06:37for intense gamma emission.
06:41In the first few minutes, the visible cloud will reach from 60 to 100,000 feet or more
06:46for multi-megaton bursts with a stem over five miles in diameter.
06:51Fallout of the radioactive particles inside and below the visible structure now begin
06:56through the operation of gravity, rainout, convection, and other mechanisms.
07:01The active airborne particles move on downwind, causing significant fallout for a period of
07:06ten hours or more.
07:08The settling dust reaches ground in a pattern which, while naturally quite variable, is
07:13reasonably represented as a long leaf shape.
07:17Starting back at the time of burst again, it is important to note that while the visible
07:21cloud will move with cloud height winds, the fallout particles will settle through lower
07:26winds of possibly conflicting directions at various heights.
07:30Orientation of the ground fallout pattern is determined by a resultant wind vector which
07:34is an average of all winds from ground to cloud height.
07:39Therefore, the fallout pattern may take an entirely different path from that of the visible
07:43cloud.
07:44Changes in the average wind vector as the falling dust moves across country can cause
07:49major distortion of the fallout pattern.
07:53The most important collectors of castle fallout data were of two main types.
07:58Total collectors, such as the gum paper trays and funnels of several sizes, intermittent
08:04collectors, such as belt samplers, and the rotating drums, both of which exposed collection
08:10trays at timed intervals.
08:14Such instrumentation in varying combinations was placed on a number of islands at Bikini
08:18and more distant atolls.
08:21Since this constituted scanty coverage, 26 instrumented stations were located on anchored
08:26rafts a few miles apart throughout the Bikini Lagoon.
08:31Losses of this type of equipment were heavy on the unexpectedly powerful first shot, which
08:35only 12 of the 26 stations survived.
08:39All those within a 10-mile radius were overturned.
08:42For the final shot, number six in the Old Mike Crater, a similar grid of 32 of these
08:47raft stations was employed to document the Eniwetok Lagoon.
08:52To extend the coverage outside the lagoons, original planning called for the use of floating
08:56danbuys in concentric rings at 30 to 100 miles from ground zero.
09:01They were instrumented with funnel and sticky paper collectors, plus small radio transmitters
09:07to assist in locating them after each shot.
09:10Success of the danbuy project was limited by difficulty of recovery due to high seas
09:15and change of shot schedule.
09:19On the last two shots, open ocean fallout was documented by a new technique of water
09:24survey and sampling methods.
09:26One-gallon water samples were taken at a number of stations in contaminated areas at various
09:31depths from the surface to several hundred meters down.
09:34Further data were obtained from surface and underwater gamma meters, either lowered straight
09:38down for determination of radiation versus depth, or towed behind ships for contour surveys.
09:46Vertical profile data from the meters and from analysis of the water samples indicated
09:50that the radioactive debris mixes rapidly and uniformly throughout the surface layer
09:55down to the thermocline at around 120 meters.
09:59This vertical mixing information made it possible to estimate total fallout intensity at a given
10:04ocean site by measuring the activity of a single sample of surface water from that spot.
10:10All computations were correlated with the data from buoy and raft stations, ships, and
10:15island weather stations.
10:18In fact, emphasis on this open ocean survey resulted directly from the unforeseen fallout
10:23from shot one on some populated distant island, a weather station on one of them.
10:29These islands, functioning as accidental total fallout collectors, gave us our first real
10:33clues to the vast area affected by contamination from a high-yield surface burst.
10:39Within a few hours after that shot, a powdery snow-like fallout began on Eilinganai and
10:44Rongelap Atolls, then on Rongerik, and finally on Uterik.
10:49By 8 plus 78 hours, 229 Marshall Islanders and 28 American service personnel were evacuated
10:56to Kwajalein for survey and treatment.
11:00It was tentatively estimated that the total gamma dose may have approached 70 roentgens
11:04for the people on Eilinganai, 175 roentgens for some on southern Rongelap, 80 on Rongerik,
11:12and only 14 on Uterik.
11:15The dosages in these outer fringe areas did not appear to reach levels of immediate combat
11:20significance, nor did any severely incapacitating effects show up during treatment or observation
11:25on Kwajalein in excess of 40 days.
11:28A majority of those receiving the heaviest radiation reported some transient nausea on
11:33the first or second day, and there was a small incidence of gastrointestinal disturbances
11:38of short duration.
11:40Some loss of hair was a frequent symptom.
11:44Most of the Marshallese in this category developed multiple skin lesions, usually not severe,
11:49predominantly on the scalp, back of the neck, and feet.
11:53Only a few developed mild secondary infections during healing.
11:57The lesions appeared to be directly related to the amount of fallout deposited on the
12:01skin rather than to the generalized whole body radiation.
12:06It appeared that even one layer of clothing afforded substantial skin protection, suggesting
12:11that the beta energies of the fallout material were relatively low.
12:16Significant blood changes were found in patients from the heavier fallout areas, including
12:20pronounced lowering of both platelet and leukocyte count, which would reduce the body's ability
12:25to combat hemorrhage or infection.
12:28Returns to normal were not complete after six weeks.
12:33Recent surveys of the fallout islands, together with autopsies of domestic animals, have indicated
12:38that intake of contaminants through the lungs in cases of this sort will be negligible compared
12:43to the external radiation dose, and will probably be negligible in comparison with the intake
12:48with food and water unless these supplies are protected.
12:52Hmm, possibly some new Air Force equipment.
13:00We can now take another look at the fallout material that came down on Rongelap.
13:05The small portion of the cloud material destined for southern Rongelap, where the natives lived,
13:10was emitting gamma at the rate of about 130 roentgens per hour at H plus one, or one hour
13:16after the shock.
13:18Decaying with time as it traveled another four hours downwind, the material was emitting
13:22perhaps 20 roentgens per hour, and still decaying when it grounded at Rongelap, 100 miles from
13:28zero.
13:29By evacuation time at H plus 50 hours, the maximum accumulated dose at that point was
13:35around 175 roentgens, a mild sickness dose for less than 50 percent of exposed personnel.
13:42The activity increased rapidly toward the uninhabited north, however, and in 10 miles
13:48reached a mean lethal level for exposed humans on the order of 450 roentgens.
13:54On the atoll's upper islands, this H plus five to H plus 50 hour dosage ran from possibly
14:001,500 to 3,000 roentgens, well above the lethal human dose.
14:06We can plot a line of peak observed readings, but considering the average wind vector, the
14:11center line of the fallout was apparently still farther north.
14:15Mapping from a few established values, we can at least approximate the minimum fallout
14:20pattern.
14:21The contours are selected to represent accumulated dosage from arrival time to H plus 50 hours.
14:29The 450 roentgen mean lethal dose appears to have enclosed an area exceeding 7,000 statute
14:35square miles, an area some 250 miles long, an area which on land could blanket large
14:41segments of population.
14:44And note that inside this 450 roentgen border, the dose accumulated by H plus 50 hours climbs
14:50quickly to 100 percent lethal for exposed humans.
14:56On the defensive side, it should be remembered that the gamma intensity of fallout at H plus
15:01seven hours has decayed to one-tenth what it was at H plus one, and by H plus 48 hours,
15:08it is only one one-hundredth of the H plus one value.
15:12Additionally, the shelter of a frame dwelling will cut the dose rate to one-half of the
15:17outside rate, and the possession in the basement would reduce it to a tenth.
15:22Attenuations in excess of 1,000 can be gained in basements or middle stories of multistory
15:28buildings or in simple shelters with at least three feet of earth overhead.
15:33In general, however, it should be recognized that the best average shelter available in
15:37cities will cut dose rates only to a level between one-quarter and one-eighth of the
15:42full dose.
15:44Accurate evacuation when fallout begins is not too promising, both because of sheer physical
15:49difficulties and because of probable lack of data as to safe and dangerous areas.
15:54The most practical solution appears to be the widespread use of available shelter for
15:58two to four days before attempting mass evacuation.
16:04We will consider now a phase of the fallout studies which was of major importance to naval
16:09operations.
16:10This was an experiment with a pair of modified Liberty ships to determine the effectiveness
16:15of a saltwater spray system designed to wash contamination from weather surfaces as a ship
16:20progresses through a heavy fallout area.
16:23Additional studies were made of the effectiveness of decks and other ship structures for shielding
16:27interior locations and of the entry of airborne contaminants through ventilation and boiler
16:32air systems.
16:36The Liberty ships designated as vehicles for these and related studies were YAG-39, fully
16:41equipped with a washdown system, and YAG-40 with no washdown.
16:48Each ship's modifications included a representative flight deck, two gun installations, and an
16:54F4U aircraft carried aft.
16:58Both ships were heavily instrumented to measure gamma dose rate and total dosage.
17:03On each of the four shots participated in, an average of 400 detector channels was in
17:08operation, transmitting data below decks to the recording rooms.
17:13Airborne and weather deck beta distribution studies were also accomplished.
17:17The ships were equipped with drone control systems for remote operation of engines, steering,
17:22and the washdown apparatus of YAG-39.
17:26During the first two shots, both ships were unmanned in their maneuvers into the fallout
17:30region and were controlled from a P2V-5 aircraft with a secondary control center aboard the
17:36carrier by ROCO.
17:39During the remaining shots on which the project was active, shots four and five, YAG-39 was
17:45manned by a small crew which controlled the ship from a well-shielded compartment.
17:50This party in turn exercised radio control of the nearby YAG-40.
17:54During these exposures to heavy fallout, the flow rate of YAG-39's washdown was approximately
18:002,000 gallons per minute.
18:03Radiation levels below decks remained low enough to permit the crew to take the ship
18:06back to Eniwetok Lagoon after each shot.
18:09YAG-40, unprotected by washdown, could not be manned for the return trip.
18:16After each test period, radio control was dropped and the ship was towed back to Eniwetok.
18:23At Eniwetok, the F4U airplanes were removed to shore for further study and cleaning operations.
18:31Comparisons of radiation data on the two YAGs led to an estimate that washdown effectiveness
18:36on ships and their exposed aircraft will average about 95 percent based on the dose rate.
18:42Shielding studies indicated that weather deck gamma levels will be attenuated by distance
18:46and structural shielding to a fraction estimated at two-tenths in compartments close to the
18:51weather surfaces and approximately one-one-thousandth in interior compartments below armored decks.
18:59Boiler air system contamination appeared to be minor, and the mushroom heads on ventilation
19:03intakes reduced the airborne gamma contamination below decks by 99 percent.
19:08Stopping the fans made no apparent difference.
19:13Some shot five figures will give a rough idea of the levels of intensity involved in the
19:17project.
19:18By ten hours after the shot, measured areas on YAG-39's decks had, in spite of the washdown,
19:25accumulated an average total dose of some 40 roentgens.
19:29YAG-40's cumulative dose was 400 roentgens, approaching a mean lethal dose.
19:34Fifteen hours after the shot, random sampling on YAG-40's decks still showed a dangerous
19:4025 roentgens per hour, while on YAG-39 it was only two roentgens, a negligible rate
19:46by comparison.
19:49The weight of the spray assembly can be minor, even for fighting ships, and the entire head
19:53of water can usually be handled by a ship's normal pump.
19:57It is concluded that the washdown system can serve the purpose for which it was designed,
20:02to hold gamma radiation below decks of combat ships within tolerable levels in such fallout
20:07areas, and to hold weather surface contamination to levels permitting immediate topside emergency
20:13action after leaving the fallout.
20:22No thermal military effects tests were scheduled on CASL, but measurements were made of the
20:27thermal spectrum, power versus time, and total energy.
20:32Power versus time graphs show that the main thermal pulse of a low-yield weapon arrives
20:37and is essentially completed inside of a couple of seconds.
20:41Of a high-yield weapon, it takes some three seconds to reach the peak of the main pulse,
20:46which has a comparatively long duration.
20:48Therefore, quick dodging even into light cover would allow target personnel to escape most
20:54of the thermal effect.
20:56This slower delivery time also requires a scaling up of low-yield thermal damage criteria.
21:02Equivalent damage from a one-megaton bomb requires twice as many calories per square
21:06centimeter.
21:07The needed increase approaches 350 percent for 15 megatons, and probably still more for
21:13higher yield.
21:15But even with these handicaps, the thermal destructive range of megaton weapons is huge.
21:22Against exposed troops wearing four-layer winter uniform, an optimum burst height with
21:27a 100-kiloton bomb can produce 50 percent casualties out to nearly two miles, involving
21:33an area of 10 square miles.
21:36With the same 25-mile visibility, a 15-megaton burst will, even after tripling the calorie
21:42requirement, produce these 50 percent casualties out to the edges of a 75-square-mile area.
21:48Lighter clothes will greatly extend the area, and it should be remembered that far higher
21:52casualty rates will be produced nearer zero.
21:57Extending the comparisons, we see that the 100-kiloton weapon will probably cause heavy
22:02primary or secondary fire damage in average cities over about the same 10 square miles
22:08that fit at the 50 percent casualty probability.
22:11A great many small trash and litter fires would be initiated over some 25 square miles.
22:18Using the 15-megaton burst, we get very heavy fire damage over 75 square miles, and the
22:24sporadic small fire area may become in excess of 200 square miles.
22:29No estimate can be made as to how many of these fires would survive the blast wind,
22:33but based on Hiroshima and Nagasaki, plus test experience, destruction could be extensive.
22:40Tied directly to thermal effects of such magnitude is the high-priority problem of determining
22:45minimum safety parameters for aircraft delivering high-yield bombs.
22:50One channel of attack on this problem was the earlier work on means of delaying bomb
22:54bursts until the aircraft reaches a safe distance.
22:58Probe parachutes were designed for this purpose, to open after bomb release and slow the fall
23:03of the weapon.
23:04Still, it remained for CASL to derive more solid data as to what was a safe distance.
23:11The aircraft employed in the tests were a B-36 and one of our high-performance mediums,
23:16a B-47, from which extrapolations to the B-52 may be possible.
23:22On the B-47, primary interest was in the effects of radiant heat on the aluminum skin of the
23:27ailerons, 20 thousandths of an inch thick.
23:30A temperature rise in the skin of 370 degrees Fahrenheit over ambient was felt to be critical
23:36to the airplane's safety.
23:39The critical peak overpressure for the B-47 was considered to be one psi, and it was estimated
23:45that this envelope, as well as the gamma and gust loading envelopes, would lie well inside
23:50the thermal envelope at the chosen altitude of 35,000 feet.
23:55Instrumentation was extensive, primarily to measure thermal effect.
23:58A total of 43 thermocouples was installed at selected points in skin and supporting
24:03structure.
24:05Radiometers and calorimeters in the fuselage gave thermal time history and total input.
24:11Additional instruments included accelerometers, screen gauge bridges, pressure gauges, and
24:16numerous temp tapes attached to the skin.
24:19Test cameras under the fuselage were aimed at zero to assist orientation calculations.
24:25A thermal shield was designed for attachment to the inside of the canopy of the aircraft
24:29to protect the pilot and co-pilot.
24:33For locating the test aircraft's flight positions, radar was supplemented by the accurate RADIST
24:38system, which used the heterodyning or phase relationships of radio signals from transmitters
24:43on the ground and on the aircraft.
24:47Depending on five of the shots, the B-47's flight pattern was selected to position it
24:52where it should receive the theoretical maximum allowable temperature rise, 370 degrees in
24:58the aileron skin.
25:00In practically every instance, the maximum skin temperature rise was substantially lower
25:04than predicted for the observed input, indicating that predictions of heat absorption and transfer
25:10and of cooling factors were conservative.
25:14Blast damage was in all cases minor, involving only some patches of blistered paint at various
25:19points.
25:21Because of the B-47's high escape speed, the highest overpressure recorded was around a
25:25third of a pound, and the only blast damage was a split rubber coupling on the in-flight
25:30refueling manifold.
25:33On the B-36, also heavily instrumented, the maximum safe thermal level had been defined
25:38as that causing a 400 degree Fahrenheit temperature rise on the 20,000th of an inch magnesium
25:43skin under the elevator.
25:46This skin and other critical underside areas were white enamel coated to increase thermal
25:51reflectivity.
25:52Eight-tenths of a pound of a square inch was estimated to be the safe overpressure level
25:58beyond which critical dishing in of bomb bay doors and buckling of skin might occur.
26:05The B-36's flight patterns placed it tail on toward all but the last shot, for which
26:10it was flown head on for both thermal and blast phases, with a sharp turn later to avoid
26:15the cloud.
26:16As a matter of record, no prompt gamma or fallout problems were encountered by either
26:21test aircraft.
26:22With the highest intensity thermal input recorded on the B-36, the skin temperature rise approached
26:28260 degrees, 65 percent of critical.
26:32Predictions, especially for thermal response, were again generally conservative, with some
26:37inconsistencies.
26:39One effect observed was an abrupt momentary rise in jet tailpipe temperatures above the
26:44normal 500 degrees Fahrenheit.
26:47This appears to be the result of choking of the jet exhaust by overpressure and material
26:52motion associated with shockwave passage.
26:55However, no jet turbine damage was observed.
26:59At blast arrival on several of the shots, the B-36 reciprocating engines momentarily
27:04dropped and then raised their speeds by several hundred RPM before returning to normal.
27:10This was due to the engine torque balance being upset by the increased density and the
27:14gust immediately behind the shockwave.
27:18Visible thermal damage included some slight skin buckling on the elevators where white
27:23enamel had peeled or blistered, plus scorched enamel on some other areas.
27:28Some unprotected sponge rubber was burned around the lower aft blisters, one of which
27:33also developed cracks from thermal and or shock effect.
27:37Spotty blistering and blackening appeared on the radome.
27:41The highest overpressure reached the critical eight-tenths of a pound level, with the average
27:45around half a pound.
27:47Blast damage included characteristic sheet metal dishing of wings, bomb bay doors, lower
27:52turret and landing gear doors, spotty rivet failure, and severe crushing of the radome.
27:59The highest gust loadings were on shot five, reaching 60 to 90 percent of design limit
28:05load at various critical stations.
28:08It is concluded that the B-36 can withstand the critical overpressure of eight-tenths
28:12of a pound with some minor damage.
28:15However, with current delivery techniques, the B-36 delivering multi-megaton bombs will
28:20experience less than this overpressure.
28:23Another phase of the aircraft delivery problem was explored by planes fitted with gyro-stabilized
28:28cameras, which recorded time, azimuth, and tilt on a corner of their film.
28:34These aircraft, carefully positioned, took pictures of cloud rise and spread, primarily
28:39to determine their dangers to delivering bombers.
28:43Adding up the preliminary data from these successful projects, we find that both the
28:47B-36 and the B-47 can deliver weapons of the size tested on Castle with assurance of surviving
28:53the effects.
28:56Pacific Air Command bombers staging from Guam were also in the skies on the Castle shots
29:01because of continued interest in indirect bomb damage assessment, which was just one
29:06of many projects, like long-range detection, that we haven't time to look at in detail.
29:17While many phases of basic blast phenomena were measured on Castle, the projects were
29:22not on a large scale.
29:23In particular, structures testing was minimized for reasons of economy and lack of suitable
29:28sites.
29:30Bikini blast line instrumentation was, in general, of familiar types, air density and
29:35temperature gauges, ground baffle Wianco pressure gauges and accelerometers, dynamic pressure
29:42or Q gauges, and some gauges newly designed because of uncertainty as to the degree that
29:47existing Q gauges reflected dust loading of the air.
29:52It had been expected that wave forms from the Castle shots, largely propagated in cool
29:57air over water, would be clean and of ideal shape, but some records suggested dust and
30:02or water loading, indicating that the lagoon water was not a perfectly reflecting surface
30:07as had been assumed.
30:09However, the non-ideal behavior apparently did not significantly affect peak pressure
30:14levels whose curves, in general, conformed well with standard cube root scaling theory.
30:21An interesting development on shot three was a rainstorm, which at shot time apparently
30:26lay with one edge roughly over ground zero, which was in a cab on Enanman Island.
30:32Instrument readings to the east and west indicate that this unmeasured rain dampened peak pressure
30:37levels by approximately 15 percent, which is compatible with theory for a rain of quite
30:42moderate intensity.
30:45The real military importance of high yield blast effects lies not in their quality or
30:49type, but in their enormous range compared to kiloton weapons.
30:54Defining blast range in terms of destruction may be more arbitrary than precise, but the
30:59Japanese surveys indicate that 8 psi will destroy all wood frame structures, multi-story
31:07masonry wall structures, light steel frame buildings, and conventional reinforced concrete
31:14or brick buildings.
31:16This can reasonably be defined as severe damage.
31:204 psi will heavily damage portions of any normal building with near collapse of all
31:26lightly built structures.
31:28We will call this level moderate damage.
31:32A 100 kiloton weapon at optimum height will cause severe damage over an area of 5 square
31:38miles and moderate damage over 12 square miles.
31:42Contrast this, 5 and 12, with 80 square miles of severe damage and 240 square miles of moderate
31:50damage from a 15 megaton surface burst like shot one.
31:55240 square miles, more than 20 Hiroshimas in a group, more than 10 Manhattans, in which
32:01blast compounded with fire may bring almost total destruction.
32:07An idea of the extensive damage that 15 megatons can do at still greater distances is obtained
32:13by a look at the Bikini Base Camp on Enanman Island, almost 16 miles from shot one.
32:20The overpressure reached around 1.6 psi with a 12 second positive phase, and the area concerned
32:27in destruction of this order would be some 800 square miles, nearly three times the area
32:32of all the boroughs of New York City.
32:35The secondary fires would probably aggravate the damage in any metropolitan area.
32:41Tree stand studies involved mainly stands of coconut palms up to 50 feet tall and stands
32:47of Pisonia, a native broadleaf similar to the American beech, and averaging up to 80
32:52feet high and 3 feet thick at breast height.
32:56Palm stand before and after pictures show almost half the trees broken by 4 1⁄4 psi.
33:04Here is a before picture of a Pisonia stand 12 miles from shot one, and then some afters.
33:15Overpressure 2.4 psi, principal damage, crown and branch breakage, contrasted to the stem
33:22breakage characteristic of conifers tested on upshot knothole.
33:27Ground level measurements taken at intervals through a 2,000 foot stretch of trees indicated
33:32that even comparatively large tree stands will not reduce peak static pressures in the
33:364 psi region.
33:39Crater depth measurements made on Castle by sonic fathometer showed only the apparent
33:43crater depths, which may have run 30 to 50 percent less than the true craters, which
33:48were partially filled by disturbed earth and layers of water drifted sand or mud.
33:5414 1⁄2 megatons fired on a reef surface left a crater some 6,000 feet across.
34:01Estimated true crater depth, 240 feet.
34:04Note that the depth was only about 8 percent of the width.
34:08130 kilotons fired on the surface of Enanman Island made a crater 700 feet across.
34:14Estimated depth, 75 feet.
34:17On small shots, the depth to width ratio seems to increase substantially.
34:23Here a 6 megaton device was detonated at the surface of water 160 feet deep.
34:29The crater went 90 feet into the lagoon bottom and was 1,500 feet across.
34:34In general, the craters were broader and shallower than anticipated.
34:38While no rigorous scaling laws can yet be derived for application to land surface bursts
34:43in general, our crater prediction techniques were substantially improved by Castle data.
34:49A considerable grid of instrumentation was established in the Bikini Lagoon from 6,000
34:54to 20,000 feet from zero to measure underwater pressure transmission.
35:00The pressure time gauges were suspended at various depths from moored buoys, some being
35:04self-recording and some sending data to large floating cylinders referred to as tuna cans.
35:11A number of the tuna cans telemetered data to an orbiting aircraft.
35:15The transducers or gauges were of several varieties, mechanical, electromechanical,
35:21and piezoelectric.
35:24The underwater pressures were of military interest from the standpoint of effects on
35:28ships, submarines, subpens, harbor facilities, minefields, and dams.
35:34The primary finding was that the pressures from a shallow water surface burst were about
35:38of the same magnitude as the air overpressures at the same distances and are therefore probably
35:44of small military value.
35:46A related project was a study of minefield clearance in which arrays of American and
35:51Russian mines were moored between 2,000 and 18,000 feet from a 6 megaton water surface
35:57burst.
35:58Only the American Mark 39 mines survived at 3,500 feet, while at 4,500 feet the Russian
36:05also survived.
36:08About 60 percent of the older United States models survived at 7,000 feet, and no mines
36:13were damaged at 11,000 feet.
36:17It should be remembered that it took 6 megatons for these effects, and a 20 kiloton device
36:22might possibly not be reliable beyond 500 feet, though the scaling factors are uncertain.
36:31Instruments were set up on some of the Bikini Islands and coral heads in the lagoon to study
36:35water waves generated by the high yield bursts.
36:39The waves followed normal shallow water propagation theory to a degree, but a number of anomalies
36:44of timing and amplitude remain to be explained.
36:49A 12 megaton shot in the northern lagoon sent water 5 feet deep over an island 12 and a
36:54half miles away, 8 feet deep over one at 12 miles, and 10 feet over an island at 17 miles.
37:03Such waves acting beyond the radius of strong blast effects could obviously be very damaging
37:08to certain categories of shoreline targets.
37:12One aspect of the dynamic or wind pressure investigations on Kassel involved exposure
37:17of groups of jeeps to what were expected to be classical or undeformed shock waves.
37:24Deformation of the shock wave from upshot knot holes low height shot 10 caused substantial
37:29lowering of its static overpressures, but not of its dynamic pressures.
37:34Equipment damage was excessive for criteria based on the low static pressure, which is
37:38the usual parameter, so the question arose as to whether the dynamic pressure was an
37:43adequate criterion.
37:46The influence of the heavy dust loading of the air and of the blast's long positive phase
37:50duration were also in question.
37:53Jeep damage from Kassel's relatively clean shocks correlated well with upshot knot hole
37:57damage at the same dynamic pressures, so it is concluded that dynamic pressure is a valid
38:03criterion for damage to targets of this class.
38:10In summary, it could be said that Kassel gave us more substantial knowledge of the possibilities
38:14of thermonuclear warfare.
38:17Ivy Mike showed us the outlines of that huge power and Kassel filled in the outlines, pinpointing
38:23great quantities of vital data.
38:26The finding that must be considered most significant is that of the thousands upon thousands of
38:32square miles that are made potentially lethal by wind-carried fallout from a multi-megaton
38:37surface burst.