HISTORICAL REPORT ATOMIC BOMB TESTS ABLE AND BAKER. ._(OPERATION CROSSROADS- 0.... .....- ,,., QUAL17'ED FrQULMTES MAY OBTAIN COPIES OF TI•S REEPORT FROM D= NOT F'OR PUBIC RU-A& LUj VOLUME 1 OF 3 CONDUCTED AT BIKINI ATOLL, MARSHALL ISLANDS ON 1 JULY 1946 AND 25 JULY 1946 *; Director of Ship Material, Joint Task Force One 9019 Coy / QT.UAL7= MO•U NOT FOa PUD L MAY OAN COOPM3 OF TMS WOn FROM Dfb LAB HISTORY OF DIRECTOR OF SHIP MATERIAL OPERATION CROSSROADS 'Table of ,Conents PREFACE By Rear Admiral T. A. Solberg, USN, Director of Ship Material, Joint Task Force One INTRODUCTION: ORIGINS OF ATOMIC BOMB TESTS Chapter 1 DIRECTOR OF SHIP MATERIAL Chapter 2 BUREAU OF SHIPS Chapter 3 DAMAGE CONTROL SAFETY SECTION Chapter 4 BUREAU OF ORDNANCE GROUP Chapter 5 BUREAU OF AERONAUTICS GROUP Chapter e ARMY GROL/ND GROUP Chapter 7 NAVAL MEDICAL RESEARCH SECTION C.hapter 8 ELECTRONICS GROUP Chapter 9 SHIPS INSTRUMENTATION GROUP Chapter 10 ORDNANCE INSTRUMENTATION GROUP Chapter 11 OCEANOGRAPHY GROUP Chapter 12 SHIPS TECHNICAL PHOTOGRAPHY SECTION Chapter' 13 SUMMARY I I Appendix I: 'Appendix I1: Table of Contents (Cont.) I. BIBLIOGRAPHY LIST OF TARGET VESSELS Appendix III: OPERATIONAL DESIGNATIONS OF GROUPS AND UNITS Appendix IV: LIST OF PERSONNEL Appendix V: PICTORIAL REVIEW fk i.! PREFACE The purpose of this history is to provide a general, nontechnical introduction to the voluminous technical reports evolving from Operation Crossroads. There are many reasons for such a history but it is enough to say here that any assessment of results in a large test operation must take into account In some manner how the results were obtained. The history, therefore, provides a chronological account of the effort, extending over a period of eight months, which the groups under the Director of Ship Material, as well as some other closely related groups, put forth to obtain the results that lie behind the technical reports. The scope of the history includes all groI from Army corps and Navy bureaus which either served directly under the Director of Ship Material or gathered data of interest to technical studies made in his organization. This will account for the fact that chapters are included on certain instrumentation groups whose activities were directly rel ii sponsilj.e to the .. echnical Lirectr)., Although these cnai)te2s do not give conolete chronographies of the activities of the instrumentation groups, they serve to show the means by which measurements were made. Since the relation of in".-trumontation to damage was stressed throughout the operation, the inclusion of an account of how the instrumentation data were gathered is considered iia:)ortant in assessing the relevance of the damaoe data. Certain aspects of the work of insticuruentation groups could not logically be separated from other groups from the viewpoint of the technical reports; for this reason those aspects are included with the Director of Ship Material history. The history has another function. Because the m*ny dif- ferent Army and Navy groups serving under the Director of Ship Material had diverse tasks, each of them wrote historical accounts of their own, which will be, naturally, mo~e elaborate with relation to their work than the account given here. This history serves to tie all of these together and to give a oemblance of unity to one of the most complex undertakings in Operation Crossroads.-, 10 January 1947 iv .y-h ORIGINS OF ATOMIC BOMB TESTS INTRODUCTION ORIGINS OF ATOMIC BOMB TESTS Underwater Exlosilon Program On 20 June 1945, when the European war had ended and the Pacific war was approaching its climactic phase, Vice Admiral E. L. Cochrane, Chief of the Bureau of Ships, and Vice Admiral (then Rear Admiral) G. F. Hussey, Chief of "theBureau of Ordnance, addressed a joint letter to the Chief of Naval Operations proposing a comprehenisve program for testing high explosives against merchant and warship hulks, captured enemy vessels, and United States Navy combatant ships about to be stricken from the active list. It was desired to go beyond the model studies and full-scale caisson tests which were normally carried on by the two Bu'eaus. proposal for "controlled This destructive testing in a planned program to elicit fundamental information on damage to shiplike structures by high explosives" met with approval. The Stwo Bureaus and their research agencies sped up the planning vii which had already been done to carry out this program. Meanwhile other forces were at work. a The First Three Atomic Bomb Explosions In the New Mexico desert, near Alamagordo, on 16 July 1945, scientists of the Manhattan District secretly carried out the "Trinity Test" with the first explosion of the atoric bomb, which had been under civilian and military development since July of 1939, when Einstein and other scientists brought the military potentialities of such a weapon to the attention of President Roosevelt. On 5 August, only three weeks after this test, the first military atomic bomb exploded over Hiroshima, and a few days later another atomic bomb exploded over Nagasaki, hastening the Pacific war to its close. The Japanese, faced with this new terror as well as imminent invasion, surrendered unconditionally on 14 August, nine days after the ftrst atomic bomb had been dropped. Even before technical personnel made their studies in Japan, reports of damage at Hiroshima and Nagasaki offered conclusive proof, if any were needed, of the tremendous military potentialities of this new weapon. I p vi Proposal for Ship Tests with Atomic Bombs On 28 August, the Chief of the Bureau of Ships, Vice Admiral Cochrane, informed his design and research agencies which were planning new programs of underwater explosion work with conventional explosives, that the Bureau of Ships "ccmust be prepared to undertake broad-scale experiments with the atomic bomb to clear up its major influence on naval warfare before we can at all consider an extension of the underwater explosion work on the concept of TNT or its associated explosives." Exploratory discussions on this matter were held with the Chief of the Bureau of Ordnance and other personnel of the two Bureaus. On I October, Vice Admiral Cochrane and Vice Admiral Hussey sent another letter to the Chief of Naval Operations stating that the appearance of the atomic bomb "has made it imperative that a program of full-scale testing be undertaken to determine the effects of this type of bomb, both underwater and above water, against ships of varioas types." This letter which outlined the problem at considerable length, added that ix Ig the two Bureaus would "'prepare and present for consideration at the earliest practicable date a testing program with the atomic bomb Requesting including specific that various warships ship requirements." already scheduled disposal be retained for the atomic bomb tests, for the letter pointed out the severe limitations of model work and the need for realistic tests. 'Certain of the proposed post-war design developments in underwater ordnance and in underwater protection, the letter stated, require "realistic ship targets, either by virtue of the inherent nature of the problem, or to provide adequate guidance so that model work and simplified experiments may be prosecuted intelligently."' Approval o9 Atomic Bomb Tests In a letter on 16 October, Admiral E. 3. King, Commanderin-Chief of the United States Fleet and Chief of Naval Operations, recommended that the Joint Chiefs of Staff approve test of the atomic bomb against naval vessels. The Joint Chiefs of Staff undertook study of this proposal. When the x tX a proposal was referred to thern, the Joint Staff Planners appointed a planning sub-committee under the chairmanship of Major. General Curtis LeMay, Army Air Forces. The Bureau of Ships was represented on this sub-committee by Capt. L. A. Kniskern, the head of Its Design Branch. The sub-committee, which first met early in December, submitted a report about a week later recommending that the tests be held, that they be conducted by a Joint Task Force, that the President issue a directive to the War and Navy Departments to conduct the tests, and that the Joint Chiefs of Staff be authorized to appoint a Joint Task Force Commander. The sub-committee also made general recommendations relative to the nature of the tests. The question of appointment of the joint Task Force Commander was left open, two alternative recommendations being made. The Secretaries of War and of the Navy made the first public announcement af the proposed tests in a joint press release on 10 December, stating that the Army and Navy contemplated a "Joint test of atomic bombs against naval vessels." X1 Creation of 1o=nt Task ForceOre As it was generally understood that the Task Force Commander, if a naval officer, would be Vice Admiral W. H. P. Blandy, the Deputy Chief of Naval Operations for special Weapons, Admiral Blandy took an active interest in the proposed tests during the period of the sub-committee sessions, and increasingly as the time approached approval, which had been assured. for presidential On 10 January 1946, the President approved the recommendations of the Joint Chiefs of Staff essentially as made by the sub-committee; and on 11. January, the Joint Chiefs of Staff created Joint Task Force One, appointing Admiral Blandy as its Commander. Admiral Blandy had already begun specific planning for the two tests, starting with consideration of various proposals for target arrays drawn up by the Bureau of Ships. On 7 January, a large conference had been held in the offices of the Manhattan District, Army Engineers Building, Washington, D. C. Army, Navy, and Miamhattan District representatives discussed the general problems of the tests, giving attention to the x~i *" latest sketches Alamos * of target arrays. Laboratory scientific agencies Scientists from the Los and personnel from other military and discussed special problems during the same day. ,Misson ot joint Task E2=9 _Qn The mission of Joint Task Force One, which had already been discussed in these conferences, was publicly announced by Its Commander on 24 January, when Vice Admiral Blandy told the Senate Committee on Atomic Energy: "The mission of Joint Task Force One Is primarily to determine the effects of the atomic bomb upon naval vessels in order to gain Information of value to the national defense. The ultimate results of the tests, so far as the Navy is concerned, will be their traxwlatlon Into terms of United States sea power. Secondary pur- poses are to afford training for Army Air Forces personnel in attack with the atomic bomb against ships and to determine the effect of the atomic bomb upon military installations equipment." and He also announced that the atomic bomb tests had been assigned the code name Operation Crossroads. xlii INDEX VOLUME I PREFACE Page INTRODUCTION ORIGINS OF ATOMIC BOMB TESTS Underwater Explosion Program ...... vii The First Three Atomic Bomb Explosions ...... vii i Proposal for Ship Tests with Atomic Bombs .... ix Approval of Atomic Bomb Tests .. . ..... x Creation of joint Task Force One .............. xll Mission of Joint Task Force One .............. ii CH4APTER 1 DIRECTOR OF SHIP MATERIAL Exploratory Discussions.......... ....... Pbsitian in Task Force ...................... Formatin of Staff ... L ........... *, 13.Relation to Instrumentation Groups.......... Relatin to Operational Units .................. Respcmsibility .......... Staff for Technical Inspections ................ 3 4 5 7 7 88............... 10 DEVELOPMENT OF TARGET ARRAY Prelimina~ry...........................- 13 Early Plans and Philosophy .................. 14 First Sketches ............................. 14 Early Changes ............................. 16 K Sketches for Each Test ...................... Modfications for Both Tests ................ F',arther Adjustments........................18 16 17 Mooring and Loading Prablem. ........... LAW Development . ........................ Final Target Array for Test Able .............. Final Tat-get Array for Test Baker ............ Chbmges Resulting from Test Able ............. 19 20 21 22 xv 23 Page PREPARATIONS FOR THE TESTS Preliminary .. ....... ... ....... .......... 25 Assembling of Target Ships .. . I ...... ... . 25 Departure of Advance Units .............. .. 26 Crossroads WVork on West Coast ................... 27 Crossroads Work at Pearl Harbor .................. 27 Postponement of Tests ........................... 28 Preliminary Ispections by Groups ................ Departure xf Stafffrom Washington ................ Rear Echelon ................................... 29 30 30 Stopover at Pearl Harbor ......................... 31 Final Preparations at Bildui ....................... 32 Rehearsals ofl Iitial Boarding Teams .............. Situafo-i Reports to Deputy Commander ....... 32 e... Postponement of Queen Day ....................... Queen Day. Rehearsal ...... ............. 33 34 35 OPERATIONS DURING TEST ABLE Evacuation of Lagoon ............................ Dispersal of Staff .................................. Dropping of Bomb ....................................... Aerial Reports from PBM Charlie ................. Re-entry Into Lagoon ............................... Preliminary Suzvey of Damage ..................... Able Day Situation•Reports ...... Reboarding of Target Ships ............ 36 36 37 38 39 40 41 41 Control of Inspections ....................... ... Repair and Salvage Work ........................ Damage Reports .............................. .. 44 45 43 OPERATIONS DURING TEST BAKER Re-arrangement of the Array ......... Ship Mooring ................................... Ship Preparation . .. . .......................... W IllJam Day Rehearsal ............. Changes in Boarding Procedures .... Baker Day ........................ Reports o Technical Observer ........... Re-entry Into Lagom ...... ................ xv1 ... 47 47 48 o....... 49 ............... 50 .. . 50 I.........51 .......... 52 P--ge Preliminary Salvage Operations ............ Decontamination Measures ................ Technical Inspections .................... Safety Program ....................... Departure from Bikini . .................. Damage Reports ........................ 53 54 55 56 56 57 CHAPTER 2 BUREAU OF SHIPS GROUP 683 64 Formation of Group ................... Responsibility ....................... PREPARATION OF TARGET SHIPS ... 66 Preliminary ....................... 67 General Preparations .................. Heavy Target Ships ..................... Light Target Ships ............... Target Submarines .................... Submarines at Pearl Harbor ............... Concrete Barges and Floating Drydock 68 .... ...... 70 71 71 72 Ship Measurements and Reference Planes ..... 73 Twist Pendulums and Deflection Gauges ...... Magnitude of ship Preparation Task 73 74 PREPARATION OF NON-TARGET SHIPS Preliminary............................ Task Force Flagship ................... Director of Ship Material ................. Instrumentation Ships .................... Press and Observer Ships ............... Bomb Carrying Ships ................... 76 76 77 77 78 79 REBOARDING AND INSPECTION Preliminary ........................ Preliminary Inspections ................. Inspection Instructions ................. Inspections after the Tests ................ 80 80 81 82 SUPPORT OF TEST OPERATIONS Assembly of Staff ...................... Final Pre-Test Inspections ............... Test Able Operations .................. Test Baker Operations ................. 84 84 85 86 xvii Page CHAPTER 3 DAMAGE CONTROL SAFET1 SECTION Formation of Section ................... Responsibility ........................ 91 92 SUPPORT OF THE SAFETY PLAN General Considerations. ................. 93 Training ........................... Instruction of Target Ship Personnel ......... Operational Procedure .. ................ Test Able Operations ................... Test Baker Operations .................. Post-Test Operations ..................... Concluding Comment ................... 93 94 ,5 96 97 98 98 CHAPTER 4 BUREAU OF ORDNANCE GROUP Formation of Group ..................... Responsibility ....................... 103 104 C OORDINIATION OF 0STRUMENTATION Preliminary.......... ................ Blast Measurements ................... Temperature Measurements .............. Radioactivity Measurements .............. Static Pressure Measurements ............. Accelerometer Measurements .............. 106 106 107 108 108 i0 EXPLOSIVES UNIT Preliminary .......................... Organization ......................... Inspections and Tests .................. 110 1.1 111 FIRE CONTROL UNIT Preliminary .......................... Optical Section ...... ................... Surface Vessels Section ................. Radar Section ... ...................... Submarine Section.......................... xviii 113 s13 I I 11,16 Page GUNS AND MOUNTS IJNITi Prelim inary ......................... 117 ......................... Organization Preparations .......................... Pre-Test Inspections .................... 118 118 119 AVIATION ORDNANCE UNIT Preliminary ......................... Organization and Inspections ............... 120 120 UNDERWATER ORDNANCE UNIT Preliminary . .......................... ..................... Primary Planning ................... Modification of Plans Preparation of Weapons ................. 122 123 123 124 Underwater Photography Secton ........... 125 Underwater Photographic Equipment .......... 126 ARMOR AND METALLURGY UNIT 127 127 128 Preliminary ......................... Preparation and Installation of Armor ........ Inspections and Tests .................... TEST OPERATIONS Test Activities at Bikini ................. Test Able Operations ................... .................. Test Baker Operations 130 131 131 CHAPTER 5 BUREAU OF AERONAUTICS GROUP Formation of Group .................... Responsibility ........................ 135 135 OPERATIONAL PLANS Routine Activities ..................... Transport and Air-Sea Rescue....... Photographic Aircraftt .................. 137 137 I[ ..... DRONE PROGRAM Exploratory Discussions.................. Operational Assignment..................141 Manufacturing Program ................. Radio-Control Problems ................... Radioactivity Filters and Geiger Counters ..... xix 140 141 i4, 142 Additionriu ifformation ...... Design and Testing of Rl-idioactivity Filters Design and 'Testing of Geiger Counters .. Operational Training . .1..... .......... Collection of Water Samptes. . 143 . 143 144 1.45 145 ..... 147 147 .. . . .. SHIP PREPARATION PLAN Target Aircraft ........ Embarkation Orders. .. .............. Continental Loadings ... . Pearl Harbor Loadin.s ...... Seaplane Moorings .. ....... Aviation Fuel and Lubricants ........... Aviation Or dnnce .... ... ,I.. . Airborne Electronics .... .... .. INSPECTION PROGRAM Preliminary Inspection in Shhyyar(]2 Pre-Test Activities at Bikini .......... Test Able Operations ......... Exposures for Test Baker .... Test Baker Operations 148 . . 149 150 150 . . .... .. 151 151 . 153 1,54 154 155 1 VOLUME II CHAPTER 6 ARMY GROUND GROUP Exploratory Discussions. ...................... ........... Formation of Group . Responsibility ........ SUPPORT OF ARMY GRO()j\ C)ROTOiU Quartermastc, Unit . Engineer Unit . Ordnance Unit ... Signal Unit ... .... Chemical Unit . . .. AIr Unit ................. TEST OPERATIONS Preliminary rinspcctions .. Final Preparations ..... Test Able Operations .. I. Participation in Sucond 1 -, ,Test Baker Operations .. 1 160 1)6 L PLAAN i 63 165 . .. 167... 168 .. !...0 Cl':. . .. . . I14 1V4 .. ......... .... ........ , ... . ... I' 1' Page CHAPTER 7 NAVAL MEDICAL RESEARCH SECTION. Exploratory Discussions .......................... Formation of Section ............................ Responsibility .. ............................... 181 181 182 PLAN OF MATERIAL EXPOSURE General Considerations .......................... Instrumentation .................................. 184 184 Animals ............ ........................... Insects, Bacteria, and Other Test Material ......... 185 186 OPERATIONAL PROCEDURE Embarkation and Departure ....................... Test Able Operations ............................. 188 188 Test Baker Operations ........................... 190 CHAPTER 8 ELECTRONICS GROUP Formation of Group ............................. Responsibility ................................... 193 194 SHIP PREPARATION AND INSPECTION Preliminary ....... .. .................... Personnel . .............. ........................ Equipmen, in Operation During Tests ............... Preparing Electronics Equipment .................. Airborne Electronics ............................. Inspection Plans ................................. 196 196 197 197 198 199 TECHNICAL COMMUNICATIONS Preliminary .................................... 200 Task Force Flagship ............................. Director of Ship Material ......................... Instruimentation Ships .............................. Press and Observer Ships ............. ........ Communications for Director of Ship Material ...... Special Communication Projects ................... ELECTROMAGNETIC PROPAGATION Preliminary ..................................... Propagation in Target Area ....................... 204 204 Monitoring the Equipment on Target Vessels ......... Radar Plotting of Target Array .................... Reflectivity Measurements ........................ 205 206 207 xxi" 200 201 201 202 202 203 Page Remate Monitoring of Radio Transmissions .......... Infra-Red Measumrement ................. ......... 209 21.0 BLAST, PRESSURE, AND SHOCK MEASUREMENTS Preli mi sm;y ..................................... 211 Sonobu•oys .............. ....... . 211 Sonobuoy Recorders .............................. 212 Telemetering .............. .................... 213 Contactng Research Agencies ...................... 213 Telemeter•ng Plans .................. . ..... 214 Telemetering Installations ............. 215 WAVE MEASUREIMIENT Television ....................................... Television Installations ........................ Sonobuoys and Fathometers ....................... . 216 216 217 OTHER SPECIA-L PROJECTS Timing Sigfals ................................... Navigational Radar Beacons ........................ Telemetering for Geiger Counters .................. Drone Boat Program ............................. Installations on Drone Boats ........................ TEST OPERATIONS Ship Inspections ...... .......................... Performance of Special Projects ................... Special Projects for Test Baker ..................... Inspections After Test Baker ....................... CHAPTER 9 SHIPS INSTRUMENTATION GROUP Exploratory Discussions ........................... Fornmation of Group ............................... Responsibility .................................. 218 218 218 219 220 222 222 223 225 229 230 231 LOADING INSTRUMENTATION Measurement Problems ............................ Telemetering - Air Pressure .................... Pressure Gauges ................................ xxil 233 233 234 Page Jnderwater Shock Wave Meas;.rement....... Summary RESPONSE INSTRTIME NT'ATI(Oh Measurement Problems ................ Instantaneous Velocity Meters ............. Meanss of Recording .................... Location of Velocity Meters .............. Miscellaneous Shock Gauges ............... Summary .......................... -- EIPERTlJRE, PR.ESSURE, AND OTTHER 235 236 237 237 238 239 239 240 INSTRUMENTATION Preliminary . Temperature 241 ......................... ................................... 241 Interior Pressures and Winds .............. ....................... Roll and Pitch. 44 246 Other Physical Observations ............... 240 CHAPTER 10 ORDNANCE IUSTRUIYEIETATION GROUP Exploratory Discussions ................ Formation of Group ..................... Responsibility. ........................ 251 251 253 AIR BLAST INSTRUMENTATION Measurement Problems ................ Aluminum Foil Meters ................. 254 254 255 3Ball-Crusher Gauges .................. Free Piston Recording Gauges ............. Linear and Logarithmic Axis Recorders ...... 256 2,56 ................ Other Peak-Pressures .... Pyramidal Orientometers ............... Shock Wave Velocity Measurements ......... 256 257 257 Photographic Methods .................. 258 UNDERWATER INSTRIUJIMET•ATION Measurement Problems ................ Bail-Crusher and Diaphragm Gauges ......... Other Gauges Low Frequency Sound Measu ements ........ Hydrophones .............. xxWU 269 260 2.......................260 260 261 Page R.ADIOMETRY INSTRUMENTATION Measurement Problem..................262 Unfocused Bolometers..................262 Focused Bolonieters .................... Spectrography ......................... Photoelectric Units 263 63 263 ............... 264 Photographic M\6easurement oi Fire Ball ...... CHAPTER 11 OCEANOGRAPh-Y GROUP Exploratory Discussions ................. Formation of Group ................... Responsibility ....................... 267 68 269 WAVE MEASUREME NT Preliminary .............. Photogrammetry and Television ........... Model Basin Studies .................... 270 Instrumentation Studies ................. 272 Fathometers ........................ Photogrammetry Installations ............. Bottom Pressure Recorders and Wave Duoys . 270 271 . 273 273 274 Water Height and Level Indicators ......... Swell Recorders ..................... Seismology Problems .................. 274 274 276 Initial Seismology Plans . ............... 276 Coordination of Plans .................. Seismic Sea Wave at Hawaii ............... Measurement of Water Crater ............ OCEANOGRAPHIC SURVEY Preliminary ........................ Physical Oceanography ................. ....................... Fisheries.... Biology ............................ Geology ........................... The Bowditch Expedition ................. BIological Collecting .................. Geological Investigations ................. Fisheries Work ...................... Oceanographic Measurements .............. Results of Oceanographic Survey .......... xxiv 276 277 278 279 279 280 281 282 283 . 283 284 284 285 Pa~e RADIOLO( ICAL SAFETY RECO)NNAISSANCE Preliminary .......................... Preparations .............................. 286 286 ............................ 281 Operations CHAPTER 12 SHIPS TECHNICAL PHOTOGRAPHY SECTION Exploratory Discussions Formation of Section 291 2................ 291 ................ 292 Responsibility ....................... PHOTOGRAPHIC ACTIVITIES OF VARIOUS GROUPS 293 ........... Ship Preparation and Inspection 294 Oceanography . ...................... 294 2,95 296 26 Electronics ......................... ................... Ships Instrumentation Moving Film Spectrographs ................. Underwater Photography ................... Icaroscope Observations ................... Aerial Photography ................... Steroscopic Photography ................... 2ý 298 298 CHAPTER 13 S UMMARY Organization for Technical Reports .......... Decontamination Problemss ............... ...................... Conclusion ... 301 302 303 APPENDICES APPENDIX i I - 3 Bibliography ....................... APPENDIX ID List of Target Vessels ................ II - 3 APPENDIX III Operational Designation of Groups and Units APPENDIX IV List of Personnel .................... . . III - 3 IV - 3 VQLEvE Ill .APPENDIX V Pictori.a Review V . XXV - . CHAPTER 1 DIRECTOR OF SHIP MATERIAL 4 x I tLLw 0 W L) 2 w - w 0 6, -aa o z 'Ji ;! w LL WW 0 -4 - 02 4 .4 0~ U) Z r, -, wx Li. 0 1-- N 2 *4 (fl.() O~jjE DIRECTOR, OF SHIP MATERIAL Exploratorv Discussions During this exploratory period, the Chief of the Burea.u of Ships, Vice Admiral E. L. Cochrane, who would have a prime concern in any tests of the bomb against naval vessels, had been kept informed of the trend of developments. But the top secret classification of the project permitted very few other officers in the Bureau to know more than the most general facts concerning it; and then, too, the whole project was in such a nebulous state that there was no positive assurance it would be carried through. Around the middle of January, the Commander joint Task Force One requested that Admiral Cochrane designate an officer with whom he could deal directly and personally on all matters affecting the proposed tests, which by now were called Operation Crossroads. As the Bureau of Ships had a paramount interest in Operation Crossroads, Admiral Cochrane recognized the great responsibility which would devolve upon the officer selected to represent the Bureau and to carry out its extenslve and complex tasks. Accordingly, he decided to appoint Rear Admiral T. A. Solberg, head of the Research Branch of the Bureau of Ships, as the senior member of a large bureau group for Operation Crossroads. Admiral Solberg had been a deputy member of the "Tolman Committee", appointed by Major General Leslie R. Groves in the fall of 1944, almost a year before the "Trinity Test" of the atomic bomb at Alamagordo, New Mexico, to investigate further technical developments in atomic energy for both civilian and military purposes. This committee, under the chairmanship of Dr. R. C. Tolman, had studied many suggestions from personnel connected with the atomic energy projects concerning "the use of nuclear energy for power and the use of radioactive by-products for scientific, 3 1 medical, and industrial purposes." , On 17 January, Admiral Cochrane called Admiral Solberg and Captain Kniskern to his office and discussed the entire problem with them. He explained that he was appointing Admiral Solberg to this position because it was desirable to have someone of his rank and experience to coordinate all the varied and extensive efforts of the Bureau of Ships and to insure the success of the bureau's work in the project. Admiral Cochrane promised full support, with the assignment of an adequate number of well qualified officers to work full time on the project. He then instructed Admiral Solberg to prepare an administrative order setting up a special section in the bureau to handle Crossroads work. This order, dated 22 January, set up Code 180, the Crossroads Section; and on the same day Admiral Solberg was designated as head of the section and Captain Kniskern as his senior assistant. A number of officers took up duties in the section immediately, and others were added as rapidly as they could be freed from current daties. Position in Task Force Meanwhile, Admiral Solberg and Captain Kniskern consulted with Rear Admiral (then Commodore) W. S. Parsons as to the relationship of Admiral Solberg's group to the rest of the Task Force. In the first organization chart 'prepared by the Task Force., Admiral Parsons was shown as Deputy Task Force Commander for Technical Direction, and under him was the Technical Director, Dr. R. A. Sawyer, in charge of scientific aspects of the tests, particularly the preparation of the bombs and instrumentation to measure their effects. But there was apparently no place in the organization for the primary tasks of ship preparation and inspection. Admiral ISee H. D, Smyth, Atomic Enera, for Military Purposes(Princeton, 194b), pp. 224-5. 4 Parsons was quick to recognize th-e necessity for broadening the Organization to include the vast amount of technical effort required outside the field of scientific instrumentation, but closely related to it. Accordingly, Admiral Solberg was assigned a place in the organization parallel to that of the Technical Director. This assignment was made because it had become apparent that there must be central control over all the materials on the target ships, whether normal materials or those placed aboard for test purposes, including special instruments. In other words, it was essential for one agency to coordinate all of the problems relating to the target ships themselves including special test materials on the ships. Admiral Solberg received this overall technical responsibility. It then remained to select a title for this position. When the title "Director of Ship Material" was proposed, Admiral Parsons and Admiral Blandy agreed; and henceforth this title appeared in the Joint Task Force One organization charts, under Admiral Parsons, the Deputy Task Force Commander for Technical Direction, and parallel to Dr. Sawyer, the Technical Director. It was agreed that all instrumentation would be subject to the Technical Director's approval, but that the Director of Ship Material would have a major interest in problems involved in locations of instruments on target ships and in their installation, as well as in the results they gave with reference to ship damage. It was therefore agreed that the closest liaison between the Technical Director and the Director of Ship Material would be necessary. Formation of Staff Many representatives of various Navy bureaus and Army Ground and Air Forces, who had been involved in the early planning of Operation Crossroads, found their appropriate place in Joint Task Force One on the staff of the Director of Ship Material when that organization was created in late January with the code designation 014. Most of the staff members reported to the Director of Ship Material before 5 I February. Capt. L. A. Kniskern reported as head of the Bureau of Ships Group (014-K), remaining in tiat position until shortly before Test Able when he became Dpputy Director of Ship Material, being relieved by Capt. F. X. Forest, a member of the Bureau of Ships Group. Even during the early stages, however, Captain Kniskern, as first assistant to Admiral Solberg, served to all intents and purposes as a deputy director. Col. J. D. Frederick reported as head of the Army Ground Group (014-B), which included personnel from the Quartermaster Corps, Signal Corps, Ordnance Department, Chemical War.iare Service, Air Corps, and Corps of Engineers. Capt. T. C, Lonnquest joined the staff as head of the Bureau of Aeronautics Group (014-J). Capt. E. B. Mott became a member of the staff as head of the Bureau of Ordnance Group (014-L). Capt. R. H. Draeger (MC), head of the Naval MedicalResearch Section (014-M2), joined the Director of Ship Material staff, as great stress was being laid on animal studies aboard the target ships. Capt. 0. Schneider (MC), reported around the middle of February as head of the Damage Control Safety Section (014-MI), which had been created by the Safety Adviser for determining non-radiological hazards. An officer from the Electronics Group, Comdr. F. X. Foster, was assigned to the staff early in February as Special Assistant in Communications. Early in March, the Bureau, of Ships ordered its historian to report to the Director of Ship Material for duty, as he was designated historian for the Director of Ship Material. Two other bureaus were minor participants. The Bureau. of Yards and Docks in early March provided a small group (014-Y), under Comdr. Raymond Lamoreaux, (CEC), which had a structural interest in three steel-reinforced concrete vessels in the target array. The Bureau of Supplies and Accounts, which was interested in normal ships' stores, in May provided a small group (014-S), under Lieut. Comdr. 0. W. Fraser, (SC). 6 elation to Instrumentation Grous Instrumentation groups from the Bureau of Ships, while rcponsible to the Technical Director (013), performed duties on the staff of the Director of Ship Material, as he was rezpon.-fble for all Bureau of Ships activities in Operation .rossroadso Conmdx. C. H. Gerlach, head of the Ships InstruS,ntation Group (013-C), had been engaged in the underwater :xp]ioson research program of the Bureau of Ships from which much of the ship instrumentation evolved. Comdr. Roger Revelle, head of the Oceanography Group (013-B), who .L 0 0 a 0 W IL 44 !AJ - z h It 0I (A :iLi 06 Sivj dos DEVELOPMENT OF TAPGLT ARRAY Preliminary The number and disposition of target ships for the ate oic bonib tests were matters of such fundam-ental importarce 1r, all activities concerned in the test that it was neces.,rv-, ,u.bject all proposals to the closest examination anu to oK tain opinions and comments from all of 1L-ese activities before the final target arrays could be approved by the joint C'iiefs of ,8roff In the end, of course, it was necessay to adopAt compromise solutions which, however, were re•c.sonab.y satisfactory to all concerned, Even during the period of preliminary i,"iscsions" by the special sub-committee of the Joint Staff Planr(e.;'rs it was necessary to have some approximate conception of a feasible target. array. The Chief of Naval Operations had made certahi ships available for explosion testing and later specifically for the atomic tests. With a knowledge of the characteristics of the available ships, and a broad background of experience fromr war damage analysis and controlled tests, It was natural and' logical that the Bureau of Ships should take the fir-st steps n attempting to formulate a target array, and should play an yn portant part in all subsequent developments of target arrays. At the time that the atomic bomb tests were under con- sideration by the: Joint Staff Planners, it was considered de. sirable to have three tests - one with the bomb burst in air above the target array, one with the bomb burst at the surface of the water, and one with .thebomb burs[, at the su f..ce. of the water, at an unspecified depth. The characteristics of the bomb were not known to the Bureau of Ships" hence assumptions as to damage had to be based on the publishlc;d statement that the bomb was approximately equivalent to 20,000 tons of TNT. Summarizing, the first studies of target arrays made by the Bureau of Ships in December lic,45 were based on the following: (a) Knowledge of ships which probably would be available for the tests. 13 (b) KnLowlcdgu' of (.) VC!y roij.yIli Lrier.u.tica of tho<;.:.sliipa, of damaging, eifecteL of 2Q000 tom;flo1 .li'U, baioed on w-ar expU-riln.e arid t.c,-;tang COt.X[{>, ri• itii .ti[ . c~h, , all .. chargegs. LLti Plano iad PbiUoophy Th.E, first sl.ctch, prepared by the Bureau of Ships before 1c')-m , 194b, nevertheless, had some of the characteri ti, of the in-Ai target arrays. The first and the moot inportant of Lhese features was the ise of relatively large JnurJ.mbcA of merchant type vessels and. destroyers to provide L,ro: gaugesp of daxmage effects. Secondly, some ships placed, close to the center were expected to be sunk or just J.ort of being sunk, while others at extreme range were ex,ectcd to be essentially undamaged, and those in between -mcre to show gradatior; of damage between maximum and -inimxum as finilly required by joint Chiefs of Staff. Thirdlythe dezLr(yers and merchant-type vessels were arranged in approxim~ately radil-lines, out from the center, with two oracntations, end-on ,.tnd beam-on, toward the center. Certain basic differences from later lay outs will be ý. notrod., however. In the first place, it was assumed that. all target vessels would be moored bow and stern to obtain de_;.re( orientations. Sceohdly, ;.: was assumed that the ranges of interest for the thzree t,3sts would be approximately the same, so one ietch.~wac used for all three tests, with notes covering the targeL ah-Utz which probably would be required as a result ,f dmag-c from ea~ch of the first two tesLs. First Sketches No !as .ritý:.-- made of Sketch No. .1 and the originnl fQ ar deJ!)vClop"ing cuanges during, the period frorn .19 De(cetrrmber to 3 Jynu_.iLry: hence it bears the date of 3 January. 14 (No. 2 was assigned to a small tracing paper overlay containing the center of the array for the air burst test; this was later put on Sketch No. 3 In dotted indication). Sketch No. I waaA Csussed informally with Admiral Blandy, and also with the Chief of the Bureau of Ships, Admiral Cochrane. As a result of these discussions and other developments during this period It was decided, at least tentatively, to make the following changes, which were incorporated In Sketch No. 3:(1) As soon as Bikini Atoll was selected tentatively as the site of the tests, the center of the target array was located as close to Bikini Island as was considered practicable at the time. (2), Twelve landing craft were placed on the island, beached, although these had not been made available by the Chief of Naval Operations. I3) PRINZ EUGEN, NAGATO aad SAKAWA were added. ) It was considered out of the question to moor all ships, hence simple anchoring was shown. (5) It was considered necessary to place an aircraft carrier as the aWming point for the air test. (6) It was considered necessary to place the other available aircraft carrier, a submarine and a battleship at distances from the surlace burst (second test) which were within the estimate of mean radial bombing error. Mooring of these targets bow and stern was essential. (7) It was desired to, have a closer grouping of ships toward the center for the air burst test, so as to insure that major combatant vessels would be close to the explosion, even with mmaxLnm bombing errors. (By Battleships and cruisers were re-arranged to afford a better distribution with respect to pairing in orientation. 15 Early Chne Sketch No. 4 dated 8 January, was essentially like except that the center cd the array was broulht closer Bikini Island so that the ground installatims proposed time would be exposed properly, and also to provide a No. 3 to at that short- er range desired by the Los Alams Group at that tiie fo 'nstr umentation purposes. Sketch No. 4 was In effect at the time of the first meeting with Los Alamus perasomel who had at hand information regarding the air blast and shock wave intensities to be expected. This information did not materially change views toward the surface. test; but figures showed that for the first test, the air blast-intensities would decay with distance more rapidly than has beefi the guess, and this Information becarne a factor In the progressively closer grouping of target ships around the center lox Tes, Able. In Sket. No 5, dated 10 Janmary, the major combatant ships were moved closer toward ,the center. In order to close In the Immediate center for Test Able, the point-of-aim carrier was changed to be moated bow and stern, Instead of auchord, thereby enabling the four surrounding ships to be moved closer in. For Test Baker, the close-in battleship and submarine were Interchauged in position to place the battleship broadside to the explosion. Other ctaages addeed various landing craft beached an Pikini Island, and several destroyers were spread out in the astbrly sector to insure an adequate coverage with respect to radioactively contaminated spray, which could be expected ,in this sector in Test Baker. Finally, it had been decided to submerge five of the submarines in Test Baker. Sketches for Each Test At this time, plans were proceeding on the basLs of oniy two tests - an air burst and a surface test as the Los Alamos Group i.msidered that only two tests would be feasible In 1946, and that a surface burst was preferable to a shallow underwater burst In Bikini Lagoon. 16 By the middle af January, it had become obvious that the reqrlremeats for shim/locations In the two tests would diverge to a greater degree txan first thought. From here on, the sketches were treated separately for Tests Able and Baker. Sketch Nos. 6(lbst Baker) and (Test Able), dated 23 January, offered no major changes except that five heavy hull submarines had been made available as a remilt of tle l~nportance with which the future role of the submw.41n.e was regarded in many quarters. The sabmarines previmusly available were In a.ll cases submarines which were beIng retired from active patrol service in the later months of the war. Modern designs were desired in the target array wherever possible, and it war, possible to use modern submarlnes. Three light hull vesseLs were s=i2J retained in the target grray, peruni-tting a direct comparison between the two types. For Test Able, the point-•-aim CV was replaced by a CVL, as the U.SS. RANGER had been taken away fvr operation needs. Mod.iAcations for Both Tests Sketches No. 8 •Test Baker) and No. 9 (Test Able), dated 25 aruiaxy, incorporated two major changes. First, in order to avoid a cluster of. coral heads that would interfere seriouly with the desired placing of the target ships, the center of the array was shifted some distance southwest to an area much less densely populated by coral heads. Second, ships. on the 1,500 yard circle and within were intended to be moored bow and stern with a spare anchor abeam in order to have some assurance against the complications and uncontrolled damage which might result from a number of ships being adrift. There were two minor changes. First, ships of the center group for Test Baker were moved somewhat farther out tMan their original station. Although it was considered a prerequislte to sink these ships, it was felt that at this range the sinking would contribute nothing; because anything so close probably would be damaged beyond hope of 17 gainirg useW! knm7-edge. Seccndlyq. fTor Test AbJe, the comter groupbng shipso -= modifed to .failltteinstrumentation techniques aimed ai d ndarjndung shock wave veloc!ýy, and for both test~ships we:i'e added relatively close to the ntýen-,: m a lune t•oward Bikini to facilltae these mmaurements. Sketchec No. 10 (Test Baker) and No. 11 (Tent Abie), daied 28 jWnary,, ewnpriaed oly sflghi, modIfIcaticas of thti prevIotas Issues. For Test Able, the "Acation.s of thc center gra•p o Whips were cheaged aslghtly to achieve a more favorable L-tar get distibuition from the standpoint 4f random botabkr dispersiom. For Test Baker, locations were peovided ftor adi ships used in Test Able, contiagent upon ikeir survival of the first test. Sketches No. 12 (Test Baker) and No. 13 klTest Able), dated 31 january, were the result of a zOnfer &ace.tf Commaader joint Task Force One, his Deputy Task .4' .rce Comanaader, his adviser for Army Ground Forces, the M•1tlitax.r Advisory Board to the Communding General of the U mhattan District, General LeMay., a-ad representatives of the aurew:i of Ships and the Bureau of Ordnan;ce. The points raised primcipaJly camcered filling In the gaps that existed inside 1,000 yards ami praviding a more symmetrical distribution of targets by placing ships In the easterly sectors. .e specific points agreed pon were in=prated In .kel ch Nos. 12 and 13, and sent to various of the conferees for i ther study. Further Adjumen•ts Sketch No. 14 (Test Able), dated 8 February, was affected by several developments. First, the plan for bow and stern moniung of ships, with a spare anchor abeam. for ships at 1,500 yards o;- less, fell through hecaase cf technical dlffi- culties and shortage of ground tackle, so that plain anchoring had to be relied upo as nuicah as possible. )n this connection hwever, it was decided for Test Baker, to prcvide for droppIne a seco•i anchor with chain .looed&p in blgAtu to hold the ship in case the first chain parted. Secondly, more accurate saud consistent figures became available for the .Iar 18 blast p~roperties, and these su.pported a. demand f or even denser grouping of ships around the center, especill~y within 1,000 ya-'ds. 34 thios connection, Dr. W. G. Penney and Sir Geoffrey Maylor ýrooght forward specific proposals for placting, iajor clombatant ships In a sort. of pentagonal ar-rangerent -a~xoýfl the pc.Lt-ocf-alm. to traprove the range distribution under tlhe rta-ndom bombing dispersion expected. These pro~posals, which were subs'tantially acc eipted., condi.tioned the grouplng, esp-cially within about 1,000 yards. rhtirdly, although the Army Air Forces originally had desired an aircraft ci.,rrier as a po~nt-of -aim for the bombing plane, thiey proposed at this timne that the center ship should be the heaviest and most. resistant ship available. PENSYLVANLA was therefore shown in t-he cente~r position Ln Sketch No. 14C Finally, preliminary comments from, Army Air Forces suggested a. better spreading of chips to the north and east, and sugogested thiat the submarines be closed in to give a more rigorou~s testing of thos'e vessels; both of these suggestions were adopted, Sketch No. 15 (Test Baker), dated 8 February, followed the changes of Test Able respecting the submarines and the It Included landing craft fanned out to the north and east. minor adjustments around. the center as a consequence of abandoni~ng the mooring scheme previously mentioned. Mooring and Loadin Problems Sketch No. 16 (Test Able), dated 9 February, was an outgrowth of comapromnises resulting from an Army Air Force proposal. to pack shipis more closely around the center 'than would be practic~ablic from simnple considerations of mooring problems, A mooring scheme proposed by Rear AdmiJral F. G. Fahrion, USN, Commander Task Group 1.2j, war, adop'led. to permit the densest array practicable within 500 yards. B~ecause of the complexities of the moorings and the limiltations on groaind tackle su~pp .ly, ships beyond 500 yards were to remain anchored. At this time, NEVADA was substituted. becaw> for PENNSYLVANIA at the center of the array, 19 PENNSYLVANIA had some d:unage near the stern, from a torpedo hit suffered during the war and this had been repair.ý ed only by a temporary pat .h. The bas.c ,',irecLtie required gradation of damage from maximum to negligible, and it was therefore considered necesoary to place at least one battleship at a point where aamag4e would probably be slight, and another at an intermediat.- range. PENNSYLVANA was selected for the former location, NEW YORK for the latter. Up to this time the Bureau of Ships had proposed, with respect to the loading of the target vessels, t., provide sample loading of fuel and ammunition as a rieans of studying what effects these materials might have. In a discussion of this edition of the target array with the Military Advisory Board to the Commanding General of the Manhattan District, the representatives of the Manhatrtin District and Army Air Forces proposed full loading of both fuel and ammunition. The actual fuel and ammunition loadings used were the result of a compromise reached on this subject. The decision also was made to assign the lesser quantities to ships upwind in the array to reduce the darnage of a possible conflagration of fuel on the surface drifting down over the array. The loadings were carried over to the same ships in their position in At this time it ships of all types necessary work on the Test Baker array. was necessary to determine upon specific by name and location in order to enable target ships to proceed. Late Developments By the middle of February, the target arrays for both Tests Able and Baker were in a reasonably firm conditit a, and only minor changes had to be made before they reached their final form. Sketch No. 16A (Test Able), dated 1.5 Febru-. ary, showed SALT LAKE CITY and ARKANSAS moored with two anchors at the bow to permit their being closed in toward the center. Sketch No. 16B (Test Able) (20 February) showed a de- stroyer moved in somewhat closer than its original station 20 at 700 yards, SARATOGA anchored at about one mile, and another destroyer brought in from the rim of the array to about 1,500 yards. Sketch No. 11ý, dated 11 February, showed ARKANSAS and •SALT LAKE CrTY moored bvw and stern to enable the 1,000 y,.rd circle to be packed tight with ships, with additional destraycrs aad a=xillaries placed inside the circle. The submarines, ezoept PARCHE., were moved to the northeast quadrant to reduce the posslbihity of undue complications to their role In Test Baker from oil fires In the Lagoon. The line of destroyerx ifn the northwest sectr, was opened up in spacing to put the head of the string 200 yards closer in. This sketch was approved by the Idlit Chiefs of Staff for Test Able, but certain changes were later found necessary and approved. Final Target Array for Test Able The followhng changes from the approved sketch, were approved anrd Incorporated in the actual array o! ships used in Test Able:(a) Late in April, 1946, the Chief of Naval Operations requested the Commander Jolnt Task Force One to reduce the rnumber of ships inValved In Operation Crossroads to accomplsh the maximum practicable saving in personnel. Accordingly, it was decided that the following changes could be made without serious effezts on the value of the tesU.,:(1) Omit destroyers HELM and SMI=H, ard substitute for them LCT's 1013 and 705. These desfxoyers had bemn included In the array primarily to serve as "rain catchers" to collect samples of any fission products which might lall out of the atomic cloud In that down-wind sector of the array. It was decided that the LCT s could fill this role equally well. (2) Omit CLEBURNE (APA 13) a nd substitue GASCONADE (AP.P 85), thus saving one vessel as It was agreed that CLEBURNE could be omitted from Test Baker also without serious effect. 21 LT 388 was omitted because it was raeeed by TaAk IZ) Group 1.38, anc LS1" =0-waz transferred from a position on the beach to the former position of LST 388. (c) The following ýmbstitutioas were made becas~e af poor mterial condition of the vessels omited:(1) LST 361 ubatitted for LST 283. (2) LCT 1175 srbstitr.ed for LCT 845. (3) LCT 12S7 substituted for LCT 412. (d) MAYAWT was ubstitutd for FLU1IER because FLUSSER's machinery was ýn better conditim than MAYRANT's for use iu the destroyer patrol •M Able Day and Bakar Day. Final Target Array for Test Baker Sketch No. 15 became the approved array for Test Baker, a=uWt. to an -uderstandlng with the joint Chiefs of Staff that modifications would undoubtedly be necessary as a result of experience with Test Able, as well as for other reascns. At that time, Test Baker. was scheduled to be a surface shot, but Investigations were made cx the feasibility of firing this Ahbt below the surface. When it developed that this would be feasible without appreciable delay in the tests, agreement was general in favor of the underwater shot and a recommendation for this was submitted to the joint Chiefs of Staff and approved by them, At about the same time, a revised target array was submitted to the Joint Chiefs of Staff, with the following note on the plan:- "The array shown is the approved arroy for Test Baker In theit-ent Test Able will have been postpcned, and is the basic scheme to be adjusted as appropriate if Test Able will have been conducted"'. Tlids array as finally approved, included the following (a) To provide closer grouping near the center. (1) PENNSYLVANIA and SALT LAKE CITY were moved In chus requiring RALPH TALBOT to c 22 Ie be iýcved outward about 300 yards. (2) The positions of NAGATO, SAKAWA and INDE- PENDEWJC'E were changed to fill In as closely as possible * -ea within 1500 yards In the northeast sector. (b) To save personnel by reducing the number of ships, as requested by the Chief of Naval Operations. (1) FERG JS and CLEBURNE were omitted. (2) SMITH, HELM, and BAGLEY were omitted, with LCT 1013 and LCT 705 substituted for SMIYTE and HELM. (c) LST 133 was moved In from the beach to the former position of ST 220. (d) LmST 388 was omitted and 1,ST 220 substituted for it for the same reason as given above for Test Able. (e) ARKANSAS was moved at the request of the joint Chiefs of Staff. Changes Resulting from Test Aole After Test Able, a staff conference was held to discuss des•irale changes In the target layout for Test Baker. This conference was attended by the Joint Chiefs of Staff Evaluation Board and representatives of the Manhattan District, in addition to the regular attendance of the Staff. As a result of this conference, changes were recommended to the joint Chiefs of Stalff and were approved as follows:(a) Substitute MUSETIN for SAKAWA (Sunk In Test Able) on same bearkg. Replace MUSITIN by HUGHES, which was not in the original array. These changes provided another opportmnity for obtaining graduated damage on hulls of the same ype. (b) Interchange positions of RHIND and WILSON. it was thumg that RIND might have some weakening of structure from Test Able and a less lethal position was desired because of instrumentation carried on RHIND. (c) Interchange position of SALT LAKE CITY and INDEPENDENCE. INDEPENDENCE had severe damage above the waterline at the. stern, and afforded greater probability of furnishing useS~23 ful WInrmation with her bow presented toward the explosion. (d) Substitute BRULE, not originally in Test Baker, for GILLIAM.. sunk In Tsst Able. (e) Interchange positions of CRITTENDEN and DAWSON, for the same reason as In item (b) above. (f) Move GASCONADE to southwestward about 500 yards and place FALLON between BRULE and ARKANSAS, In order to provide better coverage of the area between the 500 yard and the 160 yard circles. (g) Substitute CONYNGHAM for ANDERSON, sunk in Test Able and place LCT 1115 in previous CONYNGHAM berth: leave LCT 810 1a Test Able position replacing LCT 1115, In order to utilize Instrumentation already Installed in LCT _16. Wh) Move PENSACOLA to bearing250", at original range, to permit moving the submarines APOGON, SKIPJACK, DENTUDA, SEARAVEN, and TUNA each f ward about 300 yards. Moor APOGON submerged at or bekow bomb depth. The other four submerged sabmarines were to remain at periscope depth. Place SKATE on surface bearilg about 220 degrees, range about 700 yards; the damage to topside structure and fitt•ns prevented monring SKATE submerged, although tite presmaue hull was sored. (i) Move SARATOGA nearer the outer limit of lethal area, thereby providing better graduation of distances between ARKAN- SAS, SARATOGA, NEVADA, NEW YORK and PENNSYLVANIA. ThLs also made it probable that SARATOGA would sink more slowly, pemittl•ng photographic studies of overall damage, particularly the behavior of the flight deck. 0) Place LST 125 on beach, In order to have the LST's represented among the beached landing craft. (k) Add LCT 818 at 1700 yards an bearing 0350 to provide additional Instrumentation desired %pecificallyin this loca- tion. Note: The originals of thevarious sketches referred to herein are available for study ii the Bureau of Ships, Code 424, and copies are also available In the files of the Historian, joint Task Force One. 24 PREP.ARA"IONS FOR THE TESTS There were a number of problems which Immediately confronted the Director of Ship Material as soon as various Army and Nawy groups were orgi'i zed under his commnand. The ships which had been made available by the Chief of Naval Operations as targets were scattered in oontinentai. and overseas naval shipyards, and it was necessary to obta-i firm information on their whereabouts. An overall pLan had to be made effecting an orderly distribution of these ships, among, different naval shipyards, as " e3Jr preparation would be a major task far beyond the capa.Lty of any single yard. In many cases considerable repair work would have tu be done to enable the ships to steam to Biliii and maintain themselves there. The location of instruments and test materials aboard the target ships would depend upon the positions of the ships in the target array, which was In a transitional state, undergoing frequent changes for military or technical reasons. The time limit was short to the point of urgency, with only about three months for preparing ships, materials, and instruments for the first test, which had been set for 15 May. All these interlocking "Tactors were operating simultaneously, and they increased the difficulty of what would have been In any case a naval construction task of the first magnitude. Assembling of Target Ships Prior to the Director of Ship Material's first staff conference on 22 January, the forces afloat had already sent out orders for all target ships to proceed to Pearl Harbor by 5 April. This was obviously going to create a serious bottleneck at Pearl Harbor; accordingly, the Director of Ship Material arranged for the cancellation of all previous sailing 25 ipy•.• rd2', ,s'o th. tthcf.y orders tc certain ships In continents.1 T:hb mightJ remain ain these shipyards and b•' reu red b.for. arriving at Pearl Harbor. It dev," ope'd th;A "tli th. mM or (o r.- batant sidps, were prepared at naval shipyards; on the wc••t Coast, with the exception of NEW YORK and PRINZ EUGEN., which were held in Philadelphia. Most of the non-targtc.t axiliaries were prepared in continental shrpy.aýrds, principally on the West Coast. Target destroyers, submarines, landing craft, and auxiliaries assembled at Pearl Harýbor. T2he Japanese battleship NAGATO and cruiser SAýAWA, originally scheduled for preparation at Pe'arl Harbor, were finally prepared by a repair ship at Bikini, after arriving there late in April following several changes in orders, Departure of Advance Unit.:. During the latter part of January and e,Febro.u-ry, tUhe' ... ship preparation units prepared detailed imrltructions, covering all types of target ships, which were 1.spatched to the ships themselves and the naval shipyards preparing tni 0 By the middle of February, this planning h.ld progre...sse-,d to the point where it was found desirable for the Director of Ship Material to send representatives to the v. orlou: sipyards to assist in the preparatory work and to inpe,- tie, ships. The first of these departed Washington on 8 Febru-ry to expedite non-target conversions on the Wet Cosr.;t; oiher'.; followed on 16 February to coordinate the:- destroy!:.': iary and landing craft program at Pearl Harbor. 1,3ter in February, representatives of the unit for combatant ships, comprising battleships, carriers, and crui.'.sers-, proceeded. to the West Coast, where officers were assign(-d to the variou:; naval shipyards preparing the major target.: hip•. J.ihe .ubmarine representatives left on 2 March for f'earl Harbor to assist in preparing the target submarines, 26 Crossroada Work on West Coast The senior Crossroads representative for the West Coast,, Captain Maxwell, organized his unit at the Naval shipyard at Terminal Island, after arriving there on 22 February. As additional personnel arrived from the Bureau of Ships Group in Washington, he appointed Crossroads representatives for the naval shipyards at Puget Sound and San Fran•cisco. These two shipyards were preparing PENNSYLVANIA and SARATOGA, respectively, and the remaining ships,, NEVADA, ARKANSAS, INDEPENDENCE, SALT LAKE CITY, and PENSACOLA, were at Terminal Island. Later work on PRINZ EUGEN was also done at Terminal Island. The first of a series of weekly conferences was held on 26 February with the commanding officers, or their representatives. of the West Coast target ships, as a means of explaining the nature of the tests, passing on instructions from the Bureau of Ships Group, and assisting in ship preparation work. On 5 March, Captain Creasor arrived at Terminal Island Naval Shipyard from Washington and commenced inspections of the target ships at West Coast yards and at Pear]. Harbor, particularly in regard to electrical plants and special electrical materials installed for the tests. As the yards completed the assigned preparatory work and the combatant ships proceeded to Pearl Harbor in early May, remaining West Coast representatives rejoined the staff in WHARTON at Oakland, California. Crossroads Work at Pearl Harbor Captain Bell, the senior Crossroads representative for Pearl Harbor, arrived there on 27 Fr bruary, along with Capt. E. W. Lamons, machinery assistant, and other staft personnel; and a conference was held on the same day with representatives of the naval shipyard, the Service Force of the Pacific Fleet, and the Army. All the target destroyers, submarines, landing cr-aft and auxiliaries had been assembled 27 at Pearl Harbor for preparation. The submarines were prepared at the submarine base under the direction of Commander Gaasterland, who arrived at Pearl Harbor on 4 March as head of the Crossroads submarine unit. Regular conferences were held with the commanding officers of destroyers and of auxiliaries and landing craft, which formed two groups of target ships being prepared at the naval shipyard. The Crossroads unit included special assistants for hull, machinery, electrical equipment, electronics, and ship measurements, plus a considerable number of Ships Instrumentation personnel, and representatives of the Bureau of Ordnance, Bureau of Aeronautics and Army Ground Groups. The Unit concluded this preparatory phase during the middle of May, when the target ships departed for Bikini, and the members of the unit assumed their assignment on the Director of Ship Material Staff in WHARTON. Postponement of Tests On 23 March, the Commander Joint Task Force One publicly announced that the tests had been postponed for six weeks by direction of the President of the United States and that the date of the first test, which had been scheduled for 15 May, would now be 1 July. In his conference on 20 March, the Director of Ship Material had informed his groups that all preparations were well in hand, with the departure date from Washington by special train set for 29 March. After the postponement, the Director of Ship Material held a special conference with his staff on 25 March to review the situation. Major target ships were being held on the West Coast. Sailing orders of WHARTON and other non-target ships had been cancelled. NAGATO and SAKAWA, instead of proceeding directly from Japan to Pearl Harbor, were being diverted to Eniwetok. A tentative interval between tests, Ad-ira) Solberg stated, was under stddy; and he directed his groups to make repor.ts on their estimate of how much time would be required between tests for th(xn to do their work. The effects of the po.7nponement were also discussed in another confer- 28 ence on 27 March. More time was now available for studying details of organization, making further preliminary Inspections, and submitting history material; meanwhile all work was to proceed without any slackening of effort. It was now possible to plan on a ten-day stopover in Pearl Harbor enroute to Bikini Atoll. The availability of many of the target ships would allow for considerable instrumentation work which otherwise would have had to be done under less favorable conditions in the target area, and would permit observers tn become familiar with the target ships. Preliminary IMnsections .by Grou Starting with the first visits to NEW YORK at Philadelphia Naval Shipyard in late janualy, heads of groups or their representatives made preliminary inspections of the progress of ship preparation work until the departure of the Director of Ship Material staff in May. The general purpose of these inspections was to insure that the ship preparation work was done in conformity with the detailed instructions of Annex W and special instructions contained in Director of Ship Material Memoranda. During the second week In March, the head of the Bureau of Aeronautics G.-3up, Captain Lonnquest, inspected SARATOGA and INDEIPENDENCE on the West Coast, as well as other target ships carrying aircraft. The executive officer of the Bureau of Ordnance Group, Commander Freedman, went to the West Coast around the middle of March to check the progress of ordnance work. The head of the Army Ground Group, Colonel Frederick, made inspections on the West Coast early in April of the loading of Army equipment on target ships. Captain Forest, representing the Bureau of Ships Group and the Director of Ship Material, made a last-minute inspection of target ships on the West Coast and at Pearl Harbor during the middle of April, not long before the staff was to depart from Washington. These preliminary inspections, along with numerous others which had been made, were to be supplemented by inspections of the target ships at Pearl Harbor; and then the last prelimi- 29 nary inspections could be made after the target fleet assembled in Bikini Lagoon. Departure of Staff from Washlngton The departure of the Director of Ship Matei lal staff, numbering about 200 personnel, by special train for the West Coast on 29 April, marked the end of the Washington phase of ship preparation work. From January through April, this work had been carried on by means of planning in Washington and execution of plans in Army and Navy field activities, principally naval shipyards. From now on planning would be closely integrated with the final preparations made on the target ships at Pearl Harbor and at Bikini. The tasks which lay ahead, apart from these last-minute preparations, would largely involve reorganization of the staff for operations in the target area, more preliminary inspections of the ships before the tests, rehearsal on Queen Day, and technical inspections subsequent to Able Day. After 6 May, when, WHARTON got underway from Oakland for Pearl Harbor with the Director of Ship Material groups aboard, a program was started for training inspection personnel and for acquainting staff members with the general aspects of the Operation Plan. Studies were made of the component parts of the target ships as compared with more modern vessels, of the organization of the inspection groups, and of the nature of the technical reports which would be required. Rear Echelon When the Task Force was first formed it had been envisioned that there would be a definite need for close liaison between the staff a- Bikini and the various Army and Navy parent organizations participating in the Task Force. To provIde this liaison, a duplicate staff, designated as Task Force One Rear Echelon, with members representing each 30 i:!. I i-f bo of the nominal positions and Pgroupsflncluid<,,t 'n j in en be at Bikini, was to remain in Waashington. Mýios"L of h bers worked with the groups they were to reprts(.nt diurixng the preparatory phase- and were cntirely feamiliaix with thc. operation. On 25 April, the Director of Ship Material held a cornerencq with members of his Rear Echelon Gtoup to o0tline the matters which would be handled in the rear -rxea and to emphasize the importance of conscientious and expeditious progressing of all such matters. Comdr. VJ W. Keller, who had been working with the Bureau of Ships Group, represented that Group and a-ted in the capacity of Director of Ship Material on the Rear Echelon staff. He was supported by Col, G,_ VI,. Trichel, who coordinated ail phases urader the Army Ground Group, Comdr. R, B. Heilig, wno progressed matters tiunder the cognizance of the Bureau of Ordnance).omdr- . K, IJ .,y. don, who acted for the Bureau of Aeronautics, and LL, S. H. Seal, who assisted for the Bureau of Medicine and Surgery, Each of these officers had staff members under thom in charge of particular phases of their work or repro.enting special units. Whern the staff departed on 29 April for Bikini, the Rear Echelon staff took over duties concerned with Crossroads in the Washington area. St__nover at Pearl Harbor The mo'xem ent of WHARTON has been synchronized wit}l', the movement )f t i? target ships so that the major comba1;,Jnt ships prpepareu on the West Cnast, as well as aux"!iaries, destroyers, landing craft -ýnd submarines, would be at PearV Harbor while th, staff of the Direckor of Ship Material w,3:5 there. Many of e target ships, including all the major ones, were available durin7 thE ?eriod 12 -22 May when WHARTON was berthed at Peari Harbor. Con Man 4- 1-: us=0 wI I.- a us l U 0 J0 .4-- ZW 0 ow 0a bi TA i x go Z on z ox- 400 - IL~ z IL 1-0 00 0 s I - a m .- 0 49 o 0 ao IL I- ha * 0 2 10 0 0 Z 0 me 1 z z 31 2 4 C9 3 z IL .44 U. I0 BUREAU OF SHIPS GROUP Formation of GrouD The Bureau of Ships Group was officially activated by the Bureau of Ships on 23 January. Rear Admiral T. A. Solberg was placed in charge of all activities of the Bureau of Ships relative to Operation Crossroads. His subsequent assignment to the Task Force as Director of Ship Material required that, in practice, the Bureau of Ships Group act as his executive agency, under the direction of Capt. L. A. Kniskern, so that thq Director of Ship Material would be able to carry out his responsibilities under the Deputy Task Force Commander for Technical Direction. The Bureau of Ships Group, with Captain Kniskern as head, worked directly under the Director of Ship Material. The material phases of the work of the Group were carried out by the section for Ship Preparation and Inspection, which had four main subsections, responsible for large target vessels, small target vessels, submarines, and non-targetvessels. Working in close association with Capt. F. W. Slaven and Capt. F. X. Forest, the heads of this section, were four special assistants for hull, machinery, electrical, electronics, with the head of the Electronics Group as the fourth assistant. In late January, Captain Forest became officer-in-charge of target ship preparation and inspection, with Capt. W. S. Maxwell as machinery assistant, Comdr. J. W. Roe as hull assistant, and Comdr. E. H. Batcheller as administrative assistant. Capts. R. C. Bell and E. W. Lamons became members of the Group about that time, and until their departure in mid-February to become Crossroads representatives at Pearl Harbor, assisted in the preparation of the general instructions to target ships. Comdr. C. L. Gaasterland reported late in January for the specialized work required in preparation of submarines and Capt. P. S. Creasor joined the Group in February as electrical assistant. 63 Several other officers were ordered to the Bureau duiiring the preparatory period to assist in the work of specialized uniL..% Some of them, after brief indoctrination in the various pnhase....of the project, proceeded to the different naval shipyards to progress ship preparations until re-assembly of the Grou,,., on the West Coast for departure for Bikini. Certain civi, .un specialists within the Bureau joined the staff on a part-tirm• basis and then became fulltime members of the Group upon departure from Washington. Although not required during ts.c. preparatory stages, the services of several specialists from naval shipyards were engaged well in advance for the pre- t.e and post-test inspection work at Bikini. These men, who were selected for particular employment with boilers, turbine's, pumps, cranes, and numerous electrical items, and specialt&NS such as welding, reported to the Group just prior to the departure of the staff from the West Coast. Late in March, an officer from Mare Island Naval Shipyard became a member of the Grou.p to study test effects on paint and chemicals, and two office', one from the Philadelphia Naval Material Inspection Office, tUin other from the Bureau, joined the Group to supervise expos.u-re and examination of navy 'uels and lubricants. One subsection on explosion phenomern, was maintained by means of close liaison with the head of the Ships Instrument'attion Group. Other subsections dealt with planning, progress, technical inspection, and naval architecture, The wbole organ>zation was kept fluid because of the necessity of accomplis.•hing much of its work in scattered naval shipyards, both in United States and Pearl. Harbor, and even the special assistants performed over-lapping duties in the field, as necessary. Whc(-i: the Director of Ship Material staff was reorganized enroate to Bikini Atoll, Captain Forest became head, of the Bureau. ot Ships Group, and other members of the group were assignea staff duties involved in the technical inspections. This entire group was embarked in WHARTON. Respofl ibili in executing the tasks assigned its parent organization, 64 N