Chapter 1

INTRODUCTION

Project TRINITY was the name given to the war-time effort to produce the first nuclear detonation. A plutonium-fueled implosion device was detonated on 16 July 1945 at the Alamogordo Bombing Range in south-central New Mexico.

Three weeks later, on 6 August, the first uranium-fueled nuclear bomb, a gun-type weapon code-named LITTLE BOY, was detonated over the Japanese city of Hiroshima. On 9 August, the FAT MAN nuclear bomb, a plutonium-fueled implosion weapon identical to the TRINITY device, was detonated over another Japanese city, Nagasaki. Two days later, the Japanese Government informed the United States of its decision to end the war. On 2 September 1945, the Japanese Empire officially surrendered to the Allied Governments, bringing World War II to an end.

In the years devoted to the development and construction of a nuclear weapon, scientists and technicians expanded their knowledge of nuclear fission and developed both the gun-type and the implosion mechanisms to release the energy of a nuclear chain reaction. Their knowledge, however, was only theoretical. They could be certain neither of the extent and effects of such a nuclear chain reaction, nor of the hazards of the resulting blast and radiation. Protective measures could be based only on estimates and calculations. Furthermore, scientists were reasonably confident that the gun-type uranium-fueled device could be successfully detonated, but they did not know if the more complex firing technology required in an implosion device would work. Successful detonation of the TRINITY device showed that implosion would work, that a nuclear chain reaction would result in a powerful detonation, and that effective means exist to guard against the blast and radiation produced.

1.1 HISTORICAL BACKGROUND OF PROJECT TRINITY

The development of a nuclear weapon was a low priority for the United States before the outbreak of World War II. However, scientists exiled from Germany had expressed concern that the Germans were developing a nuclear weapon. Confirming these fears, in 1939 the Germans stopped all sales of uranium ore from the mines of occupied Czechoslovakia. In a letter sponsored by group of concerned scientists, Albert Einstein informed President Roosevelt that German experiments had shown that an induced nuclear chain reaction was possible and could be used to construct extremely powerful bombs (7; 12)*.

* All sources cited in the text are listed alphabetically in the reference list at the end of this volume. The number given in the text corresponds to the number of the source document in the reference list.

In response to the potential threat of a German nuclear weapon, the United States sought a source of uranium to use in determining the feasibility of a nuclear chain reaction. After Germany occupied Belgium in May 1940, the Belgians turned over uranium ore from their holdings in the Belgian Congo to the United States. Then, in March 1941, the element plutonium was isolated, and the plutonium-239 isotope was found to fission as readily as the scarce uranium isotope, uranium-235. The plutonium, produced in a uranium-fueled nuclear reactor, provided the United States with an additional source of material for nuclear weapons (7; 12).

In the summer of 1941, the British Government published a report written by the Committee for Military Application of Uranium Detonation (MAUD). This report stated that a nuclear weapon was possible and concluded that its construction should begin immediately. The MAUD report, and to a lesser degree the discovery of plutonium, encouraged American leaders to think more seriously about developing a nuclear weapon. On 6 December 1941, President Roosevelt appointed the S-1 Committee to determine if the United States could construct a nuclear weapon. Six months later, the S-1 Committee gave the President its report, recommending a fast-paced program that would cost up to $100 million and that might produce the weapon by July 1944 (12).

The President accepted the S-1 Committee's recommendations. The effort to construct the weapon was turned over to the War Department, which assigned the task to the Army Corps of Engineers. In September 1942, the Corps of Engineers established the Manhattan Engineer District to oversee the development of a nuclear weapon. This effort was code-named the "Manhattan Project" (12).

Within the next two years, the MED built laboratories and production plants throughout the United States. The three principal centers of the Manhattan Project were the Hanford, Washington, Plutonium Production Plant; the Oak Ridge, Tennessee, U-235 Production Plant; and the Los Alamos Scientific Laboratory in northern New Mexico. At LASL, Manhattan Project scientists and technicians, directed by Dr. J. Robert Oppenheimer,* investigated the theoretical problems that had to be solved before a nuclear weapon could be developed (12).

* This report identifies by name only those LASL and MED personnel who are well-known historical figures.

During the first two years of the Manhattan Project, work proceeded at a slow but steady pace. Significant technical problems had to be solved, and difficulties in the production of plutonium, particularly the inability to process large amounts, often frustrated the scientists. Nonetheless, by 1944 sufficient progress had been made to persuade the scientists that their efforts might succeed. A test of the plutonium implosion device was necessary to determine if it would work and what its effects would be. In addition, the scientists were concerned about the possible effects if the conventional explosives in a nuclear device, particularly the more complex implosion-type device, failed to trigger the nuclear reaction when detonated over enemy territory. Not only would the psychological impact of the weapon be lost, but the enemy might recover large amounts of fissionable material.

In March 1944, planning began to test-fire a plutonium-fueled implosion device. At LASL, an organization designated the X-2 Group was formed within the Explosives Division. Its duties were "to make preparations for a field test in which blast, earth shock, neutron and gamma radiation would be studied and complete photographic records made of the explosion and any atmospheric phenomena connected with the explosion" (13). Dr. Oppenheimer chose the name TRINITY for the project in September 1944 (12).

1.2 THE PROJECT TRINITY SITE

The TRINITY site was chosen by Manhattan Project scientists after thorough study of eight different sites. The site selected was an area measuring 29 by 39 kilometers* in the northwest corner of the Alamogordo Bombing Range. The Alamogordo Bombing Range was located in a desert in south-central New Mexico called the Jornada del Muerto ("Journey of Death"). Figure 1-1 shows the location of the bombing range. The site was chosen for its remote location and good weather and because it was already owned by the Government. MED obtained permission to use the site from the Commanding General of the Second Air Force (Army Air Forces) on 7 September 1944 (12). Figure 1-2 shows the TRINITY site with its major installations.

* Throughout this report, surface distances are given in metric units. The metric conversion factors include: 1 meter = 3.28 feet; 1 meter = 1.09 yards; and 1 kilometer = 0.62 miles. Vertical distances are given in feet; altitudes are measured from mean sea level, while heights are measured from surface level, unless otherwise noted.

Ground zero for the TRINITY detonation was at UTM coordinates 630266.** Three shelters, located approximately 9,150 meters (10,000 yards) north, west, and south of ground zero, were built for the protection of test personnel and instruments. The shelters had walls of reinforced concrete and were buried under a few feet of earth. The south shelter was the Control Point for the test (12). The Base Camp, which was the headquarters for Project TRINITY, was located approximately 16 kilometers southwest of ground zero. The principal buildings of the abandoned McDonald Ranch, where the active parts of the TRINITY device were assembled, stood 3,660 meters southeast of ground zero. Seven guard posts, which were simply small tents or parked trucks like the ones shown in figures 1-3 and 1-4, dotted the test site (9).

** Universal Transverse Mercator (UTM) coordinates are used in this report. The first three digits refer to a point on an east- west axis, and the second three digits refer to a point on a north-south axis. The point so designated is the southwest corner of an area 100 meters square.

1.3 THE PROJECT TRINITY ORGANIZATION

The organization that planned and conducted Project TRINITY grew out of the X-2 Group. LASL, though administered by the University of California, was part of the Manhattan Project, supervised by the Army Corps of Engineers Manhattan Engineer District. The chief of MED was Maj. Gen. Leslie Groves of the Army Corps of Engineers. Major General Groves reported to both the Chief of Engineers and the Army Chief of Staff. The Army Chief of Staff reported to the Secretary of War, a Cabinet officer directly responsible to the President. Figure 1-5 outlines the organization of Project TRINITY.

The director of the Project TRINITY organization was Dr. Kenneth Bainbridge. Dr. Bainbridge reported to Dr. J. Robert Oppenheimer, the director of LASL. A team of nine research consultants advised Dr. Bainbridge on scientific and technical matters (3).

The Project TRINITY organization was divided into the following groups (3):

o The TRINITY Assembly Group, responsible for assembling and arming the nuclear device

o The TR-1 (Services) Group, responsible for construction, utilities, procurement, transportation, and communications

o The TR-2 Group, responsible for air-blast and earth-shock measurements

o The TR-3 (Physics) Group, responsible for experiments concerning measurements of ionizing radiation

o The TR-4 Group, responsible for meteorology

o The TR-5 Group, responsible for spectrographic and photographic measurements

o The TR-6 Group, responsible for the airblast-airborne condenser gauges

o The TR-7 (Medical) Group, responsible for the radiological safety and general health of the Project TRINITY participants.

Each of these groups was divided into several units. Individuals were also assigned special tasks outside their groups, such as communications and tracking the TRINITY cloud with a searchlight (3).

1.4 MILITARY AND CIVILIAN PARTICIPANTS IN PROJECT TRINITY

From March 1944 until the beginning of 1946, several thousand people participated in Project TRINITY. These included not only the LASL scientists, but also scientists, technicians, and workmen employed at MED installations throughout the United States. According to entrance logs, film badge data, and other records, about 1,000 people either worked at or visited the TRINITY site from 16 July 1945 through 1946 (1; 3; 8; 15; 16).

Although supervised by Major General Groves and the Army Corps of Engineers, many Manhattan Project personnel were civilians. Military personnel were assigned principally to support services, such as security and logistics, although soldiers with special skills worked with the civilians (7; 12). Most of the military personnel were part of the Army Corps of Engineers, although Navy and other Army personnel were also assigned to the project (4; 12).