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Detonation of the First Atomic Bomb at the Trinity Site, 1945

By Michael Ann Sullivan

On 16 July 1945 the U.S. Army and civilian scientists attached to the Manhattan Engineering District detonated the first atomic device in the New Mexico desert at Trinity Site, a remote location sixty miles northwest of Alamogordo. At 5:30 am in the morning a brilliant fireball rose into the air and lit the pre-dawn sky with the brightness of sunrise. A mushroom shaped cloud billowed 38,000 feet into the air and all animal and plant life vaporized from the site. Despite this awesome sight, few people, other than those involved in the test, witnessed the blast and those that did failed to guess at its significance. Newspaper coverage that day did not enlighten the public. Pre-wrote press releases claimed that an ammunition magazine accidentally exploded on the Alamogordo Air Base.

The Trinity test affirmed Manhattan Project scientists’ efforts to develop an atomic weapon ahead of the Germans during World War II (WWII). The United States entered the field of atomic research at the urging of Albert Einstein and Leo Szilzard two émigré physicists that escaped Nazi Germany. In 1939, Einstein and Szilzard wrote a letter to President Franklin Delano Roosevelt warning him about German research into nuclear fission and its possible uses. Roosevelt responded by creating an Advisory Committee on Uranium. The Uranium Committee funded the first U.S. atomic research.

After the Japanese attack at Pearl Harbor in 1941, the U.S. atomic program expanded rapidly. Roosevelt established a National Defense Research Committee (NDRC) and the Office of Scientific Research and Development (OSRD) to mobilize science for the war effort. In 1942, a NDRC report suggested that an atomic weapon could be developed in time to influence the outcome of the war. Roosevelt then created the Manhattan Engineering District (MED), a top-secret agency under the direction of General Leslie R. Groves to develop and produce an atomic bomb for use during the war. Groves immediately began selecting sites and personnel to conduct the research necessary to achieve this outcome. Groves picked Oak Ridge, Tennessee, and Hanford, Washington, as the locations for the production of nuclear materials. Groves demanded utter secrecy. Each facility of the Manhattan Project knew only what that site was working on and nothing else.

Groves met J. Robert Oppenheimer, a theoretical physicist, at the University of Berkeley, in October of 1942. Oppenheimer challenged Groves’ practice of compartmentalization and suggested the need for a central laboratory to combine all areas of research—“chemical, physical, metallurgic, engineering, and ordnance.” Groves agreed that a laboratory for research and development would be a boon to the project and selected Oppenheimer to lead it. Although an established and accomplished theoretical physicist, Oppenheimer had no previous administrative experience. Moreover, his left-leaning politics made many in Washington nervous. Nevertheless, Groves found Oppenheimer to be both brilliant and trustworthy and recommended him for the post. Oppenheimer accepted and began touring the country recruiting eminent scientists and engineers to work on the many problems associated with creating an atomic weapon. Many of the civilian scientists that accepted Oppenheimer’s proposal had escaped from Nazi Germany or other fascist regimes in Europe. The brightest minds in physics—Niels Bohr, Enrico Fermi, Emilio Segrè, Stanlislaw Ulum, Edward Teller, I. I. Rabi, Hans Bethe, and John von Nuemann agreed to join Oppenheimer in his new central laboratory.

Groves required a remote location for the facility, west of the Mississippi, and located in a natural bowl so that the perimeter could be fenced and guarded. Several sites in the Southwest were selected but neither suited Oppenheimer. He then suggested the Los Alamos Ranch School for Boys which he knew about from previous vacations in New Mexico. The government quickly appropriated the school and twenty-six other properties from local inhabitants. Combined with already government owned land, the Hill, as Los Alamos came to be called, eventually comprised some 9,000 acres. The M. M. Sundt Construction Company and the architectural firm of New Mexico state architect W.C. Kruger began immediately to transform the rustic boy’s school into a military base.

In early 1943 work began on the main MED mission—“to produce a practical military weapon in the form of a bomb”, or gadget, as the device began to be called, by the release of energy due to a “neutron chain reaction.” The Site Y (the code name for Los Alamos) scientists pursued two promising avenues of weapon development, a gun-type uranium enriched weapon (Little Boy) and an implosion plutonium weapon (Fat Man). The gun-type weapon operated simply by colliding two ends of a gun barrel, one with a detonator and the other with enriched uranium, causing a fission reaction and explosion. The plutonium weapon was more complex. It operated by detonating shaped conventional explosives surrounding a pit of plutonium. This explosion increasingly compressed the plutonium eventually causing a critical mass and a sustained nuclear chain reaction. Scientists felt assured that the Little Boy weapon would work without prior testing, but wanted to ascertain whether the Fat Man bomb would work as theorized.

Therefore, in the spring of 1944, just as Germany had surrendered, Oppenheimer, Groves, and Kenneth T. Bainbridge (selected to oversee the test) began to look for an appropriate site to test the implosion type weapon. The test site had to be close to Los Alamos yet remote from any population centers both for reasons of safety and secrecy. The search soon narrowed to three sites, the desert training area north of Rice, California, where General Patton had trained his troops, the rugged lava beds outside of Grants, New Mexico, and the northwest corner of the Alamogordo Air Base also located in New Mexico. The team selected the Bombing Range which lay within the historical region of the Jornada del Muerto, a desolate ninety-mile stretch of desert between present day Socorro and El Paso.

The “Route of the Dead Man” or “Journey of Death” plagued early Spanish settlers as its waterless trail claimed many lives. The route became an integral part of the Camino Real, the main road from Mexico City through El Paso, Texas and into New Mexico. However, well into the nineteenth century travelers cautioned one another to cross this desert with care. By the 1940s, the area still had few permanent residents. Only a small number of hardy ranchers made this barren region at the base of the Sierra Oscuro mountains their home. Much of the land was owned by the federal government and leased out for cattle and sheep grazing. The army leased privately owned land from ninety-seven families and moved them out for the duration. However, no one has ever been able to return to their homes and the U.S. Government eventually settled with everyone who owned property in the Jornada del Muerto. The David McDonald family protested the longest and loudest claiming the U.S. Army stole their land. McDonald even briefly re-occupied his property in 1982 until New Mexico representatives Senator Harrison Schmidt and Congressmen Joe Skeen effected a settlement between the federal government and McDonald.

Oppenheimer chose the code name Trinity to designate the 51,500 acre site within the Jornado del Muerto to test the gadget. Captain Samuel P. Davalos, an engineer from Los Alamos began transforming the McDonald Ranch and surrounding area into a suitable scientific test site for the first atomic experiment. Bainbridge situated Ground Zero 3,400 yards from the McDonald Ranch house which was retrofitted to accommodate the final assembly of the nuclear device. The Army Corps of Engineers built two control bunkers close to Ground Zero and the base camp was built six miles to the south. Davalos used CCC prefabricated buildings for barracks, a latrine, the mess hall, and a laboratory at the Trinity Base Camp. The buildings were transported from near Albuquerque and reassembled on site. Campaña Hill, an overlook north of Ground Zero, was chosen as a spot for VIPs to witness the results of the test. Initially, the site was built to house 160 men but at its height 300 men claimed the Trinity Site as their temporary home.

Test personnel began arriving in March of 1945. Everyday life at Trinity was rigorous and rustic. Buildings were constructed for strength not comfort. Summer temperatures were extreme and the environment dusty and dry. The only air conditioning was in the mess hall and workers only enjoyed it for an hour a day during lunch. As befit the history of the Jornada, water was at a premium. The existing wells produced water with extremely high gypsum content. Even the installation of water filters did little to improve its potability. Rattlesnakes, scorpions, and insects of all kinds constantly strayed into barracks and mess.

Technicians and scientists worked at a feverish pace to set the test up by the July deadline. The work day began at 5:00 am and continued until 3:00 pm. Work days lasting 18 hours were not uncommon. As the test date approached, the crew began to go without sleep in order to take care of last minute problems. In off hours men played pool, cards, volleyball, or hunted game to add variety to the menu. Weekly movies were shown outside, and horses originally brought to patrol the perimeter were used for playing polo. Most personnel except the scientists did not know what the purpose of their work was until the bomb exploded.

Scientists conducted a simulated explosion with conventional TNT two months before the actual test to calibrate all the equipment to be used in measuring the blast. 100 tons of TNT mounted on a 20 foot tall wooden platform was detonated on May 7th with a minute amount of radioactive material. The explosion left nothing but a crater and small trace amounts of radiation.

Babcock and Wilcox Steel Corporation of Barberton, Ohio, constructed a large banded steel cylinder to house the gadget. The purpose of the container, which Groves nicknamed Jumbo, was to preserve the expensive and rare plutonium if the bomb did not detonate. If the bomb worked as planned, then Jumbo would dissolve. However, as the test day approached scientists became more and more confident that the gadget would operate according to their calculations and abandoned the idea of using the container. Jumbo arrived by railroad and was placed 800 yards from Ground Zero. It survived the explosion and is the only visible evidence of the experiment left at Trinity Site.

On 12 July the testing team began to assemble the bomb. Workers converted a room in the McDonald ranch house into a clean room where scientists assembled the plutonium core of the bomb. Jack Hubbard, hired as the chief meteorologist, made weather forecasts and determined the most desirable conditions for the blast. Hubbard wished to schedule the test on a day with clear skies, high visibility, low humidity, and with light winds heading steadily away from the blast site. Instead international and military events determined the date of the test, and in regards to the weather, only the winds cooperated with the scientists that day.

On the day of the test at 5:10 am, the countdown for the Trinity test began as a spirited recording of the “Star Spangled Banner” played in the background. In preparation for the blast, men lay face down on the ground with their eyes covered and their hands over their faces. After the blast occurred, they were allowed to stand up and watch the explosion through a pair of welder’s glasses. At exactly 5:30 am the blast occurred as planned. Witnesses saw a blinding flash of light brighter than any witnessed to date in human history. The light was so bright, that Georgia Green, a young blind woman being driven to the University of New Mexico for her morning class along Highway 85, queried her brother-in-law about the flash. The blast created a flash, then a fireball, and lastly a mushroom shaped cloud that sucked thousands of tons of sand and dirt into its mouth. Heat accompanied the light and a tremendous shock wave followed the explosion. The atomic bomb vaporized all plant and animal life within a mile radius. The area was covered with smoke and the stench of death.

The other scientists and personnel witnessing the blast expressed a variety of emotions: relief, elation, awe, and trepidation. Later, when reporters interviewed Oppenheimer, he said he felt glad that the bomb worked. He also related that at the moment of detonation the lines from the Bhagavad Gita had run through his mind, “I am become Death, the destroyer of worlds.”

The successful testing of the gadget at Trinity gave the U.S. Army the go ahead to use atomic weapons to end the war. On 6 August 1945 the air force dropped Little Boy over Hiroshima, Japan killing 100,000 people and devastating the city. Three days later on 9 August 1945 an American bomber dropped Fat Man on Nagasaki killing 140,000 civilians and annihilating that city also. Japan surrendered unconditionally on 14 August 1945.

In 1965, the National Park Service asked Congress to make Trinity Site a National Historic Landmark. However, Trinity is inside the White Sands Missile Range and efforts to make it a tourist attraction seem unlikely. The Missile Range opens Trinity Site to the public twice a year in April and October.

Sources Used:

Groves, Leslie R. Now It Can Be Told: The Story of the Manhattan Project. New York: Harper and Row, 1962.

Hunner, Jon. Inventing Los Alamos: The Growth of an Atomic Community. Norman, Oklahoma: University of Oklahoma Press, 2004.

Lamont, Lansing. Day of Trinity. New York: Atheneum, 1965.

Loeber, Charles R. Building the Bombs: A History of the Nuclear Weapons Complex. Albuquerque, New Mexico: Sandia National Laboratories, 2002.

Merlan, Thomas. Life at Trinity Base Camp. Tularosa, NM: White Sands Missile Range, 2001.

Rhodes, Richard. The Making of the Atomic Bomb. New York: Simon and Schuster, 1986.

Szasz, Ference Morton. The Day the Sun Rose Twice: The Story of the Trinity Site Nuclear Explosion July 16, 1945. Albuquerque: University of New Mexico Press, 1984.