TRINITY TEST SITE

• Columbia University
• University of California, Berkeley
• The Dayton Project, 1943-1945
• The Dayton Project, 1945 and Beyond
• Bomb Casing and Drop Test Sites
• Trinity Test Site
• Tinian Island
• City of Hiroshima
• City of Nagasaki
• Uranium Mines
• Uranium Processing Facilities

Although confidence in the uranium gun-type design was high, doubt remained about the plutonium implosion device's effectiveness. The Los Alamos laboratory began considering a possible test in late 1943. In January 1944, General Leslie Groves reluctantly agreed to test the device as long as the plutonium could be recovered. The test would be a scaled-down explosion using a containment vessel. Los Alamos officials soon reconsidered this approach. Contending that performance would be easier to predict for a full-scale explosion, laboratory director J. Robert Oppenheimer in February recommended carrying out a full test in a remote location inside a containment vessel. Groves remained unenthusiastic but allowed the laboratory staff under the leadership of the Harvard physicist Kenneth T. Bainbridge to study the possibilities. for the test began in spring 1944.

Site selection Remote siting was a priority, with Los Alamos itself soon ruled out. Security dictated that any test blast not be too closely linked with the laboratory, and insufficient space existed on the mesa to accommodate a possible explosion in the kiloton range. Bainbridge scoured maps of the western United States searching for the optimum site. Appropriate distance from Los Alamos was important, far enough away to avoid ready linkage with the laboratory but close enough to allow for ease of travel back and forth. Proper terrain and climate were critical. The site needed to be flat with infrequent haze and light winds so that the blast would not be hindered and prevent accurate measurements. Desert areas were preferable so that storms and rainfall could be avoided. Security and safety both demanded an isolated and sparsely settled region. "The area had to be remote," Bainbridge later observed, "so that people could be evacuated in the event of a low-order detonation, which would distribute poisonous plutonium, or a high-level explosion, which would be accompanied by dangerous radioactive fallout."

Bainbridge and his site selection committee, which included Oppenheimer, initially considered eight different locations. Four sites were in New Mexico, two—the Tularosa and Jornada del Muerto valleys—in the arid southern part of the state, and two—the lava region south of Grants and the area southwest of Cuba and north of Thoreau—over the mountains to the west of the laboratory. Two sites were in California: on San Nicolas Island about seventy-five miles off the southern coast and at an Army tank training ground in the Mojave Desert near Rice. The remaining two sites were in the San Luis Valley near the Great Sand Dunes National Monument in southern Colorado and on a barrier island ten miles off the Texas Gulf Coast. After several exploratory expeditions, on one of which to the western New Mexico sites Oppenheimer participated in, Bainbridge and his committee narrowed the choices to either the California desert or the southern New Mexico valleys. Groves rejected the California location, reportedly because General George S. Patton was using the site and Groves refused to deal with him, and, in early September 1944, the Bainbridge committee settled on the Jornada del Muerto in the northwest corner of the Alamogordo Bombing Range about 100 miles south of Albuquerque.

Construction of a base camp at the Trinity site with barracks, officers' quarters, a mess hall, and other support facilities began in fall 1944. Construction accelerated in early 1945 with the building of warehouses, repair shops, bomb-proof structures, an explosives magazine, a stockroom to house equipment shipped from Los Alamos, an unloading platform on the railroad siding at Pope 25 miles west of the site, a commissary, and more barracks. Throughout May and June 1945 an entire laboratory grew in the desert, charged with designing a wide variety of instruments to measure various bomb effects and capture images of the explosion in progress. Instrumentation surrounding the site was tested with an explosion of a large amount of conventional explosives on May 7. Preparations were completed by the beginning of July. Three observation bunkers located 10,000 yards north, west, and south of the firing tower at ground zero measured key aspects of the reaction.

On July 12, the plutonium core was taken to the test area in an army sedan. The non-nuclear components left for the test site at 12:01 a.m., Friday the 13th. During the day on the 13th, final assembly of the "Gadget" (as it was nicknamed) took place in the nearby McDonald ranch house. By 5:00 p.m. on the 15th, the device had been assembled and hoisted atop the 100-foot firing tower. At precisely 5:30 a.m. on Monday, July 16, 1945, the device exploded over the New Mexico desert, vaporizing the tower and turning the asphalt around the base of the tower to green sand. Seconds after the explosion came a huge blast wave and heat searing out across the desert. The orange and yellow fireball stretched up and spread, a second column, narrower than the first, rose and flattened into a mushroom shape. The test was more efficient than expected, and little radioactive fallout initially dropped on the test site beyond 1,200 yards of ground zero. Most radioactivity was contained within the dense white mushroom cloud that topped out at 25,000 feet. Within an hour, the cloud had largely dispersed toward the north-northeast, all the while dropping a trail of fission products. Offsite fallout was heavy. Several ranch families, missed by the Army survey, received significant exposures in the two weeks following Trinity. The families, nonetheless, evidenced little external injury. Livestock were not as fortunate, suffering skin burns, bleeding, and loss of hair. Stafford Warren, the Manhattan District's chief medical officer, reported to Groves that "while no house area investigated received a dangerous amount, the dust outfall from the various portions of the cloud was potentially a very dangerous hazard over a band almost 30 miles wide extending almost 90 miles northeast of the site." The Alamogordo site, Warren concluded, was "too small for a repetition of a similar test of this magnitude except under very special conditions." For any future test, he proposed finding a larger site, "preferably with a radius of at least 150 miles without population." The Trinity test had been, as Warren informed Groves, something of a near thing.

You can read more about the Trinity test of July 16, 1945 here.

• Columbia University
• University of California, Berkeley
• The Dayton Project, 1943-1945
• The Dayton Project, 1945 and Beyond
• Bomb Casing and Drop Test Sites
• Trinity Test Site
• Tinian Island
• City of Hiroshima
• City of Nagasaki
• Uranium Mines
• Uranium Processing Facilities

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