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Date of visit:
April 1, 2000

For location of this site in NM, click on the map:
 Location of Trinity Site ...
 

We rate this site a:

Site Highlights:
 On White Sands range
 Open twice a year
 Well attended
 Military escort
 Few things to see
 Ground zero haunting
 Monolith photogenic
 Surrounded by nothing
 Many photographs
 McDonald Ranch

 Kachina

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Trinity Site
The Day The Sun Rose Twice
Dawn of a new era
Dawn of a new era
Trinity Site is where the first atomic bomb was tested at 5:29:45 a.m. Mountain War Time on July 16, 1945. The 19-kiloton explosion not only led to a quick end to the war in the Pacific but also ushered the world into the atomic age. All life on Earth has been touched by the event that took place here.

The 51,500-acre area was declared a national historic landmark in 1975. The landmark includes base camp, where the scientists and support group lived; ground zero, where the bomb was placed for the explosion; and the McDonald ranch house, where the plutonium core to the bomb was assembled.

The Manhattan Project
Trinity Site Marker
Trinity Site Marker
The story of Trinity Site begins with the formation of the Manhattan Project in June 1942.

The project was given overall responsibility for designing and building an atomic bomb.

At the time it was a race to beat the Germans who, according to intelligence reports, were building their own atomic bomb.

Under the Manhattan Project three large facilities were constructed. At Oak Ridge, Tenn., huge gas diffusion and electromagnetic process plants were built to separate uranium 235 from its more common form, uranium 238. Hanford, Wash. became the home for nuclear reactors that produced a new element called plutonium. Both uranium 235 and plutonium are fissionable and can be used to produce an atomic explosion.

Los Alamos was established in northern New Mexico to design and build the bomb. At Los Alamos many of the greatest scientific minds of the day labored over the theory and actual construction of the device. Dr. J. Robert Oppenheimer who is credited with being the driving force behind building a workable bomb by the end of the war led the group.

The Theory
Los Alamos scientists devised two designs for an atomic bomb--one using uranium 235 and another using plutonium. The uranium bomb was a simple design and scientists were confident it would work without testing. The plutonium bomb was more complex and worked by compressing the plutonium into a critical mass to sustain a chain reaction. The compression of the plutonium ball was to be accomplished by surrounding it with lense-shaped charges of conventional explosives. They were designed to all explode at the same instant. The force would be directed inward, thus smashing the plutonium from all sides.

In an atomic explosion, a chain reaction picks up speed as atoms split releasing neutrons plus great amounts of energy. The escaping neutrons strike and split more atoms, thus releasing still more neutrons and energy. In a nuclear explosion this all occurs in a millionth of a second with billions of atoms being split.

Project leaders decided a test of the plutonium bomb was essential before it could be used as a weapon of war. From a list of eight sites in California, Texas, New Mexico and Colorado, Trinity Site was chosen as the test site. The government already controlled the area because it was part of the Alamogordo Bombing and Gunnery Range, which was established in 1942. The secluded Jornada del Muerto was perfect as it provided isolation for secrecy and safety, but was still close to Los Alamos for easy commuting back and forth.

The Test Site
Basecamp
Basecamp
In the fall of 1944 soldiers started arriving at Trinity Site to prepare for the test. Marvin Davis and his military police unit arrived from Los Alamos at the site on Dec. 30, 1944.

The unit set up security checkpoints around the area and had plans to use horses to ride patrol. According to Davis the distances were too great so they resorted to jeeps and trucks for transportation.

JUMBO
Jumbo
Jumbo
The bomb design to be used at Trinity Site actually involved two explosions. First there would be a conventional explosion involving the TNT and then, a fraction of a second later, the nuclear explosion, if a chain reaction was maintained. The scientists were sure the TNT would explode, but were initially unsure of the plutonium. If the chain reaction failed to occur, the TNT would blow the very rare and dangerous plutonium all over the countryside.

Because of this possibility, Jumbo was designed and built. Originally it was 25 feet long, 10 feet in diameter and weighed 214 tons. Scientists were planning to suspend the bomb in the center of this huge steel jug because it could contain the TNT explosion if the chain reaction failed to materialize. This would prevent the plutonium from being lost. If the explosion occurred as planned, Jumbo would be vaporized.

Jumbo was brought to Pope, NM, by rail and unloaded. A specially built trailer with 64 wheels was used to move Jumbo the 25 miles to Trinity Site.

As confidence in the plutonium bomb design grew it was decided not to use Jumbo. Instead, Jumbo was placed under a steel tower about 800 yards from ground zero. The blast destroyed the tower, but Jumbo survived intact.

Today Jumbo rests at the entrance to ground zero so all can see it. The ends are missing because, in 1946, the Army detonated eight 500-pound bombs inside it. Because Jumbo was standing on end, the bombs were stacked in the bottom and the asymmetry of the explosion blew the ends off.

To calibrate the instruments, which would be measuring the atomic explosion, and to practice a countdown, the Manhattan Project scientists ran a simulated nuclear blast on May 7. They stacked 100 tons of TNT onto a 20-foot wooden platform just southeast of ground zero. Louis Hempelmann inserted a small amount of radioactive material from Hanford into tubes running through the stack of crates. The scientists hoped to get a feel for how the radiation might spread in the atomic test by analyzing this test. The explosion destroyed the platform, leaving a small crater with trace amounts of radiation.

The Bomb Assembly
Loading plutonium after assembly
Loading plutonium after assembly

Final assembly

Final assembly
On July 12 the two hemispheres of plutonium were carried to the George McDonald ranch house two miles from ground zero.

At the house, Brig. Gen. Thomas Farrell, deputy to Maj. Gen. Leslie Groves, was asked to sign a receipt for the plutonium.

Farrell later said, "I recall that I asked them if I was going to sign for it shouldn't I take it and handle it. So I took this heavy ball in my hand and I felt it growing warm. I got a certain sense of its hidden power. It wasn't a cold piece of metal, but it was really a piece of metal that seemed to be working inside. Then maybe for the first time I began to believe some of the fantastic tales the scientists had told about this nuclear power."

At the McDonald ranch house the master bedroom had been turned into a clean room for the assembly of the bomb core. According to Robert Bacher, a member of the assembly team, they tried to use only tools and materials from a special kit. Several of these kits existed and some were already on their way to Tinian, the island in the Pacific, which was the base for the bombers. The idea was to test the procedures and tools at Trinity as well as the bomb itself.

At one minute past midnight on Friday, July 13, the explosive assembly left Los Alamos for Trinity Site. Later in the morning, assembly of the plutonium core began. According to Raemer Schreiber, Robert Bacher was the advisor and Marshall Holloway and Philip Morrison had overall responsibility. Louis Slotin, Boyce McDaniel and Cyril Smith were responsible for the mechanical assembly in the ranch house. Later Holloway was responsible for the mechanical assembly at the tower.

In the afternoon of the 13th the core was taken to ground zero for insertion into the bomb mechanism.

The bomb was assembled under the tower on July 13. The plutonium core was inserted into the device with some difficulty. On the first try it stuck. After letting the temperatures of the plutonium and casing equalize the core slid smoothly into place. Once the assembly was complete many of the men took a welcome relief and went swimming in the water tank east of the McDonald ranch house.

The next morning the entire bomb was raised to the top of the 100-foot steel tower and placed in a small shelter. A crew then attached all the detonators and by 5 p.m. it was complete.

The Test
The test tower
The test tower
Three observation points were established at 10,000 yards from ground zero. None of the manned bunkers are left.

These were wooden shelters protected by concrete and earth. The south bunker served as the control center for the test. The automatic firing device was triggered from there as key men such as Dr. Robert Oppenheimer, head of Los Alamos, watched.

Many scientists and support personnel, including Gen. Groves, head of the Manhattan Project, watched the explosion from base camp, which was ten miles southwest of ground zero. All the buildings at base camp were removed after the test. Most visiting VIPs watched from Compania Hill, 20 miles northwest of ground zero.

The test was scheduled for 4 a.m. July 16, but rain and lightning early that morning caused it to be postponed. The device could not be exploded under rainy conditions because rain and winds would increase the danger from radioactive fallout and interfere with observation of the test. At 4:45 a.m. the crucial weather report came through announcing calm to light winds with broken clouds for the following two hours.

At 5: 10 a.m. the countdown started and at 5:29:45 the device exploded successfully (see archived photos.) To most observers the brilliance of the light from the explosion-watched through dark glasses - -overshadowed the shock wave and sound that arrived later.

Hans Bethe, one of the contributing scientists, wrote "it looked like a giant magnesium flare which kept on for what seemed a whole minute but was actually one or two seconds. The white ball grew and after a few seconds became clouded with dust whipped up by the explosion from the ground and rose and left behind a black trail of dust particles."

Joe McKibben, another scientist, said, "We had a lot of flood lights on for taking movies of the control panel. When the bomb went off, the lights were drowned out by the big light coming in through the open door in the back."

The heat they immediately felt impressed others. Military policeman Davis said, "The heat was like opening up an oven door, even at 10 miles." Dr. Phillip Morrison said, "Suddenly, not only was there a bright light but where we were, 10 miles away, there was the heat of the sun on our faces. Then, only minutes later, the real sun rose and again you felt the same heat to the face from the sunrise. So we saw two sunrises."

Visitors sometimes ask about soldiers watching the test from trenches. That took place during tests in Nevada, not at Trinity Site. Personnel were at least 10,000 yards from Ground Zero and they were in bunkers.

After the Explosion
All that remained
All that remained
Although no information on the test was released until after the atomic bomb was used as a weapon against Japan, people in New Mexico knew something had happened.

The shock wave broke windows 120 miles away and was felt by many at least 160 miles away. Army officials simply stated that a munition storage area had accidentally exploded at the Alamogordo Bombing Range.

The explosion did not make much of a crater. Most eyewitnesses describe the area as more of a small depression instead of a crater. The heat of the blast vaporized the steel tower (above) and melted the desert sand and turned it into a green glassy substance. It was called Trinitite and small pieces can still be seen in the area. At one time Trinitite completely covered the depression made by the explosion. Afterwards the depression was filled and much of the Trinitite was taken away by the Nuclear Energy Commission.

To the west of the monument is a low structure, which is protecting an original portion of the crater area. Trinitite is visible through openings in the roof.

The Schmidt House
The Schmidt house
The Schmidt house
The George McDonald ranch house sits within an 85' x 85' low stone wall. Franz Schmidt, a German immigrant, built the house in 1913.

The McDonalds constructed an addition on the north side in the 1930's. A display about the Schmidt family is in the house during each open house.

The ranch house is a one-story, 1,750 square foot building. It is built of adobe, which was plastered and painted. An icehouse is located on the West Side along with an underground cistern, which stored rainwater running off the roof. At one time the north addition contained a toilet and bathtub which drained into a septic tank northwest of the house.

There is a large, divided water storage tank and a Chicago Aeromotor windmill east of the house. The scientists and support people used the north tank as a swimming pool during the long hot summer of 1945. South of the windmill are the remains of a bunkhouse and a barn which was part garage. Further to the east are corrals and holding pens. The buildings and fixtures east of the house were stabilized to prevent further deterioration.

The ranch was abandoned in 1942 when the Alamogordo Bombing and Gunnery Range took over the land to use in training World War 11 bombing crews. The house stood empty until the Manhattan Project support personnel arrived in early 1945.

Inside the house the northeast room (the master bedroom) was designated the assembly room. Workbenches and tables were installed. To keep dust and sand out of instruments and tools, the windows were covered with plastic. Tape was used to fasten the edges of the plastic and to seal doors and cracks in the walls.

The explosion, only two miles away, did not significantly damage the house. Most of the windows were blown out, but the main structure was intact. Years of rainwater dripping through holes in the roof did much more damage. The barn did not do as well. During the Trinity test the roof was bowed inward and some of the roofing was blown away. The roof has since collapsed.

The house stood empty and deteriorating until 1982 when the U.S. Army stabilized the house to prevent any further damage. Shortly after, the Department of Energy and U.S. Army provided the funds for the National Park Service to completely restore the house. The work was done in 1984. All efforts were directed at making the house appear as it did on July 12, 1945 when the house was used in the assembly process.

Afterwards
The story of what happened at Trinity Site did not come to light until after the second atomic bomb was exploded over Hiroshima, Japan, on August 6. President Truman made the announcement that day. Three days later, August 9, the third atomic bomb devastated the city of Nagasaki, and on August 14 the Japanese surrendered.

Trinity Site became part of what was then White Sands Proving Ground. The proving ground was established on July 9, 1945 as a test facility to investigate the new rocket technology emerging from World War 11. The land, including Trinity Site and the old Alamogordo Bombing Range, came under the control of the new rocket and missile testing facility.

At first Trinity Site was encircled with a fence and radiation-warning signs were posted. The site remained off limits to military and civilian personnel of the proving ground and closed to the public.

In 1952 the Atomic Energy Commission let a contract to clean up the site. Much of the Trinitite was scraped up and buried. In September 1953 about 650 people attended the first Trinity Site open house. A few years later a small group from Tularosa visited the site on the anniversary of the explosion to conduct a religious service and prayers for peace. Similar visits have been made annually in recent years on the first Saturday in October.

In 1967 the inner oblong fence was added. In 1972 the corridor barbed wire fence which connects the outer fence to the inner one was completed. Jumbo was moved to the parking lot in 1979.

Trinity Site open houses are now conducted in April and October because it is generally very hot on the Jornada del Muerto in July.

The Project Patch
The Project Patch
Project Patch
The background of the patch was blue which represented the universe. A white cloud and a lightning bolt form a question mark which symbolizes the unknown results and the secrecy surrounding the project. The lightning bolt extends down to split a yellow atom, which represents atomic fission and the expected success of the test.

A red and blue star in the center of the question mark is the insignia for the Army Service Forces to which soldiers working on the Manhattan Project were assigned.

Site Gallery -At Trinity Site
 
A cloudy day On to ground zero Ground zero
A cloudy day Ground zero Ground zero
All that remains The shelter The shelter
Trinitrite A fair warning The McDonald ranch
The McDonald ranch The McDonald ranch The McDonald ranch
The McDonald ranch Last view by Jumbo
The day the sun rose twice
 
 
For More Information
White Sands Missile Range (use link to go to Public Affairs)

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