MANHATTAN PROJECT

The Manhattan Project was a program of research undertaken during WWII to produce the first nuclear weapons. It was led by the US in collaboration with the United Kingdom and Canada. From 1942-1946, the project was under the direction of Major General Leslie Groves of the U.S. Army Corps Engineers. Nuclear physicist J. Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the bombs. The Army component was designated the Manhattan District, as its first headquarters. Formally Known as Development of Substituted Materials. The project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project grew rapidly and employed nearly 130,000 people and cost nearly $2 billion at the time. Over 90% of the cost was for building factories and produce fissile material, with less than 10% for development and production. Research also took place at more than 30 sites across the US, UK, and Canada.

Manhattan Creation

American scientists, took steps in 1939 to organize a project to exploit the newly recognized fission process for military purposes. The first contact with the government was made by G.B. Pegram of Columbia University, who arranged a conference between Enrico Fermi and the Navy Department in March 1939. In the summer of 1939, Albert Einstein was persuaded by his fellow scientists to use his influence to present the military potential of an uncontrolled fission reaction chain to President Franklin Roosevelt. In February 1940, $6,000 was made available to start research under the supervision of a committee headed by L.J. Briggs, director of the National Bureau of Standards. On December 6, 1941, the project was put under the direction of the Office of Scientific Research and Development.

After the U.S. entered WWII, the War Department was given partial responsibility for the project, because by mid-1942 a vast array of pilot plants, laboratories, and manufacturing facilities would have to be constructed by the U.S Army Corps Engineers. In June 1942 the Corps of Engineers’ Manhattan District was initially assigned management of the construction work and in September 1942 Brig. Gen. Leslie Groves was placed in charge of all Army activities (chiefly engineering activities) relating to the project. the “Manhattan Project” became the code name for research work that would extend across the country.

Manhattan Project Expansion

It was known in 1940, German scientists were working on a similar project and that the British were also exploring the problem. In fall of 1941, Manhattan Project chemist Harold C. Urey accompanied Pegram to England in attempt to set up a cooperative effort. By 1943 a combined policy committee was established with Great Britain and Canada. In that year, a number of British and Canadian scientists moved to the US to join the project.

If the project were to achieve timely success, several lines of research and development had to be carried on simultaneously before it was certain whether any might succeed. The explosive materials then had to be produced suitable for use in an actual weapon.

Uranium Methods

Uranium-235, the essential fissionable component of the postulated bomb, cannot be separated from its natural companion. The more abundant uranium-238 by chemical means. The atoms of these respective isotopes must be separated from each other by physical means. Several physical methods to do this were intensively explored, and two were chosen—the electromagnetic process developed at the University of California, Berkeley, under Ernest Orlando Lawrence and the diffusion process developed under Urey at Columbia University. Both of these processes, particularly the diffusion method, required large, complex facilities and huge amounts of electric power to produce even small amounts of separated uranium-235. Philip Hauge Abelson developed a third method called thermal diffusion, which was also used for a time to effect a preliminary separation. These methods were put into production at a 70-square-mile track near Knoxville, Tn., formally known as Clinton Engineer Works, later as Oak Ridge.

Plutonium Method

Only one method was available for the production of the fissonable material plutonium-239. It was developed at the metallurgical laboratory of the University of Chicago under the direction of Arthur Holly Compton and involved the transmutation in a reactor pile of uranium-238. In December 1942 Fermi finally succeeded in producing and controlling a fission chain reaction in this reactor pile at Chicago.

Large production of plutonium-239 required the construction of a reactor of great size and power that would release about 25,000 kilowatt-hours of heat for each gram of plutonium produced. This requires the development of chemical extraction procedures that would work under conditions never before encountered. An intermediate step in putting this method into production was taken with the construction of a medium-size reactor at Oak Ridge. The large-scale production reactors were built on an isolated 1,000-square-mile tract on the Columbia River north of Pasco, Washington-the Hanford Engineer works.

Manhattan Project Theories

Before 1943, work on the design of the bomb itself was largely theoretical. Based on fundamental experiments carried out at a several different locations. The laboratory in Los alamos, New Mexico, was tasked with developing methods to reduce the fissionable products of the production plants to pure metal and fabricate the metal to required shapes. Methods of rapidly bringing together amounts of fissionable material to achieve a supercritical mass (nuclear explosion) had to be devised. Along with the actual construction of a deliverable weapon that would be dropped from a plane and fused to detonate at the right time, in the air above the target. Most of these problems had to be solved before any appreciable amount of fissionable material could be produced, so that the first adequate amounts could be used at the fighting front with minimum delay.

By the summer of 1945, amounts of plutonium-239 sufficient to produce a nuclear explosion had become available from the Hanford Works, and weapon development and design were sufficiently advanced so that an actual field test of a nuclear explosive could be scheduled. Because such a test was no simple affair. Elaborate and complex equipment had to be assembled to provide a complete diagnosis of success or failure. By this time the original $6,000 authorized for the Manhattan Project had grown to $2 billion.

First Atomic Bombs

The first atomic bomb was exploded on July 16, 1945, at the Alamogordo’s air base. Oppenheimer had called the site “Trinity” in reference to one of John Donne’s Holy Sonnets. The bomb, a plutonium implosion device called Gadget, was raised to the top of a 100ft steel tower called “Zero”. The area at the base of the tower was marked “Ground Zero,”. The tower was surrounded by scientific equipment, with remote monitoring taking place in bunkers occupied by scientists just yards way. The explosion came as an intense light flash, a sudden wave of heat, and a tremendous roar as the shock wave passed through the valley. A ball of fire rose rapidly, followed by a mushroom cloud. The bomb generated an explosive power equivalent to 15,000-20,000 tons of trinitrotoluene (TNT). The tower was completely vaporized and the surrounding desert surface fused to glass for a radius of 800 yards.

The following month, two other atomic bombs produced by the project. The first using uranium-235 and the second using plutonium, were dropped on the Japanese cities of Hiroshima and Nagasaki. Neither city had been attacked during the U.S. strategic bombing campaign until that point. Planners wished to demonstrate the destructive power of the bombs. Hiroshima was selected as the primary target because of its military value. It was the headquarters of the Japanese Second Army. On August 6, 1945, a U.S. B-29 Bomber released a gun assembly fission bomb-dubbed Little Boy-above Hiroshima. The weapon detonated at an altitude of 1,900ft. The explosive yield was estimated to be the equivalent of 15,000 tons of TNT. Some 70,000 people were killed instantly. However, By the end of the year the death toll had surpassed 100,000. Two-thirds of the city was destroyed.

Fat Man

By the morning of August 9, 1945, the Soviet Union had declared war on Japan. But the Japanese government had not yet communicated its intent to surrender to the allies. A B-29 carrying Fat Man, similar to “Gadget”, was initially dispatched to Kokura. Thick clouds and haze prevented the bombardier from sighting the designated aimpoint. However the bomber proceeded to its secondary target, Nagasaki.

At 11:02 AM Fat Man exploded at an altitude of 1,650ft northwest of the city. It detonated with the explosive force of 21,000 tons of TNT. An estimated 40,000 people were killed instantly. At least 30,000 more would die from their injuries and radiation poisoning by the end of the year. About 40% of the city’s buildings were completely destroyed. Due to the area’s uneven terrain, a significant part of Nagasaki, was relatively untouched. The Japanese initiated surrender the next day. By this point, Groves had notified U.S. Pres. Harry S. Truman, that another bomb would be ready within a week.

On September 2, 1945, a Japanese delegation signed formal surrender documents on the deck of the USS Missouri. Shortly after the conclusion of hostilities, Manhattan Project physicist Philip Morrison traveled to Hiroshima at the request of the War Department to study the effects of the atomic bomb. Characterizing the bomb as “preeminently a weapon of saturation,” he said, “It destroys so quickly and so completely such a large area that defense is hopeless.” Horrified by what he had witnessed, Morrison would spend the rest of his life campaigning against nuclear weapons and a potential “third bomb.”

Operations Crossroads

First Test

After the war, the Manhattan Project oversaw Operation Crossroads, a military-scientific experiment conducted at Bikini Atoll in the South Pacific in 1946. “Able,” the first peacetime atomic weapons test, was carried out in July of 1946. In attendance were some 42,000 U.S. military personnel, as well as journalists and representatives from a dozen countries. A 20-kiloton atomic bomb was dropped from a B-29 and exploded at an altitude of about 520ft over a fleet of about 80 decommissioned WWII naval vessels. Only five ships were sunk by the blast, and, although several more were damaged, the majority survived the explosion.

Within a day, radiation levels had subsided enough for the ships to be boarded and inspected. Press and foreign military observers seemed underwhelmed that the blast had not vaporized the assembled ships. But such an appraisal discounted the debilitating effect that radiation would have had on a ship’s crew. Many test animals placed throughout the fleet suffered from radiation sickness. Confirming a prediction in the Bulletin of the Atomic Scientists that “a large ship, about a mile away from the explosion, would escape sinking, but the crew would be killed by the deadly burst of radiations from the bomb, and only a ghost ship would remain.

Second Test

The second test, “Baker,” took place in July of 1946. A 23-kiloton device was suspended at a depth of 9ft from a decommissioned landing craft in the Bikini lagoon. At the moment of explosion, a luminous dome rose on the surface, followed by an opaque cloud that surrounded half the target area. The cloud dissipated within seconds, revealing a column of ascending water that lifted the 26,000 ton battleship, USS Arkansas, into the air. The column of water, rose to a height of 1 mile, sending spray still higher. The expanding column of spray engulfed about half the ships in the targeted area with radioactive water. Waves traveling outward were up to 100ft tall.

The evaluation board of the Joint Chiefs of Staff reported that the explosion had produced intense radioactivity in the waters of the lagoon. Four days after the test, the waters where still so lethal, that any useful length of time in the area was considered unsafe.  Because of persistent radiation and the difficulty of decontamination led to the cancellation of “Charlie,” a planned third test that would have involved a bomb being detonated at the bottom of the Bikini lagoon.

Manhattan Project – The End

Since the conclusion of Operation Crossroads, the Manhattan District relinquished direction of the plants under its jurisdiction to the U.S. Atomic Energy Commission (AEC). Under the AEC, weapon testing continued along with development of the peaceful uses of atomic energy. The U.S. government disbanded the AEC under the Energy Reorganization Act of 1974 and divided its functions between two new agencies: the Nuclear Regulatory Commission , which regulates the nuclear power industry, and the Department of Energy.