American scientists, many of them
refugees from fascist
regimes in Europe, 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 and present the military potential of an uncontrolled fission chain
reaction to Pres. Franklin
D. 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 (later National
Institute of Standards and Technology). On December 6, 1941,
the project was put under the direction of the Office of Scientific Research
and Development, headed by Vannevar
Bush.
Groves, Leslie RichardLos Alamos National LaboratoryAfter
the U.S. entry into World
War II, the War Department was given joint responsibility for
the project, because by mid-1942 it was obvious that a vast array of pilot
plants, laboratories, and manufacturing facilities would have to be constructed
by the U.S. Army Corps of Engineers so that the assembled scientists could
carry out their mission. In June 1942 the Corps of Engineers’ Manhattan
District was initially assigned management of the construction work (because
much of the early research had been performed at Columbia
University, in Manhattan),
and in September 1942 Brig. Gen. Leslie
R. Groves was placed in charge of all Army activities
(chiefly engineering activities) relating to the project. “Manhattan Project”
became the code name for research work that would extend across the country.
It was known in 1940 that German scientists were working
on a similar project and that the British were also exploring the problem. In
the fall of 1941 Harold
C. Urey and Pegram visited England to attempt to set up a
cooperative effort, and by 1943 a combined policy committee with Great Britain
and Canada
was established. In that year a number of scientists of those countries moved
to the United States to join the project there.
If the project were to achieve success quickly, 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 and be made suitable for use in an actual weapon.
atomic bombEncyclopædia Britannica, Inc.Uranium-235,
the essential fissionable component of the postulated bomb, cannot be separated
from its natural companion, the much more abundant uranium-238,
by chemical means; the atoms of these respective isotopes
must rather 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, and 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 (180-square-km)
tract near Knoxville,
Tennessee,
originally known as the Clinton Engineer Works, later as Oak
Ridge.
nuclear chain reaction: scientists observing the
world’s first self-sustaining nuclear chain reaction, in Chicago, 1942National Archives and Records Administration (ARC
Identifier 542144)Only one method was available for the
production of the fissionable 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.
Quantity 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. It involved
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 (2,600-square-km) tract on the Columbia
River north of Pasco,
Washington—the Hanford
Engineer Works.
Groves, Leslie Richard: Groves and Openheimer
working on the Manhattan ProjectMarie Hansen—Time Life Pictures/Getty ImagesBefore
1943, work on the design and functioning of the bomb itself was largely
theoretical, based on fundamental experiments carried out at a number of
different locations. In that year a laboratory directed by J.
Robert Oppenheimer was created on an isolated mesa at Los
Alamos, New
Mexico, 34 miles (55 km) north of Santa
Fe. This laboratory had to develop methods of reducing the
fissionable products of the production plants to pure metal and fabricating the
metal to required shapes. Methods of rapidly bringing together amounts of
fissionable material to achieve a supercritical mass (and thus a 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 proper moment 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 far
advanced so that an actual field test of a nuclear explosive could be
scheduled. Such a test was no simple affair. Elaborate and complex equipment
had to be assembled so that a complete diagnosis of success or failure could be
had. By this time the original $6,000 authorized for the Manhattan Project had
grown to $2 billion.
The first atomic
bomb was exploded at 5:30 am
on July 16, 1945, at a site on the Alamogordo
air base 120 miles (193 km) south of Albuquerque,
New Mexico. It was detonated on top of a steel tower surrounded by scientific
equipment, with remote monitoring taking place in bunkers occupied by
scientists and a few dignitaries 10,000 yards (9 km) away. The explosion came
as an intense light flash, a sudden wave of heat, and later a tremendous roar
as the shock
wave passed and echoed in the valley. A ball of fire rose
rapidly, followed by a mushroom cloud extending to 40,000 feet (12,200 metres).
The bomb generated an explosive power equivalent to 15,000 to 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 (730 metres). The
following month, two other atomic bombs produced by the project, the first
using uranium-235 and the second using plutonium, were dropped on Hiroshima
and Nagasaki,
Japan.
Source: http://www.britanica.com/event/manhattan-Project
Source: http://www.britanica.com/event/manhattan-Project
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