FINAL BOMB DESIGN
Los Alamos: Laboratory
(1944-1945)
Events: Bringing It All
Together,
1942-1945
Late in 1944, Los Alamos
began to shift from research to development and bomb production. Increased
production at Oak Ridge and Hanford seemed to promise that
enough plutonium and enriched uranium would be available for at least one bomb using
each. Germany no longer was the intended primary target. The war in
Europe (right) appeared to be entering its final phase, and evidence
uncovered by the ALSOS mission in November 1944 indicated that the German
atomic program had not gone beyond the research phase. Already by
summer 1944, Groves and his advisers had turned their sights toward
Japan. The atomic bomb would justify the years of effort,
including both the vast expenditures and the judgment of everyone
responsible, by bringing the war in the Pacific to a fiery end.
Ongoing
problems continued to complicate
the efforts of Robert
Oppenheimer (right) to finalize bomb design. Foremost among
these were continuing personnel shortages, particularly of physicists, and
supply difficulties. The procurement system, designed to protect the
secrecy of the Los Alamos project, led to frustrating delays and, when combined
with persistent late war shortages, proved a constant headache. The lack
of contact between the remote laboratory and its supply sources exacerbated the
problem, as did the relative lack of experience the academic scientists had with
logistical matters.
Leslie Groves and
James Conant were determined not to let mundane problems compromise the bomb
effort, and in fall 1944 they made several changes to prevent this
possibility. Conant shipped as many scientists as could be spared from the
Met Lab and Oak
Ridge to Los Alamos, hired every civilian machinist he could lay his
hands on, and arranged for Army enlisted men to supplement the work force (these
GIs were known as SEDS ("Special Engineering
Detachment"). Hartley Rowe,
an experienced industrial engineer, provided help in easing the transition from
research to production. Los Alamos also arranged for a rocket research
team at the California Institute of Technology to aid in procurement, test
fuses, and contribute to component development. These changes kept Los
Alamos on track as design work reached its final stages.
Weapon design for the uranium
gun-type
bomb was frozen in February 1945. Confidence in the weapon was high enough
that a test prior to combat use was seen as unnecessary. The design for an
implosion device was approved in March with a
test of the more problematic plutonium weapon scheduled for July 4.
Oppenheimer shifted the laboratory into high gear and assigned Samuel Allison,
Robert Bacher, and George Kistiakowsky to the Cowpuncher Committee to "ride
herd" on the implosion weapon. He placed Kenneth T. Bainbridge
(right) in
charge of Project Trinity, a new division to
oversee the July test firing. "Deke" Parsons headed Project
Alberta, known as Project A, which had the responsibility for preparing and
delivering weapons for combat.
The bombs had to be physically assembled at Los Alamos, and this
depended largely on the ability of the chemists and metallurgists to process the
uranium and plutonium into metal and craft them into the correct shape and
size. Plutonium (right) posed by far the greater obstacle. It existed in
different states, depending upon temperature, and was extremely toxic.
Working under intense pressure, the chemists and metallurgists managed to
develop precise techniques for processing plutonium just before it arrived in
quantity beginning in May.
As a result of progress at Oak Ridge and metallurgical and
chemical refinements on plutonium that improved implosion's chances, the nine
months between July 1944 and April 1945 saw the American bomb project progress
from doubtful to probable. The August 1 delivery date for the "Little
Boy" uranium bomb (right) certainly appeared more likely than it had when Groves
briefed George Marshall. There would be no implosion weapons in the first
half of 1945 as Groves had hoped, but developments in April boded well for the
scheduled summer test of the "Fat Man" plutonium bomb (right). And
recent calculations provided by Hans Bethe's theoretical group gave hope that
the yield for the first weapon would be in the vicinity of 5,000 tons of TNT
rather than the 1,000-ton estimate provided in fall 1944.
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