Book contents
- Frontmatter
- Contents
- List of Illustrations
- Preface
- 1 Introduction
- 2 Early Research on Fission: 1933–1943
- 3 The Early Materials Program: 1933–1943
- 4 Setting Up Project Y: June 1942 to March 1943
- 5 Research in the First Months of Project Y: April to September 1943
- 6 Creating a Wartime Community: September 1943 to August 1944
- 7 The Gun Weapon: September 1943 to August 1944
- 8 The Implosion Program Accelerates: September 1943 to July 1944
- 9 New Hopes for the Implosion Weapon: September 1943 to July 1944
- 10 The Nuclear Properties of a Fission Weapon: September 1943 to July 1944
- 11 Uranium and Plutonium: Early 1943 to August 1944
- 12 The Discovery of Spontaneous Fission in Plutonium and the Reorganization of Los Alamos
- 13 Building the Uranium Bomb: August 1944 to July 1945
- 14 Exploring the Plutonium Implosion Weapon: August 1944 to February 1945
- 15 Finding the Implosion Design: August 1944 to February 1945
- 16 Building the Implosion Gadget: March 1945 to July 1945
- 17 Critical Assemblies and Nuclear Physics: August 1944 to July 1945
- 18 The Test at Trinity: January 1944 to July 1945
- 19 Delivery: June 1943 to August 1945
- Epilogue
- 20 The Legacy of Los Alamos
- Notes
- Name Index
- Subject Index
13 - Building the Uranium Bomb: August 1944 to July 1945
Published online by Cambridge University Press: 31 March 2010
- Frontmatter
- Contents
- List of Illustrations
- Preface
- 1 Introduction
- 2 Early Research on Fission: 1933–1943
- 3 The Early Materials Program: 1933–1943
- 4 Setting Up Project Y: June 1942 to March 1943
- 5 Research in the First Months of Project Y: April to September 1943
- 6 Creating a Wartime Community: September 1943 to August 1944
- 7 The Gun Weapon: September 1943 to August 1944
- 8 The Implosion Program Accelerates: September 1943 to July 1944
- 9 New Hopes for the Implosion Weapon: September 1943 to July 1944
- 10 The Nuclear Properties of a Fission Weapon: September 1943 to July 1944
- 11 Uranium and Plutonium: Early 1943 to August 1944
- 12 The Discovery of Spontaneous Fission in Plutonium and the Reorganization of Los Alamos
- 13 Building the Uranium Bomb: August 1944 to July 1945
- 14 Exploring the Plutonium Implosion Weapon: August 1944 to February 1945
- 15 Finding the Implosion Design: August 1944 to February 1945
- 16 Building the Implosion Gadget: March 1945 to July 1945
- 17 Critical Assemblies and Nuclear Physics: August 1944 to July 1945
- 18 The Test at Trinity: January 1944 to July 1945
- 19 Delivery: June 1943 to August 1945
- Epilogue
- 20 The Legacy of Los Alamos
- Notes
- Name Index
- Subject Index
Summary
After abandoning the plutonium gun, Oppenheimer streamlined the uranium gun program. The remaining work, all experimental and straight-forward, was consolidated in one ordnance group under Lt. Comdr. A. Francis Birch. Birch's group completed and tested the uranium gadget design by February 1945. Meanwhile, metallurgists decided that 235U was strong enough to be used in its natural state, so that alloy research could be discontinued. They developed suitable large-scale metal reduction and fabrication techniques. Polonium production for the initiators was on schedule.
As 235U production slowly increased and the laboratory made arrangements for fabricating gun parts, a quiet but dramatic change was occurring in the gun program. Before March 1945, this program had centered on perfecting a reliable method of assembling 235U. Now Birch had to turn the gadget into a bomb that could be delivered by an airplane. The bomb had to contain the gun gadget, offer protection from antiaircraft fire, house all the components (including antenna, fuzing, and circuitry), and provide a reliable, stable flight. The design of the gadget could still be changed slightly, after being frozen in February. But once the drop tests began, extensive changes could not be made without jeopardizing Groves's July deadline.
Conversion to the Uranium Gun
With the cancellation of the plutonium gun in July 1944, the need to develop a multifaceted high-velocity gun suddenly vanished. Fifteen months of intensive effort had gone into the physical design of the plutonium gun's components, into interior ballistics, and the mechanical properties of plutonium.
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- Critical AssemblyA Technical History of Los Alamos during the Oppenheimer Years, 1943–1945, pp. 249 - 266Publisher: Cambridge University PressPrint publication year: 1993