Pumpkin bomb
| Pumpkin bomb | |
|---|---|
 A picture of a Pumpkin bomb |
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| Type | Conventional high explosive bomb |
| Place of origin | United States |
| Service history | |
| In service | 1945 |
| Used by | United States Army Air Corps |
| Wars | World War II |
| Production history | |
| Number built | 486 |
| Specifications | |
| Weight | 5.26 tons |
| Length | 12 feet, 5 inches |
| Diameter | Five feet |
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| Filling | Composition B |
| Filling weight | 6,000 pounds |
Pumpkin bombs were conventional high explosive aerial bombs developed by the Manhattan Project and used by the United States Army Air Forces against Japan during World War II. The name "pumpkin bomb" resulted from the large ellipsoidal shape of the munition and was the actual reference term used in official documents.
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[edit] Development
The concept for the pumpkin bomb originated with Navy Captain William S. Parsons of the Ordnance Division at Los Alamos and USAAF Colonel Paul W. Tibbets, commander of the 509th CG, on December 13, 1944, as a means of providing continued realistic training for the B-29 crews assigned to drop the atomic bomb after their deployment to the Western Pacific. The bomb would be a close but non-nuclear replication of the Fat Man plutonium bomb with the same ballistic and handling characteristics. Mission parameters would be similar to those of the actual atomic bomb missions, and all targets would be located in the vicinity of the cities designated for atomic attack.
The development of the bomb was managed by the California Institute of Technology under the direction of Dr. Charles C. Lauritsen. Specifications for the bomb required that it be carried in the forward bomb bay of a Silverplate B-29 and be fuzed to be effective against actual targets. The bomb shells were manufactured by two Los Angeles, California, firms, Consolidated Steel Corporation and Western Pipe and Steel Company, while the tail assembly was produced by Centerline Company of Detroit, Michigan. After initial development, management of the program was turned over to the U.S. Navy Bureau of Ordnance in May 1945.
Pumpkin bombs were produced in both inert and high explosive variants, with the inert versions filled with a cement-plaster-sand mixture combined with water to the density of the Composition B used in the high explosive versions. The filler of both variants had the same weight and weight distribution as the inner sphere used in the plutonium bomb. All of the inert versions were shipped from the manufacturers directly to Wendover Army Air Field, Utah, by rail, where they were used by the 216th Base Unit in flight testing of the bomb shape.
The bombs intended as live ordnance were shipped to the Naval Ammunition Depot, McAlester, Oklahoma, for filling with explosives. The Composition B was poured as a slurry, solidified in a drying facility, sealed, and shipped by railroad to the Port Chicago Naval Magazine, California for shipment by sea to Tinian.[1]
A total of 486 live and inert bombs were eventually assembled.
[edit] Description
The pumpkin bombs were externally similar to the Fat Man bomb in size and shape, and both had the same 52-inch square tail assembly and single-point attachment lug. The pumpkin bomb had three contact fuses arranged in an equilateral triangle around the nose of the bomb while the atomic bomb had four fuse housings. The atomic bomb had its sections bolted together but most if not all of the pumpkin bombs were welded with a four-inch hole used for filling the shell. The Fat Man also had four external mounting points for radar antennas which the pumpkin bombs did not have.
The pumpkin bombs were twelve feet eight inches in length and five feet in maximum diameter. The most commonly-given weight for the bombs is 5.26 tons, consisting of 3,800 pounds for the shell, 425 pounds for the tail assembly, and 6,300 pounds of filler. The shells were made of .375-inch steel plate and the tail assemblies from .200-inch aluminum plate. Although anecdotal sources attribute the naming of the bombs to painting them a pumpkin color, photographs indicate that the units delivered to Tinian came painted in the same Zinc Chromate primer color worn by Fat Man [2]
[edit] Use
Combat missions were flown by the 509th Composite Group between July 20, 23, 26 and 29, and August 8 and 14, 1945, using the bombs against individual targets in Japanese cities, to practice dropping the Fat Man nuclear shape from the B-29 Superfortress. A total of 49 bombs were dropped on 14 targets, one was jettisoned into the ocean, and two were aboard aircraft that aborted their missions.[3] More than 400 people were estimated killed and 1,200 others injured.[4]
In addition to the live ordnance dropped on Japan, several hundred inert bombs were used by combat crews of the 509th's 393rd Bomb Squadron to test the ballistics of the bomb shape in conjunction with Project Alberta, and to train bombardiers in mission procedures before movement of the group overseas.
[edit] See also
[edit] References
[edit] Notes
- ^ National Archives, minutes of third target committee meeting, May 28 45.
- ^ Coster-Mullen, Atom Bombs, photographs, p 184 and 185.
- ^ Campbell, The Silverplate Bombers, 27 and 104.
- ^ "模擬原爆パンプキン 秘められた原爆投下訓練". NHK. http://www.nhk.or.jp/sonotoki/2008_08.html. Retrieved 2010-01-20.
[edit] Bibliography
- Coster-Mullen, John, Atom Bombs: the top secret inside story of Little Boy and Fat Man (2011), (Self Published)
- Campbell, Richard H., The Silverplate Bombers: A History and Registry of the Enola Gay and Other B-29s Configured to Carry Atomic Bombs (2005), pp. 27–29, 72-75, 90. ISBN 0-7864-2139-8.
- Department of Energy/The Manhattan Project: Final Decision to Use the Bomb.
