Tag Archives: B-29

8 August 1945

Fat Man, Nuclear Bomb, Mark III, being prepared at Tinian, Marshall Islands, 8 August 1945. (U.S. Air Force)

“So, the next day, Fat Man, the two armored steel ellipsoids of its ballistic casing bolted together through bathtub fittings to lugs cast into the equatorial segments of the implosion sphere, its boxed tail sprouting radar antennae just as Little Boy’s had done. By 2200 on August 8 it had been loaded into the forward bomb bay of a B-29 named Bockscar after its usual commander, Frederick Bock, but piloted on this occasion by Major Charles W. Sweeney. Sweeney’s primary target was the Kokura Arsenal on the north coast of Kyushu; his secondary was the old Portuguese- and Dutch-influenced port city of Nagasaki, the San Francisco of Japan, home of the country’s largest colony of Christians, where the Mitsubishi torpedoes used at Pearl Harbor had been made.”

—The Making of the Atomic Bomb, by Richard Rhodes, Simon and Schuster, New York, 1986, Chapter 19 at Page 739.

The Mark III “Fat Man” bomb loaded on its carrier, 8 August 1945. (Manhattan Engineer District)

Fat Man was an implosion-type fission bomb, using plutonium (Pu-239) as the nuclear material. It was a very complex device which used 32 precisely-shaped explosive charges surrounding the spherical plutonium-alloy core, detonating with enough force to compress the core to double its normal density. This caused it to reach “critical mass” and the fission chain reaction began.

The Mark III implosion bomb and its trailer are lowered into the pit in preparation for loading aboard Bockscar, 8 August 1945. (U.S. Air Force)
The Mark III implosion bomb and its trailer are lowered into the pit in preparation for loading aboard Bockscar, 8 August 1945. (U.S. Air Force)

The Mark III bomb, unlike the gun-type “Little Boy,” required testing before combat use. The nuclear component of the bomb, called “Gadget,” had been exploded at 05:29:45 a.m., Mountain War Time, 16 July 1945, at the Trinity Site of the Alamogordo Test Range, in the Jornada del Muerta desert of New Mexico. The explosive yield of the detonation was estimated to be equivalent to 20–22,000 tons of TNT.

The fully assembled combat weapon was 12 feet, 8 inches ¹ (3.261 meters) long, 5 feet, ¼ inch ² (1.530 meters) in diameter, and weighed approximately 10,300 pounds (4,672 kilograms).

Rear fuselage of Bockscar, B-29 44-27297, at Tinian. Note the “Triangle N” and “77” codes. The Enola Gay is in the background. (U.S. Air Force)

¹ Overall length, ± ¼ inch

² Overall diameter, ± inch

© 2017, Bryan R. Swopes

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5 August 1945

Martin-Omaha B-29-45-MO Superfortress 44-86292, Enola Gay, being moved into position over the pit to load Little Boy, 5 August 1945. (U.S. Air Force)

5 August 1945: In the afternoon, the Glenn L. Martin Company B-29-45-MO Superfortress 44-86292 was towed into position over a 13-foot × 16-foot (3.9 × 4.9 meters) concrete pit on the island of Tinian in the Marshall Group. Down in that pit was the most destructive weapon of war yet devised by man: The Mark I, code named Little Boy.

Little Boy was a nuclear bomb, designed to explode with unimaginable force when two masses of highly enriched uranium were forced together at very high speed. This was a “gun-type” bomb, considered to be so simple that it was not even tested before it was used.

Several hours later, at 0245 6 August 1945, the B-29, which had been named Enola Gay, took off from North Field and headed toward Hiroshima, Japan.

Bomb Unit L-11 in the pit before loading aboard Enola Gay, 5 August 1945. (U.S. Air Force)

© 2015, Bryan R. Swopes

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11 December 1945

Bell-Atlanta B-29B-60-BA Superfortress 44-84061, the Pacusan Dreamboat. (U.S. Air Force)
Bell-Atlanta B-29B-60-BA Superfortress 44-84061, the Pacusan Dreamboat. (U.S. Air Force)

11 December 1945: Three days after Lieutenant Colonel Henry E. Warden and Captain Glen W. Edwards set a transcontinental speed record flying a prototype Douglas XB-42 from Long Beach California to Washington, D.C. in 5 hours, 17 minutes, Colonel Clarence S. Irvine and the crew of the B-29 Pacusan Dreamboat also set a record, flying from Burbank, California to overhead Floyd Bennett Field, New York, in 5 hours, 27 minutes, 8 seconds. The average speed for the 2,464-mile flight was 450.38 miles per hour (724.82 kilometers per hour).

Lieutenant General Clarence S. Irvine, U.S. Air Force

Irvine was Deputy Chief of Staff, Pacific Air Command, 1944–1947. He flew the Pacusan Dreamboat on several record-setting flights, including Guam to Washington, D.C., and Honolulu, Hawaii to Cairo, Egypt. He rose to the rank of lieutenant general in the United States Air Force, and served as Deputy Chief of Staff for Materiel.

Pacusan Dreamboat was a Bell Aircraft Corporation B-29B-60-BA Superfortress, built at Marietta, Georgia. The B-29B was a lightweight variant of the B-29, intended for operation at lower altitudes. It did not have the four power gun turrets and their .50-caliber machine guns. A radar-directed 20 mm cannon and two .50-caliber machine guns in the tail were the only defensive weapons. Much of the standard armor plate was also deleted. Pacusan Dreamboat was further lightened. The tail guns were removed and the tail reshaped.

The B-29B was equipped with four air-cooled, fuel-injected Wright R-3350-CA-2 Duplex Cyclone two-row 18 cylinder radial engines and specially-designed propellers. The engine nacelles were modified for improved cooling.

The Superfortress had been lightened to an empty weight of 66,000 pounds (29,937 kilograms). A standard B-29B weighed 69,000 pounds (31,298 kilograms) empty and 137,000 pounds (62,142 kilograms) fully loaded. Additional fuel tanks installed on the Dreamboat were able to carry 10,000 gallons (37,854 liters) of gasoline.

Colonel Clarence S. Irvine (standing, left) with the crew of Pacusan Dreamboat: W.J.Benett, G.F.Broughton, Dock West, W.S. O’Hara, F.S. O’Leary, K.L. Royer, F.J.Shannon, J.A. Shinnault, G.R. Stanley. (FAI)
Colonel Clarence S. Irvine (standing, left) with the crew of Pacusan Dreamboat: W.J.Benett, G.F.Broughton, Dock West, W.S. O’Hara, F.S. O’Leary, K.L. Royer, F.J.Shannon, J.A. Shinnault, G.R. Stanley. (FAI)

© 2015, Bryan R. Swopes

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