page_title: Silverplate
section_title: Initial experiments
hierarchical_section_title: Silverplate / Initial experiments
caption_attribution_description: Casings for the "Thin Man" plutonium gun design weapons being developed during the Manhattan Project as part of Project Alberta at Wendover Field, Utah (additional "Fat Man" test casings can be seen in the background as well). The plutonium gun design was eventually abandoned as infeasible, as the spontaneous fission rate of reactor-bred plutonium was much higher than expected.
context_page_description: Silverplate was the code reference for the United States Army Air Forces' participation in the Manhattan Project during World War II. Originally the name for the aircraft modification project which enabled a B-29 Superfortress bomber to drop an atomic weapon, "Silverplate" eventually came to identify the training and operational aspects of the program as well. The original directive for the project had as its subject line "Silver Plated Project" but continued usage of the term shortened it to "Silverplate".
  Testing began with scale models at the Naval Proving Ground in Dahlgren, Virginia, in August 1943. Modifications began on a prototype Silverplate B-29 known as the "Pullman" in November 1943, and it was used for bomb flight testing at Muroc Army Air Field in California commencing in March 1944. The testing resulted in further modifications to both the bombs and the aircraft.
  Seventeen production Silverplate aircraft were ordered in August 1944 to allow the 509th Composite Group to train with the type of aircraft they would have to fly in combat, and for the 216th Army Air Forces Base Unit to test bomb configurations.
context_section_description: The USAAF sent instructions to its Army Air Forces Materiel Command at Wright Field, Ohio, on 30 November 1943, for a highly classified B-29 modification project. The Manhattan Project would deliver full-sized mockups of the weapons shapes to Wright Field by mid-December, where Army Air Forces Materiel Command would modify an aircraft and deliver it for use in bomb flight testing at Muroc Army Air Field in California. B-29-5-BW 42-6259 (referred to as the "Pullman airplane" from an internal code name assigned it by the Engineering Division of Army Air Forces Materiel Command) was delivered to the 468th Bombardment Group at Smoky Hill AAB, Kansas, on 30 November 1943, and flown to Wright Field on 2 December.
  Modifications to the bomb bays of 42-6259 were extensive and time-consuming. Its four 12-foot (3.7 m) bomb bay doors and the fuselage section between the bays were removed and a single 33-foot (10 m) bomb bay configured. The length of the initial gun-type bomb shape was approximately 17 feet (5.2 m), necessitating that it be carried in the aft bomb bay, with some of its length protruding into the forward bay. The implosion-type bomb was mounted in the forward bay. New bomb suspensions and bracing were attached for both shape types, and separate twin-release mechanisms were mounted in each bay, using modified glider tow-cable attach-and-release mechanisms.
caption: "Thin Man" plutonium gun test casings at Wendover Army Air Field. Casing designs for "Fat Man" bombs are seen in the background. The tow truck was used to lower bombs into a pit for loading into the aircraft.
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