World War Photos

B-29 Enola Gay Tinian August 1945

Operation Silverplate: Preparing the B-29 for the Atomic Bomb

Operation Silverplate was the code name given by the USAAF to a top-secret project to modify B-29 Superfortresses for the delivery of atomic bombs. The project began in late 1943, well before the first nuclear device was even tested. The modifications were initially made in anticipation of a nuclear weapon weighing up to 25,000lb. These modifications were so significant that they effectively created a specialized variant of the B-29.

Modifications

A total of 46 Silverplate B-29s were produced by the Glenn L. Martin factory before the war’s end. To reduce weight and accommodate the expected size of the bombs, the Silverplate B-29s were stripped of their armor and gun turrets, except for the twin .50-caliber machine guns in the tail. The bomb bays were reconfigured to handle a single, five-ton bomb up to 128 inches in length and five feet in diameter. This involved:

• Reconfiguring the twin bomb bays to carry a single 10,000lb bomb.
• Installing British F-type bomb releases and G-type attachments.
• Adding dual electrical and mechanical bomb release mechanisms.
• Equipping the bomb bay doors with pneumatic actuators for rapid opening and closing.

Beyond the bomb bay modifications, other changes included:

• Installing four fuel-injected Wright R-3350-41 engines, known for their high performance and reliability.
• Using newly developed Curtiss-Electric reversible-pitch propellers to enhance braking capability upon landing.
• Creating a new crew position called the “weaponeer station” to monitor the release and detonation of the atomic weapons.

Deployment

Of the 46 Silverplate B-29s produced, 29 were assigned to the 509th Composite Group (CG), with 15 based in the Marianas. The 509th CG, commanded by Colonel Paul W. Tibbets Jr., was formed specifically to deliver the atomic bombs. The group’s activities were shrouded in secrecy, and they initially used the markings of the 6th Bomb Group as a security measure.

To maintain secrecy and enhance operational efficiency, the 509th CG operated independently from other B-29 units. They conducted training flights to low-priority targets like Truk and locations within Japan, but their true mission remained unknown to those outside the group.

Operational History

The Silverplate B-29s played a pivotal role in the atomic bombings of Hiroshima and Nagasaki in August 1945. Enola Gay, piloted by Colonel Tibbets, dropped the “Little Boy” atomic bomb on Hiroshima on August 6, 1945. Three days later, Bockscar, piloted by Major Charles Sweeney, dropped the “Fat Man” atomic bomb on Nagasaki.

Beyond their use in the atomic bombings, the Silverplate B-29s also participated in Operation Crossroads, a series of nuclear weapon tests conducted at Bikini Atoll in 1946. Dave’s Dream, one of the original Silverplate B-29s, was used to drop an atomic bomb during the “Able” test on July 1, 1946.

Post-War

Following World War II, the remaining Silverplate B-29s continued to play a critical role in the development and deployment of nuclear weapons:

• In 1946, the Strategic Air Command (SAC) assumed responsibility for the atomic bomb and inherited the 509th CG and its fleet of 65 Silverplate B-29s.
• The 97th Bombardment Wing at Biggs Air Force Base in Texas received 27 Silverplate B-29s from the 509th Bombardment Wing when it transitioned to the B-50D bomber in 1949.
• By November 1951, all Silverplate B-29s had been reassigned to other roles or retired, marking the end of Operation Silverplate after nearly eight years.
• The Saddletree codename replaced Silverplate in May 1947 due to concerns about the original codename being compromised. Saddletree modifications were then applied to the B-50 and B-36 bombers as the US expanded its nuclear arsenal.