Requirements for a new, more powerful bomb were formulated in March 1941, aiming for the maximum possible blast effect over the largest possible area. Initially, an 8,000-pound bomb (over 3.5 tons) was intended for transport in a disposable glider, but it was soon decided to explore the possibility of loading it into heavy bombers under development.
The first variant considered for this development was a modification of the “Wellington”—the twin-engine Vickers “Warwick”. However, the maximum diameter that could be accommodated in the bomb bay was 30 inches (762 mm), the same as the “Cookie” bomb. To fit a bomb of double the caliber, its length needed to be increased, which posed certain operational difficulties.
Innovative Design and Early Challenges
Eventually, with the advent of new 4-engine bombers, it was decided to simply connect two 4,000-pound bombs into a single unit. The idea of a ‘composite’ munition was both novel and original. This approach offered certain advantages in reducing production difficulties, and no obvious problems were anticipated with the simultaneous detonation of the two bombs. The biggest drawback was its excessive length compared to its diameter—approximately 1/3.
The possibility of increasing the bomb’s diameter to 48 inches (1291 mm) for placement in a disposable glider was considered. Soon it was discovered that the new “Warwick” bomber could accommodate a bomb with a 38-inch (965 mm) diameter, making the diameter-to-length ratio more realistic. Work on the 30-inch and 48-inch bombs was abandoned, and the decision was finally made to focus on the 38-inch bomb design.
By June 1941, preliminary designs for the 8,000-pound bomb were completed, and the principle of creating the bomb from sections of smaller caliber was retained. However, the idea of simply joining standard 4,000-pound bombs into one block had to be abandoned. Instead, two 4,000-pound sections of larger diameter were used, joined by a flange welded to one of the sections and then bolted together.
Testing and Explosive Composition
By August 1941, three inert bombs were completed and dispatched for testing. Two additional bombs were filled with explosives and tested for their destructive effectiveness. By October 1941, the bomb’s testing cycle was complete. Overall, the effectiveness of the 8,000-pound bomb was deemed satisfactory and proportional to the power of the 4,000-pound bomb.
Recommendations for explosive filling prescribed 85% amatol and 15% of an RDX and TNT mixture in equal proportions. However, in production, bombs were filled with various explosive compositions depending on the availability of specific high explosives.
Combat Deployment and Lancaster Adaptations
The 8,000-pound bomb was first used in combat in late 1942. Its primary carrier became the heavy bomber “Lancaster”. However, even its capacious bomb bay (the largest among bombers of all nations at that time) could not accept it without some modifications. It was found that accommodating the 8,000-pound bomb required altering the bomb bay doors, which interfered with the installation of radar equipment.
Therefore, a certain number of “Lancaster” bombers were specifically modernized to carry this bomb, with their rear-view radar, whose antenna was located under the fuselage in a fairing, being removed. Sometimes, though very rarely, an annular tail stabilizer was used on the 8,000-pound bombs, but generally, the bomb was used without it.