Length: 20.25"

B-47 research and development began in 1945 with the first prototype flight in December 1947. The Air Force wanted a high-altitude, medium-range, subsonic bomber. At that time, four contractors were developing bombers. Two designs were conventional bombers in the mold of the B-29, while the more radical designs were the Northrop flying wing and the Boeing swept wing jet. In this era before the SAM, fighter aircraft were considered the main threat to bombers. World War II had shown that stripped down B-29's with near-fighter speed and a higher altitude ceiling could only be successfully intercepted from the rear.

With the speed and maneuverability of the fighters of the late forties, Boeing's swept-wing XB-47 won the bomber competition and swiftly transformed the XB-46 and the XB-48 into aviation footnotes. Six Allison J35-2 turbojet engines slung in pods beneath the swept-back wings gave the prototype Stratojet nimble performance, and helped to validate a design concept still widely used today. Although uprated J47-GE-3s were soon substituted, the B-47 also carried mountings for 18 solid-fuel booster rockets in the aft fuselage to shorten the takeoff roll. Flight testing continued through 1951, and B-47's began entering the inventory in 1952. ICBMs and SLBMs did not yet exist, and the penetrating bomber was the only nuclear