The Boeing Model 450 B-47 Stratojet was a medium-range and medium-size jet bomber capable of flying at high subsonic speeds and primarily designed for penetrating the airspace of the Soviet Union. A major innovation in post-World War II combat jet design, it helped lead to the development of modern jet airliners. Although the B-47 never saw major combat use, it served the United States Air Force from 1951 through 1969 and was a mainstay of the U.S. Air Force’s Strategic Air Command (SAC) during the 1950s and early 1960s.
The B-47 arose from a 1943 U.S. Army Air Forces requirement for a jet bomber and reconnaissance aircraft that could reach Nazi Germany in the event that Great Britain fell.
The National Advisory Committee for Aeronautics (NACA, the ancestor of NASA) performed wind tunnel tests on a composite model of the designs submitted by the manufacturers, (The three submissions were generally similar).
The NACA wind tunnel tests showed that the Boeing model suffered from excessive drag. Boeing engineers then tried a revised design, the Model 432, with the four engines buried in the forward fuselage, but although it had some structural advantages there was little effect on drag.