In an offshoot of Boeing's MX-2145 manned boost-glide bomber project, Boeing partnered with RAND Corporation in January 1954 to explore what sort of bomber aircraft would be needed to deliver the various contemporary nuclear weapons under development. At the time, nuclear weapons weighed several tons, and the need to carry enough fuel to fly that payload from the continental United States to the Soviet Union demanded large bombers. They also concluded that after the release of the bombs, the aircraft would need supersonic speed to escape the critical blast-radius.