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 | In
                    1955 the US Air Force issued System Requirement No.
                    22 for Weapon System (WS) 110A, a chemically powered
                    bomber to succeed the B-52 in SAC service from
                    1963.  This aircraft was to be able to deliver
                    thermonuclear weapons to targets within the Soviet
                    Union from bases in the continental US.  The
                    weapons were to be free-fall bombs or a 300+
                    nautical mile range cruise missile.  The bomber
                    itself was to have an un-refuelled radius of more
                    than 4000 nautical miles, with a subsonic cruise and
                    high supersonic dash over the target. 
 Both Boeing and North American Aviation studied
                    various designs to meet this requirement.  The
                    winning North American proposal was ultimately
                    developed into the XB-70 Valkyrie, which flew in
                    prototype form in 1964.  The Boeing
                    configurations ranged from 16-engined developments
                    of the B-52 to trapezoidal and delta winged
                    machines.
 
 A more radical concept developed by Boeing but used
                    by both competitors was the "floating panel". 
                    In this arrangement, the outer wings of the
                    aircraft, with their own fuel pods, undercarriage
                    and even engines, acted as sub-craft and were free
                    to rotate in flight to eliminate loads on the
                    central airframe.  After the subsonic cruise
                    section of the flight, these outer panels would be
                    jettisoned and the bomber would accelerate to
                    supersonic speeds for the attack.  Although the
                    use of large jettisonable pods had been demonstrated
                    on the Convair B-58 Hustler, the idea was not
                    carried forward and the final designs presented by
                    North American and Boeing were monolithic bombers.
 
 
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