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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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