In the event that launch sites might be forced back into the Reich itself, von Braun and his colleagues were put under pressure
to develop a longer-range version of the A-4 known alternately as A-9 and A-4b, the reason for the dual designation being that the A-4
series had received "national priority"; the A-4b designation ensured the availability of scarce resources
In June 1939, Kurt Patt of the Peenemünde Design Office, proposed wings for converting rocket speed and altitude into aerodynamic lift and
range. As the rocket encountered thicker atmosphere on its descent phase, it would execute a pullout and enter a shallow glide, trading
speed for distance. Patt also proposed the Flossengeschoss (fin projectile). Both concepts were utilized by Walter Dornberger when he
drafted a memo for presentation to Hitler regarding the "America rocket" on July 31, 1940.
Design studies on the A-9 began in 1940. In addition to its wings, the A-9 would have been somewhat larger than the A-4 and its
engine would have produced about 30% more thrust. Following wind tunnel testing of models, the design was subsequently modified to
replace the wings with fuselage strakes, as the tests showed that these provided better lift at supersonic velocities and also solved
the problem of transonic shift of the centre of lift.
Development was suspended in 1941, but in 1944 several V-2s were modified to an approximation of the A-9 configuration under the
designation A-4b. It was calculated that by fitting wings, the A4's range would be extended to 750 km (470 mi), allowing targets in
Britain to be attacked from launch sites within Germany itself. It was intended that following launch the curve of the A-4b's trajectory
would become shallower and the rocket would glide toward its target. It was anticipated that interception by enemy aircraft at the end
of the glide phase would be virtually impossible as over the target the A-4b was intended to enter a near vertical dive leaving little
time for interception.
The A-4b concept was tested by fitting swept back wings to two A-4s launched from Blizna. However, little development work had
been carried out and the first launch on 27 December 1944 was a complete failure. The second launch attempt, on 24 January 1945, was
partially successful, in that the wing broke off, but the A-4b still managed to become the first winged guided missile to break the
sound barrier and attain Mach 4.