NORTH AMERICAN XB-70 VALKYRIE 81
L
ike nothing before it and nothing since,
the B-70 Valkyrie was a technological
masterpiece. Designed to be the
ultimate high-altitude, high-speed manned
strategic bomber, it was to be immune from
enemy ghters by a planned cruise speed of
Mach 3 and operating altitude of 70,000ft.
Events, however, would cause it to play a far
di erent role in the history of aviation.
The Valkyrie was designed to be a high-
altitude Mach 3 bomber powered by six
engines, but was under development at a time
when the future of the manned bomber was
uncertain. During the late 1950s and early
1960s, many believed that manned aircraft were
obsolete, and the future belonged to missiles.
As a result, the Kennedy Administration ended
plans to deploy the B-70. Two experimental
XB-70A prototypes were under construction at
North American Aviation when the programme
was cancelled. At the same time there was
growing interest in an American supersonic
transport (SST). The XB-70 Valkyrie seemed to
be a perfect testbed for SST research. It was
the same size as the projected SST designs,
and used similar structural materials, such as
brazed stainless steel honeycomb and titanium.
Thus, the XB-70A’s role changed from a
manned bomber prototype to one of the most
remarkable research aircraft ever own.
To achieve Mach 3 performance, the B-70 was
designed to ‘ride’ its own shock wave, much as a
surfer rides an ocean wave. The resulting shape
used a delta wing on a slab-sided fuselage that
contained the six jet engines that powered the
aircraft. The outer wing panels were hinged.
During take-o , landing, and subsonic ight,North American
XB-70 Valkyrie
they remained in the horizontal position. Once
the aircraft was supersonic, the wing panels
would be hinged downward reducing drag
and providing more vertical surface to improve
directional stability at high Mach numbers.
Attached to the delta was a long, thin forward
fuselage. Behind the cockpit were two large
canards, which acted as control surfaces.The need for speed
The Valkyrie rst burst through the
sound barrier on 12 October 1964,
reaching a speed of Mach 1.1. The
aircraft subsequently set a number
of world records, which included
sustained supersonic ight for 40
continuous minutes on 24 October
1964 and sustained supersonic ight
for 60 minutes on 4 March 1965. On
the Valkyrie’s tenth ight, the aircraft
sustained 74 minutes of supersonic
ight, including 50 minutes beyond
Mach 2. The second Valkyrie was
aerodynamically better and it attained
Mach 3 for the rst time on 3 January- On 19 May of that year it ew at
Mach 3 for 33 minutes and at Mach 2.5
for a total of 62 minutes.
Left: The XB-70A, capable of ying three times
the speed of sound, was the world’s largest
experimental aircraft in the 1960s. Two XB-70A
aircraft were built, serial numbers 62-0001 and
62-0207.Right: The Valkyrie was powered by a bank of six
General Electric YJ93-GE-3 afterburning turbojets.
While travelling at Mach 2.58 on 7 May 1965, the
aircraft’s horizontal intake splitter was torn away
and pieces landed in the engines, which were all
destroyed beyond repair. Incredibly, the Valkyrie
managed to land in one piece.