this is america's mach 3 super bomber that you've never seen
the north american aviation xb70 valkyrie was the prototype version of the planned b70 nuclear-armed
deep penetration supersonic strategic bomber for the united states air force strategic air command
designed in the late 1950s by north american aviation naa the six-engine valkyrie was capable
of cruising for thousands of miles at mach 3 plus while flying at 70 000 feet or 21 000 meters
the usaf eventually gave up fighting for its production and the b-70 program was cancelled
in 1961. development was then turned over to a research program to study the effects of
long-duration high-speed flight as such two prototype aircraft designated xb70a
were built these aircrafts were used for supersonic test flights during 1964-1969
at these speeds it was expected that the b-70 would be practically immune to interceptor
aircraft the only effective weapon against bomber aircraft at the time the bomber would spend only a
brief time over a particular radar station flying out of its range before the controllers could
position their fighters in a suitable location for an interception high speed also made the
aircraft difficult to see on radar displays and its high altitude and high speed capacity could
not be matched by any contemporaneous soviet interceptor or fighter aircraft
the idea behind the xb70 originated in the 1950s when it was assumed ever greater speeds
and altitudes would enable american bombers to survive against soviet air defenses unmolested on
their way to delivering their doomsday payloads at the time the only effective defense against
bombers were fighters and anti-aircraft artillery even then anti-aircraft guns were only marginally
effective and interceptors were increasingly challenged by ever improving bomber performance
the introduction of the first soviet surface-to-air missiles in the late 1950s
put the near invulnerability of the b-70 in doubt in response the united states air force usaf
began flying its missions at low level where the missile radar's line of sight was limited
by terrain in this low-level penetration role the b-70 offered little additional performance
over the b-52 it was meant to replace while being far more expensive with shorter range other
alternate missions were proposed but these were of limited scope with the advent of intercontinental
ballistic missiles or icbms during the late 1950s man bombers were increasingly seen as obsolete
meanwhile the xb70 test program continued the jet made its first flight on september 21 1964
when it flew from palmdale to edwards air force base california but the first xb70 proved to be
a disappointment it had poor directional stability above mach 2.5 and made only one
flight above mach 3.0 the second jet which flew on july 17 1965 added five degrees of dihedral
on the wings for better supersonic stability with the growing realization that soviet sams posed an
increasing threat to american bombers the pentagon started to explore low-level penetration as an
alternative low-level penetration involved flying under the radar horizon using terrain
to mask a bomber's approach which greatly reduces enemy response times moreover the development of
intercontinental ballistic missiles greatly reduced the united states reliance on man-bombers
many leading military strategists of the time believed bombers were too vulnerable
to survive the journey into soviet airspace as a result president john f kennedy decided to
cancel the xb70 as a front-line bomber program on march 28 1961. tragedy struck on june 8 1966
when the second xb70 prototype was destroyed in a crash after a mid-air collision with its
f-104n chase plane two people were killed and one was severely injured during the accident the loss
of the second aircraft which was much more capable than the first was a huge setback testing however
continued until february 4th 1969. ultimately the first xb70 logged 83 flights totaling hours in 16
minutes while the second xb70 logged 46 flights totaling 92 hours and 22 minutes according to nasa
the xb70 while a technological wonder at the time was the wrong plane for the wrong time
it came at a time when ballistic missiles were thought to be supplanting men bombers
moreover it was being developed at a time when it was increasingly apparent that high
speed and high altitude were not sufficient protection against surface-to-air missiles
or the next generation of soviet fighters but the nail in the coffin was the jet's exorbitant
price tag and lack of mission flexibility the b-70 couldn't be adopted for the low-level role
the air force changed the program to full weapon development and awarded a contract
for an xb70 prototype and 11 yb70s in august 1960. in november 1960 the b-70 program received a 265
million dollars equivalent to 2.3 billion today appropriation from congress for fiscal year 1961.
nixon trailing in his home state of california also publicly endorsed the b-70
and on 30 october eisenhower helped the republican campaign with a pledge of an
additional 155 million dollars 1.3 billion dollars today for the b-70 development program
the xb70 used compression lift which arose from a shock wave generated by the sharp leading edge
of the central engine intake splitter plate below the wing at mach 3 cruising speed the shock wave
attached along the wing leading edge preventing the high pressure behind the shock front from
leaking up over the wing the compression lift provided five percent of the total lift the wing
included inboard camber to more effectively use the high pressure feel behind the strong shock
wave unique among aircraft of its size the outer portion of the wings were hinged and could be
pivoted downward by up to 65 degrees acting almost as a type of variable geometry wingtip device this
increased the aircraft's directional stability at supersonic speeds shifted the center of pressure
to a more favorable position at high speeds and strengthened the compression lift effect
with the wingtip stroop downwards the compression lift shock wave would be further trapped under
the wings the valkyrie was designed to be a high altitude mach 3 bomber with six
engines harrison storms shaped the aircraft with a canard surface and a delta wing
which was built largely of stainless steel sandwiched honeycomb panels and titanium
the xb70 was designed to use supersonic technologies developed for the mach 3
sm-64 navajo as well as a modified form of the navajos inertial guidance system
you