<article><hdr>North American XB-70 Valkyrie</hdr><body>
<p>When the first North American—XB-70 prototype was rolled out from the Palmdale plant on 11 May 1964, the watching crowds felt conflicting emotions. Awe was one, for this monster, gleaming brilliant white in the hot sun, was the longest, heaviest, most powerful and most expensive aircraft since the Wright brothers; and, except for the small air-dropped X-15s made by the same company, it was the fastest. By a narrow margin it missed having the longest range and highest ceiling. Hardly a soul can have failed to feel excitement; many were elated at what they considered breathtaking beauty, and those who had worked on it felt relief that at least they had come this far.
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<p>Overlying everything, however, was the belief that the jagged white giant was probably a white elephant. The world seemed to be moving into a era of missiles and space, and the world's fastest and highest-flying bomber was looking increasingly vulnerable, to both enemy missiles and friendly Congressmen.
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<p>Things had looked very different 10 years previously. In 1954 the commander of the USAF's Strategic Air Command, the fearsome General Curtis E. LeMay, began to press for a new strategic bomber. Had he been told the Boeing B-52 would still be in service 35 years later he would have refused to believe it; in his view both that bomber and the Mach-2 Convair B-58 had limited capability, and SAC urgently needed to get started on something with as few deficiencies as possible. It was a time of amazing new vistas, and by 1955 SAC had three colossal new programs. Weapon System 107A was for an ICBM (intercontinental ballistic missile), previously considered impossible. WS-110A was for a CPB (chemically propelled bomber), combining intercontinental range with supersonic speed. WS-125A was for an NPB (nuclear propelled bomber) which could fly nonstop for weeks or months.
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<p>Six companies bid for the CPB, and on 11 November 1955 Boeing and NAA (North American Aviation Inc.) received Phase I design contracts. Supersonic aircraft inevitably suffer much higher drag than subsonic ones, and getting long range demands brilliance, subterfuge and cheating. NAA cheated by starting with a giant canard (tail-first) bomber tailored to Mach 2.3, and then adding to its wingtips freely hinged outer wings carrying fuel pods each as big as a Boeing B-47. Near the target these outer parts were unclipped, the bombing run was made at Mach 2.3 and the stubby canard bomber was then able to land with a weight of 220,000 lb (99,790 kg), little over one-quarter of the weight at which it took off. It was an impressive solution, but when LeMay saw the brochure he removed his cigar and growled, "Hell, this isn't an airplane, it's a three-ship formation."
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<p>NAA had exhausted the possibilities of area-ruled design, advanced afterburning engines and unusual configurations. One route to higher performance was a brutal frontal attack with 'zip fuel' to make engines more powerful. Various totally new fuels based on boron, such as the ethyl boranes, offered higher energy than traditional kerosenes. The problems were terrible, but in the absence of any better idea the USAF and US Navy began pouring tens of millions (today equivalent to billions) of dollars into vast new plants to produce zip fuel for the 1960s. For the CPB it meant about 10 per cent more range and a cruising speed up to Mach 3. The basic SAC demand of an unrefueled range of 6,325 miles (10,180 km), with a 1,000-mile (1,610-km) supersonic dash over the target remained out of reach. Then NAA's document searchers hit on a classified paper by Alfred J. Eggers and Clarence A. Syvertson of NACA (later NASA). While mowing his lawn Eggers had been pondering the problem, and had devised a scheme in which the aircraft body was entirely under the wing, whose leading-edge shockwave would cause compression under the wing which could be accentuated by hemming in the flow downstream between an expanding fuselage and downturned wingtips. A popular account later said the discovery of compression lift enabled a highly supersonic aircraft 'to climb atop its own shockwave much as a speedboat rises on to its step'.
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<p>Within a week NAA had a compression-lift model at Mach 3.5 in a tunnel, recording a gain in peak lift/drag ratio of 22 per cent, and over 100 per cent at small angles. Suddenly, the WS-110A aircraft could fly the whole mission at Mach 3 (2,000 mph; 3,220 km/h). Everyone was elated, yet there was a tiny nagging doubt. The US Army already had batteries of Nike SAMs, and their successors looked as if they would be able to shoot down any bomber, even one as fast as this. Surprisingly little attention was paid either to flying at treetop height, or to what today is called 'stealth' technology to make bombers undetectable. Instead, the debate began to rage around the question 'Does the ICBM make the bomber obsolete?' Nobody appeared to notice that this was a completely irrelevant issue, or that ICBMs cannot be used against moving targets, or for reconnaissance.
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<p>In parallel, NAA had been developing the most costly weapon the USAF had ever funded, the colossal SM-64 Navaho cruise missile. This flew the ICBM mission but with a Mach 3 winged vehicle. After spending $691 million the USAF cancelled this in July 1957. This cleared the way to award the CPB to NAA on 23 December 1957, and in 1958 this became the B-70 Valkyrie. In February 1958 Dr Hugh L. Dryden, Director of NACA (NASA later that year) said, "A strange and wonderful thing has happened, as if the pieces of a jigsaw were falling into place." Massive research programs into aerodynamics, structures and propulsion all began to pay off, and together they made the B-70 possible. The same technology was used for the North American F-108 Rapier long-range interceptor, with two B-70 engines instead of six, but this was cancelled in 1959.
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<p>When all the new research jigsaw was complete, NAA set about actually designing the B-70 which, after passing through five different company design numbers, finally went ahead as the NA-278. Three prototypes were ordered on 4 October 1961, but no. 3 was cancelled in May 1964, leaving just two aircraft with USAF numbers 62-001 and 62-207.
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<p>About 70 per cent of the structure was made of a new stainless steel, PH 15-7 Mo, which had to be hot-creep formed at 1,202 degrees F (650 degrees C) or deep-freeze formed at -99 degrees F (-73 degrees C). The interior structure was mostly sine-wave corrugated sheets, while the skin was brazed honeycomb sandwich, with paper-thin steel yet immense strength and rigidity at red-heat and a surface like a mirror. The hottest parts were Rene 41, never before used for an airframe, and the leading and trailing edges were machined to a razor-like finish. The fuselage grew like a long dinosaur neck from the apex of the vast wing, and was mainly titanium. Under the wing, and profiled to generate the compression lift, was the vast engine box housing six General Electric engines more powerful than anything previously attempted. On zip fuel just one was noisier than any previous air-breathing engine in history. Fortunately, the technical and political problems of zip fuel were so enormous that this program was terminated in August 1959, only days before the huge plants were to go 'on stream'. The engine box measured 7 ft (2.13 m) deep, 37 ft (11.3 m) wide and 110 ft (33.5 m) long, the last dimension being the same as the root chord of the wing. The inlet system and jet nozzles were fully variable in area and profile.
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<p>Each engine drove a 60-kVA alternator, while the total hydraulic horsepower ran into thousands. A new fluid called Oronite 70 served 85 linear actuators and 44 hydraulic motors, the most powerful of which fitted into the thin outer wings to drive them down to either 25 degrees or 65 degrees to gain full compression lift. Flight control surfaces comprised full-span elevons, powered foreplanes and twin slab vertical rudders without fins. Roughly twice as heavy as any previous aircraft, the XB-70 still had only eight main wheels, plus a fifth wheel on each bogie to serve as an anti-skid reference, while the nose gear folded back between the inlet ducts. Almost all parts of the aircraft were subcontracted throughout US industry, and some of the biggest contracts were for NAA's own Autonetics stellar/inertial navigation system, IBM's nav/bombing system, General Electric's 'unjammable' radar and Westinghouse's defensive electronic shield.
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<p>The crew of four rode in a pressure capsule between the radar and the canards in special rocket seats which, on ejection, were each enclosed in a sealed capsule to protect the occupant against the slipstream. A single long bay between the ducts and engines could carry groups of any thermonuclear bombs used by SAC, with sliding doors that opened automatically at the last moment before release of the chosen weapon. Studies were made of various forms of external ballistic missile carriage, but this was not a USAF requirement.
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<p>Back in 1957 the UK had boldly proclaimed that missiles made all further development of fighters or bombers unnecessary. While not buying this argument (nor did any other country), the USA did begin to have doubts about what it began to call cost/effectiveness of its major programs. The 1960 Kennedy administration brought Robert S. McNamara in as a very forceful Defense Secretary, and he opposed the B-70. In January 1962 he told the Congress, "Considering the increasing capabilities of ground-to-air missiles, the speed and altitude of the B-70, in itself, would no longer be a significant advantage. It has not been designed for the use of air-to-surface missiles such as Hound Dog or Skybolt, and in a low-altitude mission it must fly at subsonic speeds. In addition, the B-70 is not well suited to an era when both sides have large numbers of ICBMs. It would be more vulnerable on the ground than hardened missiles, and it does not lend itself to airborne-alert measures." Some of these criticisms were only partly true, but the political battle was on in earnest.
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<p>Later in 1962 the USAF shifted its stance from wanting 200 B-70s to a requirement for 150 RS-70 reconnaissance/strike aircraft. This was an error, swiftly pounced on by the opponents as soon as President Johnson revealed the Lockheed SR-71. By February 1964 Congress had virtually killed the program, leaving just two prototypes gutted of their military sub-systems. The first aircraft had looked complete in 1963, but over a year was spent trying to cure seepages of fuel through millions of microscopic holes, the special (modified JP-6) kerosene billowing away in vast smoke clouds as the tanks were bent and twisted at up to 554 degrees F (290 degrees C). Curing the seeping welds was almost the last straw, and when 62-001 was finally rolled out the no. 5 tank at the junction of fuselage and wing was still unusable (and so it remained).
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<p>USAF project pilot Colonel Joe Cotton and NAA chief test pilot Al White at last made the first flight on 21 September 1964, landing at Edwards and being slowed by three brake chutes. Mach 1 had been prevented by an inability to retract the main gears, and on touchdown a brake fault locked the two left rear main tires, which promptly blew. In general, however, flight development was encouraging, and remarkably close to prediction. Mach 3 was demonstrated on Flight 17. Cotton later said flying the B-70 was "like driving a Greyhound bus 200 mph round the track at Indianapolis." One of the few difficulties for the pilots was the need to aim to touch down about 2,500 ft (760 m) beyond the threshold, because the actual landing happened 110 ft (34 m) behind the pilot and 40 ft (12 m) lower down. On Flight 5 the wings were pivoted down to 65 degrees and, of course, they had to be horizontal before landing. The landing was cushioned by powerful ground effect, and at first the pilots found it hard to tell when the wheels had touched. There was always a heavy workload aboard, but the growing team of pilots were unanimous that the white monster was 'a truly great airplane'.
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<p>On 17 July 1965, 62-207 joined the flight program, and on its 39th flight, on 19 May 1966, showed the kind of mission the Valkyrie had been designed to fly. After climbing to cruise height it accelerated to Mach 3.08, and this was maintained for 33 minutes in the course of a 2,700-mile (4,354-km) journey through eight Western states. Much of the work by this time involved trailing sonic booms across instrumented routes in California and Nevada desert regions, in support of the planned US supersonic transport. NAA's own Phase I contract expired on 15 June 1966, to be replaced by a joint USAF/NASA Phase II program aimed mainly at SST back-up research.
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<p>Thus, on 8 June 1966, 62-207 aircraft was booked for a 'clean-up mission' with various tasks to complete Phase I, to which a sonic boom run was added at the final flight-plan conference. Engine builder General Electric had obtained permission on the usual 'noninterference' basis to organize a formation of GE-engined aircraft round the B-70 at the conclusion of the mission, for publicity pictures. As the workload was modest, Colonel Cotton let Major Carl S. Cross have his first familiarization ride as copilot. The sortie began at 0715, and soon after 0900 the tasks were done and GE-powered McDonnell F-4, Northrop F-5, Lockheed F-104 and Northrop T-38 formed up around it like minnows round a whale. By 0925 a GE-engined Learjet had got its pictures. The F-104, flown by Joe Walker, NASA's chief research pilot on the X-15 and probably the most experienced supersonic pilot in the world, gradually drifted very close under the right wingtip of the B-70. Suddenly, the fighter's tail actually struck the tip, the fighter reared up, rolled inverted and slid across the top of the B-70's wing. It carried away most of the B-70's rudders and then exploded in a fireball, falling away astern. The formation opened out, all eyes on the B-70. After what seemed about a minute it gradually began to oscillate, rolling and yawing until it went outside the design flight envelope. As it began to break up, Cotton ejected. Cross never even initiated the ejection sequence and his body was found in the wreckage.
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<p>To say a storm ensued would be to understate the situation. The USAF's antipathy to public relations exercises and aerial photography endures to this day, and for a long time the Pentagon was rather against 'the media' in general. Several careers of innocent people were blighted, and General Electric in particular wished the properly authorized formation had never been schemed.
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<p>Aircraft 62-001 continued to amass valuable research data, running on plain JP-6 fuel and instrumented for various NASA programs. Flown by Cotton, Lieutenant Colonel Fitz Fulton and Van Shepard, it was limited in its accomplishments only by the funding, and the last mission was regretfully flown on 4 February 1969. On this flight Fulton and Lieutenant Colonel Ted Sturmthal brought 62-001 in to land at Wright-Patterson AFB in Ohio. From its parking place it was towed to the USAF Museum where, along with a Convair B-36, it is the biggest exhibit. It was certainly right to start to B-70 program, and probably right to cancel it. Even the most vehement anti-bomber opponent of the early 1960s admitted that as a technical achievement this aircraft was in a class of its own.
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<p>What nobody in the USA then realized was the impact this program had on the USSR. While on the one hand Sukhoi built a bomber that looked very much like a slightly smaller B-70, on the other Mikoyan was ordered to build a fighter that could intercept the Mach 3 bomber. The result was the MiG-25, and this was continued even though the B-70 was not.
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<hi style=hdr1>Specification</hi>
<hi style=hdr2>North American—XB-70 Valkyrie</hi>
<list style=aflst>
<item><hi format=bold>Type:</hi> designed as four-seat strategic bomber
<item><hi format=bold>Powerplant:</hi> six 27,200-lb (121-kN) thrust General Electric J93-3 afterburning turbojets
<item><hi format=bold>Performance:</hi> maximum cruising speed 2,035 mph (3,275 km/h) or Mach 3.08; service ceiling 75,000 ft (22,860 m); unrefueled range 5,000 miles (8,050 km)
<item><hi format=bold>Weights:</hi> empty about 205,000 Ib (92,990 kg); maximum take-off 550,000 lb (249,476 kg)
<item><hi format=bold>Dimensions:</hi> span (tips extended) 105 ft 0 in (32.0 m); length 196 ft 6 in (59.89 m); height 30 ft 3 in (9.22 m); wing area 6,297 sq ft (585 m<su>2</su>)
<item><hi format=bold>Armament:</hi> no defensive weapons except electronics; provision for up to 14 nuclear or thermonuclear bombs, varied assortments of conventional bombs or (study only) externally carried stand-off missiles
