North American XB-70
| North American XB-70 Valkyrie | |
|---|---|
 The XB-70 Valkyrie AV / 1 at takeoff |
|
| Type: | Prototype of a strategic bomber |
| Design country: | |
| Manufacturer: | |
| First flight: |
September 21, 1964 |
| Commissioning: |
Flight tests ended in 1969 |
| Production time: |
Was never mass-produced |
| Number of pieces: |
2 |
North American XB-70 Valkyrie ( German Walküre ) was the name of a US test aircraft from North American Aviation in the early 1960s. The XB-70 was supposed to show the feasibility of a strategic Mach 3 bomber , hence the addition “X” for “eXperimental status” in the name. Originally, the machine was to go into series production as the successor to the B-52 . However, the project was reduced to just two test vehicles before construction began. The key data of the designed machine corresponded to the doctrine of the time , which considered high altitudes and extremely high speeds to be necessary for future successful use.
history
Development goal
At the start of the project, the XB-70 was seen in competition with ICBMs on the one hand and nuclear-powered aircraft on the other. However, the aim of putting the B-70 into service was abandoned. The decisive factor was the high risk that an aircraft is exposed to from anti-aircraft missiles . At the same time, the USSR had made significant advances in radar technology. For a VHF radar, the B-70 would have been visible several hundred kilometers away.
With the advent of ballistic missiles with a long range and carrying capacity, the US and the Soviets introduced much cheaper ICBMs, which made the B-70 just as redundant as the Russian T-4 . Nevertheless, the development continued in order to gain experimental experience. The research results from the XB-70 program influenced US aviation for decades.
The Valkyrie is one of the most remarkable aircraft of all for size and speed. Technically, the XB-70 had many special features, for example with its six jet engines . The wing tips could be tilted downward up to 65 ° at high speeds to reduce drag and improve stability. To date, these are the largest adjustable aerodynamic flaps on an aircraft. The Valkyrie is also one of the noisiest aircraft ever built. Compared to other aircraft in this speed class, such as the Lockheed SR-71 Blackbird, the Valkyrie is more than twice as large.
The XB-70 was the first to use compression lift on an aircraft . The shock wave created by the air inlet is guided under the wings. In this way, lift could be increased by 30% without additional air resistance during supersonic flight. On the XB-70, this was additionally supported by the wing tips when they were fully folded down by generating an additional 5% compression lift. The folded-down wing tips also increased directional stability, so that the vertical stabilizers of the XB-70 could be small. This was the only way to achieve acceptable ranges at Mach 3.
A total of 128 flights were completed, 82 of them with the AV / 1. Test flights and roll-outs were spectacular events, often with celebrity guests.
An interceptor was also developed to accompany and protect the B-70 throughout the mission: the North American XF-108 Rapier. However, it did not get beyond the project stage.
Project progress
In 1955, Air Force General Curtis LeMay called for a successor to the B-52, which he believed was to be phased out in 1965 and which had not yet been introduced at the time. It was supposed to penetrate the enemy airspace at supersonic march speed and be introduced from 1964. The project was launched under the name "CPA" (chemical powered aircraft) WS-110A as a B-70 bomber. The Strategic Air Command planned 250 bombers, which according to the US Secretary of Defense Robert McNamara (under the administration of John F. Kennedy ) would cost about 10 billion US dollars. This was too expensive for him and in 1961 he stopped the "B-70" project with Kennedy backing. However, since more than 360 million US dollars had been spent on research and development by 1961 and the Concorde supersonic aircraft had been announced in Europe , an agreement was reached on the construction of three test aircraft XB-70 AV-1 to AV-3. The first Valkyrie AV-1 (USAF Serial No. 62-0001) flew for the first time on September 21, 1964. On March 24, 1965, it took off weighing over 500,000 pounds , the highest weight an aircraft could ever take off had picked up at the time. The second, AV-2, flew on July 17, 1965. A Mach-3 flight was first conducted on October 14, 1965, but revealed severe structural weaknesses in the AV-1, which was then limited to Mach 2.5. The construction of the AV-2 took place at a different time than the AV-1, so that findings from the construction of the first machine could be incorporated directly. Thus, the AV-2 showed various technical improvements and was ultimately able to fly permanently at Mach 3, in contrast to other combat aircraft that can only fly at this high speed for a few minutes, if at all. AV-2 reached Mach 3 for the first time on January 3, 1966. By June 1966, nine flights had been made at this speed. The third machine AV-3 was stopped shortly before final assembly. The three test aircraft should also research the basics for the SST project, a Mach 3 fast airliner project. However, the AV-3 was designed as a B-70 bomber with a four-man crew, computer-aided star navigation , IBM radar and digital computer and short dwell times on the ground (20 minutes in the air from a cold start and 7 minutes between landing and restarting).
A total of 63 flights with a total duration of 160 hours and 16 minutes were carried out by the AV-1; the AV-2 accumulated a total of 92 hours 22 minutes on 46 flights.
Aviation accident
On June 8, 1966, several US military aircraft (including the Valkyrie XB-70 AV-2, F-104 Starfighter , F-4 Phantom , Northrop T-38 Talon) carried out a formation flight for a photo opportunity, in which the most famous aircraft of the United States Air Force with General Electric engines in one photo. Shortly before the formation was supposed to break up after the actual photo session, the F-104 came out of the formation - without being asked or instructed to do so - too close to the XB-70.
The F-104 touched the right wing of the XB-70, presumably due to wake vortices , which were generated by the much larger XB-70 and its half-tilted wing tips . Then the F-104 was sucked by the air flow of the XB-70 over its delta wing surface. There it turned 180 °, collided roughly along the middle with the wing of the XB-70 and tore off both vertical stabilizers . The pilot of the F-104, Joe Walker , at the time the top test pilot at NASA, died immediately. The XB-70 continued to fly for about 16 seconds in normal flight position before it began to roll and, with decreasing maneuverability, finally north of Barstow hit the ground.
The co-pilot of the XB-70, Carl Cross, who had just joined the Valkyrie program, had failed to save himself on his first flight on the type. He had probably waited too long and because of the high centrifugal forces of the crash process failed later in the mechanism of the seat into the ausschießbare rescue capsule system should push back. Al White , the pilot of the XB-70 and at the same time chief pilot of North American and the Valkyrie project, was able to deploy the escape capsule and landed with it on the ground, but he was injured due to the non-deployed air cushion. He flew again six months later for NASA, but never again with the other remaining XB-70.
End of project and whereabouts
After losing the AV-2, the program was for a while with the remaining AV-1 - ultimately under the auspices of NASA - continued and the ferry flight on 4 February 1969 on the Wright-Patterson Air Force Base in Dayton (Ohio) completed . The AV-1 - the only surviving XB-70 Valkyrie - can be viewed today at the National Museum of the United States Air Force in Dayton, Ohio.
technical description
Concept and main weak point
The concept envisaged a strategic supersonic nuclear bomber with intercontinental range and extremely high penetration speed of permanently more than Mach 3. However, the proposals initially brought into play by Boeing and North American only met with strict rejection from the USAF leadership. To date, Boeing was almost the sole manufacturer of strategic bombers ( B-47 and B-52 ), but the second design from North American finally won the race due to the long wind tunnel testing and the clearly better concept (only it used the compression lift) possible successor to the B-52. Most jets could only maintain their top speed for a very short time. The B-70 was designed for long flight times at top speed. At the same time, however, as a result of extensive research work by Lockheed for the client CIA, a lot of basic knowledge about the location of aircraft using radar was gained. These findings spoke against a successful deployment. The cruising altitude, initially believed to be safe from missiles, has since turned out to be obsolete. The B-70 bomber concept was therefore reduced by the US Department of Defense to three, later two test aircraft, relatively early on before construction began.
Construction
The XB-70 was an all - metal low- wing aircraft , for the most part in steel sandwich construction with delta and duck wings . For this purpose, fundamentally new processes, such as electron beam welding in a vacuum, had to be developed for such large assemblies. The expected high temperatures at the fuselage and wing tips made the use of stainless steel and titanium necessary. The less temperature-resistant aluminum could only be used in less exposed and polluted areas. However, stainless steel has a lower strength than aluminum in relation to its weight . For this reason, many assemblies for weight reduction were manufactured using a honeycomb composite construction. This increased the development and manufacturing costs dramatically.
Airframe and flight characteristics
The delta wing had a leading edge sweep of 65.57 ° with almost straight leading edges which converged in the middle outside the fuselage contour below the front fuselage and above the vertical separating edge of the air inlet. On the basis of flight experience with the AV-1, the wings of the AV-2 were designed with a V-shape of 5 ° to improve the longitudinal stability . At about two-thirds of the half-span there was a longitudinally arranged hinge line on which the outer wings could be folded down in flight depending on speed and aerodynamic requirements. From about Mach 2.5, the two wing ends were folded down to a maximum of 64.5 ° on the first prototype and 69.5 ° on the second. This increased the efficiency of the compression effect and improved the directional stability. This made it possible to achieve considerably greater ranges than with conventional concepts. The extremely long and slender front fuselage generated a high yaw moment (torque around the vertical axis) in cross winds. The center of gravity and buoyancy , however, were far back. In order to achieve sufficient stability around the vertical axis, two large hydraulically operated were vertical stabilizers necessary. The elevator and ailerons, which are also hydraulically driven, were combined as elevons . In order to reduce the turbulence and thus the air resistance, the flaps were divided several times and thus made very narrow. This also reduced the operating forces to bearable values. The foldable ends of the wing required a complex and powerful hydraulic system in the wings. Due to the duck wing construction with the elevator located very far forward, the stall behavior was very good-natured. During the landings, the typical ground effect of delta wing aircraft caused a very soft touchdown. The slow flight characteristics of the XB-70 were also, as is typical of the delta, extremely good-natured and better than expected.
Hull and cockpit
The almost circular front fuselage was preassembled as a complete assembly in half-shell construction and placed on the main fuselage with wings in one piece. In the further course to the rear, the upper half-cross section of the fuselage merged with the almost flat top of the wing. In this area, shortly before the rear end of the back of the fuselage, there was a shaft for three braking parachutes , each 28 feet (approx. 8.50 m) in diameter, for braking after landing.
Under the wing delta, the lower part of the fuselage had a rectangular cross-section, the width of which increased in a wedge shape from the separating edge of the two air inlets towards the rear, and which merged into the engine cowling for the six turbojet engines arranged next to one another in the rear. In addition to the engine technology with the intake air duct, this lower part of the fuselage also contained the landing gear and the bomb bay. For the high-speed flight, the front cockpit windows had to be placed as flat as possible with a kind of visor. That would have resulted in extremely poor visibility during take-off and landing. Therefore, this windshield visor could be swiveled down with a complex mechanism during subsonic flight. The cockpit of the AV-1 and AV-2 machines was designed for two men (commander and copilot) with dual controls. The two-man cockpit created a high workload for the crew. The B-52 and the B-1 as an example have other crew members on board for navigation, radio, as well as attack and defense systems. The prototype AV-3 would then have received a four-man cockpit.
landing gear
The tripod landing gear had to carry a maximum take - off weight of 249 t. Due to the high landing weight and the landing speed - in order to protect the landing gear and the tires - all landings were completed with a very flat approach with a descent angle of only about 1.2 to 1.5 ° if possible.
The main landing gear was provided with four high-pressure tires each. These were provided with a silver-colored aluminum coating to keep the high temperatures away from the sensitive rubber in flight. The two main landing gears had only two relatively small landing gear shafts next to the air inlet ducts. To retract, a sequence was required in which the main landing gear legs had to be swiveled through 90 ° one after the other in two axes. This process was very complex, tested and optimized for a long time, but still caused problems on the first flights. Between the axles of the main tires there was a smaller, unbraked reference wheel , which, without the influence of the slip that occurs during braking, provided the speed information for the brake computer, which in turn controlled the automatic anti-skid system .
The nose landing gear was designed with twin tires and arranged centrally behind the engine air inlet openings. It was retractable to the rear and therefore had to be extended by the hydraulics against the wind; the very limited space between the air inlet ducts did not allow any other more functionally reliable solution.
Engines and fuel
The six General Electric YJ93-GE-3 turbojet engines of the XB-70 were among the few engines in the world designed for Mach 3. Together with the afterburner they reached a thrust of almost 830 kN. The engines were developed from the GE J79 (-X275) and were also the basis for the later GE4 engine. During measurement flights, heights of around 24,500 m (~ 75,000 ft) were reached. The YJ-93 engines were designed for long operation with afterburners. However, the fuel consumption increases almost threefold in afterburner operation.
Only through the use of high- energy boron fuels, so-called high-energy fuels (HEF), in the afterburners , which should run at Mach 3 during cruise, would the required range have been possible (according to the planning). The individual fuel candidates in this program have been numbered. For this purpose, the XB-70 was originally to be equipped with General Electric YJ93-GE-5 turbojet engines. These should not use JP-4 in their afterburner , but the highly toxic HEF-3 Ethyldekaboran with a significantly higher calorific value of 25,000 BTU / Ib (JP-4 only has a calorific value of 18,000 BTU / Ib). It was planned to use HEF-4 methyldekaborane throughout the engine later. In 1959, the toxic borane fuels were canceled, whereupon the newly developed JP-6 was used in the entire engine. JP-6 had a higher energy density than JP-4 and withstood higher temperatures. The planned range could also be achieved with an additional tank.
An air inlet each supplied three of the engines via a diffuser chamber . The air, which flows in very quickly at maximum speed, was led through the two inlets into two large chambers that widen towards the rear, in order to reduce the speed during expansion to a permissible, subsonic speed up to the compressor inlet. In front of the engines there were flaps at the top of the diffuser chamber, with which excess air could be diverted to the top of the fuselage during high-speed flight. The front end of the central partition between the two inflow channels was designed as a cutting edge and deflected the shock waves past the inlet openings at over Mach 1. The turbulent boundary layer from the underside of the fuselage was diverted past the inlet. The tip of this very boundary layer separator at the top front at the inlet came loose during a high-speed test flight, penetrated the right-hand shaft, destroyed engine no. 5 and also damaged the airframe. Immediate shutdown enabled the flight to be safely completed with the remaining engines. The relatively low thrust-to-weight ratio of 0.34 (tons of thrust to one ton of weight) made very long runways necessary. However, the high difference of 180 t between the empty weight (68 t) and the maximum take-off weight (249 t) indicated that the flight parameters were good when reaching cruising altitude. The engine mounts and connections were designed in such a way that a defective engine could be replaced on the airfield in just 25 minutes.
Radar Signature (RCS)
The very large radar cross-section - caused by the large outer flat surfaces of the air intake - ultimately tipped the balance to shorten the B-70 program to just two test aircraft XB-70. Since the XB-70 had very large rectangular air inlets and also six turbines, the radar echo was very large. The rudder arrangement, which formed right angles to the fuselage, was also problematic.
tank
The wings had three tanks on each side. Another five tanks were housed in the fuselage of the XB-70. On the first XB-70, however, one of the fuselage tanks could not be used. Air refueling was not planned for the AV-1 and AV-2, while this was planned for the later canceled machine AV-3 even at supersonic speed. For this purpose, the AV-2 was temporarily to be converted as a tanker and provided with a tank jib ("boom"). With this concept, a B-70 should accompany one to three other B-70s (as bombers) as a tanker and thus increase their range. A similar deployment concept was implemented a good 15 years later for the MRCA Panavia Tornado .
In order to compensate for the point of lift moving backwards with increasing speed, fuel could be pumped backwards in flight in order to bring the center of gravity back congruent with the point of lift. Otherwise the displacement would have to be trimmed aerodynamically with the flap position. That in turn would have increased the induced drag and thus reduced the speed and range.
A major problem was the high linear expansion caused by the heating during high-speed flight and thus the sealing of the tanks. The outgassing of the fuel would have been a high risk potential. Therefore, the tanks were pressurized with nitrogen so that no explosive fuel-air mixture could form inside the tanks.
Rescue system
A conventional ejection seat is no longer useful at speeds above Mach 2+ . At these high speeds, there is a risk that the strong head wind will destroy the pressure suit when it comes to the scrap, which in the thin mountain air would have led to immediate decompression and thus in all probability to death.
Therefore, a rescue capsule was used similar to that of the B-58 : in front of the committee, the ejection seat was quickly moved backwards in a rail. Arms and legs were pulled to the body with retrieval straps. A protective visor folded from behind over the entire ejection seat including the occupants and formed a capsule in which the occupant was protected from the attack of the airstream when leaving the cockpit. Only then was the seat encapsulated in this way shot up through the fuselage ceiling. After the scrap, the protective capsule had to be released from the seat after braking to a lower speed. From this point on, the function was analogous to that of a normal ejection seat, which the pilot releases via the seat separation.
When machine number 2 crashed, the system saved the life of pilot Al White, but it seriously injured his right elbow. Due to the strong centrifugal forces during the spin, the copilot Carl Cross was either no longer able to trigger the system or it failed.
Payload
In order to keep the air resistance and the radar echo low and to bring the range as high as possible, the designed weapon loads had to be carried in an internal bomb bay with large flaps. These unused rooms accommodated the measuring devices and sensors, which were still heavy at the time, during testing. The maximum take-off weight was 266% above the curb weight, which shows the extreme lightweight construction with high tank capacity and payload.
Technical specifications
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| Parameter | Data XB-70A Valkyrie |
|---|---|
| Type | Prototype of a high-speed strategic heavy bomber |
| crew | 2 |
| length | 59.74 m |
| span | 32.03 m |
| height | 9.12 m |
| Wing area | 585.62 m² |
| Wing loading | 414.7 kg / m² |
| Empty mass | approx. 68,400 kg |
| normal takeoff mass | 238,350 kg |
| Max. Takeoff mass ( MTOW ) | 249,500 kg |
| Marching speed | 3163 km / h |
| Top speed | Mach 3.08 or 3249 km / h at 22,250 m altitude |
| Service ceiling | 21,336 m |
| Max. Altitude | 24,385 m |
| Range | approx. 6,900 km |
| Armament | up to 14 nuclear free-fall bombs in an internal weapon bay (1) |
| Engines | six General Electric YJ93-GE-3 jet engines with 137.9 kN each |
| Thrust-to-weight ratio | 0.338 (with empty weight 1.233) |
| total cost | approx. $ 1.5 billion (2) |
(1) Both XB-70s were unarmed: The weapon bay was only theoretically designed for arming with the planned B-70 . The third XB-70, which is currently being planned, might have been able to carry weapons, but was stopped in the shell before final assembly.
(2) Many secret research projects of the US Air Force were mostly allocated to other larger projects in the budget in terms of costs, thus obscuring their existence. The high total shown (as of 1969) must therefore be questioned critically.
Further developments
Based on the findings of the flight tests and with significantly reduced requirements, the tender for a successor B-1 to be developed was then formulated. In the new tender, the speed was reduced to a maximum of Mach 2 and the number of engines to four. The fuselage should be rounded, without sharp edges and large flat surfaces. The radar echo should be significantly reduced by inclined partition walls in the engine inlets. The future mission profile has been changed to low attack or Hi-Lo-Hi . This made it possible to dispense with speeds of Mach 3+ and the use of the compression effect. The problematic fold-down surface ends could therefore give way to a "normal" swivel wing . This is also better suited for the gusts of wind during a fast low flight. The armament should be carried completely in weapon shafts in the fuselage. This requirement has been taken over from the XB-70 program, because it significantly reduces both air resistance and radar echo, while at the same time considerably increasing the possible speed and range.
After North American was taken over by Rockwell, this successor was developed by North American Rockwell (NAR) . The B-1 bomber went into production under the name Rockwell B-1 because NAR had meanwhile been renamed Rockwell International . In 1996 the aerospace sector of Rockwell International was finally taken over by Boeing .
Reactions to the XB-70
Soviet MiG-25 interceptor
As soon as the designs became known, the demand for a suitable interceptor in the same speed class quickly became loud in the Soviet Union . Mikoyan-Gurewitsch presented the design for the Mach 3 fast MiG-25. An irony of history was that the XB-70 was never mass-produced, but the interceptor that was supposed to fight this machine was very much. The MiG-31 was later developed from the MiG-25 .
Soviet projects Myasishchev M-56 and Tu-135
From 1957 studies on an M-56 were carried out at Myasishchev and from 1958 on a Tu-135 at Tupolev , which took up the concept variants of the B-70 project. After the two projects were merged, the Tu-135 design was abandoned in the mid-1960s for technical and political reasons.
Soviet long-range bomber Sukhoi T-4
The construction of the 10 ton lighter Suchoi T-4 was, apart from the missing foldable wing tips for the compression effect and the simple rudder, noticeably similar to the XB-70. The T-4 looks like a scaled-down XB-70. The distinctive air inlets, the fuselage, the landing gear and the wing geometry were similar. The visor of the XB-70, which significantly improved the pilots' vision during taxiing, take-off and landing, was of a much simpler design on the T-4, but meant that there was almost no forward view when flying straight ahead. When testing the four-engine T-4, a speed of about Mach 1.3 was not exceeded. The design available at the time would have been sufficient for Mach 1.9, which was well below the XB-70. The construction and maintenance, however, was foreseeably too expensive. With the increasingly powerful intercontinental ballistic missiles (ICBM) an effective deterrent could be realized with much lower costs. The otherwise demanding and promising project T-4 was discontinued after only one test machine for cost reasons. The XB-70 and the T-4 entered extremely uncharted aeronautical territory and both ultimately failed due to the very high costs involved - as did the conceptually comparable civil aircraft Tu-144 and Concorde after them.
See also
literature
- Dennis R. Jenkins, Tony R. Landis: Valkyrie: North American's Mach 3 Superbomber. Specialty Press, North Branch, Minnesota, USA 2004, ISBN 1-58007-072-8 .
- Jeannette Reamark, Joe Ventolo: XB-70 Valkyrie: The Ride to Valhalla. MBI Publishing Company, Osceola, Wisconsin, USA 1998, ISBN 0-7603-0555-2 .
- Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 .
Web links
- The North American XB-70A Valkyrie experimental aircraft ( Memento from December 26, 2005 in the Internet Archive )
- Federation of American Scientists - B-70 Valkyrie (English)
- "B70 - The State-of-the-Art-Improver - Part 1", Flight , edition of. June 25, 1964, page 1055 ff. , Available online at flightglobal.com - Aviation History - PDF archive, in English - accessed on January 2, 2016
- "B70 - The State-of-the-Art-Improver - Part 2", Flight , edition of. July 2, 1964, page 18ff. , available online at flightglobal.com - Aviation History - PDF archive, in English - accessed on January 2, 2016
- Articles on the entire XB-70 history, from planning to retirement
- 04: 28min video on YouTube (English)
- Aerospaceweb.org: North American XB-70
- USAF Museum: Factsheet North American XB-70
Individual evidence
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , p. 17.
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , p. 76.
- ↑ a b c d NASA Armstrong Fact Sheet: XB-70 Valkyrie , March 1, 2014 , English language, accessed January 3, 2016
- ^ North American's XB-70 "The Great White Bird," accessed December 10, 2017
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , p. 76.
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , pp. 98-99.
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , pp. 99-100.
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , pp. 99-100.
- ^ Abandoned & Little-Known Airfields
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , p. 84.
- ^ Abandoned & Little-Known Airfields
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , p. 81.
- ↑ Dennis R. Jenkins, Tony R. Landis: Warbird Tech Series Volume 34, North American, XB-70 VALKYRIE. Specialty Press, North Branch, Minnesota, USA 2002, ISBN 1-58007-056-6 , p. 34.
- ^ Tupolev Tu-135 Strategic Bomber on globalsecurity.org