"The XB-70 Valkyrie is the prototype of the B-70 nuclear-armed, deep-penetration strategic bomber for the U.S. Air Force's Strategic Air Command. Only two aircraft were ever built, and the program was cancelled before production had a chance to begin.
The XB-70 was powered by six General Electric YJ93s capable of generating 30,000 lbs. thrust each, with afterburner. North American Aviation designed the Valkyrie to be able to reach speeds in excess of Mach 3 while flying at 70,000 feet. The B-70 was expected to easily outrun any enemy interceptor aircraft—the only effective weapon against bomber aircraft at that time. The Valkyrie would spend only a few minutes over a particular radar station, flying out of its range before the controllers could vector their fighters into a suitable location for an interception. Its high speed made the aircraft difficult to see on radar, and its high altitude could not be matched by any contemporary Soviet fighter." Popular Mechanics
NASA Armstrong Fact Sheet: XB-70 Valkyrie
"The B-70 Valkyrie, with a planned cruise speed of Mach 3 and operating altitude of 70,000 feet, was to be the ultimate high-altitude, high-speed manned strategic bomber. Events, however, would cause it to play a far different role in the history of aviation.
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 off, landing, and subsonic flight, they remained in the horizontal position. This feature increased the amount of lift produced, improving the lift-to-drag ratio. Once the aircraft was supersonic, the wing panels would be hinged downward. Changing the position of the wing panels reduced the drag caused by the wingtips interacted with the inlet shock wave. The repositioned wingtips also reduced the area behind the airplane's center of gravity, which reduced trim drag. The downturned outer panels also provided 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.
As impressive a technological feat as the B-70 represented, the aircraft 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 program was canceled.
At the same time there was growing interest in an American supersonic transport (SST). Jet airliners had cut flight times by more than half in comparison to propeller-powered aircraft. A Mach 2 or 3 SST would make a similar improvement over the new subsonic jet airliners. The Flight Research Center (FRC-now the Dryden Flight Research Center, Edwards, CA.) had several SST studies underway during the early 1960s. NASA's Douglas F5D-1 was used for landing studies, a North American F-100C was modified to simulate SST handling qualities, a North American A-5A was used to simulate an SST for tests of the air traffic control system, and a Lockheed JetStar was modified as an in-flight SST simulator." NASA
NASA Armstrong Fact Sheet: XB-70 Valkyrie continued...
"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 flown.
The XB-70A number 1 (62-001) made its first flight from Palmdale to Edwards Air Force Base, CA, on Sept. 21, 1964. Tests of the XB-70's airworthiness occurred throughout 1964 and 1965 by North American and Air Force test pilots. The Flight Research Center prepared its instrument package. Although intended to cruise at Mach 3, the first XB-70 was found to have poor directional stability above Mach 2.5, and only made a single flight above Mach 3. Despite the problems, the early flights provided data on a number of issues facing SST designers. These included aircraft noise, operational problems, control system design, comparison of wind tunnel predictions with actual flight data, and high-altitude, clear-air turbulence.
NASA Ames Research Center, Moffett Field, CA, wind-tunnel studies led engineers at North American Aviation in Downey, CA, to build the second XB-70A (62-207) with an added 5 degrees of dihedral on the wings. This aircraft made its first flight on July 17, 1965. The changes resulted in much better handling, and the second XB-70 achieved Mach 3 for the first time on Jan. 3, 1966. The aircraft made a total of nine Mach 3 flights by June.
At the same time, a joint agreement was signed between NASA and the Air Force to use the second XB-70A prototype for high-speed research flights in support of the SST program, selected due to its better aerodynamics, inlet controls, and a much superior instrument package, compared to the first aircraft. The NASA research flights were to begin in mid-June, once the North American Aviation Phase I tests of the vehicle's airworthiness were completed. NASA research pilot Joe Walker was selected as the project pilot. The flights were to evaluate the aircraft on typical SST flight profiles, and to study the problems of sonic booms on overland flights.
These plans went awry on June 8, 1966, when the second XB-70 crashed following a midair collision with NASA's F-104N chase plane. Joe Walker, F-104N pilot, died in the accident. North American test pilot Al White ejected from the XB-70 in his escape capsule, but received serious injuries in the process. Co-pilot Maj. Carl Cross, who was making his first flight in the XB-70, was unable to eject and died in the crash." NASA
Last XB-70 at the Air Force Museum
"The plane is moving into the museum's 224,000-square foot fourth building, which is scheduled to open to the public in June 2016. It will house four galleries—R&D (where the Valkyrie will live), Space, Global Reach, and Presidential—along with three science, technology, engineering and mathematics (STEM) Learning Nodes. The construction of the newest hangar was privately financed by the Air Force Museum Foundation, which gifted more than $40 million for the construction. The public will be able to view aircraft as they move into the fourth building from a designated area on the museum grounds. Information on the move schedule will be updated regularly on the museum's website. A map of the viewing area and additional information about the expansion also are available on that page." Popular mechanics. Article here...
Above- 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 XB-70 was designed to use supersonic technologies developed for the Mach 3 Navaho, as well as a modified form of the SM-64 Navaho's all-inertial guidance system.
NASA Armstrong Fact Sheet: XB-70 Valkyrie continued...
The deaths of Walker and Cross, and the destruction of the second XB-70 had major consequences for the research program. The second XB-70 had been selected for the Phase II tests, which were to be conducted jointly by NASA and the Air Force. With this aircraft now destroyed, only the first aircraft was available. Given the aircraft's shortcomings, the Air Force began to doubt that it would be able to meet the Phase II test goals.
The first XB-70 was undergoing maintenance and modifications at the time of the accident to its sister ship. It did not fly again until Nov. 3, 1966. Col. Joe Cotton piloted it, while NASA research pilot Fitzhugh Fulton served as co-pilot. The flight reached a top speed of Mach 2.1. Between November 1966 and the end of January 1967, a total of 11 joint Air Force/NASA research flights occurred. Cotton, Fulton, and Van H. Shepard of North American Aviation were crewmen on these flights. A top speed of Mach 2.57 was the highest attained during the remainder of the XB-70 program.
These flights were made as part of the National Sonic Boom Program. The XB-70 flew at differing altitudes, Mach numbers, and weights over an instrumented test range at Edwards. The "boom carpet" area was determined and the overpressure measured on two specially constructed housing units. The tests showed that a large aircraft, such as the XB-70 or the projected SST, could generate overpressures high enough to cause damage. Moreover, when the XB-70 made a turn, its shock waves converged, and often doubled the overpressure on the ground.
NASA Armstrong Fact Sheet: XB-70 Valkyrie continued...
Following these tests, the XB-70 was grounded for maintenance that lasted 2 1/2 months. The Air Force had concluded by that point that the XB-70 program should be turned over to NASA as soon as possible. FRC director Paul Bikle and Air Force Flight Test Center (AFFTC) commander Maj. Gen. Hugh Manson created a joint FRC/AFFTC XB-70 operating committee on March 15, 1967. This was patterned on similar committees established for the X-15 and lifting bodies. The NASA XB-70 program continued to receive Air Force assistance, in terms of aircraft support and Air Force test pilots.
The first NASA XB-70 flight occurred on April 25, 1967, by Fulton and Cotton. By the end of March 1968, another 12 research flights had been completed. The pilots included Fulton, Cotton, and Shepard, as well as Lt. Col. Emil Sturmthal and NASA research pilot Don Mallick. The flights acquired data to correlate with an Ames ground-based SST simulator and the JetStar in-flight SST simulator at FRC. Other XB-70 research goals were to measure its structural response to turbulence; determine the aircraft's handling qualities during landings; and investigate boundary layer noise, inlet performance, and structural dynamics, including fuselage bending and canard flight loads.
The XB-70 underwent modifications after a final flight on March 21, 1968. During research flights, the XB-70 pilots had frequently experienced trim changes and buffeting during high-speed, high-altitude flights. These resulted from clear-air turbulence and rapidly changing atmospheric temperatures. For a specialized research aircraft, these characteristics were little more than annoying; on a commercial SST, however, they would be uncomfortable for the passengers, increase the pilots' workload, and shorten the structural fatigue life of the SST." NASA
Above- Restoration crews at the National Museum of the U.S. Air Force moved the North American XB-70 Valkyrie into the museum’s new fourth building during the last week of October 2015. The aircraft – the world’s only remaining XB-70 – will be displayed in the new Research & Development (R&D) Gallery and open to the public in June 2016. Interview with National Museum of the U.S. Air Force Curator Jeff Duford. The National Museum of the U.S. Air Force’s new $40.8 million fourth building including aircraft such as SAM 26000 (Air Force One) and the only remaining XB-70 Valkyrie, will open to the public on June 8, 2016.
NASA Armstrong Fact Sheet: XB-70 Valkyrie continued...
"The XB-70 was fitted with two small vanes for the Identically Located Acceleration and Force (ILAF) experiment. The vanes rotated 12 degrees at a rate of up to 8 cycles per second. This induced a structural vibration in the XB-70 at a known frequency and amplitude. The XB-70's accelerometers detected the disturbances, then signaled the aircraft's stability augmentation system to damp out the motion. When XB-70 research flights resumed on June 11, 1968, the ILAF proved its ability to reduce the effects of turbulence and atmospheric temperature changes.
Despite the accomplishments of the XB-70, time was running out for the research program. NASA had reached an agreement with the Air Force to fly research missions with a pair of YF-12As and a "YF-12C," which was actually an SR-71. These represented a far more advanced technology than that of the XB-70. In all, the two XB-70s had logged 1 hour and 48 minutes of Mach 3 flight time. A YF-12 could log this much Mach 3 time in a single flight.
The final XB-70 research flight occurred on Feb. 4, 1969. Fulton and Sturmthal made a subsonic structural dynamics test and ferry flight. The XB-70 took off from Edwards and flew to Wright-Patterson Air Force Base, OH, where the aircraft was put on display at the Air Force Museum. The first XB-70 made 83 flights totaling 160 hours and 16 minutes, while the second XB-70 logged 46 flights in its brief life, totaling 92 hours and 22 minutes." NASA
"The XB-70 was equipped with six General Electric YJ93-GE-3 turbojet engines, designed to use JP-6 jet fuel. The engine was stated to be in the "30,000-pound class", but actually produced 28,000 lbf (124.6 kN) with afterburner and 19,900 lbf (88 kN) without afterburner. The Valkyrie used fuel for cooling; it was pumped through heat exchangers before reaching the engines. To reduce the likelihood of auto ignition, nitrogen was injected into the JP-6 during refueling, and the "fuel pressurization and inerting system" vaporized a 700 lb (320 kg) supply of liquid nitrogen to a gas to fill the fuel tank vent space and maintain tank pressure." Wiki
"The Valkyrie was fast, but it was not easy to fly. It took both pilots to keep it flying straight and level. To save weight the XB-70 used a 5000v electrical architecture, and a 5000 psi hydraulic system. It got rid of it's extra heat by transferring it into the fuel, and also carried 1 ton of water that could be boiled away to dissipate any heat the fuel could not hold. The hydraulic fluid had a working temp. of 450 F and could withstand temps as high as 750 F. None the less, the Valkyrie would often overheat it's hydraulic fluid to the point of needing replacement. The main landing gear did not always operate properly, and several times the aircraft had to land with one of the main gear trucks locked in the vertical position (tippy toe landing). One of the two Valkyries had 2 degrees of dihedral in the wings the other had flat wings. The aircraft with the dihedral was even harder to fly. This was an extremely complex aircraft that was hard to build, maintain, and fly. I am amazed that such a project could be accomplished in the early 60's, and, sadly, it would seem that one of the lessons we took away from it was; don't ever try anything like that again." James Monahan
"The XB-70A, built by the North American Aviation (NAA) Los Angeles Division for the U.S. Air Force, was an experimental high-speed, delta-wing aircraft designed to fly at three times the speed of sound and higher than 70,000 feet (21,000 kilometers).
On Sept. 21, 1964, 5,000 employees and guests at Air Force Plant 42 in Palmdale, Calif., watched as NAA Chief Pilot Alvin White and U.S. Air Force copilot Joseph Cotton took the graceful six-engine giant up for its first flight. It was the culmination of an effort that began in 1954, when both Boeing and NAA submitted designs for the Air Force Weapon System 110A competition, and on Dec. 23, 1957, NAA won the competition.
However, federal budget cutbacks and advances in Soviet air defenses resulted in an emphasis on less expensive and theoretically more survivable intercontinental ballistic missiles as the mainstay of U.S. nuclear forces. On April 10, 1961, the Air Force cut back the B-70 to a research program, and only two of the aircraft would be built. A second Valkyrie, the XB-70A-2, flew on July 17, 1965." Boeing. More here...
WORLDS FASTEST BOMBER Aircraft us air force XB-70 Valkyrie
Close Look at New Plane- 1964
XB-70 Valkyrie Ship 2 Photos Slide Show
Images Courtesy- Thornton D. Barnes
The XB-70 used compression lift, which was generated from a prominent wedge at the center of the engine inlets that created a shock wave below the aircraft. The wing included inboard camber to more effectively use the higher pressure field behind the strong shock wave (the airflow at the XB-70 wing's leading edge was subsonic). The compression lift increased the lift by five percent. Unique among aircraft of its size, the outer portions of the wings were hinged, and could be pivoted downward by up to 65 degrees. This increased the aircraft's directional stability at supersonic speeds, shifted the center of lift to a more favorable position at high speeds, and strengthened the compression lift effect.With the wingtips drooped downwards, the compression lift shock wave would be further trapped under the wings. The XB-70 was equipped with six General Electric YJ93-GE-3 turbojet engines, designed to use JP-6 jet fuel. The engine was stated to be in the "30,000-pound class", but actually produced 28,000 lbf (124.6 kN) with afterburner and 19,900 lbf (88 kN) without afterburner. The Valkyrie used fuel for cooling; it was pumped through heat exchangers before reaching the engines. To reduce the likelihood of autoignition, nitrogen was injected into the JP-6 during refueling, and the "fuel pressurization and inerting system" vaporized a 700 lb (320 kg) supply of liquid nitrogen to fill the fuel tank vent space and maintain tank pressure.
Above- TECHNICAL NOTES:
Compressor: 11-stage axial flow with variable stators
Thrust: 30,000 lbs. with afterburner
Weight: 4,770 lbs.
Below- XB-70 SUPERSONIC STRATEGIC BOMBER MACH 3 FLIGHT TEST FILM