"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
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...
"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