Bomber crew save file location11/18/2023 Because of this, and a growing shift to the intercontinental ballistic missile (ICBM) force, the B-70 bomber program was cancelled in 1961 by President John F. The result would be an aircraft with somewhat higher subsonic speed than the B-52, but less range. Higher aerodynamic drag at low level limited the B-70 to subsonic speed while dramatically decreasing its range. The switch from high-altitude to low-altitude flight profiles severely affected the B-70, the design of which was tuned for high-altitude performance. The same effects also meant that low-flying aircraft were difficult to detect by higher-flying interceptors, since their radar systems could not readily pick out aircraft against the clutter from ground reflections (lack of look-down/shoot-down capability). This combination of effects made SAMs of the era ineffective against low-flying aircraft. Bombers flying at low altitudes could remain under these angles simply by keeping their distance from the radar sites. Additionally, radars of the era were subject to " clutter" from stray returns from the ground and other objects, which meant a minimum angle existed above the horizon where they could detect a target. This tactic greatly reduces radar detection distances through the use of terrain masking using features of the terrain like hills and valleys, the line-of-sight from the radar to the bomber can be broken, rendering the radar (and human observers) incapable of seeing it. The USAF Strategic Air Command (SAC) was aware of these developments and had begun moving its bombers to low-level penetration even before the U-2 incident. The XB-70 Valkyrie was chosen in 1957 to replace the Hustler, but suffered as a result of a switch in doctrine from high to low-altitude flying profilesīy the late 1950s, however, anti-aircraft surface-to-air missiles (SAMs) could threaten high-altitude aircraft, as demonstrated by the 1960 downing of Gary Powers' U-2. ![]() Soviet Union interceptor aircraft, the only effective anti-bomber weapon in the 1950s, were already unable to intercept the high-flying Lockheed U-2 the Valkyrie would fly at similar altitudes, but much higher speeds, and was expected to fly right by the fighters. In December 1957, the USAF selected North American Aviation's B-70 Valkyrie for this role, a six-engine bomber that could cruise at Mach 3 at high altitude (70,000 ft or 21,000 m). ![]() ![]() In 1955, the USAF issued requirements for a new bomber combining the payload and range of the Boeing B-52 Stratofortress with the Mach 2 maximum speed of the Convair B-58 Hustler. Main article: North American XB-70 Valkyrie The Northrop Grumman B-21 Raider is to begin replacing the B-1B after 2025 all B-1s are planned to be retired by 2036. and NATO military forces in Afghanistan and Iraq. It first served in combat during Operation Desert Fox in 1998 and again during the NATO action in Kosovo the following year. With the disestablishment of SAC and its reassignment to the Air Combat Command in 1992, the B-1B was converted for a conventional bombing role. By 1988, all 100 aircraft had been delivered. Dubbed the B-1B, deliveries of the new variant began in 1985 the plane formally entered service with Strategic Air Command (SAC) as a nuclear bomber the following year. The B-1A design was altered, reducing top speed to Mach 1.25 at high altitude, increasing low-altitude speed to Mach 0.96, extensively improving electronic components, and upgrading the airframe to carry more fuel and weapons. The program was restarted in 1981, largely as an interim measure due to delays in the B-2 stealth bomber program. The program was canceled in 1977, after the B-1A prototypes had been built. The combination of the high cost of the aircraft, the introduction of the AGM-86 cruise missile that flew the same basic speed and distance, and early work on the B-2 stealth bomber reduced the need for the B-1. This version had a top speed of Mach 2.2 at high altitude and the ability to fly for long distances at Mach 0.85 at very low altitudes. After a long series of studies, Rockwell International (now part of Boeing) won the design contest for what emerged as the B-1A. The B-1 was first envisioned in the 1960s as a platform that would combine the Mach 2 speed of the B-58 Hustler with the range and payload of the B-52, and was meant to ultimately replace both bombers. Air Force fleet along with the B-2 Spirit and the B-52 Stratofortress as of 2023. It is one of three strategic bombers serving in the U.S. It is commonly called the "Bone" (from "B-One"). ![]() The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. North American Rockwell/Rockwell International
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