B-1 Lancer

The B-1 Lancer is a strategic bomber used by the United States Air Force. First envisioned in the 1960s as a supersonic bomber with sufficient range and payload to replace the B-52 Stratofortress, it developed primarily into a low-level penetrator with long-range and capable of supersonic speed. The design was canceled and reinstated multiple times over its lengthy development history, as the theory of strategic balance changed from flexible response to mutually assured destruction and back again. It eventually entered service more than 20 years after first being studied.

The B-1B production version has been in service with the United States Air Force (USAF) since 1986. The Lancer serves as the supersonic component of the USAF's long-range bomber force, along with the subsonic B-52 and B-2 Spirit. The bomber is commonly called the "Bone" (originally from "B-One"). With the retirement of the EF-111 Raven in 1998 and the F-14 Tomcat in 2006, the B-1B is the U.S. military's only variable-sweep wing aircraft.

Development
The B-1 was conceived as the Advanced Manned Strategic Aircraft (AMSA) program around 1965. AMSA was the last in a series of 1960s programs that looked at replacing the B-52 with a long-range multi-role supersonic aircraft that could drop bombs and launch nuclear missiles.

The Valkyrie and changing tactics
In December 1957, U.S. Air Force selected North American Aviation's proposal to replace the B-52 Stratofortress. This would lead to the B-70 Valkyrie. The Valkyrie was a six-engine bomber that could fly very high at Mach 3 to avoid interceptor aircraft, the only effective anti-bomber weapon in the 1950s. At the time, Soviet interceptors were unable to intercept the high-flying Lockheed U-2; the Valkyrie was to fly at similar altitudes and much higher speeds. But by the late 1950s, anti-aircraft surface-to-air missiles (SAMs) could threaten high-altitude aircraft, as demonstrated by the downing of Gary Powers' U-2 in 1960.

Recognizing this, the USAF Strategic Air Command had begun moving to low-level penetration before the U-2 downing. This greatly reduces radar detection distances while at that time SAMs were ineffective and interceptors less effective against low-flying aircraft. Also the flight path to a target could be routed around known anti-aircraft sites, and the landscape could be used to the bomber's advantage to stay out of the radar's line-of-sight operation. Aircraft speed became much less important. The targets themselves often had defenses located nearby to prevent this sort of approach all the way in, but stand-off weapons such as the AGM-69 SRAM provided an attack capability from outside the defensive missile's range. Low-altitude flight also made the bombers very difficult to detect from aircraft at higher altitudes, including interceptors, as radar systems of that generation could not "look down" due to the clutter that resulted from ground reflections.

Operations at low levels would limit the B-70 to subsonic speed, while dramatically decreasing its range due to much higher fuel requirements. The result would be an aircraft with similar speed but much less range than the B-52 it would have replaced. The Mach 2 B-58 was similarly limited to subsonic speeds at low altitudes. Unsuited for this new role, the viability of the B-70 as a bomber was questioned. Citing high cost, a growing ICBM force, and poor survivability against missiles, the operational bomber fleet was canceled in 1961 by President John F. Kennedy, and the program was changed to a supersonic research program with two XB-70 prototype aircraft.

B-1A program
President Richard Nixon re-established the program after taking office, in keeping with his administration's flexible response strategy that required a broad range of options short of general nuclear war. Secretary of Defense Melvin Laird reviewed the programs and decided to lower the numbers of FB-111s, claiming it lacked the required range, and recommended that the AMSA design studies be accelerated. In April 1969 the program officially became the B-1A. This was the first entry in the new bomber designation series, first created in 1962.

After the prolonged development period, the production contract was finally awarded in 1970. The original program called for two test airframes, five flyable aircraft, and 40 engines. This was cut in 1971 to one ground- and three flight test aircraft (74-0158 through 0160). First flight was set for April 1974. The company changed its name to Rockwell International and named its aircraft division North American Aircraft Operations in 1973. A fourth prototype (76-1074) was ordered in the FY 1976 budget. This fourth aircraft was to be built to production standards. At one time, some 240 B-1As planned to be built, with initial operational capability set for 1979.

Rockwell's design featured a number of features common to 1960s U.S. designs. These included the use of variable-sweep wings in order to provide both high lift during takeoff and landing, and low drag during a high-speed dash phase. With the wings set to their widest position the aircraft had considerably better lift and power than the B-52, allowing it to operate from a much wider variety of bases. Penetration of the USSR's defenses would take place in a dash, crossing them as quickly as possible before entering into the less defended "heartland" where speeds could be reduced again. The large size and fuel capacity of the design would allow this dash portion of the flight to be relatively long.

In order to achieve the required Mach 2 performance at high altitudes, the air intake inlets were variable. In addition, the exhaust nozzles were fully variable. Initially, it had been expected that a Mach 1.2 performance could be achieved at low altitude, which required that titanium be used in critical areas in the fuselage and wing structure. However, this low altitude performance requirement was lowered to only Mach 0.85, reducing the amount of titanium, and the overall cost.

Crew escape was provided for using an escape pod that ejected a portion of the entire cockpit with both pilots inside, as opposed to the more conventional ejection seats; it was felt that egress during a high-speed, high-altitude dash would be too dangerous without pressurization. A pair of small canards mounted near the nose are part of an active vibration damping system that smooths out the otherwise bumpy low-altitude ride, reducing crew fatigue and improving airframe life.

An extensive suite of electronics was planned, including a Litton LN-15 inertial navigation system, a Doppler radar altimeter, a Hughes forward-looking infrared, a General Electric APQ-114 forward-looking radar and a Texas Instruments APQ-146 terrain-following radar. The terrain-following radar, in particular, would allow the B-1 to fly at much lower altitudes during the "dash" phase of the mission than the B-52, which relied on older systems that demanded higher minimum altitudes during bad weather.

Overall it had a range similar to that of the B-52, although more of the flight could be low-level. A combination of flying lower due to better navigation systems and a greatly reduced radar cross section made it much safer from attack by missiles, and the latter also improved its odds against fighters as well. In situations where fighters were the expected competition (i.e. outside the USSR), its high-speed dash was a potentially useful technique the B-52 could not match. A convincing B-52 replacement had arrived.