Archive for the ‘Technology’ Category
The Northrop SM-62 Snark was a specialized intercontinental cruise missile with a W39 nuclear warhead operated by the U.S. Strategic Air Command from 1958 until 1961. It takes its name from Lewis Carroll’s snark.
The Snark was developed to offer a nuclear deterrence to the Soviet Union at a time when ICBMs were still in development. It was the only intercontinental surface-to-surface cruise missile ever deployed by the United States Air Force. With the deployment of ICBMs, it was rendered obsolete and taken out of service.
Design and development
Work on the project began in 1946. Initially there were two missiles — a subsonic design (the MX775A Snark) and a supersonic design (the MX775B Boojum). Budget reductions threatened the project in its first year, but the intervention of Jack Northrop and Carl Spaatz saved the project. Despite this, funding was low and the program was dogged by requirement changes. The expected due date of 1953 passed with the design still in testing and SAC was becoming less enthusiastic. In 1955, Eisenhower ordered top priority to the ICBM and associated missile programs. The original designation was B-62.
Despite considerable difficulties with the missile and military reservations toward it, work continued. In the 1957 tests the missile had a circular error probable (CEP) of only 17 nautical miles (31.5 km). By 1958 the celestial navigation system used by the Snark allowed its most accurate test, which appeared to fall 4 nautical miles (7.4 km) short of the target. However, this apparent failure was at least partially because the British Navigation Charts used to determine the position of Ascension Island were based on position determination techniques less accurate than those used by the Snark. The missile landed where Ascension Island would be found if more accurate navigation methods had been used when developing the chart. However, even with the decreased CEP, the design was notoriously unreliable, with the majority of tests suffering mechanical failure thousands of miles before reaching the target. Other factors, such as the reduction in operating altitude from 150,000 to 55,000 feet (46 to 17 km) and the inability of the system to detect countermeasures and perform evasive maneuvers also made the Snark an undesirable strategic deterrent.
The jet powered 20.5 m long unmanned aircraft had a top speed of 650 mph (1,046 km/h) and a maximum range of 5,500 nautical miles (10,200 km). The complex stellar navigation guidance system gave a claimed CEP of 8,000 ft (2.4 km).
The Snark was an air-breathing design, launched from a light platform by two rocket booster engines. It switched to an internal jet engine for the remainder of its flight. The jet was a Pratt and Whitney J57, the first 10,000 lbf (44 kN) thrust design, also used in the early B-52 and the F-100. Lacking a horizontal tail, the missile used elevons as its primary flight control surfaces, and flew an unusual nose high aspect during level flight. During the final phase of flight the nuclear warhead separated from the missile’s main body and followed a ballistic trajectory to the target. Upon separation, due to the abrupt shift in its center of gravity, the missile body performed an abrupt pitch-up maneuver to avoid colliding with the warhead.
One advanced feature of the Snark was its ability to fly missions of up to 11 hours and return for a landing. If the warhead did not detach, the missile could be flown repeatedly. Lacking landing gear, it was necessary for the Snark to skid to a stop on a flat, level surface. The runway at Cape Canaveral is still today known as the Skid Strip.