guided missile, self-propelled, unmanned space or air vehicle carrying an explosive warhead. Its path can be adjusted during flight, either by automatic self-contained controls or remote human control. Guided missiles are powered either by rocket rocket, any vehicle propelled by ejection of the gases produced by combustion of self-contained propellants. Rockets are used in fireworks, as military weapons, and in scientific applications such as space exploration.
..... Click the link for more information. engines or by jet propulsion jet propulsion, propulsion of a body by a force developed in reaction to the ejection of a high-speed jet of gas.

Jet Propulsion Engines

The four basic parts of a jet engine are the compressor, turbine , combustion chamber, and propelling nozzles.
..... Click the link for more information. . The American, R. H. Goddard Goddard, Robert Hutchings, 1882–1945, American physicist and rocket expert, b. Worcester, Mass., grad. Worcester Polytechnic Institute (B.S., 1908), Ph.D. Clark Univ., 1911. From 1914 he was associated with Clark Univ., becoming a professor of physics in 1919.
..... Click the link for more information. , did important early work on rockets, but guided missiles were first developed in their military form by the Germans, who in World War II employed V-1 and V-2 missiles against Great Britain and the Low Countries. The V-1 was the first cruise missile; it was powered through most of its flight and followed a straight-line trajectory to its target. The V-2, which was powered only during the first part of its flight, was the world's first operational ballistic missile, with a powered launch followed by an unpowered parabolic trajectory, sometimes guided by radio. Such missiles have since become the key strategic weapon of modern warfare and a crucial, and much used, tactical weapon.

Guided missiles are of various types and ranges. Missiles may be aerodynamic, i.e., controlled by aerodynamic surfaces and following a straight-line trajectory to the target, or ballistic, i.e., powered during flight and following a parabolic trajectory. Long-range missiles generally have nuclear warheads, while short-range missiles usually have high-explosive warheads.

Aerodynamic missiles are of four types. Air-to-air missiles are fired by aircraft at enemy aircraft and are often guided by self-contained controls that detect and target the missile toward heat sources. Surface-to-air missiles, such as the U.S. Patriot missile, operate against aircraft or other missiles. Both types may supplement antiaircraft guns. Air-to-surface missiles, launched by aircraft against ground positions, are generally radio-controlled. Surface-to-surface missiles (including ship and submarine launched versions) include many different types, such as antitank weapons. Longer-range surface-to-surface missiles, such as the Iraqi Scud, are in fact short-range ballistic missiles. Cruise missiles cruise missile, low-flying, continuously powered offensive missile designed to evade defense systems. Although the German V-1 (1944) was a simple cruise missile, the cruise missile did not realize its potential until the 1970s, when the United States sought to
..... Click the link for more information. , which are launched like a missile but use flipout wings and a turbofan engine to fly like an airplane to the target at altitudes of about 50 ft (15 m), are either air-to-surface or surface-to-surface missiles.

All long-range missiles are ballistic. The intermediate-range ballistic missile (IRBM) can reach targets up to 1,500 nautical miles away, while the intercontinental ballistic missile (ICBM) has a range of many thousands of miles. The first operational U.S. ICBM, the Atlas D, was controlled by radio, but since then inertial guidance, which uses internal gyroscopes to calculate and correct direction (sometimes with celestial, and then terrestrial readings), has been used. The key U.S. offensive ballistic missiles are the Minutemen ICBMs, which are launched from silos, and the submarine-launched Tridents, which replaced the earlier Polaris and Poseidon. All currently deployed ballistic missiles can be equipped with Multiple Independently Targetable Reentry Vehicles (MIRVs), which permit one booster to carry several warheads, each guided to a separate target. An antiballistic missile (ABM) is designed to detect and intercept enemy ballistic missiles. Space-, air-, sea-, and mobile land-based ABMs were barred by the 1972 ABM treaty, but the United States announced its withdrawal from that agreement in 2001.

The Soviet Union completed the first operative ICBMs in 1958, and the United States, reacting to a supposed "missile gap," gained overwhelming missile superiority by 1962, which in terms of accuracy and payload it never relinquished. Offensive and defensive ballistic missiles have been regulated by a number of arms control agreements between the United States and the USSR/Russia (see disarmament, nuclear disarmament, nuclear, the reduction and limitation of the various nuclear weapons in the military forces of the world's nations. The atomic bombs dropped (1945) on Japan by the United States in World War II demonstrated the overwhelming destructive potential of
..... Click the link for more information. ). Military ballistic missiles have been used as launchers for civilian space projects (see space exploration space exploration, the investigation of physical conditions in space and on stars, planets, and other celestial bodies through the use of artificial satellites (spacecraft that orbit the earth), space probes (spacecraft that pass through the solar system and that may
..... Click the link for more information. ).

Bibliography

See L. Martin, The Changing Face of Nuclear Warfare (1987); D. Mackenzie, Inventing Accuracy (1990).

guided missile

Projectile provided with means for altering its direction after it leaves its launching device. Almost all modern missiles are propelled by rocket or jet engines and have guidance mechanisms, usually including sensors, to help the missile find its target. Heat-seeking missiles, for example, carry infrared sensors that allow them to home in on the exhaust of jet engines.