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A missile is, broadly, a projectile, that is, something
thrown or otherwise propelled. Missiles can range from a rock thrown from a slingshot, through a crossbow bolt, to a Minuteman III intercontinental ballistic missile (ICBM) with multiple nuclear warheads.
Modern ICBMs, the largest missiles currently deployed, represent the most destructive weapons ever made in human history.
Rocket-powered missiles are known simply as rockets. Other missiles typically use some form of jet
engine for propulsion.
Missiles are often used in warfare as a means of delivering destructive force
(usually in the form of an explosive warhead) upon a target. Aside from
explosives, other possible types of destructive missile payloads are various forms of chemical and biological agents. Sometimes
missiles are used to deliver payloads designed to break infrastructure without harming people. For example, in the Gulf War cruise missiles were
used to deliver reels of carbon filament to electricity stations and
switches, effectively disabling them by forming short circuits.
Missiles which spend most of their trajectory in unpowered flight, and which don't use aerodynamics to alter their course, are
known as ballistic missiles (because their motion is governed by
the laws of ballistics). These are in contrast to cruise missiles which spend most of their trajectory in powered flight.
Guided Missiles
Missiles that have the ability to maneuver through the air can be guided, and are known as guided missiles. These have three key system components:
A tracking system locates the missile's target. This can be either a human gunner aiming a sight on the target (remotely from
the missile) or an automatic tracker. Automatic trackers use radiation emanating
from the target. Passive automatic trackers use the target's inherent radiation, usually heat or light, but missiles designed to
attack Command & Control posts may use radio waves.
Active automatic trackers rely on the target being illuminated by radiation. The target can be "painted" with light (sometimes
infrared) or radio waves (radar) which can
be detected by the missile. The radiation for the painting can originate in the missile itself or may come from a remote station
(for example, a hilltop gunner can illuminate a target with a laser device and this can
be used to direct an air launched guided missile).
A guidance system takes data from the missile's tracking system
and flight system and computes a flight path for the missile designed to intercept the target. It produces commands for the
flight system.
The flight system causes the missile to maneuver. There are two main systems: vectored thrust (for missiles that are powered
throughout the guidance phase of their flight) and aerodynamic maneuvering (wings, fins, canards, etc).
There are some similarities between guided missiles and guided bombs. A guided bomb, dropped from an aircraft, is unpowered and uses aerodynamic fins
for forward horizontal maneuvering while falling vertically.
See also
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