A guided missile is a pilotless, self-propelled airborne vehicle or spacecraft that carries a destructive warhead to a preselected target.
There are many different types of missiles, and one way of classifying them is by their application. Strategic missiles can be used to attack an enemy’s home territory, while tactical missiles are used during the course of a battle. Developments in the capabilities of modern missiles have tended to blur this distinction though so that, for example, a cruise missile fitted with a nuclear warhead and targeted on an enemy city would be strategic, while the same missile fitted with antitank submunitions can have tactical applications.
Another way of differentiating between missiles is by the way they work; ballistic missiles are fired in a ballistic trajectory with the propulsion system acting during the first boost portion of the flight only. In aerodynamic types, the engines fire throughout the flight. A further classification favored by military analysts, since it provides a good description of the application, is based on the medium (land, sea, or air) from which the missile is launched and at which it is targeted. Thus, there are surface-to-surface missiles, air-tosurface missiles, air-to-air missiles, and so on.
Whatever the type or specific application, a missile consists of an airframe—with or without wings and fins—that houses a propulsion unit, a guidance system, and the warhead.
Airframe and propulsion system
The configuration and size of a missile are determined by its range and the size of the warhead package, since these determine the propulsion thrust and fuel load required. Largest of all are the strategic intercontinental ballistic missiles (ICBMs) with a range of at least 5,000 miles requiring multistage rocket motors, which take them to a height of up to 1,000 miles (1,600 km)during the boost stage. Speed at reentry is on the order of 15,000 mph (24,000 km/h), making interception difficult, while flight time is in the order of 25 minutes or less. The cylindrical fuel tanks for liquid propellant motors or the casings of solid-fuel motors often form the main structure of the missile, being arranged in a series of stages that are jettisoned in turn as the fuel is used up, leaving the warhead package to complete the trajectory to the target. Wings or fins are not generally fitted because most of the missile’s flight is outside Earth’s atmosphere, where aerodynamic control surfaces would be ineffective. The earliest successful U.S. ICBM was the Atlas, tested in 1959. It was quickly followed by the Titan and then the Minuteman. Currently, the United States uses Peacekeeper ICBMs, which are capable of carrying ten warheads.
Most of the above types of missiles have rocket motors; both solid- and liquid-fuel motors are used. Solid-fuel designs are generally preferred, since they can more readily be prepared for firing.
Other types of missiles have a cylindrical body fitted with cruciform wings and either cruciform tail fins or nose-mounted foreplanes. Cruise missiles, such as the Tomahawk, are air breathing with ramjet or turbojet engines and are designed to travel within Earth’s atmosphere. They tend to resemble piloted aircraft, with air intakes for the engines and wings or fins to sustain them in flight.
