Cruise Missile, small pilotless aircraft that carries an explosive warhead. Cruise missiles can be launched from airplanes, trucks, ships, or submarines.

Modern cruise missiles are designed to be reliable and accurate. A typical example is the Lockheed Martin AGM-158 Joint Air-to-Surface Standoff Missile (JASSM). The JASSM weighs 1,000 kg (2,300 lb), has a range of more than 300 km (200 mi), and can be carried on fighter or bomber airplanes.

Cruise missiles are small and fast but can still be shot down, so designers make them stealthy (hard to detect on radar). To locate a cruise missile, an enemy uses a radar system to transmit radio waves that reflect off the missile or an airplane carrying the missile. The radar receives the reflected signals and thereby determines the speed and position of the cruise missile or the airplane carrying the missile. The stealthy cruise missile or airplane, however, is designed to thwart the radar system. For example, JASSM’s flat sides, pointed nose, and sweptback wings make it hard to detect on radar because any radar signals aimed at the missile bounce away from the radar that sent them out so the radar does not receive back any reflected signals.

A small jet engine powers a cruise missile, typically at speeds of more than 800 km/h (500 mph). The engine is controlled by a computer. In the JASSM, this computer was originally made to control automobile antilock brakes.

A cruise missile is designed to be extremely accurate. It is steered by an inertial navigation system (INS). Used on many airplanes and missiles, an INS measures every movement of the missile and every change of speed, constantly calculating the missile’s position. Any INS “drifts” or loses accuracy over time, like a clock, so current cruise missiles, such as the JASSM, also have a global positioning system (GPS) receiver that corrects the INS with the help of radio signals transmitted by GPS satellites.

Most modern cruise missiles, including the JASSM, have a precision guidance system that allows them to hit small targets. Before a cruise missile is launched, a photograph of the target is loaded into the missile’s computer. As the missile approaches the target, an infrared camera in the nose takes a picture and the computer matches it to the stored image. A cruise missile is so accurate that it can be aimed not just at a building, but at a specific place in the building, such as a door or window.

A cruise missile has a sharp nose and steel casing so that it can penetrate concrete bunkers. Warheads used in the JASSM cruise missile are filled with a type of explosive material that will not blow up if the warhead is dropped accidentally, or even if the airplane carrying the missile catches fire on the ground.

Other cruise missiles include the United States Navy’s Tactical Tomahawk, which is launched from ships and submarines using a rocket booster. A unique feature of this cruise missile is that it can be programmed with up to 15 targets. The missile flies to the first target on its list, and its camera sends a picture back to the ship via radio. If another Tomahawk has already hit the target, the controller can send the missile to its next target.

Some cruise missiles, including the Anglo-French Storm Shadow, use “terrain matching” guidance to help them navigate. Radar measures the height of the ground below the missile and compares these measurements with a three-dimensional map stored in the missile’s computer. Because ground contours are unique, these measurements enable the missile to determine its position.