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Active Radar — A terminal phase guidance method in which a cruise missile emits its own radar signal, and then homes in on the energy reflected off the target.

Anti-Ship Cruise Missile (ASCM) — A type of cruise missile designed to strike sea-based targets ranging from small craft to aircraft carriers. ASCMs normally use radar and/or heat-seeking sensors to find and strike their targets.

Autonomous Target Acquisition (ATA) — A terminal phase guidance method in which a cruise missile can find locate and attack a target completely autonomously. Target data is not necessarily preloaded, as in the case of Digital Scene Matching Area Correlation (DSMAC).

Booster Rocket — A liquid- or solid-fuelled rocket that provides the initial thrust in a cruise missile launch from land or sea. After the booster burns out, thrust is provided by a sustainer motor, usually a jet engine.

Canard Stabilizer — A horizontal airfoil mounted in front of the main wing on a cruise missile. It reduces the lift-induced drag of the wing, and lowers the overall drag of the missile.

Circular Error Probability (CEP) — A simple measure of a cruise missile’s precision. It is defined as the radius of a circle into which the missile will land at least half the time.

Cruise Missile — A guided missile, the major portion of whose flight path to its target is conducted at an approximately constant velocity. It depends on the dynamic reaction of air for lift and upon propulsion forces (usually a jet engine) to balance drag. It is distinct from a ballistic missile, which follows a ballistic trajectory. A cruise missile can be launched from an aircraft, ship, submarine, or from land, and can be armed with a conventional or nuclear warhead.

Datalink — A means of connecting one location to another for the purpose of transmitting and receiving data. In cruise missiles, the datalink is used to send command and control signals and receive telemetry.

Delta Wing — A wing configuration in the shape of a triangle, named after the Greek uppercase delta (letter). The primary advantage of the delta wing design is that the wing’s leading edge remains behind the shock wave generated by the nose of the cruise missile when flying at supersonic speeds.

Digital Scene Matching Area Correlation (DSMAC) — A navigation system that compares terminal phase area imagery with preloaded satellite imagery that the cruise missile carries in its memory.

Global Positioning System (GPS) — A U.S. navigation system consisting of more than 24 satellites that allows a cruise missile to accurately determine its location in any weather, day or night, anywhere on Earth.

Global Navigation Satellite System (GLONASS) — A Russian navigation system similar to the U.S. Global Positioning System (GPS). Like GPS, the complete GLONASS constellation consists of 24 satellites allowing a cruise missile to accurately determine its location in any weather, day or night, anywhere on Earth.

Electronic Jamming — The deliberate radiation or reflection of electromagnetic energy for the purpose of disrupting enemy use of electronic devices or systems.

Forward-Swept Wings — A wing configuration, consisting of wings located further back on the body that angle forward (rather than backward as is the case with conventional-swept wings). Forward-Swept wings allow for increased maneuverability at supersonic speeds.

Fragmentation Warhead — A warhead that is designed to expel a large amount of shrapnel upon explosion.

Hypersonic Speed — A speed greater than Mach 5.0.

Imaging Infra-red Seeker (IIS) — A terminal phase guidance method in which a cruise missile can recognize the heat-based image of its target.

Infra-red (IR) — A terminal phase guidance method in which a cruise missile homes in on the heat emitted from its target.

Inertial Navigation System (INS) — A guidance system that measures a cruise missile’s acceleration in all three axes to determine its displacement from its launch point, and that determines its position. It is immune to electronic jamming.

Joint Direct Attack Munition (JDAM) — A “smart” bomb fitted with a tail control system and a Global Positioning System-aided inertial navigation system (INS).

Kiloton (kT) — An explosive force equivalent to that of 1,000 metric tons of TNT. It is used to rate the energy output, and hence the destructive power, of nuclear weapons.

Land-Attack Cruise Missile (LACM) — A type of cruise missile designed to strike land targets ranging in size from individual buildings to entire cities. LACMs are usually equipped with Global Positioning System and terrain-matching navigation systems that allow them to fly low-altitude, terrain-following, defense-evading paths.

Launch Phase — The initial phase of a cruise missile’s trajectory, during which the missile is guided by its inertial navigation system (INS).

Liquid Propellant — Any liquid combustible fed to the combustion chamber of a rocket engine.

Mach Number — The ratio of a cruise missile’s speed to the speed of sound (344 meters per second, 1,238 kilometers per hour). Objects with a speed of less than Mach 1.0 are known as “subsonic.” Objects with a speed of greater than Mach 1.0 are known as “supersonic.” Objects with a speed of greater than Mach 5.0 are known as “hypersonic.”

Megaton (MT) — A unit of explosive force equal to that of 1,000,000 metric tons of TNT. It is used to rate the energy output, and hence the destructive power, of nuclear weapons.

Midcourse Phase — The second phase of a cruise missile’s trajectory. During this phase, the missile is powered by a sustainer motor, usually a jet engine. It is guided by its inertial navigation system (INS) updated by one or more of the following systems: a radar-based terrain matching system, a radar or optical scene matching system, or a Global Positioning System-type satellite system.

Non-Nuclear Electromagnetic Pulse (EMP) Warhead — A payload designed to generate a non-nuclear electromagnetic pulse, which releases a high-intensity, short-duration burst of electromagnetic energy that can cripple electronic equipment within a certain radius.

Passive Radar — A guidance method in which a cruise missile detects and homes in on enemy radar emissions.

Penetration Warhead — A warhead that is designed to penetrate hardened targets, such as bunkers.

Precision Terrain Aided Navigation (PTAN) — A navigation system for cruise missiles currently in development by the U.S. that uses a worldwide digital database with radar maps.

Ramjet Engine — A newer type of cruise missile engine that contains no major moving parts and is ideally suited for high speed flight trajectories.

Sea-Skimming Trajectory — A low-level cruise missile trajectory, about 10 m above sea level. A warship under attack can only detect a sea-skimming missile when it emerges over the horizon at a distance of 15 to 25 nautical miles (28 to 46 km), which translates to only 25 to 60 seconds of warning time.

Stealth Technology — A range of techniques used by cruise missiles to make them less visible or invisible to radar and other detection methods. Stealth technology includes changing the shape of the missile body to minimize radar reflections, moving the engine air intake to hide the compressor face (normally a major radar return), and using a diffuser on the engine exhaust to minimize the infra-red signature.

Solid Propellant — A rocket propellant in solid form, combining both fuel and oxidizer in the form of a compact, cohesive grain.

Submunitions — Small bomblets contained in a larger warhead. Their primary purpose is to kill enemy infantry and vehicles, although submunitions have been designed for anti-runway, anti-armor, and mine-scattering purposes.

Subsonic Speed — A speed lower than the speed of sound (Mach 1.0; 344 meters per second, 1,238 kilometers per hour).

Supersonic Speed — A speed greater than the speed of sound (Mach 1.0; 344 meters per second; 1,238 kilometers per hour).

Sustainer Motor — A motor, usually a jet engine, that powers the cruise missile during its midcourse and terminal phases.

Tailplane — The fixed horizontal airfoil of a cruise missile’s tail assembly.

Television Imaging (Electro-Optical Imaging) — A navigation system for cruise missiles in which an electro-optical seeker scans a designated area for targets via optical imaging. Once a target is acquired, the missile will lock on to it for the kill. TV imaging does not depend on a target’s heat signature, and thus can be used against low-heat targets. The system, however, has the drawback that the target must be “seen” by the missile, which limits its range of action.

Terminal Phase — The third and final phase of a cruise missile’s trajectory. The terminal phase begins when the missile enters the target area and uses either more accurate terrain-matching guidance technology, or a terminal seeker (usually an optical or radar-based seeker).

Terrain Contour Matching (TERCOM) — A navigation system for cruise missiles that uses an on-board contour map of the terrain over which the missile flies over. TERCOM “sees” the terrain it is flying over using its radar system and matches it to an internally stored ground-map.

Terrain Profile Matching (TERPROM) — A navigation system for cruise missiles that uses stored digital elevation data combined with navigation system and radar altimeter inputs to compute the location of the aircraft or missile above the surface of the earth.

Thermobaric Warhead — A warhead that expels a cloud of explosive mist using a small charge and then ignites it with a second charge, thus producing greater explosive energy. Thermobaric warheads are also known as a fuel-air munitions, heat and pressure weapons, or vacuum bombs.

Transporter-Erector-Launcher (TEL) — A ground vehicle capable of carrying and firing one or more cruise missiles.

Turbofan Engine — A newer type of cruise missile engine, similar to a turbojet. It consists of a ducted fan with a smaller diameter turbojet engine mounted behind it that powers the fan. Part of the air stream from the ducted fan passes through the turbojet where it is burnt to power the fan, but the majority of the flow bypasses it and produces most of the thrust.

Turbojet Engine — An older type of cruise missile engine consisting of a turbine-driven compressor that expels hot gases and produces a high velocity jet in the exhaust plume. The momentum of the exhaust stream propels the missile forward.