Guided missiles form the cutting edge of all weapons of war today. The difference between the conventional weapons of yesteryear and the guided weapons is that, while the conventional weapon has to be launched in the correct direction with a lead angle to intercept the target at some future position, the guided weapon can be controlled in flight till interception to achieve destruction of the target. While guided missiles have become more and more sophisticated and smart, the fundamentals of missiles remain unchanged. A host of different disciplines of science and engineering go into the making of a guided weapon system. This chapter gives a bird’s eye view of the different types of guided missile systems, and the subsystems, which go to make up a guided missile system.
Depending on the environment from which the missile is launched and the environment in which the target is to be found, the guided missile (or weapon) systems are classified as follows:
• Surface-to-Surface Missile (SSM or SSW)
• Surface-to-Air Missile (SAM or SAW)
• Surface-to-Underwater Missile (SUM or SUW)
• Air-to-Surface Missile (ASM or ASW)
• Air-to-Air Missile (AAM or AAW)
• Air-to-Underwater Missile (AUM or AUW)
• Underwater-to-Surface Missile (USM or USW)
• Underwater-to-Air Missile (UAM or UAW)
• Underwater-to-Underwater Missile (UUM or UUW)
All these varieties do not necessarily exist. For example, UAMs are not practical propositions, and UUMs are really torpedoes. Any missile system whoset arget is a submarine like the SUM, will be a composite system, where the terminal underwater component is likely to be a homing torpedo. Guided missiles may also be classified as strategic or tactical, with further subdivisions depending on the role. Strategic missiles are large missiles, often with nuclear warheads and very long ranges, meant to destroy the enemy’s ability to wage war. Tactical missiles, on the other hand, are meant for battlefield use for the limited purpose of winning the battle or encounter. These can be of different kinds, depending on their roles.
Strategic Missiles
The target for strategic missiles will be a fixed position on earth, such as a city, troop forming up posistion, etc., whose coordinates are known a priori and the missile has to be programmed to fly to this geographical position. The guidance reduces to one of navigation to the target, which requires the missile to know continuously, its own position on the earth. The favoured method is ‘Inertial Navigation’, wherein the missile navigates to the target using inertial instruments like gyros and accelerometers. Celestial navigation – using stars for navigation – was an alternative to inertial navigation. It was used in some early missiles, but with navigation satellites in position, it is obsolete and currently, Global Positioning System (GPS), using navigation satellites becomes a possible alternative.
Strategic missiles may be launched from land (or a surface ship), a submarine, or an aircraft. Ground-launched missiles have to be protected against pre-emptive attacks or retaliatory attacks by the enemy. They may be launched, either from a hardened underground silo or from a mobile vehicle, whose position keeps changing all the time. Both trucks with cross-country capability and railway flatbeds can be used for this purpose. Ship, submarine and air launched missiles are obviously safer from this perspective. The range of strategic missiles is very large and they follow either a ballistic trajectory or a low altitude aerodynamic trajectory (also called the supported trajectory)