Guided Missiles

I

Introduction

Guided Missiles, self-propelled aerial projectiles, usually containing conventional or nuclear explosives, guided in flight towards a target either by remote control or by internal mechanisms. Guided missiles vary widely in size and type, ranging from large strategic ballistic missiles with nuclear warheads to small, portable rockets carried by foot soldiers. Although most are military weapons with explosive warheads, others may carry scientific instruments for gathering information within or above the Earth’s atmosphere.

Guided missiles consist of three separate systems: power source, guidance and control mechanism, and warhead or payload. Power sources normally are either self-contained rocket motors or air-breathing jet engines, but may also be airfoils or outside booster charges from ramp or tube launchers. The type of guidance and control system employed depends on the type of missile and the nature of the target. Inertial guidance systems sense the position of the flight path in relation to a fixed target; other guidance systems use a variety of more active sensors to help direct the missile towards a moving objective. Payloads are generally warheads (bombs) designed for specific missions, from piercing armour plate to destroying entire urban areas (see Missile Warfare).

Not all missiles require guidance systems. Very short range missiles—artillery and sounding rockets (which may carry scientific instruments for collecting information within or above the Earth's atmosphere)—with ranges of up to about 90 km (56 mi), and efficient aerodynamics and high acceleration, can be delivered onto their targets with such accuracy that they do not require guidance. The range of more sophisticated systems can be increased to about 140 km (87 mi), although guidance is provided if great accuracy is required. The US Lance surface-to-surface missile with a range of about 120 km (74 mi), for example, was provided with guidance. At greater ranges, drag, wind, and drift spoil the accuracy of even the best-designed missile; the designers then have to rely on guidance for acceptable accuracy.

Some 90 countries have artillery rockets with ranges of up to 40 km (25 mi); about 40 countries have missiles with ranges of more than 40 km (25 mi); 12 countries have ballistic missiles able to deliver major payloads over ranges greater than 600 km (387 mi); and 9 countries have missiles with ranges greater than 1,500 km (930 mi), of which China, Russia, and the US have intercontinental ballistic missiles (ICBM) with ranges greater than 5,500 km (3,400 mi).

Before World War II guided missiles were limited to experimental, pilotless aircraft controlled by radio. During the war, however, rapid technological advances in such fields as aerodynamics, electronics, rocket and jet propulsion, radar, servo-mechanisms, inertial guidance and control systems, and aircraft structures, coupled with the intensive search for better weapons, led to the construction, testing, and finally mass production of the modern guided missile.

II

Warheads

Military guided missiles carry either high-explosive or chemical, biological, or nuclear warheads (see Chemical and Biological Warfare). Short-range tactical missiles employ high-explosive charges that produce damage through their force of impact and blast or through fragmentation. Anti-tank missiles, for example, normally depend on a concentrated blast effect to penetrate or splinter armour; warheads used against less protected targets such as aircraft rely more on fragmentation to produce the greatest damage.

Nuclear warheads are weapons of mass destruction carried primarily by an ICBM. To enhance the effectiveness of these long-range delivery systems, several types of warheads were developed in the 1970s. The multiple independently targeted re-entry vehicle (MIRV) dispatches several nuclear warheads from a single missile while in flight; the rocket-powered manoeuvrable alternative-target re-entry vehicle enables an individual warhead to change course as it falls. The Soviet-built fractional orbit bombardment system (FOBS) allows missiles or warheads to remain in Earth orbit before beginning their descent. FOBS gave the Union of Soviet Socialist Republics (USSR) the ability to launch a mass attack against the United States from any direction rather than just depending on a ballistic pathway arching over the North Pole.

The 1993 START II arms control agreement banned all ICBMs with MIRV but was never ratified by the US and Russia. It also attempted to limit submarine-launched ballistic missiles and called for the elimination of all multiple-warhead land-based missiles. However, during their November 2001 summit meeting in Washington, D.C., Presidents George W. Bush and Vladimir Putin agreed to attempt to make progress again in reductions in strategic nuclear forces. Bush announced that the US would unilaterally reduce the number of its operationally deployed strategic nuclear warheads to between 1,700 and 2,200 over the next ten years, substantially below the 3,500-warhead limit in the START II Treaty. Putin announced that the Russians would reduce the number of their operationally deployed strategic nuclear warheads to 1,500, but he did not say over what period of time this would be done.

Nuclear warheads are also used in several US air defence missiles with the intention of breaking up mass bomber formations. Most large tactical missiles are designed to carry nuclear warheads to destroy military concentrations on or behind the battlefield. In the 1980s, Soviet airborne or shipboard nuclear-tipped cruise missiles posed a threat to US Navy carrier task forces. A new type of nuclear weapon, the first to be added to the US arsenal since 1989, is being deployed by the United States. The weapons laboratory at Los Alamos has created the B61 “Mod 11”, an earth-penetrating warhead designed to destroy underground command and control installations.

III

Guidance and Control

Missiles are guided towards targets by remote control or by internal guidance mechanisms. Remote-control missiles are linked to a human or mechanical target locator through trailing wires, wireless radio, laser, or some other type of signal system. Internal guidance mechanisms have optical, radar, infrared, or some other type of sensor that can detect heat, light, or electronic emissions from the target. Most missiles have some type of movable fins or airfoil that can be used to direct the course of the missile towards the target while in flight.

The inertial guidance systems of ballistic missiles are more complex. Missile velocity, pitch, yaw, and roll are sensed by internal gyroscopes and accelerometers, and course corrections are made mechanically by slightly altering the thrust of the rocket exhaust by means of movable vanes or deflectors. In larger rockets, small external jets are also used to alter direction.

With laser-guided missiles an operator uses a laser to sight the target. After launch, the missile uses onboard sensors to look for the heat signal created by the laser on the target to acquire the target. The missile then homes in on the target, even a moving target. Laser guidance does not work in rain or when there is significant cloud cover. The disadvantages of laser guidance can be overcome by using the Global Positioning System (GPS) to navigate the missile to its target. GPS, which uses a satellite system to provide very accurate location, is not affected by weather conditions navigating the missile to the target. GPS-guided missiles have been tested but not yet used in action. GPS-guided missiles are tomorrow’s weapons, unaffected by adverse weather conditions, unrestricted by a wire, and not leaving any operator vulnerable.

IV

Missile Proliferation

The range and relative low cost of missiles make them the preferred means of delivery system for proliferating nations—those believed to be in the process of developing weapons of mass destruction. The Missile Technology Control Regime (MTCR) consists of 33 nations that have agreed to control exports of missile technology and equipment. China is as yet not a member of the MTCR, but is in the process of agreeing to its requirements, which refer to weapons of range 300 km (186 mi) or more, and carrying payloads of at least 500 kg (1,100 lb).

The United States and the former Soviet Union have in the past provided missiles to other powers, such as Israel and other Middle Eastern countries. India and Pakistan are said to have developed their own systems. China and Argentina, among others, are suspected of having been suppliers to other countries.

The Middle East, Far East, and Indian subcontinent are the prime areas threatened by missile proliferation. In the Gulf War, there was widespread fear that Iraq’s Russian-made Scud missiles, of 600 km (372 mi) range, may have been carrying chemical warheads; over 800 Scuds were fired during the conflict—ten of which had a range of 900 km (560 mi). The 600-km Scud-C was later made in Iraq. Israel has its own Jericho missiles, which have ranges of 650 km (403 mi) and 1,500 km (930 mi). North Korea, at the same time as being suspected of nuclear proliferation, has tested missiles based on the Scud of ranges 500 km (310 mi) and 1,500 km (930 mi); other nations in the region are feared to be developing or advancing their own programmes as a countermeasure.