Guidance and control

For any guided weapon system the accent must be upon guidance.

Guidance covers two distinct technical problems: first the control of the attitude of the missile, and secondly, the control of the path of the missile. The former ensures correct orientation of the vehicle in space, while the latter has to be solved so that the missile while reach its target. Moreover, attitude control must be effected before path guidance can be attempted.

There are essentially three stages in the guidance of any missile. First is known as the launching phase when control must be employed in order to correct any dispersion following the takeoff, so that the missile can be directed into the correct path for it to enter the next phase of midcourse guidance. Then the guidance system must ensure that the missile’s warhead is carried as close as possible to the target with the minimum of time delay. The missile next enters its final stage of terminal guidance in which it has to be brought within lethal distance of the target. Finally the warhead must be exploded; or, if lethal distance is not achieved a safety device has to operate so that the missile cannot damage friendly personnel or equipment.

Missile guidance systems can be conveniently divided into two classes each of which has its own special peculiarities. The first covers all missiles which move against surface targets – such as the broad categories of surface-to-surface and air-to-surface missiles – where the target is essentially stationary and its po0sition on the surface of the Earth can be observed or calculated. The second class encompasses those missiles which are designed to attack moving targets mainly surface-to-air missiles and air-to-air missiles. These two broad categories cover most missiles but there are, of course, borderline cases; for example, air-to-sea and underwater-to-air missiles, which do not fit quite so readily into the general pattern.

The three stages of guidance operate somewhat differently in each class. For weapons which are directed against airborne targets, the first stage following launching often consists of a radar gathering beam having a wide conical form which can bring the missile to the correct flight path as already mentioned. During midcourse guidance the missile can use what is known as beam rider or a system of command guidance, while the final closing to the kill will make use of some king of homing device.

For surface-to-surface missiles, the launching phase will once more be used to place the missile on its correct initial flight path or trajectory. Midcourse guidance in this class has to extend over a much longer range and will make use of an inertial or navigational system. While target homing might include to device explode the thermonuclear warhead at the optimum distance from the target area, which may not be at closest approach to the target.