Beam-riding

Beam-riding, also known as Line-Of-Sight Beam Riding LOSBR or beam guidance, is a technique of directing a missile to its target by means of radar or a laser beam. The name refers to the way the missile flies down the guidance beam, which is aimed at the target. It is one of the simplest guidance systems and was widely used on early missile systems, however it had a number of disadvantages and is now found typically only in short-range roles.

Beam riding is based on a signal that is pointed towards the target. The signal does not have to be powerful, as it is not necessary to use it for tracking as well. The main use of this kind of system is to destroy airplanes or tanks. First, an aiming station (possibly mounted in a vehicle) in the launching area directs a narrow radar or laser beam at the enemy aircraft or tank. Then, the missile is launched and at some point after launch is “gathered” by the radar or laser beam when it flies into it. From this stage onwards, the missile attempts to keep itself inside the beam, while the aiming station keeps the beam pointing at the target. The missile, controlled by a computer inside it, “rides” the beam to the target.

Beam riding is one of the simplest methods of missile guidance using a radar. It was widely used for surface-to-air missiles in the post-World War II era for this reason.

Early tracking radars generally use a beam a few degrees wide, which makes it easy to find the target as it moves about. These radars are normally used in conjunction with wide-scanning early warning radar systems, although in modern systems the two functions can be combined. When a target is detected, some radars had the ability to "lock on", and track the target automatically.

Beam riding systems can be easily adapted to work with such a system. By placing receiver antennas on the rear of the missile, the onboard electronics can compare the strength of the signal from different points on the missile body and use this to create a control signal to steer it back into the center of the beam. In practice, the systems used additional information from the signal, such as conical scanning, to more accurately calculate the centerline. With this simple system, the majority of the tracking problem is offloaded from the missile to the launching platform. In early examples, these were ground-based radars with all the equipment necessary for tracking.

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Wikipedia