Beam riding
Encyclopedia
Beam-riding, also known as 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.
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.
s 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.
The inherent disadvantage of the radar beam riding system is that the beam spreads as it travels outward from the broadcaster. As the missile flies towards the target, it therefore becomes increasingly inaccurate. This is not a problem at short ranges, but as many early surface-to-air missile
s were designed to work at long ranges, this was a major issue. For example, earlier versions of the RIM-2 Terrier
missile introduced in the 1950s were beam riders, but later variants employed semi-active radar homing
to improve their effectiveness against high-performance and low-flying targets. In contrast to beam riding, semi-active guidance becomes more accurate as the missile approaches the target.
Another issue is the guidance path of the missile is essentially a straight line to the target. This is useful for missiles with a great speed advantage over their target, or where flight times are short, but for long-range engagements against high-performance targets the missile will need to "lead" the target in order to arrive with enough energy to do terminal manoeuvres. A possible solution for this problem was to use two radars, one for tracking the target and another for guiding the missile, but this drove up implementation costs. A more common solution for long-range missiles was to guide the missile entirely independently of the radar, using command guidance, as was the case for the Nike Hercules. Pure radar beam riding was rare by 1960.
s. A laser beam can be made much more narrow than a radar beam while not increasing the size of the broadcaster. Additionally, it is simple to encode additional information in the beam using digital means, which has a number of advantages. Missiles with small optical receivers on their tail can beam ride on lasers with similar ease as earlier radar beam systems, but will be inherently more accurate.
Additionally, as the beam is very narrow by design, less power is needed than a semi-active design where the volume of space being "painted" is generally larger, in order to ensure the missile body does not block all of the signal. This makes it more difficult to be noticed by the target's warning receiver. Very low power signals can be used.
In modern use, laser beam riding is generally limited to short-range missiles, both anti-air and anti-tank. Examples include the Starstreak, the RBS 70
, and 9M119 Svir.
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
to its target by means of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
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.
Basic concept
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
Aiming station
An aiming station is a term used to describe something used to designate targets for other systems, usually missiles. An example is a tank using a laser or radar to target enemy units for missiles....
(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.
Radar beam riding
Beam riding is one of the simplest methods of missile guidance using a radar. It was widely used for surface-to-air missileSurface-to-air missile
A surface-to-air missile or ground-to-air missile is a missile designed to be launched from the ground to destroy aircraft or other missiles...
s in the post-World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
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
Early warning radar
An early warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate...
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
Conical scanning
Conical scanning is a system used in early radar units to improve their accuracy, as well as making it easier to steer the antenna properly to point at a target...
, 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.
The inherent disadvantage of the radar beam riding system is that the beam spreads as it travels outward from the broadcaster. As the missile flies towards the target, it therefore becomes increasingly inaccurate. This is not a problem at short ranges, but as many early surface-to-air missile
Surface-to-air missile
A surface-to-air missile or ground-to-air missile is a missile designed to be launched from the ground to destroy aircraft or other missiles...
s were designed to work at long ranges, this was a major issue. For example, earlier versions of the RIM-2 Terrier
RIM-2 Terrier
The Convair RIM-2 Terrier was a two-stage medium-range naval surface-to-air missile , and was among the earliest surface-to-air missiles to equip United States Navy ships. Originally, the Terrier had a launch thrust of 23 kN , and weight of 1392 kg...
missile introduced in the 1950s were beam riders, but later variants employed semi-active radar homing
Semi-active radar homing
Semi-active radar homing, or SARH, is a common type of missile guidance system, perhaps the most common type for longer-range air-to-air and surface-to-air missile systems. The name refers to the fact that the missile itself is only a passive detector of a radar signal – provided by an external ...
to improve their effectiveness against high-performance and low-flying targets. In contrast to beam riding, semi-active guidance becomes more accurate as the missile approaches the target.
Another issue is the guidance path of the missile is essentially a straight line to the target. This is useful for missiles with a great speed advantage over their target, or where flight times are short, but for long-range engagements against high-performance targets the missile will need to "lead" the target in order to arrive with enough energy to do terminal manoeuvres. A possible solution for this problem was to use two radars, one for tracking the target and another for guiding the missile, but this drove up implementation costs. A more common solution for long-range missiles was to guide the missile entirely independently of the radar, using command guidance, as was the case for the Nike Hercules. Pure radar beam riding was rare by 1960.
Laser beam riding
Beam riding guidance became more popular again in the 1980s and 90s with the introduction of low-cost and highly portable laser designatorLaser designator
A laser designator is a laser light source which is used to designate a target. Laser designators provide targeting for laser guided bombs, missiles, or precision artillery munitions, such as the Paveway series of bombs, Lockheed-Martin's Hellfire, or the Copperhead round, respectively.When a...
s. A laser beam can be made much more narrow than a radar beam while not increasing the size of the broadcaster. Additionally, it is simple to encode additional information in the beam using digital means, which has a number of advantages. Missiles with small optical receivers on their tail can beam ride on lasers with similar ease as earlier radar beam systems, but will be inherently more accurate.
Additionally, as the beam is very narrow by design, less power is needed than a semi-active design where the volume of space being "painted" is generally larger, in order to ensure the missile body does not block all of the signal. This makes it more difficult to be noticed by the target's warning receiver. Very low power signals can be used.
In modern use, laser beam riding is generally limited to short-range missiles, both anti-air and anti-tank. Examples include the Starstreak, the RBS 70
RBS 70
RBS 70 is a man-portable air-defense system designed for anti-aircraft warfare in all climate zones and with little to no support from other forces. Originally designed and manufactured by the Swedish defence firm of Bofors Defence...
, and 9M119 Svir.
External links
- Jerzy Maryniak et al., "Modeling of Motion of an Automatically Controlled Beam-Riding Guided Missile in Terms of the Maggi Equations" (pdf), AIAA Atmospheric Flight Mechanics Conference and Exhibit, August 2005
- Missile Guidance, aerospaceweb.org, accessed March 14, 2007
- Greg Goebel, "Early Radar Technology", February 1, 2007, accessed March 14, 2007
- Carlo Kopp, "Man Portable Surface-Air Missiles", Australian Aviation, July, 1989
- Carlo Kopp, "Active and SemiActive Radar Missile Guidance", Australian Aviation, June 1982