SA-9 Gaskin
Encyclopedia
The warhead was primarily intended to impact the target directly, and had contact and magnetic fuzes, but also contained a back-up optical proximity fuze to detonate the warhead in case of a near miss. The missile also had an unusual safety mechanism in case of a miss; rather than a self-destruct fuze, if the optical fuze didn't detect a target within 13...16 seconds, the warhead safety mechanism would be engaged to prevent its detonation upon impact.
Propulsion is by a single-stage solid fuel
rocket
motor, which is ignited at a distance of few meters from the launch tube: as the throw-out charge ejects the missile from its canister, it is trailing a wire from its rear. The main rocket ignites when missile reaches the wire's end at a few metres distance, and is cut off from it.
The seeker head is an unusual construction, using uncooled lead sulphide (PbS) detector elements, but with an unusual tracking mechanism. Uncooled PbS elements are commonly used to detect radiation at only short wavelengths of less than 2 micrometers. Only very hot objects emit strongly at such short wavelengths, limiting heat-seeking systems using uncooled PbS detector elements to rear-hemisphere engagements against jet targets, although propeller-driven aircraft and helicopters can of course be engaged from any direction from which the exhaust or other very hot parts of the engine are visible.
The seeker head of 9M31, however, utilizes the PbS elements differently from usual. Taking advantage of the fact that the clear sky gives strong and constant background emission at below 2 micrometer range, peaking at visual light (0.4 to 0.7 micrometer) wavelengths at which PbS in 295 kelvins temperature still provides a response, the seeker head is used to track a change of radiation from the target compared to the background. The method is called optical photocontrast homing (Rus.: фотоконтрастное наведение). The advantage of photocontrast homing method over traditional heat-seeking homing heads using PbS elements is that it negates the most serious drawback of early-generation IR-homing missiles: complete lack of front-aspect engagement capability against approaching jets. Even early cooled seeker heads had usually only limited forward hemisphere engagement abilities, often reducing to zero in case of jets approaching exactly towards the shooter.
The new photo-contrast seeker had its own serious limits also, however, which came in the form of rather strict meteorological conditions that had to be met in order to enable the seeker to detect and track the target: it could only engage targets against background conditions of either clear sky or solid overcast, minimum of 20 degrees away from the sun, and at least 2 degrees above horizon. Nonetheless, following a study of battlefield conditions and aircraft tactics in past conflicts where short-range air defences had been used, it was concluded that conditions allowing the use of such homing system were common enough to make it a cost-effective design choice and a better trade-off than the only practical alternative available at the time, which was infrared homing restricted to rear-hemisphere engagements.
No doubt the fact that Strela-1 would be supplemented by IR-homing Strela-2 and radar-controlled ZSU-23-4 self-propelled AA gun system may have influenced the decision in favour of such an unusual homing system. The main advantage the choice was that it made Strela-1 the only ADA system in the Soviet tank or motor rifle regiment that could engage approaching targets out to a range of several kilometers - the ZSU being hampered by very short range, and Strela-2 by its limitation to tail-chase engagements of ground attack jets, after the jet had already delivered its attack.
The new version introduced many slight improvements in performance characteristics of the missile: it had a slightly heavier warhead, more accurate guidance system to increase the probability of direct impacts, and extended range. Range is again reported to be as high as 8000 m (0.35 to 5 miles) in a number of western and also a few Russian sources, whereas for example Petukhov & Shestov, Lappi, and a number Russian web sources give much more modest performance figures; considering the performance of similar systems, at least an intercept range of 8000 m seems unlikely for such a small, high-drag missile design.
Shilkas, and a SAM platoon with four Strela-1 vehicles.
The Strela-1 platoon contains, in addition to a command vehicle, one TEL
fitted with a passive radar
detection system similar to a Radar Warning Receiver
, and several more (usually three) without any radar system. The radar detection system is the 9S16 "Flat Box" and consists of four sensors mounted around the BRDM
vehicle giving it 360 degree coverage. This system emits no radar energy but can detect radio waves
emitted from aircraft, giving the vehicle warning about incoming aircraft and aiding in the acquisition of the target aircraft with the optical system. Typical tactics call for the launch of two missiles against each target to improve the chance of destroying it.
In Russia
, the 9K31 Strela-1 system was superseded by the 9K35 Strela-10.
Propulsion is by a single-stage solid fuel
Solid fuel
Solid fuel refers to various types of solid material that are used as fuel to produce energy and provide heating, usually released through combustion....
rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
motor, which is ignited at a distance of few meters from the launch tube: as the throw-out charge ejects the missile from its canister, it is trailing a wire from its rear. The main rocket ignites when missile reaches the wire's end at a few metres distance, and is cut off from it.
The seeker head is an unusual construction, using uncooled lead sulphide (PbS) detector elements, but with an unusual tracking mechanism. Uncooled PbS elements are commonly used to detect radiation at only short wavelengths of less than 2 micrometers. Only very hot objects emit strongly at such short wavelengths, limiting heat-seeking systems using uncooled PbS detector elements to rear-hemisphere engagements against jet targets, although propeller-driven aircraft and helicopters can of course be engaged from any direction from which the exhaust or other very hot parts of the engine are visible.
The seeker head of 9M31, however, utilizes the PbS elements differently from usual. Taking advantage of the fact that the clear sky gives strong and constant background emission at below 2 micrometer range, peaking at visual light (0.4 to 0.7 micrometer) wavelengths at which PbS in 295 kelvins temperature still provides a response, the seeker head is used to track a change of radiation from the target compared to the background. The method is called optical photocontrast homing (Rus.: фотоконтрастное наведение). The advantage of photocontrast homing method over traditional heat-seeking homing heads using PbS elements is that it negates the most serious drawback of early-generation IR-homing missiles: complete lack of front-aspect engagement capability against approaching jets. Even early cooled seeker heads had usually only limited forward hemisphere engagement abilities, often reducing to zero in case of jets approaching exactly towards the shooter.
The new photo-contrast seeker had its own serious limits also, however, which came in the form of rather strict meteorological conditions that had to be met in order to enable the seeker to detect and track the target: it could only engage targets against background conditions of either clear sky or solid overcast, minimum of 20 degrees away from the sun, and at least 2 degrees above horizon. Nonetheless, following a study of battlefield conditions and aircraft tactics in past conflicts where short-range air defences had been used, it was concluded that conditions allowing the use of such homing system were common enough to make it a cost-effective design choice and a better trade-off than the only practical alternative available at the time, which was infrared homing restricted to rear-hemisphere engagements.
No doubt the fact that Strela-1 would be supplemented by IR-homing Strela-2 and radar-controlled ZSU-23-4 self-propelled AA gun system may have influenced the decision in favour of such an unusual homing system. The main advantage the choice was that it made Strela-1 the only ADA system in the Soviet tank or motor rifle regiment that could engage approaching targets out to a range of several kilometers - the ZSU being hampered by very short range, and Strela-2 by its limitation to tail-chase engagements of ground attack jets, after the jet had already delivered its attack.
9M31M
While the 9M31 was accepted to service after state trials in 1968, the trials committee also suggested improvements that should be incorporated into the weapon as soon as possible. As a result of these improvements the 9M31M "Strela-1M" (US DoD designation SA-9B "Gaskin-Mod0") entered service in 1970.The new version introduced many slight improvements in performance characteristics of the missile: it had a slightly heavier warhead, more accurate guidance system to increase the probability of direct impacts, and extended range. Range is again reported to be as high as 8000 m (0.35 to 5 miles) in a number of western and also a few Russian sources, whereas for example Petukhov & Shestov, Lappi, and a number Russian web sources give much more modest performance figures; considering the performance of similar systems, at least an intercept range of 8000 m seems unlikely for such a small, high-drag missile design.
Deployment
The Strela-1 was deployed in short-range air defence batteries of Soviet motor rifle and tank regiments. The battery consisted of a gun platoon of four ZSU-23-4ZSU-23-4
The ZSU-23-4 "Shilka" is a lightly armored, self-propelled, radar guided anti-aircraft weapon system . ZSU stands for Zenitnaya Samokhodnaya Ustanovka , meaning "anti-aircraft self-propelled mount". The "23" signifies the bore diameter in millimeters. The "4" signifies the number of gun barrels. It...
Shilkas, and a SAM platoon with four Strela-1 vehicles.
The Strela-1 platoon contains, in addition to a command vehicle, one TEL
TEL
- Acronyms :TEL is a three-letter acronym for:* Tetra-ethyl lead, a gasoline additive to make leaded gasoline* Tokyo Electron, a semiconductor equipment manufacturer* Transporter erector launcher, a mobile missile launch platform...
fitted with a passive 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...
detection system similar to a Radar Warning Receiver
Radar warning receiver
Radar warning receiver systems detect the radio emissions of radar systems. Their primary purpose is to issue a warning when a radar signal that might be a threat is detected. The warning can then be used, manually or automatically, to evade the detected threat...
, and several more (usually three) without any radar system. The radar detection system is the 9S16 "Flat Box" and consists of four sensors mounted around the BRDM
BRDM
BRDM is an initialism for Boyevaya Razvedyvatelnaya Dozornaya Mashina, , literally "Combat Reconnaissance Patrol Vehicle". The BRDM is a four wheeled amphibious vehicle which is very lightly armoured by today's standards. Both versions were produced in the Soviet Union and other Eastern Bloc...
vehicle giving it 360 degree coverage. This system emits no radar energy but can detect radio waves
Radio waves
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...
emitted from aircraft, giving the vehicle warning about incoming aircraft and aiding in the acquisition of the target aircraft with the optical system. Typical tactics call for the launch of two missiles against each target to improve the chance of destroying it.
In Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, the 9K31 Strela-1 system was superseded by the 9K35 Strela-10.