9K31 Strela-1

9K31 Strela-1 (NATO reporting name: SA-9 Gaskin)
9K31 transporter erector launcher
Type	Vehicle-mounted SAM system
Place of origin	Soviet Union
Service history
In service	1968-present
Used by	See list of operators
Wars	Arab-Israeli Wars, Western Sahara War, Yugoslav wars, South African Border War Lebanon wars, Iran-Iraq war, Gulf War, 2003 invasion of Iraq
Production history
Designer	OKB-16 design bureau (now the Moscow-based KB Tochmash Design Bureau of Precision Engineering)
Manufacturer	Soviet state factories
Produced	1966
Variants	9K31, CA-95
Specifications (9K31 Strela-1)
Weight	7,000 kg
Length	5.8 m
Width	2.4 m
Height	2.3 m (travelling)
Crew	3 (commander, gunner and driver)
Armour	5-14 mm
Main armament	4 x 9M31 (or 9M31M)
Engine	GAZ 41 V-8 water-cooled petrol 140 hp at 3,400 rpm
Power/weight	20 hp/t
Ground clearance	0.43 m
Fuel capacity	290 litres
Operational range	750 km
Speed	100 km/h (road) 10 km/h (water)
Guidance system	infrared homing

The 9K31 Strela-1 (Russian: 9К31 «Стрела-1»; English: arrow) is a highly mobile, short-range, low altitude infra-red guided surface-to-air missile system. Originally developed by the Soviet Union under the GRAU designation 9K31, it is commonly known by its NATO reporting name, SA-9 "". The system consists of a BRDM-2 amphibious vehicle, mounting two pairs of ready-to-fire 9M31 missiles.

The missiles used in this system were developed alongside the ubiquitous Soviet MANPADS 9K32M "Strela-2" (NATO designation SA-7 "Grail") in the 1960s. At first both missiles were intended to be man-portable systems, but as it became obvious that Strela-2 would be far the more compact of the two systems, the development goals of Strela-1 were changed. Instead of a battalion-level man-portable system the new criteria called for a regimental vehicle-mounted SAM to support the ZSU-23-4.

As a result of the change in role and more relaxed weight limits of a vehicle-mounted SAM, the design team made the 9M31 a much heavier missile, which permitted fewer design compromises than in the case of Strela-2 to achieve acceptable kinematic performance. The most notable difference is the much larger diameter of the missile and a blunt seeker head that occupies the full width of the missile body. With all else being equal, the ability of an optical seeker to detect a target is directly proportional to its diameter, but on the other hand aerodynamic drag increases proportionally to the square of the diameter.

The Strela-1 also had a warhead over twice as heavy, a proximity fuze and more effective control surface configuration to provide better maneuverability at the cost of increased drag. The net result was a missile four times the weight of Strela-2, with only slightly longer reach but otherwise of much better performance.

Each TEL carries four ready-to fire missiles, but typically no missiles for reloading. Reloading is performed manually and usually takes approximately 5 minutes. The missile boxes are lowered for transport to lower the total height of the vehicle. The driver and commander have periscopes for viewing outside the vehicle when the hatches are closed.