SA-2 Guideline

The SA-2 Guideline is the NATO reporting name for the S-75 (Russian: ?-75) high-altitude surface-to-air guided missile system (SAM) of the Soviet Union, the most widely deployed and used air defense missile in history. They gained notoriety when they shot down a USAF U-2 spy plane in 1960, and during the Vietnam War when they were briefly the cause of much consternation among US air-war planners. It has also been locally-produced in the People's Republic of China as the HQ-1 and HQ-2.

Description

The S-75 system is organized into a regimental structure with three battalions consisting of launcher sites, and the regimental headquarters with early-warning radars and communications. Each battalion consists of six semi-fixed trainable single-rail launchers for their V-750 missiles about 60-100 meters apart, deployed in a hexagonal "flower" pattern around the central radars and guidance systems. It was the unique shape of the "flower" that led to the sites being easily recognizable in reconnaissance photos. Typically another six missiles are stored on tractor-trailers near the center of the site.

Related Topics:
Radar - Tractor-trailer

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The V-750 is a two-stage missile, consisting of a solid-fuel booster and a storable liquid-fuel upper stage burning red fuming nitric acid as the oxidizer, and kerosene as the fuel. The booster fires for about 4-5 seconds, and the main engine for about 22 seconds, by which time the missile is travelling at about Mach 3. The booster mounts four large cropped-delta wing fins with small control surfaces in their trailing edges, used to control roll. The upper stage has smaller cropped-deltas near the middle of the airframe, with a smaller set of control surfaces are at the extreme rear and (in most models) much smaller fins on the nose.

Related Topics:
Two-stage - Red fuming nitric acid - Mach 3 - Delta wing

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The missiles are guided using radio control signals from the guidance computers at the site, sent on one of three channels. The earlier SA-2 models received their commands via two sets of four small antennas in front of the frontmost fins, while the D models and on used four much larger strip antennas running between the forward and middle fins. The guidance system at an SA-2 site can handle only one target at a time, but can direct three missiles against it. Additional missiles could be fired against the same target after one or more missiles of the first salvo had completed their run and the radio channel was freed.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The missile typically mounts a 195 kg (430 lb) fragmentation warhead, with proximity, contact and command fusing. The warhead has a lethal radius of about 65 m (215 ft) at lower altitudes, while at higher altitudes the thinner atmosphere allows for a wider radius of up to 250 m (820 ft). The missile itself is accurate to about 75m (250 ft), which explains why two were typically fired in a salvo. One version, the SA-2E, mounted a 295 kg (650 lb) nuclear warhead of an estimated 15 kT yield, or a conventional warhead of similar weight.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Typical range for the missile is about 45 km (30 miles), with a maximum altitude around 20,000 m (60,000 ft). The radar and guidance system imposed a fairly long short-range cutoff of about 500-1,000 m (3,000 ft), making them fairly safe to attack at low level.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The main search radar, known as the Spoon Rest in the west, has a range of about 275 km (170 miles), while the tracking/guidance radars, the Fan Song, have a range of about 65 km (40 miles). Earlier versions used a targeting radar known as Knife Rest, which was replaced in Soviet use, but can still be found in older installations. The Fan Song system consisted of two antennas operating on different frequencies, one for elevation and the other for azimuth. The regimental HQ also includes a Spoon Rest, as well as a Flat Face long-range C-band radar and the Side Net height-finder. Information from these radars is forwarded to the battalion Spoon Rest operators to allow them to coordinate their searches.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~