SA-2 “GUIDELINE”

Designated the V-750 (sometimes V-75) Dvina in the Soviet Union, the missile is better known in the West as the S-75 or by its NATO name, SA-2 “Guideline” Mod 0. Evolved from the 1944 German Wasserfall missile concept, the weapon was designed to protect the strategic and population centers of Russia, but it soon became the primary and longest-serving air defense missile offered to the Soviet Union’s allies too. Several variants were developed, including the short-lived experimental V-753 that was to be fired from an eight-round magazine aboard Sverdlov Class cruisers. Developed quickly in the mid-1950s, the missile was designed to intercept targets at medium to high altitude. Its performance against aircraft below 3,000ft was poor.

The two-stage SA-2 had a Kartukov PRD-18 booster section with 14 tubes of NMF-2 solid chemical propellant (more in later versions) and large fins to impart

stable flight on launch. This burned for four to five seconds and then fell away, leaving the Isayev S2.711 sustainer motor to maintain flight at Mach 3. The latter burned hypergolic liquid propellant comprising TG-02 (50 per cent isomeric xylidine, 48.5 per cent triethylamine and 1.5 per cent diethylamine), with AK-20 fuming nitric acid as the oxidizer. This specification was derived from the Wasserfall.

A turbo-pump was required to supply the motor with OT-155 Isonite (isopropyl nitrate) liquid fuel sufficient for a 22-second engine burn. The later Item 20D Volkhov development of the S-75 used a different fuel comprising 56 per cent kerosene and 40 per cent Trikresol, with a TG-02 “starter fuel” supply to ignite the mixture. This was much safer to handle and store than the volatile mix used in the Dvina or Desna (“Guideline Mod 1”) models. For the North Vietnamese, a shortage of technicians qualified to perform these tasks meant that fewer than 40 missiles could be assembled and filled with fuel, oxidizer and compressed air daily.