The 2K12 "Kub" (; English: 'cube') (NATO reporting name: SA-6 "Gainful") mobile surface-to-air missile system is a Soviet low to medium-level air defence system designed to protect ground forces from air attack. 2К12 is the GRAU designation of the system. Each 2K12 battery consists of a number of similar tracked vehicles, one of which carries the 1S91 (SURN vehicle, NATO designation "Straight Flush") 25 kW G/H band radar (with a range of ) equipped with a continuous wave illuminator, in addition to an optical sight. The battery usually also includes four triple-missile transporter erector launchers (TELs), and four trucks, each carrying three spare missiles and a crane. The TEL is based on a GM-578 chassis, while the 1S91 radar vehicle is based on a GM-568 chassis, all developed and produced by MMZ. Development The development of the 2K12 was started after 18 July 1958 at the request of the CPSU Central Committee. The system was set the requirements of being able to engage aerial targets flying at speeds of at altitudes of at ranges up to , with a single shot kill probability of at least 0.7. The systems design was the responsibility of the now Tikhomirov Scientific Research Institute of Instrument Design (NIIP). In addition to NIIP several other design bureaus were involved in the creation of the Kub missile system including Mytishchi Machine-Building Plant which designed and produced the chassis of the self-propelled components. Many of the design bureaus would later go on to co-operate in the development of the successor to the 2K12 "Kub", the 9K37 "Buk". First trials of the missile system were started at the end of 1959 to discover a series of problems: low power for the missile radar seeker and badly designed nose cone missile air inlets design failure low quality of heat shield inside the afterburner chamber (titanium was replaced by steel). In August 1961 Toropov was replaced by Lyapin as the Chief Designer of Vympel and in January 1962 Tikhomirov was replaced by Figurovskiy as the Chief Designer of NIIP. Still, the work was not intensified. Before 1963 only 11 of 83 missiles fired had the seeker head installed; only 3 launches were successful. Kub downed its first-ever air target on February 18, 1963, during the state trials at Donguz test site, Orenburg Oblast. It was an Ilyushin Il-28 bomber. The system entered an extended testing period between 1959 and 1966,