Work on air-to-air missiles had started at the Kaliningrad Engineering Plant (then known as Plant #455, and later merged into Zvezda-Strela) in 1955. This had resulted in the
Kaliningrad K-5 (AA-1 'Alkali') family of beam-guided missiles, including the K-51 (RS-2-US) carried by the
Su-9 'Fishpot'.
OKB-4 Molniya (later
Vympel NPO) under
Matus Bisnovat would go on to produce missiles such as the
AA-6 Acrid. As a result, Yurii N. Korolyov came up with his own proposals based on the earlier experiments with the RS-2-US. A design bureau to develop the RS-2-US for surface targets was set up under Korolyov by decree #100 of 12 March 1966 of the Ministry of the Aircraft Industry; The resulting weapon used the body of a
K-8 (AA-3 'Anab'), K-5 guidance and propulsion systems, but increased the warhead from to . This had the big advantage of allowing the new weapon to be fitted to any aircraft capable of firing the K-5. It entered production in 1968 for that aircraft. The Kh-66 was only an interim solution as it required the launch aircraft to dive towards the target to maintain lock on the target. It entered service on 20 June 1968 A laser-guided version of the Kh-23, the Kh-25, became the basis for the AS-10 'Karen' family of missiles. Technology from these was 'backported' to the Kh-23 to create the Kh-23M in 1974. The Kh-23 was later licensed for local production in both Romania and Yugoslavia. In 1977 a dummy Kh-23 was fired from a Ka-252TB helicopter, the prototype of the
Kamov Ka-29TB 'Helix-B' assault transport. ==Design==