The S-13 is a 122 mm calibre unguided rocket weapon developed by the Soviet Air Force for use by military aircraft. It remains in service with the Russian Air Force and some other countries. The S-13 rocket was developed in the 1970s to meet requirements for a penetrating weapon capable of cratering runways and penetrating hardened aircraft shelters, bunkers and pillboxes, to fill a gap between 80 mm and 240 mm rockets and fulfill a role similar to the 127 mm Zuni rocket. The S-13 is conventional in layout, with a solid rocket motor and folding tail fins that provide stability after launch.