The Kh-55 (, also known as RKV-500; NATO reporting name: AS-15 'Kent') is a Soviet/Russian subsonic air-launched cruise missile, designed by MKB Raduga. It has a range of up to and can carry nuclear warheads. Kh-55 is launched exclusively from bomber aircraft and has spawned a number of conventionally armed variants mainly for tactical use, such as the Kh-65SE and Kh-SD, but only the Kh-101 and Kh-555 appear to have made it into service. Contrary to popular belief, the Kh-55 was not the basis of the submarine- and ground-launched S-10 Granat or RK-55 "Relief" (SS-N-21 'Sampson' and SSC-X-4 'Slingshot') designed by NPO Novator. The RK-55 is very similar to the air-launched Kh-55 (AS-15 'Kent') but the Kh-55 has a drop-down turbofan engine and was designed by MKB Raduga. Both have formed the basis of post-Cold-War missiles, in particular the Sizzler which has a supersonic approach phase.