The Kh-90 GELA (Russian: ГЭЛА (гиперзвуковой экспериментальный летательный аппарат), Hypersonic Experimental Flight Vehicle) is a Soviet/Russian air-to-surface hypersonic missile. It was supposed to replace subsonic intermediate range missiles in the Soviet inventory. The missile was an ambitious project, as the main objective was to develop it into a hypersonic missile. It was to be a successor to the Kh-45, which never entered service.

Kh-90 GELA (NATO reporting name: AS-X-21)
Type	Air-launched Hypersonic weapon
Place of origin	Russia
Production history
Manufacturer	MKB Raduga, Turaevo TMKB Soyuz, TsAGI
Specifications
Mass	15 metric tons[1]
Length	11 m [2][3]
Diameter	0.8 - 0.9m
Wingspan	7m
Warhead	various: HE, FAE, TBX, two nuclear each 1.2 Mt
Warhead weight	200 kg to < 1.6 ton HE , 200 kg < 1.82 ton TNW
Engine	booster + Ramjet Raduga TMKB Soyuz (or Scramjet ?) TsAGI
Propellant	solid propellant booster, liquid ramjet (or scramjet), kerosene
Operational range	3000-4000[4] km
Maximum speed	Mach 5+ [1]
Guidance system	inertial, TERCOM , GLONASS , Radar , IR IIR , TV camera , Opto-Electronic , CCD
Launch platform	Aircraft, can be loaded on ship ground TEL, maybe submarine

The missile was designed by Raduga. It was equipped with a one-megaton thermonuclear warhead and used inertial navigation with mid-course update via data link. It had a maximum range of 3,000 km.

It was developed at the beginning of 1980, following the Kh-80 and Kholod projects.^[5][6][7] It was shown to the public an MAKS Airshow 1995.^[1]