|Country of origin||USSR|
|Associated L/V||Soyuz, Zenit|
4 / UDMH
|Thrust (vac.)||19.61 kilonewtons (4,410 lbf)|
|Chamber pressure||9.61 megapascals (1,394 psi)|
|Isp (vac.)||327 seconds|
|Burn time||2,000 seconds|
|Length||1,028 millimetres (40.5 in)|
|Diameter||838 millimetres (33.0 in)(max)|
|Dry weight||75 kilograms (165 lb)|
|Fregat and Phobos program|
S5.92 burns a hypergolic mixture of UDMH and nitrogen tetroxide in the gas-generator cycle. It has two throttle settings. The highest produces 19.61 kilonewtons (4,410 lbf) of thrust, a specific impulse of 327 seconds, and a 3-second ignition transient. The lower throttle level produces 13.73 kilonewtons (3,090 lbf) of thrust, specific impulse of 316 seconds, and a 2.5 second ignition transient. It is rated for 50 ignitions, and 300 days between ignitions.
It was originally designed by the famous A.M. Isayev Chemical Engineering Design Bureau, for the two spacecraft of the Phobos program. While the Mars missions were unsuccessful, the spacecraft manufacturer, NPO Lavochkin, found a market niche for the technology. Thus, the engine was adapted for use on the optional Fregat upper stage of the Soyuz and Zenit launch vehicles.