11D428

The 11D428A-16 (manufacturer's name RDMT-135M) is a liquid pressure-fed rocket engine burning N2O4/UDMH with an O/F of 1.85. It is used for crew-rated spacecraft propulsion applications. It is currently used in the KTDU-80 spacecraft propulsion module. The previous version, the 11D428A (manufacturer's name RDMT-135) is still used as the reaction control system thrusters of the Zvezda ISS module. The 11D428A-16 generates 129.16 N of thrust with a chamber pressure of 0.88 MPa and achieves a specific impulse of 291 isp. It is rated for 500,000 starts with a certified ignition time of 0.03 seconds to 2000 seconds. Each unit weights 1.5 kg.

Versions
This engine has been used with certain variations in the crewed Russian space program since the Salyut 6 in Soviet times. The three main versions are:
 * 11D428: Delivered in 1970 for use in Salyut 1.
 * 11D428M: Version developed for the Yantar-2K platform. It reached space on the first launch, Kosmos 697 on August 6, 1974.
 * 11D428A (AKA RDMT-135): Version developed for the Soyuz 7K-S, it flew on Kosmos 670, Kosmos 772 and Kosmos 869. Later used on the KTDU-426.
 * 11D428A-10: Thruster used on the Zvezda ISS Module. Originally developed for the Mir Core Module.
 * 11D428A-14: Thruster used on the Zvezda ISS module.
 * 11D428A-16 (AKA RDMT-135M): Improved specific impulse version. Used on the KTDU-80 since Soyuz TM-28.
 * 11D428AF-16:Thruster version developed for the Fobos-Grunt planetary sample mission.