S5.142

The S5.142 (AKA DST-25) 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 was used in KTDU-80 propulsion module from the Soyuz-TM to the Soyuz-TMA-M, as the low thrust thruster (DPO-M). As of the Soyuz MS, KTDU-80 does not use DPO-M anymore.

The S5.142 generates 25 N of thrust with a chamber pressure of 0.88 MPa and a nozzle expansion of 45 that enables it to achieve a specific impulse of 285 isp. It is rated for 300,000 starts with a total firing time of 25,000 seconds and can do single burns from 0.03 seconds to 4,000 seconds. Each unit weights 0.9 kg.

Versions
This engine has been used in crewed Russian space program since the Soyuz TM-23. There are two versions:
 * S5.142 (AKA DST-25): Version used as DPO-M (attitude control thrusters) on the KTDU-80 unit of the Soyuz-TM up to the Soyuz-TMA-M.
 * S5.142A: A version of the S5.142 adapted for the KVTK upper stage for the Angara rocket.