The RD-0255 (Russian: Ракетный Двигатель-0255, romanized: Raketnyy Dvigatel-0255, lit.
Both are liquid-fuel rocket engines, burning a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide (N2O4) oxidizer.
The RD-0256 main engine operates in the oxidizer rich staged combustion cycle, while the vernier RD-0257 uses the simpler gas generator cycle.
Subsequently, it has been in the Dnepr second stage and as of 2016 it is still in active service.
[6] The RD-0228 was developed between 1967 and 1974 for the first generation of R-36M (GRAU: 15D83) ICBM second stage, but was replaced on subsequent iterations by the RD-0256.