The RD-253 and its later variants, the RD-275 and RD-275M, are liquid-propellant rocket engines developed in the Soviet Union by Energomash. The engines are used on the first stage of the Proton launch vehicle and use an oxidizer-rich staged combustion cycle to power the turbopumps. The engine burns a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide oxidizer, which are highly toxic, but storable at room temperature.
History
Development of the RD-253 started in 1961. Preliminary investigations and development of the engine and its further production was performed under the guidance of Valentin Glushko and finished in 1963. The RD-253 uses an oxidiser-rich staged combustion cycle. It was used for the first time in July 1965, when six engines powered the first stage of the Proton rocket. Development and production of RD-253 was a qualitative leap forward for rocketry of that time by achieving high levels of thrust, specific impulse and pressure in the combustion chamber. This engine is one of the most reliable engines in the USSR and modern Russia.
As the first stage of the Proton-K rocket used six RD-253 engines, the system played a pivotal role in Russian space missions when this rocket was chosen as a carrier, including the following programs: