RD-253

RD-253 (РД-253)
Country of origin	USSR/Russia
First flight	RD-253: 1965; RD-275: 1995; RD-275М: 2007
Designer	Energomash, V.Glushko
Manufacturer	Proton-PM
Application	First stage booster
Associated LV	Proton
Successor	RD-254, RD-256, RD-275, RD-275М
Status	Operational
Liquid-fuel engine
Propellant	N2O4 / UDMH
Mixture ratio	2.67
Cycle	Staged combustion
Configuration
Chamber	1
Nozzle ratio	26.2
Performance
Thrust, vacuum	RD-253: 1,630 kN (370,000 lbf); RD-275: 1,750 kN (390,000 lbf); RD-275М: 1,832 kN (412,000 lbf)
Thrust, sea-level	RD-253: 1,470 kN (330,000 lbf); RD-275: 1,590 kN (360,000 lbf); RD-275М: 1,671 kN (376,000 lbf)
Thrust-to-weight ratio	156.2
Chamber pressure	RD-253: 14.7 MPa (2,130 psi; 147 bar); RD-275: 15.7 MPa (2,280 psi; 157 bar); RD-275M: 16.5 MPa (2,390 psi; 165 bar)
Specific impulse, vacuum	RD-253: 316s; RD-275: 316s; RD-275M: 315.8s
Specific impulse, sea-level	RD-253: 285s; RD-275: 287s; RD-275M: 288s
Gimbal range	7.5°, single plane
Dimensions
Length	3 m (9.8 ft)
Diameter	1.5 m (4 ft 11 in)
Dry weight	RD-253: 1,080 kg (2,380 lb); RD-275: 1,070 kg (2,360 lb); RD-275M: 1,070 kg (2,360 lb)
Used in
	Proton first stage.
References
References

The RD-253 ( Russian: Раке́тный дви́гатель 253 , Rocket Engine 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 UDMH/N₂O₄, which are highly toxic but hypergolic and storable at room temperature, simplifying the engine's design.

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