RD-253

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The RD-253 (from Russian Ракетный двигатель , "Raketnyj dwigatel") ( GRAU index 11D48) is a rocket engine for liquid rockets .

Six RD-253 engines on the first stage of the Proton missile

Development and use

It was developed by the Soviet chief designer for rocket motors Valentin Petrovich Glushko between 1961 and 1965 at the Leningrad gas dynamics laboratory . Six of them are used in the Proton rocket to drive the first stage .

technology

It is operated with 1,1-dimethylhydrazine (UDMH) and liquid nitrogen tetroxide (N 2 O 4 ) and consists of an upstream and a main combustion chamber , a turbine and an auxiliary and two main pumps with a total output of 18.7 MW. The specialty of this engine is that the turbine for driving the fuel pumps is located inside the pre-combustion chamber. For this purpose, the entire amount of the oxidizer and a small part of the fuel is fed, which burns there at a low temperature and drives the turbine. The exhaust gas from the pre-combustion chamber then passes to the main combustion chamber, where the main part of the fuel is supplied and burns. With this design, the engine does not lose any drive gas for the pumps, even at the high combustion chamber pressure of almost 15 MPa, which would have led to considerable losses at a throughput of more than 520 kg / s. At the same time, the high degree of combustion due to the pre- combustion and main combustion largely excludes instabilities during combustion and thus combustion oscillations. Due to the special design of the RD-253, the dimensions and the mass of the engine could be kept low compared to a comparable engine, the design of which would have corresponded to that of the RD-107 .

Despite some problems with initial development and production, the RD-253 is still used in Proton launch vehicles today. Almost 2,000 of them have now been built. Some of them in improved versions such as the RD-275 (GRAU index 14D14) (after 1990) with 1578/1746 kN floor / vacuum thrust and 15.7 MPa combustion chamber pressure and the RD-275M (GRAU index 14D14M, sometimes also with RD -276 ) with a further 5% increase in take-off thrust, which had its first launch in July 2007 with a Proton-M.

Technical specifications

Code number value
Mixing ratio N 2 O 4 / UDMH 2.67
Combustion chambers 1
Total height 2.72 m
diameter 1.5 m
Dry matter 1280 kg
Mass / thrust ratio (ground / vacuum) 0.87 / 0.78 kg / kN
Combustion chamber diameter 430 mm
Combustion chamber pressure 14.7 MPa
Nozzle throat diameter 279.7 mm
Nozzle mouth diameter 1431 mm
Orifice pressure 61 kPa
Relaxation relationship 241
Floor thrust / vacuum thrust 1474/1635 kN
Specific impulse (soil / vacuum) 2795/3100 Ns / kg

literature

Web links

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