RD-107

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View of the underside of a Soyuz FG with 4 RD-107s and one RD-108
RD-107

The RD-107 (from Russian Реактйвный двигатель , "Reaktiwny Dwigatel", in German: " reaction drive ") is a rocket engine for liquid rockets . It was developed by the Soviet chief designer for rocket motors Valentin Petrovich Gluschko between 1954 and 1957 at the Leningrad Gas Dynamics Laboratory and used in the R-7 variants such as the Soyuz rocket as a drive for the first stage . Initially, the single-chamber RD-105 and RD-106 engines were intended for this rocket, but these enlarged versions of the German ED-140 proved to be unstable, and work on it was discontinued in 1956.

The preferred thereon engine RD-107 / RD-108 with kerosene and liquid oxygen ( LOX operated) and has four rigid cylindrical combustors Paraboldüsen, two pivotable control nozzles and a turbo pump set at 4000 kW and two main and two auxiliary pumps. The main pumps deliver 91 kg of kerosene and 226 kg of oxygen per second to the combustion chambers at full thrust, with the turbine running at over 8,000 rpm. One of the auxiliary pumps conveys hydrogen peroxide as fuel for the turbine of the main pumps, the other conveys liquid nitrogen into the fuel tank and creates an overpressure there in this way.

Turbopump scheme

A derivative of the RD-107 is the RD-108 which is used as a second stage engine for the Soyuz and which has four control nozzles. In contrast to the predecessor engines RD-100 , RD-101 and RD-103 , the thermal load on the combustion chamber wall has been reduced considerably by cooling with fuel. For this purpose, the upper part of the combustion chambers was double-walled (provided with channels) through which the fuel was pumped. In addition to the cooling, this measure also increased the stability of the combustion chamber, which meant that the combustion chamber pressure could be more than doubled without damage.

The main problem during the development of the engine was (as with almost every large rocket engine) the combustion vibrations , which can lead to failure or destruction of the engine due to periodic changes in pressure and temperature in the combustion chamber. They are caused by incomplete combustion of fuel.

variants

The first engines for the variants of the R-7 bore the official designation 8D74 and 8D75 (the RD-x designation is that of the manufacturer). They were part of the initial equipment of the R-7 in 1957, but with 971 and 912 kN were still too weak to carry the planned payloads (warheads or the large Sputnik satellites from Sputnik -3). As a result, improved / modified variants were developed very quickly. For the RD-107 these are 8D74-1958 (e.g. for Luna version), 8D74-1959 (e.g. for Wostok), 8D74K (e.g. for Molnija), 8D76 (e.g. for 8A91 , i.e. from Sputnik 3), 8D727 and 11D511 (RD-117 for Soyuz) or for the RD-108 the versions 8D75PS (Sputnik 1 and 2), 8D77 (e.g. for 8A91, i.e. from Sputnik 3), 8D75 -1958 (Luna), 8D75-1959 (Wostok), 8D75K (e.g. for Molnija), 8D727 (e.g. Molnija) and 11D512 (RD-118 for Soyuz).

The engines are still today in a modified form as RD-107A / RD-117 (821/1021 kN floor / vacuum thrust) and RD-108A / RD-118 (765/1010 kN floor / vacuum thrust) in the various Soyuz versions used.

Technical specifications

Data for the RD-107 and RD-108.

Parameter RD-107 (8D76) RD-108 (8D77)
Mixing ratio oxygen / kerosene 2.47 2.39
Combustion chambers / control nozzles 4/2 4/4
Total height 3.00 m
Height without control thrusters 2.86 m
Diameter without timing gears 2.58 m 1.95 m
Dry matter 1155 kg 1250 kg
Mass / thrust ratio 1.2 kg / kN 1.3 kg / kN
Combustion chamber diameter 430 mm
Combustion chamber volume ~ 70 l
Combustion chamber pressure 5.85 MPa / 58.5 bar 5.10 MPa / 51.0 bar
Nozzle throat diameter 166 mm
Nozzle mouth diameter 720 mm
Orifice pressure 39 kPa / 0.39 bar 34 kPa / 0.34 bar
Relaxation relationship 150
Bottom shear / vacuum thrust 821/995 kN
(790/945 kN in R-7, Sputnik)
745/941 kN
Specific impulse (soil / vacuum) 2520/3080 Ns / kg
(2452 Ns / kg in R-7, Sputnik)
2430/3090 Ns / kg
Outflow velocity 2950 m / s

literature

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