S5.80 Explained

S5.80
Country Of Origin:	USSR
Date:	1977-1986
First Date:	1986-05-21 (Soyuz TM-1)
Designer:	OKB-2, Anton Tavzarachvili
Purpose:	Spacecraft main propulsion
Predecessor:	11D426
Status:	In Production
Type:	liquid
Fuel:	UDMH
Oxidiser:	N2O4
Mixture Ratio:	1.85
Cycle:	pressure fed
Combustion Chamber:	1
Nozzle Ratio:	153.8
Thrust(Vac):	2.95kN
Chamber Pressure:	0.88MPa
Specific Impulse Vacuum:	302isp
Burn Time:	890 seconds
Restarts:	30
Gimbal:	±5°
Length:	1.2m (03.9feet)
Diameter:	2.1m (06.9feet)
Dry Weight:	310kg (680lb)
Used In:	Soyuz since Soyuz-TM and Progress since Progress-M

The S5.80 is a liquid pressure-fed rocket engine burning N₂O₄/UDMH with an O/F of 1.85. It is used for crew-rated spacecraft propulsion applications. It is currently used in the Soyuz-TMA-M spacecraft propulsion module KTDU-80, and its sibling, the S5.79 rocket engine, is still used as the main propulsion of the Zvezda ISS module.The S5.80 generates 2.95kN of thrust with a chamber pressure of 0.88MPa and a nozzle expansion of 153.8 that enables it to achieve a specific impulse of 302isp. It is rated for 30 starts with a total firing time of 890 seconds. The engine, without the pressurization system or propellant tanks, weighs 310kg (680lb) and is an integrated unit that is 1.2m (03.9feet) long with a diameter of 2.1m (06.9feet).

Versions

This engine has been used with certain variations in the crewed Russian space program since the Salyut 6 in Soviet times. The three main versions are:

• 11D426: Used as the main orbit correction engine of the Soyuz-T it was part of the integrated propulsion module KTDU-426 which was the big innovation introduced with that series. It enabled using fewer engines, increasing the reliability and reducing the weight of the spacecraft using a dual string redundant pressurization and propellant feed system for the main propulsion and the reaction control system. Since the latter could be used to de-orbit the spacecraft, it eliminated the need for backup orbital correction engine like the KTDU-35 required.
• S5.79 (AKA KRD-79): The orbit correction propulsion module of the second generation DOS stations, the Salyut-6 and Salyut-7 space stations, the Mir Core Module and the Zvezda ISS module. It was designed by KB KhIMMASH under RKK Energia specification based on the 11D426 design. It has improved life and restart capabilities, and is offered in a single compact unit. Each station has two of such engines.
• S5.80: An evolution of the 11D426 and S5.79 it is used on the KTDU-80 propulsion module that has been a staple of all Soyuz since the Soyuz-TM and Progress since the Progress-M. It has slightly reduced thrust but improved specific impulse, while improving engine life over the 11D426.

Engine (SKD)	11D426	S5.79	S5.80
Propulsion module		KRD-79	KTDU-80
Development	1968–1974	1968-1977	1977–1986
Engine Type
Module	integrated spacecraft propulsion, pressurization and attitude control system	main propulsion engine	integrated spacecraft propulsion, pressurization and attitude control system
Propellant	N2O4/UDMH with 1.85 O/F ratio
Thrust (SKD)	3.09kN	3.09kN	2.95kN
isp	292isp	293.7isp	302isp
Chamber Pressure	0.88MPa	1.75MPa	0.88MPa
Nozzle	1	1	1
Expansion Ratio			153.8
Burn time	570s	2700s	890s
Ignitions	40	70	30
Mass	270kg (600lb)	38.5kg (84.9lb)	310kg (680lb)
Length	1200mm	840mm	1204mm
Diameter	2100mm	550mm	2100mm
Uses			Soyuz-TM Soyuz-TM Soyuz-TMA Soyuz-TMA-M Progress-M Pirs Poisk
References

See also

• KB KhIMMASH
• KTDU-35
• KTDU-80
• Soyuz-T
• Soyuz-TM

External links

• KB KhIMMASH Official Page (in Russian)