KTDU-426

KTDU-80

Soyuz TM-32 departing the ISS with its SKD nozzle cover closed
Country of origin	Russia
Manufacturer	KB KhIMMASH
Predecessor	KTDU-35
Status	In production
Liquid-fuel engine
Propellant	N2O4 / UDMH
Cycle	Pressure fed
Performance
Thrust	2.95 kN
Chamber pressure	0.88 MPa
Specific impulse	302 s
Burn time	890 s
Gimbal range	5
Dimensions
Length	1.2m
Diameter	2.1m
Used in
Soyuz

The KTDU-80 (Russian: Корректирующе-Тормозная Двигательная Установка, КТДУ) is the latest of a family of integrated propulsion system that KB KhIMMASH has implemented for the Soyuz since the Soyuz-T. It integrates main propulsion, RCS and attitude control in a single system pressure fed from a common dual string redundant pressurized propellant system. The common propellant is UDMH and N₂O₄ and the main propulsion unit, is the S5.80 main engine. It generates 2.95 kN (660 lbf) of thrust with a chamber pressure of 0.88 MPa (128 psi) and a nozzle expansion of 153.8 that enables it to achieve a specific impulse of 302 s (2.96 km/s). It is rated for 30 starts with a total firing time of 890 seconds. The integrated system without the pressurization nor tanks weighs 310 kg (680 lb) and is an integrated unit that is 1.2 m (47 in) long with a diameter of 2.1 m (83 in).

The KTDU-80 system integrates a dual string redundant propellant and pressurization system, a main propulsion system (the SKD), an RCS (the DPO-B) and an attitude control system (the DPO-M). All the propulsion elements are pressure fed rocket engines burning UDMH and N₂O₄ with a common supply of pressurized propellant. Mechanically, the KTDU-80 is separated in two sections:

Each subsystem is describe in the following sections.

The Pneumatic Pressurization System has three main functions:

The system has four spherical pressurizing gas tanks in two separated circuits. Each circuit connects two tanks, and has its individual pressure transducer, valves, pressure regulator and electrically actuated valves. The circuits are separated by two squib actuated valves that enable to share both circuits, to use a single one, or to use both systems independently. The Helium is stored initially at 34.32 MPa (4,978 psi) and is regulated to 1.75 MPa (254 psi), with a maximum pressure of 2.15 MPa (312 psi) and a minimum of 1.37 MPa (199 psi), which is the minimum required pressure to activate the pneumatically actuated valves of the SKD.