Fregat (Russian Фрегат for frigate ) is a rocket upper stage, which is being built by Russia's Lavochkin and currently used in Soyuz rockets. The stage is used to launch high altitude satellites, such as geosynchronous communications satellites, and space probes. Fregat up to 20 times may be re- ignited, and is thus useful in different orbits and for exposing a plurality of satellites.


The Fregat stage was derived from the propulsion module of the Fobos - and Mars -96 spacecraft. The development of the stage began in 1993, but was due to financing difficulties progressing very slowly. Only with the establishment of the company Starsem to commercialize the Soyuz rocket and the signing of the Treaty for the launch of four Cluster satellites for ESA accelerated in the late 1990s the development of the Fregat stage.

The first launch of a Fregat upper stage of a Soyuz rocket (version Soyuz -U) was held on 8 February 2000. After another test flight four Cluster satellites were successfully launched into space at two Sojus-U/Fregat-Flügen. This Fregat was able to prove their efficiency and reliability, when she took over in time for a premature shutdown of the third stage of the Soyuz control of the flight and the mission still was able to save by their excess fuel charge.

Currently, the Soyuz (versions Soyuz -U, Soyuz -FG and Soyuz - 2.1a as of 2006, and the Soyuz - 2.1b ) with the Fregat stage to launch commercial payloads and spacecraft (Mars Express, Venus Express) will be used. The start jobs are handled by the company Starsem.

Since 2011, start by default with Fregat stage equipped Soyuz rocket from the European Spaceport in Kourou, here takes place marketing on Arianespace.

Also in 2011 launched the Fobos -Grunt mission in which using a modified Fregat stage for the first time to land a probe on Mars Moon Phobos and should bring back soil samples to Earth.


The Fregat upper stage is an autonomous rocket stage which is equipped with a modern digital control system and has independent communication and navigation systems. Thus the stage is theoretically integrated into different types of moderate to severe launchers. The stage is 1.50 m high with a diameter of 3.35 m. The empty weight is 950 kg, and it can store up to 5250 kg fuel (NTO / UDMH ) are taken.

The step structure is composed of six spherical aluminum tanks, which are arranged in a circle. Two of the tanks containing the fuel ( UDMH ), two said oxidizing agent (NTO ) and two further serve as a container for the avionics. Eight support structures that pass through the tanks are used for structural stability.

The stage main engine is a product manufactured by KB ChemMachine near Moscow S5.92 engine which has a combustion chamber and can change by a hydraulic control system of its position, and thus the thrust vector of the step. The engine can be operated in two modes: with a thrust of 19,85 / 14 kN and a specific impulse of 3.247/3.100 Ns / kg (or 331/316 sec).

For position control Fregat has in addition to the control possibilities of S5.92 over 12 additional hydrazine combusted 50 -N thrusters are arranged in four groups and two separate smaller tanks fed with fuel. Up to 85 kg of hydrazine can be taken away from the stage.

The enlarged Fregat -SB- stage (Russian Фрегат - СБ ) has additional droppable fuel tanks. This level is 2.3 m high with a diameter of 3.44 m and weighs along with fuel up to 11,600 kg. The stage empty mass is 950 kg and the unladen mass of the droppable tanks 375 kg. Fregat -SB is to heavier launchers - the first visit is scheduled at the zenith - are used. The first launch took place on January 20, 2011. The Fregat -SB was launched on a Zenit and promoted the Russian electric -L weather satellite into geostationary orbit.

Start list

This is a partial list of all the Fregat launch. State of the list: June 26, 2013

  • ¹ Not necessarily the target orbit of the payload - but the path on which the payload was suspended from the upper stage.

For scheduled start of the Fregat stage see the list of scheduled Soyuz launches and the list of scheduled Zenit- offs.