Fregat

Fregat stage with the spherical tanks, here in the configuration for Fobos-Grunt

Fregat ( Russian Фрегат for frigate ) is a rocket upper stage , the Russian company Lavochkin built and currently in Soyuz - launchers used. The stage is used for launching soaring satellites such as geostationary communications satellites and spacecraft . Fregat can be re-ignited up to 20 times and is therefore also suitable for launching multiple satellites in different orbits .

development

The Fregat stage was derived from the drive module of the Fobos and Mars-96 space probes. Development of the stage began in 1993, but progressed very slowly due to funding difficulties. It was not until the establishment of the Starsem company to market the Soyuz rocket and the signing of the contract to launch four cluster satellites for ESA that the development of the Fregat stage accelerated at the end of the 1990s.

The first launch of a Fregat upper stage on a Soyuz rocket (the Soyuz-U version) took place on February 8, 2000. After another test flight, four cluster satellites were successfully launched into space on two Soyuz U / Fregat flights. Fregat was able to prove her efficiency and reliability when she took over control of the flight in good time after the third stage of the Soyuz was switched off too early and was able to save the mission with her excess fuel.

Currently, the Soyuz (in the versions Soyuz-U, Soyuz-FG, Soyuz-2.1a and Soyuz-2.1b) with the Fregat stage is used to launch commercial payloads and space probes ( Mars Express , Venus Express ). The start orders are processed by the Starsem company.

Since 2011, Soyuz rockets equipped with Fregat stages have been launched from the European spaceport in Kourou , where they are marketed via Arianespace .

The Fobos-Grunt mission also started in 2011, in which , with the help of a modified Fregat stage, a probe was to land on the Mars moon Phobos for the first time and bring soil samples back to Earth.

technology

The Fregat upper stage is an autonomous rocket stage that is equipped with a modern digital control system and has its own communication and navigation systems. This means that the stage can theoretically be integrated into various types of medium to heavy launch vehicles. The step is 1.50 m high with a diameter of 3.35 m. The curb weight is 950 kg and up to 5,250 kg of rocket fuel ( NTO / UDMH ) can be carried.

The structure of the stage consists of six spherical aluminum tanks arranged in a circle. Two of these tanks contain the fuel (UDMH), two the oxidizing agent (NTO), and two more are used as containers for the avionics . Eight support structures that run through the tanks provide structural stability.

The main engine of the stage is an S5.92 engine manufactured by KB Chimmasch near Moscow with a combustion chamber , which can change its position and thus the thrust vector of the stage through a hydraulic control system. 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 s).

For the position control has Fregat in addition to the control possibilities of the S5.92 12 additional hydrazine burning 50-N-engines, which are arranged in four groups and are fed from two separate smaller tanks with fuel. Up to 85 kg of hydrazine can be taken from the step.

The enlarged Fregat SB stage ( Russian Фрегат-СБ ) has additional fuel tanks that can be released. This step is 2.3 m high with a diameter of 3.44 m and weighs up to 11,600 kg together with fuel. The empty weight of the stage is 950 kg, the empty weight of the drop tanks is 375 kg. Fregat-SB is to be used on heavier launch vehicles - initially, use on the Zenit is planned. The first launch took place on January 20, 2011. The Fregat-SB was launched on a zenith and transported the Russian electric L- weather satellite into a geostationary orbit.

Start list

→ See: List of rocket launches with Fregat upper stage

Web links

• Soyuz GSC User's Manual from Arianespace (PDF file, English language; 5.3 MB)
• Website of the manufacturer Lavochkin on the Fregat stage ( Memento from April 3, 2015 in the Internet Archive ) (Russian)

Individual evidence

1. ^ Gunter Krebs: Fregat. In: Gunter's Space Page. August 23, 2014, accessed September 1, 2014 .