Fregat is a type of rocket stage
Multistage rocket
A multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...

 developed by NPO Lavochkin in the 1990s. Its main engine is a liquid propellant rocket
Liquid rocket
A liquid-propellant rocket or a liquid rocket is a rocket engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be relatively low, and it is possible to use lightweight pumps to pump the propellant from...

 that uses UDMH and N2O4
Dinitrogen tetroxide
Dinitrogen tetroxide is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide; some call this mixture dinitrogen tetroxide, while some call it nitrogen dioxide.Dinitrogen tetroxide is a powerful oxidizer, making it highly...

 as propellants.


The dry mass of a Fregat (as of October 2006) is 924 kg; with fuel the mass is up to 5350 kg. Current modification of the main engine has a specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...

 of 332 s and a thrust of 2018 kg. The reaction control system
Reaction control system
A reaction control system is a subsystem of a spacecraft whose purpose is attitude control and steering by the use of thrusters. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow...

 includes 12 engines, each having 5 kg thrust, 225 s Isp, using pure hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

, with mass up to 42 kg. Height: 1,500 mm, Diameter 3,350 mm,
Fueled Mass: 6,415-6,535 kg., Firing Duration: 1350 seconds


The stage can be restarted multiple times, which has been used to place payloads such as the GIOVE
GIOVE, or Galileo In-Orbit Validation Element, is the name for each satellite in a series being built for the European Space Agency to test technology in orbit for the Galileo positioning system.Giove is the Italian word for "Jupiter"...

-B satellite into their planned orbits.


NPO Lavochkin created many interplanetary probes in the past, and the Fregat stage follows their design traditions. The main part of the stage is six intersecting spheres placed on a single plane, four of which contain propellants. The remaining two contain the control equipment. The main engine is placed between the spheres, so Fregat is a tightly-packed stage with a diameter much larger than its height.

Fregat is a versatile spacecraft. For example, in addition to orbital insertion, it can be used as an escape stage to launch modern space probes into interplanetary trajectories (e.g., Venus Express
Venus Express
Venus Express is the first Venus exploration mission of the European Space Agency. Launched in November 2005, it arrived at Venus in April 2006 and has been continuously sending back science data from its polar orbit around Venus. Equipped with seven science instruments, the main objective of the...

 and Mars Express
Mars Express
Mars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally referred to the speed and efficiency with which the spacecraft was...


Fregat stages are currently used as the fourth stage of some Soyuz-FG
The Soyuz-FG launch vehicle is an improved version of the Soyuz-U, from the R-7 family of rockets, designed and constructed by TsSKB-Progress in Samara...

 launch vehicles. A version called Fregat-SB can be used with the Ukrainian Zenit-2SB rocket. This version has a block of drop-off tanks which makes increased payload capability possible. Fregat-SB was launched for the first time on 20 January 2011, when it lifted the Elektro-L weather satellite into geosynchronous orbit.

External links

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