Soyuz Feature Article
August 19, 2009 14:54:34
The Legendary Soyuz Booster
By Robert Gass
The Soyuz Booster Family. From left to right we see the R-7, Sputnik, Vostok, Voskhod, and Soyuz. Photo Credit: NASA

When talking about the Russian space program, invariably, people will begin to compare the American Space Shuttle to Russia's Soyuz booster. Many are quick to point out how advanced the Shuttle is, how much more powerful it is, and of course the fact that it can be used time and time again. But Soyuz  has more than a few tricks of it's own and it can honestly be debated that  this venerable, nearly 50 year old relic of the cold war, can still out class and out perform nearly every other booster on the market today.

Soyuz is the worlds oldest and most reliable space launcher. With the exception of some new upper stages it is virtually identical to the  R-7, Russia's first ICBM which was built in 1957 by the legendary Soviet rocket designed S.P. Korolev. Ironically, what would become the worlds most reliable space launcher was canceled before it was ever borne after six unsuccessful launch attempts. Korolev, who knew his design was sound, ignored the order to return to Moscow and launched his seventh, and last R-7, without the Kremlin's blessings. The flight was a complete success and both the R-7 and Korolev were redeemed.

The R-7 was intended to toss atomic weapons across the ocean and into the United States. The problem was that the Soviets had yet to develop atomic weapons small enough to be carried in a plane let alone in a rocket. Because nobody knew how large these weapons would be Korolev over designed the R-7 giving it tremendous lift capabilities far beyond those of other rockets in existence at that time.  

Korolev's R-7

Although Korolev was ordered to build an ICBM for the Soviet Government he knew that his rocket would open the door to space for the Soviet people. So he designed the R-7 in such a way that it could be easily converted into a space launcher. He then used that rocket to drag the Soviet Union kicking and screaming into space.

Once converted to a space launcher, the Soviets began  naming different configurations of the booster after the spacecraft it launched. So the R-7 was also called Sputnik, Vostok, Voskhod, Luna, Manolya and a host of other names before becoming the launch vehicle for the Soyuz manned spacecraft in the mid 1960s. Since that time the name has remained unchanged.

All in all Soyuz has been launched over 1736 times carrying everything from people to interplanetary probes. Soyuz can and has been  launched through heavy fog, relatively high winds, very cold temperatures, and even through snow storms! It boasts a failure rate of only 0.982% and at the peak of production nearly 60 were manufactured and launched every year. 

Cut-away diagram of  a Soyuz Booster. At the base we can see the four pods that make up the first stage clustered around the core that makes up the second stage. Above that is the third stage and a Fregat upper stage is seen inside the payload fairing. Photo Credit: Arianespace

Launches occur from one of two pads at the Baikonur Cosmodrome, or from one of four pads at the Plesetsk Cosmodrome. Plesetsk was originally a super secret military launch facility used by the Soviet Union to launch spy satellites and other military spacecraft. Baikonur, although also considered a State secret by the Soviets,  was primarily used for the more public manned and interplanetary missions. Today, both facilities are now open for civilian and commercial launches although Baikonur continues to be the base for all manned operations.

Soyuz is unique in that it is a "pod" rocket. Pod rockets differ from traditional rockets in that Instead of having the first stage stacked on top of the second, the first stage is wrapped around the second. On Soyuz four such "pods" are combined to form the first stage. They look like a cone that has been flattened on one side and attached to a cylindrical base.

 Each pod is identical containing an oxygen tank in the upper cone shaped section and a kerosene tank in the lower cylindrical section.  A single Energomash RD 107 engine and two gimbaled vernier thrusters are located at the base of each pod.

The RD 107 engine is unique in that it is in fact four engines in one. At the time of its development scientists working on the R-7 ICBM found that they could not produce a combustion chamber that was large enough to power the vehicle without producing vibrations that were so severe they would consistently destroy the vehicle. 

The problem was solved  by mounting a single large turbo pump above four smaller combustion chambers. These, in turn, fed into four nozzles creating four small engines as opposed to one large combustion chamber that fed into one large engine. The result is that  each pod has four engines giving the combined first stage a total of 16 engines. The engines are fixed and can not be gimbaled the way most modern rocket engines can which is why Soyuz  relies on a series of 12 vernier thrusters (small rockets that can be gimbaled) for its steering capabilities.

The second stage consists of the core rocket and it is powered by a single NPO Energomash RD 108 engine. This engine also has the distinctive four chamber design in effect adding four more engines to the stack  for a total of 20 (36 if you count the 12 verniers!). However, the core differs from the pods in that it is cylindrical in shape and contains four vernier thrusters instead of the two found on each pod. This allows the rocket to maintain three access stabilization once the pods have fallen away.

Above the second stage is a metal lattice that contains an  equipment bay that shelters the vehicles internal control systems.  The lattice also links the third stage to the second stage. The Third stage is powered by an RD 0110 engine from KB KhA.  This engine is more conventional in nature and does not contain the multiple chambers found in the first and second stage engines. Above that sits the payload and on manned flights a launch escape tower tops off the stack. All stages are fueled by liquid oxygen and kerosene.  

Another major difference between Soyuz and most other launchers is the way it is assembled. Soyuz is assembled on its side in a facility known as the Assembly and Testing Facility located close to the launch pad. Two days before launch, the rocket is rolled out of the assembly building and transported via rail car to the launch pad. 

This photo shows a manned Soyuz U booster on the launch pad at Baikonure. The giant tear drop shaped flame pit is in the forground. At the far end of the photo is the launch pad itself. The erector that was used to raise the booster into launch possition is still attached to the rocket. Support equipment can be seen ready top encapsulate the rocket. Photo Credit: SP Korolev Rocket And Space Corporation.

The launch pad itself  lies on the flat side of a gigantic tear drop shaped flame pit. The pit is graded so that the deepest part of the pit lies at the flat end which then gradually ascends to ground level at the pointed end. The launch pad sits directly over the deepest part of the pit and just below its rim. The pit is 45 meters deep and displaces 1 million meters of earth!

Upon reaching the pad, the booster is tilted into it's launch position using hydraulic lifts and then encased by the service towers. That afternoon (or sometimes the next day)  a dress rehearsal for launch is conducted during which all electrical and mechanical equipment are activated and tested.

Soyuz was first developed as a ballistic missile, so when SP Korolov designed his giant rocket, he kept preparation time down to a minimum. Although 2 days is a snails to military planers, it is considered to be lightning fast for a space launcher (compare it to the American Space Shuttle which takes over a month to get ready!). 

On Launch day  the vehicle is loaded with propellant and the final countdown sequence is started about four hours before launch. If people are involved, the crew will arrive at the launch pad only 2 hours before launch. Launch preparations proceed with clock work precision as the highly trained and experienced launch team works through the pre-launch check list as they have literally thousands of times before. Technical issues and scrubs are virtually unheard of. 

This close-up of the base of a Soyuz Booster shows the rockets first and second stages. All 20 of these engines along with 12 vernier rockets will light at launch to lift the rocket off of it's launch pad. Photo Credit: NASA

At launch all 20 engines and all 12 vernier thrusters fire simultaneously to provide the nearly 500 metric tons of thrust necessary get the vehicle off the ground. When Soyuz reaches a predetermined speed (usually about 118 seconds into the flight) the pods fall away and the core continues firing until it is time for third stage ignition. At this point, the core will shut down and instead of falling away just before ignition as with most other rockets, the core remains attached until the ignition of the third stage literally blasts the two stages apart at the lattice.

The third stage will continue operating for about another 240 seconds until a predetermined velocity is reached. It will then shut down and separate itself from the payload. At this point a valve will open allowing the liquid oxygen tank to outgas. This, in turn, provides thrust that moves the spent stage safely away from the payload. It will then slowly sink back into Earth's atmosphere where it is destroyed.

Tracking and telemetry are provided by independent radar transponders found in the second and third stages of the vehicle. Since the boosters flight path takes it mostly over land during the first few minutes of launch, the health of the rocket is downloaded to ground stations located along the flight path and telemetry and tracking data are transmitted to mission control where it is recorded for analysis.

After the fall of the Soviet Union in the mid 1980's, the entire Soyuz launch system was privatized and is now owned and operated by Starsem SA. Starsem is  a French corporation  consisting of four partners - EADS (35%), SamaraSpaceCenter (25%), Rosaviakosmos (25%) and Arianespace (15%). As these numbers clearly indicate, Russian corporations control 50% of the new companies stock with the remaining 50% divided amongst two European partners. 

Starsem currently markets five versions of the booster. Soyuz U is the manned version. It is used exclusively in support of the Russian manned space program and the International Space Station. Back in the 1970's the Soviets modified the Soyuz spacecraft so that it can serve as a space freighter called Progress. The standard Soyuz U booster was modified to accommodate the new un-manned freighter and became known as Soyuz Cargo.  

Back in the day's of the Soviet Union, a fourth stage was developed and added to the basic Soyuz launch vehicle.  The new stage was named Ikar and the new launcher became known as Soyuz-Ikar. Soyuz-Ikar features an in flight restart capability where the stages main engine can be started, turned off, and restarted up to 50 times during a mission. It can be controlled  from the ground or, it can operate in autonomous mode allowing for the delivery of multiple satellite payloads to orbit. Soyuz-Ikar is capable of delivering payloads of up to 4,100 kg to a 450 km circular orbit inclined 51.8 deg. or payloads of up to 3,300 kg to a 1,400 km circular orbit.

 Another fourth stage was developed for the Soviet planetary exploration program. This one is known as Fregat  and the launcher is known as Soyuz-Fregat. Fregat is more powerful than Ikar and has been used on over 30 interplanetary spaceflights. It has demonstrated a high degree of reliability under conditions that often exceeded its technical specifications. Frigat makes use of a fuel knowen as UDMH and uses N204 as an oxidizer. The single chamber engine can be restarted as many as 20 times making the vehicle well suited for multipul satellite launches, interplanetary flights, and delivering large payloads to orbit. Soyuz-Fregat can launch up to 5000 kg into orbits inclined 51.8 deg or up to 4,000 kg into 1,400 km circular orbits.

A Soyuz ST booster is raised onto the launch pad. Photo Credit: ESA

Finally, we come to the newest Soyuz booster - Soyuz ST. Soyuz ST features redesigned combustion chamber injectors on the first and second stages and a reinforced  third stage. The propellant tanks on the third stage also have been enlarged and a new digital flight control system added.  The payload fairing has been enlarged based on the one that was used used by the Ariane 4 boosters however, the Soyuz faring, is about 1 meter longer than the largest Ariane 4 faring.

The new booster is compatible with both the Ikar and Fregat upper stages giving Soyuz ST the ability to place payloads up to 5,500 kg into 450 km circular orbits or 4,600 kg to a 1,400 km Sun-synchronous orbit.

Arianespace intends to launch the Soyuz ST booster from its spaceport in French Guiana. The legendarySoviet booster will now join Europe' s launcher fleet bridging the gap between the light weight "Vega" and the heavy weight "Ariane V boosters. Construction of the facility began in January 2008 with the first launch scheduled for late 2009. This will mark the first launch of a Soyuz booster from a facility outside of the former USSR.

When Korolev first built the R-7 critics lambasted the rocket saying it was to big, took to long to prepare, and was a poor weapon. They were correct - the R-7 was a poor weapon but little did they realize that the "master designer" had in fact constructed an ideal space launcher that would still be in use long after most of those critics had died.

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 Soyuz Launch Vehicle Characteristics 


First Stage



RD-107 (4)



Thrust (tons)

102 (each)

Burn Time (sec)


Specific Impulse


Length (meters)




Dry Mass (tons)


Propellant Mass (tons)


Second Stage






Thrust (tons)


Burn Time (sec)


Specific Impulse


Length (meters)


Diameter (meters)


Dry Mass (tons)


Propellant mass (tons)


Third Stage






Thrust (tons)


Burn Time (sec)


Specific Impulse


Length (meters)


Diameter (meters)


Dry Mass (tons)


Propellant mass (tons)


Payload Mass (tons)


Shroud Mass (tons)


Launch Mass (tons)





Soyuz Launcher Countdown Timeline

(Manned Launch)

T-34 Hours

Booster is prepared for fuel loading


Batteries are installed in the booster


State commission gives go to take launch vehicle


Crew arrives at site 254


Tanking begins


Spacesuite donning


Booster is loaded with liquid oxygen


Crew meets delegations


Reports to state commissions


Transfer to the launch pad


Vehicle 1st and 2nd stage oxidizer fueling complete


Crew arrives at launch pad


Crew ingress through orbital module side hatch


Crew in reentry vehicle


Reentry vehicle hardware tested: suits are ventilated


Launch command monitoring and supply unit prepared


Orbital component hatch tested for sealing


Launch vehicle control system prepared for use: gyro instruments activated


Launch pad service structure halves are lowered


Reentry vehicle hardware testing complete: leak checks performed on suits


Emergency escape system armed: launch command supply unit activated


Service towers withdrawn


Suit leak tests complete: crew engages personal escape hardware auto mode


Launch gyro instruments uncaged: crew activates on-board recorders


All prelaunch operations complete


Key to launch command given at launch site


Automatic program of final launch operations is activated


All launch complex and vehicle systems ready for launch


Onboard systems switched to onboard control


Ground measurement system activated by RUN 1 command


Commanders controls activated


Crew switches to suit air by closing helmets


Launch key inserted in launch bunker


Combustion chambers of side and central engine pods purged with nitrogen


Booster propellant tank pressurization starts


Onboard measurement system activated by RUN 2 command


Prelaunch pressurization of all tanks with nitrogen begins


Oxidizer and fuel drain and safety valves of launch vehicle are closed


Ground filling of oxidizer and nitrogen to the launch vehicle is terminated


Vehicle on internal power


Automatic sequencer on


First umbilical tower separates from booster


Ground power supply umbilical to third stage is disconnected


Launch command given at the launch position


Central and side pod engines are turned on


Second umbilical tower separates from booster


Engine turbopumps at flight speed


First stage engines at maximum thrust


Fueling tower separates




Booster velocity is 1640 ft/sec


Stage one separation


Booster velocity is 4921 ft/sec


Escape tower and launch shroud jettison


Core booster separates at 105.65 statute miles


Third stage ignites


Velocity is 19,685 ft/sec


Third stage cut-off


Soyuz spacecraft separation


Soyuz spacecraft antennas and solar panels deploy


Flight control switches to Kaliningrad Mission Control


Begin Mission Time Line


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