The Operation of a Soyuz-2 Rocket By William Fescemyer

This document describes the function of the engine systems of a Russian Soyuz-2 carrier rocket, the latest three stage design in the Soyuz rocket family. This document will discuss the major system associated with the flight of this rocket, the propulsion systems of the vehicle.

The Soyuz-2 is a Russian designed rocket ship, designed to deliver a varying group of payloads, everything from satellites to astronauts, to a low Earth orbit. The Soyuz rocket flight system involves the usage of a non- recoverable three stage system, made up of engines using a varying mixture of liquid and solid rocket fuels, with each stage using a different type of engine.

Introduction: The Soyuz-2 spacecraft is one of the latest designs produced by the Russian Federal Space Agency. The Soyuz-2 is designed to be an effective, reliable, and cost effective replacement for its predecessor, the Soyuz-1. As can be seen in the figure, the Soyuz-2 is a very classic

Figure 1: Soyuz-2 on Launchpad rocket design. It is designed in a similar manner to its predecessor, with a three stage system, and nearly identical body design. This is due to a multitude of factors, primarily because of the Soyuz-1 reliability and cost effectiveness as a space transport system, mostly because of its simple engine systems. The main weakness of the Soyuz-1 was its inability to change course in flight, meaning that it had to be aimed on the Launchpad. The vehicle could only be launched when there was no wind. Also, the Soyuz-2 was produced to allow an increase payload weight, so that heavier objects or vehicles with larger crews could be sent to space. This required a redesign of engine systems, making this the primary difference in the new Soyuz spacecraft.

Spacecraft Design: The Soyuz spacecraft is designed around a three stage rocket design, with a payload carrying device mounted at the top of the spacecraft. Each of the rocket’s stages is designed to be used at a certain point during flight. The stage will expend its fuel then detach, falling back to Earth. The detachment of the stage clears the way for the next stage to fire. The extra weight of the previous stage is lost, and the rocket will gain fuel efficiency as it loses weight. Also, at higher atmospheres, air resistance lessens, due a reduction in density, and so less force is required to keep the vehicle moving upward. This means that later stages of the rocket can use smaller engines and burn less fuel. A three stage rocket is the most common form of non-recoverable rocket, as it provides three different engines, which can cover the three most important sections of a space vehicle’s journey. Each of the stages can be seen in figure 2, showing how the final rocket design fits together. The first part of the journey is the acceleration and troposphere flight, covered by larger engines of stage 1 on the Soyuz spacecraft, with additional thrust from stage 2 during the acceleration phase. The second part of the journey is through the stratosphere covered by stage 2. The final part of the journey is covered by stage 3, when the rocket ship enters the mesosphere and thermosphere. Finally, thrusters on the payload move the object to its final orbit distance of anywhere from 160 to 2000 kilometers from Earth, or low Earth orbit. As each of the stages fulfills its role, it can be detached to make way for a more efficient engine. Figure 2: Stage Setup for Soyuz-2 with Reentry Vehicle as Payload This design makes the vehicle more reliable. If a stage should fail, the mission can be canceled. The stages will detach, and the crew section can disengage to parachute back to Earth, unlike other spacecraft such as the space shuttle. The stages are easier to examine and maintain, because the rocket is simple to disassemble and inspect for issues. This makes prelaunch checks and maintenance more straightforward.

The engines and heat resistant panels are the primary locations of failure in rocket vehicles. The heat panels in the vehicle can be easily checked, as only the payload system must maintain heat resistant panels, and as can be seen in the figure, is a very small part of the vehicle. The rest of the stages, when detached, either burn up in the atmosphere or parachute back to Earth, meaning they do not require the easily damaged heat resistant ceramic panels. As compared to the space shuttle, with massive numbers of heat resistant panels, the Soyuz-2 maintains a much lower number of panels. The engines use older technologies in a new manner, and so have a small amount of electronics, reducing computer failure. They also use proven valve and fuel injection systems. The engine’s fuel sources are also said to be very straightforward and common, so they have been well tested. These engines systems are built off of older Soyuz engines, and so have been heavily tested. These engine factors make the Soyuz-2 reliable to the degree that it has only suffered 1 failed launch in its history, a great record for any spacecraft.

Stage 1: Design Operation: The first stage of the vehicle is designed primarily to launch the rocket, and direct its early stage flight. This stage is used to accelerate this vessel to a launch velocity of 7.8 kilometers per second. In order to do so, the stage utilizes its RD-0120.10 F engines, and liquid fuel systems. It is designed as the primary propulsion unit, and so is extremely specialized to do this job. The design operates usually through the usage of hydrogen, oxygen fuel cells to provide the necessary thrust. Engine System: To achieve this extremely high speed, the stage uses a Russian design engine called a RD-0120.10 F. As can be seen in figure 1, the stages sections maintain four nozzle systems, each an individual rocket motor, a self-contained engine in itself. This engine is built around the concept of providing the highest amount of thrust possible, without injuring the human occupants or damaging the payload. To do Figure 3: Stage One, surrounding Stage 2 so, the engine uses an advanced fuel injector system, which insures the proper amounts of the fuel is mixed then directed out of the nozzle. The engines are also designed to be able to reduce or increase thrust. This imbalance allows the vessel to turn. Each of the individual engines can have its flow of fuel reduced, and this reduction cause the rocket to turn toward the engine with the flow reduced. The engine can increase its burn again, and level out. It is reliable, as it operates under simple parameters, unlikely to fail. Fuel: The engine uses a mixed liquid fuel cell. Liquid fuel can be expended at a high enough rate to produce the necessary thrust. Though the actual composition of the fuel is kept secret by the Russian Federal Space Agency, it is believed to be two parts hydrogen and one part oxygen, as this is the typical fuel source used by the first stages on rockets. The fuel functions by the principle of applying energy to the separated fuels as it leaves its storage, causing the hydrogen and oxygen to react explosively to create water, with the energy released by the reaction propelling the vessel forward. This fuel provides a powerful enough force to accelerate the rocket, and can be easily controlled by limiting the amount of two reactants. Special Features: Of the stages of the Soyuz-2, this stage’s four rocket boosters are the only recoverable part of the spacecraft’s engine’s systems. Once the engines fuel supplies are depleted, they are detached from the rocket by the automatic disengagement of the attaching latches, then explode outward from compressed air boosters mounted along the stage. Then four parachutes deploy to allow them to fall safely to the ground.

Stage 2: Design Operation: The second stage of the vehicle is designed as the cruising stage, keeping the rocket on its current trajectory, as well as maintaining the vehicle current speed. To do this, the rocket uses a NK-33-1 engine, using very similar principles to the engine powering stage 1. The purpose of the stage is to maintain the rocket’s current speed, and carry it through the thinner air of the stratosphere. As such, it must carry a large amount of fuel for continuous burning, but does not have to accelerate. The stage is built to be much longer and thinner, to store the fuel, and only maintains a single engine cluster at the base. This allows the stage to operate as a go- between stage, from the lower atmosphere, to the higher atmosphere. Engine Systems: The NK-33-1 is a liquid fuel booster engine, and according to sources within the Russian Space Administration, the engine is very similar in operation to the RD-0120.10 F. This engine’s primary difference is in the fuel injection systems, which operate under the principle of providing enough fuel to keep the engine pushing the rocket upward, without causing major acceleration. Acceleration will be saved for the third stage, where the atmosphere is thin. The fuel injectors on the rocket are controlled by the launch control on the ground, as the amount of fuel entering the rocket needs to be fine-tuned during flight. Fuel: The engine most likely uses the same fuel as stage 1. This fuel is also useful for stage 2 engines, as it is relatively lightweight when compared with other possible fuel sources. The thrust from the fuel can very easily be fine-tuned in flight, by adjusting the hydrogen to oxygen ratio. If the amount of each is reduced according to the two to one ratio, then the thrust can be adjusted quickly and efficiently. Special Features: The stage includes an advanced mechanism to ensure that it does not successfully fall back to Earth. As the stage must burn up in the atmosphere, but also must not be damaged by the heat of launch, it is made of somewhat heat resistant metals. To ensure it burns up completely the stage includes a detonation mechanism that destroys the stage. This system makes much smaller parts, and these parts maintain more surface area, and so burn up more quickly. This ensures that the debris does not make it to the ground, and cause injuries.

Stage 3: Design Operation: The third stage is designed to carry the rocket up through the mesosphere, and thermosphere, and accelerate the rocket fast enough to escape Earth’s gravity. The rocket must move at 11.2 kilometers per second or gravity will pull the rocket in an elliptical direction to slowly arc back toward Earth. This stage must cover the longest distance, and also must accelerate. This means the stages engine is designed to provide large amounts of thrust as well as maintaining that thrust for a long period of time. To do so, the engine uses a slow burn fuel system. As can be seen in figure 4, it is also the smallest of the stages. Engine Systems: The engine for the final stage of the rocket is an RD-0146E, a type of solid fuel engine system, designed to complete the rocket’s journey into space. This engine is designed to burn slowly but in a powerful enough manner to accelerating the rocket forward against the pull of gravity. In the mesosphere and above, the air is very thin, so the rocket only has to compete against gravity. This means the engine itself is not required to be as Figure 4: Stage three, with payload (White Section) powerful as the first two stages. As such, the engine utilizes a slow burn system which applies an extremely combustible fuel in a slow manner. Most Russian rockets use this method, because it is reliable and efficient within the flight. The slow burn can be modified from outside the flight, allowing the system to operate at peak efficiency. Fuel: The RD-0146E fuel is not classified, as the fuel itself is purchased from outside Russia. The fuel utilized in the engine consists of potassium sulfate, combining with a chlorohydrocarbon, which reacts in a similar manner to the fuel in the other two stages. These chemicals combine only in the presence of an electric current, meaning the amount of fuel passing through the current can be modified, to control thrust. The fuel is also lighter than the other stages, as the first two stages need to carry the weight of the third stage. The reason the other stages do not use this fuel is its production is much more expensive than the hydrolysis of water, to produce the other stages fuel. Special Features: Stage 3 is the last stage on the rocket, and in certain missions, it is used to move the payload into low earth orbit, when the payload needs to move to a higher level of the orbital band. This means there is the risk of the stage remaining in orbit, creating unneeded space. To prevent this, the stage maintains extra thrusters that will destabilize the orbit, so the stage will fall back to Earth and burn up in the atmosphere.

Final Operation of the Spacecraft: When the Soyuz-2 vehicle functions correctly, the system should operate as follows. At the start of launch, the engine of stage 1 ignites, and the docking clamps release. Then the engine throttles up, beginning the launch by pushing the spacecraft upwards. The engine then begins to accelerate its passengers, pushing them at about 10 g-forces, and reaching a speed of 7.8 meters per second, as in figure 5. In 311 seconds (5 minutes), the engine is depleted, and the rocket has passed about six thousand feet above the troposphere. During the flight, the spacecraft conducts any necessary course corrections through the usage of the stages thrusters. Stage 1 then detaches, and the air boosters on stage 1 propel it away from the spacecraft. This stage’s parachutes open, after it reaches an altitude Figure 5: Soyuz-2 just after launch of a half mile. Immediately after stage 1 detachments, the stage 2 engines activate, and maintain the current speed. Ground control regulates fuel flow. In 359 seconds (6 minutes), the stage 2 boosters are also depleted, and the spacecraft has left the stratosphere. This stage detaches as well, and then begins to fall to Earth. The stage then destroys itself at a safe distance from the spacecraft, ensuring no debris reaches ground. As soon as stage 2 is clear, the engines of stage 3 activate. The engine then accelerates the craft to Earth gravity’s escape velocity of 11.2 Kilometers per second, and carries the rocket through the mesosphere, and thermosphere. The stage burns for 327 seconds (5.5 minutes). The stage then detaches from the payload. The payload now moves through space on its own smaller thrusters. Stage 3 fires thrusters to destabilize the stages orbit, ensuring that the depleted stage will fall back to Earth. The payload is now in low Earth orbit, and the launch has been a success. In total the launch lasted 997 seconds, or about 16 minutes, and has burned several thousand gallons of fuel. After the launch, the mission in space then commences.

Image Credits Figure 1: Soyuz-2. (n.d.). . Retrieved July 29, 2014, from http://upload.wikimedia.org/wikipedia/commons/7/73/Soyuz_2_metop.jpg Figure 2: How should Russia evolve the Soyuz rocket family?. (2013, May 1). . Retrieved July 29, 2014, from http://forum.nasaspaceflight.com/index.php?topic=31790.15 Figure 3: Soyuz Stage 3. (n.d.). . Retrieved July 29, 2014, from http://www.russianspaceweb.com/images/rockets/soyuz/stage3/cluster_1.jpg Figure 4: Soyuz Stage 2 engine. (n.d.). . Retrieved July 29, 2014, from http://www.kosmonavtika.com/lanceurs/fregat/tech/fregat/figC4a.jpg Figure 5: Soyuz Launch. (2014, January 14). . Retrieved July 29, 2014, from http://www.spaceflight101.com/uploads/6/4/0/6/6406961/1792520_orig.jpg?0