Multistage rocket: Ministry of Defense of the Russian Federation. Multistage rocket: Ministry of Defense of the Russian Federation What are multistage rockets?
In Fig. 22 shows that the trajectory of a ballistic missile, and therefore its flight range, depends on initial speed V 0 and the angle Θ 0 between this speed and the horizon. This angle is called the throwing angle.
Let, for example, the throwing angle be Θ 0 = 30°. In this case, the rocket, which began its ballistic flight at point 0 with a speed V 0 = 5 km/sec, will fly along elliptical curve II. At V 0 = 8 km/sec, the rocket will fly along elliptical curve III, at V 0 = 9 km/sec - along curve IV. When the speed is increased to 11.2 km/sec, the trajectory from a closed elliptical curve will turn into an open parabolic one and the rocket will leave the sphere of gravity of the earth (curve V). At an even higher speed, the rocket's departure will follow a hyperbola (VI). This is how the trajectory of the rocket changes when the initial speed changes, although the throwing angle remains unchanged.
If you keep the initial speed constant and only change the throwing angle, then the trajectory of the rocket will undergo no less significant changes.
Let, for example, the initial speed be V 0 = 8 km/h. If a rocket is launched vertically upward (throwing angle Θ 0 = 90°), then theoretically it will rise to a height equal to the radius of the Earth and return to Earth not far from the start ( VII) At Θ 0 = 30°, the rocket will fly along the elliptical trajectory we have already considered (curve III). Finally, at Θ 0 = 0° (launch parallel to the horizon), the rocket will turn into an Earth satellite with a circular orbit (curve I).
These examples show that only by changing the throwing angle the range of missiles at the same initial speed of 8 km/sec can have a range from zero to infinity.
At what angle will the missile begin its ballistic flight? This depends on the control program that is assigned to the rocket. You can, for example, for each initial speed choose the most advantageous (optimal) throwing angle, at which the flight range will be greatest. As the initial speed increases, this angle decreases. The resulting approximate values of range, altitude and flight time are shown in table. 4.
Table 4
If the throwing angle can be changed arbitrarily, then the change in initial speed is limited, and increasing it for every 1 km/sec is associated with major technical problems.
K. E. Tsiolkovsky gave a formula that allows one to determine the ideal * speed of a rocket at the end of its engine acceleration:
V start = V source ln G start /G end,
where Vid is the ideal speed of the rocket at the end of the active section;
V source is the speed of gas flow from the engine jet nozzle;
G initial - initial weight of the rocket;
G con - final weight of the rocket;
ln - sign of the natural logarithm.
We became acquainted with the speed of gas flow from a rocket engine nozzle in the previous section. For liquid fuels given in table. 3, these speeds are limited to 2200 - 2600 m/sec (or 2.2 - 2.6 km/sec), and for solid fuels - to 1.6 - 2.0 km/sec.
G start denotes the starting weight, i.e. total weight rocket before launch, and G con is its final weight at the end of acceleration (after fuel is consumed or the engines are turned off). The ratio of these weights G start / G end, included in the formula, is called the Tsiolkovsky number and indirectly characterizes the weight of the fuel consumed to accelerate the rocket. Obviously than larger number Tsiolkovsky, the greater the speed the rocket will develop and, therefore, the further it will fly (all other things being equal). However, the Tsiolkovsky number, as well as the speed of gas flow from the nozzle, has its limitations.
In Fig. Figure 23 shows a cross-section of a typical single-stage rocket and its weight diagram. In addition to fuel tanks, the rocket has engines, controls and control systems, casing, payload, and various structural elements, auxiliary equipment. Therefore, the final weight of the rocket cannot be many times less than its initial weight. For example, the German V-2 rocket weighed 3.9 tons without fuel, and 12.9 tons with fuel. This means the Tsiolkovsky number of this rocket was equal to: 12.9/3.9 = 3.31. At the current level of development of foreign rocket technology, this ratio for foreign rockets reaches a value of 5 - 7.
Let's calculate the ideal speed of a single-stage rocket, taking V 0 = 2.6 km/sec. and G start / G end = 7,
V ID = 2.6 · ln 7 = 2.6 · 1.946 ≈ 5 km/sec.
From the table 4 shows that such a missile is capable of reaching a range of about 3,200 km. However, its actual speed will be less than 5 km/sec. since the engine spends its energy not only to accelerate the rocket, but also to overcome air resistance, to overcome the force of gravity. The actual speed of the rocket will be only 75 - 80% of the ideal. Consequently, it will have an initial speed of about 4 km/sec and a range of no more than 1800 km *.
* (Range given in table. 4 is given approximately, since a number of factors were not taken into account when calculating it. For example, sections of the trajectory lying in dense layers of the atmosphere and the influence of the Earth’s rotation were not taken into account. When shooting at east direction range of flight ballistic missiles turns out to be greater, since the speed of rotation of the Earth itself is added to their speed relative to the Earth.)
To create an intercontinental ballistic missile, launch artificial satellites Earth and spaceships, and even more so to send space rockets to the Moon and planets, it is necessary to impart a significantly higher speed to the launch vehicle. Thus, for a missile with a range of 9000 - 13000 km, an initial speed of about 7 km/sec is required. The first escape velocity that must be imparted to a rocket so that it can become a satellite of the Earth with a low orbit altitude is, as is known, 8 km/sec.
To escape the Earth's sphere of gravity, the rocket must be accelerated to the second escape velocity- 11.2 km/sec; to fly around the Moon (without returning to Earth) a speed of more than 12 km/sec is required. A flyby of Mars without returning to Earth can be accomplished at an initial speed of about 14 km/sec, and with a return to orbit around the Earth - about 27 km/sec. A speed of 48 km/sec is required to reduce the duration of the flight to Mars and back to three months. Increasing the rocket's speed, in turn, requires spending an ever-increasing amount of fuel for acceleration.
Let, for example, we build a rocket that weighs 1 kg without fuel. If we want to give it a speed of 3, 6, 9 and 12 km/sec, then how much fuel will need to be filled into the rocket and burned during acceleration? The required amount of fuel * is shown in the table. 5.
* (At an exhaust speed of 3 km/sec.)
Table 5
There is no doubt that in the rocket body, the “dry” weight of which is only 1 kg, we will be able to accommodate 1.7 kg of fuel. But it is very doubtful that it can accommodate 6.4 kg of it. And, obviously, it is completely impossible to fill it with 19 or 54 kg of fuel. A simple but quite durable tank that can hold such an amount of fuel already weighs significantly more than a kilogram. For example, a twenty-liter canister known to motorists weighs about 3 kg. The “dry” weight of the rocket, in addition to the tank, must include the weight of the engines, structure, payload, etc.
Our great compatriot K. E. Tsiolkovsky found another (and so far the only) way to solve such a difficult problem as achieving the speeds required by a rocket in practice today. This path consists of creating multistage rockets.
A typical multistage rocket is shown in Fig. 24. It consists of a payload AND several detachable stages with power plant and a supply of fuel in each. The first stage engine imparts speed ν 1 to the payload, as well as the second and third stages (second subrocket). Once the fuel is used up, the first stage separates from the rest of the rocket and falls to the ground, and the rocket's second stage engine ignites. Under the influence of its thrust, the remaining part of the rocket (the third subrocket) acquires additional speed ν 2. Then the second stage, after using up its fuel, also separates from the rest of the rocket and falls to the ground. At this time, the third stage engine turns on and imparts an additional speed ν 3 to the payload.
Thus, in a multi-stage rocket, the payload is accelerated many times. The total ideal speed of a three-stage rocket will be equal to the sum of three ideal speeds, received from each stage:
V ID 3 = ν 1 + ν 2 + ν 3.
If the speed of gas flow from the engines of all stages is the same and after the separation of each of them the ratio of the initial weight of the remaining part of the rocket to the final weight does not change, then the speed increases ν 1, ν 2 and ν 3 will be equal to each other. Then we can assume that the speed of a rocket consisting of three (or even n) stages will be equal to triple (or increased by n times) the speed of a single-stage rocket.
In fact, each stage of multistage rockets may contain engines that produce different exhaust velocities; a constant ratio of weights may not be maintained; Air resistance changes as the flight speed changes and the Earth's gravity changes as you move away from it. Therefore the final speed multistage rocket cannot be determined by simply multiplying the speed of a single-stage rocket by the number of stages *. But it remains true that by increasing the number of stages, the speed of the rocket can be increased many times.
* (It should also be borne in mind that there may be a time interval between turning off one stage and turning on another, during which the rocket flies by inertia.)
In addition, a multistage rocket can provide a given flight range of the same payload with significantly less total consumption fuel and launch weight than a single-stage rocket. Has the human mind really managed to bypass the laws of nature? No. Simply, a person, having learned these laws, can save on fuel and the weight of the structure while completing the task. In a single-stage rocket, from the very start to the end of the active phase, we accelerate its entire “dry” weight. In a multistage rocket we don't do this. Thus, in a three-stage rocket, the second stage no longer wastes fuel to accelerate the “dry” weight of the first stage, because the latter is discarded. The third stage also does not waste fuel to accelerate the “dry” weight of the first and second stages. It accelerates only itself and the payload. The third (and generally the last) stage could no longer be disconnected from the head of the rocket, because further acceleration is not required. But in many cases it still separates. Thus, separation of the last stages is practiced in satellite launch vehicles, space rockets and such combat missiles as Atlas, Titan, Minuteman, Jupiter, Polaris, etc.
When scientific equipment placed in the head of a rocket is launched into space, the separation of the last stage is provided. This is necessary for the correct functioning of the equipment. When a satellite is launched, it is also planned to separate from the final stage. Thanks to this, resistance is reduced and it can exist for a long time. When launching a combat ballistic missile, the last stage is separated from the warhead, as a result of which it becomes more difficult to detect the warhead and hit it with an anti-missile. Moreover, the last stage that separates during the descent of the rocket becomes a false target. If, when returning to the atmosphere, it is planned to control the warhead or stabilize its flight, then without the last stage it is easier to control it, since it has less mass. Finally, if the last stage is not separated from the combat head, then it will be necessary to protect both from heating and combustion, which is unprofitable.
Of course, the task of obtaining high speeds movement will be decided not only by the creation of multi-stage rockets. This method also has its drawbacks. The fact is that with an increase in the number of stages, the design of rockets becomes much more complicated. There is a need for complex mechanisms for separating stages. Therefore, scientists will always strive for a minimum number of stages, and for this, first of all, it is necessary to learn how to obtain more and more high speeds the flow of combustion products or products of any other reaction.
2. Operating principle of a multi-stage rocket
The rocket is very “costly” vehicle. Spacecraft launch vehicles “transport” mainly the fuel necessary to operate their engines and their own structure, consisting mainly of fuel containers and a propulsion system. The payload accounts for only small part rocket launch mass.
A composite rocket allows for a more efficient use of resources due to the fact that during flight a stage that has exhausted its fuel is separated, and the rest of the rocket fuel is not wasted on accelerating the design of the spent stage, which has become unnecessary to continue the flight. An example of a calculation confirming these considerations is given in the article Tsiolkovsky Formula.
Missile configuration options. From left to right:
1. single-stage rocket;
2. two-stage rocket with transverse separation;
3. two-stage rocket with longitudinal separation.
4. A rocket with external fuel tanks that are separated after the fuel in them is exhausted.
Three-stage transversely separated Saturn V rocket without adapters
Structurally, multistage rockets are made with transverse or longitudinal separation of stages.
With transverse separation, the stages are placed one above the other and work sequentially one after another, turning on only after the separation of the previous stage. This scheme makes it possible to create systems, in principle, with any number of stages. Its disadvantage is that the resources of subsequent stages cannot be used during the operation of the previous one, being a passive load for it.
Three-stage launch vehicle with longitudinal-transverse separation Soyuz-2.
With longitudinal separation, the first stage consists of several identical rockets operating simultaneously and located symmetrically around the body of the second stage, so that the resultant thrust forces of the first stage engines are directed along the axis of symmetry of the second. This scheme allows the engine of the second stage to operate simultaneously with the engines of the first, thus increasing the total thrust, which is especially necessary during the operation of the first stage, when the mass of the rocket is maximum. But a rocket with longitudinal separation of stages can only be two-stage.
There is also a combined separation scheme - longitudinal-transverse, which allows you to combine the advantages of both schemes, in which the first stage is divided from the second longitudinally, and the separation of all subsequent stages occurs transversely. An example of this approach is the domestic carrier Soyuz.
Space Shuttle layout.
The first stage is side solid propellant boosters.
The second stage is an orbiter with a detachable external fuel tank. At start, the engines of both stages are started.
Launch of the Space Shuttle.
The unique design of a two-stage rocket with longitudinal separation has spaceship Space Shuttle, the first stage of which consists of two side solid fuel boosters, and on the second stage part of the fuel is contained in the orbiter tanks, and most of- in a detachable external fuel tank. First, the orbiter propulsion system consumes fuel from the external tank, and when it is depleted, the external tank is reset and the engines continue to operate on the fuel contained in the orbiter tanks. This scheme makes it possible to make maximum use of the orbiter’s propulsion system, which operates throughout the entire launch of the spacecraft into orbit.
When transversely separated, the stages are connected to each other by special sections - adapters - load-bearing structures of cylindrical or conical shape, each of which must withstand the total weight of all subsequent stages, multiplied by the maximum overload value experienced by the rocket in all flight segments in which this adapter is included. rockets.
With longitudinal separation, power bands are created on the body of the second stage, to which the blocks of the first stage are attached.
The elements connecting the parts of a composite rocket give it the rigidity of a solid body, and when the stages are separated, they should almost instantly release the upper stage. Typically, the steps are connected using pyrobolts. A pyrobolt is a fastening bolt, in the rod of which a cavity is created next to the head, filled with high explosive explosive with an electric detonator. When a current pulse is applied to the electric detonator, an explosion occurs, destroying the bolt rod, causing its head to come off. The amount of explosives in the pyrobolt is carefully dosed in order, on the one hand, to ensure that the head comes off, and, on the other, not to damage the rocket. When the stages are separated into electric detonators of all pyrobolts connecting the separated parts, a current pulse is simultaneously applied and the connection is released.
Next, the steps should be spaced a safe distance from each other. When separating stages in the atmosphere, the aerodynamic force of the oncoming air flow can be used to separate them, and when separating in the void, auxiliary small solid rocket engines are sometimes used.
On liquid rockets these same engines also serve to “sediment” the fuel in the tanks of the upper stage: when the engine of the lower stage is turned off, the rocket flies by inertia, in a state of free fall, while the liquid fuel in the tanks is in suspension, which can lead to failure starting the engine. Auxiliary engines The stages impart a slight acceleration, under the influence of which the fuel “settles” on the bottom of the tanks.
In the above photo of the Saturn 5 rocket, on the body of the third stage, the black body of one of the auxiliary solid fuel propulsion engines of the 3rd and 2nd stages is visible.
Increasing the number of steps gives positive effect only up to a certain limit. The more stages, the greater the total mass of adapters, as well as engines operating only on one part of the flight, and, at some point, a further increase in the number of stages becomes counterproductive. IN modern practice As a rule, rocket science of more than four stages is not done.
When choosing the number of stages, reliability issues are also important. Pyrobolts and auxiliary solid propellant rocket motors are single-use elements, the functioning of which cannot be checked before the rocket launch. Meanwhile, the failure of just one pyrobolt can lead to an emergency termination of the rocket’s flight. An increase in the number of disposable elements that are not subject to functional testing reduces the reliability of the entire rocket as a whole. This also forces designers to refrain from doing too much large quantity steps.
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The invention relates to reusable space transport systems. The proposed rocket contains an axisymmetric body with a payload, a propulsion system and takeoff and landing shock absorbers. Between the struts of these shock absorbers and the nozzle of the main engine, a heat shield is installed, made in the form of a hollow thin-walled compartment made of heat-resistant material. The technical result of the invention is to minimize the gas-dynamic and thermal loads on the shock absorbers from the operating propulsion engine during launches and landings of the launch vehicle and, as a result, ensure the required reliability of the shock absorbers during repeated (up to 50 times) use of the rocket. 1 ill.
Authors of the patent:
Vavilin Alexander Vasilievich (RU)
Usolkin Yuri Yurievich (RU)
Fetisov Vyacheslav Alexandrovich (RU)
Owners of patent RU 2309088:
Federal State Unitary Enterprise "State Missile Center" Design Bureau named after. Academician V.P. Makeeva" (RU)
The invention relates to rocket and space technology, in particular to reusable transport space systems (MTKS) of a new generation of the “Space orbital rocket - single-stage vehicle carrier” (“CORONA”) type with fifty to hundred times of its use without major repairs, which is a possible alternative to cruise reusable systems such as the Space Shuttle and Buran.
The CORONA system is designed to launch a payload (spacecraft (SC) and spacecraft with upper stages (UB) into low Earth orbits in the altitude range from 200 to 500 km with an inclination equal to or close to the inclination of the orbit of the launched spacecraft.
It is known that at launch the rocket is located at starting device, is in a vertical position and rests on the four support brackets of the tail compartment, which is subject to the weight of a fully fueled rocket and wind loads that create an overturning moment, which, when acted simultaneously, are the most dangerous for the strength of the tail compartment of the rocket (see, for example, I N. Pentsak, Flight theory and design of ballistic missiles, M.: Mashinostroenie, 1974, p. 112, Fig. 5.22, p. 217, Fig. 11.8, p. 219). The load when parking a fully fueled rocket is distributed across all support brackets.
One of fundamental issues The proposed MTKS is the development of takeoff and landing shock absorbers (TSA).
The work carried out at the State Missile Center (SRC) on the CORONA project showed that the most unfortunate event VPA loading is rocket landing.
The load on the VPA when a fully fueled rocket is parked is distributed over all supports, while during landing, with a high degree of probability, due to the permissible deviation from the vertical position of the rocket body, a case is possible where the load falls on one support. Taking into account the presence of vertical speed, this load turns out to be comparable or even greater than the parking load.
This circumstance made it possible to make a decision to abandon the special launch pad, transferring the power functions of the latter to the rocket’s VPA, which significantly simplifies the launch facilities for systems of the “CORONA” type, and accordingly, the costs of their construction are reduced.
The closest analogue of the proposed invention is a reusable single-stage launch vehicle "CORONA" for vertical takeoff and landing, containing an axisymmetric body with a payload, a propulsion system and takeoff and landing shock absorbers (see A.V. Vavilin, Yu.Yu. Usolkin "O possible ways of development of reusable transport space systems (MTKS)", RK technology, scientific and technical collection, series XIY, issue 1 (48), part P, calculation, experimental research and design of ballistic missiles with underwater launch, Miass, 2002 ., p.121, fig.1, p.129, fig.2).
The disadvantage of the design of an analogue rocket is that its PPAs are located in the zone of gas-dynamic and thermal influence of the flame emerging from the central nozzle of the main propulsion system (MPU) during repeated launch and landing of the rocket, as a result of which the reliable operation of the design of one PPA is not ensured with the required resource its use (up to one hundred flights with a twenty percent resource reserve).
The technical result when using a single-stage reusable vertical take-off and landing launch vehicle is to ensure the required reliability of the design of one propeller when using the launch vehicle fifty times by minimizing the gas-dynamic and thermal loads on the launch vehicle from the operating MDU during multiple launches and landings of the rocket.
The essence of the invention is that in a well-known single-stage reusable launch vehicle for vertical takeoff and landing, containing an axisymmetric body with a payload, a propulsion system and takeoff and landing shock absorbers, a heat shield is installed between the struts of the takeoff and landing shock absorbers and the nozzle of the propulsion engine .
Compared to the closest analogue rocket, the proposed single-stage reusable vertical takeoff and landing launch vehicle has better functional and operational capabilities, because it ensures the necessary reliability of the design of one UPA (not lower than 0.9994) for a given service life of one launch vehicle (up to one hundred launches) by isolating (using a heat shield) the UPA struts from the gas-dynamic and thermal loads of the operating MDU for a given resource (up to hundred) flights of the launch vehicle during its multiple launches and landings.
To explain the technical essence of the proposed invention, a diagram of the proposed launch vehicle with an axisymmetric body 1, a nozzle 2 of the propulsion system, struts of the takeoff and landing shock absorber 3 and a heat shield 4 of a hollow thin-walled compartment made of heat-resistant material, which isolates the struts of the takeoff and landing shock absorber from the gas-dynamic and thermal impact of the flame from the central nozzle of the main propulsion system during takeoff and landing of the rocket.
Thus, the proposed reusable vertical takeoff and landing launch vehicle has wider functional and operational capabilities compared to the closest analogue by increasing the reliability of one takeoff and landing shock absorber for a given flight life of the launch vehicle on which this takeoff and landing shock absorber is located.
A single-stage reusable launch vehicle for vertical takeoff and landing, containing an axisymmetric body with a payload, a propulsion system and takeoff and landing shock absorbers, characterized in that a heat shield made in the form of a hollow one is installed between the struts of the takeoff and landing shock absorbers and the nozzle of the propulsion engine thin-walled compartment made of heat-resistant material.
The development of a landing system - the number of supports, their arrangement, while minimizing their mass - is a very difficult task...
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Drawing from the book by Kazimir Simenovich Artis Magnae Artilleriae pars prima 1650
Multistage rocket- an aircraft consisting of two or more mechanically connected rockets, called steps, separated in flight. A multi-stage rocket allows you to achieve a speed greater than each of its stages individually.
Story
One of the first drawings depicting rockets was published in the work of the military engineer and artillery general Kazimir Simenovich, a native of the Vitebsk Voivodeship of the Polish-Lithuanian Commonwealth, “Artis Magnae Artilleriae pars prima” (Latin: “The Great Art of Artillery Part One”), published in the year in Amsterdam , Netherlands. On it is a three-stage rocket, in which the third stage is embedded in the second, and both of them together - in the first stage. The head part contained a composition for fireworks. The rockets were filled with solid fuel - gunpowder. This invention is interesting because more than three hundred years ago it anticipated the direction that modern rocketry would take.
The idea of using multistage rockets for space exploration was first expressed in the works of K. E. Tsiolkovsky. In the city he published his new book under the title "Space Rocket Trains". This term was used by K. Tsiolkovsky to describe composite missiles, or rather, an assembly of missiles that take off on the ground, then in the air, and finally in outer space. A train composed, for example, of 5 rockets is driven first by the first - the lead rocket; Once its fuel is used, it is unhooked and dropped to the ground. Then, in the same way, the second one begins to work, then the third, fourth and finally the fifth, the speed of which will by that time be high enough to be carried away into interplanetary space. The sequence of work from the head rocket is caused by the desire to force the rocket materials to work not in compression, but in tension, which will make the structure lighter. According to Tsiolkovsky, the length of each rocket is 30 meters. Diameters - 3 meters. Gases from the nozzles escape indirectly towards the axis of the rockets, so as not to put pressure on the following rockets. The take-off run on the ground is several hundred kilometers.
Despite the fact that in technical details rocket science has taken a largely different path (modern rockets, for example, do not “scatter” along the ground, but take off vertically, and the order of operation of the stages of a modern rocket is the reverse of what Tsiolkovsky spoke about ), the very idea of a multi-stage rocket remains relevant today.
Missile configuration options. From left to right:
1. single-stage rocket;
2. two-stage rocket with transverse separation;
3. two-stage rocket with longitudinal separation.
4. A rocket with external fuel tanks that are separated after the fuel in them is exhausted.
Structurally, multistage rockets are carried out with transverse or longitudinal separation of steps.
At cross section the stages are placed one above the other and operate sequentially one after another, turning on only after the separation of the previous stage. This scheme makes it possible to create systems, in principle, with any number of stages. Its disadvantage is that the resources of subsequent stages cannot be used during the operation of the previous one, being a passive load for it.
At longitudinal division the first stage consists of several identical rockets (in practice, from 2 to 8), located symmetrically around the body of the second stage, so that the resultant thrust forces of the first stage engines are directed along the axis of symmetry of the second, and operating simultaneously. This scheme allows the engine of the second stage to operate simultaneously with the engines of the first, thus increasing the total thrust, which is especially necessary during the operation of the first stage, when the mass of the rocket is maximum. But a rocket with longitudinal separation of stages can only be two-stage.
There is also a combined separation scheme - longitudinal-transverse, which allows you to combine the advantages of both schemes, in which the first stage is divided from the second longitudinally, and the division of all subsequent stages occurs transversely. An example of this approach is the domestic carrier Soyuz.
The Space Shuttle has a unique design of a two-stage longitudinally separated rocket, the first stage of which consists of two side-mounted solid rocket boosters, and in the second stage part of the fuel is contained in tanks orbiter(actually reusable ship), and most of it is in the separated external fuel tank. First, the orbiter propulsion system consumes fuel from the external tank, and when it is depleted, the external tank is reset and the engines continue to operate on the fuel contained in the orbiter tanks. This scheme makes it possible to make maximum use of the orbiter’s propulsion system, which operates throughout the entire launch of the spacecraft into orbit.
With transverse separation, the steps are connected to each other by special sections - adapters- supporting structures of cylindrical or conical shape (depending on the ratio of the diameters of the stages), each of which must withstand the total weight of all subsequent stages, multiplied by the maximum value of overload experienced by the rocket in all areas in which this adapter is part of the rocket.
With longitudinal division, power bands (front and rear) are created on the body of the second stage, to which the blocks of the first stage are attached.
The elements connecting the parts of a composite rocket give it the rigidity of a solid body, and when the stages are separated, they should almost instantly release the upper stage. Typically, the connection of steps is done using pyrobolts. A pyrobolt is a fastening bolt, in the rod of which a cavity is created next to the head, filled with a high explosive with an electric detonator. When a current pulse is applied to the electric detonator, an explosion occurs, destroying the bolt rod, causing its head to come off. The amount of explosives in the pyrobolt is carefully dosed so that, on the one hand, it is guaranteed to tear off the head, and, on the other, not to damage the rocket. When the stages are separated into electric detonators of all pyrobolts connecting the separated parts, a current pulse is simultaneously applied and the connection is released.
Next, the steps should be spaced a safe distance from each other. (Starting a high-stage engine near a low-stage engine can cause burnout fuel tank and an explosion of residual fuel, which would damage the upper stage or destabilize its flight.) When separating stages in the atmosphere, the aerodynamic force of the oncoming air flow can be used to separate them, and when separating in a void, auxiliary small solid rocket engines are sometimes used.
On liquid rockets, these same engines also serve to “sediment” the fuel in the tanks of the upper stage: when the engine of the lower stage is turned off, the rocket flies by inertia, in free fall, while the liquid fuel in the tanks is suspended, which can lead to to failure when starting the engine. Auxiliary engines provide the stage with a slight acceleration, under the influence of which the fuel “settles” on the bottom of the tanks.
In the above photo of the rocket
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Multistage rocket
A rocket whose launch vehicle includes more than one stage. A stage is a part of a rocket that is separated during flight, including units and systems that have completed their functioning at the time of separation. Home integral part stage is the propulsion system (see Rocket engine) of the stage, the operating time of which determines the operating time of other elements of the stage.
Propulsion systems belonging to different stages can operate either in series or in parallel. During sequential operation, the propulsion system of the next stage is switched on after the operation of the propulsion system of the previous stage is completed. In parallel operation, the propulsion systems of adjacent stages operate together, but the propulsion system of the preceding stage completes its operation and is separated before the operation of the subsequent stage is completed. Stage numbers are determined by the order in which they are separated from the rocket.
The prototype of multistage rockets are composite rockets, in which the spent parts were not supposed to be separated sequentially. Composite rockets were first mentioned in the 16th century in the work “On Pyrotechnics” (Venice, 1540) by the Italian scientist and engineer Vannoccio Biringuccio (1480-1539).
In the 17th century, the Polish-Belarusian-Lithuanian scientist Kazimir Seminovich (Seminavichus) (1600-1651) in his book “The Great Art of Artillery” (Amsterdam, 1650), which for 150 years was fundamental scientific work on artillery and pyrotechnics, provides drawings of multi-stage rockets. It is Semenovich, according to many experts, who is the first inventor of a multi-stage rocket.
The first patent in 1911 for a multistage rocket was received by the Belgian engineer Andre Bing. The Bing rocket moved by sequentially detonating powder bombs. In 1913, the American scientist Robert Goddard became the owner of the patent. The Godard rocket design provides for sequential separation of stages.
At the beginning of the 20th century, a number of famous scientists were engaged in the study of multistage rockets. The most significant contribution to the idea of creating and practical use multistage rockets were contributed by K.E. Tsiolkovsky (1857-1935), who outlined his views in the works “Rocket Space Trains” (1927) and “ Highest speed rockets" (1935). Ideas of Tsiolkovsky K.E. have become widespread and implemented.
In the Strategic Missile Forces, the first multi-stage missile put into service in 1960 was the R-7 missile (see Missile strategic purpose). The propulsion systems of two stages of the rocket, placed in parallel, using liquid oxygen and kerosene as fuel components, ensured the delivery of 5400 kg. payload for a range of up to 8000 km. It was impossible to achieve the same results with a single-stage rocket. In addition, in practice it was found that when moving from a single-stage to a two-stage rocket design, it is possible to achieve a multiple increase in range with a less significant increase in launch mass.
This advantage was clearly demonstrated during the creation of a single-stage rocket. medium range R-14 and two-stage intercontinental missile R-16. While the main energy characteristics are similar, the flight range of the R-16 missile is 2.5 times greater than the R-14 missile, while its launch mass is only 1.6 times greater.
While creating modern missiles the choice of the number of stages is determined by many factors, namely, the energy characteristics of the fuels, the properties of structural materials, the perfection of the design of the units and systems of the rocket, etc. It is also taken into account that the design of a rocket with a smaller number of stages is simpler, its cost is lower, and the creation time is shorter. Analysis of the design of modern rockets makes it possible to identify the dependence of the number of stages on the type of fuel and flight range.