Multistage missile: Ministry of Defense of the Russian Federation. Why are rockets made multi-stage? Scheme with hanging tanks

The project was developed at the request of a venture investor from the EU.

The cost of launching spacecraft into orbit is still very high. This is due to the high cost of rocket engines, an expensive control system, expensive materials used in the stressed design of rockets and their engines, complex and usually expensive technology for their manufacture, preparation for launch, and, mainly, their one-time use.

The share of the cost of the carrier in the total cost of launching a spacecraft varies. If the media is serial, and the device is unique, then about 10%. On the contrary, it can reach 40% or more. It is very expensive, and therefore the idea arose to create a launch vehicle that, like an air liner, would take off from the cosmodrome, fly into orbit and, leaving a satellite or spacecraft there, would return to the cosmodrome.

The first attempt to implement such an idea was the creation of the Space Shuttle system. Based on the analysis of the shortcomings of disposable carriers and the Space Shuttle system, which was made by Konstantin Feoktistov (K. Feoktistov. The trajectory of life. Moscow: Vagrius, 2000. ISBN 5-264-00383-1. Chapter 8. Rocket as an airplane), there is an idea of ​​the qualities that a good launch vehicle should have to ensure the delivery of a payload into orbit at minimal cost and with maximum reliability. It should be a reusable system capable of 100-1000 flights. Reusability is needed both to reduce the cost of each flight (development and manufacturing costs are distributed over the number of flights), and to increase the reliability of launching a payload into orbit: every trip by car and flight of an aircraft confirms the correctness of its design and high-quality manufacturing. Consequently, it is possible to reduce the cost of insuring the payload and insuring the rocket itself. Only reusable machines can be truly reliable and inexpensive to operate - such as a steam locomotive, a car, an airplane.

The rocket must be single-stage. This requirement, like reusability, is associated with minimizing costs and ensuring reliability. Indeed, if the rocket is multi-stage, then even if all its stages return safely to Earth, then before each launch they must be assembled into a single whole, and it is impossible to check the correct assembly and functioning of the processes of stage separation after assembly, since with each check the assembled machine must crumble . Not tested, not tested for functioning after assembly, the connections become, as it were, disposable. And a packet connected by nodes with reduced reliability also becomes disposable to some extent. If the rocket is multi-stage, then the cost of its operation is greater than the cost of operating a single-stage machine for the following reasons:

• For a single stage machine, no assembly costs are required.
• There is no need to allocate landing areas on the Earth's surface for the landing of the first stages, and, consequently, there is no need to pay for their rent, for the fact that these areas are not used in the economy.
• There is no need to pay for the transportation of the first steps to the launch site.
• Refueling a multi-stage rocket requires more complex technology, more time. The assembly of the package and the delivery of the stages to the launch site are not amenable to simple automation and, therefore, require the participation of more specialists in preparing such a rocket for the next flight.

The rocket must use hydrogen and oxygen as fuel, as a result of which combustion produces environmentally friendly combustion products at the output of the engine with a high specific impulse. Environmental cleanliness is important not only for work carried out at the start, during refueling, in the event of an accident, but also to avoid the harmful effects of combustion products on the ozone layer of the atmosphere.

Skylon, DC-X, Lockheed Martin X-33 and Roton are among the most developed projects of single-stage spacecraft abroad. If Skylon and X-33 are winged vehicles, then DC-X and Roton are vertical takeoff and vertical landing missiles. In addition, both of them went as far as creating test samples. If Roton had only an atmospheric prototype for practicing autorotation landing, then the DC-X prototype made several flights to a height of several kilometers on a liquid-propellant rocket engine (LRE) on liquid oxygen and hydrogen.

Technical description of the Zeya rocket

To radically reduce the cost of launching cargo into space, Lin Industrial proposes to create a Zeya launch vehicle (LV). It is a single-stage, reusable vertical take-off and vertical landing transport system. It uses environmentally friendly and highly efficient fuel components: oxidizer - liquid oxygen, fuel - liquid hydrogen.

The launch vehicle consists of an oxidizer tank (above which is a heat shield for atmospheric entry and a soft landing rotor), a payload compartment, an instrument compartment, a fuel tank, a tail compartment with a propulsion system, and a landing gear. Fuel and oxidizer tanks - segmental-conical, load-bearing, composite. The fuel tank is pressurized by liquid hydrogen gasification, and the oxidizer tank is pressurized by compressed helium from high-pressure cylinders. The marching propulsion system consists of 36 engines located around the circumference and an external expansion nozzle in the form of a central body. Control during operation of the main engine in pitch and yaw is carried out by throttling diametrically located engines, in roll - with the help of eight engines on gaseous fuel components located under the payload compartment. Engines on gaseous propellant components are used for control in the orbital flight segment.

The flight pattern of the Zeya is as follows. After entering the reference near-Earth orbit, the rocket, if necessary, performs orbital maneuvers to enter the target orbit, after which, by opening the payload compartment (weighing up to 200 kg), it separates it.

During one revolution in near-Earth orbit from the moment of launch, having given out a braking impulse, the Zeya lands in the area of ​​the launch cosmodrome. High landing accuracy is ensured by using the lift-to-drag ratio created by the shape of the rocket for lateral and range maneuvers. A soft landing is carried out by descending using the principle of autorotation and eight landing shock absorbers.

Economy

Below is an estimate of the time and cost of work before the first start-up:

• Pilot project: 2 months - €2 million
• Creation of the propulsion system, development of composite tanks and control system: 12 months - €100 million
• Creation of a bench base, construction of prototypes, preparation and modernization of production, draft design: 12 months - €70 million
• Development of components and systems, prototype testing, fire testing of a flight product, technical design: 12 months - €143 million

Total: 3.2 years, €315 million

According to our estimates, the cost of one launch will be €0.15 million, and the cost of inter-flight maintenance and overhead costs will be about € 0.1 million for the interlaunch period. If you set the launch price in € 35 thousand per 1 kg (at a cost of €1250/kg), which is close to the launch price on the Dnepr rocket for foreign customers, the entire launch (200 kg payload) will cost the customer € 7 million. Thus, the project will pay off in 47 launches.

Zeya variant with a three-component engine

Another way to increase the efficiency of a single-stage launch vehicle is to switch to an LRE with three fuel components.

Since the early 1970s, the concept of three-component engines has been studied in the USSR and the USA, which would combine a high specific impulse when using hydrogen as a fuel, and a higher average fuel density (and, consequently, a smaller volume and weight of fuel tanks), characteristic of hydrocarbon fuels. At start-up, such an engine would run on oxygen and kerosene, and at high altitudes it would switch to using liquid oxygen and hydrogen. Such an approach may make it possible to create a single-stage space carrier.

In our country, three-component engines RD-701, RD-704 and RD0750 were developed, but they were not brought to the stage of creating prototypes. In the 1980s, NPO Molniya developed the Multipurpose Aerospace System (MAKS) based on the RD-701 liquid-propellant rocket engine with oxygen + kerosene + hydrogen fuel. Calculations and design of three-component rocket engines were also carried out in America (see, for example, Dual-Fuel Propulsion: Why it Works, Possible Engines, and Results of Vehicle Studies, by James A. Martin and Alan W. Wilhite , published in May 1979 in Am erican Institute of Aeronautics and Astronautics (AIAA) Paper No. 79-0878).

We believe that for the three-component Zeya, liquid methane should be used instead of the kerosene traditionally offered for such liquid-propellant rocket engines. There are many reasons for this:

• Zeya uses liquid oxygen as an oxidizer, boiling at a temperature of -183 degrees Celsius, that is, cryogenic equipment is already used in the design of the rocket and the refueling complex, which means that there will be no fundamental difficulties in replacing a kerosene tank with a methane tank at -162 degrees Celsius.
• Methane is more efficient than kerosene. The specific impulse (SI, a measure of LRE efficiency - the ratio of the impulse created by the engine to fuel consumption) of the methane + liquid oxygen fuel pair exceeds the SI of the kerosene + liquid oxygen pair by about 100 m/s.
• Methane is cheaper than kerosene.
• Unlike kerosene engines, there is almost no coking in methane engines, that is, in other words, the formation of hard-to-remove soot. And, therefore, such engines are more convenient to use in reusable systems.
• If necessary, methane can be replaced with a similar liquefied natural gas (LNG). LNG consists almost entirely of methane, has similar physical and chemical characteristics, and is slightly less efficient than pure methane. At the same time, LNG is 1.5–2 times cheaper than kerosene and much more affordable. The fact is that Russia is covered by an extensive network of natural gas pipelines. It is enough to take a branch to the cosmodrome and build a small gas liquefaction complex. Also in Russia, an LNG plant was built on Sakhalin and two small-scale liquefaction complexes in St. Petersburg. It is planned to build five more plants in different parts of the Russian Federation. At the same time, the production of rocket kerosene requires special grades of oil extracted from strictly defined fields, the reserves of which are depleted in Russia.

The scheme of operation of a three-component launch vehicle is as follows. First, methane is burned - a fuel with a high density, but a relatively small specific impulse in a vacuum. Then hydrogen is burned - a fuel with a low density and the highest possible specific impulse. Both types of fuel are burned in a single propulsion system. The higher the proportion of fuel of the first type, the smaller the mass of the structure, but the greater the mass of the fuel. Accordingly, the higher the proportion of fuel of the second type, the lower the required fuel supply, but the greater the mass of the structure. Therefore, it is possible to find the optimal ratio between the masses of liquid methane and hydrogen.

We carried out the corresponding calculations, taking the coefficient of fuel compartments for hydrogen equal to 0.1, and for methane - 0.05. The fuel compartment ratio is the ratio of the final mass of the fuel compartment to the mass of the available fuel supply. The final mass of the fuel compartment includes the masses of the guaranteed fuel supply, the unusable residues of propellant components, and the mass of pressurization gases.

Calculations have shown that the three-component Zeya will launch 200 kg of payload into low Earth orbit with a mass of its structure of 2.1 tons and a launch mass of 19.2 tons. The two-component Zeya on liquid hydrogen loses a lot: the mass of the structure is 4, 8 tons, and the starting weight is 37.8 tons.

Drawing from the book of Kazimir Simenovich Artis Magnae Artilleriae pars prima 1650

Multistage rocket- an aircraft consisting of two or more mechanically connected missiles, called steps separating in flight. A multi-stage rocket allows you to achieve a speed greater than each of its stages separately.

Story

One of the first drawings depicting rockets was published in the work of a military engineer and artillery general Kazimir Simenovich, a native of the Vitebsk Voivodeship of the Commonwealth, "Artis Magnae Artilleriae pars prima" (lat. "Great art of artillery part one"), printed in the year in Amsterdam , Netherlands . On it is a three-stage rocket, in which the third stage is nested in the second, and both of them together are in the first stage. The composition for fireworks was placed in the head part. The rockets were filled with solid fuel - gunpowder. This invention is interesting in that more than three hundred years ago it anticipated the direction in which modern rocket technology went.

For the first time, the idea of ​​using multi-stage rockets for space exploration is expressed in the works of K. E. Tsiolkovsky. In the city he published his new book entitled Space Rocket Trains. K. Tsiolkovsky called this term compound rockets, or rather, an assembly of rockets that take off on the ground, then in the air and, finally, in outer space. A train, made up, for example, of 5 missiles, is first guided by the first - the head missile; after using its fuel, it is unhooked and thrown to the ground. Further, in the same way, the second begins to work, then the third, the 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 with the head rocket is caused by the desire to make rocket materials work not in compression, but in tension, which will make it easier to design. According to Tsiolkovsky, the length of each rocket is 30 meters. Diameters - 3 meters. Gases from the nozzles escape indirectly to the axis of the rockets, so as not to put pressure on the following rockets. The length of the takeoff run on the ground is several hundred kilometers.

Despite the fact that, in terms of technical details, rocket science has gone in many ways along a 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 opposite, in relation to the one that Tsiolkovsky spoke about ), the very idea of ​​a multi-stage rocket remains relevant today.

Rocket options. From left to right:
1. single-stage rocket;
2. two-stage rocket with transverse separation;
3. Two-stage missile with longitudinal separation.
4. Rocket with external fuel tanks, detachable after the exhaustion of fuel in them.

Structurally, multi-stage rockets are carried out c transverse or longitudinal separation of steps.
At transverse separation the stages are placed one above the other and work sequentially one after the other, turning on only after the separation of the previous stage. Such a scheme makes it possible to create systems, in principle, with any number of steps. Its disadvantage lies in the fact that the resources of subsequent stages cannot be used in the work of the previous one, being a passive burden 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 of the thrust forces of the first stage engines is directed along the axis of symmetry of the second, and working simultaneously. Such a 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 a 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.

The Space Shuttle spacecraft has a unique layout of a two-stage rocket with longitudinal separation, the first stage of which consists of two side solid-propellant boosters, and in the second stage part of the fuel is contained in tanks orbiter(actually a reusable ship), and most of them - in a detachable external fuel tank. First, the orbiter's propulsion system consumes fuel from the external tank, and when it is exhausted, the external tank is dumped and the engines continue to operate on the fuel contained in the orbiter's tanks. Such a scheme makes it possible to make maximum use of the orbiter's propulsion system, which operates throughout the spacecraft's launch into orbit.

With a transverse separation, the steps are interconnected by special sections - adapters- bearing 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 the overload experienced by the rocket in all areas where this adapter is part of the rocket.
With longitudinal separation, 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 that connect the parts of a composite rocket give it the rigidity of a single body, and when the stages are separated, they should almost instantly release the upper stage. Usually the steps are connected using pyrobolts. A pyrobolt is a fastening bolt, in the shaft of which a cavity is created near 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 shaft, as a result of which its head comes 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 hand, not to damage the rocket. When the stages are separated, the electric detonators of all pyrobolts connecting the separated parts are simultaneously supplied with a current pulse, and the connection is released.
Next, the steps should be divorced at a safe distance from each other. (Starting the upper stage engine close to the lower one can burn out its fuel tank and explode the remaining fuel, which will damage the upper stage or destabilize its flight.) When the stages are separated in the atmosphere, the aerodynamic force of the oncoming air flow can be used to separate them, and In the void, auxiliary small solid rocket motors are sometimes used.
On liquid-propellant rockets, the same engines also serve to "precipitate" 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 in suspension, which can lead to failure when starting the engine. Auxiliary engines impart a slight acceleration to the stages, under the influence of which the fuel "settles" on the bottoms of the tanks.
In the above picture of the rocket

The launch was carried out with the help of a multi-stage rocket,” we have read these words many times in reports about the launch of the world's first artificial satellites of the Earth, about the creation of a satellite of the Sun, about the launch of space rockets to the Moon. Just one short phrase, and how much inspired work of scientists, engineers and workers of our Motherland is hidden behind these six words!

What are modern multi-stage rockets? Why did it become necessary to use rockets consisting of a large number of stages for space flights? What is the technical effect of increasing the number of rocket stages?

Let's try to briefly answer these questions. To carry out flights into space, huge reserves of fuel are required. They are so large that they cannot be placed in the tanks of a single-stage rocket. With the current level of engineering science, it is possible to build a rocket in which fuel would account for up to 80-90% of its total weight. And for flights to other planets, the required fuel reserves should be hundreds and even thousands of times greater than the own weight of the rocket and the payload in it. With those reserves of fuel that can be placed in the tanks of a single-stage rocket, it is possible to achieve a flight speed of up to 3-4 km / s. The improvement of rocket engines, the search for the most advantageous grades of fuel, the use of higher quality structural materials, and further improvement in the design of rockets will certainly make it possible to slightly increase the speed of single-stage rockets. But it will still be very far from cosmic speeds.

To achieve cosmic speeds, K. E. Tsiolkovsky proposed the use of multi-stage rockets. The scientist himself figuratively called them "rocket trains." According to Tsiolkovsky, a rocket train, or, as we say now, a multi-stage rocket, should consist of several rockets mounted one on top of the other. The bottom rocket is usually the largest. She carries the entire "train". Subsequent steps are made smaller and smaller.

When taking off from the surface of the Earth, the engines of the lower rocket work. They act until they use up all the fuel in her tanks. When the tanks of the first stage are empty, it separates from the upper rockets so as not to burden their further flight with dead weight. The separated first stage with empty tanks continues to fly upwards for some time by inertia, and then falls to the ground. To save the first stage for reuse, it can be parachuted down.

After the separation of the first stage, the engines of the second stage are switched on. They begin to act when the rocket has already risen to a certain height and has a significant flight speed. Second-stage engines accelerate the rocket further, increasing its speed by a few more kilometers per second. After all the fuel contained in the tanks of the second stage is used up, it is also dumped. The further flight of the composite rocket is ensured by the operation of the engines of the third stage. Then the third stage is dropped. The queue approaches the fourth stage engines. Having done the work assigned to them, they increase the speed of the rocket by a certain amount, and then give way to the fifth stage engines. After resetting the fifth stage, the sixth engines start to work.

So, each stage of the rocket successively increases the flight speed, and the last, upper stage reaches the required cosmic speed in airless space. If the task is to land on another planet and return back to Earth, then the rocket that has flown into space, in turn, must consist of several stages, which are sequentially switched on when descending to the planet and when taking off from it.

It is interesting to see what effect the use of a large number of stages on rockets gives.

Take a single-stage rocket with a launch weight of 500 tons. Suppose that this weight is distributed as follows: payload - 1 ton, dry weight of the stage - 99.8 tons and fuel - 399.2 tons. Therefore, the structural perfection of this rocket is such that the weight fuel is 4 times the dry weight of the stage, that is, the weight of the rocket itself without fuel and payload. The Tsiolkovsky number, that is, the ratio of the launch weight of the rocket to its weight after all the fuel has been used up, for this rocket will be 4.96. This number and the rate at which the gas exits the engine nozzle determines the speed that the rocket can reach. Let us now try to replace a single-stage rocket with a two-stage one. Let us again take a payload of 1 ton and assume that the design perfection of the stages and the gas outflow velocity will remain the same as in a single-stage rocket. Then, as calculations show, to achieve the same flight speed as in the first case, a two-stage rocket with a total weight of only 10.32 tons is required, that is, almost 50 times lighter than a single-stage one. The dry weight of a two-stage rocket will be 1.86 tons, and the weight of the fuel placed in both stages will be 7.46 tons. As you can see, in the example under consideration, replacing a single-stage rocket with a two-stage one makes it possible to reduce the consumption of metal and fuel by 54 times when launching the same payload .

Let's take for example a space rocket with a payload of 1 ton. Let this rocket have to break through the dense layers of the atmosphere and, flying into airless space, develop a second cosmic velocity - 11.2 km / s. Our diagrams show the change in the weight of such a space rocket depending on the weight fraction of fuel in each stage and on the number of stages (see page 22).

It is easy to calculate that if you build a rocket whose engines throw off gases at a speed of 2,400 m / s and in each of the stages the fuel accounts for only 75% of the weight, then even with six stages, the take-off weight of the rocket will be very large - almost 5.5 thousand tons. By improving the design characteristics of the rocket stages, it is possible to achieve a significant reduction in the starting weight. So, for example, if the fuel accounts for 90% of the weight of the stage, then a six-stage rocket can weigh 400 tons.

The use of high-calorific fuel in rockets and the increase in the efficiency of their engines produce an exceptionally great effect. If in this way the speed of gas outflow from the engine nozzle is increased by only 300 m/s, bringing it to the value indicated on the graph - 2,700 m/s, then the launch weight of the rocket can be reduced several times. A six-stage rocket, in which the fuel weight is only 3 times the weight of the stage structure, will have a launch weight of approximately 1.5 thousand tons. And by reducing the structure weight to 10% of the total weight of each stage, we can reduce the launch weight of the rocket with the same up to 200 steps

If we increase the speed of the outflow of gas by another 300 m/sec, that is, take it equal to 3 thousand m/sec, then an even greater reduction in weight will occur. For example, a six-stage rocket with a fuel weight fraction of 75% will have a launch weight of 600 tons. By increasing the fuel weight fraction to 90%, it is possible to create a space rocket with only two stages. Its weight will be about 850 tons. By doubling the number of stages, you can reduce the weight of the rocket to 140 tons. And with six stages, the take-off weight will drop to 116 tons.

This is how the number of stages, their design perfection and the speed of gas outflow affect the weight of the rocket.

Why, then, with an increase in the number of stages, the required fuel reserves decrease, and with them the total weight of the rocket? This is because the greater the number of stages, the more often empty tanks will be discarded, the rocket will be freed from useless cargo faster. At the same time, with an increase in the number of stages, at first the take-off weight of the rocket decreases very much, and then the effect of increasing the number of stages becomes less significant. It can also be noted, as can be clearly seen in the graphs, that for rockets with a relatively poor design characteristic, an increase in the number of stages has a greater effect than for rockets with a high percentage of fuel in each stage. This is quite understandable. If the shells of each stage are very heavy, then they must be dropped as quickly as possible. And if the hull has a very low weight, then it does not burden the missiles too much, and frequent drops of empty hulls no longer have such a great effect.

When rockets fly to other planets, the required fuel consumption is not limited to the amount that is necessary for acceleration during takeoff from the Earth. Approaching another planet, the spacecraft falls into its sphere of attraction and begins to approach its surface with increasing speed. If the planet is deprived of an atmosphere capable of extinguishing at least part of the speed, then the rocket, when falling on the surface of the planet, will develop the same speed that is necessary to fly away from this planet, that is, the second space velocity. The value of the second cosmic velocity, as is known, is different for each planet. For example, for Mars it is 5.1 km/sec, for Venus - 10.4 km/sec, for the Moon - 2.4 km/sec. In the case when the rocket flies up to the sphere of attraction of the planet, having a certain speed relative to the latter, the speed of the fall of the rocket will be even greater. For example, the second Soviet space rocket reached the surface of the Moon at a speed of 3.3 km/sec. If the task is to ensure a smooth landing of the rocket on the surface of the Moon, then additional fuel supplies must be on board the rocket. To extinguish any speed, it is required to use as much fuel as is necessary for the rocket to develop the same speed. Consequently, a space rocket intended for the safe delivery of some kind of cargo to the lunar surface must carry significant reserves of fuel. A single-stage rocket with a payload of 1 ton should have a weight of 3-4.5 tons, depending on its design perfection.

Previously, we showed what an enormous weight rockets must have in order to carry a load of 1 ton into outer space. And now we see that only a third or even a fourth of this load can be safely lowered to the surface of the Moon. The rest should be fuel, storage tanks, engine and control system.

What should be the final weight of a space rocket intended for the safe delivery of scientific equipment or other payload weighing 1 ton to the lunar surface?

In order to give an idea of ​​ships of this type, in our figure, a five-stage rocket is conventionally shown in section, designed to deliver a container with scientific equipment weighing 1 ton to the surface of the Moon. The calculation of this rocket was based on the technical data given in a large number of books (for example, in the books of V. Feodosyev and G. Sinyarev "Introduction to Rocketry" and Sutton "Rocket Engines").

Liquid propellant rocket engines were taken. To supply fuel to the combustion chambers, turbopump units are provided, driven by the decomposition products of hydrogen peroxide. The average gas outflow velocity for the first stage engines is assumed to be 2,400 m/s. The engines of the upper stages operate in highly rarefied layers of the atmosphere and in an airless space, so their efficiency turns out to be somewhat higher and for them the gas outflow velocity is assumed to be 2,700 m/sec. For the design characteristics of the stages, such values ​​were adopted that are found in rockets described in the technical literature.

With the selected initial data, the following weight characteristics of the space rocket were obtained: take-off weight - 3,348 tons, including 2,892 tons of fuel, 455 tons of structure and 1 ton of payload. The weight of the individual stages was distributed as follows: the first stage - 2,760 tons, the second - 495 tons, the third - 75.5 tons, the fourth - 13.78 tons, the fifth - 2.72 tons. The height of the rocket reached 60 m, the diameter of the lower stage - 10 m

At the first stage, 19 engines with a thrust of 350 tons each were delivered. On the second - 3 of the same engines, on the third - 3 engines with a thrust of 60 tons each. On the fourth - one with a thrust of 35 tons and at the last stage - an engine with a thrust of 10 tons.

When taking off from the surface of the Earth, the engines of the first stage accelerate the rocket to a speed of 2 km / s. After the empty body of the first stage is dropped, the engines of the next three stages are turned on, and the rocket acquires a second space velocity.

Further, the rocket flies by inertia to the Moon. Approaching its surface, the rocket turns its nozzle down. The fifth stage engine is turned on. It dampens the falling speed, and the rocket smoothly descends to the lunar surface.

The above figure and the calculations related to it, of course, do not represent a real project for a lunar rocket. They are given only to give a first idea of ​​the scale of space multistage rockets. It is absolutely clear that the design of a rocket, its dimensions and weight depend on the level of development of science and technology, on the materials at the disposal of the designers, on the fuel used and the quality of the rocket engines, on the skill of its builders. The creation of space rockets presents boundless scope for the creativity of scientists, engineers, and technologists. There are still many discoveries and inventions to be made in this area. And with each new achievement, the characteristics of missiles will change.

Just as modern airships of the IL-18, TU-104, TU-114 types are not like the airplanes that flew at the beginning of this century, so space rockets will be continuously improved. Over time, for space flights, rocket engines will use not only the energy of chemical reactions, but also other sources of energy, such as the energy of nuclear processes. With the change in the types of rocket engines, the design of the rockets themselves will also change. But the remarkable idea of ​​​​K. E. Tsiolkovsky about the creation of "rocket trains" will always play an honorable role in the study of the vast expanses of space.

On fig. 22 shows that the trajectory of a ballistic missile, and hence the range of its flight, depends on the initial velocity V 0 and the angle Θ 0 between this velocity and the horizon. This angle is called the throw angle.

Let, for example, the throwing angle is equal to Θ 0 = 30°. In this case, the rocket, which started its ballistic flight at point 0 with a speed V 0 = 5 km/sec, will fly along the elliptic curve II. At V 0 = 8 km/sec, the rocket will fly along an elliptical curve III, at V 0 = 9 km/sec, along curve IV. When the speed is increased to 11.2 km/s, the trajectory from a closed elliptic 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 will escape along a hyperbole (VI). This is how the rocket trajectory changes with a change in the initial speed, although the angle of throw remains unchanged.

If you keep the initial speed constant, and change only the angle of throw, then the trajectory of the rocket will undergo no less significant changes.

Let, for example, the initial "speed is equal to V 0 = 8 km / h. If the rocket is launched vertically upwards (throw 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 angle of throw, the range of missiles at the same initial speed of 8 km / s can have a range from zero to infinity.

At what angle will the rocket start its ballistic flight? It depends on the control program that is given to the rocket. It is possible, for example, for each initial speed to choose the most advantageous (optimal) throwing angle at which the flight range will be the greatest. As the initial speed increases, this angle decreases. The resulting approximate values ​​​​of the range, altitude and flight time are shown in Table. four.

Table 4

If the throwing angle can be changed arbitrarily, then the change in the initial speed is limited, and its increase by every 1 km / s is associated with great technical problems.

K. E. Tsiolkovsky gave a formula that makes it possible to determine the ideal speed of a rocket at the end of its acceleration by engines:

V id \u003d V ist ln G start / G end,

where V id - the ideal speed of the rocket at the end of the active section;

V ist - the speed of the outflow of gases from the jet nozzle of the engine;

G beg - the initial weight of the rocket;

G con - the final weight of the rocket;

ln is the sign of the natural logarithm.

We got acquainted with the value of the speed of the outflow of gases from the nozzle of a rocket engine in the previous section. For liquid fuels given in table. 3, these speeds are limited to 2200 - 2600 m / s (or 2.2 - 2.6 km / s), and for solid fuels - to 1.6 - 2.0 km / s.

G start denotes the initial weight, i.e., the total weight of the rocket before launch, and G end is its final weight at the end of acceleration (after running out of fuel or turning off the engines). The ratio of these weights G beg /G con, included in the formula, is called the Tsiolkovsky number and indirectly characterizes the weight of the fuel used to accelerate the rocket. Obviously, the larger the Tsiolkovsky number, the greater the speed the rocket will develop and, consequently, the farther it will fly (ceteris paribus). However, the Tsiolkovsky number, as well as the speed of the outflow of gases from the nozzle, has its limitations.

On fig. 23 shows a section of a typical single-stage rocket and its weight diagram. In addition to fuel tanks, the rocket has engines, controls and control systems, skin, payload, and various structural elements and 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 that the Tsiolkovsky number of this rocket was: 12.9 / 3.9 = 3.31. At the current level of development of foreign rocket science, this ratio for foreign rockets reaches 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 \u003d 2.6 ln 7 \u003d 2.6 1.946 ≈ 5 km / s.

From 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 expends its energy not only on rocket acceleration, but also on overcoming air resistance, on overcoming 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*.

* (The 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 firing in an easterly direction, the flight range of ballistic missiles is 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 Earth satellites and spacecraft, and even more so to send space rockets to the Moon and planets, it is necessary to impart a significantly higher speed to the carrier rocket. So, for a missile with a range of 9000 - 13000 km, an initial speed of about 7 km / s is required. The first cosmic velocity that must be given to a rocket so that it can become a satellite of the Earth with a low orbital altitude is, as is known, 8 km/sec.

To exit the Earth's sphere of gravity, the rocket must be accelerated to the second cosmic velocity - 11.2 km / s, to fly around the Moon (without returning to Earth) a speed of more than 12 km / s is required. A flyby of Mars without returning to Earth can be carried out at an initial speed of about 14 km/s, and with a return to orbit around the Earth - about 27 km/s. A speed of 48 km/s is required to reduce the duration of a flight to Mars and back to three months. Increasing the speed of the rocket, in turn, requires the expenditure of an ever-increasing amount of fuel for acceleration.

Suppose, for example, we have built a rocket weighing 1 kg without fuel. If we want to tell her the speed of 3, 6, 9 and 12 km / s, then how much fuel will need to be filled into the rocket and burned during acceleration? The required amount of fuel * is shown in table. 5.

* (With an outflow velocity of 3 km/sec.)

Table 5

There is no doubt that in the body of a rocket, 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 his 6.4 kg. And, obviously, it is absolutely impossible to fill it with 19 or 54 kg of fuel. A simple but strong enough tank that can hold such an amount of fuel already weighs much 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, should 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 task as achieving the rocket speeds that are required by practice today. This path consists in the creation of multi-stage rockets.

A typical multi-stage rocket is shown in Fig. 24. It consists of a payload AND several detachable stages with a power plant and a supply of fuel in each. The engine of the first stage informs the payload, as well as the second and third stages (the second sub-rocket) with the speed ν 1 . After the fuel is used up, the first stage separates from the rest of the rocket and falls to the ground, and the second stage engine is turned on on the rocket. Under the action of its thrust, the remaining part of the rocket (the third sub-rocket) acquires an additional speed ν 2 . Then the second stage, after running out of fuel, also separates from the rest of the rocket and falls to the ground. At this time, the third stage engine turns on and informs the payload of the additional speed ν 3 .

Thus, in a multi-stage rocket, the payload accelerates many times. The total ideal speed of a three-stage rocket will be equal to the sum of the three ideal speeds obtained from each stage:

V id 3 \u003d ν 1 + ν 2 + ν 3.

If the speed of the outflow of gases 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 one does not change, then the speed increments 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, in each stage of multi-stage rockets there may be engines that give different exhaust velocities; a constant weight ratio may not be maintained; air resistance as the flight speed changes and the attraction of the Earth as you move away from it change. Therefore, the final speed of a multi-stage 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 over.

* (It should also be borne in mind that between turning off one stage and turning on another, there may be a time interval during which the rocket flies by inertia.)

In addition, a multi-stage rocket can provide a given range of the same payload at a significantly lower total fuel consumption and launch weight than a single-stage rocket. Has the human mind managed to circumvent the laws of nature? No. Just a person, having learned these laws, can save on fuel and weight of the structure, performing the task. In a single-stage rocket, from the very start to the end of the active section, we accelerate all of its "dry" weight. In a multi-stage rocket, we don't do that. So, in a three-stage rocket, the second stage no longer spends fuel to accelerate the "dry" weight of the first stage, because the latter is discarded. The third stage also does not waste fuel for acceleration of the "dry" weight of the first and second stages. It accelerates only itself and the payload. The third (and in general 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, the separation of the last stages is practiced in carrier rockets of satellites, space rockets and such combat missiles as Atlas, Titan, Minuteman, Jupiter, Polaris, etc.

When scientific equipment placed in the head part of the rocket is launched into space, separation of the last stage is envisaged. This is necessary for the correct functioning of the equipment. When a satellite is launched, it is also provided for its separation from the last stage. Due to this, resistance is reduced and it can exist for a long time. When launching a combat ballistic missile, the separation of the last stage from the combat head is provided, as a result of which it becomes more difficult to detect the combat head and hit it with an anti-missile. Moreover, the last stage separated during the descent of the rocket becomes a decoy. If during reentry into 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 a smaller 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 problem of obtaining high speeds will be solved 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 steps. Therefore, scientists will always strive for the minimum number of steps, and for this, first of all, it is necessary to learn how to get more and more speeds of the outflow of combustion products or products of some other reaction.

What is the device of a multi-stage rocket Let's take a look at the classic example of a rocket for space flight, described in the writings of Tsiolkovsky, the founder of rocket science. It was he who was the first to publish the fundamental idea of ​​manufacturing a multi-stage rocket.

The principle of the rocket.

In order to overcome gravity, the rocket needs a large supply of fuel, and the more fuel we take, the greater the mass of the rocket. Therefore, to reduce the mass of the rocket, they are built on the principle of multistage. Each stage can be considered as a separate rocket with its own rocket engine and fuel supply for flight.

The device of the stages of a space rocket.

The first stage of a space rocket the largest, in a rocket for space flight, there can be up to 6 engines of the 1st stage, and the more heavy the load must be brought into space, the more engines in the first stage of the rocket.

In the classic version, there are three of them, located symmetrically along the edges of an isosceles triangle, as if encircling the rocket around the perimeter. This stage is the largest and most powerful, it is she who tears off the rocket. When the fuel in the rocket's first stage is used up, the entire stage is discarded.

After that, the movement of the rocket is controlled by the engines of the second stage. They are sometimes called accelerating, since it is with the help of the engines of the second stage that the rocket reaches the first space velocity, sufficient to reach the near-Earth orbit.

This can be repeated several times, with each stage of the rocket weighing less than the previous one, since the force of gravity of the Earth decreases with the climb.

How many times this process is repeated, so many steps are contained in a space rocket. The last stage of the rocket is designed for maneuvering (flight correction engines are available in each stage of the rocket) and delivery of the payload and astronauts to their destination.

We reviewed the device how a rocket works, ballistic multi-stage missiles, a terrible weapon carrying nuclear weapons, are arranged in exactly the same way and do not fundamentally differ from space rockets. They are capable of completely destroying both life on the entire planet and itself.

Multistage ballistic missiles go into near-Earth orbit and from there hit ground targets with divided warheads with nuclear warheads. At the same time, 20-25 minutes are enough for them to fly to the most remote point.