What does a rocket do in space? Scientific discoveries that brought us into space: Rockets. The last stage of a space rocket and a container with scientific equipment

home- Rocket aircraft , moving in space due to the action of jet thrust that occurs when the rocket rejects part of its own mass (working; body). Flight rockets does not require the presence of a surrounding air or gas environment and is possible not only in the atmosphere, but also in a vacuum. In a word denote a wide range of flying devices from firecrackers to.

space launch vehicle Typically, scientific rockets are equipped with instruments for measuring atmospheric pressure

, magnetic field, cosmic radiation and air composition, as well as equipment for transmitting measurement results via radio to the ground. There are rocket models where instruments with data obtained during ascent are lowered to the ground using parachutes.

Rocket meteorological research preceded satellite research, so the first meteorological satellites had the same instruments as meteorological rockets. The rocket was launched for the first time to study the parameters of the air environment on April 11, 1937, but regular rocket launches began in the 1950s, when a series of specialized scientific rockets were created. In the Soviet Union these were meteorological missiles MR-1, M-100, MR-12, MMR-06 and geophysical ones of the "Vertical" type. In modern Russia in September 2007, M-100B missiles were used. Outside Russia, Aerobi, Black Brant, and Skylark missiles were used.

Cosmonautics Creator astronautics , as a science, Hermann Oberth is considered to be the first to prove the physical possibility human body endure the overloads that occur during rocket launch, as well as the state of weightlessness. High speed the outflow of fuel combustion products (often greater than M10), allows the use of rockets in areas where extremely high speeds are required, for example, for launching spacecraft into Earth orbit (see First escape velocity). Maximum speed , moving in space due to the action of jet thrust that occurs when the rocket rejects part of its own mass (working; body). Flight, which can be achieved using

, is calculated using the Tsiolkovsky formula, which describes the velocity increment as the product of the exhaust velocity and the natural logarithm of the ratio of the initial and final mass of the apparatus. Rocket is the only one capable of launching a spacecraft into space. Alternative ways to lift spacecraft into orbit, such as the “space elevator,” are still in the design stage.

IN space the main feature is most clearly manifested rockets- no need for environment or external forces for your movement. This feature, however, requires that all components necessary to generate the reaction force be on board the rockets. So for missiles, using dense components such as liquid oxygen and kerosene as fuel, the ratio of fuel weight to structure weight reaches 20/1. For rockets powered by oxygen and hydrogen, this ratio is smaller - about 10/1. Massive rocket characteristics depend very much on the type used rocket engine and the established limits of design reliability.

Due to the reduction total weight design and fuel burnup, the acceleration of a composite rocket increases over time. It can decrease slightly only at the moment of discarding the spent stages and the start of operation of the engines of the next stage. Such multi-stage rockets designed to launch spacecraft are called launch vehicles.

Used for needs astronautics rockets are called launch vehicles because they carry a payload. Most often, multi-stage ballistic missiles are used as launch vehicles. , moving in space due to the action of jet thrust that occurs when the rocket rejects part of its own mass (working; body). Flight. The launch vehicle launches from the Earth, or, in the case of a long flight, from the orbit of an artificial Earth satellite.

Currently space agencies different countries launch vehicles Atlas V, Ariane 5, Proton, Delta-4, Soyuz-2 and many others are used.

Forces acting on a rocket in flight

The science that studies the forces acting on rockets or other spacecraft is called astrodynamics.

The main forces acting on a rocket in flight:
1. Engine thrust
2. Attraction celestial body
3. When moving in the atmosphere - drag.
4. Lifting force. Usually small, but significant for rocket planes.

Literature

1. Rocket // Cosmonautics: Little Encyclopedia; Chief Editor V. P. Glushko. 2nd edition, additional - Moscow: “ Soviet encyclopedia", 1970 - P. 372
2. Wikipedia

The word cosmos is synonymous with the word Universe. Space is often divided somewhat arbitrarily into near space, which can currently be explored with the help of artificial Earth satellites, spacecraft, interplanetary stations and other means, and distant space - everything else, incommensurably greater. In fact, near space refers to the solar system, and distant space refers to the vast expanses of stars and galaxies.

The literal meaning of the word “cosmonautics”, which is a combination of two Greek words- “swimming in the Universe.” In common usage, this word means a set of various branches of science and technology that provide research and development of outer space and celestial bodies with the help of spacecraft - artificial satellites, automatic stations for various purposes, manned spacecraft.

Cosmonautics, or, as it is sometimes called, astronautics, combines flights into outer space, a set of branches of science and technology that serve for the exploration and use of outer space in the interests of the needs of mankind using various space means. The beginning of the space age of mankind is considered to be October 4, 1957 - the date when the first artificial Earth satellite was launched in the Soviet Union.

The theory of space flight, a long-standing dream of mankind, became a science as a result of the seminal works of the great Russian scientist Konstantin Eduardovich Tsiolkovsky. He studied the basic principles of missile ballistics, proposed a diagram of a liquid rocket engine, and established the laws that determine the reactive force of the engine. Schemes of spacecraft were also proposed and the principles of rocket design, which are now widely used in practice, were given. For a long time, until the moment when ideas, formulas and drawings of enthusiasts and scientists began to turn into objects manufactured “in metal” in design bureaus and factory workshops, the theoretical foundation of astronautics rested on three pillars: 1) the theory of spacecraft motion ; 2) rocket technology; 3) the totality of astronomical knowledge about the Universe. Subsequently, a wide range of new scientific and technical disciplines arose in the depths of astronautics, such as the theory of control systems for space objects, space navigation, the theory of space communication systems and information transmission, space biology and medicine, etc. Now that it is difficult for us to imagine astronautics without these disciplines, it is useful to remember that theoretical basis Cosmonautics were laid down by K. E. Tsiolkovsky at a time when only the first experiments were carried out on the use of radio waves and radio could not be considered a means of communication in space.

Beam signaling has been seriously considered as a means of communication for many years. sunlight, reflected towards the Earth by mirrors located on board the interplanetary spacecraft. Now that we are accustomed to not being surprised by either live television coverage from the surface of the Moon or radio photographs taken near Jupiter or on the surface of Venus, this is hard to believe. Therefore, it can be argued that the theory of space communications, despite all its importance, is still not the main link in the chain of space disciplines. This main link is the theory of the movement of space objects. It is this that can be considered the theory of space flight. Specialists involved in this science themselves call it differently: applied celestial mechanics, celestial ballistics, space ballistics, cosmodynamics, mechanics space flight, theory of motion of artificial celestial bodies. All these names have the same meaning, precisely expressed by the last term. Cosmodynamics, therefore, is part of celestial mechanics - a science that studies the movement of any celestial bodies as natural (stars, the Sun, planets, their satellites, comets, meteoroids, cosmic dust), and artificial (automatic spacecraft and manned spacecraft). But there is something that distinguishes cosmodynamics from celestial mechanics. Cosmodynamics, born in the bosom of celestial mechanics, uses its methods, but does not fit into its traditional framework.

A significant difference between applied celestial mechanics and classical mechanics is that the second does not and cannot deal with the choice of orbits of celestial bodies, while the first deals with the selection from a huge number of possible trajectories for reaching a particular celestial body of a certain trajectory, which takes into account numerous, often conflicting demands. The main requirement is the minimum speed to which the spacecraft accelerates during the initial active phase of the flight and, accordingly, the minimum mass of the launch vehicle or orbital upper stage (when launching from low-Earth orbit). This ensures the maximum payload and therefore the greatest scientific efficiency of the flight. The requirements for ease of control, radio communication conditions (for example, at the moment the station enters the planet during its flyby), conditions for scientific research (landing on the day or night side of the planet), etc. are also taken into account. Cosmodynamics provides space operation designers with methods for optimal transition from one orbit to another, ways to correct the trajectory. In its field of vision is orbital maneuvering, unknown to classical celestial mechanics. Cosmodynamics is the foundation general theory space flight (just as aerodynamics is the foundation of the theory of flight in the atmosphere of airplanes, helicopters, airships and other aircraft). Cosmodynamics shares this role with rocket dynamics - the science of rocket motion. Both sciences, closely intertwined, form the basis of space technology. Both of them are sections of theoretical mechanics, which itself is a separate section of physics. Being an exact science, cosmodynamics uses mathematical research methods and requires a logically coherent system of presentation. It is not for nothing that the foundations of celestial mechanics were developed after the great discoveries of Copernicus, Galileo and Kepler by precisely those scientists who made the greatest contribution to the development of mathematics and mechanics. These were Newton, Euler, Clairaut, d'Alembert, Lagrange, Laplace. And at present, mathematics helps solve problems of celestial ballistics and, in turn, receives an impetus in its development thanks to the tasks that cosmodynamics poses for it.

Classical celestial mechanics was a purely theoretical science. Her conclusions were consistently confirmed by astronomical observation data. Cosmodynamics introduced experiment into celestial mechanics, and celestial mechanics for the first time turned into an experimental science, similar in this respect to, say, such a branch of mechanics as aerodynamics. The involuntarily passive nature of classical celestial mechanics was replaced by the active, offensive spirit of celestial ballistics. Each new achievement in astronautics is at the same time evidence of the effectiveness and accuracy of cosmodynamics methods. Cosmodynamics is divided into two parts: the theory of motion of the center of mass of a spacecraft (theory of space trajectories) and the theory of motion of a spacecraft relative to the center of mass (the theory of “rotational motion”).

Rocket engines

The main and almost the only means of transportation in outer space is the rocket, which was first proposed for this purpose in 1903 by K. E. Tsiolkovsky. The laws of rocket propulsion represent one of the cornerstones of the theory of space flight.

Cosmonautics has a large arsenal of rocket propulsion systems based on the use various types energy. But in all cases, the rocket engine performs the same task: in one way or another it ejects a certain mass from the rocket, the reserve of which (the so-called working fluid) is located inside the rocket. A certain force acts on the ejected mass from the rocket, and according to Newton’s third law of mechanics - the law of equality of action and reaction - the same force, but in the opposite direction, acts from the ejected mass on the rocket. This last force that propels the rocket is called thrust. It is intuitively clear that the thrust force should be greater, the greater the mass per unit time is ejected from the rocket and the greater the speed that can be imparted to the ejected mass.

The simplest diagram of a rocket design:

At this stage of development of science and technology, there are rocket engines based on different operating principles.

Thermochemical rocket engines.

The operating principle of thermochemical (or simply chemical) engines is not complicated: as a result chemical reaction(usually a combustion reaction) a large amount of heat is released and heated to high temperature the reaction products, rapidly expanding, are ejected from the rocket with high exhaust speed. Chemical engines belong to a broader class of thermal (heat exchange) engines in which the working fluid flows out as a result of its expansion through heating. For such engines, the exhaust velocity mainly depends on the temperature of the expanding gases and on their average molecular weight: than higher temperature and the lower the molecular weight, the greater the flow rate. Liquid rocket engines, solid fuel rocket engines, and air-breathing engines operate on this principle.

Nuclear thermal engines.

The principle of operation of these engines is almost no different from the principle of operation of chemical engines. The difference is that the working fluid is heated not due to its own chemical energy, but due to “extraneous” heat released during an intranuclear reaction. Based on this principle, pulsating nuclear thermal engines, nuclear thermal engines based on thermonuclear fusion, and radioactive decay isotopes. However, the danger of radioactive contamination of the atmosphere and the conclusion of an agreement to stop nuclear tests in the atmosphere, in space and under water, led to the cessation of funding for the mentioned projects.

Heat engines with external source energy.

The principle of their operation is based on receiving energy from the outside. Based on this principle, a solar thermal engine is designed, the energy source of which is the Sun. Sun rays concentrated by mirrors are used to directly heat the working fluid.

Electric rocket engines.

This broad class of engines combines Various types engines that are being developed very intensively at present. Acceleration of the working fluid to a certain exhaust velocity is carried out due to electrical energy. Energy is obtained from a nuclear or solar power plant on board spaceship(in principle, even from a chemical battery). The designs of the electric motors being developed are extremely diverse. These include electrothermal engines, electrostatic (ionic) engines, electromagnetic (plasma) engines, electric engines with the intake of working fluid from the upper layers of the atmosphere.

Space rockets

A modern space rocket is a complex structure consisting of hundreds of thousands and millions of parts, each of which plays its intended role. But from the point of view of the mechanics of accelerating a rocket to the required speed, the entire initial mass of the rocket can be divided into two parts: 1) the mass of the working fluid and 2) the final mass remaining after the release of the working fluid. This latter is often called “dry” mass, since the working fluid in most cases is liquid fuel. The “dry” mass (or, if you prefer, the “empty” mass, without the working fluid, of the rocket) consists of the mass of the structure and the mass of the payload. The design should be understood not only as the supporting structure of the rocket, its shell, etc., but also the propulsion system with all its units, the control system, including controls, navigation and communication equipment, etc. - in a word, everything that which ensures normal flight of the rocket. The payload consists of scientific equipment, a radio telemetry system, the body of the spacecraft being launched into orbit, the crew and life support system of the spacecraft, etc. The payload is something without which the rocket can make a normal flight.

The acceleration of the rocket is facilitated by the fact that as the working fluid flows out, the mass of the rocket decreases, due to which, with constant thrust, the reactive acceleration continuously increases. But, unfortunately, the rocket does not consist of only one working fluid. As the working fluid expires, the vacated tanks, excess parts of the shell, etc. begin to burden rocket to the dead load, making it difficult to accelerate. It is advisable at some points to separate these parts from the rocket. A rocket built in this way is called a composite rocket. Often a composite rocket consists of independent rocket stages (thanks to this, various stages can be composed of individual stages) missile systems), connected in series. But parallel connection of steps, side by side, is also possible. Finally, there are projects of composite rockets, in which the last stage goes inside the previous one, which is enclosed inside the previous one, etc.; in this case, the stages have a common engine and are no longer independent rockets. A significant drawback of the latter scheme is that after separation of the spent stage, the jet acceleration sharply increases, since the engine remains the same, the thrust therefore has not changed, and the accelerated mass of the rocket has sharply decreased. This complicates the accuracy of missile guidance and places increased demands on the strength of the structure. When the stages are connected in series, the newly switched on stage has less thrust and the acceleration does not change sharply. While the first stage is operating, we can consider the remaining stages along with the true payload as the first stage payload. After the separation of the first stage, the second stage begins to operate, which, together with subsequent stages and the actual payload, forms an independent rocket (“first subrocket”). For the second stage, all subsequent stages, together with the true payload, play the role of their own payload, etc. Each sub-rocket adds its own ideal speed to the existing speed, and as a result, the final ideal speed of a multi-stage rocket is the sum of the ideal speeds of the individual sub-rocket.

The rocket is a 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 a small part (1.5-2.0%) of the launch mass of the rocket.

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.

Missile configuration options. From left to right:

1. Single stage rocket.
2. Two-stage cross-section rocket.
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 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 in the work of the previous one, being a passive load for it.

With longitudinal separation, the first stage consists of several identical rockets (in practice, from two to eight), 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 separation of all subsequent stages occurs transversely. An example of this approach is the domestic Soyuz launch vehicle.

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 fuel boosters; in the second stage, part of the fuel is contained in the orbiter tanks (the reusable spacecraft itself), and most of it is contained 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 design 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 (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 sections, on 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 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 a high explosive with an electric detonator. When a current pulse is applied to the electric detonator, an explosion occurs that destroys 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, a current pulse is simultaneously applied to the electric detonators of all pyrobolts connecting the separated parts, and the connection is released.

Next, the steps should be spaced a safe distance from each other. (Starting the engine of a higher stage near a lower one can cause burnout of its fuel capacity and an explosion of residual fuel, which will 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 In the void, auxiliary small solid rocket motors 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 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.

Increasing the number of steps gives a 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 steps important There are also reliability issues. Pyrobolts and auxiliary solid propellant rocket motors are disposable elements, the functioning of which cannot be verified before the launch of the rocket. 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.

Cosmic speeds

It is extremely important to note that the speed developed by the rocket (and with it the entire spacecraft) on the active part of the path, that is, on that relatively short section while the rocket engine is running, must be achieved very, very high.

Let's mentally place our rocket in free space and turn on its engine. The engine created thrust, the rocket received some kind of acceleration and began to pick up speed, moving in a straight line (if the thrust force does not change its direction). What speed will the rocket acquire by the time its mass decreases from the initial m 0 to the final value m k? If we assume that the speed w of the outflow of matter from the rocket is constant (this is observed quite accurately in modern rockets), then the rocket will develop a speed v, expressed Tsiolkovsky formula, which determines the speed that an aircraft develops under the influence of the thrust of a rocket engine, unchanged in direction, in the absence of all other forces:

where ln denotes natural and log denotes decimal logarithms

The speed, calculated using the Tsiolkovsky formula, characterizes the energy resources of the rocket. It's called ideal. We see that the ideal speed does not depend on the second mass consumption of the working fluid, but depends only on the exhaust velocity w and on the number z = m 0 /m k, called the mass ratio or the Tsiolkovsky number.

There is a concept of so-called cosmic velocities: first, second and third. The first cosmic velocity is the speed at which a body (spacecraft) launched from the Earth can become its satellite. If we do not take into account the influence of the atmosphere, then directly above sea level the first escape velocity is 7.9 km/s and decreases with increasing distance from the Earth. At an altitude of 200 km from the Earth it is 7.78 km/s. Practically, the first escape velocity is assumed to be 8 km/s.

In order to overcome the gravity of the Earth and turn, for example, into a satellite of the Sun or to reach some other planet in the solar system, a body (spacecraft) launched from the Earth must reach a second escape velocity, taken equal to 11.2 km/s.

A body (spacecraft) must have the third cosmic velocity at the surface of the Earth in the case where it is required that it can overcome the gravity of the Earth and the Sun and leave the Solar system. The third escape velocity is assumed to be 16.7 km/s.

Cosmic velocities are enormous in their significance. They are several tens of times faster than the speed of sound in air. Only from this it is clear what complex tasks are facing in the field of astronautics.

Why escape velocity so huge and why don’t spacecraft fall to Earth? Indeed, it is strange: the Sun, with its enormous gravitational forces, holds the Earth and all the other planets of the solar system near itself, preventing them from flying into outer space. It would seem strange that the Earth holds the Moon near itself. There are gravitational forces between all bodies, but the planets do not fall on the Sun because they are in motion, this is the secret.

Everything falls down to the Earth: raindrops, snowflakes, a stone falling from a mountain, and a cup overturned from a table. And the Moon? It revolves around the Earth. If it were not for the forces of gravity, it would fly off tangentially to the orbit, and if it suddenly stopped, it would fall to Earth. The Moon, due to the gravity of the Earth, deviates from a straight path, all the time as if “falling” to the Earth.

The movement of the Moon occurs along a certain arc, and as long as gravity acts, the Moon will not fall to the Earth. It’s the same with the Earth - if it stopped, it would fall into the Sun, but this will not happen for the same reason. Two types of motion - one under the influence of gravity, the other due to inertia - add up and result in curvilinear motion.

The law of universal gravitation, which keeps the Universe in balance, was discovered by English scientist Isaac Newton. When he published his discovery, people said he had gone crazy. The law of gravity determines not only the movement of the Moon and the Earth, but also all celestial bodies in the solar system, as well as artificial satellites, orbital stations, interplanetary spacecraft.

Kepler's laws

Before considering the orbits of spacecraft, let's consider Kepler's laws that describe them.

Johannes Kepler had a sense of beauty. All his adult life he tried to prove that the solar system is some kind of mystical work of art. At first he tried to connect its structure with the five regular polyhedra of classical ancient Greek geometry. (Regular polyhedron - volumetric figure, all faces of which are equal to each other regular polygons.) In Kepler's time, six planets were known, which were believed to be placed on rotating "crystal spheres". Kepler argued that these spheres are arranged in such a way that regular polyhedra fit exactly between adjacent spheres. Between the two outer spheres - Saturn and Jupiter - he placed a cube inscribed in the outer sphere, into which, in turn, the inner sphere is inscribed; between the spheres of Jupiter and Mars - a tetrahedron (regular tetrahedron), etc. Six spheres of planets, five regular polyhedra inscribed between them - it would seem that perfection itself?

Alas, having compared his model with the observed orbits of the planets, Kepler was forced to admit that the real behavior of celestial bodies does not fit into the harmonious framework he outlined. The only result of Kepler's youthful impulse that survived the centuries was a model of the solar system, made by the scientist himself and presented as a gift to his patron, Duke Frederick von Württemburg. In this beautifully executed metal artifact, all the orbital spheres of the planets and the regular polyhedra inscribed in them are hollow containers that do not communicate with each other, which on holidays were supposed to be filled with various drinks to treat the Duke’s guests.

Only after moving to Prague and becoming an assistant to the famous Danish astronomer Tycho Brahe, Kepler came across ideas that truly immortalized his name in the annals of science. Tycho Brahe collected astronomical observation data throughout his life and accumulated enormous amounts of information about the movements of the planets. After his death they came into the possession of Kepler. These records, by the way, had great commercial value at that time, since they could be used to compile refined astrological horoscopes (today scientists prefer to remain silent about this section of early astronomy).

While processing the results of Tycho Brahe's observations, Kepler encountered a problem that, even with modern computers, might seem intractable to someone, and Kepler had no choice but to carry out all the calculations by hand. Of course, like most astronomers of his time, Kepler was already familiar with the Copernican heliocentric system and knew that the Earth revolves around the Sun, as evidenced by the above-described model of the solar system. But how exactly does the Earth and other planets rotate? Let's imagine the problem as follows: you are on a planet that, firstly, rotates around its axis, and secondly, revolves around the Sun in an orbit unknown to you. Looking into the sky, we see other planets that are also moving in orbits unknown to us. And the task is to determine, based on observations made on our rotating around its axis around the Sun globe, the geometry of orbits and the speed of movement of other planets. This is exactly what Kepler ultimately managed to do, after which, based on the results obtained, he derived his three laws!

The first law describes the geometry of the trajectories of planetary orbits: each planet in the Solar System revolves in an ellipse, at one of the foci of which the Sun is located. From school course geometry - an ellipse is a set of points on a plane, the sum of the distances from which to two fixed points - foci - is equal to a constant. Or in other words - imagine a section of the side surface of a cone by a plane at an angle to its base, not passing through the base - this is also an ellipse. Kepler's first law states that the orbits of the planets are ellipses, with the Sun at one of the foci. The eccentricities (degree of elongation) of the orbits and their distance from the Sun at perihelion (the point closest to the Sun) and apohelia (the most distant point) are different for all planets, but all elliptical orbits have one thing in common - the Sun is located at one of the two foci of the ellipse. After analyzing Tycho Brahe's observational data, Kepler concluded that planetary orbits are a set of nested ellipses. Before him, this simply had not occurred to any astronomer.

The historical significance of Kepler's first law cannot be overestimated. Before him, astronomers believed that the planets moved exclusively in circular orbits, and if this did not fit into the framework of observations, the main circular motion was supplemented by small circles that the planets described around the points of the main circular orbit. This was primarily a philosophical position, a kind of immutable fact, not subject to doubt or verification. Philosophers argued that the heavenly structure, unlike the earthly one, is perfect in its harmony, and since the most perfect of geometric shapes are a circle and a sphere, which means the planets move in a circle. The main thing is that, having gained access to the extensive observational data of Tycho Brahe, Johannes Kepler was able to step over this philosophical prejudice, seeing that it did not correspond to the facts - just as Copernicus dared to remove the Earth from the center of the universe, faced with arguments that contradicted persistent geocentric ideas, which also consisted of the “improper behavior” of planets in orbits.

The second law describes the change in the speed of motion of planets around the Sun: each planet moves in a plane passing through the center of the Sun, and in equal periods of time, the radius vector connecting the Sun and the planet describes equal areas. The farther the elliptical orbit takes a planet from the Sun, the slower the movement; the closer it is to the Sun, the faster the planet moves. Now imagine a pair of line segments connecting two positions of the planet in its orbit with the focus of the ellipse in which the Sun is located. Together with the ellipse segment lying between them, they form a sector, the area of ​​which is precisely the “area that is cut off by a straight line segment.” This is exactly what the second law talks about. How closer planet towards the Sun, the shorter the segments. But in this case, in order for the sector to cover in equal time equal area, the planet must travel a greater distance in its orbit, which means its speed increases.

In the first two laws we're talking about about the specifics of the orbital trajectories of a single planet. Kepler's third law allows us to compare the orbits of planets with each other: the squares of the periods of revolution of the planets around the Sun are related as the cubes of the semi-major axes of the planets' orbits. It says that the farther a planet is from the Sun, the longer it takes to complete a full revolution when moving in orbit and the longer, accordingly, the “year” lasts on this planet. Today we know that this is due to two factors. Firstly, the farther a planet is from the Sun, the longer the perimeter of its orbit. Secondly, as the distance from the Sun increases, the linear speed of the planet’s movement also decreases.

In his laws, Kepler simply stated facts, having studied and generalized the results of observations. If you had asked him what caused the ellipticity of the orbits or the equality of the areas of the sectors, he would not have answered you. This simply followed from his analysis. If you asked him about the orbital motion of planets in other star systems, he also would not have anything to answer you. He would have to start all over again - accumulate observational data, then analyze it and try to identify patterns. That is, he simply would have no reason to believe that another planetary system obeys the same laws as the Solar system.

One of the greatest triumphs of Newton's classical mechanics lies precisely in the fact that it provides a fundamental justification for Kepler's laws and asserts their universality. It turns out that Kepler's laws can be derived from Newton's laws of mechanics, Newton's law of universal gravitation and the law of conservation of angular momentum through rigorous mathematical calculations. And if so, we can be sure that Kepler's laws apply equally to any planetary system anywhere in the Universe. Astronomers searching for new planetary systems in space (and quite a few of them have already been discovered) time after time, as a matter of course, use Kepler’s equations to calculate the parameters of the orbits of distant planets, although they cannot observe them directly.

Kepler's third law played and continues to play an important role in modern cosmology. By observing distant galaxies, astrophysicists detect faint signals emitted by hydrogen atoms orbiting in very distant orbits from the galactic center - much further than stars usually are. Using the Doppler effect in the spectrum of this radiation, scientists determine the rotation speeds of the hydrogen periphery of the galactic disk, and from them the angular speeds of galaxies as a whole. The works of the scientist, who firmly put us on the path to a correct understanding of the structure of our solar system, and today, centuries after his death, play such an important role in the study of the structure of the vast Universe.

Orbits

Of great importance is the calculation of spacecraft flight trajectories, in which the main goal should be pursued - maximum energy savings. When calculating the flight path of a spacecraft, it is necessary to determine the most advantageous time and, if possible, launch location, take into account the aerodynamic effects that arise as a result of the interaction of the device with the Earth’s atmosphere during launch and finish, and much more.

Many modern spacecraft, especially those with a crew, have relatively small onboard rocket engines, the main purpose of which is the necessary correction of the orbit and braking during landing. When calculating the flight path, its changes associated with the adjustment must be taken into account. Most of The trajectory (in fact, the entire trajectory, except for its active part and adjustment periods) is carried out with the engines turned off, but, of course, under the influence of the gravitational fields of celestial bodies.

The trajectory of a spacecraft is called an orbit. During the free flight of a spacecraft, when its onboard jet engines are turned off, movement occurs under the influence of gravitational forces and inertia, and main force is the gravity of the Earth.

If we consider the Earth to be strictly spherical, and the action of the Earth’s gravitational field to be the only force, then the motion of the spacecraft obeys Kepler’s well-known laws: it occurs in a stationary (in absolute space) plane passing through the center of the Earth - the orbital plane; the orbit has the shape of an ellipse or a circle (a special case of an ellipse).

Orbits are characterized by a number of parameters - a system of quantities that determine the orientation of the orbit of a celestial body in space, its size and shape, as well as the position in the orbit of the celestial body at some fixed moment. The unperturbed orbit along which the body moves in accordance with Kepler's laws is determined by:

1. Orbital inclination (i) to the reference plane; can have values ​​from 0° to 180°. The inclination is less than 90° if the body appears to be moving counterclockwise to an observer located at the north ecliptic pole or the north celestial pole, and more than 90° if the body is moving in the opposite direction. When applied to the Solar System, the plane of Earth's orbit (the ecliptic plane) is usually chosen as the reference plane; for artificial satellites of the Earth, the plane of the Earth's equator is usually chosen as the reference plane; for satellites of other planets of the Solar System, the equator plane of the corresponding planet is usually chosen as the reference plane.
2. Ascending Node Longitude (Ω)- one of the basic elements of the orbit, used to mathematically describe the shape of the orbit and its orientation in space. Defines the point at which the orbit intersects the main plane in the direction from south to north. For bodies revolving around the Sun, the main plane is the ecliptic, and the zero point is the First Point of Aries (vernal equinox).
3. Major axle(s) is half the main axis of the ellipse. In astronomy, it characterizes the average distance of a celestial body from the focus.
4. Eccentricity- numerical characteristic of a conic section. Eccentricity is invariant with respect to plane movements and similarity transformations and characterizes the “compression” of the orbit.
5. Periapsis argument- is defined as the angle between the directions from the attracting center to the ascending node of the orbit and to the periapsis (the point of the satellite’s orbit closest to the attracting center), or the angle between the line of nodes and the line of apses. Counted from the attracting center in the direction of the satellite's movement, usually selected within the range of 0°-360°. To determine the ascending and descending node, a certain (so-called base) plane containing the attracting center is selected. The ecliptic plane (the movement of planets, comets, asteroids around the Sun), the equatorial plane of the planet (the movement of satellites around the planet), etc. are usually used as the base plane.
6. Average anomaly for a body moving in an unperturbed orbit - the product of its average motion and the time interval after passing the periapsis. Thus, the average anomaly is the angular distance from the periapsis of a hypothetical body moving with a constant angular velocity equal to the average motion.

There are different types of orbits - equatorial (inclination "i" = 0°), polar (inclination "i" = 90°), sun-synchronous orbits (orbital parameters are such that the satellite passes over any point earth's surface approximately at the same local solar time), low-orbital (altitudes from 160 km to 2000 km), medium-orbital (altitudes from 2000 km to 35786 km), geostationary (altitude 35786 km), high-orbital (altitudes more than 35786 km).

Questions.

1. Based on the law of conservation of momentum, explain why a balloon moves in the opposite direction to the stream of compressed air coming out of it.

2. Give examples jet propulsion tel.

In nature, an example is the reactive movement of plants: the ripened fruits of a crazy cucumber; and animals: squid, octopus, jellyfish, cuttlefish, etc. (animals move by throwing out the water they absorb). In technology, the simplest example of jet propulsion is segner wheel, more complex examples are: the movement of rockets (space, gunpowder, military), water vehicles with a jet engine (hydrocycles, boats, motor ships), air vehicles with an air-jet engine (jet airplanes).

3. What is the purpose of rockets?

Rockets are used in various fields of science and technology: in military affairs, scientific research, astronautics, sports and entertainment.

4. Using Figure 45, list the main parts of any space rocket.

Spacecraft, instrument compartment, oxidizer tank, fuel tank, pumps, combustion chamber, nozzle.

5. Describe the principle of operation of a rocket.

In accordance with the law of conservation of momentum, a rocket flies due to the fact that gases with a certain momentum are pushed out of it at high speed, and the rocket is given an impulse of the same magnitude, but directed in the opposite direction. Gases are ejected through a nozzle in which the fuel burns, reaching high temperatures and pressures. The nozzle receives fuel and oxidizer, which are forced there by pumps.

6. What does the speed of a rocket depend on?

The speed of the rocket depends primarily on the speed of gas flow and the mass of the rocket. The rate of gas flow depends on the type of fuel and the type of oxidizer. The mass of the rocket depends, for example, on what speed they want to impart to it or on how far it should fly.

7. What is the advantage of multi-stage rockets over single-stage ones?

Multistage rockets are capable of reaching higher speeds and flying further than single-stage rockets.

8. How is a spacecraft landed?

The landing of the spacecraft is carried out in such a way that its speed decreases as it approaches the surface. This is achieved using brake system, which can be played by or parachute system braking or deceleration can be carried out using a rocket engine, with the nozzle directed downwards (towards the Earth, Moon, etc.), due to which the speed is reduced.

Exercises.

1. From a boat moving at a speed of 2 m/s, a person throws an oar with a mass of 5 kg at a horizontal speed of 8 m/s opposite to the movement of the boat. At what speed did the boat begin to move after the throw, if its mass together with the mass of the person is 200 kg?

2. What speed will the rocket model get if the mass of its shell is 300 g, the mass of gunpowder in it is 100 g, and gases escape from the nozzle at a speed of 100 m/s? (Consider the gas outflow from the nozzle to be instantaneous).

3. On what equipment and how is the experiment shown in Figure 47 carried out? What physical phenomenon is being demonstrated in this case, what does it consist of, and what physical law underlies this phenomenon?
Note: the rubber tube was positioned vertically until water began to flow through it.

A funnel with a rubber tube attached to it from below with a curved nozzle at the end was attached to the tripod using a holder, and a tray was placed below. Then they began to pour water from the container from above into the funnel, while the water poured from the tube into the tray, and the tube itself shifted from a vertical position. This experiment illustrates reactive motion based on the law of conservation of momentum.

4. Perform the experiment shown in Figure 47. When the rubber tube deviates from the vertical as much as possible, stop pouring water into the funnel. While the water remaining in the tube flows out, observe how it changes: a) the flight distance of the water in the stream (relative to the hole in the glass tube); b) position of the rubber tube. Explain both changes.

a) the flight range of water in the stream will decrease; b) as water flows out, the tube will approach horizontal position. These phenomena are due to the fact that the water pressure in the tube will decrease, and therefore the impulse with which the water is ejected.

Let flights into space have long been a common thing. But do you know everything about space launch vehicles? Let's take it apart piece by piece and see what they consist of and how they work.

Rocket engines

Engines are the most important component launch vehicle. They create the traction force that propels the rocket into space. But when it comes to rocket engines, you shouldn’t remember those that are under the hood of a car or, for example, turning the rotor blades of a helicopter. Rocket engines are completely different.

The operation of rocket engines is based on Newton's third law. The historical formulation of this law says that for any action there is always an equal and opposite reaction, in other words, a reaction. That's why these engines are called jet engines.

During operation, a jet rocket engine ejects a substance (the so-called working fluid) in one direction, while it itself moves in the opposite direction. To understand how this happens, you don't have to fly a rocket yourself. The closest, “earthly” example is the recoil that occurs when firing from firearms. The working fluid here is the bullet and powder gases escaping from the barrel. Another example is an inflated and released balloon. If you don't tie it down, it will fly until the air comes out. The air here is the very working fluid. Simply put, the working fluid in a rocket engine is the combustion products of rocket fuel.

Model of the RD-180 rocket engine

Fuel

Rocket engine fuel is usually two-component and includes a fuel and an oxidizer. The Proton launch vehicle uses heptyl (unsymmetrical dimethylhydrazaine) as fuel and nitrogen tetroxide as an oxidizer. Both components are extremely toxic, but this is a “memory” of the missile’s original combat purpose. Intercontinental ballistic missile The UR-500, the progenitor of the Proton, having a military purpose, had to be in combat readiness for a long time before the launch. And other types of fuel did not allow for long-term storage. The Soyuz-FG and Soyuz-2 rockets use kerosene and liquid oxygen as fuel. The same fuel components are used in the Angara family of launch vehicles, Falcon 9 and Elon Musk's promising Falcon Heavy. The fuel pair of the Japanese H-IIB launch vehicle (H-to-bee) is liquid hydrogen (fuel) and liquid oxygen (oxidizer). As in the rocket of the private aerospace company Blue Origin, used to launch the New Shepard suborbital ship. But these are all liquid rocket engines.

Solid propellant rocket engines are also used, but, as a rule, in the solid propellant stages of multistage rockets, such as the starting accelerator of the Ariane 5 launch vehicle, the second stage of the Antares launch vehicle, and the side boosters of the Space Shuttle.

steps

The payload launched into space is only a small fraction of the rocket's mass. Launch vehicles primarily “transport” themselves, that is, their own structure: fuel tanks and engines, as well as the fuel needed to operate them. Fuel tanks and rocket engines are located in different stages of the rocket and, as soon as they exhaust their fuel, they become unnecessary. In order not to carry extra load, they are separated. In addition to full-fledged stages, external fuel tanks that are not equipped with their own engines are also used. During the flight they are also reset.

First stage of the Proton-M launch vehicle

There are two classical schemes for constructing multi-stage rockets: with transverse and longitudinal separation of stages. In the first case, the stages are placed one above the other and are turned on only after the separation of the previous, lower, stage. In the second case, several identical rocket stages are located around the body of the second stage, which are turned on and dropped simultaneously. In this case, the second stage engine can also operate during start-up. But a combined longitudinal-transverse scheme is also widely used.

Missile layout options

The Rokot light-class launch vehicle, launched in February of this year from the cosmodrome in Plesetsk, is a three-stage rocket with a transverse separation of stages. But the Soyuz-2 launch vehicle, launched from the new Vostochny cosmodrome in April of this year, is a three-stage one with a longitudinal-transverse division.

An interesting design for a two-stage longitudinally separated rocket is the Space Shuttle system. This is where the difference between the American shuttles and the Buran lies. The first stage of the Space Shuttle system is the side solid fuel boosters, the second is the shuttle itself (orbiter) with a detachable external fuel tank, which is shaped like a rocket. During liftoff, both the shuttle and booster engines fire. In the Energia-Buran system, the two-stage super-heavy launch vehicle Energia was an independent element and, in addition to launching the Buran spacecraft into space, could be used for other purposes, for example, to support automatic and manned expeditions to the Moon and Mars.

Acceleration block

It may seem that as soon as the rocket goes into space, the goal is achieved. But it is not always the case. The target orbit of a spacecraft or payload can be much higher than the line from which space begins. For example, the geostationary orbit, which hosts telecommunications satellites, is located at an altitude of 35,786 km above sea level. This is why we need an upper stage, which, in fact, is another stage of the rocket. Space begins already at an altitude of 100 km, where weightlessness begins, which is a serious problem for conventional rocket engines.

One of the main “workhorses” of Russian cosmonautics, the Proton launch vehicle paired with the Breeze-M upper stage ensures the launch of payloads weighing up to 3.3 tons into geostationary orbit. But initially the launch is carried out into a low reference orbit (200 km ). Although the upper stage is called one of the stages of the ship, it differs from the usual stage in its engines.

Proton-M launch vehicle with Breeze-M upper stage in assembly

To move a spacecraft or vehicle into a target orbit or direct it onto an outbound or interplanetary trajectory, the upper stage must be able to perform one or more maneuvers that change the flight speed. And for this you need to turn on the engine every time. Moreover, during periods between maneuvers, the engine is turned off. Thus, the upper stage engine is capable of being switched on and off repeatedly, unlike the engines of other rocket stages. The exceptions are the reusable Falcon 9 and New Shepard, whose first stage engines are used for braking when landing on Earth.

Payload

Rockets exist to launch something into space. In particular, spaceships and spacecraft. In the domestic cosmonautics, these are the Progress transport cargo ships and the Soyuz manned spacecraft sent to the ISS. Of the spacecraft this year, the American Intelsat DLA2 spacecraft and the French Eutelsat 9B spacecraft, the domestic navigation spacecraft Glonass-M No. 53 and, of course, the ExoMars-2016 spacecraft, designed to search for methane in atmosphere of Mars.

The rockets have different capabilities for launching payloads. The payload weight of the light-class Rokot launch vehicle, intended for launching spacecraft into low Earth orbits (200 km), is 1.95 tons. The Proton-M launch vehicle belongs to the heavy class. It launches 22.4 tons into low orbit, 6.15 tons into geostationary orbit, and 3.3 tons into geostationary orbit. Soyuz-2, depending on the modification and the cosmodrome, is capable of delivering from 7.5 to 8.7 t, to geostationary transfer orbit - from 2.8 to 3 t and to geostationary - from 1.3 to 1.5 t. The rocket is designed for launches from all Roscosmos sites: Vostochny, Plesetsk, Baikonur and Kuru, used as part of joint Russian-European project. Used to launch transport and manned spacecraft to the ISS, the Soyuz-FG LV has a payload mass from 7.2 tons (with the Soyuz manned spacecraft) to 7.4 tons (with the Progress cargo spacecraft). Currently, this is the only rocket used to transport cosmonauts and astronauts to the ISS.

The payload is usually located at the very top of the rocket. In order to overcome aerodynamic drag, a spacecraft or ship is placed inside the rocket's head fairing, which is discarded after passing through the dense layers of the atmosphere.

The words of Yuri Gagarin, which went down in history: “I see the Earth... What beauty!” were told to them precisely after the release of the head fairing of the Vostok launch vehicle.

Installation of the head fairing of the Proton-M launch vehicle, payload SC "Express-AT1" and "Express-AT2"

Emergency rescue system

A rocket that launches a spacecraft with a crew into orbit can almost always be distinguished by appearance from the one that launches a cargo ship or spacecraft. To ensure that in the event of an emergency on the launch vehicle the crew of the manned spacecraft remains alive, an emergency rescue system (ESS) is used. Essentially, this is another (albeit small) rocket at the head of the launch vehicle. From the outside the SAS looks like a turret unusual shape on top of the rocket. Its task is to pull out a manned spacecraft in an emergency and take it away from the scene of the accident.

In the event of a rocket explosion at launch or at the beginning of a flight, the main engines of the rescue system tear off the part of the rocket in which the manned spacecraft is located and move it away from the accident site. After which a parachute descent takes place. If the flight proceeds normally, after reaching a safe altitude, the emergency rescue system is separated from the launch vehicle. On high altitudes the role of the SAS is not so important. Here the crew can already escape thanks to the separation of the spacecraft's descent module from the rocket.

Soyuz launch vehicle with SAS at the top of the rocket