Carefully many letters.

A flight prototype of a spacecraft with a nuclear power propulsion system (NPP) in Russia is planned to be created by 2025. The corresponding work is laid down in the draft of the Federal Space Program for 2016–2025 (FKP-25), sent by Roscosmos for approval to the ministries.

Nuclear power systems are considered the main promising sources of energy in space when planning large-scale interplanetary expeditions. Provision of megawatt power in space in the future will allow the nuclear power plant, which is currently being created by the enterprises of Rosatom.

All work on the creation of a nuclear power plant is proceeding in accordance with the planned terms. We can say with a great deal of confidence that the work will be completed within the timeframe stipulated by the target program, ”says Andrey Ivanov, project manager of the communications department of the Rosatom state corporation.

Recently, the project has completed two important milestones: a unique design of the fuel element has been created, which ensures operability in conditions of high temperatures, large temperature gradients, high-dose irradiation. Technological tests of the reactor vessel of the future space power unit have also been successfully completed. As part of these tests, the body was pressurized and 3D measurements were made in the base metal, girth weld, and tapered transition zones.

Operating principle. History of creation.

WITH nuclear reactor there are no fundamental difficulties for space applications. In the period from 1962 to 1993, our country has accumulated rich experience in the production of similar installations. Similar work was carried out in the United States. Since the beginning of the 1960s, several types of electric jet engines have been developed in the world: ionic, stationary plasma, anode layer engine, pulsed plasma engine, magnetoplasma, magnetoplasmodynamic.

Work on the creation of nuclear engines for spacecraft were actively conducted in the USSR and the USA in the last century: the Americans closed the project in 1994, the USSR in 1988. The closure of the works was largely facilitated by the Chernobyl disaster, which negatively tuned public opinion towards the use of nuclear energy. In addition, tests of nuclear installations in space were not always carried out routinely: in 1978, the Soviet satellite "Kosmos-954" entered the atmosphere and collapsed, scattering thousands of radioactive fragments over an area of ​​100 thousand square meters. km in the northwestern regions of Canada. The Soviet Union paid Canada monetary compensation in the amount of more than $ 10 million.

In May 1988, two organizations - the Federation of American Scientists and the Committee of Soviet Scientists for Peace against the Nuclear Threat - made a joint proposal to ban the use of nuclear energy in outer space. That proposal did not receive formal implications, but since then no country has launched spacecraft with nuclear power plants on board.

The great advantages of the project are practically important operational characteristics - a long service life (10 years of operation), a significant overhaul interval and a long operating time with one switch-on.

In 2010, technical proposals for the project were formulated. From this year, the design began.

The nuclear power plant contains three main devices: 1) a reactor plant with a working fluid and auxiliary devices (heat exchanger-recuperator and turbine generator-compressor); 2) an electric rocket propulsion system; 3) refrigerator-radiator.

Reactor.

From a physical point of view, it is a compact gas-cooled fast reactor.
A compound (dioxide or carbonitride) of uranium is used as a fuel, but since the design must be very compact, uranium has a higher enrichment in isotope 235 than in fuel elements on conventional (civil) nuclear power plants possibly above 20%. And their shell is a monocrystalline alloy of refractory metals based on molybdenum.

This fuel will have to operate at very high temperatures. Therefore, it was necessary to select materials that would be able to contain the negative factors associated with temperature, and at the same time allow the fuel to perform its main function - to heat the gas heat carrier, with the help of which electricity will be produced.

Fridge.

Cooling the gas during the operation of a nuclear installation is absolutely essential. How do you release heat in outer space? The only option is cooling by radiation. The heated surface in the void is cooled by emitting electromagnetic waves in a wide range, including visible light. The uniqueness of the project lies in the use of a special coolant - helium-xenon mixture. The installation provides a high efficiency.

Engine.

The principle of operation of the ion engine is as follows. A rarefied plasma is created in the gas discharge chamber with the help of anodes and a cathode block located in a magnetic field. The ions of the working fluid (xenon or other substance) are "drawn out" from it by the emission electrode and are accelerated in the gap between it and the accelerating electrode.

To implement the plan, 17 billion rubles were promised in the period from 2010 to 2018. Of these funds, 7.245 billion rubles were allocated to the state corporation Rosatom for the creation of the reactor itself. Other 3.955 billion - FSUE "Keldysh Center" for the creation of a nuclear - power propulsion plant. Another 5.8 billion rubles - for RSC Energia, where the working appearance of the entire transport and energy module is to be formed in the same time frame.

According to plans, by the end of 2017, the preparation of a nuclear power propulsion system will be carried out to complete the transport and energy module (interplanetary flight module). By the end of 2018, the nuclear power plant will be prepared for flight design tests. The project is financed from the federal budget.

It is no secret that work on the creation of nuclear rocket engines began in the United States and the USSR back in the 60s of the last century. How far have they come? And what problems did you have to face along the way?

Anatoly Koroteev: Indeed, work on the use of nuclear energy in space began and was actively pursued in our country and in the United States in the 1960s and 1970s.

Initially, the task was set to create rocket engines, which, instead of the chemical energy of combustion of fuel and oxidizer, would use the heating of hydrogen to a temperature of about 3000 degrees. But it turned out that such a direct route is still ineffective. We get high thrust for a short time, but at the same time we throw out a jet, which in the event of abnormal operation of the reactor may be radioactively contaminated.

Certain experience was accumulated, but neither we nor the Americans were able to create reliable engines at that time. They worked, but not much, because heating hydrogen to 3000 degrees in a nuclear reactor is a serious task. And besides, there were environmental problems during ground tests of such engines, since radioactive jets were released into the atmosphere. It is no longer a secret that such work was carried out at the Semipalatinsk test site specially prepared for nuclear tests, which remained in Kazakhstan.

That is, two parameters turned out to be critical - the exorbitant temperature and radiation emissions?

Anatoly Koroteev: In general, yes. For these and some other reasons, work in our country and in the United States was stopped or suspended - you can evaluate it in different ways. And it seemed to us unreasonable to renew them in such a, I would say, frontal way, in order to make a nuclear engine with all the already mentioned disadvantages. We have proposed a completely different approach. It differs from the old one in the same way that a hybrid car differs from a conventional one. In a conventional car, the engine turns the wheels, and in hybrid cars, electricity is generated from the engine, and this electricity turns the wheels. That is, a kind of intermediate power plant is being created.

So we have proposed a scheme in which the space reactor does not heat the jet ejected from it, but generates electricity. The hot gas from the reactor turns the turbine, the turbine turns the electric generator and the compressor, which circulates the working fluid in a closed loop. The generator generates electricity for the plasma engine with a specific thrust 20 times higher than that of its chemical counterparts.

A tricky scheme. Essentially, this is a mini-nuclear power plant in space. And what are its advantages over a ramjet nuclear engine?

Anatoly Koroteev: The main thing is that the jet coming out of the new engine will not be radioactive, since a completely different working fluid, which is contained in a closed loop, passes through the reactor.

In addition, with this scheme, we do not need to heat hydrogen to exorbitant values: an inert working fluid circulates in the reactor, which heats up to 1500 degrees. We are seriously simplifying our task. And as a result, we will raise the specific thrust not twice, but 20 times in comparison with chemical engines.

Another thing is also important: there is no need for complex field tests, for which the infrastructure of the former Semipalatinsk test site is needed, in particular, the bench base that remained in the city of Kurchatov.

In our case, all the necessary tests can be carried out on the territory of Russia, without getting involved in long international negotiations on the use of nuclear energy outside their state.

Are similar works being carried out in other countries now?

Anatoly Koroteev: I had a meeting with the deputy head of NASA, we discussed issues related to the return to work on nuclear energy in space, and he said that the Americans are showing great interest in this.

It is quite possible that China can respond with vigorous actions on its part, so work must be done quickly. And not only in order to get ahead of someone by half a step.

We need to work quickly, first of all, so that in the emerging international cooperation, and de facto it is being formed, we look worthy.

I do not exclude the possibility that in the near future an international program for a nuclear space power plant, similar to the program for controlled thermonuclear fusion, is being implemented now.

Liquid rocket engines made it possible for a person to go into space - into near-earth orbits. But the speed of the jet stream in the liquid-propellant engine does not exceed 4.5 km / s, and flights to other planets require tens of kilometers per second. A possible solution is to use the energy of nuclear reactions.

The practical creation of nuclear rocket engines (NRM) was carried out only by the USSR and the USA. In 1955, the United States began implementation of the Rover program to develop a nuclear rocket engine for spaceships... Three years later, in 1958, NASA became involved in the project, which set a specific task for ships with nuclear propulsion - a flight to the Moon and Mars. Since that time, the program has become known as NERVA, which stands for "nuclear engine for installation on missiles."

By the mid-70s, within the framework of this program, it was supposed to design a nuclear propulsion engine with a thrust of about 30 tons (for comparison, a liquid-propellant engine of that time had a characteristic thrust of about 700 tons), but with a gas outflow speed of 8.1 km / s. However, in 1973, the program was closed due to a shift in US interests towards space shuttles.

In the USSR, the design of the first nuclear rocket engines was carried out in the second half of the 50s. At the same time, Soviet designers, instead of creating a full-scale model, began to make separate parts of the NRM. And then these developments were tested in interaction with a specially designed pulsed graphite reactor (IGR).

In the 70s-80s of the last century in KB "Salyut", KB "Khimavtomatiki" and NPO "Luch" were created projects of space nuclear rocket engines RD-0411 and RD-0410 with a thrust of 40 and 3.6 tons, respectively. During the design process, the reactor, cold engine and bench prototype were manufactured for testing.

In July 1961, Soviet academician Andrei Sakharov announced a nuclear explosion project at a meeting of leading nuclear scientists in the Kremlin. The explosion had conventional liquid-propellant rocket engines for take-off, while in space it was supposed to detonate small nuclear charges. The fission products arising from the explosion transferred their impulse to the ship, forcing it to fly. However, on August 5, 1963, a treaty banning nuclear weapons tests in the atmosphere, outer space and under water was signed in Moscow. This was the reason for the closure of the program of nuclear explosions.

It is possible that the development of the NRM was ahead of its time. However, they were not too premature. After all, the preparation of a manned flight to other planets lasts several decades, and propulsion systems for it must be prepared in advance.

Nuclear rocket engine design

Nuclear rocket engine(NRE) - a jet engine in which the energy arising from a nuclear decay or fusion reaction heats the working fluid (most often, hydrogen or ammonia).

There are three types of NRE according to the type of fuel for the reactor:

• solid phase;
• liquid phase;
• gas phase.

The most complete is solid phase engine option. The figure shows a diagram of the simplest NRE with a solid nuclear fuel reactor. The working fluid is located in an external tank. With the help of a pump, it is fed into the engine chamber. In the chamber, the working fluid is sprayed with the help of nozzles and comes into contact with the heat-generating nuclear fuel. As it heats up, it expands and flies out of the chamber through the nozzle at a tremendous speed.

Liquid phase- nuclear fuel in the reactor core of such an engine is in liquid form. The thrust parameters of such engines are higher than those of solid-phase ones due to the higher temperature of the reactor.

V gas phase NRE fuel (for example, uranium) and the working fluid are in a gaseous state (in the form of plasma) and are held in the working area by an electromagnetic field. Uranium plasma heated to tens of thousands of degrees transfers heat to the working medium (for example, hydrogen), which, in turn, being heated to high temperatures, forms a jet stream.

By the type of nuclear reaction, a radioisotope rocket engine, a thermonuclear rocket engine and a nuclear engine itself are distinguished (nuclear fission energy is used).

An interesting option is also a pulsed NRE - it is proposed to use a nuclear charge as a source of energy (fuel). Such installations can be of internal and external types.

The main advantages of NRE are:

• high specific impulse;
• significant energy storage;
• compactness of the propulsion system;
• the possibility of obtaining a very high thrust - tens, hundreds and thousands of tons in a vacuum.

The main disadvantage is the high radiation hazard of the propulsion system:

• fluxes of penetrating radiation (gamma radiation, neutrons) during nuclear reactions;
• carryover of highly radioactive uranium compounds and its alloys;
• the outflow of radioactive gases with a working fluid.

Therefore, starting a nuclear engine is unacceptable for launches from the Earth's surface due to the risk of radioactive contamination.

Found interesting article... In general, atomic spaceships have always interested me. This is the future of astronautics. Extensive work on this topic was carried out in the USSR as well. The article is just about them.

Into space on atomic thrust. Dreams and Reality.

Doctor of physico-mathematical sciences Yu. Ya. Stavisskiy

In 1950, I defended my degree in physics engineering at the Moscow Mechanical Institute (MMI) of the Ministry of Ammunition. Five years earlier, in 1945, the Faculty of Engineering and Physics was formed there, preparing specialists for a new industry, the tasks of which were mainly the production of nuclear weapons. The faculty was unmatched. Along with fundamental physics in the volume of university courses (methods of mathematical physics, theory of relativity, quantum mechanics, electrodynamics, statistical physics and others), we were taught a full range of engineering disciplines: chemistry, metal science, resistance of materials, theory of mechanisms and machines, etc. Created by the outstanding Soviet physicist Alexander Ilyich Leipunsky, the Faculty of Engineering and Physics of MMI grew over time into the Moscow Engineering Physics Institute (MEPhI). Another Faculty of Engineering and Physics, which later also merged into MEPhI, was formed at the Moscow Power Engineering Institute (MEI), but if the MMI focused on fundamental physics, then at the Power Engineering Faculty - on thermal and electrophysics.

We studied quantum mechanics from the book by Dmitry Ivanovich Blokhintsev. Imagine my surprise when, during the distribution, I was sent to work for him. I, an avid experimenter (as a child, dismantled all the clocks in the house), and suddenly I find myself with a famous theorist. I was seized by a slight panic, but upon arrival at the place - "Object B" of the USSR Ministry of Internal Affairs in Obninsk - I immediately realized that I was worried in vain.

By this time, the main subject of "Object B", which until June 1950 was actually headed by A.I. Leipunsky, has already formed. Here they created reactors with expanded reproduction of nuclear fuel - "fast breeders". As director, Blokhintsev initiated the development of a new direction - the creation of nuclear-powered engines for space flights. The mastery of space was an old dream of Dmitry Ivanovich, even in his youth he corresponded and met with K.E. Tsiolkovsky. I think that understanding the gigantic possibilities of nuclear energy, in terms of calorific value millions of times higher than the best chemical fuels, determined life path DI. Blokhintsev.
“You can't see a face face to face” ... In those years we did not understand a lot. Only now, when the opportunity has finally appeared to compare the deeds and fates of outstanding scientists of the Physics and Power Engineering Institute (IPPE) - the former "Object B", renamed on December 31, 1966 - a correct, it seems to me, understanding of the ideas that drove them at that time is taking shape. ... With all the variety of cases that the institute had to deal with, priority scientific directions that turned out to be in the sphere of interests of its leading physicists.

The main interest of AIL (as the institute called Alexander Ilyich Leipunsky behind his back) is the development of global energy based on fast breeder reactors (nuclear reactors that have no restrictions on the resources of nuclear fuel). It is difficult to overestimate the significance of this truly "cosmic" problem, to which he devoted the last quarter of a century of his life. Leipunsky spent a lot of energy on the country's defense, in particular on the creation of atomic engines for submarines and heavy aircraft.

The interests of D.I. Blokhintsev (the nickname "DI" stuck to him) were aimed at solving the problem of using nuclear energy for space flights. Unfortunately, in the late 1950s, he was forced to leave this job and lead the creation of an international scientific center- Joint Institute for Nuclear Research in Dubna. There he was engaged in impulse fast reactors - IBR. This was the last big thing in his life.

One goal, one team

DI. Blokhintsev, who taught at Moscow State University in the late 1940s, noticed there, and then invited to work in Obninsk the young physicist Igor Bondarenko, who literally raved about atomic-powered spaceships. Its first scientific advisor was A.I. Leipunsky, and Igor, naturally, dealt with his subject - fast breeders.

Under D.I. Blokhintsev, a group of scientists formed around Bondarenko, who united to solve the problems of using atomic energy in space. In addition to Igor Ilyich Bondarenko, the group included: Viktor Yakovlevich Pupko, Edwin Alexandrovich Stumbur and the author of these lines. Igor was the main ideologist. Edwin conducted experimental studies of ground-based models of nuclear reactors in space installations. I dealt mainly with “low thrust” rocket engines (thrust in them is created by a kind of accelerator - “ion propulsion device”, which is powered by energy from a space nuclear power plant). We investigated the processes
flowing in ion propellers, on ground stands.

On Victor Pupko (in the future
he became the head of the space technology department of the IPPE) there was a lot of organizational work. Igor Ilyich Bondarenko was an outstanding physicist. He subtly felt the experiment, set up simple, elegant and very effective experiments. I think, like no experimenter, and perhaps even few theoreticians, “felt” fundamental physics. Always responsive, open and benevolent, Igor was truly the soul of the institute. To this day, IPPE has been living with his ideas. Bondarenko lived an unreasonably short life. In 1964, at the age of 38, he died tragically due to a medical error. As if God, seeing how much man had done, decided that it was already too much and ordered: "Enough."

It is impossible not to remember one more unique personality- Vladimir Aleksandrovich Malykh, technologist "from God", modern Leskovsky Lefty. If the “products” of the above-mentioned scientists were mainly ideas and calculated estimates of their reality, then Malykh's works always had a way out “in metal”. His technological sector, which numbered more than two thousand employees during the heyday of IPPE, could do, without exaggeration, everything. Moreover, he himself has always played a key role.

V.A. Malykh started out as a laboratory assistant at a research institute nuclear physics Moscow State University, having three courses in physics at its heart, - the war did not let me finish my studies. In the late 1940s, he managed to create a technology for the manufacture of technical ceramics based on beryllium oxide, a unique material, a dielectric with high thermal conductivity. Before Malykh, many unsuccessfully fought over this problem. And the fuel cell based on serial stainless steel and natural uranium, developed by him for the first nuclear power plant, is a miracle for both modern times... Or the thermo-emission fuel cell of a reactor-electric generator for powering spacecraft, created by Malykh, is a “garland”. Until now, nothing better has appeared in this area. Malykh's creations were not demonstration toys, but elements of nuclear technology. They worked for months and years. Vladimir Aleksandrovich became a doctor of technical sciences, laureate of the Lenin Prize, Hero of Socialist Labor. In 1964, he tragically died from the consequences of a military concussion.

Step by step

S.P. Korolev and D.I. Blokhintsev have long cherished the dream of a manned flight into space. Close working ties have been established between them. But in the early 1950s, in the midst of „ cold war“, The funds were not spared only for military purposes. Rocket technology was considered only as a carrier of nuclear charges, and they did not even think about satellites. Meanwhile, Bondarenko, knowing about recent advances rocket scientists, persistently advocated the creation of an artificial Earth satellite. Subsequently, no one remembered this.

The story of the creation of the rocket, which lifted into space the first cosmonaut of the planet, Yuri Gagarin, is curious. It is associated with the name of Andrei Dmitrievich Sakharov. In the late 1940s, he developed a combined fission-thermonuclear charge - "puff", apparently, regardless of "father hydrogen bomb“Edward Teller, who proposed a similar product called the alarm clock. However, Teller soon realized that the nuclear charge of such a scheme would have a "limited" power, no more than ~ 500 kilotons of tol equivalent. This is not enough for an “absolute” weapon, so the “alarm clock” was abandoned. In the Soviet Union, in 1953, Sakharov's puff RDS-6s was blown up.

After successful tests and the election of Sakharov to the academician, the then head of the Ministry of Medium Machine Building V.A. Malyshev invited him to his place and set the task to determine the parameters of the next generation bomb. Andrei Dmitrievich appreciated (without detailed study) the weight of the new, much more powerful charge. Sakharov's report formed the basis of the decree of the Central Committee of the CPSU and the Council of Ministers of the USSR, which obliged S.P. Korolev to develop a ballistic launch vehicle for this charge. It was this R-7 rocket called Vostok that launched an artificial Earth satellite into orbit in 1957 and a spacecraft with Yuri Gagarin in 1961. It was no longer planned to use it as a carrier of a heavy nuclear charge, since the development thermonuclear weapons went the other way.

At the initial stage of the space nuclear program, the IPPE, together with the design bureau V.N. Chelomeya developed a nuclear cruise missile. This direction did not develop for long and ended with calculations and testing of engine elements created in the department of V.A. Malykha. In fact, it was about a low-flying unmanned aircraft with a ramjet nuclear engine and a nuclear warhead (a kind of nuclear analogue of the "buzzing bug" - the German V-1). The system was launched using conventional rocket boosters. After reaching a given speed, the thrust was created by atmospheric air heated by a chain reaction of fission of beryllium oxide impregnated with enriched uranium.

Generally speaking, the ability of a rocket to perform a particular astronautical task is determined by the speed that it acquires after using the entire stock of the working fluid (fuel and oxidizer). It is calculated by the Tsiolkovsky formula: V = c × lnMn / Mk, where c is the outflow velocity of the working fluid, and Mn and Mk are the initial and final mass of the rocket. In conventional chemical rockets, the flow rate is determined by the temperature in the combustion chamber, the type of fuel and oxidizer, and the molecular weight of the combustion products. For example, the Americans used hydrogen as fuel in the descent vehicle to land astronauts on the moon. The product of its combustion is water, whose molecular weight is relatively low, and the flow rate is 1.3 times higher than when burning kerosene. This is enough for the descent vehicle with the astronauts to reach the surface of the Moon and then return them to the orbit of its artificial satellite. At Korolev, work with hydrogen fuel was suspended due to an accident with fatalities. We did not have time to create a lunar descent vehicle for humans.

One of the ways to significantly increase the rate of expiration is the creation of nuclear thermal missiles. We had ballistic atomic missiles (BAR) with a range of several thousand kilometers (a joint project of OKB-1 and IPPE), while the Americans had similar systems of the Kiwi type. The engines were tested at test sites near Semipalatinsk and in Nevada. Their principle of operation is as follows: hydrogen is heated in a nuclear reactor to high temperatures, passes into an atomic state, and already in this form flows out of the rocket. In this case, the outflow velocity is increased by more than four times in comparison with a chemical hydrogen rocket. The question was to find out to what temperature hydrogen can be heated in a solid fuel cell reactor. Calculations gave about 3000 ° K.

At NII-1, whose scientific director was Mstislav Vsevolodovich Keldysh (then president of the USSR Academy of Sciences), the department of V.M. Ievlev, with the participation of IPPE, was engaged in an absolutely fantastic scheme - a gas-phase reactor in which a chain reaction proceeds in a gas mixture of uranium and hydrogen. From such a reactor, hydrogen flows out ten times faster than from a solid fuel, while uranium is separated and remains in the core. One of the ideas involved the use of centrifugal separation, when a hot gas mixture of uranium and hydrogen is “swirled” by incoming cold hydrogen, as a result of which uranium and hydrogen are separated, like in a centrifuge. Ievlev tried, in fact, to directly reproduce the processes in the combustion chamber of a chemical rocket, using as a source of energy not the heat of combustion of fuel, but a fission chain reaction. This paved the way for the full use of energy intensity. atomic nuclei... But the question of the possibility of the outflow of pure hydrogen (without uranium) from the reactor remained unresolved, not to mention the technical problems associated with the containment of high-temperature gas mixtures at pressures of hundreds of atmospheres.

IPPE's work on ballistic atomic missiles was completed in 1969-1970 with “fire tests” at the Semipalatinsk test site of a prototype nuclear rocket engine with solid fuel cells. It was created by IPPE in cooperation with A.D. Konopatov, Moscow Research Institute-1 and a number of other technology groups. The basis of the engine with a thrust of 3.6 tons was an IR-100 nuclear reactor with fuel cells made of a solid solution of uranium carbide and zirconium carbide. The hydrogen temperature reached 3000 ° K at a reactor power of ~ 170 MW.

Low-thrust nuclear missiles

Until now, we have been talking about rockets with a thrust exceeding their weight, which could be launched from the surface of the Earth. In such systems, an increase in the flow rate makes it possible to reduce the stock of the working fluid, increase the payload, and abandon the multistage system. However, there are ways to achieve practically unlimited flow rates, for example, the acceleration of matter by electromagnetic fields. I have been working in this area in close contact with Igor Bondarenko for almost 15 years.

The acceleration of a rocket with an electric jet engine (EJE) is determined by the ratio of the specific power of the space nuclear power plant (KNPP) installed on them to the outflow rate. In the foreseeable future, the specific capacities of the KNPP, apparently, will not exceed 1 kW / kg. In this case, it is possible to create rockets with low thrust, tens and hundreds of times less than the weight of the rocket, and with a very low consumption of the working fluid. Such a rocket can only start from the orbit of an artificial Earth satellite and, slowly accelerating, reach high speeds.

For flights within the solar system, rockets with an outflow velocity of 50-500 km / s are needed, and for flights to the stars, “photonic rockets” that go beyond our imagination with an outflow speed, equal speed Sveta. In order to carry out a long-range space flight that is at least reasonable in time, unimaginable specific capacities of power plants are required. While it is impossible to even imagine on what physical processes they can be based.

The calculations showed that during the Great Confrontation, when the Earth and Mars are closest to each other, it is possible to fly a nuclear spacecraft with a crew to Mars in one year and return it to the orbit of an artificial Earth satellite. The total weight of such a ship is about 5 tons (including the stock of the working fluid - cesium, equal to 1.6 tons). It is mainly determined by the mass of the 5 MW KNPP, and the jet thrust is determined by a two megawatt beam of cesium ions with an energy of 7 keV *. The spacecraft starts from the orbit of an artificial satellite of the Earth, enters the orbit of the satellite of Mars, and will have to descend to its surface on a device with a hydrogen chemical engine, similar to the American lunar one.

This direction based on technical solutions, possible already today, was devoted to a large cycle of IPPE works.

Ionic movers

In those years, the ways of creating various electrojet propulsion devices for spacecraft, such as "plasma guns", electrostatic accelerators of "dust" or liquid droplets, were discussed. However, none of the ideas had a clear physical basis. The find was surface ionization of cesium.

Back in the 1920s, American physicist Irving Langmuir discovered surface ionization of alkali metals. When a cesium atom evaporates from the surface of a metal (in our case, tungsten), whose work function of electrons is greater than the ionization potential of cesium, it loses a weakly bound electron in almost 100% of cases and turns out to be a singly charged ion. Thus, the surface ionization of cesium on tungsten is the physical process that makes it possible to create an ion propulsion device with almost 100% use of the working fluid and with an energy efficiency close to unity.

Our colleague Stal Yakovlevich Lebedev played an important role in the creation of models of the ion propulsion system of such a scheme. With his iron tenacity and perseverance, he overcame all obstacles. As a result, it was possible to reproduce in the metal a flat three-electrode scheme of the ion propulsion device. The first electrode is a tungsten plate about 10 × 10 cm in size with a potential of +7 kV, the second is a tungsten grid with a potential of -3 kV, and the third is a grid of thoriated tungsten with zero potential. The “molecular gun” produced a beam of cesium vapor, which fell through all the grids onto the surface of the tungsten plate. A balanced and calibrated metal plate, the so-called balance, was used to measure the “force,” that is, the thrust of the ion beam.

The accelerating voltage to the first grid accelerates the cesium ions to 10,000 eV, the decelerating voltage to the second slows them down to 7000 eV. This is the energy with which the ions must leave the propulsion device, which corresponds to an outflow velocity of 100 km / s. But the ion beam, limited by the space charge, cannot “go out into outer space”. The volume charge of ions must be compensated for by electrons in order to form a quasi-neutral plasma, which freely spreads in space and creates a reactive thrust. The third grid (cathode) heated by the current serves as the source of electrons to compensate for the space charge of the ion beam. The second, "blocking" grid prevents electrons from getting from the cathode to the tungsten plate.

The first experience with the ion propulsion model marked the beginning of more than ten years of work. One of the latest models - with a porous tungsten emitter, created in 1965, gave a "thrust" of about 20 g at an ion beam current of 20 A, had a coefficient of energy utilization of about 90% and of matter - 95%.

Direct conversion nuclear heat into electricity

Ways of direct conversion of nuclear fission energy into electrical energy have not yet been found. We still cannot do without an intermediate link - a heat engine. Since its efficiency is always less than unity, the “waste” heat must be disposed of somewhere. On land, in water and in the air, this is no problem. In space, there is only one way - thermal radiation... Thus, the KNPP cannot do without a “cooler-radiator”. The radiation density is proportional to the fourth power of the absolute temperature, therefore the temperature of the radiator-refrigerator should be as high as possible. Then it will be possible to reduce the area of ​​the emitting surface and, accordingly, the mass of the power plant. We had an idea to use the “direct” conversion of nuclear heat into electricity, without a turbine and generator, which seemed more reliable for long-term operation at high temperatures.

From the literature, we knew about the works of A.F. Joffe - the founder Soviet school technical physics, a pioneer in the study of semiconductors in the USSR. Few people now remember about the current sources developed by him, which were used during the Great Patriotic War. Then, more than one partisan detachment had a connection with the mainland thanks to the "kerosene" TEGs - Ioffe's thermoelectric generators. A "crown" of TEGs (it was a set of semiconductor elements) was put on a kerosene lamp, and its wires were connected to radio equipment. The “hot” ends of the elements were heated by the flame of a kerosene lamp, and the “cold” ends were cooled in air. The heat flux, passing through the semiconductor, generated an electromotive force, which was enough for a communication session, and in the intervals between them, the TEG charged the battery. When, ten years after the Victory, we visited the Moscow plant of TEGs, it turned out that they were still finding sales. At that time, many of the villagers had energy-efficient Rodina radios with direct incandescent lamps and battery power. TEGs were often used instead.

The trouble with the kerosene TEG is its low efficiency (only about 3.5%) and low limiting temperature (350 ° K). But the simplicity and reliability of these devices attracted developers. Thus, semiconductor converters developed by the group of I.G. Gverdtsiteli at the Sukhum Physics and Technology Institute, found application in space installations of the Buk type.

At one time A.F. Ioffe proposed another thermionic converter - a diode in vacuum. The principle of its operation is as follows: a heated cathode emits electrons, some of them, overcoming the potential of the anode, do work. Significantly higher efficiency (20-25%) was expected from this device at operating temperature above 1000 ° K. In addition, unlike a semiconductor, a vacuum diode is not afraid of neutron radiation, and it can be combined with nuclear reactor... However, it turned out that it is impossible to implement the idea of ​​a “vacuum” Ioffe converter. As in the ion propulsion device, the vacuum converter needs to get rid of the space charge, but this time not ions, but electrons. A.F. Ioffe proposed to use micron gaps between the cathode and anode in a vacuum converter, which is practically impossible under conditions of high temperatures and thermal deformations. This is where cesium came in handy: one cesium ion, obtained due to surface ionization at the cathode, compensates for the volume charge of about 500 electrons! In essence, a cesium converter is a “reversed” ion propulsion device. The physical processes in them are close.

"Garlands" by V.A. Malykha

One of the results of the IPPE's work on thermionic converters was the creation of V.A. Small and serial production in its department of fuel elements from series-connected thermionic converters - "garlands" for the Topaz reactor. They gave up to 30 V - one hundred times more than single-element converters created by "competing organizations" - the Leningrad group of MB Barabash and later - the Institute of Atomic Energy. This made it possible to “remove” from the reactor tens and hundreds of times more power. However, the reliability of the system, crammed with thousands of thermionic elements, raised concerns. At the same time, steam and gas turbine plants operated without interruptions, so we paid attention to the “machine” conversion of nuclear heat into electricity.

The whole difficulty lay in the resource, because in deep space flights, turbine generators should work for a year, two, or even several years. To reduce wear, the “revolutions” (turbine speed) should be made as low as possible. On the other hand, a turbine works efficiently if the speed of the gas or vapor molecules is close to the speed of its blades. Therefore, we first considered the use of the heaviest - mercury vapor. But we were frightened by the intense radiation-stimulated corrosion of iron and stainless steel, which occurred in a nuclear reactor cooled with mercury. In two weeks, corrosion “ate up” the fuel elements of the Clementine experimental fast reactor in the Argonne Laboratory (USA, 1949) and the BR-2 reactor at the IPPE (USSR, Obninsk, 1956).

Potassium vapor turned out to be tempting. A reactor with potassium boiling in it formed the basis for the power plant of a low-thrust spacecraft that we were developing - potassium steam rotated a turbine generator. This "machine" method of converting heat into electricity made it possible to count on an efficiency of up to 40%, while real thermionic installations gave an efficiency of only about 7%. However, KNPPs with “machine” conversion of nuclear heat into electricity have not been developed. The case ended with the release of a detailed report, in fact - a "physical note" to the technical project of a low-thrust spacecraft for a crewed flight to Mars. The project itself was never developed.

In the future, I think, interest in space flights using nuclear rocket engines simply disappeared. After the death of Sergei Pavlovich Korolev, support for the IPPE work on ion propulsion systems and "machine" nuclear power plants noticeably weakened. OKB-1 was headed by Valentin Petrovich Glushko, who had no interest in daring promising projects. The OKB Energia, which he created, built powerful chemical rockets and the Buran spacecraft that would return to Earth.

"Buk" and "Topaz" on the satellites of the "Cosmos" series

Work on the creation of a KNPP with direct conversion of heat into electricity, now as a power source for powerful radio-technical satellites (space radar stations and TV broadcasters), continued until the start of restructuring. From 1970 to 1988, about 30 radar satellites with Buk nuclear power plants with semiconductor converters and two with Topaz thermal emission plants were launched into space. "Buk", in fact, was a TEG - a semiconductor Ioffe converter, only instead of a kerosene lamp it used a nuclear reactor. It was a fast reactor with a power of up to 100 kW. The full load of highly enriched uranium was about 30 kg. Heat from the core was transferred by liquid metal - eutectic sodium-potassium alloy to semiconductor batteries. Electric power reached 5 kW.

Installation "Buk" under the scientific guidance of the IPPE was developed by experts from OKB-670 MM. Bondaryuk, later - NPO Krasnaya Zvezda (chief designer - GM Gryaznov). The Dnepropetrovsk design bureau Yuzhmash (chief designer - MK Yangel) was instructed to create a launch vehicle for launching the satellite into orbit.

"Buk" working hours - 1-3 months. If the installation failed, the satellite was transferred to a long-term orbit with an altitude of 1000 km. For almost 20 years of launches, there have been three cases of a satellite falling to Earth: two into the ocean and one on land, in Canada, in the vicinity of the Great Slave Lake. Space-954, launched on January 24, 1978, fell there. He worked for 3.5 months. The satellite's uranium elements were completely burned up in the atmosphere. On the ground, only the remains of a beryllium reflector and semiconductor batteries were found. (All of this data is given in the joint report of the US and Canadian atomic commissions on Operation Morning Light.)

A thermal reactor with a power of up to 150 kW was used in the Topaz thermal emission nuclear power plant. The full load of uranium was about 12 kg - significantly less than that of the Buk. The core of the reactor was fuel elements - "garlands", developed and manufactured by Malykh's group. They were a chain of thermoelements: the cathode was a “thimble” of tungsten or molybdenum filled with uranium oxide, and the anode was a thin-walled niobium tube cooled with liquid sodium-potassium. The cathode temperature reached 1650 ° C. The electric power of the installation reached 10 kW.

The first flight prototype, the Kosmos-1818 satellite with the Topaz installation, entered orbit on February 2, 1987 and operated without failure for six months, until the cesium reserves were depleted. The second satellite, Kosmos-1876, was launched a year later. He worked in orbit for almost twice as long. The main developer of "Topaz" was OKB MMZ "Soyuz", headed by S.K. Tumansky (former design bureau of aircraft engine designer A.A.Mikulin).

This was in the late 1950s, when we were working on the ion propulsion system, and he was working on the third stage engine, intended for a rocket that was to fly around the moon and land on it. Memories of the Melnikov laboratory are fresh to this day. It was located in Podlipki (now the town of Korolev), on site No. 3 of OKB-1. A huge workshop with an area of ​​about 3000 m2, lined with dozens of desks with loop oscilloscopes recording on 100 mm roll paper (this was still a bygone era, today one personal computer would be enough). At the front wall of the workshop there is a stand where the combustion chamber of the "lunar" rocket engine is mounted. Oscilloscopes have thousands of wires from sensors for gas velocity, pressure, temperature and other parameters. The day starts at 9.00 with the ignition of the engine. It works for several minutes, then immediately after stopping, the first shift team of mechanics dismantles it, carefully examines and measures the combustion chamber. At the same time, oscilloscope tapes are analyzed and recommendations for design changes are made. The second shift - the designers and workshop workers make the recommended changes. In the third shift, a new combustion chamber and diagnostic system are being installed at the stand. A day later, at exactly 9:00 am, the next session will take place. And so without days off for weeks, months. Over 300 engine options per year!

This is how chemical rocket engines were created, which had to work for only 20-30 minutes. What can we say about the tests and modifications of nuclear power plants - the calculation was that they should work for more than one year. This required a truly gigantic effort.

Sergeev Aleksey, 9 "A" class MOU "Secondary School No. 84"

Scientific consultant: Deputy Director of the non-profit partnership for scientific and innovative activities "Tomsk Atomic Center"

Head:, teacher of physics, MOU "Secondary School No. 84" ZATO Seversk

Introduction

Propulsion systems on board the spacecraft are designed to generate thrust or angular momentum. According to the type of thrust used, the propulsion system is divided into chemical (CRD) and non-chemical (NHRD). RWEs are divided into liquid (LPRE), solid-propellant (solid propellant rocket engines) and combined (KRD). In turn, non-chemical propulsion systems are divided into nuclear (NRE) and electric (ERE). Great scientist Konstantin Eduardovich Tsiolkovsky a century ago created the first model of a propulsion system that worked on solid and liquid fuels. After, in the second half of the 20th century, thousands of flights were carried out using mainly liquid propellant engines and solid propellants.

However, at present, for flights to other planets, not to mention the stars, the use of liquid rocket engines and solid propellants is becoming more and more unprofitable, although many RDs have been developed. Most likely, the capabilities of liquid-propellant rocket engines and solid propellants have completely exhausted themselves. The reason here is that the specific impulse of all chemical taxiways is low and does not exceed 5000 m / s, which requires long-term propulsion operation and, accordingly, large fuel reserves, as is customary in astronautics, to develop sufficiently high speeds. large values the Tsiolkovsky number, i.e., the ratio of the mass of the fueled rocket to the mass of the empty one. So the LV Energia, injecting 100 tons of payload into a low orbit, has a launch mass of about 3000 tons, which gives a value for the Tsiolkovsky number within 30.

For a flight to Mars, for example, the Tsiolkovsky number should be even higher, reaching values ​​from 30 to 50. It is easy to estimate that with a payload of about 1,000 tons, namely, within such limits, the minimum mass required to provide all the necessary crew starting to Mars fluctuates Taking into account the fuel supply for the return flight to the Earth, the initial mass of the spacecraft should be at least 30,000 tons, which is clearly beyond the level of development of modern cosmonautics based on the use of liquid propellant rocket engines and solid propellant rocket engines.

Thus, in order to reach even the nearest planets by manned crews, it is necessary to develop launch vehicles on engines operating on principles different from chemical propulsion systems. The most promising in this regard are electric jet engines (ERE), thermochemical rocket engines and nuclear jet engines (NRE).

1.Basic concepts

A rocket engine is a jet engine that does not use the environment (air, water) for operation. The most widely used are chemical rocket engines. Other types of rocket engines are being developed and tested - electric, nuclear and others. The simplest rocket engines operating on compressed gases are also widely used in space stations and spacecraft. Usually nitrogen is used as a working fluid in them. /1/

Classification of propulsion systems

2. Purpose of rocket engines

According to their purpose, rocket engines are divided into several main types: accelerating (starting), braking, cruising, control and others. Rocket engines are primarily used on rockets (hence the name). In addition, rocket engines are sometimes used in aviation. Rocket engines are the main engines in astronautics.

Military (combat) missiles usually have solid fuel engines. This is due to the fact that such an engine is refueled at the factory and does not require maintenance for the entire storage and service life of the rocket itself. Solid-propellant engines are often used as boosters for space rockets. Especially widely, in this capacity, they are used in the USA, France, Japan and China.

Liquid-propellant rocket engines have higher thrust characteristics than solid-propellant ones. Therefore, they are used to launch space rockets into orbit around the Earth and for interplanetary flights. The main liquid fuels for rockets are kerosene, heptane (dimethylhydrazine) and liquid hydrogen. For these types of fuel, an oxidizing agent (oxygen) is required. Nitric acid and liquefied oxygen are used as oxidizing agents in such engines. Nitric acid is inferior to liquefied oxygen in terms of oxidizing properties, but does not require maintaining a special temperature regime during storage, refueling and use of rockets

Spaceflight engines are different from earthly topics that they, with the smallest possible mass and volume, should generate as much power as possible. In addition, they are subject to such requirements as extremely high efficiency and reliability, significant operating time. According to the type of energy used, the propulsion systems of spacecraft are subdivided into four types: thermochemical, nuclear, electric, solar - sailing. Each of these types has its own advantages and disadvantages and can be used in certain conditions.

Currently, spacecraft, orbital stations and unmanned Earth satellites are launched into space by rockets equipped with powerful thermochemical engines. There are also miniature low-thrust engines. This is a miniature copy of powerful engines. Some of them may fit in the palm of your hand. The thrust of such engines is very small, but it is enough to control the position of the ship in space.

3. Thermochemical rocket engines.

It is known that the engine internal combustion, the furnace of a steam boiler - wherever combustion occurs, atmospheric oxygen takes an active part. There is no air in outer space, and for rocket engines to operate in outer space, it is necessary to have two components - a fuel and an oxidizer.

In liquid thermochemical rocket engines, alcohol, kerosene, gasoline, aniline, hydrazine, dimethylhydrazine, and liquid hydrogen are used as fuel. Liquid oxygen, hydrogen peroxide, and nitric acid are used as oxidizing agents. Perhaps, in the future, liquid fluorine will be used as an oxidizing agent when methods for storing and using such an active chemical are invented.

Fuel and oxidizer for liquid jet engines are stored separately, in special tanks and pumped into the combustion chamber using pumps. When they are combined, a temperature of up to 3000 - 4500 ° C develops in the combustion chamber.

Combustion products, expanding, acquire a speed of 2500 to 4500 m / s. Pushing off from the engine body, they create jet thrust. In this case, the greater the mass and velocity of the gas outflow, the greater the thrust force of the engine.

It is customary to estimate the specific thrust of engines by the amount of thrust created by a unit of mass of fuel burned per second. This value is called the specific impulse of the rocket engine and is measured in seconds (kg of thrust / kg of fuel burned per second). The best solid-propellant rocket engines have a specific impulse of up to 190 s, that is, 1 kg of fuel burning in one second creates a thrust of 190 kg. The hydrogen-oxygen rocket engine has a specific impulse of 350 s. Theoretically, a hydrogen-fluorine engine can develop a specific impulse of more than 400s.

The commonly used scheme of a liquid-propellant rocket engine works as follows. The compressed gas creates the necessary pressure in the cryogenic fuel tanks to prevent the formation of gas bubbles in the pipelines. Pumps supply fuel to rocket motors. Fuel is injected into the combustion chamber through a large number of nozzles. An oxidizer is also injected into the combustion chamber through the nozzles.

In any car, during the combustion of fuel, large heat fluxes are formed that heat the walls of the engine. If you do not cool the walls of the chamber, then it will quickly burn out, no matter what material it is made of. A liquid-propellant jet engine is usually cooled by one of the fuel components. For this, the chamber is made two-wall. The cold fuel component flows in the gap between the walls.

Aluminum "href =" / text / category / alyuminij / "rel =" bookmark "> aluminum, etc. Especially as an additive to conventional fuel, such as hydrogen-oxygen. Such" triple compositions "are able to provide the highest speed possible for chemical fuels outflow - up to 5 km / s. But this is practically the limit of the resources of chemistry. It practically cannot do more. Although liquid-propellant rocket engines still prevail in the proposed description, it must be said that a thermochemical solid-fuel rocket engine was created for the first time in the history of mankind - Solid propellant. Fuel - for example special gunpowder - is located directly in the combustion chamber.Combustion chamber with a jet nozzle, filled with solid fuel - that's the whole structure. solid fuel depends on the purpose of the solid propellant rocket (starting, marching or combined). For solid-propellant missiles used in military affairs, the presence of a launch and sustainer engines is characteristic. The starting solid rocket motor develops a high thrust for a very short time, which is necessary for the missile to leave the launcher and its initial acceleration. The sustainer solid propellant is designed to maintain a constant rocket flight speed in the main (sustainer) section of the flight path. The differences between them are mainly in the design of the combustion chamber and the profile of the combustion surface of the fuel charge, which determine the rate of combustion of the fuel on which the operating time and engine thrust depend. In contrast to such rockets, space launch vehicles for launching Earth satellites, orbital stations and spacecraft, as well as interplanetary stations, operate only in the starting mode from the launch of the rocket to the launch of the object into orbit around the Earth or to an interplanetary trajectory. In general, solid-propellant rocket engines do not have many advantages over liquid-fueled engines: they are easy to manufacture, can be stored for a long time, are always ready for action, and are relatively explosion-proof. But in terms of specific thrust, solid-fuel engines are 10-30% inferior to liquid ones.

4 electric rocket motors

Almost all of the rocket engines discussed above develop tremendous thrust and are designed to launch spacecraft into orbit around the Earth and accelerate them to space speeds for interplanetary flights. It is quite another matter - propulsion systems for spacecraft already launched into orbit or into the interplanetary trajectory. Here, as a rule, low-power motors (several kilowatts or even watts) are needed that can operate for hundreds and thousands of hours and turn on and off repeatedly. They allow you to maintain flight in orbit or along a given trajectory, compensating for the flight resistance created by the upper atmosphere and the solar wind. In electric rocket engines, a working fluid is accelerated to a certain speed by heating it with electrical energy. Electricity comes from solar panels or a nuclear power plant. Methods of heating the working fluid are different, but in reality it is mainly used by electric arc. It has shown itself to be very reliable and withstands a large number of inclusions. Hydrogen is used as a working medium in electric arc engines. Using an electric arc, hydrogen is heated to a very high temperature and it turns into plasma - an electrically neutral mixture of positive ions and electrons. The speed of plasma outflow from the engine reaches 20 km / s. When scientists solve the problem of magnetic isolation of the plasma from the walls of the engine chamber, then it will be possible to significantly increase the temperature of the plasma and bring the flow velocity up to 100 km / s. The first electric rocket engine was developed in the Soviet Union in the years. under the leadership (later he became the creator of engines for Soviet space rockets and an academician) in the famous gas dynamic laboratory (GDL). / 10 /

5.Other types of motors

There are also more exotic projects of nuclear rocket engines, in which the fissile substance is in a liquid, gaseous or even plasma state, however, the implementation of such structures on modern level technique and technology is unrealistic. There are, while at the theoretical or laboratory stage, the following rocket engine projects

Pulsed nuclear rocket engines using the energy of explosions of small nuclear charges;

Thermonuclear rocket engines that can use a hydrogen isotope as fuel. The energy productivity of hydrogen in such a reaction is 6.8 * 1011 KJ / kg, that is, approximately two orders of magnitude higher than the productivity of nuclear fission reactions;

Solar-sailing engines - in which the pressure of sunlight (solar wind) is used, the existence of which was experimentally proved by a Russian physicist back in 1899. By calculation, scientists have established that an apparatus with a mass of 1 ton, equipped with a sail with a diameter of 500 m, can fly from Earth to Mars in about 300 days. However, the efficiency of a solar sail decreases rapidly with distance from the Sun.

6 nuclear rocket motors

One of the main disadvantages of liquid propellant rocket engines is associated with the limited flow rate of gases. In nuclear rocket engines, it seems possible to use the colossal energy released during the decomposition of nuclear "fuel" to heat the working substance. The principle of operation of nuclear rocket engines is almost the same as the principle of operation of thermochemical engines. The difference is that the working fluid is heated not due to its own chemical energy, but due to the "extraneous" energy released during the intranuclear reaction. The working fluid is passed through a nuclear reactor, in which the fission reaction of atomic nuclei (for example, uranium) takes place, and at the same time heats up. Nuclear rocket motors eliminate the need for an oxidizer and therefore only one fluid can be used. As a working fluid, it is advisable to use substances that allow the engine to develop a high thrust force. This condition is most fully satisfied by hydrogen, followed by ammonia, hydrazine and water. The processes in which nuclear energy is released are subdivided into radioactive transformations, fission reactions of heavy nuclei, and the reaction of fusion of light nuclei. Radioisotope transformations are realized in the so-called isotopic energy sources. The specific mass energy (the energy that a substance weighing 1 kg can release) of artificial radioactive isotopes is much higher than that of chemical fuels. So, for 210Ро it is equal to 5 * 10 8 KJ / kg, while for the most energetic chemical fuel (beryllium with oxygen) this value does not exceed 3 * 10 4 KJ / kg. Unfortunately, such engines are used on space launch vehicles not yet rational. The reason for this is the high cost of the isotopic substance and the difficulty of operation. After all, the isotope releases energy constantly, even when it is transported in a special container and when the rocket is parked at the start. More energy efficient fuel is used in nuclear reactors. Thus, the specific mass energy of 235U (the fissile isotope of uranium) is 6.75 * 10 9 kJ / kg, that is, about an order of magnitude higher than that of the isotope 210Ро. These engines can be “turned on” and “turned off”, nuclear fuel (233U, 235U, 238U, 239Pu) is much cheaper than isotopic fuel. In such engines, not only water can be used as a working fluid, but also more efficient working substances - alcohol, ammonia, liquid hydrogen. The specific thrust of the liquid hydrogen engine is 900 s. In the simplest scheme of a nuclear rocket engine with a reactor running on solid nuclear fuel, the working fluid is located in the tank. The pump delivers it to the engine chamber. Spraying with the help of nozzles, the working fluid comes into contact with the heat-generating nuclear fuel, heats up, expands and at high speed is thrown out through the nozzle. Nuclear fuel surpasses any other type of fuel in energy storage. Then a natural question arises - why do installations on this fuel still have a relatively small specific thrust and a large mass? The fact is that the specific thrust of a solid-phase nuclear rocket engine is limited by the temperature of the fissile material, and power plant when working, it emits strong ionizing radiation, which has a harmful effect on living organisms. Biological protection against such radiation is of great importance and is not applicable to space aircraft... The practical development of nuclear rocket engines using solid nuclear fuel began in the mid-50s of the 20th century in the Soviet Union and the United States, almost simultaneously with the construction of the first nuclear power plants... The work was carried out in an atmosphere of increased secrecy, but it is known that such rocket engines have not yet received real use in astronautics. So far, everything has been limited to the use of isotopic sources of electricity of relatively low power on unmanned artificial satellites Earth, interplanetary spacecraft and the world famous Soviet "lunar rover".

7. Nuclear jet engines, the principle of operation, methods of obtaining an impulse in the NRE.

NRE got their name due to the fact that they create thrust through the use of nuclear energy, that is, the energy that is released as a result of nuclear reactions. In a general sense, these reactions mean any changes in the energy state of atomic nuclei, as well as the transformation of some nuclei into others, associated with a rearrangement of the structure of nuclei or a change in the number of elementary particles contained in them - nucleons. Moreover, nuclear reactions, as is known, can occur either spontaneously (that is, spontaneously), or be induced artificially, for example, when some nuclei are bombarded with other (or elementary particles). Nuclear fission and fusion reactions in terms of energy exceed chemical reactions millions and tens of millions of times, respectively. This is due to the fact that the energy chemical bond atoms in molecules are many times less than the nuclear bond energy of nucleons in the nucleus. Nuclear energy in rocket engines can be used in two ways:

1. The released energy is used to heat the working fluid, which then expands in the nozzle, just like in a conventional rocket engine.

2. Nuclear energy is converted into electrical energy and then used to ionize and accelerate the particles of the working fluid.

3. Finally, the impulse is created by the fission products themselves, formed in the process, for example, refractory metals- tungsten, molybdenum) are used to impart special properties to fissile substances.

The fuel elements of the solid-phase reactor are pierced by channels through which the working fluid of the NRE flows, gradually heating up. The channels have a diameter of about 1-3 mm, and their total area is 20-30% of the cross-section of the core. The core is suspended by means of a special grating inside the power case, so that it can expand when the reactor is heated (otherwise it would collapse due to thermal stresses).

The core experiences high mechanical loads associated with the action of significant hydraulic pressure drops (up to several tens of atmospheres) from the flowing working fluid, thermal stresses and vibrations. The increase in the size of the core during heating of the reactor reaches several centimeters. The core and the reflector are placed inside a robust force body that perceives the pressure of the working fluid and the thrust generated by the jet nozzle. The case is closed with a sturdy lid. It accommodates pneumatic, spring or electrical mechanisms for driving the regulating bodies, attachment points for the NRE to the spacecraft, flanges for connecting the NRE with the working fluid supply pipelines. A turbo pump unit can also be located on the cover.

8 - Nozzle,

9 - Expanding nozzle attachment,

10 - Selection of working substance for the turbine,

11 - Power body,

12 - Control drum,

13 - Turbine exhaust (used to control orientation and increase thrust),

14 - Ring of drives of control drums)

At the beginning of 1957, the final direction of the Los Alamos Laboratory's work was determined, and a decision was made to build a graphite nuclear reactor with uranium fuel dispersed in graphite. The Kiwi-A reactor created in this direction was tested in 1959 on July 1.

American solid state nuclear jet engine XE Prime on a test bench (1968)

In addition to the construction of the reactor, the Los Alamos Laboratory was in full swing on the construction of a special test site in Nevada, and also carried out a number of special orders of the US Air Force in related areas (development of individual TNRD units). On behalf of the Los Alamos Laboratory, all special orders for the manufacture of individual units were carried out by the following companies: Aerojet General, a Rocketdyne division of North American Aviation. In the summer of 1958, all control over the implementation of the Rover program was transferred from the US Air Force to the newly organized National Aeronautics and Space Administration (NASA). As a result of a special agreement between the CAE and NASA, in mid-summer 1960, the Office of Space Nuclear Engines was formed under the leadership of G. Finger, who later headed the Rover program.

The results obtained from six "hot tests" of nuclear jet engines were very encouraging, and in early 1961 a Reactor In-Flight Test Report (RJFT) was prepared. Then, in mid-1961, the Nerva project was launched (the use of a nuclear engine for space rockets). Aerojet General was selected as the general contractor and Westinghouse as the subcontractor responsible for the construction of the reactor.

10.2 Work on TNRE in Russia

American "href =" / text / category / amerikanetc / "rel =" bookmark "> Americans, Russian scientists used the most economical and efficient tests of individual fuel elements in research reactors. Salyut ", KB Khimavtomatiki, IAE, NIKIET and NPO Luch (PNITI) to develop various projects of space NRMs and hybrid nuclear power propulsion units. In KB Khimavtomatiki under the scientific leadership of NIITP (the reactor elements were responsible for FEI, IAE, NIKIET, NIITVEL, NPO" Luch ", MAI) were created YARD RD 0411 and nuclear engine of minimum dimension RD 0410 with a thrust of 40 and 3.6 tons, respectively.

As a result, a reactor, a "cold" engine and a bench prototype for testing on gaseous hydrogen were manufactured. In contrast to the American one, with a specific impulse of no more than 8250 m / s, the Soviet TNRE, due to the use of more heat-resistant and advanced fuel elements and a high temperature in the core, had this indicator equal to 9100 m / s and higher. The bench base for testing the TNRE of the joint expedition of NPO "Luch" was located 50 km south-west of the city of Semipalatinsk-21. She started working in 1962. In years. the full-scale fuel elements of the prototypes of the nuclear rocket engine were tested at the test site. In this case, the exhaust gas was fed into a closed discharge system. The Baikal-1 bench complex for full-size tests of nuclear engines is located 65 km south of the city of Semipalatinsk-21. From 1970 to 1988, about 30 "hot starts" of the reactors were carried out. At the same time, the power did not exceed 230 MW with a hydrogen flow rate of up to 16.5 kg / s and its temperature at the reactor outlet of 3100 K. All launches were successful, without accident, and according to plan.

Soviet TYRD RD-0410 - the only working and reliable industrial nuclear rocket engine in the world

Currently, such work at the landfill has been discontinued, although the equipment is maintained in a relatively efficient condition. The bench base of NPO Luch is the only experimental complex in the world where it is possible to carry out tests of elements of NRE reactors without significant financial and time costs. It is possible that the resumption in the United States of work on TNRE for flights to the Moon and Mars within the framework of the Space Research Initiative program with the planned participation of specialists from Russia and Kazakhstan will lead to the resumption of the Semipalatinsk base and the implementation of the “Martian” expedition in the 2020s. ...

Main characteristics

Specific impulse on hydrogen: 910 - 980 sec(theory up to 1000 sec).

· Speed ​​of the outflow of the working fluid (hydrogen): 9100 - 9800 m / sec.

· Achievable thrust: up to hundreds and thousands of tons.

· Maximum operating temperatures: 3000 ° C - 3700 ° C (short-term activation).

· Service life: up to several thousand hours (periodic activation). /5/

11.Device

Device of the Soviet solid-phase nuclear rocket engine RD-0410

1 - line from the working fluid tank

2 - turbo pump unit

3 - regulating drum drive

4 - radiation protection

5 - regulating drum

6 - retarder

7 - fuel assembly

8 - reactor vessel

9 - fire bottom

10 - nozzle cooling line

11- nozzle chamber

12 - nozzle

12.Principle of work

By its principle of operation, the TNRE is a high-temperature reactor-heat exchanger, into which a working fluid (liquid hydrogen) is introduced under pressure, and as it warms up to high temperatures (over 3000 ° C), it is ejected through a cooled nozzle. The regeneration of heat in the nozzle is very beneficial, since it allows the hydrogen to be heated up much faster and by utilizing a significant amount of thermal energy to increase the specific impulse up to 1000 sec (9100- 9800 m / s).

Nuclear rocket engine reactor

MsoNormalTable ">

Working body

Density, g / cm3

Specific thrust (at the indicated temperatures in the heating chamber, ° K), sec

0.071 (liquid)

0.682 (liquid)

1,000 (liquid)

no. dunn

no. dunn

no. dunn

(Note: The pressure in the heating chamber is 45.7 atm, expansion to a pressure of 1 atm with a constant chemical composition of the working fluid) /6/

15.Advantages

The main advantage of TNRE over chemical rocket engines is to obtain a higher specific impulse, significant energy storage, compactness of the system and the possibility of obtaining very high thrust (tens, hundreds and thousands of tons in a vacuum. In general, the specific impulse achieved in a vacuum is greater than that of a spent two-component chemical rocket fuel (kerosene-oxygen, hydrogen-oxygen) by 3-4 times, and when operating at the highest thermal intensity by 4-5 times. space exploration), such engines can be produced in a short time and will have a reasonable cost. additional use perturbation maneuvers using the gravitational field of large planets (Jupiter, Uranus, Saturn, Neptune), the achievable boundaries of studying the solar system are significantly expanding, and the time required to reach distant planets is significantly reduced. In addition, the TNRE can be successfully used for spacecraft operating in low orbits of giant planets using their rarefied atmosphere as a working medium, or for working in their atmosphere. /eight/

16.Disadvantages

The main disadvantage of the TNRE is the presence of a powerful flux of penetrating radiation (gamma radiation, neutrons), as well as the removal of highly radioactive uranium compounds, refractory compounds with induced radiation, and radioactive gases with a working fluid. In this regard, the TNRE is unacceptable for ground launches in order to avoid deterioration ecological situation at the launch site and in the atmosphere. /fourteen/

17. Improving the characteristics of the turbine engine. Hybrid TYRD

Like any rocket engine or any engine in general, a solid-phase nuclear jet engine has significant limitations on the achievable critical characteristics... These restrictions represent the inability of the device (TNRD) to operate in the temperature range exceeding the range of maximum operating temperatures. construction materials engine. To expand the capabilities and significantly increase the main operating parameters of the TNRE, various hybrid schemes can be applied in which the TNRE plays the role of a source of heat and energy and additional physical methods of accelerating the working bodies are used. The most reliable, practically feasible, and having high characteristics in terms of specific impulse and thrust is a hybrid scheme with an additional MHD circuit (magnetohydrodynamic circuit) for accelerating the ionized working fluid (hydrogen and special additives). /13/

18.Radiation hazard from NRE.

A working NRE is a powerful source of radiation - gamma and neutron radiation. Without taking special measures, radiation can cause unacceptable heating of the working fluid and structure in the spacecraft, embrittlement of metal structural materials, destruction of plastic and aging of rubber parts, violation of insulation of electrical cables, and destruction of electronic equipment. Radiation can cause induced (artificial) radioactivity of materials - their activation.

At present, the problem of radiation protection of spacecraft with nuclear propellant engines is considered, in principle, solved. Fundamental issues related to the maintenance of NRE at test benches and launch sites have also been resolved. Although the operating NRE poses a danger to the service personnel, "already a day after the end of the NRE operation, it is possible without any personal protective equipment to be for several tens of minutes at a distance of 50 m from the NRE and even approach it. The simplest means of protection allow the service personnel to enter the working area. YARD soon after testing.

The level of contamination of the launching complexes and the environment, apparently, will not be an obstacle to the use of NRE at the lower stages of space rockets. The problem of radiation hazard for the environment and maintenance personnel is largely mitigated by the fact that the hydrogen used as a working medium is practically not activated when passing through the reactor. Therefore, the jet stream of the NRE is no more dangerous than the jet of the liquid-propellant engine. / 4 /

Conclusion

When considering the prospects for the development and use of NRE in cosmonautics, one should proceed from the achieved and expected characteristics of various types of NRE, from what they can give to cosmonautics, their application, and, finally, from the presence of a close connection between the NRE problem and the problem of energy supply in space and with the issues of energy development. generally.

As mentioned above, of all the possible types of NRE, the most developed are the thermal radioisotope engine and the engine with a solid-phase fission reactor. But if the characteristics of radioisotope NRE does not allow us to hope for their wide application in astronautics (at least in the near future), then the creation of solid-phase NRE opens up great prospects for astronautics.

For example, an apparatus with an initial mass of 40,000 tons (that is, approximately 10 times greater than that of the largest modern launch vehicles) has been proposed, with 1/10 of this mass being the payload, and 2/3 by nuclear charges ... If you detonate one charge every 3 seconds, then their supply will be enough for 10 days of continuous operation of the NRM. During this time, the device will accelerate to a speed of 10,000 km / s and in the future, in 130 years, it can reach the star Alpha Centauri.

Nuclear power plants have unique characteristics, which include practically unlimited energy consumption, independence of operation from the environment, and resistance to external influences (space radiation, meteorite damage, high and low temperatures etc.). However, the maximum power of nuclear radioisotope installations is limited to the order of several hundred watts. This limitation does not exist for nuclear reactor power plants, which predetermines the profitability of their use during long-term flights of heavy spacecraft in near-earth space, during flights to distant planets of the solar system and in other cases.

The advantages of solid-phase and other NRE with fission reactors are most fully revealed in the study of such complex space programs as manned flights to the planets of the solar system (for example, during an expedition to Mars). In this case, an increase in the specific impulse of the RD makes it possible to solve qualitatively new problems. All these problems are greatly facilitated by using a solid-phase NRE with a specific impulse twice that of modern liquid-propellant rocket engines. In this case, it also becomes possible to significantly reduce flight times.

Most likely, in the near future solid-phase NRE will become one of the most widespread RDs. Solid-phase NRM can be used as vehicles for long-distance flights, for example, to planets such as Neptune, Pluto, and even fly out of the Solar System. However, for flights to the stars, the NRM based on the principles of fission is not suitable. In this case, promising are NRE or, more precisely, thermonuclear jet engines (TJE) operating on the principle of fusion reactions and photonic jet engines (FRD), the sources of impulse in which are the reaction of annihilation of matter and antimatter. However, most likely humanity will use a different, different from jet, method of travel to travel in interstellar space.

In conclusion, I will give a paraphrase of Einstein's famous phrase - in order to travel to the stars, humanity must come up with something that would be comparable in complexity and perception to a nuclear reactor for a Neanderthal!

LITERATURE

Sources:

1. "Rockets and people. Book 4 Moon Race" -M: Knowledge, 1999.
2.http: // www. lpre. de / energomash / index. htm
3. Pervushin "Battle for the stars. Cosmic confrontation" -M: knowledge, 1998.
4. L. Gilberg "Conquest of the sky" - M: Knowledge, 1994.
5.http: // epizodsspace. ***** / bibl / molodtsov
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7. "Engine", "Gas-phase nuclear engines for spacecraft",

No. 6, 1999
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8.http: // www. lpre. de / energomash / index. htm
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10., Chekalin transport of the future.

Moscow: Knowledge, 1983.

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Knowledge, 1988.

12. Gubanov B. "Energy - Buran" - a step into the future // Science and life.-

13.Gatland K. Space technology.- Moscow: Mir, 1986.

14., Sergeiuk and commerce. - M .: APN, 1989.

15. USSR in space. 2005.-M .: APN, 1989.

16. On the way to deep space // Energy. - 1985. - No. 6.

APPLICATION

Main characteristics of solid-phase nuclear jet engines

Manufacturer country	Engine	Thrust in vacuum, kN	Specific impulse, sec		Project work, year
	NERVA / Lox Mixed Cycle