The idea of ​​throwing atomic bombs behind the stern turned out to be too brutal, but the amount of energy that the nuclear fission reaction produces, not to mention fusion, is extremely attractive for astronautics. Therefore, many non-pulse systems were created that eliminated the hassle of storing hundreds of nuclear bombs on board and cyclopean shock absorbers. We'll talk about them today.

Nuclear physics at your fingertips

What is a nuclear reaction? To explain it very simply, the picture will be something like this. From the school curriculum we remember that matter consists of molecules, molecules are made of atoms, and atoms are made of protons, electrons and neutrons (there are lower levels, but this is enough for us). Some heavy atoms have an interesting property - if they are hit by a neutron, they decay into lighter atoms and release several neutrons. If these released neutrons hit other heavy atoms nearby, the decay will repeat, and we will get a nuclear chain reaction. The movement of neutrons at high speed means that this movement turns into heat when the neutrons slow down. Therefore, a nuclear reactor is a very powerful heater. They can boil water, send the resulting steam to a turbine, and get a nuclear power plant. Or you can heat hydrogen and throw it outside, creating a nuclear jet engine. From this idea the first engines were born - NERVA and RD-0410.

NERVA

Project history

The formal authorship (patent) for the invention of the atomic rocket engine belongs to Richard Feynman, according to his memoirs “You're Surely Joking, Mr. Feynman.” The book, by the way, is highly recommended reading. Los Alamos Laboratory began developing nuclear rocket engines in 1952. In 1955 the Rover project was started. At the first stage of the project, KIWI, 8 experimental reactors were built and from 1959 to 1964, the purging of working fluid through the reactor core was studied. For time reference, the Orion project existed from 1958 to 1965. Rover had phases two and three exploring higher power reactors, but NERVA was based on KIWI due to plans for the first test launch in space in 1964 - there was no time to develop more advanced options. The deadlines gradually moved forward and the first ground launch of the NERVA NRX/EST engine (EST - Engine System Test - test motor system) took place in 1966. The engine operated successfully for two hours, of which 28 minutes were at full thrust. The second NERVA XE engine was started 28 times and ran for a total of 115 minutes. The engine was deemed suitable for space applications, and the test bench was ready to test the newly assembled engines. It seemed that NERVA had a bright future ahead of it - a flight to Mars in 1978, a permanent base on the Moon in 1981, orbital tugs. But the success of the project caused panic in Congress - the lunar program turned out to be very expensive for the United States, the Mars program would be even more expensive. In 1969 and 1970, space funding was seriously reduced - Apollos 18, 19 and 20 were cancelled, and no one would allocate huge amounts of money for the Mars program. As a result, work on the project was carried out without serious funding and it was closed in 1972.

Design

Hydrogen from the tank entered the reactor, was heated there, and was thrown out, creating jet thrust. Hydrogen was chosen as the working fluid because it has light atoms and is easier to accelerate to high speed. The higher the jet exhaust speed, the more efficient the rocket engine.
A neutron reflector was used to ensure that neutrons were returned back to the reactor to maintain a nuclear chain reaction.
Control rods were used to control the reactor. Each such rod consisted of two halves - a reflector and a neutron absorber. When the rod was turned by the neutron reflector, their flow in the reactor increased and the reactor increased heat transfer. When the rod was turned by the neutron absorber, their flow in the reactor decreased, and the reactor reduced heat transfer.
Hydrogen was also used to cool the nozzle, and warm hydrogen from the nozzle cooling system rotated the turbopump to supply more hydrogen.

The engine is running. Hydrogen was specially ignited at the exit of the nozzle in order to avoid the threat of explosion; there would be no combustion in space.

The NERVA engine produced 34 tons of thrust, about one and a half times less than the J-2 engine that powered the second and third stages of the Saturn V rocket. The specific impulse was 800-900 seconds, which was twice as high as the best engines using the oxygen-hydrogen fuel pair, but less than the electric propulsion system or the Orion engine.

A little about security

A nuclear reactor that has just been assembled and not started up, with new fuel assemblies that have not yet been used, is quite clean. Uranium is poisonous, so you need to wear gloves, but nothing more. No remote manipulators, lead walls or anything else is needed. All radiating dirt appears after the reactor is started due to scattering neutrons, “spoiling” the atoms of the vessel, coolant, etc. Therefore, in the event of a rocket accident with such an engine, radiation contamination of the atmosphere and surface would be small, and, of course, it would be much less than the normal launch of Orion. In the event of a successful launch, contamination would be minimal or absent altogether, because the engine would have to be launched in the upper layers of the atmosphere or already in space.

RD-0410

The Soviet RD-0410 engine has a similar history. The idea of ​​the engine was born in the late 40s among the pioneers of rocket and nuclear technology. As with the Rover project, the original idea was a nuclear-powered air-breathing engine for the first stage of a ballistic missile, then development moved into the space industry. The RD-0410 was developed more slowly; domestic developers were carried away by the idea of ​​a gas-phase nuclear propulsion engine (more on this below). The project began in 1966 and continued until the mid-80s. The target for the engine was the Mars 94 mission, a manned flight to Mars in 1994.
The RD-0410 design is similar to NERVA - hydrogen passes through the nozzle and reflectors, cooling them, is supplied to the reactor core, heated there and released.
According to its characteristics, RD-0410 was better than NERVA - the temperature of the reactor core was 3000 K instead of 2000 K for NERVA, and the specific impulse exceeded 900 s. RD-0410 was lighter and more compact than NERVA and developed ten times less thrust.

Engine tests. The side torch on the lower left ignites the hydrogen to prevent an explosion.

Development of solid-phase nuclear propulsion engines

We remember that the higher the temperature in the reactor, the greater the flow rate of the working fluid and the higher the specific impulse of the engine. What prevents you from increasing the temperature in NERVA or RD-0410? The fact is that in both engines the fuel elements are in a solid state. If you increase the temperature, they will melt and fly out along with the hydrogen. Therefore, for higher temperatures it is necessary to come up with some other way to carry out a nuclear chain reaction.

Nuclear fuel salt engine

In nuclear physics there is such a thing as critical mass. Remember the nuclear chain reaction at the beginning of the post. If fissile atoms are very close to each other (for example, they were compressed by pressure from a special explosion), then an atomic explosion will result - a lot of heat in a very short time. If the atoms are not compressed so tightly, but the flow of new neutrons from fission increases, a thermal explosion will result. A conventional reactor would fail under such conditions. Now imagine that we take an aqueous solution of fissile material (for example, uranium salts) and feed them continuously into the combustion chamber, providing there a mass greater than the critical one. The result is a continuously burning nuclear “candle”, the heat from which accelerates the reacted nuclear fuel and water.

The idea was proposed in 1991 by Robert Zubrin and, according to various estimates, promises a specific impulse of 1300 to 6700 s with a thrust measured in tons. Unfortunately, such a scheme also has disadvantages:

• Complexity of fuel storage - chain reaction in the tank must be avoided by placing the fuel in, for example, thin tubes from a neutron absorber, so the tanks will be complex, heavy and expensive.


• The high consumption of nuclear fuel is due to the fact that the efficiency of the reaction (the number of decayed/number of atoms spent) will be very low. Even in an atomic bomb, the fissile material does not “burn” completely; immediately, most of the valuable nuclear fuel will be wasted.


• Ground tests are practically impossible - the exhaust of such an engine will be very dirty, dirtier even than the Orion.


• There are some questions about controlling the nuclear reaction - it is not a fact that a scheme that is simple in verbal description will be easy to technically implement.

Gas-phase nuclear propulsion engines

Next idea: what if we create a working fluid vortex, in the center of which a nuclear reaction will take place? In this case high temperature the active zone will not reach the walls, being absorbed by the working fluid, and it can be raised to tens of thousands of degrees. This is how the idea of ​​an open-cycle gas-phase nuclear propulsion engine was born:

The gas-phase nuclear propulsion engine promises a specific impulse of up to 3000-5000 seconds. In the USSR, a project of a gas-phase nuclear propulsion engine (RD-600) was started, but it did not even reach the mock-up stage.
"Open cycle" means that nuclear fuel will be released outside, which, of course, reduces efficiency. Therefore, the following idea was invented, dialectically returning to solid-phase NREs - let's surround the nuclear reaction region with a sufficiently heat-resistant substance that will transmit radiated heat. Quartz was proposed as such a substance, because at tens of thousands of degrees, heat is transferred by radiation and the container material must be transparent. The result is a gas-phase closed-cycle nuclear propulsion engine, or a “nuclear light bulb”:

In this case, the limit on the core temperature will be the thermal strength of the “light bulb” shell. The melting point of quartz is 1700 degrees Celsius, with active cooling the temperature can be increased, but, in any case, the specific impulse will be lower than the open circuit (1300-1500 s), but nuclear fuel will be consumed more economically, and the exhaust will be cleaner.

Alternative projects

In addition to the development of solid-phase nuclear propulsion engines, there are also original projects.

Fissile engine

The idea of ​​this engine is that there is no working fluid - it is the ejected spent nuclear fuel. In the first case, subcritical disks are made from fissile materials, which do not start a chain reaction on their own. But if the disk is placed in a reactor zone with neutron reflectors, it will start chain reaction. And the rotation of the disk and the absence of a working fluid will lead to the fact that the decayed high-energy atoms will fly away into the nozzle, generating thrust, and the undecayed atoms will remain on the disk and will get a chance at the next revolution of the disk:

Even more interesting idea consists of creating a dusty plasma (remember on the ISS) from fissile materials, in which the decay products of nuclear fuel nanoparticles are ionized electric field and are thrown out, creating thrust:

They promise a fantastic specific impulse of 1,000,000 seconds. Enthusiasm is dampened by the fact that the development is at the level of theoretical research.

Nuclear fusion engines

In an even more distant future, the creation of nuclear fusion engines. Unlike nuclear decay reactions, where nuclear reactors were created almost simultaneously with the bomb, thermonuclear reactors have not yet moved from “tomorrow” to “today” and fusion reactions can only be used in the “Orion” style - throwing thermonuclear bombs.

Nuclear photon rocket

Theoretically, it is possible to heat the core to such an extent that thrust can be created by reflecting photons. Despite the absence of technical limitations, such engines at the current level of technology are unprofitable - the thrust will be too low.

Radioisotope rocket

A rocket that heats the working fluid from an RTG will be fully functional. But an RTG generates relatively little heat, so such an engine will be very inefficient, although very simple.

Conclusion

At the current level of technology, it is possible to assemble a solid-state nuclear propulsion engine in the style of NERVA or RD-0410 - the technologies have been mastered. But such an engine will lose to the “nuclear reactor + electric propulsion” combination in terms of specific impulse, while winning in terms of thrust. But more advanced options are still only on paper. Therefore, I personally think the “reactor + electric propulsion” combination is more promising.

Sources of information

The main source of information is the English Wikipedia and the resources listed there as links. Paradoxically, there are interesting articles on NRE on Tradition - solid-phase NRE and gas-phase NRE. Article about engines on

A nuclear rocket engine is a rocket engine whose operating principle is based on a nuclear reaction or radioactive decay, which releases energy that heats the working fluid, which can be reaction products or some other substance, such as hydrogen. There are several types of rocket engines that use the principle of operation described above: nuclear, radioisotope, thermonuclear. Using nuclear rocket engines, it is possible to obtain specific impulse values ​​significantly higher than those that can be achieved by chemical rocket engines. High value specific impulse is explained by the high speed of outflow of the working fluid - about 8-50 km/s. The thrust force of a nuclear engine is comparable to that of chemical engines, which will make it possible in the future to replace all chemical engines with nuclear ones.

The main obstacle on the way complete replacement is radioactive contamination environment, which is caused by nuclear rocket engines.

They are divided into two types - solid and gas phase. In the first type of engines, fissile material is placed in rod assemblies with a developed surface. This makes it possible to effectively heat a gaseous working fluid, usually hydrogen acts as a working fluid. The exhaust speed is limited by the maximum temperature of the working fluid, which, in turn, directly depends on the maximum permissible temperature of the structural elements, and it does not exceed 3000 K. In gas-phase nuclear rocket engines, the fissile substance is in a gaseous state. Its retention in the working area is carried out through the influence of an electromagnetic field. For this type of nuclear rocket engines, the structural elements are not a limiting factor, so the exhaust speed of the working fluid can exceed 30 km/s. They can be used as first stage engines, despite the leakage of fissile material.

In the 70s XX century In the USA and the Soviet Union, nuclear rocket engines with fissile matter in the solid phase were actively tested. In the United States, a program was being developed to create an experimental nuclear rocket engine as part of the NERVA program.

The Americans developed a graphite reactor cooled by liquid hydrogen, which was heated, evaporated and ejected through a rocket nozzle. The choice of graphite was due to its temperature resistance. According to this project, the specific impulse of the resulting engine should have been twice as high as the corresponding figure characteristic of chemical engines, with a thrust of 1100 kN. The Nerva reactor was supposed to work as part of the third stage of the Saturn V launch vehicle, but due to the closure of the lunar program and the lack of other tasks for rocket engines of this class, the reactor was never tested in practice.

A gas-phase nuclear rocket engine is currently in the theoretical development stage. A gas-phase nuclear engine involves using plutonium, whose slow-moving gas stream is surrounded by a faster flow of cooling hydrogen. On orbital space stations MIR and ISS conducted experiments that could give impetus to the further development of gas-phase engines.

Today we can say that Russia has slightly “frozen” its research in the field of nuclear propulsion systems. The work of Russian scientists is more focused on the development and improvement of basic components and assemblies of nuclear power plants, as well as their unification. The priority direction for further research in this area is the creation of nuclear power propulsion systems capable of operating in two modes. The first is the nuclear rocket engine mode, and the second is the installation mode of generating electricity to power the equipment installed on board the spacecraft.

Late last year, the Russian Strategic Missile Forces tested a completely new weapon, the existence of which was previously considered impossible. The nuclear-powered cruise missile, which military experts designate 9M730, is exactly the new weapon that President Putin spoke about in his Address to the Federal Assembly. The missile test was allegedly carried out at the Novaya Zemlya test site, approximately at the end of autumn 2017, but the exact data will not be declassified soon. The rocket developer is also presumably the Novator Experimental Design Bureau (Ekaterinburg). According to competent sources, the missile hit the target in normal mode and the tests were considered completely successful. Further, alleged photographs of the launch (above) of a new rocket with a nuclear power plant and even indirect confirmation related to the presence at the expected time of testing in the immediate vicinity of the test site of the Il-976 LII Gromov “flying laboratory” with Rosatom marks appeared in the media. However, even more questions arose. Is the declared ability of the missile to fly at an unlimited range realistic and how is it achieved?

Characteristics of a cruise missile with a nuclear power plant

The characteristics of a cruise missile with nuclear weapons, which appeared in the media immediately after Vladimir Putin’s speech, may differ from the real ones, which will be known later. To date, the following data on the size and performance characteristics of the rocket have become public:

Length
- home page- at least 12 meters,
- marching- at least 9 meters,

Rocket body diameter- about 1 meter,
Case width- about 1.5 meters,
Tail height- 3.6 - 3.8 meters

The operating principle of a Russian nuclear-powered cruise missile

The development of nuclear-powered missiles was carried out by several countries at once, and development began back in the distant 1960s. The designs proposed by the engineers differed only in details; the principle of operation can be described in a simplified manner as follows: the nuclear reactor heats the mixture entering special containers (various options, from ammonia to hydrogen) and then releases it through nozzles under high pressure. However, the version of the cruise missile that he spoke about Russian President, does not fit any of the examples of designs developed previously.

The fact is that, according to Putin, the missile has an almost unlimited flight range. This, of course, cannot be understood to mean that the missile can fly for years, but it can be regarded as a direct indication that its flight range is many times greater than the flight range of modern cruise missiles. The second point, which cannot be ignored, is also related to the declared unlimited flight range and, accordingly, the operation of the cruise missile’s power unit. For example, a heterogeneous thermal neutron reactor, tested in the RD-0410 engine, which was developed by Kurchatov, Keldysh and Korolev, had a testing life of only 1 hour, and in this case there cannot be an unlimited flight range of such a nuclear-powered cruise missile. speech.

All this suggests that Russian scientists have proposed a completely new, previously unconsidered concept of the structure, in which a substance that has a much economical resource of consumption over long distances is used for heating and subsequent ejection from the nozzle. As an example, this could be a nuclear air-breathing engine (NARE) of a completely new type, in which the working mass is atmospheric air, pumped into the working containers by compressors, heated by a nuclear installation and then ejected through the nozzles.

It is also worth noting that the cruise missile with a nuclear power unit announced by Vladimir Putin can fly around zones active action air and missile defense systems, as well as keep the path to the target at low and ultra-low altitudes. This is only possible by equipping the missile with terrain-following systems that are resistant to interference created by enemy electronic warfare systems.

Skeptics argue that the creation of a nuclear engine is not a significant progress in the field of science and technology, but only a “modernization of a steam boiler”, where instead of coal and firewood, uranium acts as fuel, and hydrogen acts as a working fluid. Is the NRE (nuclear jet engine) so hopeless? Let's try to figure it out.

First rockets

All the achievements of mankind in the exploration of near-Earth space can be safely attributed to chemical jet engines. The operation of such power units is based on energy conversion chemical reaction burning fuel in an oxidizer into the kinetic energy of the jet stream, and, consequently, the rocket. The fuel used is kerosene, liquid hydrogen, heptane (for liquid propellant rocket engines (LPRE)) and a polymerized mixture of ammonium perchlorate, aluminum and iron oxide (for solid propellant rocket engines (SRRE)).

It is common knowledge that the first rockets used for fireworks appeared in China in the second century BC. They rose into the sky thanks to the energy of powder gases. The theoretical research of the German gunsmith Konrad Haas (1556), Polish general Kazimir Semenovich (1650), and Russian Lieutenant General Alexander Zasyadko made a significant contribution to the development of rocket technology.

The American scientist Robert Goddard received a patent for the invention of the first liquid-propellant rocket. His apparatus, weighing 5 kg and about 3 m long, running on gasoline and liquid oxygen, took 2.5 s in 1926. flew 56 meters.

Chasing speed

Serious experimental work on the creation of serial chemical jet engines started in the 30s of the last century. In the Soviet Union, V. P. Glushko and F. A. Tsander are rightfully considered the pioneers of rocket engine construction. With their participation, the RD-107 and RD-108 power units were developed, which ensured the USSR's primacy in space exploration and laid the foundation for Russia's future leadership in the field of manned space exploration.

During the modernization of the liquid-turbine engine, it became clear that the theoretical maximum speed of the jet stream could not exceed 5 km/s. This may be enough to study near-Earth space, but flights to other planets, and even more so to the stars, will remain a pipe dream for humanity. As a result, already in the middle of the last century, projects for alternative (non-chemical) rocket engines began to appear. The most popular and promising installations were those using the energy of nuclear reactions. The first experimental samples of nuclear space engines (NRE) in the Soviet Union and the USA passed test tests back in 1970. However, after the Chernobyl disaster, under public pressure, work in this area was suspended (in the USSR in 1988, in the USA - since 1994).

The operation of nuclear power plants is based on the same principles as thermochemical ones. The only difference is that the heating of the working fluid is carried out by the energy of decay or fusion of nuclear fuel. The energy efficiency of such engines significantly exceeds chemical ones. For example, the energy that can be released by 1 kg of the best fuel (a mixture of beryllium with oxygen) is 3 × 107 J, while for polonium isotopes Po210 this value is 5 × 1011 J.

The released energy in a nuclear engine can be used in various ways:

heating the working fluid emitted through the nozzles, as in a traditional liquid-propellant rocket engine, after conversion into electricity, ionizing and accelerating particles of the working fluid, creating an impulse directly by fission or fusion products. Even plain water, but the use of alcohol, ammonia or liquid hydrogen will be much more effective. Depending on the state of aggregation of the fuel for the reactor, nuclear rocket engines are divided into solid-, liquid- and gas-phase. The most developed nuclear propulsion engine is with a solid-phase fission reactor, using fuel rods (fuel elements) used in nuclear power plants as fuel. The first such engine, as part of the American Nerva project, underwent ground testing in 1966, operating for about two hours.

Design features

At the heart of any nuclear space engine is a reactor consisting of a core and a beryllium reflector housed in a power housing. The fission of atoms of a combustible substance, usually uranium U238, enriched in U235 isotopes, occurs in the core. To impart certain properties to the decay process of nuclei, moderators are also located here - refractory tungsten or molybdenum. If the moderator is included in the fuel rods, the reactor is called homogeneous, and if it is placed separately, it is called heterogeneous. The nuclear engine also includes a working fluid supply unit, controls, shadow radiation protection, and a nozzle. Structural elements and components of the reactor, which experience high thermal loads, are cooled by the working fluid, which is then pumped into the fuel assemblies by a turbopump unit. Here it is heated to almost 3,000˚C. Flowing through the nozzle, the working fluid creates jet thrust.

Typical reactor controls are control rods and turntables made of a neutron-absorbing substance (boron or cadmium). The rods are placed directly in the core or in special reflector niches, and the rotary drums are placed on the periphery of the reactor. By moving the rods or turning the drums, the number of fissile nuclei per unit time is changed, regulating the level of energy release of the reactor, and, consequently, its thermal power.

To reduce the intensity of neutron and gamma radiation, which is dangerous for all living things, primary reactor protection elements are placed in the power building.

Increased efficiency

A liquid-phase nuclear engine is similar in operating principle and design to solid-phase ones, but the liquid state of the fuel makes it possible to increase the temperature of the reaction, and, consequently, the thrust of the power unit. So, if for chemical units (liquid turbojet engines and solid propellant rocket engines) the maximum specific impulse (expiration speed of the jet stream) is 5,420 m/s, for solid-phase nuclear engines and 10,000 m/s is far from the limit, then the average value of this indicator for gas-phase nuclear propulsion engines lies in the range 30,000 - 50,000 m/s.

There are two types of gas-phase nuclear engine projects:

An open cycle, in which a nuclear reaction occurs inside a plasma cloud of a working fluid held by an electromagnetic field and absorbing all the generated heat. Temperatures can reach several tens of thousands of degrees. In this case, the active region is surrounded by a heat-resistant substance (for example, quartz) - a nuclear lamp that freely transmits emitted energy. In installations of the second type, the temperature of the reaction will be limited by the melting point of the flask material. At the same time, the energy efficiency of a nuclear space engine is slightly reduced (specific impulse up to 15,000 m/s), but efficiency and radiation safety are increased.

Practical achievements

Formally, the inventor of the power plant on atomic energy is considered to be the American scientist and physicist Richard Feynman. The start of large-scale work on the development and creation of nuclear engines for spacecraft as part of the Rover program was given at the Los Alamos Research Center (USA) in 1955. American inventors preferred installations with a homogeneous nuclear reactor. The first experimental sample of "Kiwi-A" was assembled at a plant at the nuclear center in Albuquerque (New Mexico, USA) and tested in 1959. The reactor was placed vertically on the stand with the nozzle upward. During the tests, a heated stream of spent hydrogen was released directly into the atmosphere. And although the rector worked for low power only about 5 minutes, the success inspired the developers.

In the Soviet Union, a powerful impetus for such research was given by the meeting of the “three great Cs” that took place in 1959 at the Institute of Atomic Energy - the creator atomic bomb I.V. Kurchatov, the chief theorist of Russian cosmonautics M.V. Keldysh and the general designer of Soviet rockets S.P. Korolev. Unlike the American model, the Soviet RD-0410 engine, developed at the design bureau of the Khimavtomatika association (Voronezh), had a heterogeneous reactor. Fire tests took place at a training ground near Semipalatinsk in 1978.

It is worth noting that quite a lot of theoretical projects were created, but the matter never came to practical implementation. The reasons for this were the presence of a huge number of problems in materials science, and a lack of human and financial resources.

For note: an important practical achievement was the flight testing of nuclear-powered aircraft. In the USSR, the most promising was the experimental strategic bomber Tu-95LAL, in the USA - the B-36.

Project "Orion" or pulsed nuclear rocket engines

For flights in space, a pulsed nuclear engine was first proposed to be used in 1945 by an American mathematician of Polish origin, Stanislaw Ulam. In the next decade, the idea was developed and refined by T. Taylor and F. Dyson. The bottom line is that the energy of small nuclear charges, detonated at some distance from the pushing platform on the bottom of the rocket, imparts great acceleration to it.

During the Orion project, launched in 1958, it was planned to equip a rocket with just such an engine capable of delivering people to the surface of Mars or the orbit of Jupiter. The crew, located in the bow compartment, would be protected from the destructive effects of gigantic accelerations by a damping device. The result of detailed engineering work was marching tests of a large-scale mock-up of the ship to study flight stability (ordinary explosives were used instead of nuclear charges). Due to the high cost, the project was closed in 1965.

Similar ideas for creating an “explosive aircraft” were expressed by Soviet academician A. Sakharov in July 1961. To launch the ship into orbit, the scientist proposed using conventional liquid-propellant rocket engines.

Alternative projects

A huge number of projects never went beyond theoretical research. Among them there were many original and very promising ones. The idea of ​​a nuclear power plant based on fissile fragments is confirmed. Design features and the design of this engine makes it possible to do without a working fluid at all. The jet stream, which provides the necessary thrust characteristics, is formed from spent nuclear material. The reactor is based on rotating disks with subcritical nuclear mass (atomic fission coefficient less than unity). When rotating in the sector of the disk located in the core, a chain reaction is started and decaying high-energy atoms are directed into the engine nozzle, forming a jet stream. The preserved intact atoms will take part in the reaction at the next revolutions of the fuel disk.

Projects of a nuclear engine for ships performing certain tasks in near-Earth space, based on RTGs (radioisotope thermoelectric generators), are quite workable, but such installations are unpromising for interplanetary, and even more so interstellar flights.

Nuclear fusion engines have enormous potential. Already at the present stage of development of science and technology, a pulsed installation is quite feasible, in which, like the Orion project, thermonuclear charges will be detonated under the bottom of the rocket. However, many experts consider the implementation of controlled nuclear fusion to be a matter of the near future.

Advantages and disadvantages of nuclear powered engines

The indisputable advantages of using nuclear engines as power units for spacecraft include their high energy efficiency, providing a high specific impulse and good traction performance (up to a thousand tons in airless space), an impressive energy reserve at battery life. The current level of scientific and technological development makes it possible to ensure the comparative compactness of such an installation.

The main drawback of nuclear propulsion engines, which caused the curtailment of design and research work, is the high radiation hazard. This is especially true when conducting ground-based fire tests, as a result of which radioactive gases, uranium compounds and its isotopes, and the destructive effects of penetrating radiation may enter the atmosphere along with the working fluid. For the same reasons, it is unacceptable to launch a spacecraft equipped with a nuclear engine directly from the surface of the Earth.

Present and future

According to the academician of the Russian Academy of Sciences, general director"Keldysh Center" Anatoly Koroteev, a fundamentally new type of nuclear engine in Russia will be created in the near future. The essence of the approach is that the energy of the space reactor will be directed not to directly heating the working fluid and forming a jet stream, but to produce electricity. The role of the mover in the installation is given to plasma engine, the specific thrust of which is 20 times higher than the thrust of chemical rocket vehicles existing today. The head enterprise of the project is a division of the state corporation Rosatom, JSC NIKIET (Moscow).

Full-scale prototype tests were successfully completed back in 2015 on the basis of NPO Mashinostroeniya (Reutov). The date for the start of flight tests of the nuclear power plant is November of this year. Essential Elements and the systems will have to be tested, including on board the ISS.

The new Russian nuclear engine operates according to closed loop, which completely eliminates the entry of radioactive substances into the surrounding space. The mass and dimensional characteristics of the main elements of the power plant ensure its use with existing domestic Proton and Angara launch vehicles.

Russia has tested the cooling system of a nuclear power plant (NPP), one of the key elements of a future spacecraft that will be able to carry out interplanetary flights. Why is a nuclear engine needed in space, how does it work and why Roscosmos considers this development to be the main Russian space trump card, Izvestia reports.

History of the atom

If you put your hand on your heart, since the time of Korolev, the launch vehicles used for flights into space have not undergone any fundamental changes. General principle work - chemical, based on the combustion of fuel with an oxidizer, remains the same. Engines, control systems, and types of fuel are changing. The basis of space travel remains the same - jet thrust pushes the rocket or spacecraft forward.

It is very common to hear that a major breakthrough is needed, a development that can replace the jet engine in order to increase efficiency and make flights to the Moon and Mars more realistic. The fact is that at present, almost the majority of the mass of interplanetary spacecraft is fuel and oxidizer. What if we abandon the chemical engine altogether and start using the energy of a nuclear engine?

The idea of ​​creating a nuclear propulsion system is not new. In the USSR, a detailed government decree on the problem of creating nuclear propulsion systems was signed back in 1958. Even then, studies were carried out that showed that, using a nuclear rocket engine of sufficient power, you can get to Pluto (which has not yet lost its planetary status) and back in six months (two there and four back), spending 75 tons of fuel on the trip.

The USSR was developing a nuclear rocket engine, but scientists have only now begun to approach a real prototype. It's not about money, the topic turned out to be so complex that not a single country has yet been able to create a working prototype, and in most cases it all ended with plans and drawings. The United States tested a propulsion system for a flight to Mars in January 1965. But the NERVA project to conquer Mars using a nuclear engine did not move beyond the KIWI tests, and it was much simpler than the current Russian development. China has set in its space development plans the creation of a nuclear engine closer to 2045, which is also very, very not soon.

In Russia, there is a new round of work on the nuclear project electric propulsion system(NPP) megawatt class for space transport systems started in 2010. The project is being created jointly by Roscosmos and Rosatom, and it can be called one of the most serious and ambitious space projects recent times. The lead contractor for nuclear power engineering is Research Center them. M.V. Keldysh.

Nuclear movement

Throughout development, news leaks to the press about the readiness of one or another part of the future nuclear engine. At the same time, in general, except for specialists, few people imagine how and due to what it will work. Actually, the essence of a space nuclear engine is approximately the same as on Earth. The energy of the nuclear reaction is used to heat and operate the turbogenerator-compressor. To put it simply, a nuclear reaction is used to produce electricity, almost exactly the same as in a conventional one. nuclear power plant. And with the help of electricity, electric rocket engines operate. In this installation, these are high-power ion engines.

In ion engines, thrust is created by creating jet thrust based on ionized gas accelerated to high speeds in an electric field. Ion engines still exist and are being tested in space. So far they have only one problem - almost all of them have very little thrust, although they consume very little fuel. For space travel such engines are: great option, especially if you solve the problem of generating electricity in space, which is what a nuclear installation will do. In addition, ion engines can operate for quite a long time, maximum term continuous operation The most modern examples of ion engines are more than three years old.

If you look at the diagram, you will notice that nuclear energy does not begin its useful work immediately. First, the heat exchanger heats up, then electricity is generated, which is already used to create thrust for the ion engine. Alas, humanity has not yet learned to use nuclear installations for propulsion in a simpler and more efficient way.

In the USSR, satellites with a nuclear installation were launched as part of the Legend target designation complex for naval missile-carrying aircraft, but these were very small reactors, and their work was only enough to generate electricity for the instruments hung on the satellite. Soviet spacecraft had an installation power of three kilowatts, but now Russian specialists are working on creating an installation with a power of more than a megawatt.

Problems on a cosmic scale

Naturally, a nuclear installation in space has many more problems than on Earth, and the most important of them is cooling. IN normal conditions For this, water is used, which absorbs engine heat very effectively. This cannot be done in space, and nuclear engines require efficient system cooling - and the heat from them must be removed into outer space, that is, this can only be done in the form of radiation. Typically, for this purpose, spacecraft use panel radiators - made of metal, with a coolant fluid circulating through them. Alas, such radiators, as a rule, have a large weight and dimensions, in addition, they are in no way protected from meteorites.

In August 2015, at the MAKS air show, a model of drop cooling of nuclear power propulsion systems was shown. In it, liquid dispersed in the form of drops flies in open space, cools, and then reassembles into the installation. Just imagine a huge spaceship, in the center of which is a giant shower installation, from which billions of microscopic drops of water burst out, fly through space, and then are sucked into the huge mouth of a space vacuum cleaner.

More recently, it became known that the droplet cooling system of a nuclear propulsion system was tested under terrestrial conditions. In this case, the cooling system is the most important stage in creating the installation.

Now it’s a matter of testing its performance in zero-gravity conditions, and only after that can we try to create a cooling system in the dimensions required for installation. Each such successful test brings us a little closer Russian specialists to the creation of a nuclear installation. Scientists are rushing with all their might, because it is believed that launching a nuclear engine into space will help Russia regain its leadership position in space.

Nuclear space age

Let’s say this succeeds, and in a few years a nuclear engine will begin operating in space. How will this help, how can it be used? To begin with, it is worth clarifying that in the form in which the nuclear propulsion system exists today, it can only operate in outer space. There is no way it can take off from the Earth and land in this form; for now it cannot do without traditional chemical rockets.

Why in space? Well, humanity flies to Mars and the Moon quickly, and that’s all? Not really. Currently, all projects of orbital plants and factories operating in Earth orbit are stalled due to lack of raw materials for work. There's no point in building anything in space until a way to put it into orbit has been found. large number required raw materials, such as metal ore.

But why lift them from Earth if, on the contrary, you can bring them from space. In the same asteroid belt solar system there are simply huge reserves of various metals, including precious ones. And in this case, the creation of a nuclear tug will simply be a lifesaver.

Bring a huge platinum- or gold-bearing asteroid into orbit and start cutting it apart right in space. According to experts, such production, taking into account the volume, may turn out to be one of the most profitable.

Is there a less fantastic use for a nuclear tug? For example, it can be used to transport satellites in the required orbits or bring spacecraft to the desired point in space, for example, to lunar orbit. Currently, upper stages are used for this, for example the Russian Fregat. They are expensive, complex and disposable. A nuclear tug will be able to pick them up in low Earth orbit and deliver them wherever needed.

The same goes for interplanetary travel. Without fast way There is simply no chance of delivering cargo and people to Mars orbit to begin colonization. The current generation of launch vehicles will do this very expensively and for a long time. Until now, the flight duration remains one of the most serious problems when flying to other planets. Surviving months of travel to Mars and back in a closed spacecraft capsule is no easy task. A nuclear tug can help here too, significantly reducing this time.

Necessary and sufficient

At present, all this looks like science fiction, but, according to scientists, there are only a few years left before testing the prototype. The main thing that is required is not only to complete the development, but also to maintain the required level of astronautics in the country. Even with a drop in funding, rockets must continue to take off, spacecraft are built, and the most valuable specialists must continue to work.

Otherwise, one nuclear engine without the appropriate infrastructure will not help the matter; for maximum efficiency, the development will be very important not only to sell, but to use independently, showing all the capabilities of the new space vehicle.

In the meantime, all residents of the country who are not tied to work can only look at the sky and hope that everything will work out for the Russian cosmonautics. And a nuclear tug, and the preservation of current capabilities. I don’t want to believe in other outcomes.