Alexander Losev
The rapid development of rocket and space technology in the 20th century was determined by the military-strategic, political and, to a certain extent, ideological goals and interests of the two superpowers - the USSR and the USA, and all state space programs were a continuation of their military projects, where the main task was the need to ensure defense capability and strategic parity with a potential enemy. The cost of creating equipment and operating costs were not of fundamental importance then. Enormous resources were allocated to the creation of launch vehicles and spacecraft, and the 108-minute flight of Yuri Gagarin in 1961 and the television broadcast of Neil Armstrong and Buzz Aldrin from the surface of the Moon in 1969 were not just triumphs of scientific and technical thought, they were also considered as strategic victories in battles of the Cold War.
But after the Soviet Union collapsed and dropped out of the race for world leadership, its geopolitical opponents, primarily the United States, no longer needed to implement prestigious but extremely costly space projects in order to prove to the whole world the superiority of the Western economic system and ideological concepts.
In the 90s, the main political tasks of previous years lost relevance, bloc confrontation was replaced by globalization, pragmatism prevailed in the world, so most space programs were curtailed or postponed; only the ISS remained as a legacy from the large-scale projects of the past. In addition, Western democracy has made all expensive government programs dependent on electoral cycles.
Voter support, necessary to gain or maintain power, forces politicians, parliaments and governments to lean toward populism and solve short-term problems, so spending on space exploration is reduced year after year.
Most of the fundamental discoveries were made in the first half of the twentieth century, and today science and technology have reached certain limits, moreover, the popularity of scientific knowledge has decreased throughout the world, and the quality of teaching mathematics, physics and other natural sciences has deteriorated. This has become the reason for the stagnation, including in the space sector, of the last two decades.
But now it becomes obvious that the world is approaching the end of another technological cycle based on the discoveries of the last century. Therefore, any power that will possess fundamentally new promising technologies at the time of change in the global technological structure will automatically ensure global leadership for at least the next fifty years.
Fundamental design of a nuclear propulsion engine with hydrogen as a working fluid
This is realized both in the United States, which has set a course for the revival of American greatness in all spheres of activity, and in China, which is challenging American hegemony, and in the European Union, which is trying with all its might to maintain its weight in the global economy.
There is an industrial policy there and they are seriously engaged in the development of their own scientific, technical and production potential, and the space sphere can become the best testing ground for testing new technologies and for proving or refuting scientific hypotheses that can lay the foundation for the creation of a fundamentally different, more advanced technology of the future.
And it is quite natural to expect that the United States will be the first country where deep space exploration projects will be resumed in order to create unique innovative technologies in the field of weapons, transport and structural materials, as well as in biomedicine and telecommunications
True, not even the United States is guaranteed success in creating revolutionary technologies. There is a high risk of ending up in a dead end when improving half-a-century old rocket engines based on chemical fuel, as Elon Musk’s SpaceX is doing, or when creating life support systems for long flights similar to those already implemented on the ISS.
Can Russia, whose stagnation in the space sector is becoming more noticeable every year, make a leap in the race for future technological leadership to remain in the club of superpowers, and not in the list of developing countries?
Yes, of course, Russia can, and moreover, a noticeable step forward has already been made in nuclear energy and in nuclear rocket engine technologies, despite the chronic underfunding of the space industry.
The future of astronautics is the use of nuclear energy. To understand how nuclear technology and space are connected, it is necessary to consider the basic principles of jet propulsion.
So, the main types of modern space engines are created on the principles of chemical energy. These are solid fuel accelerators and liquid rocket engines, in their combustion chambers the fuel components (fuel and oxidizer) enter into an exothermic physical and chemical combustion reaction, forming a jet stream that ejects tons of substance from the engine nozzle every second. The kinetic energy of the jet's working fluid is converted into a reactive force sufficient to propel the rocket. The specific impulse (the ratio of the thrust generated to the mass of the fuel used) of such chemical engines depends on the fuel components, the pressure and temperature in the combustion chamber, as well as the molecular weight of the gaseous mixture ejected through the engine nozzle.
And the higher the temperature of the substance and the pressure inside the combustion chamber, and the lower the molecular mass of the gas, the higher the specific impulse, and therefore the efficiency of the engine. Specific impulse is a quantity of motion and is usually measured in meters per second, just like speed.
In chemical engines, the highest specific impulse is provided by oxygen-hydrogen and fluorine-hydrogen fuel mixtures (4500–4700 m/s), but the most popular (and convenient to operate) have become rocket engines running on kerosene and oxygen, for example the Soyuz and Musk's Falcon rockets, as well as engines using unsymmetrical dimethylhydrazine (UDMH) with an oxidizer in the form of a mixture of nitrogen tetroxide and nitric acid (Soviet and Russian Proton, French Ariane, American Titan). Their efficiency is 1.5 times lower than that of hydrogen fuel engines, but an impulse of 3000 m/s and power are quite enough to make it economically profitable to launch tons of payload into near-Earth orbits.
But flights to other planets require much larger spacecraft than anything mankind has previously created, including the modular ISS. In these ships it is necessary to ensure long-term autonomous existence of the crews, and a certain supply of fuel and service life of the main engines and engines for maneuvers and orbit correction, to provide for the delivery of astronauts in a special landing module to the surface of another planet, and their return to the main transport ship, and then and the return of the expedition to Earth.
The accumulated engineering knowledge and chemical energy of engines make it possible to return to the Moon and reach Mars, so there is a high probability that humanity will visit the Red Planet in the next decade.
If we rely only on existing space technologies, then the minimum mass of the habitable module for a manned flight to Mars or to the satellites of Jupiter and Saturn will be approximately 90 tons, which is 3 times more than the lunar ships of the early 1970s, which means launch vehicles for their launch into reference orbits for further flight to Mars will be much superior to the Saturn 5 (launch weight 2965 tons) of the Apollo lunar project or the Soviet carrier Energia (launch weight 2400 tons). It will be necessary to create an interplanetary complex in orbit weighing up to 500 tons. A flight on an interplanetary ship with chemical rocket engines will require from 8 months to 1 year in one direction only, because you will have to do gravity maneuvers, using the gravitational force of the planets and a colossal supply of fuel to additionally accelerate the ship.
But using the chemical energy of rocket engines, humanity will not fly further than the orbit of Mars or Venus. We need different flight speeds of spacecraft and other more powerful energy of movement.
Modern design of a nuclear rocket engine Princeton Satellite Systems
To explore deep space, it is necessary to significantly increase the thrust-to-weight ratio and efficiency of the rocket engine, and therefore increase its specific impulse and service life. And to do this, it is necessary to heat a gas or working fluid substance with low atomic mass inside the engine chamber to temperatures several times higher than the chemical combustion temperature of traditional fuel mixtures, and this can be done using a nuclear reaction.
If, instead of a conventional combustion chamber, a nuclear reactor is placed inside a rocket engine, into the active zone of which a substance in liquid or gaseous form is supplied, then it, heated under high pressure up to several thousand degrees, will begin to be ejected through the nozzle channel, creating jet thrust. The specific impulse of such a nuclear jet engine will be several times greater than that of a conventional one with chemical components, which means that the efficiency of both the engine itself and the launch vehicle as a whole will increase many times over. In this case, an oxidizer for fuel combustion will not be required, and light hydrogen gas can be used as a substance that creates jet thrust; we know that the lower the molecular mass of the gas, the higher the impulse, and this will greatly reduce the mass of the rocket with better performance engine power.
A nuclear engine will be better than a conventional one, since in the reactor zone the light gas can be heated to temperatures exceeding 9 thousand degrees Kelvin, and a jet of such superheated gas will provide a much higher specific impulse than conventional chemical engines can provide. But this is in theory.
The danger is not even that when a launch vehicle with such a nuclear installation is launched, radioactive contamination of the atmosphere and space around the launch pad may occur; the main problem is that at high temperatures the engine itself, along with the spacecraft, may melt. Designers and engineers understand this and have been trying to find suitable solutions for several decades.
Nuclear rocket engines (NRE) already have their own history of creation and operation in space. The first development of nuclear engines began in the mid-1950s, that is, even before human flight into space, and almost simultaneously in both the USSR and the USA, and the very idea of using nuclear reactors to heat the working substance in a rocket engine was born along with the first rectors in mid-40s, that is, more than 70 years ago.
In our country, the initiator of the creation of nuclear propulsion was the thermal physicist Vitaly Mikhailovich Ievlev. In 1947, he presented a project that was supported by S. P. Korolev, I. V. Kurchatov and M. V. Keldysh. Initially, it was planned to use such engines for cruise missiles, and then install them on ballistic missiles. The development was undertaken by the leading defense design bureaus of the Soviet Union, as well as research institutes NIITP, CIAM, IAE, VNIINM.
The Soviet nuclear engine RD-0410 was assembled in the mid-60s at the Voronezh Chemical Automatics Design Bureau, where most liquid rocket engines for space technology were created.
Hydrogen was used as a working fluid in RD-0410, which in liquid form passed through a “cooling jacket”, removing excess heat from the walls of the nozzle and preventing it from melting, and then entered the reactor core, where it was heated to 3000K and released through the channel nozzles, thus converting thermal energy into kinetic energy and creating a specific impulse of 9100 m/s.
In the USA, the nuclear propulsion project was launched in 1952, and the first operating engine was created in 1966 and was named NERVA (Nuclear Engine for Rocket Vehicle Application). In the 60s and 70s, the Soviet Union and the United States tried not to yield to each other.
True, both our RD-0410 and the American NERVA were solid-phase nuclear propellant engines (nuclear fuel based on uranium carbides was in the solid state in the reactor), and their operating temperature was in the range of 2300–3100K.
To increase the temperature of the core without the risk of explosion or melting of the reactor walls, it is necessary to create such nuclear reaction conditions under which the fuel (uranium) turns into a gaseous state or turns into plasma and is held inside the reactor by a strong magnetic field, without touching the walls. And then the hydrogen entering the reactor core “flows around” the uranium in the gas phase, and turning into plasma, is ejected at a very high speed through the nozzle channel.
This type of engine is called a gas-phase nuclear propulsion engine. The temperatures of the gaseous uranium fuel in such nuclear engines can range from 10 thousand to 20 thousand degrees Kelvin, and the specific impulse can reach 50,000 m/s, which is 11 times higher than that of the most efficient chemical rocket engines.
The creation and use of gas-phase nuclear propulsion engines of open and closed types in space technology is the most promising direction in the development of space rocket engines and exactly what humanity needs to explore the planets of the Solar System and their satellites.
The first research on the gas-phase nuclear propulsion project began in the USSR in 1957 at the Research Institute of Thermal Processes (National Research Center named after M. V. Keldysh), and the decision to develop nuclear space power plants based on gas-phase nuclear reactors was made in 1963 by Academician V. P. Glushko (NPO Energomash), and then approved by a resolution of the CPSU Central Committee and the Council of Ministers of the USSR.
The development of gas-phase nuclear propulsion engines was carried out in the Soviet Union for two decades, but, unfortunately, was never completed due to insufficient funding and the need for additional fundamental research in the field of thermodynamics of nuclear fuel and hydrogen plasma, neutron physics and magnetohydrodynamics.
Soviet nuclear scientists and design engineers faced a number of problems, such as achieving criticality and ensuring the stability of the operation of a gas-phase nuclear reactor, reducing the loss of molten uranium during the release of hydrogen heated to several thousand degrees, thermal protection of the nozzle and magnetic field generator, and the accumulation of uranium fission products , selection of chemically resistant construction materials, etc.
And when the Energia launch vehicle began to be created for the Soviet Mars-94 program for the first manned flight to Mars, the nuclear engine project was postponed indefinitely. The Soviet Union did not have enough time, and most importantly, political will and economic efficiency, to land our cosmonauts on the planet Mars in 1994. This would be an undeniable achievement and proof of our leadership in high technology over the next few decades. But space, like many other things, was betrayed by the last leadership of the USSR. History cannot be changed, departed scientists and engineers cannot be brought back, and lost knowledge cannot be restored. A lot will have to be created anew.
But space nuclear power is not limited only to the sphere of solid- and gas-phase nuclear propulsion engines. Electrical energy can be used to create a heated flow of matter in a jet engine. This idea was first expressed by Konstantin Eduardovich Tsiolkovsky back in 1903 in his work “Exploration of world spaces using jet instruments.”
And the first electrothermal rocket engine in the USSR was created in the 1930s by Valentin Petrovich Glushko, a future academician of the USSR Academy of Sciences and the head of NPO Energia.
The operating principles of electric rocket engines can be different. They are usually divided into four types:
- electrothermal (heating or electric arc). In them, the gas is heated to temperatures of 1000–5000K and ejected from the nozzle in the same way as in a nuclear rocket engine.
- electrostatic engines (colloidal and ionic), in which the working substance is first ionized, and then positive ions (atoms devoid of electrons) are accelerated in an electrostatic field and are also ejected through the nozzle channel, creating jet thrust. Electrostatic engines also include stationary plasma engines.
- magnetoplasma and magnetodynamic rocket engines. There, the gas plasma is accelerated due to the Ampere force in the magnetic and electric fields intersecting perpendicularly.
- pulse rocket engines, which use the energy of gases resulting from the evaporation of a working fluid in an electric discharge.
The advantage of these electric rocket engines is the low consumption of the working fluid, efficiency up to 60% and high particle flow speed, which can significantly reduce the mass of the spacecraft, but there is also a disadvantage - low thrust density, and therefore low power, as well as the high cost of the working fluid (inert gases or vapors of alkali metals) to create plasma.
All of the listed types of electric motors have been implemented in practice and have been repeatedly used in space on both Soviet and American spacecraft since the mid-60s, but due to their low power they were used mainly as orbit correction engines.
From 1968 to 1988, the USSR launched a whole series of Cosmos satellites with nuclear installations on board. The types of reactors were named: “Buk”, “Topaz” and “Yenisei”.
The Yenisei project reactor had a thermal power of up to 135 kW and an electrical power of about 5 kW. The coolant was a sodium-potassium melt. This project was closed in 1996.
A real propulsion rocket motor requires a very powerful source of energy. And the best source of energy for such space engines is a nuclear reactor.
Nuclear energy is one of the high-tech industries where our country maintains a leading position. And a fundamentally new rocket engine is already being created in Russia and this project is close to successful completion in 2018. Flight tests are scheduled for 2020.
And if gas-phase nuclear propulsion is a topic for future decades that will have to be returned to after fundamental research, then its today’s alternative is a megawatt-class nuclear power propulsion system (NPPU), and it has already been created by Rosatom and Roscosmos enterprises since 2009.
NPO Krasnaya Zvezda, which is currently the world's only developer and manufacturer of space nuclear power plants, as well as the Research Center named after A. M. V. Keldysh, NIKIET im. N.A. Dollezhala, Research Institute NPO “Luch”, “Kurchatov Institute”, IRM, IPPE, RIAR and NPO Mashinostroeniya.
The nuclear power propulsion system includes a high-temperature gas-cooled fast neutron nuclear reactor with a turbomachine system for converting thermal energy into electrical energy, a system of refrigerator-emitters for removing excess heat into space, an instrumentation compartment, a block of sustainer plasma or ion electric motors, and a container for accommodating the payload. .
In a power propulsion system, a nuclear reactor serves as a source of electricity for the operation of electric plasma engines, while the gas coolant of the reactor passing through the core enters the turbine of the electric generator and compressor and returns back to the reactor in a closed loop, and is not thrown into space as in a nuclear propulsion engine, which makes the design more reliable and safe, and therefore suitable for manned space flight.
It is planned that the nuclear power plant will be used for a reusable space tug to ensure the delivery of cargo during the exploration of the Moon or the creation of multi-purpose orbital complexes. The advantage will be not only the reusable use of elements of the transport system (which Elon Musk is trying to achieve in his SpaceX space projects), but also the ability to deliver three times more cargo than on rockets with chemical jet engines of comparable power by reducing the launch mass of the transport system . The special design of the installation makes it safe for people and the environment on Earth.
In 2014, the first standard design fuel element (fuel element) for this nuclear electric propulsion system was assembled at JSC Mashinostroitelny Zavod in Elektrostal, and in 2016 tests of a reactor core basket simulator were carried out.
Now (in 2017) work is underway on the manufacture of structural elements of the installation and testing of components and assemblies on mock-ups, as well as autonomous testing of turbomachine energy conversion systems and prototype power units. Completion of the work is scheduled for the end of next 2018, however, since 2015, the backlog of the schedule began to accumulate.
So, as soon as this installation is created, Russia will become the first country in the world to possess nuclear space technologies, which will form the basis not only for future projects for the exploration of the Solar system, but also for terrestrial and extraterrestrial energy. Space nuclear power plants can be used to create systems for remote transmission of electricity to Earth or to space modules using electromagnetic radiation. And this will also become an advanced technology of the future, where our country will have a leading position.
Based on the plasma electric motors being developed, powerful propulsion systems will be created for long-distance human flights into space and, first of all, for the exploration of Mars, the orbit of which can be reached in just 1.5 months, and not in more than a year, as when using conventional chemical jet engines .
And the future always begins with a revolution in energy. And nothing else. Energy is primary and it is the amount of energy consumption that affects technical progress, defense capability and the quality of life of people.
NASA experimental plasma rocket engine
Soviet astrophysicist Nikolai Kardashev proposed a scale of development of civilizations back in 1964. According to this scale, the level of technological development of civilizations depends on the amount of energy that the planet's population uses for its needs. Thus, type I civilization uses all available resources available on the planet; Type II civilization - receives the energy of its star in the system of which it is located; and a type III civilization uses the available energy of its galaxy. Humanity has not yet matured to type I civilization on this scale. We use only 0.16% of the total potential energy reserve of planet Earth. This means that Russia and the whole world have room to grow, and these nuclear technologies will open the way for our country not only to space, but also to future economic prosperity.
And, perhaps, the only option for Russia in the scientific and technical sphere is to now make a revolutionary breakthrough in nuclear space technologies in order to overcome the many-year lag behind the leaders in one “leap” and be right at the origins of a new technological revolution in the next cycle of development of human civilization. Such a unique chance falls to a particular country only once every few centuries.
Unfortunately, Russia, which has not paid enough attention to fundamental sciences and the quality of higher and secondary education over the past 25 years, risks losing this chance forever if the program is curtailed and a new generation of researchers does not replace the current scientists and engineers. The geopolitical and technological challenges that Russia will face in 10–12 years will be very serious, comparable to the threats of the mid-twentieth century. In order to preserve the sovereignty and integrity of Russia in the future, it is now urgently necessary to begin training specialists capable of responding to these challenges and creating something fundamentally new.
There are only about 10 years to transform Russia into a global intellectual and technological center, and this cannot be done without a serious change in the quality of education. For a scientific and technological breakthrough, it is necessary to return to the education system (both school and university) systematic views on the picture of the world, scientific fundamentality and ideological integrity.
As for the current stagnation in the space industry, this is not scary. The physical principles on which modern space technologies are based will be in demand for a long time in the conventional satellite services sector. Let us remember that humanity used the sail for 5.5 thousand years, and the era of steam lasted almost 200 years, and only in the twentieth century the world began to change rapidly, because another scientific and technological revolution took place, which launched a wave of innovation and a change in technological structures, which ultimately changed both the world economy and politics. The main thing is to be at the origins of these changes [email protected] ,
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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 the conversion of the energy of the chemical reaction of fuel combustion 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 synthesis products. Even ordinary water can act as a working fluid, but the use of alcohol will be much more effective, ammonia or liquid hydrogen. 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 (jet flow velocity) 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 propellant 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 American scientist and physicist Richard Feynman is considered to be the inventor of the nuclear power plant. 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 at low power for 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 Ks” that took place in 1959 at the Institute of Atomic Energy - the creator of the atomic bomb I.V. Kurchatov, the chief theorist of Russian cosmonautics M.V. Keldysh and the general designer of Soviet rockets S.P. Queen. 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. The design features and structure of this engine make 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 of little promise 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 high specific impulse and good thrust performance (up to a thousand tons in airless space), and impressive energy reserves during autonomous operation. 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 assurances of Academician of the Russian Academy of Sciences, General Director of the Keldysh Center Anatoly Koroteev, a fundamentally new type of nuclear engine will be created in Russia 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 propulsion in the installation is assigned to a plasma engine, the specific thrust of which is 20 times higher than the thrust of chemical jet devices 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 testing of the nuclear power plant is November of this year. The most important elements and systems will have to be tested, including on board the ISS.
The new Russian nuclear engine operates in a closed cycle, which completely eliminates the release 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 was and now remains a leader in the field of nuclear space energy. Organizations such as RSC Energia and Roscosmos have experience in the design, construction, launch and operation of spacecraft equipped with a nuclear power source. A nuclear engine makes it possible to operate aircraft for many years, greatly increasing their practical suitability.
Historical chronicle
At the same time, delivering a research vehicle into the orbits of the distant planets of the Solar System requires increasing the resource of such a nuclear installation to 5-7 years. It has been proven that a complex with a nuclear propulsion system with a power of about 1 MW as part of a research spacecraft will allow for accelerated delivery in 5-7 years of artificial satellites of the most distant planets, planetary rovers to the surface of the natural satellites of these planets and delivery to Earth of soil from comets, asteroids, Mercury and satellites of Jupiter and Saturn.
Reusable tug (MB)
One of the most important ways to increase the efficiency of transport operations in space is the reusable use of elements of the transport system. A nuclear engine for spacecraft with a power of at least 500 kW makes it possible to create a reusable tug and thereby significantly increase the efficiency of a multi-link space transport system. Such a system is especially useful in a program for providing large annual cargo flows. An example would be the lunar exploration program with the creation and maintenance of a constantly expanding habitable base and experimental technological and production complexes.
Freight turnover calculation
According to the design studies of RSC Energia, during the construction of the base, modules weighing about 10 tons should be delivered to the lunar surface, and up to 30 tons to the lunar orbit. The total cargo flow from the Earth during the construction of a habitable lunar base and a visited lunar orbital station is estimated at 700-800 tons , and the annual cargo flow to ensure the functioning and development of the base is 400-500 tons.
However, the operating principle of the nuclear engine does not allow the transporter to accelerate quickly enough. Due to the long transportation time and, accordingly, the significant time spent by the payload in the Earth's radiation belts, not all cargo can be delivered using nuclear-powered tugs. Therefore, the cargo flow that can be provided on the basis of nuclear powered propulsion systems is estimated at only 100-300 tons/year.
Economic efficiency
As a criterion for the economic efficiency of an interorbital transport system, it is advisable to use the value of the specific cost of transporting a unit of mass of payload (PG) from the Earth's surface to the target orbit. RSC Energia has developed an economic and mathematical model that takes into account the main components of costs in the transport system:
- to create and launch into orbit tug modules;
- for the purchase of a working nuclear installation;
- operating costs, as well as R&D costs and possible capital costs.
Cost indicators depend on the optimal parameters of the MB. Using this model, the comparative economic efficiency of using a reusable tug based on a nuclear power propulsion system with a power of about 1 MW and a disposable tug based on advanced liquid propulsion systems in a program to ensure the delivery of a payload with a total mass of 100 tons/year from the Earth to the lunar orbit at a height of 100 km was studied. When using the same launch vehicle with a payload capacity equal to the payload capacity of the Proton-M launch vehicle, and a two-launch scheme for constructing a transport system, the specific cost of delivering a payload mass unit using a nuclear-powered tug will be three times lower than when using disposable tugs based on rockets with liquid engines of the DM-3 type.
Conclusion
An effective nuclear engine for space contributes to the solution of environmental problems of the Earth, human flight to Mars, the creation of a system for wireless energy transmission in space, the implementation with increased safety of burial in space of especially dangerous radioactive waste of ground-based nuclear power, the creation of a habitable lunar base and the beginning of industrial development of the Moon, ensuring protecting the Earth from asteroid-comet danger.
IN one of the sections On LiveJournal, an electronics engineer constantly writes about nuclear and thermonuclear machines - reactors, installations, research laboratories, accelerators, as well as about. The new Russian missile, testimony during the annual presidential address, aroused the keen interest of the blogger. And this is what he found on this topic.
Yes, historically there have been developments of cruise missiles with a ramjet nuclear air engine: the SLAM missile in the USA with the TORY-II reactor, the Avro Z-59 concept in the UK, developments in the USSR.
A modern rendering of the Avro Z-59 rocket concept, weighing about 20 tons.
However, all this work was carried out in the 60s as R&D of varying degrees of depth (the United States went the furthest, as discussed below) and was not continued in the form of models in service. We didn’t get it for the same reason as many other Atom Age developments - planes, trains, missiles with nuclear power plants. All these vehicle options, while having some advantages provided by the insane energy density in nuclear fuel, have very serious disadvantages - high cost, complexity of operation, requirements for constant security, and finally, unsatisfactory development results, about which little is usually known (by publishing the results of R&D it is more profitable for all parties display achievements and hide failures).
In particular, for cruise missiles it is much easier to create a carrier (submarine or aircraft) that will “drag” many missile launchers to the launch site than to fool around with a small fleet (and it is incredibly difficult to develop a large fleet) of cruise missiles launched from one’s own territory. A universal, cheap, mass-produced product ultimately won out over a small-scale, expensive product with ambiguous advantages. Nuclear cruise missiles have not gone beyond ground testing.
This conceptual dead end of the 60s of the Kyrgyz Republic with nuclear power plants, in my opinion, is still relevant now, so the main question to the one shown is “why??”. But what makes it even more prominent are the problems that arise during the development, testing and operation of such weapons, which we will discuss further.
So, let's start with the reactor. The SLAM and Z-59 concepts were three-mach low-flying rockets of impressive size and weight (20+ tons after the launch boosters were jettisoned). The terribly expensive low-flying supersonic made it possible to make maximum use of the presence of a practically unlimited source of energy on board; in addition, an important feature of the nuclear air jet engine is improved operating efficiency (thermodynamic cycle) with increasing speed, i.e. the same idea, but at speeds of 1000 km/h it would have a much heavier and larger engine. Finally, 3M at an altitude of a hundred meters in 1965 meant invulnerability to air defense. It turns out that earlier the concept of missile launchers with nuclear power was “tied up” at high speed, where the advantages of the concept were strong, and competitors with hydrocarbon fuel were weakening. The shown rocket, in my opinion look, transonic or subsonic (if, of course, you believe that it is she in the video). But at the same time, the size of the reactor has decreased significantly compared to TORY-II from the SLAM rocket, where it was as much as 2 meters including the radial neutron reflector made of graphite
Is it even possible to install a reactor with a diameter of 0.4-0.6 meters?
Let's start with a fundamentally minimal reactor - a Pu239 pig. A good example of the implementation of such a concept is the Kilopower space reactor, which, however, uses U235. The diameter of the reactor core is only 11 centimeters! If we switch to plutonium 239, the size of the core will drop by another 1.5-2 times. Now from the minimum size we will begin to step towards a real nuclear air jet engine, remembering the difficulties.
The very first thing to add to the size of the reactor is the size of the reflector - in particular, in Kilopower BeO triples the size. Secondly, we cannot use U or Pu blanks - they will simply burn out in the air flow in just a minute. A shell is needed, for example from incaloy, which resists instant oxidation up to 1000 C, or other nickel alloys with a possible ceramic coating. The introduction of a large amount of shell material into the core increases the required amount of nuclear fuel several times at once - after all, the “unproductive” absorption of neutrons in the core has now increased sharply!
Moreover, the metal form of U or Pu is no longer suitable - these materials themselves are not refractory (plutonium generally melts at 634 C), and they also interact with the material of the metal shells. We convert the fuel into the classical form of UO2 or PuO2 - we get another dilution of the material in the core, this time with oxygen.
Finally, let's remember the purpose of the reactor. We need to pump a lot of air through it, to which we will give off heat. Approximately 2/3 of the space will be occupied by “air tubes”.
As a result, the minimum diameter of the core grows to 40-50 cm (for uranium), and the diameter of the reactor with a 10-centimeter beryllium reflector to 60-70 cm. My knee-jerk estimates “by analogy” are confirmed by the design of a nuclear jet engine MITEE , designed for flights in the atmosphere of Jupiter. This completely paper project (for example, the core temperature is assumed to be 3000 K, and the walls are made of beryllium, which can withstand at most 1200 K) has a core diameter calculated from neutronics of 55.4 cm, despite the fact that cooling with hydrogen makes it possible to slightly reduce the size of the channels through which the coolant is pumped .
In my opinion, an airborne nuclear jet engine can be shoved into a rocket with a diameter of about a meter, which, however, is still not radically larger than the stated 0.6-0.74 m, but is still alarming. One way or another, the nuclear power plant will have a power of ~several megawatt, powered by ~10^16 decays per second. This means that the reactor itself will create a radiation field of several tens of thousands of roentgens at the surface, and up to a thousand roentgens along the entire rocket. Even installing several hundred kg of sector protection will not significantly reduce these levels, because Neutron and gamma rays will be reflected from the air and “bypass the protection.”
In a few hours, such a reactor will produce ~10^21-10^22 atoms of fission products c with an activity of several (several tens) petabecquerels, which even after shutdown will create a background of several thousand roentgens near the reactor.
The rocket design will be activated to about 10^14 Bq, although the isotopes will be primarily beta emitters and are only dangerous by bremsstrahlung X-rays. The background from the structure itself can reach tens of roentgens at a distance of 10 meters from the rocket body.
All this “fun” gives the idea that the development and testing of such a rocket is a task on the verge of the possible. It is necessary to create a whole set of radiation-resistant navigation and control equipment, to test it all in a fairly comprehensive way (radiation, temperature, vibration - and all this for statistics). Flight tests with a working reactor can at any moment turn into a radiation disaster with a release of hundreds of terrabecquerels to several petabecquerels. Even without catastrophic situations, depressurization of individual fuel elements and the release of radionuclides are very likely.
Of course, in Russia there are still Novozemelsky test site on which such tests can be carried out, but this would be contrary to the spirit of the agreement on banning nuclear weapons testing in three environments (the ban was introduced in order to prevent systematic pollution of the atmosphere and ocean by radionuclides).
Finally, I wonder who in the Russian Federation could develop such a reactor. Traditionally, the Kurchatov Institute (general design and calculations), Obninsk IPPE (experimental testing and fuel), and the Luch Research Institute in Podolsk (fuel and materials technology) were initially involved in high-temperature reactors. Later, the NIKIET team became involved in the design of such machines (for example, the IGR and IVG reactors are prototypes of the core of the RD-0410 nuclear rocket engine).
Today NIKIET has a team of designers who carry out work on reactor design ( high-temperature gas-cooled RUGK , fast reactors MBIR, ), and IPPE and Luch continue to engage in related calculations and technologies, respectively. In recent decades, the Kurchatov Institute has moved more toward the theory of nuclear reactors.
In summary, I would like to say that the creation of a cruise missile with air-jet engines with a nuclear power plant is generally a feasible task, but at the same time extremely expensive and complex, requiring a significant mobilization of human and financial resources, it seems to me to a greater extent than all other announced projects (" Sarmat", "Dagger", "Status-6", "Vanguard"). It is very strange that this mobilization did not leave the slightest trace. And most importantly, it is completely unclear what the benefits of obtaining such types of weapons (against the background of existing carriers) are, and how they can outweigh the numerous disadvantages - issues of radiation safety, high cost, incompatibility with strategic arms reduction treaties.
P.S. However, “sources” are already beginning to soften the situation: “A source close to the military-industrial complex said “ Vedomosti "that radiation safety was ensured during rocket testing. The nuclear installation on board was represented by an electrical mock-up, the source says.
One could begin this article with a traditional passage about how science fiction writers put forward bold ideas, and scientists then bring them to life. You can, but you don’t want to write with stamps. It is better to remember that modern rocket engines, solid fuel and liquid, have more than unsatisfactory characteristics for flights over relatively long distances. They allow you to launch cargo into Earth orbit and deliver something to the Moon, although such a flight is more expensive. But flying to Mars with such engines is no longer easy. Give them fuel and oxidizer in the required quantities. And these volumes are directly proportional to the distance that must be overcome.
An alternative to traditional chemical rocket engines are electric, plasma and nuclear engines. Of all the alternative engines, only one system has reached the stage of engine development - nuclear (Nuclear Reaction Engine). In the Soviet Union and the United States, work began on the creation of nuclear rocket engines back in the 50s of the last century. The Americans were working on both options for such a power plant: reactive and pulsed. The first concept involves heating the working fluid using a nuclear reactor and then releasing it through nozzles. The pulse nuclear propulsion engine, in turn, propels the spacecraft through successive explosions of small amounts of nuclear fuel.
Also in the USA, the Orion project was invented, combining both versions of the nuclear powered engine. This was done in the following way: small nuclear charges with a capacity of about 100 tons of TNT were ejected from the tail of the ship. Metal discs were fired after them. At a distance from the ship, the charge was detonated, the disk evaporated, and the substance scattered in different directions. Part of it fell into the reinforced tail section of the ship and moved it forward. A small increase in thrust should have been provided by the evaporation of the plate taking the blows. The unit cost of such a flight should have been only 150 then dollars per kilogram of payload.
It even got to the point of testing: experience showed that movement with the help of successive impulses is possible, as is the creation of a stern plate of sufficient strength. But the Orion project was closed in 1965 as unpromising. However, this is so far the only existing concept that can allow expeditions at least across the solar system.
It was only possible to reach the construction of a prototype with a nuclear-powered rocket engine. These were the Soviet RD-0410 and the American NERVA. They worked on the same principle: in a “conventional” nuclear reactor, the working fluid is heated, which, when ejected from the nozzles, creates thrust. The working fluid of both engines was liquid hydrogen, but the Soviet one used heptane as an auxiliary substance.
The thrust of the RD-0410 was 3.5 tons, NERVA gave almost 34, but it also had large dimensions: 43.7 meters in length and 10.5 in diameter versus 3.5 and 1.6 meters, respectively, for the Soviet engine. At the same time, the American engine was three times inferior to the Soviet one in terms of resource - the RD-0410 could work for an hour.
However, both engines, despite their promise, also remained on Earth and did not fly anywhere. The main reason for the closure of both projects (NERVA in the mid-70s, RD-0410 in 1985) was money. The characteristics of chemical engines are worse than those of nuclear engines, but the cost of one launch of a ship with a nuclear propulsion engine with the same payload can be 8-12 times more than the launch of the same Soyuz with a liquid propellant engine. And this does not even take into account all the costs necessary to bring nuclear engines to the point of being suitable for practical use.
The decommissioning of “cheap” Shuttles and the recent lack of revolutionary breakthroughs in space technology requires new solutions. In April of this year, the then head of Roscosmos A. Perminov announced his intention to develop and put into operation a completely new nuclear propulsion system. This is precisely what, in the opinion of Roscosmos, should radically improve the “situation” in the entire world cosmonautics. Now it has become clear who should become the next revolutionaries in astronautics: the development of nuclear propulsion engines will be carried out by the FSUE Keldysh Center. The general director of the enterprise, A. Koroteev, has already pleased the public that the preliminary design of the spacecraft for the new nuclear propulsion engine will be ready next year. The engine design should be ready by 2019, with testing scheduled for 2025.
The complex was called TEM - transport and energy module. It will carry a gas-cooled nuclear reactor. The direct propulsion system has not yet been decided: either it will be a jet engine like the RD-0410, or an electric rocket engine (ERE). However, the latter type has not yet been widely used anywhere in the world: only three spacecraft were equipped with them. But the fact that the reactor can power not only the engine, but also many other units, or even use the entire TEM as a space power plant, speaks in favor of the electric propulsion engine.
