Nuclear rocket engine Nuclear rocket engine. Jet technologies: "chemical" dead end
At the end of last year, the Russian Strategic Missile Forces tested a completely new weapon, the existence of which, as previously thought, was impossible. The nuclear-powered cruise missile, designated 9M730 by military experts, is precisely the new weapon that President Putin spoke about in his Address to the Federal Assembly. The test of the rocket was supposedly carried out at the Novaya Zemlya test site, tentatively at the end of autumn 2017, but the exact data will not be declassified soon. The developer of the rocket, also presumably, is the Novator Experimental Design Bureau (Yekaterinburg). According to competent sources, the rocket hit the target in the normal mode and the tests were recognized as completely successful. Further, alleged photographs of the launch (above) of a new missile with a nuclear power plant appeared in the media, and even indirect evidence related to the presence at the estimated time of testing in the immediate vicinity of the test site of the "flying laboratory" Il-976 LII Gromov with Rosatom marks. However, more questions emerged. Is the declared ability of the rocket to fly an unlimited range realistic and how is it achieved?
Characteristics of a cruise missile with a nuclear power plant
The characteristics of the nuclear-powered cruise missile that 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 knowledge:Length
- home- not less than 12 meters,
- marching- not less than 9 meters,
Rocket body diameter- about 1 meter,
Hull Width- about 1.5 meters,
tail height- 3.6 - 3.8 meters
The principle of operation of the Russian nuclear-powered cruise missile
The development of missiles with a nuclear power plant 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 simplified as follows: the nuclear reactor heats the mixture entering special containers (various options, from ammonia to hydrogen) with subsequent ejection through nozzles under high pressure. However, the version of the cruise missile that the Russian president spoke about does not fit any of the examples of designs being developed earlier.The fact is that, according to Putin, the missile has an almost unlimited flight range. This, of course, cannot be understood in such a way that a rocket 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 overlooked, is also associated with the declared unlimited flight range and, accordingly, the operation of the power unit of the cruise missile. For example, a heterogeneous thermal neutron reactor tested in the RD-0410 engine, which was developed by Kurchatov, Keldysh and Korolev, had a test life of only 1 hour, and in this case there can be no 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 is used for heating and subsequent ejection from the nozzle, which has a much more economical resource for spending over long distances. As an example, it can be a nuclear air-jet engine (NaVRD) of a completely new type, in which the working mass is atmospheric air injected into the working tanks by compressors, heated by a nuclear installation, and then ejected through nozzles.
It is also worth noting that the cruise missile with a nuclear power unit announced by Vladimir Putin is able to fly around the zones of active operation of air defense and missile defense systems, as well as keep the path to the target at low and ultra-low altitudes. This is possible only by equipping the missile with terrain-following systems that are resistant to interference created by enemy electronic warfare equipment.
Often in general educational publications on astronautics, the difference between a nuclear rocket engine (NRE) and a nuclear rocket electric propulsion system (NRE) is not distinguished. However, these abbreviations hide not only the difference in the principles of converting nuclear energy into rocket thrust, but also a very dramatic history of the development of astronautics.
The drama of the story lies in the fact that if the research on nuclear and nuclear power plants, which were stopped mainly for economic reasons, both in the USSR and in the USA, continued, then human flights to Mars would have become commonplace long ago.
It all started with atmospheric aircraft with a ramjet nuclear engine
Designers in the USA and the USSR considered "breathing" nuclear installations capable of drawing in outboard air and heating it to colossal temperatures. Probably, this principle of thrust generation was borrowed from ramjet engines, only instead of rocket fuel, the fission energy of atomic nuclei of uranium dioxide 235 was used.In the USA, such an engine was developed as part of the Pluto project. The Americans managed to create two prototypes of the new engine - Tory-IIA and Tory-IIC, on which the reactors were even turned on. The capacity of the plant was to be 600 megawatts.
The engines developed under the Pluto project were planned to be installed on cruise missiles, which were created in the 1950s under the designation SLAM (Supersonic Low Altitude Missile, supersonic low-altitude missile).
In the United States, they planned to build a rocket 26.8 meters long, three meters in diameter, and weighing 28 tons. The missile body was supposed to house a nuclear warhead, as well as a nuclear propulsion system with a length of 1.6 meters and a diameter of 1.5 meters. Against the background of other dimensions, the installation looked very compact, which explains its direct-flow principle of operation.
The developers believed that, thanks to the nuclear engine, the range of the SLAM rocket would be at least 182,000 kilometers.
In 1964, the US Department of Defense closed the project. The official reason was that in flight, a nuclear-powered cruise missile pollutes everything around too much. But in fact, the reason was the significant costs of maintaining such missiles, especially since by that time rocket science was rapidly developing based on liquid-propellant rocket engines, the maintenance of which was much cheaper.
The USSR remained true to the idea of creating a direct-flow NRE for much longer than the United States, closing the project only in 1985. But the results were much more significant. Thus, the first and only Soviet nuclear rocket engine was developed at the Khimavtomatika Design Bureau, Voronezh. This is RD-0410 (GRAU index - 11B91, also known as "Irbit" and "IR-100").
In RD-0410, a heterogeneous thermal neutron reactor was used, zirconium hydride served as a moderator, neutron reflectors were made of beryllium, nuclear fuel was a material based on uranium and tungsten carbides, enriched in the 235 isotope about 80%.
The design included 37 fuel assemblies covered with thermal insulation separating them from the moderator. The design provided that the hydrogen flow first passed through the reflector and moderator, maintaining their temperature at room temperature, and then entered the core, where it cooled the fuel assemblies, heating up to 3100 K. At the stand, the reflector and moderator were cooled by a separate hydrogen flow.
The reactor went through a significant series of tests, but was never tested for the full duration of operation. However, outside the reactor units were fully worked out.
Specifications RD 0410
Thrust in the void: 3.59 tf (35.2 kN)
Thermal power of the reactor: 196 MW
Specific thrust impulse in vacuum: 910 kgf s/kg (8927 m/s)
Number of inclusions: 10
Work resource: 1 hour
Fuel components: working fluid - liquid hydrogen, auxiliary substance - heptane
Weight with radiation protection: 2 tons
Engine dimensions: height 3.5 m, diameter 1.6 m.
Relatively small overall dimensions and weight, high temperature of nuclear fuel (3100 K) with an efficient hydrogen flow cooling system indicates that the RD0410 is an almost ideal prototype of a nuclear rocket engine for modern cruise missiles. And, taking into account modern technologies for obtaining self-stopping nuclear fuel, increasing the resource from an hour to several hours is a very real task.
Nuclear rocket engine designs
A nuclear rocket engine (NRE) is a jet engine in which the energy generated by a nuclear decay or fusion reaction heats the working fluid (most often hydrogen or ammonia).There are three types of NRE according to the type of fuel for the reactor:
- solid phase;
- liquid-phase;
- gas phase.
In gas-phase nuclear rocket engines, the fuel (for example, uranium) and the working fluid are in a gaseous state (in the form of plasma) and are held in the working area by an electromagnetic field. Heated to tens of thousands of degrees, uranium plasma transfers heat to the working fluid (for example, hydrogen), which, in turn, being heated to high temperatures, forms a jet.
According to the type of nuclear reaction, a radioisotope rocket engine, a thermonuclear rocket engine, and a nuclear engine proper (the energy of nuclear fission is used) are distinguished.
An interesting option is also a pulsed NRE - it is proposed to use a nuclear charge as an energy source (fuel). Such installations can be of internal and external types.
The main advantages of the YRD are:
- high specific impulse;
- significant energy reserve;
- compactness of the propulsion system;
- the possibility of obtaining very large thrust - tens, hundreds and thousands of tons in a vacuum.
- fluxes of penetrating radiation (gamma radiation, neutrons) during nuclear reactions;
- removal of highly radioactive compounds of uranium and its alloys;
- outflow of radioactive gases with the working fluid.
Nuclear power plant
Given that it is impossible to obtain any reliable information about nuclear power plants from publications, including from scientific articles, the principle of operation of such installations is best considered using examples of open patent materials, although they contain know-how.So, for example, the outstanding Russian scientist Anatoly Sazonovich Koroteev, the author of the invention under a patent, provided a technical solution for the composition of equipment for a modern nuclear power plant. Further I give a part of the specified patent document verbatim and without comments.
The essence of the proposed technical solution is illustrated by the diagram shown in the drawing. The nuclear power plant operating in the propulsion-energy mode contains an electric propulsion system (EPP) (for example, the diagram shows two electric rocket engines 1 and 2 with corresponding supply systems 3 and 4), a reactor plant 5, a turbine 6, a compressor 7, a generator 8, a heat exchanger-recuperator 9, a Rank-Hilsch vortex tube 10, a refrigerator-emitter 11. In this case, the turbine 6, the compressor 7 and the generator 8 are combined into a single unit - a turbogenerator-compressor. The nuclear power plant is equipped with pipelines 12 of the working fluid and electric lines 13 connecting the generator 8 and the electric propulsion system. The heat exchanger-recuperator 9 has the so-called high-temperature 14 and low-temperature 15 inputs of the working fluid, as well as high-temperature 16 and low-temperature 17 outlets of the working fluid.Links:The outlet of the reactor plant 5 is connected to the inlet of the turbine 6, the outlet of the turbine 6 is connected to the high-temperature inlet 14 of the heat exchanger-recuperator 9. The low-temperature outlet 15 of the heat exchanger-recuperator 9 is connected to the inlet to the Ranque-Hilsch vortex tube 10. The Ranque-Hilsch vortex tube 10 has two outputs , one of which (through the "hot" working fluid) is connected to the cooler-emitter 11, and the other (through the "cold" working fluid) is connected to the inlet of the compressor 7. The outlet of the cooler-emitter 11 is also connected to the inlet to the compressor 7. Compressor outlet 7 is connected to the low-temperature inlet 15 to the heat exchanger-recuperator 9. The high-temperature outlet 16 of the heat exchanger-recuperator 9 is connected to the inlet to the reactor plant 5. Thus, the main elements of the nuclear power plant are interconnected by a single circuit of the working fluid.
YaEDU works as follows. The working fluid heated in the reactor plant 5 is sent to the turbine 6, which ensures the operation of the compressor 7 and the generator 8 of the turbogenerator-compressor. Generator 8 generates electrical energy, which is sent through electrical lines 13 to electric rocket engines 1 and 2 and their supply systems 3 and 4, ensuring their operation. After leaving the turbine 6, the working fluid is sent through the high-temperature inlet 14 to the heat exchanger-recuperator 9, where the working fluid is partially cooled.
Then, from the low-temperature outlet 17 of the heat exchanger-recuperator 9, the working fluid is sent to the Rank-Hilsch vortex tube 10, inside which the working fluid flow is divided into "hot" and "cold" components. The "hot" part of the working fluid then goes to the cooler-emitter 11, where this part of the working fluid is effectively cooled. The “cold” part of the working fluid follows the inlet to the compressor 7, and after cooling, the part of the working fluid that leaves the cooler-radiator 11 follows there.
The compressor 7 supplies the cooled working fluid to the heat exchanger-recuperator 9 through the low-temperature inlet 15. This cooled working fluid in the heat exchanger-recuperator 9 provides partial cooling of the oncoming flow of the working fluid entering the heat exchanger-recuperator 9 from the turbine 6 through the high-temperature inlet 14. Further, The partially heated working fluid (due to heat exchange with the counter flow of the working fluid from the turbine 6) from the heat exchanger-recuperator 9 through the high-temperature outlet 16 again enters the reactor plant 5, the cycle is repeated again.
Thus, a single working fluid located in a closed loop ensures continuous operation of the nuclear power plant, and the use of a Rank-Hilsch vortex tube as part of the nuclear power plant in accordance with the proposed technical solution improves the weight and size characteristics of the nuclear power plant, increases the reliability of its operation, simplifies its design scheme and makes it possible to increase the efficiency of the nuclear power plant as a whole.
The first stage is denial
Robert Schmucker, a German expert in the field of rocket technology, considered V. Putin's statements to be completely implausible. “I can't imagine that the Russians can create a small flying reactor,” the expert said in an interview with Deutsche Welle.
They can, Herr Schmucker. Just imagine.
The first domestic satellite with a nuclear power plant (Kosmos-367) was launched from Baikonur back in 1970. 37 fuel assemblies of the small BES-5 Buk reactor, containing 30 kg of uranium, at a temperature in the primary circuit of 700°C and a heat release of 100 kW provided the electric power of the installation of 3 kW. The mass of the reactor is less than one ton, the estimated operating time is 120-130 days.
Experts will express doubts: this nuclear “battery” has too little power ... But! You look at the date: it was half a century ago.
Low efficiency - a consequence of thermionic conversion. With other forms of energy transfer, the indicators are much higher, for example, for nuclear power plants, the efficiency value is in the range of 32-38%. In this sense, the thermal power of the "space" reactor is of particular interest. 100 kW is a serious bid for victory.
It should be noted that the BES-5 Buk does not belong to the RTG family. Radioisotope thermoelectric generators convert the energy of the natural decay of atoms of radioactive elements and have negligible power. At the same time, the Buk is a real reactor with a controlled chain reaction.
The next generation of Soviet small-sized reactors, which appeared in the late 1980s, was distinguished by even smaller dimensions and greater energy release. This was the unique Topaz: compared to the Buk, the amount of uranium in the reactor was reduced by a factor of three (to 11.5 kg). Thermal power increased by 50% and amounted to 150 kW, the time of continuous operation reached 11 months (a reactor of this type was installed on board the Cosmos-1867 reconnaissance satellite).
Nuclear space reactors are an extraterrestrial form of death. In case of loss of control, the “shooting star” did not fulfill desires, but could release their sins to the “lucky ones”.
In 1992, the two remaining copies of the small Topaz series reactors were sold in the United States for $13 million.
The main question is: is there enough power for such installations to be used as rocket engines? By passing the working fluid (air) through the hot reactor core and obtaining thrust at the output according to the law of conservation of momentum.
Answer: no. Buk and Topaz are compact nuclear power plants. Other means are needed to create a YRD. But the general trend is visible to the naked eye. Compact nuclear power plants have long been created and exist in practice.
What power should a nuclear power plant have to be used as a main engine for a cruise missile similar in size to the Kh-101?
Can't find a job? Multiply time by power!
(Collection of universal tips.)
Finding power is also not difficult. N=F×V.
According to official data, the Xa-101 cruise missiles, as well as the KR of the Caliber family, are equipped with a short-life turbofan engine-50, which develops a thrust of 450 kgf (≈ 4400 N). Cruise missile cruising speed - 0.8 M, or 270 m / s. The ideal design efficiency of a turbojet bypass engine is 30%.
In this case, the required power of the cruise missile engine is only 25 times higher than the thermal power of the Topaz series reactor.
Despite the doubts of the German expert, the creation of a nuclear turbojet (or ramjet) rocket engine is a realistic task that meets the requirements of our time.
Rocket from hell
"It's all a surprise - a nuclear-powered cruise missile," said Douglas Barry, senior fellow at the International Institute for Strategic Studies in London. “This idea is not new, it was talked about in the 60s, but it faced a lot of obstacles.”
It was not only talked about. During tests in 1964, the Tori-IIC nuclear ramjet engine developed a thrust of 16 tons at a thermal power of the reactor of 513 MW. Simulating supersonic flight, the installation used up 450 tons of compressed air in five minutes. The reactor was designed very "hot" - the operating temperature in the core reached 1600°C. The design had very narrow tolerances: in a number of areas, the permissible temperature was only 150-200 ° C below the temperature at which the rocket elements melted and collapsed.
Were these indicators sufficient for the use of the YaPVRD as an engine in practice? The answer is obvious.
The nuclear ramjet engine developed more (!) thrust than the turbo-ramjet engine of the “three-wing” reconnaissance aircraft SR-71 “Black Bird”.
"Polygon-401", tests of a nuclear ramjet
The experimental facilities "Tori-IIA" and "-IIC" are prototypes of the nuclear engine of the SLAM cruise missile.
A diabolical invention, capable, according to calculations, of piercing 160,000 km of space at a minimum altitude at a speed of 3M. Literally “mowing down” everyone who met on her mournful path with a shock wave and a thunderous peal of 162 dB (deadly for a person).
The combat aircraft reactor did not have any biological protection. The eardrums ruptured after the SLAM flyby would seem like an insignificant circumstance against the background of radioactive emissions from the rocket nozzle. The flying monster left behind a plume more than a kilometer wide with a radiation dose of 200-300 rad. According to calculations, in one hour of flight, SLAM infected 1,800 square miles with deadly radiation.
According to calculations, the length of the aircraft could reach 26 meters. Starting weight - 27 tons. Combat load - thermonuclear charges, which were required to be successively dropped on several Soviet cities, along the missile's flight path. After completing the main task, SLAM was supposed to circle over the territory of the USSR for several more days, infecting everything around with radioactive emissions.
Perhaps the most deadly of all that man tried to create. Fortunately, it did not come to real launches.
The project, codenamed Pluto, was canceled on July 1, 1964. At the same time, according to one of the developers of SLAM, J. Craven, none of the military and political leadership of the United States regretted the decision.
The reason for abandoning the "low-flying nuclear missile" was the development of intercontinental ballistic missiles. Able to cause the necessary damage in less time with incomparable risks for the military themselves. As the authors of the publication in Air & Space magazine rightly noted: at least the ICBMs did not kill everyone who was near the launcher.
It is still unknown who, where and how planned to test the fiend. And who would be responsible if SLAM strayed off course and flew over Los Angeles. One of the crazy proposals suggested tying the rocket to a cable and driving in circles over deserted areas of the piece. Nevada. However, another question immediately arose: what to do with the rocket when the last remnants of fuel burned out in the reactor? The place where the SLAM will “land” will not be approached for centuries.
Life or death. Final Choice
Unlike the mystical “Pluto” from the 1950s, the project of a modern nuclear missile, voiced by V. Putin, offers the creation of an effective means for breaking through the American missile defense system. The means of mutually assured destruction is the most important criterion for nuclear deterrence.
The transformation of the classic "nuclear triad" into a diabolical "pentagram" - with the inclusion of a new generation of delivery vehicles (unlimited-range nuclear cruise missiles and Status-6 strategic nuclear torpedoes), coupled with the modernization of ICBM warheads (maneuvering "Avangard") is reasonable response to new threats. Washington's missile defense policy leaves Moscow no other choice.
“You are developing your anti-missile systems. The range of anti-missiles is increasing, the accuracy is increasing, these weapons are being improved. Therefore, we need to adequately respond to this so that we can overcome the system not only today, but also tomorrow, when you have new weapons.”
V. Putin in an interview with NBC.
The declassified details of the SLAM/Pluto experiments convincingly prove that the creation of a nuclear cruise missile was possible (technically feasible) six decades ago. Modern technologies allow us to bring the idea to a new technical level.
The sword rusts with promises
Despite the mass of obvious facts explaining the reasons for the appearance of the "superweapon of the president" and dispelling any doubts about the "impossibility" of creating such systems, in Russia, as well as abroad, there are many skeptics. "All of the listed weapons are just a means of information warfare." And then - a variety of proposals.
Probably, caricature "experts" such as I. Moiseev should not be taken seriously. The head of the Space Policy Institute (?), who told The Insider online edition: “You can’t put a nuclear engine on a cruise missile. Yes, and there are no such engines.
Attempts to "expose" the president's statements are also being made at a more serious analytical level. Such "investigations" immediately gain popularity among the liberal-minded public. Skeptics make the following arguments.
All the systems mentioned above are classified as strategic top-secret weapons, the existence of which cannot be verified or denied. (The message to the Federal Assembly itself showed computer graphics and footage of launches indistinguishable from tests of other types of cruise missiles.) At the same time, no one is talking, for example, about creating a heavy attack drone or a destroyer-class warship. A weapon that would soon have to be demonstrated to the whole world.
According to some "whistleblowers", the purely strategic, "secret" context of the messages may indicate their implausible nature. Well, if this is the main argument, then what is the argument with these people about?
There is also another point of view. Shocking about nuclear missiles and unmanned 100-knot submarines are made against the backdrop of the obvious problems of the military-industrial complex encountered in the implementation of simpler “traditional” weapons projects. Claims of missiles that at once surpassed all existing types of weapons stand in sharp contrast against the background of the well-known situation with rocket science. Skeptics cite mass failures during Bulava launches or the creation of the Angara launch vehicle, which has dragged on for two decades, as an example. Itself began in 1995; Speaking in November 2017, Deputy Prime Minister D. Rogozin promised to resume launches of the Angara from the Vostochny Cosmodrome only in ... 2021.
And, by the way, why was Zircon, the main naval sensation of the previous year, left without attention? A hypersonic missile that can cross out all existing concepts of naval combat.
The news about the arrival of laser systems in the troops attracted the attention of manufacturers of laser systems. Existing examples of directed energy weapons were created on an extensive basis of research and development of high-tech equipment for the civilian market. For example, the American AN/SEQ-3 LaWS shipborne installation represents a “package” of six welding lasers with a total power of 33 kW.
The announcement of the creation of a super-powerful combat laser contrasts against the backdrop of a very weak laser industry: Russia is not one of the world's largest manufacturers of laser equipment (Coherent, IPG Photonics or the Chinese Han "Laser Technology). Therefore, the sudden appearance of high-power laser weapons causes genuine interest among specialists .
There are always more questions than answers. The devil is in the details, but official sources give an extremely poor idea of the latest weapons. Often it is not even clear whether the system is already ready for adoption, or its development is at a certain stage. The well-known precedents associated with the creation of such weapons in the past indicate that the problems arising from this are not solved at the snap of a finger. Fans of technical innovations are concerned about the choice of a place for testing a spacecraft with a nuclear engine. Or ways to communicate with the Status-6 underwater drone (a fundamental problem: radio communication does not work underwater, submarines are forced to rise to the surface during communication sessions). It would be interesting to hear an explanation about how to use it: compared to traditional ICBMs and SLBMs, which can start and end a war within an hour, Status-6 will take several days to reach the US coast. When no one else is there!
The last fight is over.
Is anyone left alive?
In response - only the wind howl ...
Using materials:
Air&Space Magazine (April-May 1990)
The Silent War by John Craven
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 uranium acts as a fuel instead of coal and firewood, and hydrogen acts as a working fluid. Is the NRE (nuclear jet engine) so unpromising? Let's try to figure it out.
First rockets
All the merits of mankind in the development 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 a chemical reaction of fuel combustion in an oxidizer into the kinetic energy of a jet stream, and, consequently, a rocket. The fuel used is kerosene, liquid hydrogen, heptane (for liquid-fuel rocket engines (LTE)) and a polymerized mixture of ammonium perchlorate, aluminum and iron oxide (for solid propellant (RDTT)).
It is well known that the first rockets used for fireworks appeared in China as early as 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), the Polish general Kazimir Semenovich (1650), the Russian lieutenant general Alexander Zasyadko made a significant contribution to the development of rocket technology.
A patent for the invention of the first liquid-propellant rocket engine was received by an American scientist Robert Goddard. His apparatus, with a weight of 5 kg and a length of about 3 m, running on gasoline and liquid oxygen, in 1926 for 2.5 s. flew 56 meters.
In pursuit of 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. Zander are considered to be the pioneers of rocket engine building. With their participation, the power units RD-107 and RD-108 were developed, which provided the USSR with the championship in space exploration and laid the foundation for Russia's future leadership in the field of manned space exploration.
With the modernization of the liquid-propellant 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 the near-Earth space, but flights to other planets, and even more stars, will remain an unrealizable dream for mankind. As a result, already in the middle of the last century, projects of alternative (non-chemical) rocket engines began to appear. The most popular and promising were installations that use the energy of nuclear reactions. The first experimental samples of nuclear space engines (NRE) in the Soviet Union and the USA were tested in 1970. However, after the Chernobyl disaster, under pressure from the public, work in this area was suspended (in the USSR in 1988, in the USA - since 1994).
The functioning of nuclear power plants is based on the same principles as those of 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 is much higher than 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 Po210 polonium isotopes this value is 5 × 1011 J.
The released energy in a nuclear engine can be used in a variety of ways:
heating the working fluid emitted through the nozzles, as in a traditional rocket engine, after being converted into an electric one, ionizing and accelerating the particles of the working fluid, creating an impulse directly by fission or fusion 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 NRE with a solid-phase fission reactor, which uses fuel rods (fuel elements) used in nuclear power plants as fuel. The first such engine in the framework of the American project Nerva passed ground test tests in 1966, having worked for about two hours.
Design features
At the heart of any nuclear space engine is a reactor consisting of an active zone and a beryllium reflector placed in a power building. It is in the active zone that the fission of the atoms of the combustible substance occurs, as a rule, uranium U238, enriched with U235 isotopes. To give the process of nuclear decay certain properties, moderators are also located here - refractory tungsten or molybdenum. If the moderator is included in the composition of fuel elements, the reactor is called homogeneous, and if placed separately - 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, experiencing high thermal loads, are cooled by the working fluid, which is then injected into the fuel assemblies by a turbopump unit. Here it is heated to almost 3000˚С. Expiring through the nozzle, the working fluid creates jet thrust.
Typical reactor controls are control rods and rotary drums made of a substance that absorbs neutrons (boron or cadmium). The rods are placed directly in the core or in special niches of the reflector, 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 of time is changed, adjusting 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, elements of the primary reactor protection are placed in the power building.
Improving Efficiency
A liquid-phase nuclear engine is similar in principle and device 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 (LTE and solid propellant rocket engines) the maximum specific impulse (jet blast velocity) is 5,420 m/s, for solid-phase nuclear and 10,000 m/s it is far from the limit, then the average value of this indicator for gas-phase NRE 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 takes place inside a plasma cloud from a working fluid held by an electromagnetic field and absorbing all the generated heat. The temperature 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 radiated energy. In installations of the second type, the reaction temperature will be limited by the melting point of the bulb material. At the same time, the energy efficiency of a nuclear space engine decreases somewhat (specific impulse up to 15,000 m/s), but efficiency and radiation safety increase.
Practical achievements
Formally, the American scientist and physicist Richard Feynman is considered to be the inventor of the atomic power plant. The start of large-scale work on the development and creation of nuclear engines for spacecraft within the framework of the Rover program was given at the Los Alamos Research Center (USA) in 1955. American inventors preferred plants with a homogeneous nuclear reactor. The first experimental sample of "Kiwi-A" was assembled at the plant at the atomic center in Albuquerque (New Mexico, USA) and tested in 1959. The reactor was placed vertically on the stand with the nozzle up. During the tests, a heated jet of spent hydrogen was emitted 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 to such research was given by the meeting of the "three great K" held in 1959 at the Institute of Atomic Energy - the creator of the atomic bomb I.V. Kurchatov, the main theorist of Russian cosmonautics M.V. Keldysh and the general designer of Soviet missiles 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 the city of 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, the lack of human and financial resources.
For a note: an important practical achievement was the conduct of flight tests of aircraft with a nuclear engine. In the USSR, the experimental strategic bomber Tu-95LAL was the most promising, in the USA - the B-36.
Orion Project or Pulse NREs
For flights in space, a pulsed nuclear engine was first proposed to be used in 1945 by an American mathematician of Polish origin, Stanislav 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, gives it a great acceleration.
In the course of the Orion project, which started in 1958, it was planned to equip a rocket capable of delivering people to the surface of Mars or the orbit of Jupiter with just such an engine. The crew stationed in the forward compartment would be protected from the damaging effects of gigantic accelerations by a damping device. The result of detailed engineering work was march tests of a large-scale model of the ship to study the stability of the flight (conventional explosives were used instead of nuclear charges). Due to the high cost, the project was closed in 1965.
Similar ideas for creating an "explosive" were expressed by the Soviet academician A. Sakharov in July 1961. To put the ship into orbit, the scientist proposed using conventional liquid-propellant engines.
Alternative projects
A huge number of projects have not gone beyond theoretical research. Among them were many original and very promising. Confirmation is the idea of a nuclear power plant based on fissile fragments. The design features and arrangement of this engine make it possible to do without a working fluid at all. The jet stream, which provides the necessary propulsion characteristics, is formed from spent nuclear material. The reactor is based on rotating disks with a subcritical nuclear mass (the fission coefficient of atoms is less than one). When rotating in the sector of the disk located in the active zone, a chain reaction is started and decaying high-energy atoms are sent to the engine nozzle, forming a jet stream. The surviving whole 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 not very promising for interplanetary, and even more so interstellar flights.
Nuclear fusion engines have huge potential. Already at the current stage of the development of science and technology, a pulse 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 YARD
The indisputable advantages of using nuclear engines as power units for spacecraft include their high energy efficiency, which provides a high specific impulse and good traction performance (up to a thousand tons in vacuum), an impressive energy reserve 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 the NRE, which caused the curtailment of design and research work, is a high radiation hazard. This is especially true when conducting ground fire tests, as a result of which radioactive gases, compounds of uranium and its isotopes may enter the atmosphere together with the working fluid, and the destructive effect of penetrating radiation. For the same reasons, it is unacceptable to launch a spacecraft equipped with a nuclear engine directly from the Earth's surface.
Present and future
Anatoly Koroteev, Academician of the Russian Academy of Sciences, General Director of the Keldysh Center, assured that 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 the direct heating of the working fluid and the formation of a jet stream, but to generate electricity. The role of propulsor in the installation is assigned to the plasma engine, the specific thrust of which is 20 times higher than the thrust of currently existing chemical rocket vehicles. The head enterprise of the project is a subdivision of the state corporation "Rosatom" JSC "NIKIET" (Moscow).
Full-scale mock-up tests were successfully passed back in 2015 on the basis of NPO Mashinostroeniya (Reutov). November of this year has been named as the start date for flight design tests of the nuclear power plant. The most important elements and systems will have to be tested, including on board the ISS.
The operation of the new Russian nuclear engine occurs in a closed cycle, which completely excludes the ingress of radioactive substances into the surrounding space. The mass and overall characteristics of the main elements of the power plant ensure its use with existing domestic Proton and Angara launch vehicles.
Russia has been and still remains a leader in the field of nuclear space energy. Organizations such as RSC Energia and Roskosmos have experience in designing, building, launching and operating 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, the delivery of a research apparatus to the orbits of the outer planets of the solar system requires an increase in the resource of such a nuclear installation to 5-7 years. It has been proved 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 of artificial satellites of the most distant planets, planetary rovers to the surface of natural satellites of these planets and delivery 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 to ensure large annual cargo flows. An example would be the Moon exploration program with the creation and maintenance of a constantly growing habitable base and experimental technological and industrial complexes.
Calculation of cargo turnover
According to the design studies of RSC Energia, during the construction of the base, modules weighing about 10 tons should be delivered to the Moon's surface, up to 30 tons into the Moon's orbit. , and the annual cargo flow to ensure the functioning and development of the base is 400-500 tons.
However, the principle of operation of a nuclear engine does not allow to disperse the transporter quickly enough. Due to the long time of transportation and, accordingly, the significant time spent by the payload in the radiation belts of the Earth, not all cargo can be delivered using nuclear-powered tugs. Therefore, the cargo flow that can be ensured on the basis of NEP is estimated at only 100-300 tons/year.
Economic efficiency
As a criterion for the economic efficiency of the interorbital transport system, it is advisable to use the value of the specific cost of transporting a unit mass of payload (PG) from the Earth's surface to the target orbit. RSC Energia developed an economic and mathematical model that takes into account the main cost components in the transport system:
- for the creation and launch of tug modules into orbit;
- 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 nuclear propulsion propulsion with a power of about 1 MW and a disposable tug based on advanced liquid propulsion systems was studied in the program for delivering a payload with a total mass of 100 t/year from the Earth to the Moon's orbit with a height of 100 km. When using the same launch vehicle with a carrying capacity equal to the carrying capacity of the Proton-M launch vehicle and a two-launch scheme for constructing a transport system, the unit cost of delivering a unit mass of payload using a nuclear-powered tug will be three times lower than when using disposable tugboats based on rockets with liquid engines of the DM-3 type.
Output
An efficient nuclear engine for space contributes to solving the environmental problems of the Earth, manned flight to Mars, creating a system of wireless power transmission in space, implementing with increased safety the burial in space of especially dangerous radioactive waste from ground-based nuclear energy, creating a habitable lunar base and starting industrial exploration of the Moon, ensuring protection of the Earth from asteroid-comet danger.
