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

The practical creation of nuclear rocket engines (NRE) was carried out only by the USSR and the USA. In 1955, the United States began implementing the Rover program to develop a nuclear rocket engine for spacecraft. Three years later, in 1958, NASA became involved in the project, which set a specific task for ships with nuclear propulsion engines - a flight to the Moon and Mars. From that time on, the program began to be called NERVA, which stands for “nuclear engine for installation on rockets.”

By the mid-70s, within the framework of this program, it was planned to design a nuclear rocket engine with a thrust of about 30 tons (for comparison, the typical thrust of liquid rocket engines of that time was approximately 700 tons), but with a gas exhaust speed of 8.1 km/s. However, in 1973 the program was closed due to a shift in US interests towards the space shuttle.

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

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

In July 1961, Soviet academician Andrei Sakharov announced the nuclear explosion project at a meeting of leading nuclear scientists in the Kremlin. The blaster had conventional liquid rocket engines for takeoff, but in space it was supposed to detonate small nuclear charges. The fission products generated during the explosion transferred their momentum to the ship, causing it to fly. However, on August 5, 1963, a test ban agreement was signed in Moscow nuclear weapons in the atmosphere, outer space and under water. This was the reason for the closure of the nuclear explosion program.

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

Nuclear rocket engine design

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 nuclear propulsion engines depending on the type of fuel for the reactor:

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

The most complete is solid phase engine option. The figure shows a diagram of the simplest nuclear powered engine with a solid nuclear fuel reactor. The working fluid is located in an external tank. Using a pump, it is supplied to the engine chamber. In the chamber, the working fluid is sprayed using nozzles and comes into contact with the fuel-generating nuclear fuel. When heated, it expands and flies out of the chamber through the nozzle at great speed.

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

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

Based on the type of nuclear reaction, a distinction is made between a radioisotope rocket engine, a thermonuclear rocket engine and a nuclear engine itself (the energy of nuclear fission is used).

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

The main advantages of nuclear powered engines are:

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

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

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

Therefore launch nuclear engine unacceptable for launches from the Earth's surface due to the risk of radioactive contamination.

A safe way to use nuclear energy in space was invented in the USSR, and work is now underway to create a nuclear installation based on it, said the General Director of the State scientific center Russian Federation "Research Center named after Keldysh", academician Anatoly Koroteev.

“Now the institute is actively working in this direction in large cooperation between Roscosmos and Rosatom enterprises. And I hope that in due time we will get a positive effect here,” A. Koroteev said at the annual “Royal Readings” at the Bauman Moscow State Technical University on Tuesday.

According to him, the Keldysh Center has invented a scheme for the safe use of nuclear energy in outer space, which makes it possible to do without emissions and operates in a closed circuit, which makes the installation safe even if it fails and falls to Earth.

“This scheme greatly reduces the risk of using nuclear energy, especially considering that one of the fundamental points is the operation of this system in orbits above 800-1000 km. Then, in case of failure, the “flashing” time is such that it makes it safe for these elements to return to Earth after a long period of time,” the scientist clarified.

A. Koroteev said that previously the USSR had already used spacecraft powered by nuclear energy, but they were potentially dangerous for the Earth, and subsequently had to be abandoned. “The USSR used nuclear energy in space. There were 34 spacecraft with nuclear energy in space, of which 32 were Soviet and two American,” the academician recalled.

According to him, the nuclear installation being developed in Russia will be made lighter through the use of a frameless cooling system, in which the nuclear reactor coolant will circulate directly in outer space without a pipeline system.

But back in the early 1960s, designers considered nuclear rocket engines as the only real alternative for traveling to other planets in the solar system. Let's find out the history of this issue.

The competition between the USSR and the USA, including in space, was going on at that time in full swing, engineers and scientists entered the race to create a nuclear propulsion engine, and the military also initially supported the nuclear rocket engine project. At first, the task seemed very simple - you just need to make a reactor designed to be cooled with hydrogen rather than water, attach a nozzle to it, and - forward to Mars! The Americans were going to Mars ten years after the Moon and could not even imagine that astronauts would ever reach it without nuclear engines.

The Americans very quickly built the first prototype reactor and already tested it in July 1959 (they were called KIWI-A). These tests merely showed that the reactor could be used to heat hydrogen. The reactor design - with unprotected uranium oxide fuel - was not suitable for high temperatures, and the hydrogen only heated up to one and a half thousand degrees.

As experience was gained, the design of reactors for nuclear rocket engines - NRE - became more complex. The uranium oxide was replaced with a more heat-resistant carbide, in addition it was coated with niobium carbide, but when trying to reach the design temperature, the reactor began to collapse. Moreover, even in the absence of macroscopic destruction, diffusion of uranium fuel into cooling hydrogen occurred, and mass loss reached 20% within five hours of reactor operation. A material capable of operating at 2700-3000 0 C and resisting destruction by hot hydrogen has never been found.

Therefore, the Americans decided to sacrifice efficiency and included specific impulse in the flight engine design (thrust in kilograms of force achieved with the release of one kilogram of working fluid mass every second; the unit of measurement is a second). 860 seconds. This was twice the corresponding figure for oxygen-hydrogen engines of that time. But when the Americans began to succeed, interest in manned flights had already fallen, the Apollo program was curtailed, and in 1973 the NERVA project (that was the name of the engine for a manned expedition to Mars) was finally closed. Having won the lunar race, the Americans did not want to organize a Martian race.

But the lessons learned from a dozen reactors built and several dozen tests carried out were that American engineers were too carried away with full-scale nuclear tests, rather than working out key elements without involving nuclear technology where this can be avoided. And where it is not possible, use smaller stands. The Americans ran almost all the reactors at full power, but were unable to reach the design temperature of hydrogen - the reactor began to collapse earlier. In total, from 1955 to 1972, $1.4 billion was spent on the nuclear rocket engine program - approximately 5% of the cost of the lunar program.

Also in the USA, the Orion project was invented, which combined both versions of the nuclear propulsion system (jet and pulse). 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 payload.

It even went as far as 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.

In the first half of the 1960s, Soviet engineers viewed the expedition to Mars as a logical continuation of the then-developed program of manned flight to the Moon. In the wake of the enthusiasm caused by the USSR's priority in space, even such extremely complex problems were assessed with increased optimism.

One of the most important problems was (and remains to this day) the problem of power supply. It was clear that liquid-propellant rocket engines, even promising oxygen-hydrogen ones, could, in principle, provide a manned flight to Mars, then only with huge launch masses of the interplanetary complex, with a large number of dockings of individual blocks in the assembly low-Earth orbit.

Looking for optimal solutions Scientists and engineers turned to nuclear energy, gradually taking a closer look at this problem.

In the USSR, research on the problems of using nuclear energy in rocket and space technology began in the second half of the 50s, even before the launch of the first satellites. Small groups of enthusiasts emerged in several research institutes with the goal of creating rocket and space nuclear engines and power plants.

The designers of OKB-11 S.P. Korolev, together with specialists from NII-12 under the leadership of V.Ya. Likhushin, considered several options for space and combat (!) rockets equipped with nuclear rocket engines (NRE). Water and liquefied gases - hydrogen, ammonia and methane - were evaluated as the working fluid.

The prospect was promising; gradually the work found understanding and financial support in the USSR government.

Already the very first analysis showed that among the many possible schemes of space nuclear power propulsion systems (NPS), three have the greatest prospects:

• with a solid-phase nuclear reactor;
• with a gas-phase nuclear reactor;
• electronuclear rocket propulsion systems.

The schemes were fundamentally different; For each of them, several options were outlined for the development of theoretical and experimental work.

The closest to implementation seemed to be a solid-phase nuclear propulsion engine. The impetus for the development of work in this direction was provided by similar developments carried out in the USA since 1955 under the ROVER program, as well as the prospects (as it seemed then) of creating a domestic intercontinental manned bomber aircraft with a nuclear propulsion system.

A solid-phase nuclear propulsion engine operates as a direct-flow engine. Liquid hydrogen enters the nozzle part, cools the reactor vessel, fuel assemblies (FA), moderator, and then turns around and enters the FA, where it heats up to 3000 K and is thrown into the nozzle, accelerating to high speeds.

The operating principles of the nuclear engine were not in doubt. However, its design (and characteristics) largely depended on the “heart” of the engine – the nuclear reactor and were determined, first of all, by its “filling” – the core.

The developers of the first American (and Soviet) nuclear engines stood for a homogeneous reactor with a graphite core. The work of the search group on new types of high-temperature fuels, created in 1958 in laboratory No. 21 (headed by G.A. Meerson) of NII-93 (director by A.A. Bochvar), proceeded somewhat separately. Influenced by the ongoing work on an aircraft reactor (a honeycomb of beryllium oxide) at that time, the group made attempts (again exploratory) to obtain materials based on silicon and zirconium carbide that were resistant to oxidation.

According to the memoirs of R.B. Kotelnikov, an employee of NII-9, in the spring of 1958, the head of laboratory No. 21 had a meeting with a representative of NII-1, V.N. Bogin. He said that as the main material for the fuel elements (fuel rods) of the reactor in their institute (by the way, at that time the leading one in the rocket industry; head of the institute V.Ya. Likhushin, scientific director M.V. Keldysh, head of the laboratory V.M. .Ievlev) use graphite. In particular, they have already learned how to apply coatings to samples to protect them from hydrogen. NII-9 proposed to consider the possibility of using UC-ZrC carbides as the basis for fuel elements.

Later short time Another customer for fuel rods appeared - the Design Bureau of M.M. Bondaryuk, which ideologically competed with NII-1. If the latter stood for a multi-channel all-block design, then the Design Bureau of M.M. Bondaryuk headed for a collapsible plate version, focusing on the ease of machining of graphite and not being embarrassed by the complexity of the parts - millimeter-thick plates with the same ribs. Carbides are much more difficult to process; at that time it was impossible to make parts such as multi-channel blocks and plates from them. The need to create some other design corresponding to the specifics of carbides became clear.

At the end of 1959 - beginning of 1960, the decisive condition for NRE fuel rods was found - a rod type core, satisfying the customers - the Likhushin Research Institute and the Bondaryuk Design Bureau. The design of a heterogeneous reactor using thermal neutrons was justified as the main one for them; its main advantages (compared to the alternative homogeneous graphite reactor) are:

• it is possible to use a low-temperature hydrogen-containing moderator, which makes it possible to create nuclear propulsion engines with high mass perfection;
• it is possible to develop a small-sized prototype of a nuclear propulsion engine with a thrust of about 30...50 kN with a high degree of continuity for engines and nuclear propulsion systems of the next generation;
• it is possible to widely use refractory carbides in fuel rods and other parts of the reactor structure, which makes it possible to maximize the heating temperature of the working fluid and provide an increased specific impulse;
• it is possible to autonomously test, element by element, the main components and systems of the nuclear propulsion system (NPP), such as fuel assemblies, moderator, reflector, turbopump unit (TPU), control system, nozzle, etc.; this allows testing to be carried out in parallel, reducing the amount of expensive complex testing of the power plant as a whole.

Around 1962–1963 Work on the nuclear propulsion problem was headed by NII-1, which has a powerful experimental base and excellent personnel. They only lacked uranium technology, as well as nuclear scientists. With the involvement of NII-9, and then IPPE, a cooperation was formed, which took as its ideology the creation of a minimum thrust (about 3.6 tf), but “real” summer engine with a “straight-through” reactor IR-100 (test or research, 100 MW, chief designer - Yu.A. Treskin). Supported by government regulations, NII-1 built electric arc stands that invariably amazed the imagination - dozens of 6-8 m high cylinders, huge horizontal chambers with a power of over 80 kW, armored glass in boxes. Meeting participants were inspired by colorful posters with flight plans to the Moon, Mars, etc. It was assumed that in the process of creating and testing the nuclear propulsion engine, design, technological, and physical issues would be resolved.

According to R. Kotelnikov, the matter, unfortunately, was complicated by the not very clear position of the rocket scientists. The Ministry of General Engineering (MOM) had great difficulties in financing the testing program and the construction of the test bench base. It seemed that the IOM did not have the desire or capacity to advance the NRD program.

By the end of the 1960s, support for NII-1's competitors - IAE, PNITI and NII-8 - was much more serious. The Ministry of Medium Engineering ("nuclear scientists") actively supported their development; the IVG “loop” reactor (with a core and rod-type central channel assemblies developed by NII-9) eventually came to the fore by the beginning of the 70s; testing of fuel assemblies began there.

Now, 30 years later, it seems that the IAE line was more correct: first - a reliable “earthly” loop - testing of fuel rods and assemblies, and then the creation of a flight nuclear propulsion engine of the required power. But then it seemed that it was possible to very quickly make a real engine, albeit a small one... However, since life has shown that there was no objective (or even subjective) need for such an engine (to this we can also add that the seriousness of the negative aspects of this direction, for example international agreements on nuclear devices in space, was at first greatly underestimated), then the fundamental program, the goals of which were not narrow and specific, turned out to be correspondingly more correct and productive.

On July 1, 1965, the preliminary design of the IR-20-100 reactor was reviewed. The culmination was the release of the technical design of the IR-100 fuel assemblies (1967), consisting of 100 rods (UC-ZrC-NbC and UC-ZrC-C for the inlet sections and UC-ZrC-NbC for the outlet). NII-9 was ready to produce a large batch of core elements for the future IR-100 core. The project was very progressive: after about 10 years, practically without significant changes, it was used in the area of ​​​​the 11B91 apparatus, and even now all the main solutions are preserved in assemblies of similar reactors for other purposes, with a completely different degree of calculation and experimental justification.

The “rocket” part of the first domestic nuclear RD-0410 was developed at the Voronezh Design Bureau of Chemical Automation (KBHA), the “reactor” part (neutron reactor and radiation safety issues) - by the Institute of Physics and Energy (Obninsk) and the Kurchatov Institute of Atomic Energy.

KBHA is known for its work in the field of liquid propellant engines for ballistic missiles, spacecraft and launch vehicles. About 60 samples were developed here, 30 of which were brought to mass production. By 1986, KBHA had created the country's most powerful single-chamber oxygen-hydrogen engine RD-0120 with a thrust of 200 tf, which was used as a propulsion engine in the second stage of the Energia-Buran complex. Nuclear RD-0410 was created jointly with many defense enterprises, design bureaus and research institutes.

According to the accepted concept, liquid hydrogen and hexane (an inhibitory additive that reduces the hydrogenation of carbides and increases the life of fuel elements) were supplied using a TNA into a heterogeneous thermal neutron reactor with fuel assemblies surrounded by a zirconium hydride moderator. Their shells were cooled with hydrogen. The reflector had drives for rotating the absorption elements (boron carbide cylinders). The pump included a three-stage centrifugal pump and a single-stage axial turbine.

In five years, from 1966 to 1971, the foundations of reactor-engine technology were created, and a few years later a powerful experimental base called “expedition No. 10” was put into operation, subsequently the experimental expedition of NPO “Luch” at the Semipalatinsk nuclear test site .
Particular difficulties were encountered during testing. It was impossible to use conventional stands for launching a full-scale nuclear rocket engine due to radiation. It was decided to test the reactor at the nuclear test site in Semipalatinsk, and the “rocket part” at NIIkhimmash (Zagorsk, now Sergiev Posad).

To study intra-chamber processes, more than 250 tests were performed on 30 “cold engines” (without a reactor). As a model heating element The combustion chamber of the oxygen-hydrogen rocket engine 11D56 developed by KBkhimmash (chief designer - A.M. Isaev) was used. Maximum time operating time was 13 thousand seconds with an declared resource of 3600 seconds.

To test the reactor at the Semipalatinsk test site, two special shafts with underground service premises were built. One of the shafts was connected to an underground reservoir for compressed hydrogen gas. The use of liquid hydrogen was abandoned for financial reasons.

In 1976, the first power start-up of the IVG-1 reactor was carried out. At the same time, the OE created a stand for testing the “propulsion” version of the IR-100 reactor, and a few years later it was tested at different powers (one of the IR-100s was subsequently converted into a low-power materials science research reactor, which is still operating).

Before the experimental launch, the reactor was lowered into the shaft using a surface-mounted gantry crane. After starting the reactor, hydrogen entered the “boiler” from below, heated up to 3000 K and burst out of the shaft in a fiery stream. Despite the insignificant radioactivity of the escaping gases, it was not allowed to be outside within a radius of one and a half kilometers from the test site during the day. It was impossible to approach the mine itself for a month. A one and a half kilometer underground tunnel led from the safe zone first to one bunker, and from there to another, located near the mines. The specialists moved along these unique “corridors.”

Ievlev Vitaly Mikhailovich

The results of experiments carried out with the reactor in 1978–1981 confirmed the correctness of the design solutions. In principle, the YARD was created. All that remained was to connect the two parts and conduct comprehensive tests.

Around 1985, RD-0410 (according to a different designation system 11B91) could have made its first space flight. But for this it was necessary to develop accelerating block based on it. Unfortunately, this work was not ordered to any space design bureau, and there are many reasons for this. The main one is the so-called Perestroika. Rash steps led to the fact that the entire space industry instantly found itself “in disgrace” and in 1988, work on nuclear propulsion in the USSR (then the USSR still existed) was stopped. This happened not because of technical problems, but for momentary ideological reasons. And in 1990 he died ideological inspirer nuclear propulsion programs in the USSR Vitaly Mikhailovich Ievlev...

What major successes have the developers achieved in creating the “A” nuclear power propulsion system?

More than one and a half dozen full-scale tests were carried out on the IVG-1 reactor, and the following results were obtained: maximum hydrogen temperature - 3100 K, specific impulse - 925 sec, specific heat release up to 10 MW/l, total resource more than 4000 sec with consecutive 10 reactor starts. These results significantly exceed American achievements in graphite zones.

It should be noted that during the entire testing period of the nuclear propulsion engine, despite the open exhaust, the yield of radioactive fission fragments did not exceed acceptable standards neither at the test site nor outside it and was not registered in the territory of neighboring states.

The most important result of the work was the creation of domestic technology for such reactors, the production of new refractory materials, and the fact of creating a reactor-engine gave rise to a number of new projects and ideas.

Although further development such nuclear powered engines were suspended, the achievements obtained are unique not only in our country, but also in the world. This has been repeatedly confirmed in recent years at international symposiums on space energy, as well as at meetings of domestic and American specialists (at the latter it was recognized that the IVG reactor stand is the only operational test apparatus in the world today, which can play an important role in experimental development FA and nuclear power plants).

sources
http://newsreaders.ru
http://marsiada.ru
http://vpk-news.ru/news/14241

The original article is on the website InfoGlaz.rf Link to the article from which this copy was made -

Sergeev Alexey, 9 “A” class, Municipal Educational Institution “Secondary School No. 84”

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

Head: , physics teacher, Municipal Educational Institution “Secondary School No. 84” CATO Seversk

Introduction

Propulsion systems on board a spacecraft are designed to create thrust or momentum. According to the type of thrust used, the propulsion system is divided into chemical (CHRD) and non-chemical (NCRD). CRDs are divided into liquid propellant engines (LPRE), solid propellant rocket engines (solid propellant engines) and combined rocket engines (RCR). In turn, non-chemical propulsion systems are divided into nuclear (NRE) and electric (EP). The great scientist Konstantin Eduardovich Tsiolkovsky a century ago created the first model of a propulsion system that worked on solid and liquid fuel. Afterwards, in the second half of the 20th century, thousands of flights were carried out using mainly liquid propellant engines and solid propellant rocket engines.

However, at present, for flights to other planets, not to mention the stars, the use of liquid propellant rocket engines and solid propellant rocket engines is becoming increasingly unprofitable, although many rocket engines have been developed. Most likely, the capabilities of liquid propellant rocket engines and solid propellant rocket engines have completely exhausted themselves. The reason here is that the specific impulse of all chemical thrusters is low and does not exceed 5000 m/s, which requires long-term operation of the thruster and, accordingly, large reserves of fuel for the development of sufficiently high speeds, or, as is customary in astronautics, the necessary large values Tsiolkovsky number, i.e. the ratio of the mass of a fueled rocket to the mass of an empty one. Thus, the Energia launch vehicle, which launches 100 tons of payload into low orbit, has a launch mass of about 3,000 tons, which gives the Tsiolkovsky number a value within 30.

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

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

1.Basic concepts

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

Classification of propulsion systems

2. Purpose of rocket engines

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

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

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

Engines for space flights differ from those on Earth in that they must produce as much power as possible with the smallest possible mass and volume. In addition, they are subject to such requirements as exceptionally high efficiency and reliability, and significant operating time. Based on the type of energy used, spacecraft propulsion systems are divided into four types: thermochemical, nuclear, electric, solar-sail. Each of the listed types has its own advantages and disadvantages and can be used in certain conditions.

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

3.Thermochemical rocket engines.

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

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

Fuel and oxidizer for liquid jet engines are stored separately in special tanks and supplied to the combustion chamber using pumps. When they are combined in the combustion chamber, temperatures reach 3000 – 4500 °C.

Combustion products, expanding, acquire speeds from 2500 to 4500 m/s. Pushing off from the engine body, they create jet thrust. At the same time, the greater the mass and speed of gas flow, the greater the thrust of the engine.

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

The commonly used liquid rocket engine circuit works as follows. Compressed gas creates the necessary pressure in tanks with cryogenic fuel to prevent the occurrence of gas bubbles in pipelines. Pumps supply fuel to rocket engines. Fuel is injected into the combustion chamber through a large number of injectors. An oxidizer is also injected into the combustion chamber through the nozzles.

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

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

4. Electric rocket engines

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

5.Other types of engines

There are also more exotic designs for nuclear rocket engines, in which the fissile material is in a liquid, gaseous or even plasma state, but the implementation of such designs is difficult. modern level technology and technology is unrealistic. The following rocket engine projects exist, still at the theoretical or laboratory stage:

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

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

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

6.Nuclear rocket engines

One of the main disadvantages of rocket engines running on liquid fuel is associated with the limited flow rate of gases. In nuclear rocket engines, it seems possible to use the colossal energy released during the decomposition of nuclear “fuel” to heat the working substance. The operating principle of nuclear rocket engines is almost no different from the operating principle of thermochemical engines. The difference is that the working fluid is heated not due to its own chemical energy, but due to “extraneous” energy released during an intranuclear reaction. The working fluid is passed through a nuclear reactor, in which the fission reaction of atomic nuclei (for example, uranium) occurs, and is heated. Nuclear rocket engines eliminate the need for an oxidizer and therefore only one liquid can be used. As a working fluid, it is advisable to use substances that allow the engine to develop greater traction force. This condition is most fully satisfied by hydrogen, followed by ammonia, hydrazine and water. The processes in which nuclear energy is released are divided into radioactive transformations, fission reactions of heavy nuclei, fusion reaction of light nuclei. Radioisotope transformations are realized in so-called isotope energy sources. The specific mass energy (the energy that a substance weighing 1 kg can release) of artificial radioactive isotopes is significantly higher than that of chemical fuels. Thus, for 210Po it is equal to 5*10 8 KJ/kg, while for the most energy-efficient chemical fuel (beryllium with oxygen) this value does not exceed 3*10 4 KJ/kg. Unfortunately, it is not yet rational to use such engines on space launch vehicles. The reason for this is the high cost of the isotopic substance and operational difficulties. After all, the isotope constantly releases energy, even when transported in a special container and when the rocket is parked at the launch site. Nuclear reactors use more energy-efficient fuel. Thus, the specific mass energy of 235U (the fissile isotope of uranium) is equal to 6.75 * 10 9 KJ/kg, that is, approximately an order of magnitude higher than that of the 210Po isotope. These engines can be “turned on” and “off”; nuclear fuel (233U, 235U, 238U, 239Pu) is much cheaper than isotope fuel. Such engines can use not only water as a working fluid, but also more efficient working substances - alcohol, ammonia, liquid hydrogen. The specific thrust of an engine with liquid hydrogen is 900 s. In the simplest design of a nuclear rocket engine with a reactor running on solid nuclear fuel, the working fluid is placed in a tank. The pump supplies it to the engine chamber. Sprayed using nozzles, the working fluid comes into contact with the fuel-generating nuclear fuel, heats up, expands and is thrown out at high speed through the nozzle. Nuclear fuel is superior in energy reserves to any other type of fuel. Then a logical question arises: why do installations using this fuel still have a relatively low specific thrust and a large mass? The fact is that the specific thrust of a solid-phase nuclear rocket engine is limited by the temperature of the fissile material, and the power plant during operation emits strong ionizing radiation, which has a harmful effect on living organisms. Biological protection from such radiation is very important and is not applicable in space. aircraft. Practical development of nuclear rocket engines using solid nuclear fuel began in the mid-50s of the 20th century in the Soviet Union and the USA, almost simultaneously with the construction of the first nuclear power plants. The work was carried out in an atmosphere of increased secrecy, but it is known that such rocket engines have not yet received real use in astronautics. Everything has so far been limited to the use of isotope sources of electricity of relatively low power on unmanned artificial Earth satellites, interplanetary spacecraft and the world famous Soviet “lunar rover”.

7.Nuclear jet engines, operating principles, methods of obtaining impulse in a nuclear propulsion engine.

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

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

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

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

The fuel elements of a solid-phase reactor are penetrated by channels through which the working fluid of the nuclear propulsion engine flows, gradually heating up. The channels have a diameter of about 1-3 mm, and their total area is 20-30% of the cross-section of the active zone. The core is suspended by a special grid inside the power vessel so that it can expand when the reactor heats up (otherwise it would collapse due to thermal stresses).

The core experiences high mechanical loads associated with significant hydraulic pressure drops (up to several tens of atmospheres) from the flowing working fluid, thermal stresses and vibrations. The increase in the size of the active zone when the reactor heats up reaches several centimeters. The active zone and reflector are placed inside a durable power housing that absorbs the pressure of the working fluid and the thrust created by the jet nozzle. The case is closed with a durable lid. It houses pneumatic, spring or electric mechanisms for driving the regulatory bodies, attachment points for the nuclear propulsion engine to the spacecraft, and flanges for connecting the nuclear propulsion engine to the supply pipelines of the working fluid. A turbopump unit can also be located on the cover.

8 - Nozzle,

9 - Expanding nozzle nozzle,

10 - Selection of working substance for the turbine,

11 - Power Corps,

12 - Control drum,

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

14 - Drive ring for control drums)

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

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

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

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

10.2 Work on TURE in Russia

American" href="/text/category/amerikanetc/" rel="bookmark">Americans, Russian scientists used the most economical and effective tests of individual fuel elements in research reactors. The whole range of work carried out in the 70-80s allowed the design bureau " Salyut", Design Bureau of Chemical Automatics, IAE, NIKIET and NPO "Luch" (PNITI) to develop various projects of space nuclear propulsion engines and hybrid nuclear power plants. In the Design Bureau of Chemical Automatics under the scientific leadership of NIITP (FEI, IAE, NIKIET, NIITVEL, NPO were responsible for the reactor elements). Luch", MAI) were created YARD RD 0411 and nuclear engine of minimum size RD 0410 thrust 40 and 3.6 tons, respectively.

As a result, a reactor, a “cold” engine and a bench prototype were manufactured for testing on hydrogen gas. Unlike the American one, with a specific impulse of no more than 8250 m/s, the Soviet TNRE, due to the use of more heat-resistant and advanced design fuel elements and high temperature in the core, had this figure equal to 9100 m/s and higher. The bench base for testing the TURE of the joint expedition of NPO "Luch" was located 50 km southwest of the city of Semipalatinsk-21. She started working in 1962. In At the test site, full-scale fuel elements of nuclear-powered rocket engine prototypes were tested. In this case, the exhaust gas entered the closed exhaust system. The test bench complex for full-size testing of nuclear engines “Baikal-1” is located 65 km south of Semipalatinsk-21. From 1970 to 1988, about 30 “hot starts” of reactors were carried out. At the same time, the power did not exceed 230 MW with a hydrogen consumption of up to 16.5 kg/sec and its temperature at the reactor outlet of 3100 K. All launches were successful, trouble-free, and according to plan.

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

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

Main Features

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

· Outflow velocity of the working fluid (hydrogen): 9100 - 9800 m/sec.

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

· Maximum operating temperatures: 3000°С - 3700°С (short-term switching on).

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

11.Device

The design of the Soviet solid-phase nuclear rocket engine RD-0410

1 - line from the working fluid tank

2 - turbopump unit

3 - control drum drive

4 - radiation protection

5 - regulating drum

6 - retarder

7 - fuel assembly

8 - reactor vessel

9 - fire bottom

10 - nozzle cooling line

11- nozzle chamber

12 - nozzle

12.Operating principle

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

Nuclear rocket engine reactor

MsoNormalTable">

Working fluid

Density, g/cm3

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

0.071 (liquid)

0.682 (liquid)

1,000 (liquid)

No. Dann

No. Dann

No. Dann

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

15.Benefits

The main advantage of TNREs over chemical rocket engines is the achievement of a higher specific impulse, significant energy reserves, compactness of the system and the ability to obtain very high thrust (tens, hundreds and thousands of tons in a vacuum. In general, the specific impulse achieved in a vacuum is greater than that of a spent two-component chemical rocket fuel(kerosene-oxygen, hydrogen-oxygen) by 3-4 times, and when operating at the highest heat intensity by 4-5 times. Currently, in the USA and Russia there is significant experience in the development and construction of such engines, and if necessary (special space exploration programs), such engines can be produced in a short time and will have a reasonable cost. In the case of using TURE for accelerating spacecraft in space, and subject to the additional use of perturbation maneuvers using the gravitational field major planets(Jupiter, Uranus, Saturn, Neptune) the achievable boundaries of studying the solar system are significantly expanding, and the time required to reach distant planets is significantly reduced. In addition, TNREs can be successfully used for devices operating in low orbits of giant planets using their rarefied atmosphere as a working fluid, or for operating in their atmosphere. /8/

16.Disadvantages

The main disadvantage of TNRE is the presence of a powerful flow of penetrating radiation (gamma radiation, neutrons), as well as the removal of highly radioactive uranium compounds, refractory compounds with induced radiation, and radioactive gases with the working fluid. In this regard, TURE is unacceptable for ground launches in order to avoid deterioration of the environmental situation at the launch site and in the atmosphere. /14/

17.Improving the characteristics of TURD. Hybrid turboprop engines

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

18. Radiation hazard from nuclear propulsion engines.

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

Currently the problem radiation protection spacecraft with nuclear propulsion engines is considered solved in principle. Fundamental issues related to the maintenance of nuclear propulsion engines at test stands and launch sites have also been resolved. Although a working nuclear engine poses a danger to operating personnel, already one day after the end of the nuclear engine operation it is possible without any means personal protection be within a few tens of minutes at a distance of 50 m from the nuclear power plant and even approach it. The simplest means of protection allow maintenance personnel to enter the working area of ​​the nuclear propulsion engine shortly after testing.

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

Conclusion

When considering the prospects for the development and use of nuclear propulsion engines in astronautics, one should proceed from the achieved and expected characteristics of various types of nuclear propulsion engines, from what their application can give to astronautics, and, finally, from the close connection of the problem of nuclear propulsion engines with the problem of energy supply in space and with issues of energy development at all.

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

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

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

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

It is most likely that in the near future solid-phase nuclear propulsion engines will become one of the most common rocket engines. Solid-phase nuclear propulsion engines can be used as devices for long-distance flights, for example, to such planets as Neptune, Pluto, and even to fly beyond the Solar System. However, for flights to the stars, a nuclear powered engine based on fission principles is not suitable. In this case, promising are nuclear engines or, more precisely, thermonuclear jet engines (TRE), operating on the principle of fusion reactions, and photonic jet engines (PRE), the source of momentum in which is the annihilation reaction of matter and antimatter. However, most likely humanity will use a different method of transportation to travel in interstellar space, different from jet.

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

LITERATURE

Sources:

1. "Rockets and People. Book 4 Moon Race" - M: Znanie, 1999.
2. http://www. lpre. de/energomash/index. htm
3. Pervushin “Battle for the Stars. Cosmic Confrontation” - M: knowledge, 1998.
4. L. Gilberg “Conquest of the sky” - M: Znanie, 1994.
5. http://epizodsspace. *****/bibl/molodtsov
6. “Engine”, “Nuclear engines for spacecraft”, No. 5 1999

7. "Engine", "Gas-phase nuclear engines for spacecraft",

No. 6, 1999
7. http://www. *****/content/numbers/263/03.shtml
8. http://www. lpre. de/energomash/index. htm
9. http://www. *****/content/numbers/219/37.shtml
10., Chekalin transport of the future.

M.: Knowledge, 1983.

11. , Chekalin space exploration. - M.:

Knowledge, 1988.

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

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

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

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

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

APPLICATION

Main characteristics of solid phase nuclear jet engines

Country of origin	Engine	Thrust in vacuum, kN	Specific impulse, sec		Project work, year
	NERVA/Lox Mixed Cycle

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 seen 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 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 towards 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 is becoming 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 secure world 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.
They have an industrial policy and 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 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. Eat high risk find yourself in a dead end when improving half a century old rocket engines based on chemical fuel, as Elon Musk’s SpaceX is doing, or 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 rather than on 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 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 size spaceships than all that have been created by mankind previously, including the modular ISS. In these ships it is necessary to ensure long-term autonomous existence crews, and a certain supply of fuel and operating life of sustainer engines and engines for maneuvers and orbit correction, 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 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 a 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, you place inside a rocket engine nuclear reactor, into the active zone of which a substance in liquid or gaseous form will be supplied, then it, heating up 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 the 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 when high temperatures The engine itself may melt along with the spacecraft. 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 carried out 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 engine 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 fuel engines (nuclear fuel based on uranium carbides was in the reactor in a solid state), 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 for Soviet program"Mars-94" of the first manned flight to Mars, the Energia launch vehicle began to be created, 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 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 reactor of the Yenisei project had a thermal power of up to 135 kW and electrical power 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 comparable power by reducing the starting 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 production 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 whose system 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. 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 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 and world economy and politics. The main thing is to be at the origins of these changes.

Pulse YARD was developed in accordance with the principle proposed in 1945 by Dr. S. Ulam of the Los Alamos Research Laboratory, according to which it is proposed to use a nuclear charge as the energy source (fuel) of a highly efficient space rocket launcher.

In those days, as in the many years that followed, nuclear and thermonuclear charges were the most powerful and compact sources of energy compared to any other. As you know, we are currently on the verge of discovering ways to control an even more concentrated source of energy, since we are already quite advanced in the development of the first unit using antimatter. If we proceed only from the amount of available energy, then nuclear charges provide a specific thrust of more than 200,000 seconds, and thermonuclear charges - up to 400,000 seconds. These specific thrust values ​​are excessively high for most flights within the solar system. Moreover, when using nuclear fuel in its “pure” form, many problems arise that, even at the present time, have not yet been fully resolved. So, the energy released during the explosion must be transferred to the working fluid, which heats up and then flows out of the engine, creating thrust. In accordance with conventional methods for solving such a problem, a nuclear charge is placed in a “combustion chamber” filled with a working fluid (for example, water or other liquid substance), which evaporates and then expands with a greater or lesser degree of diabaticity in the nozzle.

Such a system, which we call an internal pulsed nuclear propulsion engine, is very effective, since all the products of the explosion and the entire mass of the working fluid are used to create thrust. An unsteady operating cycle allows such a system to develop higher pressures and temperatures in the combustion chamber, and as a result, a higher specific thrust compared to a continuous operating cycle. However, the very fact that explosions occur inside a certain volume imposes significant restrictions on the pressure and temperature in the chamber, and, consequently, on the achievable value of specific thrust. In view of this, despite the many advantages of an internal pulsed NRE, an external pulsed NRE turned out to be simpler and more efficient due to the use of the gigantic amount of energy released during nuclear explosions.

In an external-action nuclear propulsion engine, not the entire mass of the fuel and working fluid takes part in creating jet thrust. However, here even with lower efficiency. More energy is used, resulting in more efficient system performance. An external pulsed NPP (hereinafter referred to simply as a pulsed NPP) uses the energy of the explosion of a large number of small nuclear charges on board the rocket. These nuclear charges are sequentially ejected from the rocket and detonated behind it at some distance ( drawing below). With each explosion, some of the expanding gaseous fission fragments in the form of plasma with high density and speed collide with the base of the rocket - the pusher platform. The momentum of the plasma is transferred to the pushing platform, which moves forward with great acceleration. Acceleration is reduced by a damping device to several g in the nose compartment of the rocket, which does not exceed the endurance limits of the human body. After the compression cycle, the damping device returns the pushing platform to its initial position, after which it is ready to receive the next impulse.

The total speed increase acquired by the spacecraft ( drawing, borrowed from work ), depends on the number of explosions and, therefore, is determined by the number of nuclear charges expended during a given maneuver. Systematic development of such a nuclear power propulsion project was begun by Dr. T. B. Taylor (General Atomics Division of General Dynamics) and continued with the support of the Advanced Research Projects Agency (ARPA), the US Air Force, NASA and General Dynamic" for nine years, after which work in this direction was temporarily stopped in order to resume again in the future, since this type of propulsion system was chosen as one of the two main propulsors of spacecraft flying within the solar system.

Operating principle of a pulsed external-action nuclear propulsion engine

An early version of the installation, developed by NASA in 1964-1965, was comparable (in diameter) to the Saturn 5 rocket and provided a specific thrust of 2500 sec and an effective thrust of 350 g; the “dry” weight (without fuel) of the main engine compartment was 90.8 tons. The initial version of the pulsed nuclear rocket engine used the previously mentioned nuclear charges, and it was assumed that it would operate in low Earth orbits and in the radiation belt zone due to the danger of radioactive contamination atmosphere by decay products released during explosions. Then the specific thrust of pulsed nuclear-powered engines was increased to 10,000 seconds, and the potential capabilities of these engines made it possible to double this figure in the future.

A pulsed nuclear propulsion system may have already been developed in the 70s, with a view to carrying out the first manned space flight to the planets in the early 80s. However, the development of this project was not carried out in full force due to the approval of the program for the creation of a solid-phase nuclear propulsion engine. In addition, the development of a pulsed nuclear rocket engine was associated with a political problem, since it used nuclear charges.

Erica K.A. (Krafft A. Ehricke)