Rocket engines on liquid fuel gave man the opportunity to go into space - into near-Earth orbits. However, such rockets burn 99% of their fuel in the first few minutes of flight. The remaining fuel may not be enough to travel to other planets, and the speed will be so low that the voyage will take tens or hundreds of years. Nuclear engines can solve the problem. How? We'll figure it out together.

The operating principle of a jet engine is very simple: it converts fuel into the kinetic energy of a jet (the law of conservation of energy), and due to the direction of this jet, the rocket moves in space (the law of conservation of momentum). It is important to understand that we cannot accelerate a rocket or an airplane to a speed greater than the speed of the outflow of fuel - hot gas thrown back.

New Horizons spacecraft

What distinguishes an effective engine from an unsuccessful or outdated analogue? First of all, how much fuel the engine will need to accelerate the rocket to the desired speed. This most important parameter of a rocket engine is called specific impulse, which is defined as the ratio of total impulse to fuel consumption: the higher this indicator, the more efficient the rocket engine. If the rocket consists almost entirely of fuel (meaning there is no room for a payload, an extreme case), the specific impulse can be considered equal to the speed of the fuel (working fluid) flowing out of the rocket nozzle. Launching a rocket is an extremely expensive undertaking; every gram of not only the payload, but also the fuel, which also weighs and takes up space, is taken into account. Therefore, engineers are selecting more and more active fuel, a unit of which would give maximum efficiency, increasing the specific impulse.

The vast majority of rockets in history and modern times have been equipped with engines that use a chemical combustion reaction (oxidation) of fuel.

They made it possible to reach the Moon, Venus, Mars and even the distant planets - Jupiter, Saturn and Neptune. True, space expeditions took months and years (automatic stations Pioneer, Voyager, New Horizons, etc.). It should be noted that all such rockets consume a significant part of the fuel to lift off from the Earth, and then continue to fly by inertia with rare moments of turning on the engine.

Pioneer spacecraft

Such engines are suitable for launching rockets into near-Earth orbit, but to accelerate it to at least a quarter of the speed of light, an incredible amount of fuel will be needed (calculations show that 103,200 grams of fuel are needed, despite the fact that the mass of our Galaxy is no more than 1056 grams). It is obvious that in order to reach the nearest planets, and even more so the stars, we need sufficiently high speeds, which liquid-fuel rockets are not able to provide.

​Gas-phase nuclear engine

Deep space is a completely different matter. Take Mars, for example, “habitated” by science fiction writers far and wide: it is well studied and scientifically promising, and most importantly, it is closer than anyone else. The point is a “space bus” that can deliver the crew there in a reasonable time, that is, as quickly as possible. But there are problems with interplanetary transport. It is difficult to accelerate it to the required speed while maintaining acceptable dimensions and spending a reasonable amount of fuel.

RS-25 (Rocket System 25) is a liquid-propellant rocket engine produced by Rocketdyne, USA. Used on a space glider transport system"Space Shuttle", each of which had three such engines installed. Better known as the SSME engine (English Space Shuttle Main Engine - the main engine of the space shuttle). The main components of the fuel are liquid oxygen (oxidizer) and hydrogen (fuel). RS-25 uses a closed cycle scheme (with afterburning of the generator gas).

The solution may be a “peaceful atom” pushing spaceships. Engineers started thinking about creating a lightweight and compact device capable of launching at least itself into orbit back in the late 50s of the last century. The main difference between nuclear engines and rockets with internal combustion engines is that kinetic energy is obtained not from the combustion of fuel, but from the thermal energy of the decay of radioactive elements. Let's compare these approaches.

From liquid engines a hot “cocktail” of exhaust gases emerges (the law of conservation of momentum), formed during the reaction of fuel and oxidizer (the law of conservation of energy). In most cases it is a combination of oxygen and hydrogen (the result of burning hydrogen is plain water). H2O has much more molar mass than hydrogen or helium, so it is more difficult to accelerate; the specific impulse for such an engine is 4,500 m/s.

NASA ground tests new system launch space rockets, 2016 (Utah, USA). These engines will be installed on the Orion spacecraft, which is planned for a mission to Mars.

IN nuclear engines It is proposed to use only hydrogen and accelerate (heat) it using the energy of nuclear decay. This results in savings on the oxidizer (oxygen), which is already great, but not everything. Since hydrogen has a relatively low specific gravity, it is easier for us to accelerate it to more high speeds. Of course, you can use other heat-sensitive gases (helium, argon, ammonia and methane), but all of them are at least two times inferior to hydrogen in the most important thing - achievable specific impulse (more than 8 km/s).

So is it worth losing it? The gain is so great that engineers are not stopped either by the complexity of the design and control of the reactor, or by its heavy weight, or even by the radiation danger. Moreover, no one is going to launch from the surface of the Earth - the assembly of such ships will be carried out in orbit.

"Flying" reactor

How does a nuclear engine work? The reactor in a space engine is much smaller and more compact than its terrestrial counterparts, but all the main components and control mechanisms are fundamentally the same. The reactor acts as a heater into which liquid hydrogen is supplied. Temperatures in the core reach (and can exceed) 3000 degrees. The heated gas is then released through the nozzle.

However, such reactors emit harmful radiation. To protect the crew and numerous electronic equipment from radiation, thorough measures are required. Therefore projects interplanetary spacecraft With a nuclear engine, they often resemble an umbrella: the engine is located in a shielded separate block, connected to the main module by a long truss or pipe.

"Combustion chamber" nuclear engine is the reactor core, in which the fuel supplied high pressure hydrogen heats up to 3000 degrees or more. This limit is determined only by the heat resistance of the reactor materials and the properties of the fuel, although increasing the temperature increases the specific impulse.

Fuel elements- these are heat-resistant ribbed (to increase the heat transfer area) cylinders-“glasses” filled with uranium pellets. They are “washed” by a gas flow, which plays the role of both the working fluid and the reactor coolant. The entire structure is insulated with beryllium reflective screens that do not release dangerous radiation to the outside. To control the heat release, special rotary drums are located next to the screens

There are a number of promising designs of nuclear rocket engines, the implementation of which is waiting in the wings. After all, they will mainly be used in interplanetary travel, which, apparently, is just around the corner.

Nuclear propulsion projects

These projects were frozen due to various reasons- lack of money, complexity of the design, or even the need for assembly and installation in outer space.

"ORION" (USA, 1950–1960)

A project of a manned nuclear pulse spacecraft (“explosion plane”) for the exploration of interplanetary and interstellar space.

Operating principle. From the ship's engine, in the direction opposite to the flight, a small equivalent nuclear charge is ejected and detonated at a relatively short distance from the ship (up to 100 m). The impact force is reflected from the massive reflective plate at the tail of the ship, “pushing” it forward.

"PROMETHEUS" (USA, 2002–2005)

A NASA space agency project to develop a nuclear engine for spacecraft.

Operating principle. The spacecraft's engine was to consist of ionized particles that create thrust and a compact nuclear reactor that provides energy to the installation. The ion engine creates a thrust of about 60 grams, but can operate continuously. Ultimately, the ship will gradually be able to gain enormous speed - 50 km/sec, spending a minimum amount of energy.

"PLUTO" (USA, 1957–1964)

Project to develop a nuclear ramjet engine.

Operating principle. Air through the front vehicle enters a nuclear reactor where it is heated. Hot air expands, acquires greater speed and is released through the nozzle, providing the necessary draft.

NERVA (USA, 1952–1972)

(eng. Nuclear Engine for Rocket Vehicle Application) is a joint program of the Commission on atomic energy USA and NASA to create a nuclear rocket engine.

Operating principle. The liquid hydrogel is fed into a special compartment in which it is heated. nuclear reactor. The hot gas expands and is released into the nozzle, creating thrust.

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 supplied specific task for ships with nuclear propulsion engines - 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 engine. 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 during 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 work area 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 and 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, starting a nuclear engine is unacceptable for launches from the surface of the Earth due to the risk of radioactive contamination.

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

Characteristics of a cruise missile with a nuclear power plant

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

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

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

The operating principle of a Russian nuclear-powered cruise missile

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

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

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

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

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 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. The non-stationary operating cycle allows such a system to develop more high pressure 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. used more energy, which allows you to get more efficient characteristics systems An external pulsed NPP (hereinafter referred to simply as a pulsed NPP) uses explosion energy large quantity small nuclear warheads on board a missile. 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 collides with the base of the rocket - the pushing 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 endurance limits 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 NPP

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)

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

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

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

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

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

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

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