Helium energy. The moon and a penny, or the history of helium energy

It is necessary to understand that today the study of the solar system, the study of extraterrestrial matter, the chemical structure of the Moon and planets, the search for extraterrestrial life forms, the understanding of the physics of the Universe is the forefront of fundamental science. Modern space research should be considered not as one of the directions or branches of science, but as a stage in the development of science. Without the results obtained in space research, neither physics, nor biology, nor chemistry, nor geological sciences are incomplete.

The retreat into the background of a country with a rich experience and tradition of space exploration cannot but cause concern and a desire to understand the reasons.

E. M. Galimov

Helium 3 - the mythical fuel of the future

Probably few things in the field of thermonuclear energy are surrounded by myths like Helium 3. In the 80s-90s, it was actively popularized as a fuel that would solve all the problems of controlled thermonuclear fusion, and also as one of the reasons to get out of the Earth (since on there are literally hundreds of kilograms of it on earth, and a billion tons on the moon) and finally begin to explore the solar system. All this is based on very strange ideas about the possibilities, problems and needs of thermonuclear energy, which does not exist today, which we will talk about

Remember, I wrote that the ITER toroidal field magnets, which create backpressure to the plasma, are absolutely record-breaking products, the only ones in the world in terms of parameters? So, He3 fans propose making the magnets 500 times more powerful.

The extraction of helium-3 on the Moon will provide earthlings with energy for 5 thousand years

The reserves of helium-3 available on the Moon can provide earthlings with energy for five thousand years to come, said on Wednesday at a multimedia lecture at RIA Novosti, Doctor of Physical and Mathematical Sciences, head of the Department of Lunar and Planetary Research at the State Astronomical Institute of Moscow State University. Lomonosov Vladislav Shevchenko.

The possibilities of providing the inhabitants of the Earth with energy resources are not unlimited; their reserves on our planet will be exhausted in the coming centuries. At the same time, the United States has already calculated that the reserves of helium-3 available on the Moon can provide earthlings with energy for at least five thousand years to come, Shevchenko said.

Yes, the cost of one ton of helium-3 will be approximately a billion dollars, provided that the necessary infrastructure for extraction and delivery from the Moon is created. But at the same time, 25 tons - and this is only 25 billion dollars, which is not so much on the scale of the states of our planet - is enough to provide energy to earthlings for a year. Currently, the United States alone spends approximately $40 billion a year on energy. The benefit is obvious,” Shevchenko noted.

According to him, in the near future, partners in the International Space Station (ISS) should gradually move from its operation to the creation of an International Lunar Station (ILS). Our path now is from the ISS to the MLS. “We will get great practical benefits,” the scientist concluded.

Currently, the helium-3 isotope on Earth is mined in very small quantities, amounting to several tens of grams per year.

On the Moon, the reserves of this valuable isotope are, according to minimal estimates, about 500 thousand tons. Nuclear fusion, when 1 ton of helium-3 reacts with 0.67 tons of deuterium, releases energy equivalent to the combustion of approximately 15 million tons of oil.

In an interview with the Trud newspaper, academician Roald Zinnurovich Sagdeev called the sensation raised around the production of helium-3 on the Moon. not worth a damn.

Academician Sagdeev said that at the recently held 30th Korolev Readings, the tone was set by supporters of lunar projects, who argued that the extraction of helium-3 on the Moon is a profitable and promising task. It is believed that thermonuclear reactors. powered by helium-3 will provide humanity with energy for millennia.

Plans to create a base on the Moon by 2015 and to extract and transport helium-3, which were presented at the readings, are completely unrealistic. And helium-3 will be needed no earlier than in 80-100 years.

Academician Sagdeev said that there are still no reactors operating on deuterium and tritium. Although, the reserves of deuterium in sea water are practically unlimited. It will take about 100 more years to create a thermonuclear reactor powered by helium-3. “In a word, building a helium reactor is not even a task of the 21st, but of the 22nd century,” says Sagdeev.

Therefore, plans to create a base on the Moon and extract helium-3 there are an illusion: “In fact, all this hype associated with the proposal to mine helium-3 on the Moon is not worth a damn.”

Sagdeev’s words from an interview: “When, for example, the head of RSC Energia, Nikolai Sevastyanov, talks about the extraction of helium-3 on the Moon, I smile internally and even somewhere sympathize with such an enthusiastic person who, surprisingly, finds himself in captivity of illusions.” .

Helium-3 was discovered by Australian scientist Mark Oliphant while working at the University of Cambridge.

Application 3 He

Helium-3 is used in nuclear fusion research. It is a by-product of reactions occurring in the Sun. On Earth it is mined in very small quantities, amounting to several tens of grams per year. The reason for this is our atmosphere. facilitating the reaction of Helium-3 with other substances. Thermonuclear fusion of 1 ton of helium-3 releases energy equal to 15 million tons of oil.

3 He reserves on Earth

On Earth, its reserves are approximately estimated at 500-1000 kilograms and are extremely dispersed in the atmosphere and rocks.

3 He reserves on the Moon

The lunar resources of Helium-3 are very large and should be sufficient for at least the next millennium. The main problem remains that controlled thermonuclear fusion has not yet been implemented, and according to the most optimistic forecasts, the possibility of commercial use will not occur until 2050.

Sources: znaniya-sila.narod.ru, hodar.ru, ria.ru, ru.wikinews.org, traditio-ru.org

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Helium-three. A strange and incomprehensible phrase. Nevertheless, the further we go, the more we will hear it. Because, according to experts, it is helium-three that will save our world from the impending energy crisis. And in this enterprise the most active role is assigned to Russia.

Moon

Promising thermonuclear energy, using the deuterium-tritium fusion reaction as a basis, although safer than the energy of nuclear fission, which is used in modern nuclear power plants, still has a number of significant drawbacks.

Firstly, this reaction releases a much larger (by an order of magnitude!) number of high-energy neutrons. None of the known materials can withstand such an intense neutron flux for more than six years - despite the fact that it makes sense to make a reactor with a resource of at least 30 years. Consequently, the first wall of a tritium fusion reactor will need to be replaced - and this is a very complex and expensive procedure, which also involves shutting down the reactor for a fairly long period of time.
Secondly, it is necessary to shield the magnetic system of the reactor from powerful neutron radiation, which complicates and, accordingly, increases the cost of the design.
Third, many structural elements of a tritium reactor after the end of operation will be highly active and will require long-term burial in storage facilities specially created for this purpose.

In the case of using deuterium with the helium-3 isotope instead of tritium in a thermonuclear reactor, most problems can be solved. The intensity of the neutron flux drops by 30 times - accordingly, a service life of 30-40 years can be easily ensured. After the end of operation of the helium reactor, no high-level waste will be generated, and the radioactivity of the structural elements will be so low that they can be literally buried in a city landfill, lightly sprinkled with earth.

What's the problem? Why are we still not using such beneficial thermonuclear fuel?

First of all, because this isotope is extremely scarce on our planet. It is born in the Sun, which is why it is sometimes called a “solar isotope.” Its total mass there exceeds the weight of our planet. Helium-3 is carried into the surrounding space by the solar wind. The Earth's magnetic field deflects a significant part of this wind, and therefore helium-3 makes up only one trillionth of the Earth's atmosphere - about 4000 tons. On the Earth itself it is even less - about 500 kg.

There is much more of this isotope on the Moon. There it is embedded in the lunar soil “regolith”, whose composition resembles ordinary slag. We are talking about huge - almost inexhaustible reserves!

Analysis of six soil samples brought by the Apollo expeditions and two samples delivered by Soviet automatic stations " Moon“, showed that the regolith covering all the seas and plateaus of the Moon contains up to 106 tons of helium-3, which would meet the needs of earthly energy, even increased several times compared to modern ones, for a millennium! According to modern estimates, the reserves of helium-3 on the Moon are three orders of magnitude greater - 109 tons.

In addition to the Moon, helium-3 can be found in the dense atmospheres of the giant planets, and, according to theoretical estimates, its reserves on Jupiter alone amount to 1020 tons, which would be enough to power the Earth’s energy supply until the end of time.

Helium-3 mining projects

Regolith covers the Moon with a layer several meters thick. The regolith of the lunar seas is richer in helium than the regolith of the plateaus. 1 kg of helium-3 is contained in approximately 100,000 tons of regolith.

Therefore, in order to extract the precious isotope, it is necessary to process a huge amount of crumbly lunar soil.

Taking into account all the features, the helium-3 production technology should include the following processes:

1. Extraction of regolith.

Special “harvesters” will collect regolith from a surface layer about 2 m thick and deliver it to processing points or process it directly during the mining process.

2. Release of helium from regolith.

When the regolith is heated to 600?C, 75% of the helium contained in the regolith is released (desorbed); when heated to 800?C, almost all of the helium is released. It is proposed to heat the dust in special furnaces, focusing sunlight either with plastic lenses or mirrors.

3. Delivery to Earth by reusable spacecraft.

When helium-3 is mined, numerous substances are also extracted from the regolith: hydrogen, water, nitrogen, carbon dioxide, nitrogen, methane, carbon monoxide, which can be useful for maintaining the lunar industrial complex.

The project of the first lunar harvester, designed to process regolith and extract the helium-3 isotope from it, was proposed by the group of J. Kulczynski. Currently, private American companies are developing several prototypes, which, apparently, will be submitted to the competition after NASA decides on the features of a future expedition to the Moon.

It is clear that, in addition to delivering harvesters to the Moon, storage facilities, a manned base (to service the entire complex of equipment), a cosmodrome and much more will have to be built there. It is believed, however, that the high costs of creating a developed infrastructure on the Moon will pay off handsomely in terms of the coming global energy crisis, when traditional types of energy resources (coal, oil, natural gas) will have to be abandoned.

Main technological problem

There is one important problem on the way to creating energy based on helium-3. The fact is that the deuterium-helium-3 reaction is much more difficult to carry out than the deuterium-tritium reaction.

First of all, it is unusually difficult to ignite a mixture of these isotopes. The estimated temperature at which a thermonuclear reaction will occur in a deuterium-tritium mixture is 100-200 million degrees. When using helium-3, the required temperature is two orders of magnitude higher. In fact, we must light a small sun on Earth.

However, the history of the development of nuclear energy (the last half century) demonstrates an increase in generated temperatures by an order of magnitude within 10 years. In 1990, the European tokamak JET already burned helium-3, and the resulting power was 140 kW. Around the same time, the American tokamak TFTR reached the temperature necessary to start the reaction in the deuterium-helium mixture.

However, lighting the mixture is still half the battle. The downside of thermonuclear energy is the difficulty of obtaining practical returns, because the working fluid is plasma heated to many millions of degrees, which has to be kept in a magnetic field.

Experiments on taming plasma have been carried out for many decades, but only at the end of June last year in Moscow, representatives of a number of countries signed an agreement on the construction in the south of France in the city of Cadarache of the International Thermonuclear Experimental Reactor (ITER) - a prototype of a practical thermonuclear power plant. ITER will use deuterium and tritium as fuel.

A helium-3 thermonuclear reactor will be structurally more complex than ITER, and so far it is not even in the projects. And although experts hope that a prototype helium-3 reactor will appear in the next 20-30 years, for now this technology remains pure fantasy.

The issue of helium-3 mining was analyzed by experts during a hearing on the future of lunar exploration and development, held in April 2004 in the Subcommittee on Space and Aeronautics of the US House of Representatives Science Committee. Their conclusion was clear: even in the distant future, mining helium-3 on the Moon is completely unprofitable.

As John Logsdon, director of the Space Policy Institute in Washington, noted: “The US space community does not view helium-3 mining as a serious excuse for returning to the Moon. Flying there for this isotope is the same as sending Columbus to India for uranium five hundred years ago. He could bring it, and he would bring it, but for another few hundred years no one would know what to do with it.”

Helium-3 extraction as a national project

“We are now talking about thermonuclear energy of the future and a new ecological type of fuel that cannot be produced on Earth. We are talking about the industrial development of the Moon for the extraction of helium-3.”

This statement by the head of the Energia rocket and space corporation, Nikolai Sevastyanov, was perceived by Russian scientific observers as an application for the formation of a new “national project.”

Indeed, in fact, one of the main functions of the state, especially in the 20th century, was precisely the formulation of tasks for society on the verge of imagination. This also applied to the Soviet state: electrification, industrialization, the creation of the atomic bomb, the first satellite, the turning of rivers.

Today in the Russian Federation the state is trying, but cannot formulate tasks that are on the verge of the impossible. The state needs someone to show it a national project and justify the benefits that theoretically flow from this project. The program for the development and extraction of helium-3 from the Moon to Earth in order to supply thermonuclear energy with fuel ideally meets these requirements.

“I just think that there is a deficiency in some major technological problem,” Alexander Zakharov, Doctor of Physical and Mathematical Sciences, Scientific Secretary of the Space Research Institute of the Russian Academy of Sciences, emphasized in an interview. “Maybe this is why all this talk about mining helium-3 on the Moon for thermonuclear energy has arisen recently. If Moon- a source of minerals, and from there to bring this helium-3, but on Earth there is not enough energy... All this is understandable, it sounds very beautiful. And it may be easy to persuade influential people to allocate money for this. I think so".

It will not take long, by the standards of human civilization, before fossil natural resources will be exhausted. Among the possible candidates for replacing oil and gas are solar energy, wind power, or hydrogen. In recent years, you can increasingly hear about a new salvation for the planet called helium-3. It was only recently discovered that this substance can be used as a raw material for power plants.

General information about the substance: properties

In 1934, Australian physicist Mark Oliphant, while working at the Cavendish Laboratory at the University of Cambridge in England, came to a remarkable discovery. During the first demonstration of nuclear fusion by bombarding a deuteron target, he hypothesized the existence of a new isotope of the chemical element number 2. Today it is known as helium-3.

It has the following properties:

Contains two protons, one neutron and two electrons;
Among all known elements, it is the only stable isotope that has more protons than neutrons;
Boils at 3.19 Kelvin (-269.96 degrees Celsius). During boiling, a substance loses half its density;
The angular momentum is ½, making it a fermion;
The latent heat of vaporization is 0.026 KJ/mol;

Five years after the discovery of Mark Oliphant, his theoretical constructions received experimental confirmation. And after 9 years, scientists managed to obtain a compound V liquid form . As it turned out, in this state of aggregation, helium-3 has superfluid properties.

In other words, at temperatures close to absolute zero, it is able to penetrate through capillaries and narrow cracks, experiencing virtually no resistance from friction.

Helium-3 mining on the Moon

Over billions of years, the solar wind deposited gigantic amounts of helium-3 into the surface layer of regolith. According to estimates, its amount on the earth's satellite can reach 10 million tons.

Many space powers have a program for extracting this substance for the purpose of subsequent thermonuclear fusion:

In January 2006, the Russian company Energia announced plans to begin geological work on the Moon by 2020. Today, the future of the project is in limbo due to the difficult economic situation of the country;
In 2008, the Indian Space Research Organization sent a probe to the surface of the earth's satellite, one of the goals of which was stated to be the study of helium-containing minerals;
China also has its own plans for deposits of precious raw materials. According to plans, it is planned to send three shuttles to the satellite annually. The energy produced from this fuel will more than cover the needs of all humanity.

For now it remains a dream that can only be seen in science fiction films. Among them are “Moon” (2009) and “Iron Sky” (2012).

In this video, physicist Boris Romanov will tell you in what form the substance helium-3 is found on the Moon, and whether it is possible to import it from there:

Geochemical data

The isotope is also present on planet Earth, although in smaller quantities:

This is the main component of the earth's mantle, which was synthesized during planet formation. Its total mass in this part of the planet is, according to various estimates, from 0.1 to 1 million tons;
It comes to the surface as a result of volcanic activity. Thus, the hills of the Hawaiian Islands emit about 300 grams of this substance per year. Mid-ocean ridges - about 3 kilograms;
In places where one lithospheric plate collides with another, there may be hundreds of thousands of tons of helium isotope. It is not possible to extract this wealth industrially at the present stage of technological development;
Nature continues to produce this compound to this day, as a result of the decay of radioactive elements in the crust and mantle;
It can be found in fairly small quantities (up to 0.5%) in some natural gas sources. As experts note, every year during the transportation of natural gas, 26 m 3 of helium-3 is separated;
It is also present in the earth's atmosphere. Its specific fraction is approximately 7.2 parts per trillion atoms of other atmospheric gases. According to the latest calculations, the total mass of atmospheric 3 2 he reaches at least 37 thousand tons.

Modern uses of the substance

Almost all of the isotopes used in the national economy are produced by the radioactive decay of tritium, which is bombarded with lithium-6 neutrons in a nuclear reactor.

For decades helium-3 was just a by-product in the manufacture of atomic weapon warheads. However, after the signing of the START I treaty in 1991, the superpowers reduced the volume of missile production, which is why production products also began to decline.

Today, production of the isotope is booming as new uses have been found for it:

Due to the relatively high gyromagnetic ratio, particles of this substance are used in medical tomography of the lungs. The patient inhales a gas mixture containing hyperpolarized helium-3 atoms. Then, under the influence of infrared laser radiation, the computer draws anatomical and functional images of the organs;
In scientific laboratories, this compound is used for cryogenic purposes. By evaporating it from the surface of the refrigerator, it is possible to achieve values close to 0.2 kelvin;
In recent years, the idea of using the substance as a feedstock for power plants has been gaining popularity. The first such installation was built in 2010 in the Tennessee Valley (USA).

Helium-3 as a fuel

A second, revised approach to the use of controlled fusion energy involves the use of 3 2 he and deuterium as raw materials. The result of such a reaction will be helium-4 ion and high-energy protons.

Theoretically, this technology has the following advantages:

High efficiency because an electrostatic field is used to control the fusion of ions. The kinetic energy of protons is directly converted into electricity through solid-state conversion. There is no need to build turbines, which are used in nuclear power plants to convert the energy of protons into heat;
Lower, in comparison with other types of power plants, capital and operating costs;
Neither air nor water is polluted;
Relatively small dimensions due to the use of modern compact installations;
There is no radioactive fuel.

However, critics note the significant “crudeness” of this decision. At best commercial use of thermonuclear fusion will begin no earlier than 2050.

Among all the isotopes of a chemical element with atomic number 2, helium-3 stands out. What it is can be briefly described by the following properties: it is stable (that is, it does not undergo transformations as a result of radiation), has superfluid properties in liquid form, and has a relatively small mass.

Video about the formation of helium-3 in the Universe

In this video, physicist Daniil Potapov will tell you how helium-3 was formed in the Universe, what role it played in the formation of the Universe:

It is possible that in the coming years we will witness the Lunar Race-2, the winner (or winners) of which will get their hands on an almost inexhaustible source of energy. This, in turn, will allow humanity to enter a qualitatively new technological structure, the parameters of which we can only guess about.

What is helium-3?

From the school physics course we remember that the atomic mass of helium is four and this element is an inert gas. It is problematic to use it in any chemical reactions, especially those that release energy. A completely different matter is the isotope of helium with atomic mass 3. It is capable of entering into a thermonuclear reaction with deuterium (an isotope of hydrogen with atomic mass 2), resulting in the formation of gigantic energy due to the synthesis of ordinary helium-4 with the release of a proton (3 He + D → 4 Not + p + energy). Similarly, from just one gram of helium-3 you can get the same energy as burning 15 tons of oil.

A ton of helium-3 is enough to release 10 GW of energy for a year. Thus, to cover all of Russia’s current energy needs, 20 tons of helium-3 will be needed annually, and for all of humanity, approximately 200 tons of this isotope will be required per year. At the same time, there will be no need to burn oil and gas, the reserves of which are not unlimited; according to the latest estimates of proven hydrocarbon reserves, humanity will only last for half a century. There will be no need to operate quite dangerous nuclear power plants, which has become especially important after Chernobyl and Fukushima.

Where can I get helium-3?

With modern technology development, the only truly accessible source of this element is the surface of the Moon. Helium-3 itself is formed in the interior of stars (for example, our Sun) as a result of the combination of two hydrogen atoms.

In this case, the main product of this reaction is ordinary helium-4, and the isotope-3 is formed in small quantities. Some of it is carried out by the solar wind and distributed evenly throughout the planetary system.

Helium-3 practically does not fall onto Earth, since its atoms are deflected by the magnetic field of our planet. But on planets that do not have such a field, the element is deposited in the upper layers of the soil and gradually accumulates. The closest celestial body to the Earth that does not have a magnetic field is the Moon, so it is here that the reserves of this valuable energy carrier available to humanity are concentrated.

This is confirmed not only by theoretical calculations, but also by the results of empirical research. Helium-3 was found in relatively high concentrations in all lunar soil samples delivered to Earth. On average, there is 1 gram per 100 tons of regolith. of this energy isotope.

Thus, in order to extract the above-mentioned 20 tons of helium-3 to fully satisfy the annual energy needs of the Russian Federation, it will be necessary to “shovel” 2,000 million tons of lunar soil.

Physically, this corresponds to an area on the Moon measuring 20x20 km with a quarry depth of 3 m. The task of organizing such large-scale mining is quite complex, but quite solvable, modern engineers are sure. Apparently, a more difficult and expensive problem will be delivering tens of tons of fuel for fusion furnaces to Earth.

What does humanity lack for the helium energy revolution?

To develop full-fledged thermonuclear energy on Earth based on helium-3, people will have to solve three main problems.

1. Creation of reliable and powerful means of delivering goods along the Earth-Moon route and back.
2. Construction of lunar bases and complexes for the extraction of helium-3, which is associated with many technological problems.
3. Construction of actual thermonuclear power plants on Earth, for which certain technological barriers also have to be overcome.

Humanity has come close to solving the first problem. All four countries participating in Moon Race 2 plus the European Union have already developed or are developing heavy-duty rockets capable of throwing tons of cargo into lunar orbit. For example, by 2027, Russia plans to implement the Angara-A5V launch vehicle in hardware, which will be capable of delivering at least 10 tons of payload to the Moon. Return transportation will be easier, since the gravitational force of the Moon is 6 times less than that of Earth, but fuel will be a problem here. It will either have to be imported from Earth or produced on the surface of our satellite.

The second task is much more serious, since in addition to organizing the actual extraction of helium-3 from the regolith, engineers will have to create reliable lunar bases with life support systems for the miners of the future. Technologies developed through many years of operation of orbital stations, primarily the ISS and Mir, will greatly help with this. Both in Russia and in other countries, lunar bases are being actively designed today, and, perhaps, our country today has the maximum technology for the real implementation of such projects.

As for the third problem, work on the creation of thermonuclear reactors has been going on on Earth for the last three decades. The main technological difficulty here is the problem of confining high-temperature plasma (necessary for “igniting” thermonuclear fusion) in the so-called. "magnetic traps".

This issue has already been resolved for reactors operating on the principle of combining deuterium and tritium (D + T = 4 He + n + energy). To maintain such a reaction, a temperature of 100 million degrees is sufficient.

However, such reactors will never become widespread, since they are extremely radioactive. To start a reaction involving helium-3 and deuterium, temperatures of 300-700 million degrees will be needed. So far, such plasma cannot be kept in magnetic traps for a long time, but perhaps a breakthrough in this area will be led by the launch of the International Thermonuclear Experimental Reactor (ITER), which is currently being built in France and will be put into operation by 2025.

Thus, the decade between 2030-2040 has every chance of being a starting point in the development of energy based on helium-3, since by this time, apparently, the technological obstacles indicated above will be overcome. Accordingly, it remains to find money for the implementation of an energy project that is capable of moving humanity into an era of extremely cheap (almost free) energy with all the ensuing consequences, both for the economy and the quality of life of each person.

Candidate of Physical and Mathematical Sciences A. PETRUKOVICH.

With the light hand of the American president at the end of 2003, the issue of new goals for humanity in space was put on the agenda. The goal of creating a habitable station on the Moon, among other proposals, is partly based on the tempting idea of using the unique lunar reserves of helium-3 to generate energy on Earth. The future will tell whether lunar helium is useful or not, but the story about it is quite fascinating and allows us to compare our knowledge of the structure of the atomic nucleus and the solar system with the practical aspects of energy and mining.

Science and life // Illustrations

FOR WHAT? OR NUCLEAR fusion - ALCHEMY IN REALITY

Transforming lead into gold was the dream of medieval alchemists. As always, nature turned out to be richer than human imagination. Nuclear fusion reactions created all the diversity of chemical elements, laying the material foundations of our world. However, synthesis can also provide something much more valuable than gold - energy. Nuclear reactions in this sense are similar to chemical reactions (that is, reactions that transform molecules): each compound substance, be it a molecule or an atomic nucleus, is characterized by the binding energy that must be expended to destroy the compound, and which is released when it is formed. When the binding energy of the reaction products is higher than the starting materials, the reaction proceeds with the release of energy, and if you learn to take it in one form or another, the starting materials can be used as fuel. Of the chemical processes, the most effective in this sense, as is known, is the reaction of interaction with oxygen - combustion, which today serves as the main and irreplaceable source of energy in power plants, in transport and in everyday life (even more energy is released during the reaction of fluorine, especially molecular, with hydrogen ; however, both fluorine itself and hydrogen fluoride are extremely aggressive substances).

The binding energy of protons and neutrons in the nucleus is much greater than that which binds atoms into molecules, and it can literally be weighed using Einstein's great formula E = mc 2: the mass of the atomic nucleus is noticeably less than the masses of the individual protons and neutrons that make it up. Therefore, a ton of nuclear fuel replaces many millions of tons of oil. However, it is not for nothing that fusion is called thermonuclear: in order to overcome the electrostatic repulsion when two positively charged atomic nuclei come together, you need to properly accelerate them, that is, heat the nuclear fuel to hundreds of millions of degrees (remember that temperature is a measure of the kinetic energy of particles). In fact, at such temperatures we are no longer dealing with gases or liquids, but with the fourth state of matter - plasma, in which there are no neutral atoms, but only electrons and ions.

In nature, such conditions suitable for synthesis exist only in the interior of stars. The Sun owes its energy to the so-called helium cycle of reactions: the synthesis of the helium-4 nucleus from protons. In giant stars and during supernova explosions, heavier elements are also born, thus forming the entire diversity of elements in the Universe. (True, it is believed that part of the helium could have been formed directly at the birth of the Universe, during the Big Bang.) The sun in this sense is not the most efficient generator, because it burns for a long time and slowly: the process is slowed down by the first and slowest deuterium fusion reaction of the two protons. All the following reactions proceed much faster and immediately consume the available deuterium, converting it into helium nuclei in several stages. As a result, even if we assume that only one hundredth of the solar matter located in its core is involved in the fusion, the energy release is only 0.02 watts per kilogram. However, it is precisely this slowness, explained primarily by the small, by stellar standards, mass of the star (the Sun belongs to the category of subdwarfs) and ensuring the constancy of the flow of solar energy for many billions of years, which we owe to the very existence of life on Earth. In giant stars, the conversion of matter into energy is much faster, but as a result, they burn themselves out completely in tens of millions of years, without even having time to properly acquire planetary systems.

Having decided to carry out thermonuclear fusion in the laboratory, a person intends to outwit nature by creating a more efficient and compact energy generator than the Sun. However, we can choose a much more easily feasible reaction - the synthesis of helium from a deuterium-tritium mixture. It is planned that the projected international thermonuclear reactor - tokamak "ITER" will be able to reach the ignition threshold, from which, however, it is still very, very far from the commercial use of thermonuclear energy (see "Science and Life" No., , 2001). The main problem, as is known, is to keep the plasma heated to the required temperature. Since no wall at such a temperature can avoid destruction, they try to hold the plasma cloud with a magnetic field. In a hydrogen bomb, the problem is solved by the explosion of a small atomic charge, compressing and heating the mixture to the required condition, but this method is not suitable for peaceful energy production. (On the prospects of so-called explosive energy, see “Science and Life” No. 7, 2002)

The main disadvantage of the deuterium-tritium reaction is the high radioactivity of tritium, the half-life of which is only 12.5 years. This is the most radiation-dirty reaction available, so much so that in an industrial reactor the internal walls of the combustion chamber will need to be replaced every few years due to radiation destruction of the material. True, the most harmful radioactive waste, which requires indefinite burial deep underground due to the long decay time, is not formed at all during fusion. Another problem is that the energy released is carried away mainly by neutrons. These particles, which have no electrical charge, do not notice the electromagnetic field and generally interact poorly with matter, so it is not easy to take energy away from them.

Tritium-free fusion reactions, such as those involving deuterium and helium-3, are virtually radiation-safe because they use only stable nuclei and do not produce inconvenient neutrons. However, in order to “ignite” such a reaction, it is necessary, to compensate for the lower fusion rate, to heat the plasma ten times hotter - up to a billion degrees (at the same time solving the problem of confining it)! Therefore, today such options are considered as the basis for future thermonuclear reactors of the second generation, following the deuterium-tritium one. However, the idea of this alternative thermonuclear energy has acquired unexpected allies. Proponents of space colonization consider helium-3 to be one of the main economic goals of lunar expansion, which should meet humanity's needs for clean thermonuclear energy.

WHERE? OR SUNNY GUEST

At first glance, there should be no problem with where to get helium: it is the second most abundant element in the Universe, and the relative content of the light isotope in it is slightly less than one thousandth. However, for Earth, helium is exotic. It is a highly volatile gas. The Earth cannot hold it with its gravity, and almost all of the primary helium that fell on it from the protoplanetary cloud during the formation of the Solar System returned from the atmosphere back into space. Even helium was first discovered in the Sun, which is why it was named after the ancient Greek god Helios. It was later found in minerals containing radioactive elements, and finally caught in the atmosphere among other noble gases. Terrestrial helium is mainly not of cosmic origin, but of secondary, radiation origin: during the decay of radioactive chemical elements, alpha particles - helium-4 nuclei - are emitted. Helium-3 is not formed this way, and therefore its amount on Earth is negligible and literally amounts to kilograms.

You can stock up on helium of cosmic origin (with a relatively high content of helium-3) in the atmospheres of Uranus or Neptune - planets large enough to hold this light gas, or on the Sun. It turned out that it is easier to get to solar helium: the entire interplanetary space is filled with the solar wind, in which for every 70 thousand protons there are 3000 alpha particles - helium-4 nuclei and one helium-3 nucleus. This wind is extremely rarefied; by earthly standards it is a real vacuum, and it is impossible to catch it with a net (see Science and Life" No. 7, 2001). But solar plasma settles on the surface of celestial bodies that do not have a magnetosphere and atmosphere, for example on the Moon, and, therefore, it is possible to empty some natural trap that has been regularly replenished for the last four billion years. As a result of plasma bombardment, several hundred million tons of helium-3 fell on the Moon during this time. If all the solar wind remained on surface of the Moon, then in addition to 5 grams of helium 3, on each square meter of the surface there would be on average another 100 kilograms of hydrogen and 16 kilograms of helium 4. From this amount it would be possible to create a quite decent atmosphere, only slightly more rarefied than the Martian one, or an ocean of liquid gas two meters deep!

However, there is nothing like this on the Moon, and only a very small fraction of solar wind ions remain forever in the upper layer of lunar soil - regolith. Studies of lunar soil brought to Earth by the Soviet Luna probes and the American Apollo probes have shown that it contains approximately 1/100-millionth of helium-3, or 0.01 grams per ton. And in total there are about a million tons of this isotope on the Moon, which is a lot by earthly standards. At the current level of global energy consumption, lunar fuel would last for 10 thousand years, which is approximately ten times greater than the energy potential of all extractable chemical fuels (gas, oil, coal) on Earth.

HOW? OR "PER GRAM PRODUCTION, PER YEAR LABOR"

Unfortunately, there are no “lakes” of helium on the Moon; it is more or less evenly dispersed throughout the surface layer. Nevertheless, from a technical point of view, the mining process is quite simple and was developed in detail by enthusiasts of lunar colonization (see, for example, www.asi.org).

To meet the Earth's current annual energy needs, it is necessary to bring only about 100 tons of helium-3 from the Moon. It is this quantity, corresponding to three or four flights of space shuttles, that fascinates with its availability. However, first you need to dig up about a billion tons of lunar soil - not such a large amount by the standards of the mining industry: for example, two billion tons of coal are mined in the world per year (in Russia - about 300 million tons). Of course, the content of helium-3 in the rock is not too high: for example, the development of deposits is considered cost-effective if they contain at least several grams of gold, and diamonds - at least two carats (0.4 g) per ton. In this sense, helium-3 can only be compared with radium, of which only a few kilograms have been produced since the beginning of the twentieth century: after processing a ton of pure uranium, only 0.4 grams of radium is obtained, not to mention the problems of mining the uranium itself. At the beginning of the last century, during the period of a romantic attitude towards radioactivity, radium was quite popular and known not only to physicists, but also to lyricists: let us remember the phrase of V.V. Mayakovsky: “Poetry is the same as the production of radium. Production per gram, labor per year.” . But helium-3 is more expensive than almost any substance used by humans - one ton would cost at least a billion dollars, if we convert the energy potential of helium into an oil equivalent at the bargain price of $7 per barrel.

The gas is easily released from regolith heated to several hundred degrees, say, with the help of a solar concentrator mirror. Let's not forget that helium-3 still needs to be separated from a much larger number of other gases, mainly helium-4. This is done by cooling the gases to a liquid state and taking advantage of the slight difference in boiling points of isotopes (4.22 K for helium-4 or 3.19 K for helium-3). Another elegant separation method is based on the use of the superfluidity property of liquid helium-4, which can independently flow through a vertical wall into an adjacent container, leaving behind only non-superfluid helium-3 (see "Science and Life" No. 2, 2004).

Alas, all this will have to be done in airless space, not in the “greenhouse” conditions of the Earth, but on the Moon. Several mining cities will have to be relocated there, which, in essence, means colonizing the Moon. Now hundreds of specialists are monitoring the safety of several astronauts in low-Earth orbit, and the crew can return to Earth at any time. If tens of thousands of people end up in space, they will have to live in a vacuum on their own, without detailed supervision from Earth, and provide themselves with water, air, fuel, and basic building materials. However, there is enough hydrogen, oxygen and metals on the Moon. Many of them can be obtained as a by-product of helium mining. Then, probably, helium-3 could become a profitable commodity for trade with the Earth. But since people in such difficult conditions will need much more energy than earthlings, the lunar reserves of helium-3 may not seem so limitless and attractive to our descendants.

By the way, there is an alternative solution for this case. If engineers and physicists find a way to cope with holding helium plasma ten times hotter than what is needed for a modern tokamak (a task that now seems absolutely fantastic), then by increasing the temperature by just two times more, we will “ignite” the reaction synthesis involving protons and boron. Then all problems with fuel will be solved, and at a much lower price: there is more boron in the earth’s crust than, for example, silver or gold, it is widely used as an additive in metallurgy, electronics, and chemistry. Mining and processing plants produce hundreds of thousands of tons of various boron-containing salts per year, and if we do not have enough reserves on land, then every ton of sea water contains several grams of boron. And anyone who has a bottle of boric acid in their home medicine cabinet can consider that they have their own energy reserve for the future.

Literature

Bronstein M.P. Solar substance. - Terra Book Club, 2002.

Lunar soil from the sea of abundance. - M.: Nauka, 1974.

Captions for illustrations

Ill. 1. The helium cycle of nuclear fusion reactions begins with the fusion of two protons into a deuterium nucleus. In subsequent stages, more complex nuclei are formed. Let us write down the first few simplest reactions that we will need later.
p + p → D + e - + n
D + D → T + p or
D + D → 3 He + n
D + T → 4 He + n
D + 3 He → 4 He +2p
p + 11 Be → 3 4 He
The reaction rate is determined by the probability of overcoming the electrostatic barrier when two positively charged ions approach each other and the probability of nuclear fusion itself (the so-called interaction cross section). In particular, the higher the kinetic energy of the nucleus and the lower its electrical charge, the greater the chance of passing the electrostatic barrier and the higher the reaction rate (see graph). The key parameter of the theory of thermonuclear energy - the reaction ignition criterion - determines at what density and temperature of the plasma fuel the energy released during fusion (proportional to the reaction rate multiplied by the plasma density and combustion time) will exceed the cost of heating the plasma, taking into account losses and efficiency . The reaction of deuterium and tritium has the highest speed, and in order to achieve ignition, a plasma with a concentration of about 10 14 cm -3 must be heated to one and a half hundred million degrees and held for 1-2 seconds. To achieve a positive energy balance in reactions involving other components - helium-3 or boron, the lower speed must be compensated by increasing the temperature and density of the plasma tens of times. But a successful collision of two nuclei releases energy that is a thousand times greater than the energy spent on heating them. The initial reactions of the helium cycle, which form deuterium and tritium in the solar core, proceed so slowly that the corresponding curves are not included in the field of this graph.

Ill. 2. The solar wind is a stream of rarefied plasma that constantly flows from the solar surface into interplanetary space. The wind carries away only about 3x10 -14 solar masses per year, but it turns out to be the main component of the interplanetary medium, displacing interstellar plasma from the vicinity of the Sun. This is how the heliosphere is created - a kind of bubble with a radius of about one hundred astronomical units, moving along with the Sun through interstellar gas. As astronomers hope, the American satellites Voyager 1 and Voyager 2 are now approaching its border, which will soon become the first spacecraft to leave the solar system. The solar wind was first discovered by the Soviet interplanetary station Luna-2 in 1959, but indirect evidence of the presence of a corpuscular flow coming from the Sun was known earlier. It is to the solar wind that the inhabitants of the Earth are responsible for magnetic storms (see “Science and Life” No. 7, 2001). Near the Earth's orbit, the wind contains on average only six ions per cubic centimeter, moving at a mind-boggling speed of 450 km/s, which, however, on the scale of the solar system is not so fast: it takes three days to travel to Earth. The solar wind is 96% protons and 4% helium nuclei. The admixture of other elements is insignificant.

Ill. 3. Lunar regolith is a rather loose layer on the surface of the Moon several meters thick. It mainly consists of small debris with an average size of less than a millimeter, accumulated over billions of years as a result of the destruction of lunar rocks by temperature changes and meteorite impacts. Studies of lunar soil have shown that the more titanium oxides in the regolith, the more helium atoms.

Ill. 4. The presence of titanium in the near-surface layer is quite easily detected by remote spectroscopic analysis (red color in the right image of the figure obtained by the Clementine satellite), and thus a map of helium “deposits” is obtained, which, in general, coincides with the location of the lunar seas.

Ill. 5. To extract one ton of helium-3, it is necessary to process the surface layer of regolith over an area of at least 100 square kilometers. Along the way, it will be possible to obtain a significant amount of other gases that will be useful for arranging life on the Moon. Pictures taken from the site