Let's say the Earth is ending. The sun is about to explode, and an asteroid the size of Texas is approaching the planet. Big cities inhabited by zombies, and rural areas farmers are planting corn intensively because other crops are dying. We urgently need to leave the planet, but the problem is that no wormholes have been discovered in the Saturn region, and no superluminal engines have been brought from a galaxy far, far away. The nearest star is more than four light years away. Will humanity be able to achieve it, having modern technologies? The answer is not so obvious.

It is unlikely that anyone would argue that a global environmental disaster that would threaten the existence of all life on Earth can only happen in the movies. Have happened on our planet more than once mass extinctions, during which up to 90% of existing species died. The Earth experienced periods of global glaciation, collided with asteroids, and went through bursts of volcanic activity.

Of course, even during the most terrible disasters, life never completely disappeared. But the same cannot be said about the dominant species at that time, which died out, making way for others. Who is the dominant species now? Exactly.

It is likely that the opportunity to leave your home and go to the stars in search of something new can someday save humanity. However, we should hardly hope that some cosmic benefactors will open the way to the stars for us. It’s worth calculating what our theoretical capabilities are to reach the stars on our own.

Space Ark

First of all, traditional chemical traction engines come to mind. At the moment, four earthly vehicles (all of them were launched back in the 1970s) have managed to develop a third escape velocity, sufficient to leave the solar system forever.

The fastest of them, Voyager 1, has moved away from Earth to a distance of 130 AU in the 37 years since its launch. (astronomical units, that is, 130 distances from the Earth to the Sun). Each year the device travels approximately 3.5 AU. The distance to Alpha Centauri is 4.36 light years, or 275,725 AU. At this speed, the device will take almost 79 thousand years to reach the neighboring star. To put it mildly, it will be a long wait.

Photo of the Earth (above the arrow) from a distance of 6 billion kilometers, taken by Voyager 1. This is the distance spacecraft passed in 13 years.

You can find a way to fly faster, or you can just resign yourself and fly for several thousand years. Then only the distant descendants of those who went on the journey will reach the final point. This is precisely the idea of ​​the so-called generation ship - a space ark, which is a closed ecosystem designed for a long journey.

There are many different stories about generation ships in science fiction. Harry Garrison (“Captured Universe”), Clifford Simak (“Generation That Achieved the Goal”), Brian Aldiss (“Non Stopping”), and among more modern writers Bernard Werber (“Star Butterfly”) wrote about them. Quite often, distant descendants of the first inhabitants completely forget about where they flew from and what the purpose of their journey was. Or even begin to believe that all existing world comes down to a ship, as, for example, in Robert Heinlein's novel Stepsons of the Universe. Another interesting plot is shown in the eighth episode of the third season of the classic Star Trek, where the crew of the Enterprise tries to prevent a collision between a generation ship, whose inhabitants have forgotten about their mission, and the inhabited planet to which it was heading.

The advantage of the generation ship is that this option will not require fundamentally new engines. However, it will be necessary to develop a self-sustaining ecosystem that can survive without external supplies for many thousands of years. And don’t forget that people can simply kill each other.

The Biosphere-2 experiment, conducted in the early 1990s under a closed dome, demonstrated a number of dangers that can await people during such travel. This includes the rapid division of the team into several groups hostile to each other, and the uncontrolled proliferation of pests, which caused a lack of oxygen in the air. Even ordinary wind, as it turns out, plays a crucial role - without regular swaying, trees become fragile and break.

Technology that immerses people in long-term suspended animation will help solve many of the problems of long-term flight. Then neither conflicts nor boredom are scary, and a minimal life support system will be required. The main thing is to provide it with energy for a long time. For example, using a nuclear reactor.

Related to the theme of the generation ship is a very interesting paradox called Wait Calculation, described by scientist Andrew Kennedy. According to this paradox, for some time after the first generation ship departs, new, faster modes of travel may be discovered on Earth, allowing later ships to overtake the original settlers. So it is possible that by the time of arrival the destination will already be overpopulated by the distant descendants of the colonizers who went later.

Installations for suspended animation in the film "Alien".

Riding a nuclear bomb

Suppose we are not satisfied that the descendants of our descendants will reach the stars, and we ourselves want to expose our face to the rays of someone else’s sun. In this case, one cannot do without a spaceship capable of accelerating to speeds that will deliver it to a neighboring star in less than one human lifetime. And here the good old nuclear bomb will help.

The idea of ​​such a ship appeared in the late 1950s. The spacecraft was intended for flights within the solar system, but it could also be used for interstellar travel. The principle of its operation is as follows: a powerful armored plate is installed behind the stern. Low-power nuclear charges are uniformly ejected from the spacecraft in the direction opposite to the flight, which are detonated at a short distance (up to 100 meters).

The charges are designed in such a way that most of the explosion products are directed towards the tail of the spacecraft. The reflective plate receives the impulse and transmits it to the ship through the shock absorber system (without it, overloads will be detrimental to the crew). The reflective plate is protected from damage by light flash, gamma radiation and high-temperature plasma by a coating of graphite lubricant, which is re-sprayed after each detonation.

The NERVA project is an example of a nuclear rocket engine.

At first glance, such a scheme seems crazy, but it is quite viable. During one of nuclear tests On Enewetak Atoll, graphite-coated steel spheres were placed 9 meters from the center of the explosion. After testing, they were found undamaged, which proves the effectiveness of graphite protection for the ship. But the Test Ban Treaty signed in 1963 nuclear weapons in the atmosphere outer space and under water" put an end to this idea.

Arthur Clarke wanted to equip spaceship Discovery One from the movie "2001: A Space Odyssey" is something like a nuclear explosion engine. However, Stanley Kubrick asked him to abandon the idea, fearing that audiences would consider it a parody of his film Dr. Strangelove, or How I Stopped Being Scared and Loved the Atom Bomb.

What speed can be achieved using a series of nuclear explosions? Most information exists about the Orion explosion project, which was developed in the late 1950s in the USA with the participation of scientists Theodore Taylor and Freeman Dyson. The 400,000-ton ship was planned to accelerate to 3.3% of the speed of light - then the flight to the Alpha Centauri system would last 133 years. However, according to current estimates, in a similar way it is possible to accelerate the ship to 10% of the speed of light. In this case, the flight will last approximately 45 years, which will allow the crew to survive until they arrive at their destination.

Of course, building such a ship is a very expensive undertaking. Dyson estimates that Orion would cost approximately $3 trillion in today's dollars to build. But if we find out that our planet is facing a global catastrophe, then it is likely that a ship with a nuclear pulse engine will be humanity’s last chance for survival.

Gas giant

A further development of the Orion ideas was the project of the unmanned spacecraft Daedalus, which was developed in the 1970s by a group of scientists from the British Interplanetary Society. The researchers set out to design an unmanned spacecraft capable of reaching one of the nearest stars during a human lifetime, conducting scientific research and transmitting the information received to Earth. The main condition of the study was the use of either existing or foreseeable technologies in the project.

The target of the flight was Barnard's Star, located at a distance of 5.91 light years from us - in the 1970s it was believed that several planets revolved around this star. We now know that there are no planets in this system. The Daedalus developers set their sights on creating an engine that could deliver the ship to its destination in no more than 50 years. As a result, they came up with the idea of ​​a two-stage apparatus.

The necessary acceleration was provided by a series of low-power nuclear explosions occurring inside a special propulsion system. Microscopic granules of a mixture of deuterium and helium-3, irradiated with a stream of high-energy electrons, were used as fuel. According to the project, up to 250 explosions per second were supposed to occur in the engine. The nozzle was a powerful magnetic field created by the ship's power plants.

According to the plan, the first stage of the ship operated for two years, accelerating the ship to 7% the speed of light. The Daedalus then jettisoned its spent propulsion system, removing most of its mass, and fired its second stage, which allowed it to accelerate to a final speed of 12.2% lightspeed. This would make it possible to reach Barnard's Star 49 years after launch. It would take another 6 years to transmit the signal to Earth.

The total mass of the Daedalus was 54 thousand tons, of which 50 thousand were thermonuclear fuel. However, the supposed helium-3 is extremely rare on Earth - but it is abundant in the atmospheres of gas giants. Therefore, the authors of the project intended to extract helium-3 on Jupiter using an automated plant “floating” in its atmosphere; the entire mining process would take approximately 20 years. In the same orbit of Jupiter it was planned to carry out final assembly ship, which would then launch to another star system.

The most difficult element in the entire Daedalus concept was precisely the extraction of helium-3 from the atmosphere of Jupiter. To do this, it was necessary to fly to Jupiter (which is also not so easy and fast), establish a base on one of the satellites, build a plant, store fuel somewhere... And this is not to mention the powerful radiation belts around the gas giant, which additionally would make life more difficult for technology and engineers.

Another problem was that Daedalus did not have the ability to slow down and enter orbit around Barnard's Star. The ship and the probes it launched would simply pass by the star along the flyby path, covering the entire system in a few days.

Now an international group of twenty scientists and engineers, operating under the auspices of the British Interplanetary Society, is working on the Icarus spacecraft project. “Icarus” is a kind of “remake” of Daedalus, taking into account the knowledge and technology accumulated over the past 30 years. One of the main areas of work is the search for other types of fuel that could be produced on Earth.

At the speed of light

Is it possible to accelerate a spaceship to the speed of light? This problem can be solved in several ways. The most promising of them is an antimatter annihilation engine. The principle of its operation is as follows: antimatter is fed into the working chamber, where it comes into contact with ordinary matter, generating a controlled explosion. The ions generated during the explosion are ejected through the engine nozzle, creating thrust. Of all possible engines, annihilation theoretically allows one to achieve the highest speeds. The interaction of matter and antimatter releases a colossal amount of energy, and the speed of the outflow of particles formed during this process is close to that of light.

But here the question of fuel extraction arises. Antimatter itself has long ceased to be science fiction - scientists first managed to synthesize antihydrogen back in 1995. But it is impossible to obtain it in sufficient quantities. Currently, antimatter can only be produced using particle accelerators. Moreover, the amount of substance they create is measured in tiny fractions of grams, and its cost is astronomical. For one billionth of a gram of antimatter, scientists from European Center nuclear research (the same one where the Large Hadron Collider was created) had to spend several hundred million Swiss francs. On the other hand, the cost of production will gradually decrease and in the future may reach much more acceptable values.

In addition, we will have to come up with a way to store antimatter - after all, upon contact with ordinary matter, it is instantly annihilated. One solution is to cool the antimatter to ultra-low temperatures and use magnetic traps to prevent it from coming into contact with the walls of the tank. On this moment The record storage time for antimatter is 1000 seconds. Not years, of course, but taking into account the fact that the first time antimatter was contained for only 172 milliseconds, there is progress.

And even faster

Numerous science fiction films have taught us that it is possible to get to other star systems much faster than in a few years. It is enough to turn on the warp engine or hyperspace drive, sit back comfortably in your chair - and within a few minutes you will find yourself on the other side of the galaxy. The theory of relativity prohibits travel at speeds exceeding the speed of light, but at the same time leaves loopholes to circumvent these restrictions. If they could tear apart or stretch space-time, they could travel faster than light without breaking any laws.

A gap in space is better known as a wormhole or wormhole. Physically, it is a tunnel connecting two remote regions of space-time. Why not use such a tunnel to travel to deep space? The fact is that the creation of such a wormhole requires the presence of two singularities at different points in the universe (this is what is located beyond the event horizon of black holes - in fact, gravity in its purest form), which can tear apart space-time, creating a tunnel that allows travelers to " shortcut through hyperspace.

In addition, to maintain such a tunnel in a stable state, it must be filled with exotic matter with negative energy, and the existence of such matter has not yet been proven. In any case, only a supercivilization can create a wormhole, which will be many thousands of years ahead of the current one in development and whose technologies, from our point of view, will look like magic.

The second, more affordable option is to “stretch” the space. In 1994, Mexican theoretical physicist Miguel Alcubierre proposed that it was possible to change its geometry by creating a wave that compresses the space in front of the ship and expands it behind. Thus, the starship will be in a “bubble” of curved space, which itself will move faster than light, thanks to which the ship will not violate the fundamental physical principles. According to Alcubierre himself, .

True, the scientist himself considered that it would be impossible to implement such a technology in practice, since this would require a colossal amount of mass-energy. The first calculations gave values ​​exceeding the mass of the entire existing Universe, subsequent refinements reduced it to “only” Jupiterian.

But in 2011, Harold White, who heads research group Eagleworks at NASA carried out calculations that showed that if you change some parameters, then creating an Alcubierre bubble may require much less energy than previously thought, and it will no longer be necessary to recycle the entire planet. Now White's group is working on the possibility of an "Alcubierre bubble" in practice.

If the experiments yield results, this will be the first small step towards creating an engine that allows travel 10 times faster than the speed of light. Of course, a spacecraft using the Alcubierre bubble will travel many tens, or even hundreds of years later. But the very prospect that this is actually possible is already breathtaking.

Flight of the Valkyrie

Almost all proposed starship projects have one significant drawback: They weigh tens of thousands of tons, and their creation requires a huge number of launches and assembly operations in orbit, which increases the cost of construction by an order of magnitude. But if humanity still learns to receive a large number of antimatter, he will have an alternative to these bulky structures.

In the 1990s, writer Charles Pelegrino and physicist Jim Powell proposed a starship design known as Valkyrie. It can be described as something like a space tractor. The ship is a combination of two annihilation engines connected to each other by a super-strong cable 20 kilometers long. In the center of the bundle there are several compartments for the crew. The ship uses the first engine to reach near light speed, and the second to reduce it when entering orbit around the star. Thanks to the use of a cable instead of a rigid structure, the mass of the ship is only 2,100 tons (for comparison, the ISS weighs 400 tons), of which 2,000 tons are engines. Theoretically, such a ship can accelerate to a speed of 92% of the speed of light.

A modified version of this ship, called the Venture Star, is shown in the film Avatar (2011), for which Charles Pelegrino was one of the scientific consultants. Venture Star sets off on a journey, propelled by lasers and a 16-kilometer solar sail, before stopping at Alpha Centauri using an antimatter engine. On the way back the sequence changes. The ship is capable of accelerating to 70% the speed of light and reaching Alpha Centauri in less than 7 years.

No fuel

Both existing and future rocket engines have one problem - fuel always makes up the majority of their mass at launch. However, there are starship projects that will not need to take fuel with them at all.

In 1960, physicist Robert Bussard proposed the concept of an engine that would use hydrogen found in interstellar space as fuel for a fusion engine. Unfortunately, despite the attractiveness of the idea (hydrogen is the most common element in the Universe), it has a number of theoretical problems, ranging from the method of collecting hydrogen to the calculation maximum speed, which is unlikely to exceed 12% light. This means that it will take at least half a century to fly to the Alpha Centauri system.

Another interesting concept is the use of a solar sail. If a huge, super-powerful laser was built in Earth orbit or on the Moon, its energy could be used to accelerate a starship equipped with a giant solar sail to fairly high speeds. True, according to engineers’ calculations, in order to give a manned ship weighing 78,500 tons half the speed of light, a solar sail with a diameter of 1000 kilometers will be required.

Another obvious problem with a starship with a solar sail is that it needs to be slowed down somehow. One of its solutions is to release a second, smaller sail behind the starship when approaching the target. The main one will disconnect from the ship and continue its independent journey.

***

Interstellar travel is a very complex and expensive undertaking. Creating a ship capable of covering space distance in a relatively short period of time is one of the most ambitious tasks facing humanity in the future. Of course, this will require the efforts of several states, if not the entire planet. Now this seems like a utopia - governments have too many things to worry about and too many ways to spend money. A flight to Mars is millions of times simpler than a flight to Alpha Centauri - and yet, it is unlikely that anyone will dare to name the year when it will take place.

Work in this direction can be revived either by a global danger threatening the entire planet, or by the creation of a single planetary civilization that can overcome internal squabbles and wants to leave its cradle. The time for this has not yet come - but this does not mean that it will never come.

Interstellar flight - travel between stars by manned vehicles or automatic stations. Most often, interstellar flight refers to manned travel, sometimes with possible colonization extrasolar planets.

The construction of a squadron of interstellar ships will begin at the Lagrange points of the Earth-Moon system (points of gravitational equilibrium). Materials for the most part can be delivered from lunar bases - for example, containers with them are fired electromagnetic guns and are captured by special trap stations in the construction area. The engine for an interstellar ship must have the same order of power as all the power consumed by humanity today. Based on foreseeable technologies and resource capabilities, it is possible to provide an outline of future interstellar travel.

When considering a spacecraft for any purpose, it is convenient to divide it into two parts - the propulsion system and the payload. The propulsion system usually means not only the engines themselves, but also fuel tanks and the necessary power structures. For the problems of interstellar travel, it is the propulsion system that is key factor, which determines the feasibility of the project. However, the problems of creating a propulsion system are beyond the scope of this consideration. What is important for us now is that there are technologies that, in the course of their development, can become acceptable for interstellar flights. Here the technology of using inertial thermonuclear fusion for rocket propulsion comes first. The American NIF (National Ignition Facility) installation for researching laser thermonuclear fusion worth 3.5 billion dollars has already obtained results indicating that a rocket engine can be created on this principle. An even more powerful installation of this type is being built near Sarov. These installations bear little resemblance to rocket engines, but if we roughly “cut” them in half, get rid of foundations, walls and a lot of equipment unnecessary in space, we will get a rocket engine that can be upgraded to an interstellar version. Without going into detail, we note that such engines will necessarily be large, heavy and very powerful. The engine for an interstellar ship must have the same order of power as all the power consumed by humanity today. Having such an engine (and if there is no such engine, then there is nothing to talk about), you can feel more free when considering the parameters of the payload. By analogy, if an extra 50 kg is already noticeable for a cyclist, then a diesel locomotive won’t even notice the extra 50 tons.

Armed with this understanding, we can try to imagine the first interstellar expedition. In this case, you will have to use the results of calculations and estimates that have been made, but here, for obvious reasons, cannot be reproduced.

The construction of a squadron of interstellar ships will begin at the Lagrange points of the Earth-Moon system (points of gravitational equilibrium). Materials, for the most part, can be delivered from lunar bases - for example, containers with them are fired by electromagnetic guns and captured by special trap stations in the construction area.

One ship means hundreds of thousands of tons of payload, millions of tons of engines, tens of millions of tons of fuel. The numbers can be intimidating, but to avoid being too intimidated, they can be compared to other major construction projects. A long time ago, in 20 years, the Cheops pyramid weighing more than 6 million tons was built. Or already in our times - in Canada in 1965, North Dame Island was built. Only 15 million tons of soil was required, and construction took only 10 months. The largest sea ship - Knock Nevis - had a displacement of 825,614 tons. Construction in space has its own specific difficulties, but it also has some advantages, for example, lightening of power elements due to weightlessness, the virtual absence of restrictions on mass and size (on Earth, a large enough structure will simply crush itself).

Approximately 95% of the mass of the interstellar ship will be thermonuclear fuel. Probably, borohydrides will be used as fuel, the fuel will be solid, tanks will not be needed, which greatly improves the characteristics of the ship and facilitates its construction. It is better to collect borohydrides not in the Earth-Moon system, but somewhere away from the Sun, in the Saturn system, for example, to avoid losses due to sublimation. Construction time can be estimated at several decades. The period is not so long, and in addition, the same builders will simultaneously carry out other work as part of the development of the Solar system. It is better to start construction with the construction of the ship’s residential blocks, in which builders and other specialists will live. At the same time, during construction and accumulation of fuel, the stability of the closed life support system will be tested for decades.

A closed life support system is probably the second most difficult issue after the engine problem. One person consumes approximately 5 kg of water, food and air per day; if you take everything with you, you will need more than 200 thousand tons of supplies. Solution - reuse resources as it happens on planet Earth.

The full scale of interstellar flight distances can only be experienced if we consider the means of carrying out such flights. Of course, such consideration is not intended to “feel the distance.” Nor can it be considered as the design of a specific design of interstellar ships. The study of interstellar travel today is of an engineering and theoretical nature. It is impossible to prove the impossibility of interstellar flights, but no one has been able to prove their feasibility. The way out of the situation is not easy - it is necessary to propose a design for interstellar spacecraft that would be accepted by the engineering and scientific community as feasible.

Flights of single interstellar ships, which are the rule in science fiction literature, are excluded; flights of only a squadron of ships, about a dozen vehicles, are possible. This is a safety requirement, and in addition, it also ensures the diversity of life through communication between the crews of different ships.

Once the construction of the squadron is completed, it moves to the stored fuel reserves, docks with them and heads off. Apparently, the acceleration will be very slow and within a year or two more mobile devices will be able to throw onto ships what they forgot and take off those who have changed their minds.

The flight will last 100-150 years. Slow acceleration with an acceleration of approximately a hundredth of the earth's over ten years, tens of years of flight by inertia, and deceleration somewhat faster than acceleration. Fast acceleration would significantly reduce the flight time, but it is not possible due to the inevitably large mass of the propulsion system.

The flight will not be as full of space adventures as described in science fiction literature. There are practically no external threats. Clouds of cosmic dust, turbulence in space, gaps in time - all these paraphernalia do not pose a threat due to their absence. Even trivial meteorites are extremely rare in interstellar space. Main external problem- galactic cosmic radiation, cosmic rays. This is an isotropic flow of nuclei of elements having high energy and, therefore, high penetrating ability. On Earth we are protected from them by the atmosphere and magnetic field; in space, if the flight is long, we must take special measures, shield residential area ship so that the dose of cosmic radiation does not greatly exceed the terrestrial level. A simple design technique will help here - fuel reserves (and they are very large) are located around the living compartments and shield them from radiation most of the flight time.

The answer will require a long article, although it can be answered with a single character: c .

The speed of light in a vacuum, c , is equal to approximately three hundred thousand kilometers per second and cannot be exceeded. Therefore, it is impossible to reach the stars faster than in a few years (light travels 4.243 years to Proxima Centauri, so the spacecraft cannot arrive even faster). If you add the time for acceleration and deceleration with acceleration more or less acceptable for humans, you get about ten years to the nearest star.

What are the conditions to fly in?

And this period is already a significant obstacle in itself, even if we ignore the question “how to accelerate to a speed close to the speed of light.” Now there are no spaceships that allowed the crew to live autonomously in space for so long - the astronauts are constantly brought fresh supplies from Earth. Usually, conversations about the problems of interstellar travel begin with more fundamental questions, but we will start with purely applied problems.

Even half a century after Gagarin’s flight, engineers were unable to create a washing machine and a sufficiently practical shower for spacecraft, and toilets designed for weightlessness break down on the ISS with enviable regularity. A flight to at least Mars (22 light minutes instead of 4 light years) already poses a non-trivial task for plumbing designers: so for a trip to the stars it will be necessary to at least invent a space toilet with a twenty-year guarantee and the same washing machine.

Water for washing, washing and drinking will also have to be either taken with you or reused. As well as air, and food also needs to be either stored or grown on board. Experiments to create a closed ecosystem on Earth have already been carried out, but their conditions were still very different from space ones, at least in the presence of gravity. Humanity knows how to turn the contents of a chamber pot into clean drinking water, but in this case it is necessary to be able to do this in zero gravity, with absolute reliability and without a truck Supplies: Taking a truckload of filter cartridges to the stars is too expensive.

Washing socks and protecting from intestinal infections may seem too banal, “non-physical” restrictions on interstellar flights - however, any experienced traveler will confirm that “little things” like uncomfortable shoes or stomach upset from unfamiliar food on an autonomous expedition can turn into a threat to life.

Solving even the most basic everyday problems requires the same serious technological base as the development of fundamentally new space engines. If on Earth a worn-out gasket in a toilet tank can be bought at the nearest store for two rubles, then on the Martian ship it is necessary to provide either a supply of all such parts, or a three-dimensional printer for the production of spare parts from universal plastic raw materials.

The US Navy got serious about 3D printing in 2013 after assessing the time and cost involved in repairing military equipment. traditional methods in the field. The military reasoned that printing some rare gasket for a helicopter component that had been discontinued ten years ago was easier than ordering a part from a warehouse on another continent.

One of Korolev’s closest associates, Boris Chertok, wrote in his memoirs “Rockets and People” that at a certain point the Soviet space program faced a shortage plug contacts. Reliable connectors for multi-core cables had to be developed separately.

In addition to spare parts for equipment, food, water and air, astronauts will need energy. The engine and on-board equipment will need energy, so the problem of a powerful and reliable source will have to be solved separately. Solar batteries are not suitable, if only because of the distance from the stars in flight, radioisotope generators (they power Voyagers and New Horizons) do not provide the power required for a large manned spacecraft, and they have not yet learned how to make full-fledged nuclear reactors for space.

The Soviet nuclear-powered satellite program was marred by an international scandal following the crash of Cosmos 954 in Canada, as well as a series of failures with less dramatic consequences; similar works in the USA they stopped even earlier. Now Rosatom and Roscosmos intend to create a space nuclear power plant, but these are still installations for short-range flights, and not a multi-year journey to another star system.

Perhaps instead of a nuclear reactor, future interstellar spacecraft will use tokamaks. This summer, MIPT gave a whole lecture to everyone about how difficult it is to even correctly determine the parameters of thermonuclear plasma. By the way, the ITER project on Earth is progressing successfully: even those who entered the first year today have every chance to join the work on the first experimental thermonuclear reactor with a positive energy balance.

What to fly?

Conventional rocket engines are not suitable for accelerating and decelerating an interstellar ship. Those familiar with the mechanics course taught at MIPT in the first semester can independently calculate how much fuel a rocket will need to reach at least one hundred thousand kilometers per second. For those who are not yet familiar with the Tsiolkovsky equation, we will immediately announce the result - the mass of fuel tanks turns out to be significantly higher than the mass of the Solar system.

The fuel supply can be reduced by increasing the speed at which the engine emits the working fluid, gas, plasma or something else, up to a beam of elementary particles. Currently, plasma and ion engines are actively used for flights of automatic interplanetary stations within the Solar System or for correction of the orbit of geostationary satellites, but they have a number of other disadvantages. In particular, all such engines provide too little thrust; they cannot yet give the ship an acceleration of several meters per second squared.

MIPT Vice-Rector Oleg Gorshkov is one of the recognized experts in the field of plasma engines. SPD series engines are produced at the Fakel Design Bureau; these are serial products for orbit correction of communication satellites.

In the 1950s, an engine project was developed that would use the impulse of a nuclear explosion (the Orion project), but it was also far from becoming ready-made solution for interstellar flights. Even less developed is the design of an engine that uses the magnetohydrodynamic effect, that is, accelerates due to interaction with interstellar plasma. Theoretically, a spacecraft could “suck” plasma inside and throw it back out to create jet thrust, but this poses another problem.

How to survive?

Interstellar plasma is primarily protons and helium nuclei, if we consider heavy particles. When moving at speeds of the order of hundreds of thousands of kilometers per second, all these particles acquire energy of megaelectronvolts or even tens of megaelectronvolts - the same amount as the products of nuclear reactions. The density of the interstellar medium is about one hundred thousand ions per cubic meter, which means that in a second square meter the ship's hull will receive about 10 13 protons with energies of tens of MeV.

One electron volt, eV, is the energy that an electron acquires when flying from one electrode to another with a potential difference of one volt. Light quanta have this energy, and ultraviolet quanta with higher energy are already capable of damaging DNA molecules. Radiation or particles with energies of megaelectronvolts accompanies nuclear reactions and, in addition, is itself capable of causing them.

Such irradiation corresponds to an absorbed energy (assuming that all energy is absorbed by the skin) of tens of joules. Moreover, this energy will not just come in the form of heat, but may partially be used to initiate nuclear reactions in the ship’s material with the formation of short-lived isotopes: in other words, the lining will become radioactive.

Some of the incident protons and helium nuclei can be deflected to the side magnetic field, induced radiation and secondary radiation can be protected by a complex shell of many layers, but these problems also have no solution yet. In addition, fundamental difficulties of the form “which material will be least destroyed when irradiated” at the stage of servicing the ship in flight will turn into particular problems - “how to unscrew four 25 bolts in a compartment with a background of fifty millisieverts per hour.”

Let us recall that during the last repair of the Hubble telescope, the astronauts initially failed to unscrew the four bolts that secured one of the cameras. After consulting with the Earth, they replaced the torque-limiting key with a regular one and applied brute force. The bolts moved out of place, the camera was successfully replaced. If the stuck bolt had been removed, the second expedition would have cost half a billion US dollars. Or it wouldn’t have happened at all.

Are there any workarounds?

In science fiction (often more fantasy than science), interstellar travel is accomplished through “subspace tunnels.” Formally, Einstein's equations, which describe the geometry of space-time depending on the mass and energy distributed in this space-time, really allow something similar - only the estimated energy costs are even more depressing than the estimates of the quantity rocket fuel for a flight to Proxima Centauri. Not only do you need a lot of energy, but also the energy density must be negative.

The question of whether it is possible to create a stable, large and energetically possible “wormhole” is tied to fundamental questions about the structure of the Universe as a whole. One of the unresolved problems in physics is the absence of gravity in the so-called Standard Model, a theory that describes the behavior of elementary particles and three of the four fundamental physical interactions. The vast majority of physicists are quite skeptical that in the quantum theory of gravity there will be a place for interstellar “jumps through hyperspace”, but, strictly speaking, no one forbids trying to look for a workaround for flights to the stars.

We became acquainted with the possible physical differences between us and our cosmic brethren. Now let's move on to what may be more significant for us - intellectual differences. This problem can be formulated as follows.

Riddle 1. Have other civilizations overtaken us in their development or have they lagged behind us?

Let us assume that in our Galaxy there are at least a million “doubles” of the Earth on which there exists intelligent life. They were formed in different eras - millions of years earlier or later than ours - and, therefore, are at different stages of development. The times of dinosaurs, prehistoric man, the early Roman Empire - all these eras of Earth's history are currently, perhaps, being "copied", and simultaneously on several planets. It is possible that, in turn, we on Earth are now experiencing an era that other worlds passed thousands or even millions of years ago.

How many civilizations have surpassed us in their development? And how much? What Pozin says about this is not at all comforting to our pride. The Earth cannot be considered a high or even medium degree development. Most likely we occupy a stage not too far from lower end of the evolutionary scale. This follows from a simple and, as it seems to us, undeniable logic.

Astronomers believe that our Sun's energy will last for at least 10 billion years. Adding this number to the age of the Earth, estimated at 5 billion years, we get the total lifetime of the Earth - 15 billion years. 2.5 billion years passed before the origin of life on Earth, and the same amount before the appearance of man, which in total amounts to 1/3 of the 15 billion years “allocated” to the Earth’s share. Man, whose traces of an uncivilized predecessor can only be traced back a million years, emerged from the caves and began to join civilization at most 12,000 years ago. Consequently, 10 billion years remain for the further development of humanity.

If the “lifespan” of a million other planets like Earth is also 15 billion years, they average age- 7.5 billion years, and the average age of civilizations is 2.5 billion years. But about half of these Earth twins, roughly 500,000 planets, are even older.

Since we are near the bottom rung of the underdeveloped half, we are probably superior to about 50,000 civilizations, but inferior to 950,000 others. Those whose age is 10 billion years (just think - millions of centuries!) and who have reached unimaginable heights in mental development, without a doubt, would place us earthlings no higher than skilled ants living in colonies and displaying dubious intelligence.

However, our calculations of habitable worlds may be erroneous. It is possible that on many planets conditions prevent the emergence of life. It is likely that some civilizations encountered obstacles in the process of evolution and were able to develop normally only after long delay. Some stars flared up prematurely as novae, thereby causing irreparable damage to the habitable planets that orbit around them. And who knows how many civilizations perished in the fire of atomic wars?

But even hundreds and thousands of such restrictions will not significantly reduce the number of civilizations that are older and, apparently, smarter than ours. Regardless of how we look at it, the Earth is probably at the level of a primitive space culture. There are many thousands of civilizations that are more years ahead of us than it takes light to cover the distance separating us.

Riddle 2. Has the Earth been visited by alien beings who have been observing us using flying saucers?

Most scientists will immediately smile skeptically when they hear about flying saucers.

According to authoritative experts, in most cases, flying saucers are just a figment of the imagination. This especially applies to the so-called contact unidentified flying objects (UFOs), which are allegedly launched from Mars, Venus or other planets and regularly land at their bases. Some of them were declared to be interstellar spaceships, sparking lively discussions about the exotic experiences of their crews.

But one cannot completely ignore the opinions of those who believe that UFOs, even if they did not land on Earth, appeared in our skies. Since Arnold's first report in 1947, special search teams have recorded over 20,000 sightings of flying saucers - strange formations of unusual shapes or white-hot objects flying through the air at enormous speeds. A number of credible experts - pilots, radar operators and even some scientists - claimed that they had observed such phenomena more than once.

The main thing that the entire campaign to test the reality of UFOs has shown is that for more than 15 years not a single convincing proof of their existence has been presented. UFO believers claim that some photographs of fragments of "exploded saucers", a strange ash trail behind a suspicious object and other indirect evidence confirm the existence of alien messengers. But none of this “evidence” is acceptable either to the author of the book or to the scientific community as a whole.

Adherents of “flying saucers” allow themselves to arbitrarily interpret one fact or another - and always in their favor. If someone suddenly announced that the Earth was hollow, flying saucer proponents would be among those who would demand proof. They would reject the interpretation of seismic recordings as the disappearance of sound waves in a giant cavity at a depth of, say, 800 km. They would ask why hundreds of experienced seismologists have not obtained such results, and they would be absolutely right not to accept this wild theory, based on flimsy evidence provided by a tiny group of fanatics defending their model of a hollow Earth. However, the supporters of “flying saucers” themselves seem to be unable to understand the depravity of their position, self-confidently putting forward frivolous and biased arguments.

If one fine day a flying saucer lands and the whole world sees with its own eyes that an astronaut from another planet has emerged from it, then scientists - and along with them the author - will admit their mistake.

Since the development of orbital flight technology will lead to flights to the Moon and the emergence of manned space stations, our astronauts will eventually be able to answer the question of whether they are alone in space. Overly fanatical supporters of “flying saucers”, who are demanding today that suspicious objects be identified as space guests, must be patient, but for now their demands are completely groundless. If the aliens had some kind of a specific goal, say, the conquest of the Earth, then, having extremely developed technology, including “flying saucers,” they would have accomplished it long ago.

Another argument: pilots deliberately choose to observe us from afar, because they fear that their landing will cause panic among the inhabitants of the Earth and, possibly, the threat of space war. This is an attempt to explain the important fact that none of the saucer ships ever landed on Earth and its crew did not come into direct contact with us, the inhabitants of the Earth.

Of course, we can assume that aliens from other worlds visited Earth in the past. Suffice it to remember that in 10 billion years many civilizations could achieve extraordinary high level development of space technology to accept the possibility of multiple visits to the Earth, separated by intervals of a million years. Such visits do not seem at all fantastic now that man himself is ready to visit the Moon and other planets and is already dreaming of flights to the stars.

So, logic almost inexorably tells us that thousands of civilizations are now taking part in the exploration of the Galaxy and, perhaps, the traffic lights regulating this amazing “cosmic movement” are controlled from a single center.

Riddle 3. Is there a Space Organization of United Civilizations?

Fantasy? But why, if there are at least a million inhabited planets in the Galaxy? If most civilizations have surpassed us in their development and have long since sent interstellar ships in all directions, sooner or later they were bound to meet each other. Perhaps real “wars of the worlds” took place and empires arose, the spoils of which were individual planets. And all the other dark deeds committed by man on Earth can be repeated on a cosmic scale.

Probably, a system of space law would be developed and a galactic assembly would be formed, including both representatives of advanced civilizations and underdeveloped newcomers. Its sessions can adopt resolutions aimed at preserving peace and reducing the gap in the level of development of civilizations separated by many light years.

The Organization of United Civilizations would have begun millions of years ago. And when the delegates of our solar system arrive at the “crowded” assembly and look around in amazement at the alien diplomats, Earth will be one of the last members to have just achieved galactic status and emerge from the ranks of the underdeveloped planets.

The most prominent scientists on Earth do not see anything unscientific in this idea, and Hoyle speaks quite seriously about an “interstellar club” to which humanity will one day be invited.

The unification of the efforts of various civilizations to solve galactic problems and develop technology (which probably began even before the appearance of the first microorganism on Earth) would undoubtedly lead to a systematic search for backward civilizations that are not yet inaccessible to interstellar flights. If there are no intelligent creatures on the discovered planet yet or their culture is still too primitive to solve real cosmic problems, such a planet cannot be considered a candidate member of the community. The Earth would turn out to be such a planet.

But there is no certainty that civilizations that are highly developed in the field of space technology, but have not yet reached social maturity, would not try to conquer other planets. It is quite possible that some of our oldest and most enduring legends owe their appearance to the invasion of space aliens.

For example, the death of the legendary Atlantis in the ocean was a ruthless act that the space conquistadors committed after plundering it (gold, diamonds, uranium or even iron - a rare and therefore priceless metal on their planet), hiding the traces of their crime from the vigilant patrols of the “humane” group of civilizations .

Riddle 4. Was the Tunguska meteorite a spaceship with a crew?

In June 1908, a giant meteorite fell on the territory of Eastern Siberia, the sound of which was heard within a radius of 300 km. Unlike the Arizona and Chubb meteorites, it did not form a crater, but a powerful air wave knocked down trees within a radius of 80 km, as if the meteorite exploded in the air before hitting the surface. But several expeditions to the area of ​​the fall, organized by the USSR Academy of Sciences, did not find large fragments of a giant meteorite that should have fallen to Earth.

Two theories have been put forward, each of which considers the exploded object to be artificial, namely a ship from another world.

The first theory is that it was a fusion-powered spacecraft that exploded while trying to land. This would explain the enormous power of the blast wave; but the level of radioactivity in the area of ​​the fall is too low, which is not consistent with this theory. Energy from the explosion of a nuclear engine of a spacecraft, equivalent to at least a thousand hydrogen bombs, it would be enough for the explosion area to turn into a nuclear desert for hundreds of years. But at present this area of ​​the taiga is covered with lush vegetation.

Another assumption is that the ship arrived from the anti-world. Over the past decade, nuclear physicists have theoretically predicted an antiparticle for every known elementary particle, and many of them have already been obtained experimentally. A negatively charged electron corresponds to a positively charged antielectron, or positron, a proton - an antiproton, a neutron - an antineutron, and so on for more than thirty particles.

When any particle meets its antiparticle, they disappear, annihilate, and the entire mass turns into radiation with the release of energy, in thousand times greater than in reactions of fission or fusion of atomic nuclei.

Antiparticles are unusual only in the world of normal particles, and in the antiworld both of them change roles. But since antiparticles were first discovered as part of cosmic rays that rain down from interstellar space, a reasonable question is: why shouldn’t there be entire stars and even galaxies consisting of antimatter?

As long as galaxies and “anti-galaxies” are separated by huge distances, they can exist without causing the death of each other. However, it is possible that the radiation of colliding galaxies (for example, in the constellation Cygnus) owes its enormous power to the catastrophic processes of annihilation of stars and “antistars”.

Now it is easy to see what a terrible drama could play out over the surface of the Earth. Having spent on the way long years, perhaps all their lives, having covered the distance from one star to another, the unknown astronauts, making sure that the Earth was habitable, eagerly prepared for landing. But when immersed in dense layers of the earth’s atmosphere (at an altitude of about 80 km) the antimatter of their ship reacted with atmospheric gases - and the stellar journey ended with a monstrous flash.

This super-explosion did not scatter the atoms “to the wind.” They annihilated, and in doing so, energy was released that was many times greater than the energy of a thermonuclear explosion. The grave of the astronauts is marked only by completely fallen forest, and there are no traces of the aliens themselves or their ship.

This theory perfectly explains the mystery of the Tunguska meteorite and, if true, offers us an example of one of the rare visits from space.

Still, these are just guesses; So far no one can give us an answer to the question of whether the Earth was visited by guests from Space.

Riddle 5. Will a spaceship from Earth become a mysterious “flying saucer” for the inhabitants of another planet?

The closest planetary system to us is the star Proxima Centauri, at least 7,500 times further than Pluto, at a distance of 42 trillion km. (Of course, Proxima Centauri may not have planets at all, and if it does, they may be uninhabited.) It is difficult to imagine the enormous distances that separate the Sun and the nearest stars.

In a sphere with a radius of 12 light years (113 trillion km) there are 18 stars visible to the naked eye, including two well-known stars - Sirius and Procyon. Obviously, to visit any of these stars interplanetary the ships are unusable. Even if the rocket reaches a speed of 1600 km/sec and will cross the orbit of Pluto 40 hours from the moment of launch, to reach Proxima Centauri it will need 3000 years. Consequently, much faster interstellar ships. But even increasing the speed by 10 times will reduce the travel time to only 300 years. For interstellar travel to become possible, the rocket's speed must approach the speed of light. Spaceship flying at the speed of light (300,000 km/sec), would reach Pluto in just five hours, and its nearest neighbor star Proxima Centauri in 38,000 hours or 4.3 years. Chemically fueled rockets are not suitable because to reach speeds even a fraction of the speed of light, fuel tanks the size of asteroids are needed. Rockets with nuclear and so-called electrostatic ion engines could develop greater, but again insufficient speed.

Only completely new types of engines will provide us with real interstellar ships. Among them may be a photon rocket.

Just as in an electrostatic rocket engine the source of thrust is the flow of ions high speed, the photon engine emits a powerful beam of light quanta, providing reactive force. True, some rocketry experts believe that these projects are unrealistic, because a photon generator of incredible size and power would be required.

In recent years, there has been rapid development lasers. These devices generate unusually powerful beams of radiation (visible, ultraviolet or infrared). Every day we hear and read reports about new exploits of lasers: they burn holes in diamonds in a split second, cut plates of steel. Engineers have no doubt that they will eventually be able to concentrate millions of watts of power into a laser beam.

The spacecraft, equipped with a laser photon engine, is capable of reaching speeds equal to 90% of the speed of light. Then the journey to Proxima Centauri will take less than five years, and to Sirius (a distance of 8.6 light years) - about nine years. If astronauts voluntarily agreed to spend their lives aboard a spacecraft, it would be possible to visit all the stars within a radius of 25 light years in the hope of finding another planetary system and one of the millions of Earth "doubles" inhabited by intelligent beings.

But will this help?..

Riddle 6. What is the probability of finding life in the “nearest” neighborhood of the Sun accessible to a photon rocket?

From all that has been said above, it follows that this probability is practically zero. If Struve’s estimate is correct and the number of Earth-like planets in our Galaxy is indeed one million, then this means that on average, out of 200,000 stars, only one was lucky enough to have a family of planets. Unfortunately, as follows from Horner's calculations (Heidelberg Observatory), a sphere with a radius of 160 light years contains only 10 stars with planetary systems. This means that only with fantastic luck there is a star “close” to us - maybe even Proxima Centauri - with an inhabited planet.

If we increase Struve's estimate by 100 times, then our cosmonauts will have to examine 2000 stars before finding one with a habitable planet. Moreover, their journey will last at least 100 years - longer than their lifespan. So, due to the significant duration of the flights, it would seem impossible to successfully cope with the task of searching for fraternal worlds. Obviously, the astronauts will not have enough life to travel even a tenth of the way to such distant stars, much less visit them and return to Earth.

However, one circumstance pushes back this time barrier.

Riddle 7. Will astronauts be able to travel a distance of 1000 light years in one year?

If a spacecraft could reach a speed equal to, say, 99% of the speed of light or greater, the famous "time dilation" paradox of Einstein's theory of relativity would eliminate the time barrier. Theoretically, for a person moving with a rocket at that speed, time would literally slow down.

While the clock on Earth will tick 1000 years, for the ship's crew it will be 10 years, or even less, depending on how close its speed is to the speed of light. Therefore, upon reaching the planet, they will become only a few years older. Returning at the same speed, they will arrive on Earth a little older, but will not find their relatives and friends, who have long since died.

Riddle 8. Will man be able to visit other worlds on superluminal ships?

From the theory of relativity it follows that if the speed of an object approaches the speed of light (which is assumed to be constant), its mass tends to infinity, so that it is physically impossible for the object to continue accelerating to a higher speed.

But if the speed of light ceased to act as a limiting factor for our spacecraft, then solar system would become a pond, the Milky Way a lake, intergalactic space a sea, and the entire Universe an ocean. A sufficiently high speed will reduce the duration of travel from centuries to several months and years.

However, overcoming cosmic distances is a monstrously difficult task. Even a light year is not a large enough unit when dealing with distant objects. All the stars visible in the night sky are within 100,000 light years of our Galaxy. But the nearest galaxy in the constellation Andromeda is 2,300,000 light years away from us, and other millions and millions of galaxies are billions of light years away. Astronomers are uncomfortable using this unit, and they introduced a new one - parsec.

The word "parsec" is formed from the initial syllables of two words - parallax and second. Parallax is the magnitude of the angular displacement of the image of a star relative to the stellar background when observed from diametrically opposite points of the earth's orbit, the distance between which is 300 million. km. If the parallax (apparent displacement) is 1 arcsecond, then the distance to the observed object is 1 parsec. One parsec corresponds to 3.26 light years, or 31 trillion km. As you can see, a parsec is not much larger than a light year, so astronomers often use units derived from parsec - kiloparsec (1000 parsecs) and megaparsecs (1,000,000 parsecs). The Andromeda nebula is 700 kiloparsecs away from us, and the group of galaxies in the constellation Coma Berenices is 25 megaparsecs away (almost 90,000,000 light years).

With the help of radio telescopes and the 5-meter Palomar reflector, the boundaries of the observable Universe were expanded to 7.5 billion light years, that is, up to 2300 megaparsecs. Thus, the megaparsec as a unit of distance also becomes unusable, and some astronomers go one step further and define the size of the visible part of the Universe as magnitude 2.3 gigaparsec(console giga means billion).

The speed that would be required to fly to the farthest of famous galaxies, is expressed as a fantastic number; the distance is obtained by multiplying 7.5 billion light years by the path that light travels in a year (10 trillion km), and amounts to 75 10 21 km. Moving a million times faster than light, the spacecraft would only reach such distant objects in 750 years.

Obviously, even the removal of all relativistic restrictions will not make such flights a pleasant walk. Big Universe and even superluminal ships will only allow us to explore our own relatively small Galaxy and hardly objects beyond its borders.

This is, to some extent, an answer to those who, contemplating the myriad of worlds possibly inhabited, will ask, like Teller: “Where are you?” Only natives of our Galaxy could visit us on high-speed rockets, and even then they would have to work hard to find one surrounded by planets among every 200,000 stars. It logically follows that any planet, including Earth, will not be visited too often during the entire 10 billion years of life.