Ivan Korznikov: The realities of interstellar flights. Interstellar flights: what they will be like Interstellar flights are impossible
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 intelligent life exists. 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 consoling to our pride. The Earth cannot be among the civilizations of high or even medium 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, their average age is 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 old (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 a 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 fire nuclear 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 evidence 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 in not accepting 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 a specific goal, say, the conquest of the Earth, then, having extremely advanced technology, including “flying saucers,” they would have realized it long ago.
Another argument is that 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. It is enough to remember that in 10 billion years many civilizations could have reached an unusually high level of development of space technology in order to agree with 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 ago 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 felled 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. The energy from the explosion of a spaceship's nuclear engine, equivalent to at least a thousand hydrogen bombs, would be enough to turn the area of the explosion 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 many years on the road, perhaps their entire lives, covering the distance from one star to another, the unknown astronauts, convinced that the Earth was inhabited, 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 small 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 an electrostatic rocket engine produces thrust from a stream of high-velocity ions, a photonic engine emits a powerful beam of light quanta to provide propulsion. True, some rocketry experts believe that these projects are unrealistic, because a photon generator of incredible size and power would be required.
IN last years are rapidly developing 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, 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 spaceships, then the solar system would become a pond, the Milky Way would become a lake, intergalactic space would become a sea, and the entire Universe would become 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 travel to the most distant known galaxies is 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 eliminating all relativistic restrictions will not make have a nice walk such flights in the Big Universe and even superluminal ships will allow us to explore only 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.
Using existing technology, it would take a very, very long time to send scientists and astronauts on an interstellar mission. The journey will be painfully long (even by cosmic standards). If we want to accomplish such a journey in at least one lifetime, or even a generation, we need more radical (read: purely theoretical) measures. And while wormholes and subspace engines are absolutely fantastic at the moment, there have been other ideas for many years that we believe in being realized.
Nuclear propulsion
Nuclear propulsion is a theoretically possible "engine" for rapid space travel. The concept was originally proposed by Stanislaw Ulam in 1946, a Polish-American mathematician who took part in the Manhattan Project, and preliminary calculations were made by F. Reines and Ulam in 1947. Project Orion was launched in 1958 and lasted until 1963.
Led by Ted Taylor of General Atomics and physicist Freeman Dyson of the Institute for Advanced Study at Princeton, Orion would harness the power of pulsed pulses. nuclear explosions to provide enormous thrust with very high specific impulse.
In a nutshell, Project Orion involves a large spacecraft that gains speed by supporting thermonuclear warheads, ejecting bombs from behind and accelerating from a blast wave that goes into a rear-mounted “pusher,” a propulsion panel. After each push, the force of the explosion is absorbed by this panel and converted into forward movement.
Although this design is hardly elegant by modern standards, the advantage of the concept is that it provides high specific thrust - that is, it extracts the maximum amount of energy from the fuel source (in in this case nuclear bombs) at minimal cost. Additionally, this concept can theoretically achieve very high speeds, some estimate up to 5% of the speed of light (5.4 x 107 km/h).
Of course, this project has inevitable disadvantages. On the one hand, a ship of this size will be extremely expensive to build. Dyson estimated in 1968 that the Orion spacecraft, powered by hydrogen bombs, would have weighed between 400,000 and 4,000,000 metric tons. And at least three-quarters of that weight would come from nuclear bombs, each weighing about one ton.
Dyson's conservative calculations showed that the total cost of building Orion would be $367 billion. Adjusted for inflation, this amount comes out to $2.5 trillion, which is quite a lot. Even with the most conservative estimates, the device will be extremely expensive to produce.
There's also the small issue of the radiation it will emit, not to mention the nuclear waste. It is believed that this is why the project was scrapped as part of the partial test ban treaty of 1963, when world governments sought to limit nuclear testing and stop the excessive release of radioactive fallout into the planet's atmosphere.
Fusion rockets
Another possibility of using nuclear energy is through thermonuclear reactions to produce thrust. In this concept, energy would be created by igniting pellets of a mixture of deuterium and helium-3 in a reaction chamber by inertial confinement using electron beams (similar to what is done at the National Ignition Facility in California). So thermo nuclear reactor would explode 250 pellets per second, creating a high-energy plasma that would then be redirected into the nozzle, creating thrust.
Like a rocket that relies on a nuclear reactor, this concept has advantages in terms of fuel efficiency and specific impulse. The speed is estimated to reach 10,600 km/h, far exceeding the speed limits of conventional rockets. Moreover, this technology has been extensively studied over the past few decades and many proposals have been made.
For example, between 1973 and 1978, the British Interplanetary Society conducted a study into the feasibility of Project Daedalus. Drawing on modern knowledge and fusion technology, scientists have called for the construction of a two-stage unmanned scientific probe that could reach Barnard's Star (5.9 light-years from Earth) within a human lifetime.
The first stage, the largest of the two, would operate for 2.05 years and accelerate the craft to 7.1% the speed of light. Then this stage is discarded, the second one is ignited, and the device accelerates to 12% of the speed of light in 1.8 years. Then the second stage engine is turned off, and the ship flies for 46 years.
Project Daedalus estimates that the mission would have taken 50 years to reach Barnard's Star. If to Proxima Centauri, the same ship will get there in 36 years. But, of course, the project includes a lot of unresolved issues, in particular those that cannot be resolved using modern technologies - and most of them have not yet been resolved.
For example, there is practically no helium-3 on Earth, which means it will have to be mined elsewhere (most likely on the Moon). Second, the reaction that drives the apparatus requires that the energy emitted significantly exceeds the energy expended to start the reaction. And although experiments on Earth have already surpassed the “break-even point,” we are still far from the volumes of energy that can power an interstellar spacecraft.
Thirdly, the question of the cost of such a vessel remains. Even by the modest standards of the Project Daedalus unmanned vehicle, a fully equipped vehicle would weigh 60,000 tons. To give you an idea, the gross weight of NASA SLS is just over 30 metric tons, and the launch alone will cost $5 billion (2013 estimates).
In short, not only would a fusion rocket be too expensive to build, but it would also require a level of fusion reactor far beyond our capabilities. Icarus Interstellar, an international organization of citizen scientists (some of whom worked for NASA or ESA), is trying to revive the concept with Project Icarus. Formed in 2009, the group hopes to make the fusion movement (and more) possible for the foreseeable future.
Fusion ramjet
Also known as the Bussard ramjet, the engine was first proposed by physicist Robert Bussard in 1960. At its core, it is an improvement on the standard fusion rocket, which uses magnetic fields to compress hydrogen fuel to the fusion point. But in the case of a ramjet, a huge electromagnetic funnel sucks hydrogen from the interstellar medium and dumps it into the reactor as fuel.
As the vehicle gains speed, the reactive mass enters a confining magnetic field, which compresses it until thermonuclear fusion begins. The magnetic field then directs energy into the rocket nozzle, accelerating the craft. Since no fuel tanks will slow it down, a fusion ramjet can reach speeds on the order of 4% of light speed and travel anywhere in the galaxy.
However, this mission has a lot to offer possible disadvantages. For example, the problem of friction. The spacecraft relies on a high rate of fuel collection, but will also encounter large amounts of interstellar hydrogen and lose speed - especially in dense regions of the galaxy. Secondly, there is little deuterium and tritium (which are used in reactors on Earth) in space, and the synthesis of ordinary hydrogen, which is abundant in space, is not yet within our control.
However, science fiction fell in love with this concept. The most famous example is perhaps the Star Trek franchise, which uses Bussard collectors. In reality, our understanding of fusion reactors is not nearly as good as we would like.
Laser sail
Solar sails have long been considered an effective way to conquer the solar system. Besides the fact that they are relatively simple and cheap to manufacture, they have a big advantage: they do not require fuel. Instead of using rockets that need fuel, the sail uses radiation pressure from stars to propel ultra-thin mirrors to high speeds.
However, in the case of interstellar travel, such a sail would have to be propelled by focused beams of energy (laser or microwaves) to accelerate it to near light speed. The concept was first proposed by Robert Forward in 1984, a physicist at Hughes Aircraft Laboratory.
His idea retains the advantages of a solar sail in that it does not require fuel on board, and also that laser energy does not dissipate over a distance in the same way as solar radiation. Thus, although the laser sail will take some time to accelerate to near light speed, it will subsequently be limited only by the speed of light itself.
According to a 2000 study by Robert Frisby, director of advanced propulsion concepts research at NASA's Jet Propulsion Laboratory, a laser sail would accelerate to half the speed of light in less than a decade. He also calculated that a sail with a diameter of 320 kilometers could reach Proxima Centauri in 12 years. Meanwhile, the sail, 965 kilometers in diameter, will arrive in just 9 years.
However, such a sail will have to be built from advanced composite materials to avoid melting. Which will be especially difficult given the size of the sail. Costs are even worse. According to Frisby, the lasers would require a steady flow of 17,000 terawatts of energy, which is roughly what the entire world consumes in one day.
Antimatter engine
Science fiction fans are well aware of what antimatter is. But in case you forgot, antimatter is a substance made up of particles that have the same mass as regular particles but the opposite charge. An antimatter engine is a hypothetical engine that relies on interactions between matter and antimatter to generate energy, or thrust.
In short, an antimatter engine uses hydrogen and antihydrogen particles colliding with each other. The energy emitted during the annihilation process is comparable in volume to the energy of the explosion of a thermonuclear bomb accompanied by a flow of subatomic particles - pions and muons. These particles, which travel at one-third the speed of light, are redirected into a magnetic nozzle and generate thrust.
The advantage of this class of rocket is that most of the mass of the matter/antimatter mixture can be converted into energy, resulting in a high energy density and specific impulse superior to any other rocket. Moreover, the annihilation reaction can accelerate the rocket to half the speed of light.
This class of rockets will be the fastest and most energy efficient possible (or impossible, but proposed). While conventional chemical rockets require tons of fuel to propel a spacecraft to its destination, an antimatter engine will do the same job with just a few milligrams of fuel. The mutual destruction of half a kilogram of hydrogen and antihydrogen particles releases more energy than a 10-megaton hydrogen bomb.
It is for this reason that NASA's Advanced Concepts Institute is researching this technology as a possibility for future missions to Mars. Unfortunately, when considering missions to nearby star systems, the amount of fuel required grows exponentially and the costs become astronomical (no pun intended).
According to a report prepared for the 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, a two-stage antimatter rocket would require more than 815,000 metric tons of propellant to reach Proxima Centauri in 40 years. It's relatively fast. But the price...
Although one gram of antimatter produces an incredible amount of energy, producing just one gram would require 25 million billion kilowatt-hours of energy and cost a trillion dollars. Currently, the total amount of antimatter that has been created by humans is less than 20 nanograms.
And even if we could produce antimatter cheaply, we would need a massive ship that could hold the required amount of fuel. According to a report by Dr. Darrell Smith and Jonathan Webby of Embry-Riddle Aeronautical University in Arizona, an antimatter-powered interstellar spacecraft could reach the speed of 0.5 times the speed of light and reach Proxima Centauri in just over 8 years. However, the ship itself would weigh 400 tons and require 170 tons of antimatter fuel.
A possible way around this would be to create a vessel that would create antimatter and then use it as fuel. This concept, known as the Vacuum to Antimatter Rocket Interstellar Explorer System (VARIES), was proposed by Richard Aubauzi of Icarus Interstellar. Based on the idea of in-situ recycling, the VARIES vehicle would use large lasers (powered by huge solar panels) to create antimatter particles when fired into empty space.
Similar to the fusion ramjet concept, this proposal solves the problem of transporting fuel by extracting it directly from space. But again, the cost of such a ship will be extremely high if we build it using our modern methods. We simply cannot create antimatter on a huge scale. There is also a radiation problem to be solved, since the annihilation of matter and antimatter produces bursts of high-energy gamma rays.
They not only pose a danger to the crew, but also to the engine so that they don't fall apart into subatomic particles under the influence of all that radiation. In short, an antimatter engine is completely impractical given our current technology.
Alcubierre Warp Drive
Science fiction fans are no doubt familiar with the concept of warp drive (or Alcubierre drive). Proposed by Mexican physicist Miguel Alcubierre in 1994, the idea was an attempt to imagine instantaneous movement through space without violating Einstein's theory of special relativity. In short, this concept involves stretching the fabric of spacetime into a wave, which would theoretically cause the space in front of an object to contract and the space behind it to expand.
An object inside this wave (our ship) will be able to ride this wave, being in a “warp bubble,” at a speed much higher than the relativistic one.
Since the ship does not move in the bubble itself, but is carried by it, the laws of relativity and space-time will not be violated. Essentially, this method does not involve moving faster than the speed of light in a local sense.
It is "faster than light" only in the sense that the ship can reach its destination faster than a beam of light traveling outside the warp bubble. Assuming the spacecraft is equipped with the Alcubierre system, it will reach Proxima Centauri in less than 4 years. Therefore, when it comes to theoretical interstellar space travel, this is by far the most promising technology in terms of speed.
Of course, this whole concept is extremely controversial. Among the arguments against, for example, is that it does not take quantum mechanics into account and can be refuted by a theory of everything (like loop quantum gravity). Calculations of the required amount of energy also showed that the warp drive would be prohibitively voracious. Other uncertainties include the safety of such a system, spacetime effects at the destination, and violations of causality.
In 2013, the Jet Propulsion Laboratory published the results of warp field tests conducted in vacuum conditions. Unfortunately, the results were considered “inconclusive.” In the long term, we may find that the Alcubierre metric violates one or more fundamental laws of nature. And even if its physics prove correct, there is no guarantee that the Alcubierre system can be used for flight.
In general, everything is as usual: you were born too early to travel to the nearest star. However, if humanity feels the need to build an “interstellar ark” that will accommodate a self-sustaining human society, it will be possible to reach Proxima Centauri in about a hundred years. If, of course, we want to invest in such an event.
In terms of time, all available methods seem to be extremely limited. And while spending hundreds of thousands of years traveling to the nearest star may be of little interest to us when our own survival is at stake, as space technology advances, the methods will remain extremely impractical. By the time our ark reaches the nearest star, its technology will become obsolete, and humanity itself may no longer exist.
So unless we make a major breakthrough in fusion, antimatter, or laser technology, we will be content with exploring our own solar system.
The solar system has long been of no particular interest to science fiction writers. But, surprisingly, for some scientists our “native” planets do not cause much inspiration, although they have not yet been practically explored.
Having barely opened a window into space, humanity is rushing into unknown distances, and not only in dreams, as before.
Sergei Korolev also promised to soon fly into space “on a trade union ticket,” but this phrase is already half a century old, and a space odyssey is still the lot of the elite - too expensive a pleasure. However, two years ago HACA launched a grandiose project 100 Year Starship, which involves the gradual and multi-year creation of a scientific and technical foundation for space flights.
This unprecedented program is expected to attract scientists, engineers and enthusiasts from around the world. If everything is successful, in 100 years humanity will be able to build an interstellar ship, and we will move around the solar system like on trams.
So what problems need to be solved for star flight to become a reality?
TIME AND SPEED ARE RELATIVE
Astronomy by automatic spacecraft seems to some scientists to be an almost solved problem, oddly enough. And this despite the fact that there is absolutely no point in launching machine guns to the stars with the current snail’s speed (about 17 km/s) and other primitive (for such unknown roads) equipment.
Now the American spacecraft Pioneer 10 and Voyager 1 have left the solar system, and there is no longer any connection with them. Pioneer 10 is moving towards the star Aldebaran. If nothing happens to it, it will reach the vicinity of this star... in 2 million years. In the same way, other devices crawl across the expanses of the Universe.
So, regardless of whether a ship is inhabited or not, to fly to the stars it needs high speed, close to the speed of light. However, this will help solve the problem of flying only to the closest stars.
“Even if we managed to build a starship that could fly at a speed close to the speed of light,” wrote K. Feoktistov, “the time of travel only in our Galaxy would be calculated in millennia and tens of millennia, since its diameter is about 100,000 light years years. But on Earth, much more will happen during this time.”
According to the theory of relativity, the passage of time in two systems moving relative to each other is different. Since over long distances the ship will have time to reach a speed very close to the speed of light, the time difference on Earth and on the ship will be especially great.
It is assumed that the first target of interstellar flights will be Alpha Centauri (a system of three stars) - the closest to us. At the speed of light, you can get there in 4.5 years; on Earth, ten years will pass during this time. But the greater the distance, the greater the time difference.
Remember the famous “Andromeda Nebula” by Ivan Efremov? There, flight is measured in years, and in terrestrial years. A beautiful fairy tale, nothing to say. However, this coveted nebula (more precisely, the Andromeda Galaxy) is located at a distance of 2.5 million light years from us.
According to some calculations, the journey will take the astronauts more than 60 years (according to starship clocks), but a whole era will pass on Earth. How will their distant descendants greet the space “Neanderthals”? And will the Earth even be alive? That is, returning is basically pointless. However, like the flight itself: we must remember that we see the Andromeda nebula galaxy as it was 2.5 million years ago - that’s how long its light travels to us. What is the point of flying to an unknown goal, which, perhaps, has not existed for a long time, at least in the same form and in the same place?
This means that even flights at the speed of light are justified only to relatively close stars. However, devices flying at the speed of light still live only in theory, which resembles science fiction, albeit scientific.
A SHIP THE SIZE OF A PLANET
Naturally, first of all, scientists came up with the idea of using the most effective thermonuclear reaction in the ship’s engine - as it had already been partially mastered (for military purposes). However, for round-trip travel at close to light speed, even with an ideal system design, a ratio of initial to final mass of at least 10 to the thirtieth power is required. That is, the spaceship will look like a huge train with fuel the size of a small planet. It is impossible to launch such a colossus into space from Earth. And it’s also possible to assemble it in orbit; it’s not for nothing that scientists don’t discuss this option.
The idea of a photon engine using the principle of matter annihilation is very popular.
Annihilation is the transformation of a particle and an antiparticle upon their collision into some other particles different from the original ones. The most studied is the annihilation of an electron and a positron, which generates photons, the energy of which will move the starship. Calculations by American physicists Ronan Keene and Wei-ming Zhang show that, based on modern technologies, it is possible to create an annihilation engine capable of accelerating a spacecraft to 70% of the speed of light.
However, further problems begin. Unfortunately, using antimatter as rocket fuel is very difficult. During annihilation, bursts of powerful gamma radiation occur, harmful to astronauts. In addition, contact of positron fuel with the ship is fraught with a fatal explosion. Finally, there are not yet technologies for obtaining a sufficient amount of antimatter and its long-term storage: for example, the antihydrogen atom “lives” now for less than 20 minutes, and the production of a milligram of positrons costs 25 million dollars.
But let's assume that over time these problems can be resolved. However, you will still need a lot of fuel, and the starting mass of the photon starship will be comparable to the mass of the Moon (according to Konstantin Feoktistov).
THE SAIL IS TORN!
The most popular and realistic starship today is considered to be a solar sailboat, the idea of which belongs to the Soviet scientist Friedrich Zander.
A solar (light, photon) sail is a device that uses the pressure of sunlight or a laser on a mirror surface to propel a spacecraft.
In 1985, American physicist Robert Forward proposed the design of an interstellar probe accelerated by microwave energy. The project envisaged that the probe would reach the nearest stars in 21 years.
At the XXXVI International Astronomical Congress, a project for a laser starship was proposed, the movement of which is provided by the energy of optical lasers located in orbit around Mercury. According to calculations, the path of a starship of this design to the star Epsilon Eridani (10.8 light years) and back would take 51 years.
“It is unlikely that the data obtained from travel through our solar system will make significant progress in understanding the world in which we live. Naturally, the thought turns to the stars. After all, it was previously understood that flights near the Earth, flights to other planets of our solar system were not the ultimate goal. To pave the way to the stars seemed to be the main task.”These words belong not to a science fiction writer, but to spaceship designer and cosmonaut Konstantin Feoktistov. According to the scientist, nothing particularly new will be discovered in the solar system. And this despite the fact that man has so far only reached the Moon...
However, outside the solar system, the pressure of sunlight will approach zero. Therefore, there is a project to accelerate a solar sailboat using laser systems from some asteroid.
All this is still theory, but the first steps are already being taken.
In 1993, a 20-meter-wide solar sail was deployed for the first time on the Russian ship Progress M-15 as part of the Znamya-2 project. When docking the Progress with the Mir station, its crew installed a reflector deployment unit on board the Progress. As a result, the reflector created a bright spot 5 km wide, which passed through Europe to Russia at a speed of 8 km/s. The spot of light had a luminosity roughly equivalent to the full Moon.
So, the advantage of a solar sailboat is the lack of fuel on board, the disadvantages are the vulnerability of the sail structure: essentially, it is a thin foil stretched over a frame. Where is the guarantee that the sail will not receive holes from cosmic particles along the way?
The sail version may be suitable for launching automatic probes, stations and cargo ships, but is not suitable for manned return flights. There are other starship projects, but they are, one way or another, reminiscent of the above (with the same large-scale problems).
SURPRISES IN INTERSTELLAR SPACE
It seems that many surprises await travelers in the Universe. For example, barely reaching beyond the solar system, the American apparatus Pioneer 10 began to experience a force of unknown origin, causing weak braking. Many assumptions have been made, including the as yet unknown effects of inertia or even time. There is still no clear explanation for this phenomenon; a variety of hypotheses are being considered: from simple technical ones (for example, reactive force from a gas leak in an apparatus) to the introduction of new physical laws.
Another device, Voyadger 1, detected an area with a strong magnetic field on the border of the Solar system. In it, the pressure of charged particles from interstellar space causes the field created by the Sun to become denser. The device also registered:
- an increase in the number of high-energy electrons (about 100 times) that penetrate into the Solar System from interstellar space;
- a sharp increase in the level of galactic cosmic rays - high-energy charged particles of interstellar origin.
The space between the stars is not empty. There are remnants of gas, dust, and particles everywhere. When attempting to travel close to the speed of light, each atom that collides with the ship will be like a high-energy cosmic ray particle. The level of hard radiation during such a bombardment will increase unacceptably even during flights to nearby stars.
And the mechanical impact of particles at such speeds will be like explosive bullets. According to some calculations, every centimeter of the starship's protective screen will be continuously fired at at a rate of 12 rounds per minute. It is clear that no screen will withstand such exposure over several years of flight. Or it will have to have an unacceptable thickness (tens and hundreds of meters) and mass (hundreds of thousands of tons).
Actually, then the spacecraft will consist mainly of this screen and fuel, which will require several million tons. Due to these circumstances, flying at such speeds is impossible, especially since along the way you can run into not only dust, but also something larger, or get trapped in an unknown gravitational field. And then death is again inevitable. Thus, even if it is possible to accelerate the spaceship to sublight speed, it will not reach its final goal - there will be too many obstacles on its way. Therefore, interstellar flights can only be carried out at significantly lower speeds. But then the time factor makes these flights meaningless.
It turns out that it is impossible to solve the problem of transporting material bodies over galactic distances at speeds close to the speed of light. There is no point in breaking through space and time using a mechanical structure.
MOLE HOLE
Science fiction writers, trying to overcome inexorable time, invented how to “gnaw holes” in space (and time) and “fold” it. They came up with various hyperspace jumps from one point in space to another, bypassing intermediate areas. Now scientists have joined the science fiction writers.
Physicists began to look for extreme states of matter and exotic loopholes in the Universe where it is possible to move at superluminal speeds, contrary to Einstein's theory of relativity.
This is how the idea of a wormhole came about. This hole brings together two parts of the Universe, like a cut tunnel connecting two cities separated high mountain. Unfortunately, wormholes are only possible in an absolute vacuum. In our Universe, these holes are extremely unstable: they can simply collapse before the spacecraft gets there.
However, to create stable wormholes you can use the effect discovered by the Dutchman Hendrik Casimir. It consists in the mutual attraction of conducting uncharged bodies under the influence of quantum oscillations in a vacuum. It turns out that the vacuum is not completely empty, there are fluctuations in the gravitational field in which particles and microscopic wormholes spontaneously appear and disappear.
All that remains is to discover one of the holes and stretch it, placing it between two superconducting balls. One mouth of the wormhole will remain on Earth, the other will be moved by the spacecraft at near-light speed to the star - the final object. That is, the spaceship will, as it were, break through a tunnel. Once the starship reaches its destination, the wormhole will open for real lightning-fast interstellar travel, the duration of which will be measured in minutes.
BUBBLE OF DISRUPTION
Akin to the wormhole theory is a warp bubble. In 1994, Mexican physicist Miguel Alcubierre performed calculations according to Einstein's equations and found the theoretical possibility of wave deformation of the spatial continuum. In this case, space will compress in front of the spacecraft and simultaneously expand behind it. The starship is, as it were, placed in a bubble of curvature, capable of moving at unlimited speed. The genius of the idea is that the spacecraft rests in a bubble of curvature, and the laws of relativity are not violated. At the same time, the curvature bubble itself moves, locally distorting space-time.
Despite the inability to travel faster than light, there is nothing to prevent space from moving or spacetime warping spreading faster than light, which is what is believed to have happened immediately after the Big Bang when the Universe formed.
All these ideas do not yet fit into the framework of modern science, however, in 2012, NASA representatives announced the preparation of an experimental test of Dr. Alcubierre’s theory. Who knows, maybe Einstein’s theory of relativity will one day become part of a new global theory. After all, the process of learning is endless. This means that one day we will be able to break through the thorns to the stars.
Irina GROMOVA
The last thing experts discuss these days is interstellar travel on spaceships. And the point here is not that this topic has set teeth on edge, since it has been discussed in detail for centuries (though these details were from the realm of science fiction). The point is also not that the need for interstellar flights has disappeared and we will communicate with extraterrestrial civilizations only with the help of various signals. No signals can replace travel to other worlds. "Better to see once than hear a hundred times". Signals will not give us either material, tangible objects, or real representatives of fauna and flora. Using signals, we will not be able to establish contact with civilizations that are not yet technologically ready for it. We can point out other aspects of universal life that will be left behind if we cannot master space transport. So why is this problem not now being considered by specialists in a practical way? The answer to this question is very simple: we are not yet ready for such flights. This “for now” may continue for hundreds of years, although it is very easy to make mistakes when predicting the development of science and technology for the future.
Despite such an unfavorable state of affairs with interstellar travel, it makes sense to familiarize yourself with the problem itself. If we don’t want to be on the road for millions of years (and this is absurd), then we need to ensure a higher speed of the ship. Speed exceeding the speed of light is impossible, the speed of light for a ship is also unrealistic. Therefore, with different estimates, they operate with a speed that is 10% of the speed of light. It is called decilight. Centilight speed is one hundred times less than the speed of light.
The issue of the passage of time during space travel has been widely discussed. Time slows down significantly. Thus, the core of the Galaxy, which is located at a distance of about 30 thousand light years from us, can be reached in 21 years, and even the nearest galaxy - the Andromeda nebula - in 28 years. At the beginning of the flight, the spacecraft must accelerate for some time and slow down accordingly before landing. Each of these periods of time can be several years. The passage of time on the abandoned planet, naturally, does not slow down. Therefore, during the journey of earthlings to the Andromeda nebula and back, more than 3 million years will pass on Earth. Although this is very reminiscent of science fiction, this is precisely the number that follows from A. Einstein’s theory of relativity, that is, it is a strictly scientific result.
It is very easy to estimate what a rocket must be (its capabilities) in order for it to reach decilight or centilight speed. The speed of the rocket V, which it reaches after burning out fuel of mass M, depends both on the mass of the rocket M and on the ejection speed of the working substance of the rocket W. This dependence is expressed by the formula
We cannot increase the mass of fuel without increasing the mass of the rocket, because the fuel has to be loaded onto the same rocket. True, the rocket can also be refueled on the way, in space, but we will take this possibility into account later.
It is absolutely clear that the lighter the rocket, the easier it is to accelerate it to high speed. The need to load a large mass of fuel onto a rocket does not allow it to be made as light as desired. There is only one way out - to look for a fuel that would be very effective in terms of generating energy. Naturally, we can only talk about thermonuclear fuel. We don’t yet know of a more efficient fuel, although it certainly exists. A person is forced to proceed from what he currently has. Thus, in the last century, the project of traveling to the Moon using a steam engine was very seriously discussed. But let's get back to the rockets. It turned out that even the use of uranium as fuel can only allow the rocket to reach 1,300 km/s. By earthly standards this is a very high speed, but it is 23 times less than the speed of light. The use of thermonuclear fuel (when nuclei are not fissioned, but synthesized) will allow this speed to be increased somewhat. But it will still not be possible to reach decilight speed.
To show how technologically complex this task is, let us give an example. For every gram of mass there must be a power of 3 million watts. In this case, the acceleration of the rocket will be equal to the magnitude of the earth's acceleration. Let's compare this value with what is actually available. Thus, a submarine weighing 800 tons, using a nuclear engine, develops a power of 15 million watts. We need this power to be developed by an engine weighing 5 grams. This should include all the components of a moving rocket (not just the engine).
Photon rockets, which were written about not only by science fiction writers, but also by scientists, clearly cannot cope with the task of interstellar flights.
Not long ago, a new solution to the problem of creating propulsion for interstellar travel was proposed. It is proposed not to load fuel onto the rocket at home, on Earth, but to take it as needed directly in space. Such fuel can be hydrogen, which is contained in interstellar space. Hydrogen nuclei can be forced to enter into thermonuclear reactions and thus develop the necessary power without overloading the rocket with a large supply of fuel. In this case, no reserve is needed at all. The rocket sucks in interstellar hydrogen from the surrounding space, uses it, and throws out the spent working substance. Everything in this project would be great, but there is one “but”: the density of interstellar hydrogen is very low, there is only about one hydrogen atom in each cubic centimeter. This is the deepest vacuum that we will never achieve on Earth in the most ingenious vacuum pumps! In order to collect the required amount of hydrogen, it is necessary to filter huge volumes around the rocket. Calculations show that in order to provide itself with fuel, the rocket must capture hydrogen from the surrounding area at a distance of up to 700 kilometers! How technically this can be done is unclear. What kind of blades must be attached to the rocket so that it can scoop up hydrogen from all this space? In addition, we must keep in mind that the density of interstellar hydrogen can be thousands of times less. Whereas? There are ideas on this matter as well. One of them is that neutral hydrogen must be converted into electrically charged particles (ions), and they can be sucked into the rocket using electric fields. But that's just an idea. How to implement all this in practice is completely unclear.
Thus, in principle, it is possible to create interstellar ships (no laws of nature prevent this), but in practice we are not yet ready to do this.
It is more realistic in our time to create an automatic space station with the task of reaching the planets of other stars closest to us. Such a project was presented at the Tallinn Symposium by M.Ya. Marov and U.N. Zakirov. Previously conducted by U.N. Zakirov's calculations show that it is possible to launch a container with scientific equipment to one of the nearest stars. This should take approximately 40–50 years. The project involves the creation of a five-stage rocket. In this case, the first two stages are designed to operate in the first phase while the rocket accelerates to a speed of 40% of the speed of light. Two more stages are also designed to brake the rocket as it approaches the target. It must be borne in mind that at such high speeds " braking distances"The rocket is very big. The braking time of the rocket, just like the time of its acceleration, will be one to two years! The fifth stage of the rocket is planned to be used at the last stage of the flight to maneuver and ensure landing of the automatic station.
Fundamentally new and very interesting is the proposal of the authors of the project not to take all the fuel on board the station at once, but after using the first stage of the rocket to refuel it in space. At first glance, this may seem strange - after all, for this we will have to send a special tanker after the rocket (or rather, simultaneously with it). What benefits are possible from this? But it turns out it is possible. It turns out that if you do not refuel in space, you will have to increase the initial mass of the rocket system almost tenfold! So, despite the costs associated with the creation of a special “refueler”, the game is worth the candle. In this case, the whole system becomes quite real. Thus, the mass of the container with equipment (payload) will be approximately 450 kilograms; The mass of the rocket system will be approximately 3000 tons, which is quite realistic, since such rockets have already been mastered during the implementation of the lunar exploration program. The breakdown of mass into five stages is provided as follows: 2780, 293, 44, 8 and 3 tons.
Implementation of the developed project is not easy and expensive. Another option is possible: use spent tritium. But the technical side of the matter is again completely unclear and, undoubtedly, not easy.
What should such a probe do in space? The equipment installed on it should make it possible to study the interstellar medium, the location of the planets and the physical conditions from them. The probe should make it possible to detect signals from extraterrestrial civilizations, analyze them, communicate with subscribers, etc. That is, do everything that automatic probes in space should do, or, in other words, the probe should engage in “all major types of space science " These words belong to probe researcher Bracewell.
Could interstellar travel turn from a pipe dream into a real possibility?
Scientists around the world say that humanity is moving further and further in space exploration, and new discoveries and technologies are appearing. However, people can still only dream about interstellar flights. But is this dream so unattainable and unrealistic? What does humanity have today and what are the prospects for the future?
According to experts, if progress does not stagnate, then within one or two centuries, humanity will be able to fulfill its dream. The ultra-powerful Kepler telescope at one time allowed astronomers to discover 54 exoplanets where the development of life is possible, and today the existence of 1028 such planets has already been confirmed. These planets, orbiting a star outside the solar system, are so far from the central star that liquid water can be maintained on their surface.
However, to get an answer to main question— whether humanity is alone in the Universe is not yet possible due to the gigantic distances to the nearest planetary systems. The multitude of exoplanets at a distance of a hundred or less light years from Earth, as well as the enormous scientific interest they generate, force us to look at the idea of interstellar travel in a completely different way.
Flight to other planets will depend on the development of new technologies and the choice of method necessary to achieve such a distant goal. In the meantime, the choice has not yet been made.
In order for earthlings to be able to overcome incredibly vast cosmic distances, and in a relatively short period of time, engineers and cosmologists will have to create a fundamentally new engine. It’s too early to talk about intergalactic flights, but humanity could explore the Milky Way, the galaxy in which the Earth and the Solar system are located.
The Milky Way Galaxy has about 200–400 billion stars, around which planets move in their orbits. The closest star to the Sun is Alpha Centauri. The distance to it is approximately forty trillion kilometers or 4.3 light years.
A rocket with a conventional engine will have to fly to it for about 40 thousand years! Using Tsiolkovsky's formula, it is easy to calculate that in order to accelerate a spacecraft with a jet engine on rocket fuel to a speed of 10% of the speed of light, more fuel is needed than is available on the entire Earth. Therefore, talking about a space mission with modern technologies is complete absurdity.
According to scientists, future spaceships will be able to fly using a thermonuclear rocket engine. The thermonuclear fusion reaction can produce energy per unit mass on average almost a million times more than the chemical combustion process.
That is why, in the 1970s, a group of engineers together with scientists developed a project for a giant interstellar ship with thermonuclear propulsion. propulsion system. The unmanned spacecraft Daedalus was supposed to be equipped with a pulsed thermonuclear engine. Small granules were to be thrown into the combustion chamber and ignited by beams of powerful electron beams. Plasma, as a product of a thermonuclear reaction, escaping from the engine nozzle, provides traction to the ship.
It was assumed that Daedalus was supposed to fly to Barnard's star, the path to which is six light years away. A huge spaceship would reach it in 50 years. And although the project was not implemented, to this day there is no more realistic technical project.
Another direction in the technology of creating interstellar ships is the solar sail. The use of a solar sail is considered today as the most promising and realistic option for a starship. The advantage of a solar sailboat is that there is no need for fuel on board, which means that the payload will be much greater than that of other spacecraft. Already today it is possible to build an interstellar probe, where solar wind pressure will be the main source of energy for the ship.
The seriousness of intentions to develop interplanetary flights is evidenced by the project, which has been developed since 2010 in one of the main scientific laboratories of NASA. Scientists are working on a project to prepare for a manned flight to other star systems within the next hundred years.
