How to fly to the star Alpha Centauri at almost the speed of light

The spacecraft is really interesting. Instead of the usual rocket powered by chemical reactions and big enough to transport people or heavy equipment, the star projectile, Starshot, is a cloud of tiny multipurpose chips called StarChips, each of which is connected to "light sail". The sail will be so light that when a laser beam from a "light beamer" hits it, it will accelerate it to a speed of 20% of the speed of light. It will take 30,000 years for the fastest rocket to reach Alpha Centauri, which is 4.37 light years away from us, while it will take only 20 years for a star chip. When they arrive, the chips will not stop but will pass within a few minutes across the surface of the star and across the planets it may have, and will transmit images that will take 4.37 years to return to Earth.

The "stupid" part is that apparently the purpose of Starshot is not scientific. What astronomers want to know about stars can't be learned in such a quick flyby, and it's unknown if Alpha Centauri has any planets at all, so the mission doesn't even promise close-ups of other worlds. "We gave much less thought to the scientific aspect," admits the astrophysicist Ed Turner from Princeton University, member of Starshot's advisory board. "It was almost a given for us that from a scientific point of view it would be interesting." But in August 2016, the project team got lucky: an association of European astronomers Find, nothing to do with Starshot, a planet around the nearest star to our Sun, Proxima Centauri, which is a tenth of a light year closer to us than Alpha Centauri. Starshot suddenly became the only semi-practical way for the foreseeable future to visit the holiday planet around another star. Still, this project sounds a bit like the dreams of those science fiction and interstellar travel enthusiasts who talk seriously and constantly about sending humans beyond our solar system using technologies that will surely work, if they can find enough funding and technological miracles.

But Starshot doesn't need miracles. His technology, which does not yet exist, is based on proven engineering and does not violate any physical law. And the project is well funded. The entrepreneur behind the project is Yuri Milner, the financier also Groundbreaking initiatives others, too annual award For breakthrough scientists, all united under the name Breakthrough. Milner kickstarts Starshot's initial development with $100 million. What's more, Milner has recruited an advisory board impressive enough to convince skeptics that StarShot can do the job, including world experts in lasers, sails, chips, outer planets, aeronautics and major project management, including two Nobel laureates, Britain's Astronomer State, important theoretical astrophysicists , a selection of wise and experienced engineers, and Dyson, who, although he thinks Starshot is stupid, says that the idea of ​​a laser-powered sail makes sense and should be tried. All in all, in the long run, few would bet against that much money, that much good advice, and that many smart engineers.

However, this project is different from any previous space mission. "Everything about Starshot is unconventional," she says Joan Johnson-Fries, a space policy expert from the US Naval Academy. Its goals, mode of financing and management structure go beyond any other player in the space travel arena. Commercial space companies are focused on profits and unmanned missions within the solar system. NASA, which is also not planning a trip to other planets, is too cautious for such an uncertain venture; Many of its bureaucratic procedures are cumbersome and unnecessary and the tasks it performs depend on approvals and funding inconsistent of Congress. "NASA needs time." Billionaires can just do.” says Leroy ChowAstronaut and former commander of The International Space Station. "You build this team, and take off."

the action plan

The man driving the Starshot project has always been fascinated by distances. Yuri Milner was born in Moscow in 1961, the same year Yuri Gagarin was the first person to stay in space. "My parents told me something by calling me Yuri," he says, meaning he was supposed to go to places no one had ever been. Milner therefore studied physics, "which was my first love," he says. He studied physics for 10 years and researched Quantum chromodynamics. "Unfortunately, I wasn't very successful," he says. Then he went into business, was one of the first investors in Facebook and Twitter, and accumulated a fortune that, according to reports, is approaching 3 billion dollars. "Then about four years ago," says Milner, "I started thinking about my first love again."

In 2013, he established his prize fund, which gives a prize in each of the fields: life sciences, mathematics and physics. And in 2015 he started to engage in a "hobby", as he put it, The series of groundbreaking initiatives, like an outstretched hand to the universe: a million dollar prize for the compilation the message The most successful to present it to extraterrestrial civilizations, a prize of 100 million dollars toComprehensive search, more precisely after extraterrestrial intelligence, and now 100 million dollars toStarshot.

At the beginning of 2015, Milner assembled the core management staff from people he encountered at the various Breakthrough conventions. The chairman of the advisory committee for Starshot is My father is live, an American-Israeli physicist who serves as the head of the Department of Astronomy at Harvard University, and its actual director is Pete Worden, who directed NASA's Ames Research Institute and was involved in the program of NASA and the American Defense Advanced Research Projects Agency (DARPA) to launch a spaceship within 100 years. Worden attached the Pete Klopper, an engineer who works for episodes in the space industry who worked with him at the Ames Institute, as chief engineer. They brought in experts in the relevant technologies, who are apparently willing to participate for a little money or volunteer, including celebrities such as Facebook's Mark Zuckerberg and cosmologist Stephen Hawking. Starshot's management policy seems to be a sort of balance between NASA's strict decision-making hierarchy and the Silicon Valley culture where you put a bunch of smart people in a room, present them with a long-term goal, and let them work. one member of the committee, James Benford, company presidentMicrowave Sciences, says the task is: "Give us next week, and some date in five years, and we will already find a way to connect them."
The members of the formed team They began by agreeing that there was nothing to talk about sending humans to Alpha Centauri, because it was too far-fetched, and planned to focus on an unmanned mission, which, they estimate, could be launched in about 20 years. They also agreed that the big problem is the propulsion of the spacecraft. In the middle of 2015, doctoral students and post-doctoral students in Leib's laboratory began to classify the various ideas: impossible, improbable and feasible. In December 2015, they received an article by Philip Lubin, a physicist from the University of California at Santa Barbara called "A blueprint for interstellar flight". The drive Lubin proposed was an array of lasers Show controlled: a large number of small lasers grouped together so that their light is coherently integrated into a single beam. The laser beam will push a chip attached to the sail, which will have to move at high speed to reach another planet within a few decades. (A similar idea was published 30 years earlier by the physicist and science fiction writer Robert Forward. He called it "Stardust.) Although this technology was still more science fiction than fact, "basically, I gave the blueprint for Starshot," Lubin said, joining the project.

In January 2016, Milner, Worden, Klopfer, Leib and Lubin met at Milner's home in Silicon Valley and formulated a strategy. "Yuri came in with a page with sticky notes on it," says Lubin, "and started asking the right scientific and economic questions." The beauty of the project's unconventional approach was that instead of going through a lengthy process of requesting proposals and reviewing them, as NASA would have done, or instead of worrying about possible profits as in a commercial company, the Starshot team was free to formulate a basic plan solely according to what was best in their eyes.

The only component that is really expensive in Starshot is the laser, the sails and chips will be cheap and expendable. Bundles of them will be mounted on a launcher and launched beyond the atmosphere where they will be released like schools of flying fish, bundle after bundle, hundreds and maybe thousands of chips - so many that, similar to the reproductive system of the reptiles, if they lose a few of them along the way it will not be terrible. Each of them will receive a boost from the laser that will accelerate it within a few minutes to a speed of 20% of the speed of light. Then the laser will turn off, and the chip with the sail will just fly. When they reach the star, the chips will call home. "Ten years ago we wouldn't have been able to talk about it seriously," says Milner. But now, when lasers and chips are perfected at an exponential rate, and when scientists invent and produce new materials, "it's no longer hundreds of years away, but decades away."

Starshot management circulated the idea among scientists and asked them to look for critical failures in it. No one found any fault. "I can tell you why it's hard and why it's expensive," Lubin says, "but I can't tell you why it can't be done." In April 2016, the team had already decided on a system, and on April 12, Milner called a press conference at the head The Freedom Tower New in New York. The party featured videos and animations and was attended by several members of the advisory committee. He announced an "interstellar sail" that would sail on a wind of light. The following summer, the researchers determined what the next step should be.

Star chips and light sails

The team soon discovered that despite the technical feasibility, the implementation of the plan would be challenging. Even the lighter technology, the star-chip, piles up many difficulties. The chip has to be tiny, on the order of one gram, but it has to collect and transmit data, carry its own energy source, and survive the long journey. A few years ago the engineer son Mason Peck and the members of his research group at Cornell University components they called "sprites", which are chips similar to smart phone chips that carry a light sensor, solar panels and a radio, and weigh four grams per chip. The Starshot chips will be modeled after the elves, but will be even lighter, about one gram, and each chip will carry four cameras. Instead of focusing using heavy lenses, the engineers consider placing Bypass lattice A tiny called a planar Fourier array for capture (PFCA), across the light sensors. The grating will split the light into wavelengths that will then be able to be reproduced in a computerized manner to any desired depth of focus. The engineers are also thinking of equipping the chips with a spectrograph, to identify the chemical composition of the planets' atmosphere, and a magnetometer to measure the star's magnetic field.

The chips would also have to transmit their photographs across interstellar distance. Today's satellites useLaser diode With a power of one watt to transmit information, but such a laser works for smaller distances. So far, Peck says, the most distant transmission has been from the nearest moon 100 million times farther than Alpha Centauri. To transmit to Earth from this planet, the laser's direction has to be incredibly precise. And, in the four years it will take for the signal to arrive, it will disperse and weaken until when it gets here only a few hundred photons will be left. One possible solution is to send the images through a chain of relays, from one chip to the next and so on. Restoring the information to Earth, says a member of the Starshot Advisory Committee Zach ManchesterFrom Harvard, "it's still a difficult problem."

The chips will also need batteries to operate the cameras and computers installed in them to transmit data during their 20-year journey. Considering the distance from Alpha Centauri or Proxima Centauri and the few watts that can be produced by a small chip, it is expected that the signal that will reach Earth will be weak, but "with a number of photons just enough to be received by Starshot's receiver," says Peck. For now there is no energy source that can work both in the dark and in the cold and weighs less than a gram and produces sufficient energy. "Energy is the most difficult problem with the chip," says Peck. One possible solution, he suggests, would be to adapt the tiny nuclear batteries used in medical implants to the task. Another solution is to use the energy produced by the sail when it passes through the interstellar medium full of gas and dust and heated by friction.

This interstellar medium could also endanger the Starshot chip. The medium is similar to highly diluted cigarette smoke, he explains Bruce Drain, an astronomer from Princeton University who is also a member of the committee. The exact density of the medium is not known, nor is the size of the dust grains, so it is difficult to estimate its destructive potential. A collision at a speed close to the speed of light between the chips and between grains of any size can cause a variety of damage, from small dents to complete destruction. If the size of the chip is a square centimeter, Draine says, "it's expected to collide with a lot of things like that along the way." One of the possible ways to protect the chips from relatively small particles is alloy coatings Copper-beryllium A few millimeters thick, although even then dust particles could cause terrible damage. "The chip will survive, or it won't survive," says Peck, but with a little luck, among the hundreds of thousands of chips in the swarm, some will last.

The second technology in the order of problems is the sail. The chips will be driven by the recoil of the light reflected from their sails, similar to how the recoil of a tennis ball pushes the racket. The more light that is reflected, the stronger the thrust and the faster the cruise. To reach 20% of the speed of light, the light sail of the space chip has to return 99.999% of the light that hits it. "Any light that is not reflected ends up heating the sail," he says Jeffrey Landis, a scientist from the Glenn Research Institute of NASA and a member of the advisory committee. And considering the enormous temperatures of the light launcher, "even if a small part of the laser energy heats the sail the results will be devastating." Compared to solar sails that exist today, which have powered several experimental spacecraft around the solar system with the power of sunlight, it should also be much lighter, a few atoms thick or "the thickness of a soap bubble," says Landis. In 2000, in an experiment that came closest to this, Benford used a beam of microwaves to accelerate a sail made of carbon sheet. In the experiment, an acceleration of 13 G was recorded (an acceleration 13 times greater than the acceleration of free fall on Earth), while the Starshot sail will have to withstand an acceleration that can reach 60,000 G. And the sail, like the star-chip, will have to deal with the dust in the interstellar medium that will try to pierce it. There is still no material that is light, strong, reflective and heat resistant that does not cost millions of dollars. "One of the miracles we will have to invent is the material from which the sails will be made," Klopfer says.

There are still decisions to be made regarding the sails. The sail can connect to the chip with cables, or the chip will be mounted on the sail. The sail will be able to rotate, to keep centered in relation to the light launcher. After the initial acceleration, the sail may be able to fold like an umbrella, so that it is less exposed to the hazards of the journey. Then, when it reaches Alpha Centauri it will unfold again and fold back to the extent necessary to serve as a telescope mirror or antenna to send the signal from the chip to Earth. "It sounds like a lot of work," says Landis, "but we've already solved tough problems."

Still, all these difficulties are easier than the difficulties involved in the light launcher that will push the sails. Only by using an extremely powerful laser, of 100 gigawatts, will Starshot chips be able to gain a speed that is a significant percentage of the speed of light. The US Department of Defense has built more powerful laser devices, says Robert Peterkin, chief engineer bBoard of Directors of the Directed Energy Laboratory in the US Air Force research labs, but they only shine to the billionth or trillionth of a second. Starshot's light launcher would have to illuminate each sail for minutes. To produce such power for such a period of time, it is possible to group small fiber lasers into an array and direct their shows so that all the light from them joins a coherent beam. The Ministry of Defense has also built such show-controlled laser arrays, but the arrays it built have 21 lasers and are only 30 centimeters in diameter, Peterkin says, a configuration that produces several tens of kilowatts. Starshot's light launcher will need an array of 100 million devices of this type, with a power of several kilowatts, and a size of a square kilometer. "How far is this from the peak of today's refinement?" asks Peterkin.

"And things are getting more and more complicated," he says. The light rays of the 100 million small lasers will be deflected by the natural vortices in the atmosphere, each in a different way. In the end, the launcher will have to focus all of them into a four square meter sail hovering at an altitude of 60,000 kilometers. "As of now," he says dryly Robert Fugate, a retired scientist and member of the committee, "Controlling a show of 100 million lasers through atmospheric vortices on a target a few meters away at 60 megameters keeps me busy." The light may miss the sail entirely, or, more likely, hit it unevenly, so that parts of the sail will receive a stronger push, and it will crumple, spin, or drop from the beam.

Here too the people of Starshot have a possible solution, but it also involves its own problems. adaptive optics It is a technology that has already been used in large telescopes and it eliminates the distortions created by atmospheric vortices with the help of a flexible mirror that generates an opposite and equal distortion. But they will have to make major changes to it to suit the needs of Starshot. In the light launcher, instead of an adjustable mirror, the scientists will have to aim with masterful precision each laser fiber to correct the atmospheric distortion. The adaptive optics in today's telescopes can correct an area 30 milliseconds in diameter (that is, an arc second, a measure of the size of sky areas) at the very least. Starshot will have to aim the launcher at an angle of 0.3 milliseconds, and they haven't done that yet.

Even if all these different and challenging technologies can be realized, they will have to work together in a single system, which surely presents Starshot executives with a combination with parts that are evolving or parts that do not yet exist. Worden calls this process "the art of the long-term plan of hard research." The systems "do not yet have a single content," he says Kevin Parkin a notebook Parkin Research, systems engineer and committee member. The plan, in the first five years, Klopfer says, is to "collect the technologies", that is, under the guidance of the committee's experts in the various fields, the staff members will conduct small-scale experiments and build computational models. They started in the winter of 2015-2016 by reviewing existing technologies and publishing requests for proposals for technologies that have not yet been developed. In the spring of 2017, they intend to award small contracts, from a few hundred thousand to 1.5 million dollars. The next step could be building prototypes. If successful, construction of the laser and sail could begin in the early 30s, and launch would be in the mid-40s of this century.

By then, the cumulative cost of StarShot will surely reach billions of dollars, and with any luck, the project will recruit collaborators among governments, laboratories and space agencies in the US, Europe and Asia. "I will argue my case, hoping that more people will join," says Milner. "It has to be global," he adds, mentioning the logical considerations of national security regarding a giant laser facility. "If you start something like this in secret, a lot of question marks will arise. It is important to state the intentions openly."

On to the stars

In the face of all these setbacks, what are the chances of success? Technology experts not affiliated with Starshot estimate that the chances are small. Several people told me unequivocally that "they will not make it to Alpha Centauri." David Charbonneau from the Harvard-Smithsonian Center for Astrophysics says that the project will be so expensive in the end that "it may be worth persuading the people of the United States to allocate 5% of the national budget to it, the same share of the budget that the Apollo program collected."

Those associated with Starshot believe that the odds are better, but they are practical. "We can certainly use a laser to launch a spacecraft to Alpha Centauri," he says Greg Matloff from the New York College of Technology, a member of the committee. "Will we be able to get them there in the next 20 years? I do not know." Manchester from Harvard says that "in 50 years the chances are not bad, and in a hundred years they are 100%." Worden thinks their approach is deliberately measured, "and maybe in five years we'll find we can't do it." Milner believes that his role in Starshot, apart from the funding, is to ensure that the project remains practical and anchored in reality. "If it takes more than one generation," he says, "then we shouldn't be working on this project."

Until the end of August 2016, I thought Dyson was right: Starshot's technology is interesting, but Alpha Centauri is bullshit. It is a binary system (Alpha Centauri A and Alpha Centauri B) whose two stars are similar to our sun, and there is no uniqueness in either. The knowledge and understanding that astronomers have about such stars, says Sharbonno, "is quite good," and although a comparison between their eruptions and magnetic fields and those of the Sun can be useful, "what the journey there will teach us about the physics of stars does not justify the investment."

Now that astronomers know that Alpha Centauri's neighbor has a planet, the scientific justification is more compelling. This star, Proxima Centauri, is a little closer to Earth and is a red dwarf, the most common type of star. The distance of the planet, Proxima Centauri b, from Proxima Centauri corresponds to the possibility of life. When the discovery was announced, the Starshot team celebrated the announcement with a dinner. Will the members consider changing the goal of the project? "Certainly," says Milner. "We have a lot of time to decide." The setup of the laser array will be flexible enough "to adjust to the difference, which is about two degrees," says Fugate.

Ultimately the overall goal of the Breakthrough Initiatives is to find all the planets closest to our solar system, Klopfer says, and Proxima Centauri b may be the first of many. "I feel like an entomologist who turns over a stone, finds an insect under it, and thinks that he will find an insect under every stone he turns over now," he says. "It's not true, but there is something encouraging about it."

Of course, even the existence of Proxima Centauri b does not guarantee the scientific value of Starshot. The chip will be able to take pictures, maybe examine the planet's magnetic field, maybe even sample its atmosphere. But he will do all this on the fly, in minutes. Considering the time to prepare for the launch and the final cost, says the astrophysicist from Princeton David Spergel, "You can build an optical telescope with a diameter of 12 to 15 meters in space, observe the planet for months, and collect much more information than you can collect in a flight."

But the billionaires are free to invest in what they want, and more forgiving souls are free to join them in that desire. Moreover, many of those who doubt the scientific value of Starshot support it anyway because in the development of the technology, the project engineers will surely come across interesting things. "They won't solve all the problems, but they will solve some," says Spergel. And a creative solution to even one of the difficult problems "will be a tremendous success." Also, even if StarShot fails, missions that will benefit from the technological fruits it will yield will be able to reach several important targets both in our solar system and beyond.

Milner's own fondness for the project stems from his hope that the project will capture the humans of the world in the sense that they are one species on one planet. "In the last six years, I spent 50% of my time traveling, a lot of time in Asia and Europe," he says. "I realized that a global consensus is difficult to achieve, but not impossible." This line aligns with the other Breakthrough initiatives, which are mainly focused on finding extraterrestrials with whom to communicate, and aligns with Milner's considerable investment in the Internet and social media, which have changed the nature of discourse and community. But in the end, even he admits that the desire to reach another planet is inexplicable. "If you keep asking me why, I'll end up saying I don't know. I just think it's important."

Almost everyone I asked responded similarly: they can't explain it to someone who doesn't understand it anyway. They just want to travel. James Gan, professor emeritus in the department of astrophysical sciences at Princeton, although he believes that the chances of Starshot succeeding are slim and he doubts its scientific justification, nevertheless he says: "I see logic in most things, but I am not so logical about the desire of man. Since childhood I have dreamed of traveling to the stars." Many members of the advisory committee said the same thing. "It's just so cool," says Landis, echoing the words of other members of the committee.

The contradictions inherent in these dreams are best described by Freeman Dyson. Starshot's chip and laser-driven sail make sense, and the people driving the project are intelligent and "fairly sensible". But he thinks that the attempt to reach Alpha or Proxima Centauri should be abandoned and concentrated on the study of the solar system, where it will be possible to fly the space chips at a lower speed and with the help of weaker lasers that are easier to build. "Investigation is one of the things we are designed for," he says. "We excel at it." He thinks that it is "automatic machines" that should explore the universe and that there is no scientific justification for sending people. Then, as befits the unpredictable Dyson, he adds: "On the other hand, I'd still really like to travel."