In this illustration by Pat Rawlings for NASA, you can see the climber in the foreground and the tether stretching back down toward distant Earth. (illustration credit ill.19)
EVENTUALLY WE’LL HAVE to move beyond patrolling our planetary backyard and start laying the foundations for a true interplanetary civilization. Asteroid defense and geoengineering will only take us so far. We need to scatter to outposts and cities on new worlds so that we’re not entirely dependent on Earth for our survival—especially when life here is so precarious. Just one impact of 10 on the Torino scale could destroy every human habitat here on our home planet. As horrific as that sounds, we can survive it as a species if we have thriving cities on Mars, in space habitats, and elsewhere when the Big One hits. Just as Jewish communities managed to ensure their legacy by fleeing to new homes when they were in danger, so, too, can all of humanity.
The problem is that we can’t just put our belongings into a cart and hightail it out of Rome, like my ancestors did when things got ugly in the first century CE. Currently, we don’t have a way for people to escape the gravity well of planet Earth on a regular basis. The only way to get to space right now is in a rocket, which takes an enormous amount of energy and money—especially if you want to send anything bigger than a mobile phone into orbit. Rockets are useless for the kind of off-world commuter solution we’ll need if we’re going to become an interplanetary civilization, let alone an interstellar one. That’s why an international team of scientists and investors is working on building a 100-kilometer-high space elevator that would use very little energy to pull travelers out of the gravity well and up to a spaceship dock. It sounds completely preposterous. How would such an elevator work?
That was the subject of a three-day conference I attended at Microsoft’s Redmond campus in the late summer of 2011, where scientists and enthusiasts gathered in a tree-shaded cluster of buildings to talk about plans to undertake one of humanity’s greatest engineering projects. Some say the project could get started within a decade, and NASA has offered prizes of up to $2 million to people who can come up with materials to make it happen.
The physicist and inventor Bryan Laubscher kicked off the conference by giving us a broad overview of the project, and where we are with current science. The working design that the group hopes to realize comes from a concept invented by a scientist named Bradley Edwards, who wrote a book about the feasibility of space elevators in the 1990s called The Space Elevator. His design calls for three basic components: A robotic “climber” or elevator car; a ground-based laser-beam power source for the climber; and an elevator cable, the “ribbon,” made of ultra-light, ultra-strong carbon nanotubes. Edwards’s design was inspired, in part, by Arthur C. Clarke’s description of a space elevator in his novel The Fountains of Paradise. When you’re trying to take engineering in a radical new direction that’s never been tried before, sometimes science fiction is your only guide.
A space elevator is a fairly simple concept, first conceived in the late nineteenth century by the Russian scientist Konstantin Tsiolkovsky. At that time, Tsiolkovsky imagined the elevator would look much like the Eiffel Tower, but stretching over 35,000 kilometers into space. At its top would be a “celestial castle” serving as a counterweight.
A century after Tsiolkovsky’s work, Bradley speculated that a space elevator would be made of an ultra-strong metal ribbon that stretched from a mobile base in the ocean at the equator to an “anchor” in geostationary orbit thousands of kilometers above the Earth. Robotic climbers would rush up the ribbons, pulling cars full of their cargo, human or otherwise. Like Tsiolkovsky’s celestial castle, the elevator’s anchor would be a counterweight and space station where people would stay as they waited for the next ship out. To show me what this contraption would look like from space, an enthusiast at the Space Elevator Conference attached a large Styrofoam ball to a smaller one with a string. Then he stuck the larger ball on a pencil. When I rolled the pencil between my hands, the “Earth” spun and the “counterweight” rotated around it, pulling the string taut between both balls. Essentially, the rotation of the Earth would keep the counterweight spinning outward, straining against the elevator’s tether, maintaining the whole structure’s shape.
Once this incredible structure was in place, the elevator would pull cargo out of our gravity well, rather than pushing it using combustion. This setup would save energy and be more sustainable than using rocket fuel. Getting rid of our dependence on rocket fuel will reduce carbon emissions from rocket flights, which today bring everything from satellites to astronauts into orbit. We’ll also see a reduction in water pollution from perchlorates, a substance used in making solid rocket fuel, and which the Environmental Protection Agency in the United States has identified as a dangerous toxin in our water supplies.
A space elevator would be a permanent road into space, making it possible for people to make one or more trips per day into orbit. Passengers could bring materials up with them so that we could start building ships and habitats in space. Once we started mining and manufacturing in space, elevators would be used to bring payloads back down, too. Most important, a working space elevator is many thousands of times cheaper than the one-time-use Soyuz rockets that bring supplies to the International Space Station, only to destroy themselves in Earth’s atmosphere. NASA reports that each Space Shuttle launch cost about $450 million. Much of that money was spent on storing enough fuel to complete the round-trip back to Earth. But groups working on space-elevator plans believe their system could reduce the cost of transporting a pound of cargo into space from today’s $10,000 price tag to as little as $100 per pound.
In this illustration by Pat Rawlings for NASA, you can see the climber in the foreground and the tether stretching back down toward distant Earth. (illustration credit ill.19)
The elevator would be attached to the Earth at the equator, where geostationary orbit happens, probably on a floating platform off the coast of Ecuador in international waters. This is a likely building site because it is currently an area of ocean that experiences very little rough weather, and therefore the elevator could climb out of our atmosphere with as little turbulence as possible. According to Edwards’s plan, the elevator ribbon would stretch 100,000 kilometers out into space (about a quarter of the distance to the Moon), held taut by a counterweight that could be anything from a captured asteroid to a space station. A ride up would take several days, and along the ribbon would be way stations where people could get off and transfer to orbiting space stations or to vessels that would carry them to the Moon and beyond.
The elevator car itself is the easiest thing for us to build today. It would be an enormous container, with atmospheric controls for human cargo, connected to large robotic arms that would pull the car up the ribbon hand over hand. We already have robotic arms that can scale ropes and lift incredibly heavy objects. This aspect of the space elevator is so widely understood that the Space Elevator Conference sponsored a “kids’ day” that included LEGO space-elevator-climber races. Robots designed by teens and kids competed to see which could climb “ribbons” attached to the ceiling and place a “satellite” at the top.
Of course it will take some effort to get from LEGO climbers to lifters big enough to haul components of a space hotel up through thousands of kilometers of atmosphere and space. But this is within the capabilities of our current industrial technology. So we’ve got our elevator car. But how will it be powered?
One of the many arguments in favor of the elevator concept is that it will be environmentally sustainable. The dominant theory among would-be space-elevator engineers at this point is that we’ll install lasers on the space-elevator platform, aimed at a dish on the elevator that will capture the beam and convert it to power. This technology is also within our reach. In 2009, NASA awarded $900,000 to LaserMotive for its successful demonstration of this so-called “wireless power transmission” for space elevators. In 2012, NASA offered a similar prize for a power-beaming lunar rover. The biggest problem with the power-beaming idea currently is that we are still looking at fairly low-power lasers, and as the space elevator ascended higher into the atmosphere the beam from such a laser would scatter and be blocked by clouds. It’s possible that only 30 percent of the beam would reach the dish once the elevator was in space.
Still, we have seen successful demonstrations of power beaming, and companies are working on refining the technology. We don’t quite have our perfect power beam yet, but it’s on the way.
At the Space Elevator Conference, participants devoted an entire day to technical discussions about how we’d build the most important part of the space elevator: its cable, often called the ribbon. Again, most theories about the ribbon come from Edwards’s plans for NASA in the 1990s. At that time, scientists were just beginning to experiment with new materials manufactured at the nanoscale, and one of the most promising of these materials was the carbon nanotube. Carbon nanotubes are tiny tubes made of carbon atoms that “grow” spontaneously under the right conditions in specialized chambers full of gas and chemical primers. These tubes, which look a lot like fluffy black cotton, can be woven together into ropes and textiles. One reason scientists believe this experimental material might make a good elevator cable is that carbon nanotubes are theoretically very strong, and can also sustain quite a bit of damage before ripping apart. Unfortunately, we haven’t yet reached the point where we can convert these nanoscopic tubes into a strong material.
Carbon nanotube material is so light and strong that the elevator cable itself would be thinner than paper. It would literally be a ribbon, possibly several meters across, that the robotic cars would grip all the way up into space. Every year at the Space Elevator Conference, people bring carbon nanotube fibers and compete to see which can withstand the greatest strain before breaking. Winners stand to gain over a million dollars from NASA in its Strong Tether Challenge. Sadly, the year I attended, nobody had fibers that were strong enough to place (but there’s always next year!).
Researchers from the University of Cincinnati and Rice University, where there are nanomaterials labs investigating the tensile strength of carbon nanotubes, explained that we are years away from having a working elevator ribbon made of carbon nanotubes. Though the microscopic tubes on their own are the strongest material we’ve ever discovered, we need to make them into a “macromaterial”—something that’s big enough to actually build with. And making that transition into a macromaterial can be difficult, as the University of Cincinnati chemical engineer Mark Haase explained:
I like to compare [carbon nanotube development] to the development of aluminum in the first half of the twentieth century. In the years prior to this, aluminum had been known, and it was available in small labs. It was rare and expensive, but there was interest in it because it had strange properties. It was very valuable because of this. As the twentieth century started to progress, we developed the infrastructure and the technology as well as an understanding of the material itself that allowed us to mass-produce aluminum. And that’s when we started to see it infiltrating modern life in airplanes, consumer goods, and more. Carbon nanotubes are at that early stage—it’s an interesting material but very difficult and expensive to make. However, I and some of my colleagues are working on making those breakthroughs so that, much like aluminum in the second half of the twentieth century, we can develop a material that will change the modern landscape.
Haase added that the barrier here is that we need to invent an entirely new material, and then figure out how to string it between the Earth and a counterweight without it breaking. That’s not a trivial problem, even once we reach the point where we can create a carbon nanotube ribbon. What if a huge storm hits while the elevator is climbing into the stratosphere? Or what if one of the millions of pieces of junk orbiting the Earth, from bits of wrecked satellites to cast-off chunks of rockets, slams into the elevator ribbon and rips it? This may be an enormous structure, but it will have some vulnerabilities and we need to determine how we’ll protect it.
How do you dodge an incoming piece of space junk that’s headed right to your elevator ribbon? Engineer Keith Lofstrom suggested mounting the ribbon on a massive maglev platform designed to move the line in any direction very rapidly, basically yanking it out of the way. Rice University materials-science researcher Vasilii Artyukhov argued that we might not want to use carbon nanotubes at all, because they break in several predictable ways, especially when they’re under constant strain and bombarded with cosmic rays from the sun. He thought an alternative material might be boron nitride nanotubes, though these are even more experimental than carbon nanotubes at this point.
Ultimately, the elevator cable is our stumbling block in terms of engineering. But there are also social and political issues we’ll have to confront as we begin our journey into space.
Building the elevator goes beyond engineering challenges. First, there’s the legal status of this structure. Who would it belong to? Would it be a kind of Panama Canal to space, where everybody pays a toll to the country who builds it first? Or would it be supervised by the U.N. space committees? Perhaps more urgently, there is the question of how any corporation or government could justify spending the money to build the elevator in the first place.
One of the world experts on funding space missions is Randii Wessen, an engineer and deputy manager of the Project Formulation Office at the Jet Propulsion Laboratory. An energetic man with a quick wit, Wessen has a lifetime of experience working on NASA planetary exploration missions, and now one of his great passions is speculating about economic models that would support space flight. We’ve recently witnessed the success of Elon Musk’s private company SpaceX, whose Falcon rocket now docks with the International Space Station, essentially taking on the role once played by the U.S. government–funded Space Shuttles. “The bottom line is that you need to find a business rationale for doing it,” Wessen told me. “What I would do is parallel the model that was used for the airplane.” He swiftly fills in a possible future for commercial spaceflight, by recalling how airplanes got their start:
The first thing that happens is the military wants one—they’ll fund it themselves. Next the U.S. government says this is critical to national security or economic competitiveness, so we need to make up a job for these guys to keep them in business. For airplanes, the government said, “We’ll have you deliver mail.” They didn’t need this service, but they gave it to airline companies to keep them going. This is analogous to spacecraft today. The government is saying [to companies like SpaceX], “We want you to resupply the space station.” That’s where we are now. As this gets more routine, these private companies are going to say, “If we put seats on this thing, we’ll make a killing.” They did it with airplanes. You can see that starting today, with four or five different companies who have suborbital and orbital launch capability.
Like many other people in the slowly maturing field of commercial spaceflight, Wessen is convinced that government contracts and tourism represent the first phase of an era when sending people to space is economically feasible. He noted that SpaceX’s founder, Musk, has said it’s reasonable to expect payload costs to go down to roughly $1,000 per kilogram. “Everything cracks open at that point,” Wessen declared. SpaceX isn’t the only private company fueling Wessen’s optimism. Robert Bigelow, who owns the Budget Suites hotel chain, has founded Bigelow Aerospace to design and deploy space hotels. In the mid-2000s, Bigelow successfully launched two test craft into orbit, and he is now working on more permanent orbiting habitats. Meanwhile, Moon Express, a company in Silicon Valley, is working closely with NASA and the U.S. government to create crafts that could go to the Moon. Its founders hope to have a working prototype before 2015.
Google is another Silicon Valley mainstay that is investing in the burgeoning space economy. The company recently announced its Google Lunar X Prize, which will award up to $30 million to a privately funded company that successfully lands a robot on the Moon. To win the prize, the robot must go at least 500 meters on the Moon’s soil, called regolith, while sending video and data back to Earth. Alex Hall, the senior director of the Google Lunar X Prize, described herself as “the Lunar Chamber of Commerce.” At SETICon, a Silicon Valley conference devoted to space travel, Hall told those of us in the audience that the Lunar X Prize is “trying to kick-start the Lunar Space Economy.” She said the group measures its success not just in robots that land on the Moon, but in creating incentives for entrepreneurs to set up space-travel companies in countries where no orbital launch facilities have existed before. Mining and energy companies are among the groups most interested in what comes out of the Google X Prize, she said. The X Prize “is the first step to buying a ticket to the Moon, and using the resources on the Moon as well as living there.” Bob Richards, a cofounder of Moon Express, is one of the contenders for the Google X Prize. He spoke on the same panel as Hall at SETICon, and amplified her arguments. “This isn’t about winning—it’s about creating a new industry,” he explained. “We believe in a long-term vision of opening up the Moon’s resources for the benefit of humanity, and we’re going to do it based on commercial principles.”
The space elevator is the next stage in the space economy. Once we have a relatively cheap way of getting into orbit, and a thriving commercial space industry partly located on the Moon, there will be a financial incentive to build a space elevator—or more than one. It may begin with funding from governments, or with a space-obsessed entrepreneur who decides to invest an enormous amount of money in a “long-term vision” of the kind Richards described. Already, we see the first stirrings of how such an arrangement might work, with a future Google or Budget Suites providing the initial capital required to move the counterweight into place, drop the ribbon from space down to the ocean, and get the beam-powered robotic climber going.
Once we’ve got a reliable and sustainable method of leaving the planet, we can begin our exodus from Earth in earnest. The space elevator, or another technology like it, could be the modern human equivalent of the well-trodden path that took humans out of Africa and into what became the Middle East, Asia, and Europe. It’s the first leg on our next long journey as we scatter throughout the solar system.