Space Elevators Are Totally Possible (If Someone Will Just Pay for It)
“This would of course all go a lot faster if we had, you know, money.”
A NASA space elevator concept. Image: NASA
"This would of course all go a lot faster if we had, you know, money."
That was the defining topic at this year's annual meeting of the International Space Elevator Consortium (ISEC) in Seattle last week, which saw scientists gather from around the world to plot the next step in humanity's march to space.
The quote came from longtime ISEC member Peter Robinson during a talk on simulating tether dynamics—how to get a computer to imagine ripples in a ribbon 100,000 kilometers long—but it could have come during any of the event's dozen or so major presentations. The clear takeaway was this: the main impediment to the space elevator movement is enthusiasm. It's past time to bring the seemingly far-out concept down to Earth.
A space elevator is exactly what it sounds like: an unbroken ribbon roughly one hundred million times as long as it is wide, stretching all the way from Earth to geosynchronous orbit (GEO). They're intended to do to the solar system what railroads did to the continent, allowing 20-ton electric elevator 'cars' to pull themselves into space for a fraction of the cost of an orbital rocket.
ISEC director and former Lockheed engineer Bryan Laubscher pointed out that by burning its fuel and dumping the first two "stages" part-way through its ascent, NASA's vaunted Saturn V rocket only delivered about 5 percent of its starting mass to orbit, and only 2.4 percent to the Moon.
That level of waste is already beginning to stall human efforts in space. Companies like OneWeb, SpaceX, and Samsung are looking to blanket the Earth in high-speed internet by launching potentially thousands of new satellites in the coming decade, but plans will be monumentally expensive when even Elon Musk's pride and joy, the Falcon Heavy, plans to charge $14,000 per kilogram of cargo delivered to GEO.
Once operational, ISEC estimates a space elevator could deliver the same service for $500 or even less. Even better, after a week-long electrically powered ascent to 36,000 km above sea level, payloads could push off the elevator to use the Earth's gravity and slingshot out into the solar system. That's the sort of business model that might realistically let humans not just visit Mars, but colonize it.
A space elevator is a threshold invention, meaning that the sooner we get one, the sooner we can start to think big in space, making Moon colonies and civilian space stations far more realistic concepts. ISEC thinks the idea offers enough economic value to warrant at least a bit of investment from the private sector, but it's often hard to get investors to take the concept seriously. "We're the crazy ones," said ISEC President Dr. Peter Swan, in his opening remarks. "We're the ones who think we can actually get there."
The main source of concern is obvious: the 100,000 km "backbone" that has to endure enormous strain while remaining flexible and incredibly light. ISEC has actually invented a unit of measure for the purpose, the yuri, which represents the ratio between the strength and density of a material under strain. The magic number to begin making early space elevators seems to be around 30 megayuri, while high strength steel cable of the sort that suspends regular elevators comes in around 0.25 megayuri and zylon, an advanced modern tether material, maxes out at less than four.
Amazingly, science fiction author Arthur C. Clarke may have predicted the solution in his 1979 book The Fountains of Paradise, which posited a space elevator with a backbone made of "carbon whiskers"—described as largely identical to modern day carbon nanotubes (CNTs), which are light and strong enough to exceed the requirements for a space tether. The only thing stopping CNTs from revolutionizing everything from sporting goods to aviation is the incredible difficulty of actually making them.
University of Cincinatti materials researcher Mark Haase gave the weekend's keynote address on his work weaving these incredibly strong whiskers into passably strong composites. Haase said that, worldwide, CNTs are already made by the tens of tons every year—but only in short, disordered fragments. The key to a space elevator will be figuring out how to weave longer CNTs into a ribbon, perhaps with atom-thin layers of something like kevlar gluing them together.
A real space elevator project would likely have no trouble cobbling together billions of dollars of investor capital
Haase said the trends in recent research look on track to deliver an early composite space tether material in as little as 20 years—not quite quick enough to let ISEC hit their official goal of a working GEO space elevator by 2036, but potentially not far off.
One outlier in the space elevator community is the multi-billion dollar Japanese construction company Obayashi, which has a plan to build one by 2050. It's a much more ambitious pitch than ISEC's, featuring two tethers and the ability to send 30-person manned missions into orbit. Obayashi's Yoji Ishikawa presented the company's newest computer simulations on tether deployment from an orbital robot and the resonant motion caused as the "climbers" slowly enter and return from space.
Obayashi sees the value of investing in space elevator science now, but the construction company can only work with the tools it is given. Its timeline is only possible if mankind can develop an appropriate super-material for the tether, not to mention things like space power transmission and perhaps even orbital capture of an asteroid to act as as a counterweight at the end of the tether. It's that sort of fundamental research that most lacks for funding, at the moment.
Closest on the horizon is the concept that space elevators beget space elevators. While a 100,000-kilometer tether is at least a couple of decades out, ISEC thinks CNTs could allow a 1000-kilometer version as early as 2025. This would provide partial solutions to modern launch problems but, more importantly, a small scale elevator would dramatically reduce the cost of building a full-scale version. And with a full-scale space elevator in place, building a second would be a relative breeze.
There's definite frustration arising from the fact that, if and when it becomes possible, a real space elevator project would likely have no trouble cobbling together billions of dollars of investor capital. From telecommunications and military ventures to pure science and civilian aerospace, everyone can see the value in maturing the human relationship with space.
The question is whether anyone's willing to pay get it done.