Looking around at the scientists and enthusiasts assembled for this year's conference of the International Space Elevator Society (ISEC), many of whom have flown halfway around the world, it's easy to forget that a space elevator is currently pure fiction. The energy of the place wouldn't allow skepticism to live longer than a single sentence—I asked multiple attendees if we can really build a 20-ton elevator car capable of climbing a millimeter-thick tether at 200 km per hour all the way to space. The answer, averaged over several responses: I mean, probably.
Given a few plausible breakthroughs in power transmission and materials science, mankind certainly seems capable of surmounting each of the intermediate challenges on the way to a space elevator, climbers included. Yet just as important as developing the ability to build a space elevator is developing a motivation to actually do so, a pitch that's a whole lot more specific than offering a cheap overall path to orbit. It's not that we couldn't someday build a space elevator, it's that I wonder whether anyone has yet come up with a compelling enough reason to actually do it.
The most commonly predicted early uses for a space elevator's incredibly cheap launch costs—as little as $500 per kilogram—are things like Mars colonies and global satellite internet. Made economical by a space elevator, such inspirational projects would begin right as the Earth is set to continue its descent into the desiccated-yet-waterlogged chaos of global climate change. To actually build one of these incredibly complex machines at a time like that, the pitch will have to become more about necessity than inspiration.
There are two distinct types of challenges facing a space elevator: those that are totally impossible at present, like producing a flexible 100,000 kilometer elevator cable stretching well past geosynchronous orbit (GEO), and those that seem physically possible but incredibly difficult, like building a car to climb up that tether into space. There is a quantifiable physical principle standing between humanity and a space tether: a ratio of tensile strength to weight that proponents can graph with a nice red line.
The barrier to a climber, on the other hand, is one of engineering and design. These are the less talked-about barriers to a space elevator, the possible but incredibly difficult components that must be built before a single load can move up the elevator. Virtually every step in the construction, deployment, and operation of a space elevator will require multiple major, if achievable, firsts.
According to the International Academy of Astronautics' roadmap, to build a space elevator, you have to come up with the satellite that will carry the tether you invented into orbit over a spot you've cleared with most major world governments, then lower it by a process you created to hook up with a super-ship you designed. Depending on the specific type of elevator you're building, you may then have to build a brand new space station or even attach the end of the tether to a captured asteroid.
You'll then be responsible for the single longest line in human history, and need to coordinate a contingent of space, air, surface, and underwater military units to protect the elevator every second of every day. Managing such a vitally important piece of global infrastructure will require you to make legal and political breakthroughs just as difficult as the engineering achievements that came before.
You also have no choice but to simply hope that the thing doesn't get hit by a meteor or piece of man-made space debris. One of ISEC's elevator concepts features an idea for a failsafe that rapidly lets out a few hundred kilometers of slack from the top station if it detects a break in the tether down near the surface of the Earth. That might save the majority of the length for later reattachment. And if the breakage occurs higher than a few thousand kilometers up the tether, even with that system in place? As ISEC Director Peter Swan told me, "Well, tough shit."
Almost every subsystem of a space elevator, from space-based laser power to climber locomotion systems to the ocean platform anchor, will be its own major research project in need of years' worth of testing and prototyping. ISEC has said that it expects no one space agency could really hope to take on a space elevator alone.
A space elevator would be such a massively complex effort that I think an honest attempt to build one could at least partially unite the world's largest powers. Putting humans on the Moon inspired a space race, but it was not a necessary enough goal to have been capable of inspiring cooperation between rivals. That's what we'll need to motivate global cooperation on a space elevator: something better than putting a man on the Moon.
The only candidate that springs to mind is climate change. It might work if pitched as a package with some sort of highly efficient space-based method of carbon capture—we slowly build a space elevator, use it to quickly build several more, then get to changing the bulk makeup of the atmosphere. More pessimistically, a space elevator might work as a sort of planetary escape hatch, a way for mankind to start abandoning a mangled planet in favor of a pristine new one.
Without a vital motivator like that, a space elevator might remain a practical impossibility until most other major global concerns have been dealt with—and right now, that seems a lot further out than 2036.