Imagine a ribbon roughly one hundred million times as long as it is wide. If it were a meter long, it would be 10 nanometers wide, or just a few times thicker than a DNA double helix. Scaled up to the length of a football field, it would still be less than a micrometer across -- smaller than a red blood cell. Would you trust your life to that thread? What about a tether 100,000 kilometers long, one stretching from the surface of the Earth to well past geostationary orbit (GEO, 22,236 miles up), but which was still somehow narrower than your own wingspan?
The idea of climbing such a ribbon with just your body weight sounds precarious enough, but the ribbon predicted by a new report(Opens in a new window) from the International Academy of Astronautics (IAA) will be able to carry up to seven 20-ton payloads at once. It will serve as a tether stretching far beyond geostationary (aka geosynchronous) orbit and held taught by an anchor of roughly two million kilograms. Sending payloads up this backbone could fundamentally change the human relationship with space -- every climber sent up the tether could match the space shuttle in capacity, allowing up to a "launch" every couple of days.
The report spends 350 pages laying out a detailed case for this device, called a space elevator. The central argument -- that we should build a space elevator as soon as possible -- is supported by a detailed accounting of the challenges associated with doing so. The possible pay-off is as simple as could be -- a space elevator could bring the cost-per-kilogram of launch to geostationary orbit from $20,000 to as little as $500.
Not only is a geostationary orbit intrinsically useful for satellites, but it's far enough up the planet's gravity well to be able to use it in cheap, Earth-assisted launches. A mission to Mars might begin by pushing off near the top of the tether and using small rockets to move into a predictably unstable fall -- one, two, three loops around the Earth and off we go with enough pep to cut huge fractions off the fuel budget. Setting up a base on the Moon or Mars would be relatively trivial, with a space elevator in place.
IAA's projections for launch mass over time with different technologies.
Those are not small advantages, and are worth significant investment from the private sector. Governments and corporations spend billions installing infrastructure in space -- an elevator could easily pay for itself, and demand investment from anyone with an interest in ensuring cheap access to it down the line. A space elevator is relevant to scientists, telecoms, and militaries alike -- and with Moon- and asteroid-based mining becoming less hare-brained by the minute, Earth's notorious resource sector could get on-board as well. It will certainly be expensive, probably the biggest mega-project of all time, but since a space elevator can offer a solid value proposition to everyone from Google to DARPA to Exxon, funding might end up being the least of its problems.
This report lays out a number of technological impediments to a space elevator, but by far the most important is the tether itself; materials science has still to invent a substance that could provide the strength, flexibility, and density needed for a space elevator. Existing technologies will be little help; tethers from the EU and Japan are beginning to push the 100-kilometer mark, but that's still a long way off orbital altitude, and the materials for existing tethers will not allow much additional length.
Projecting current research in carbon nanotubes and similar technologies, the IAA estimates that a pilot project could plausibly deliver packages to an altitude of 1000 kilometers (621 miles) as soon as 2025. With continued research and the help of a successful LEO (low Earth orbit; anywhere between an altitude of 100 and 1200 miles) elevator, they predict a 100,000-kilometer (62,137-mile) successor will stretch well past geosynchronous orbit just a decade after that.
Next page: So, how do you build a space elevator?
When you get right down to it, how do you build a space elevator?
The proposed design really couldn't be simpler: a sea platform (or super-ship) anchors the tether to the Earth, while a counterweight (also called an "apex anchor") sits at the other end, keeping the system taught through centripetal force. Though many have dreamed of asteroid-capture missions to wrangle a space rock into being our anchor, the IAA points out that such a mission would likely require a space elevator to be possible in the first place.
Instead, the report argues that a nascent space elevator should be anchored first with a big ball of garbage -- retired satellites, space debris, and the cast-off machinery used to build the elevator's own earliest stages. Interestingly, a tether stretching 150,000 kilometers or more would have enough weight of its own to sidestep the need for a counterweight altogether. All tethers, no matter the length, will have to be made in a curved shape so no single edge-on micro-collision could sever the ribbon entirely -- though at just a meter wide, a collision wouldn't have to be very "macro" to cover the entire silhouette.
Climbers might well deploy huge solar arrays like this to power the climb past about 40 kilometers in altitude.
To keep weight down for the climbers (the elevator cars, if you will), this report imagines them as metal skeletons strung with meshes of carbon nanotubes -- how would you like to ascend to space in a huge future-hammock? Each car would use a two-stage power structure to ascend, likely beginning with power from focused lasers fired from the ground, or with power sent down from a dedicated box satellite. Past 40 kilometers altitude, though, the climber's own solar array should be able to keep it moving with light unfiltered by Earth's atmosphere. IAA hopes for a seven-day climb from the base to GEO -- slow, but still superior (and far cheaper) to the rockets that lead to months-long delays in launches today.
And more importantly, can we get the international cooperation to build such a mega a contraption?
In terms of placement, IAA is unequivocal: a space elevator would be too precious a resource to be built within the territory of any particular nation-state -- they reference the Suez Canal as an example of the problems in giving a self-interested nation control over global infrastructure. Though every government would certainly love a space elevator of their very own, cost considerations will likely make that impossible in the near-term. Purely by virtue of its physical size, a space elevator will stretch through multiple conflicting legal zones, from the high seas to the "territorial sky" to the "international sky" to outer space itself. Each of these presents its own unique legal and political challenges. The US could very well find itself lobbying China for help in building a tether that will help in surveillance of Chinese territory -- this will not be an easy project to plan.
A team works on the YES2 tether, which is more than 30 kilometers long and just half a millimeter wide.
Attacks by terrorists or enemies in war are also a major concern -- though politically neutral, the eventual location of the Marine Stage One base station will immediately become one of the most aggressively defended no-fly zones in the world. It will be watched from beneath by underwater security, at altitude by radar sweeps and fighter patrols, and in space by nearby satellites. Notice that while this would be a stateless project, it would require a state's assets to maintain -- likely via the UN or some new autonomous body tasked exclusively with elevator defense.
Though there are several possible tether materials, carbon nanotubes are the most likely candidate.
Arthur C. Clarke once famously said that we will build a space elevator 10 years after they stop laughing -- and they've stopped laughing. He said that in 2003, and while his timeline may have been off, his sentiment surely wasn't. The concept of a space elevator is taken seriously at NASA these days, as it eyes both shrinking budgets and growing public expectations. Space is quickly becoming a bottleneck in the timeline of human technological advancement.
From mega-telescopes and surveillance nets to space mining operations and global high-speed internet coverage, most of our biggest upcoming projects will require better access to space than we could ever derive from tanks of combustible liquids. It's simultaneously a boring infrastructure project and a wide-eyed dream machine, a mega-project that illustrates how further progress in space will necessarily require global cooperation. In the eyes of this report, that cooperation could end up being the greatest challenge of all.
[Image credit: CCP Games(Opens in a new window)]
