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 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 miningbecoming 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.
When the Space Shuttle Columbia lifted off on April 12, 1981, from Kennedy Space Center, Fla., to begin the first space shuttlemission, the dream of a reusable spacecraft was realized. Since then, NASA has launched more than 100 missions, but the price tag of space missions has changed little. Whether it is the space shuttle or the non-reusable Russian spacecraft, the cost of a launch is approximately $10,000 per pound ($22,000 per kg).
