Picture if you will...
Picture driving by a sprawling meadow. As you look out of the window, a black vertical hair seems to be hanging in front of your eye and it catches your attention. But then you notice that it is fixed in space... It's a thin black line, almost like the trace of a film-scratch on a picture. Seeing that it's practically right in front of you, you get out for a closer look.
Incredibly, it turns out that the line was only 20 meters away when you spotted it -- a black tether only a quarter-inch in diameter and anchored to the ground. The tether reaches straight up and quickly disappears from view into the clear blue sky. You tug down on the tether, and sure enough there is something holding it up, though there's no balloon, helicopter or tall structure within miles.
To understand what's going on, imagine zooming out until the meadow, nearby cities and finally the entire planet appears the size of coin. The tether spans almost eight times the diameter of the planet, points directly outwards, and is strapped to a steel ball. As the planet rotates, it carries with it the tether and ball, like a super-long spinning yo-yo; as the ball tries to escape, it keeps the tether taut.
Welcome to the space elevator: a stationary tether rotating with the Earth, held up by a weight at its end, and serving as a track on which electric vehicles called "climbers" can travel up and down carrying about 10 tons of payload. The technical details, of course, are much more involved than this (find out more using the tabs at the top of the page).
Although space elevators don't exist (yet), how could we benefit from one?
First, travel to space becomes a very straightforward matter. There are no intense gravity-loads during the trip, no acoustic vibration, no onboard fuel, nor any of the rest of the drama (and cost) associated with rocket launches; it might feel something like riding a modern train. Thus the entire process of going to space becomes much more mundane, simple and cheap.
Second, payload size is practically unlimited because space elevators can be built to any scale. Replace the quarter-inch tether with a 2.5-inch tether, and the elevator could lift 100 times the weight. That's more than 1,000 tons in this case -- about 40 shipping containers or three complete International Space Stations -- per day!
Last but not least is the cost. By using a combination of solar power and ground-based lasers to power space elevator climbers, the direct cost of propulsion could be just dollars per kilogram, whether you're going to orbit or launching yourself all the way to Mars.
For Space Elevator advocates such as myself, reducing the cost of a rocket launch payload to under $1,000 per kilogram is not enough. When I fly on a jetliner, I pay about $1 per pound (including luggage!) and complain about the service. This type of pricing, perhaps $10 per pound, is what it takes to build a viable space-based economy.
"Where's my space elevator?" you ask.
Yuri Artsutanov first proposed the idea in 1960, and up until 15 years ago it was purely in the realm of science fiction. But Sumio Iijima's discovery of carbon nanotubes (CNTs) in 1990 and Bradley Edward's engineering research in 2001 is clearing the roadmap to a space elevator's construction.
Still, what stands between us and a space elevator is a large improvement in tether technology -- a macroscopic thread that takes full advantage of the incredible strength of CNTs. Beyond the tether, other challenges are relatively straight forward, and most certainly easier than the challenges faced by the architects of the Space Shuttle or space station.
Scientists today are conducting a lot of research in the field of nanotube tethers for commercial applications on Earth. Sooner than most people expect, I hope a space-elevator-capable CNT tether will become available and kick the space elevator's development into high gear.
In his last years, Sir Arthur C. Clarke predicted that the space elevator will be built "about 10 years after everyone stops laughing". I believe people will stop laughing once a proper tether is demonstrated, and we think that this will happen within 5 to 10 years. Hopefully that means about 15 to 20 years before the first launch.
I'd also change "will be built" to "can be built" because, as always, technology is only a necessary condition -- not a sufficient one. It's a matter of political and popular will for mankind to venture into space. The space elevator offers us almost infinite promise, but it's up to us to take the initiative and benefit from this promise.
Ben Shelef is a co-founder of the Spaceward Foundation. An aerospace engineer by day, he dons the cape and mask of space elevator crusader by night and engages in daring escapades such as running the $4 million Space Elevator competitions in collaboration with NASA, researching Carbon Nanotubes, and writing advocacy articles like this one.
Thanks to Dave Mosher for editing this page.