Make way for the ultimate high-rise project: the space elevator. Long viewed as science fiction "imagineering", researchers are gathering momentum in their pursuit to propel this uplifting concept into actuality.

Forget the roar of rocketry and those bone jarring liftoffs, the elevator would be a smooth 62,000-mile (100,000-kilometer) ride up a long cable. Payloads can shimmy up the Earth-to-space cable, experiencing no large launch forces, slowly climbing from one atmosphere to a vacuum.

Earth orbit, the Moon, Mars, Venus, the asteroids and beyond - they are routinely accessible via the space elevator. And for all its promise and grandeur, this mega-project is made practical by the tiniest of technologies - carbon nanotubes.

Seen as an engineering undertaking for the opening decades of the 21^st century, the space elevator proposal was highlighted here during the 2002 Space and Robotics Conferences, held March 17-21, and sponsored by the Aerospace Division of the American Society of Civil Engineers.

Science fiction writers have been deploying space elevators for years. Space visionary, Arthur Clarke, centered his novel of the late 1970s, The Fountains of Paradise, on the notion. Also, among other writers, Kim Stanley-Robinson's Red Mars noted the soaring splendor of an elevator to space. Furthermore, the scheme has bounced around technical journals for decades. Some call it a "thought experiment", but others point out that space exploration B.C. -- "Before Cable" -- will pale contrasted to what's possible within ten to fifteen years. "Even though the challenges to bring the space elevator to reality are substantial, there are no physical or economic reasons why it can't be built in our lifetime."

For a space elevator to function, a cable with one end attached to the Earth's surface stretches upwards, reaching beyond geosynchronous orbit, at 21,700 miles (35,000-kilometer altitude). After that, simple physics takes charge.

The competing forces of gravity at the lower end and outward centripetal acceleration at the farther end keep the cable under tension. The cable remains stationary over a single position on Earth. This cable, once in position, can be scaled from Earth by mechanical means, right into Earth orbit. An object released at the cable's far end would have sufficient energy to escape from the gravity tug of our home planet and travel to neighboring the moon or to more distant interplanetary targets.

Putting physics aside the toughest challenge has been finding a super-strong cable material. That's what has kept this idea in science fiction for 40 years. But the right stuff in terms of cable material is no longer thought of as "unobtainium".

The answer is carbon-nanotube-composite ribbon. Small fibers of the material are set down side-by-side, then interconnected to form a growing ribbon.

The hurdle to date, has been the commercial fabrication of carbon nanotubes. Both U.S. and Japanese firms, among others, are ramping up production of carbon nanotubes, with tons of this now exotic matter soon to be available. That quantity of material is going to be around well before five years time. It's not going to take long.

Given the far stronger-than-steel ribbon of carbon nanotubes, a space elevator could be up within a decade. The making of carbon nanotubes is moving very quick. Perhaps within our lifetimes we might actually see real designs of skyhooks and space tethers, these kinds of things. They may be feasible at reasonable cost.

Getting the first space elevator off the ground, factually, would use two space shuttle flights. Twenty tons of cable and reel would be kicked up to geosynchronous altitude by an upper stage motor. The cable is then snaked to Earth and attached to an ocean-based anchor station, situated within the equatorial Pacific. That platform would be similar to the structure used for the Sea Launch expendable rocket program.

Once secure, a platform-based free-electron laser system is used to beam energy to photocell-laden "climbers". These are automated devices that ride the initial ribbon skyward. Each climber adds more and more ribbon to the first, thereby increasing the cable's overall strength. Some two-and-a-half years later, and using nearly 300 climbers, a first space elevator capable of supporting over 20-tons (20,000-kilograms) is ready for service.

If budget estimates are correct, we could do it for under $10 billion. The first cable could launch multi-ton payloads every 3 days. Cargo hoisted by laser-powered climbers, be it fragile payloads such as radio dishes, complex planetary probes, solar power satellites, or human-carrying modules could be dropped off in geosynchronous orbit in a week's travel time.

Read more: http://technicalstudies.youngester.com/2010/04/make-way-for-ultimate-high-rise-proje.html