Still, the mental picture needed to grasp the elevator to space ideawell, you can't be weak of mind.
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 21st 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.
Thought experiment
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." That's the matter-of-fact feeling of physicist, Bradley Edwards of Eureka Scientific in
Edwards told SPACE.com that he's been wrapped up in space elevator work for some three years, supported by grants from NASA's Institute for Advanced Concepts (NIAC) program. "I'm convinced that the space elevator is practical and doable. In 12 years, we could be launching tons of payload every three days, at just a little over a couple hundred dollars a pound," he said.
"In 15 years we could have a dozen cables running full steam putting 50 tons in space every day for even less, including upper middle class individuals wanting a joyride into space. Now I just need the $5 billion, Edwards added.
And so it grows
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," Edwards said. But the right stuff in terms of cable material is no longer thought of as "unobtainium", he said.
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.
Stronger than steel
The hurdle to date, Edwards said, has been the commercial fabrication of carbon nanotubes. Both
Given the far stronger-than-steel ribbon of carbon nanotubes, a space elevator could be up within a decade. "There's no real serious stumbling block to this," Edwards explained.
"The making of carbon nanotubes is moving very quick," said Hayam Benaroya, a professor in the Department of Mechanical and Aerospace Engineering at
"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," Benaroya said.
Reel world high-wire act
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," Edwards said.
Using a laser beam to boost the climbers into space is doable, said Harold Bennett, president of Bennett Optical Research, Inc. of
Return on investment
Eric Westling, a Houston, Texas-based consultant on the space elevator, is bullish on the concept. Spending billions on a space elevator is small change for a big purpose.
"Other than the invention of some Buck Rogers engine, the space elevator is the only system for accessing space that is subject to the economics of scale. It's a true return on investment enterprise. The cost of space travel has to become an incidental part of the overall cost of what we're trying to get done," Westling said.
"It will change the world economy. It's worth what ever it costs to put it up," Westling said. An initial elevator, he added, is sure to give birth to even larger systems, capable of handling larger loads of up and down traffic.
"I'm looking at a business plan that shows some investor could triple his or her money in about 6 years, and the initial investment could be as low as $5 billion," Edwards said.
Building the impossible
The elevator to space concept does entail aggressive research work. As example, Edwards said he is looking into the environmental impacts stemming from elevator operations. Being studied too is impact of lightning, wind and clouds on an Earth-to-space cable system. Space elevators for use on other worlds, like Mars and the Moon are receiving attention as well.
One thing to keep in mind. Building the impossible is done here on Earth routinely, Edwards said.
Take for instance the $13.5 billion
Edwards also points to the
"I think those projects are a lot harder than what I'm talking about," Edwards said.
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