Posted on 03/27/2002 9:32:03 AM PST by RightWhale
The Space Elevator Comes Closer to Reality
By Leonard David Senior Space Writer
posted: 07:00 am ET 27 March 2002
ALBUQUERQUE, NEW MEXICO -- 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.
Still, the mental picture needed to grasp the elevator to space idea…well, 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 Berkeley, California, but carrying out heavy lifting design work in Seattle, Washington.
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 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," he said.
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 Rutgers in Piscataway, New Jersey. "We're moving from the scientific stage of just developing them to actual commercial entities producing them in ton-like quantities," he said.
"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 Ridgecrest, California. "If you do it right, you can take out 96 percent of the effect of the atmosphere on the laser beam through adaptive optics," he said. The strength of the pulsed laser beam is less than the intensity of the Sun, so birds, airplanes, or human eyes wouldn't be affected, he said.
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 Millennium Tower envisioned for Hong Kong Harbor. This incredible skyscraper would be 170 stories tall. Elevator traffic within its walls is estimated at 100,000 people per day.
Edwards also points to the Gibraltar Bridge project. It would span the Straits of Gibraltar, linking Spain and Morocco at a projected cost of $20 billion. The bridge would use towers, twice as high as the world's tallest skyscraper. Roughly 1,000,000 miles (1,600,000 kilometers) of wire cables would be utilized in the project.
"I think those projects are a lot harder than what I'm talking about," Edwards said
This has many practical applications beyond outer space (pun intended). I don't mean to distract from the aerospace applications for it, but there are also plenty of excellent uses for this technology here on Earth.
Thanks for the article. It's very intriguing.
:) ttt
True. What happens when the cable is cut? When cut low to the ground, one thing. When cut higher, another thing.
A good news, bad news story, probably an old one:
Mr. President, I have bad news and good news.
--Give me the bad news first.
The Chinese have landed on the moon.
--Oh. What is the good news?
It was all of them.
Edwards said he is looking into the environmental impacts stemming from elevator operations.A space elevator attached to the equatorial Pacific would irreparably disrupt the migration pattern of the rara avis.
OK, who had the cheese?
Right. There wouldn't be just one space cable. They would be built everyplace around the equator where a suitable anchor could be located --an irregular spider's web of strands with a radius 10 times that of earth itself.
Imagine the potential conflict with commsats in geosynch orbit.
They would be built everyplace around the equator where a suitable anchor could be located --an irregular spider's web of strands with a radius 10 times that of earth itself.A veritable cosmic Tinker Toy.
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