Week of December 1, 2003
Snapshot from the Field
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Going (Way) Up:
Rising toward Reality
by JACK LYNE, Site Selection Executive Editor of Interactive Publishing
"When will the Space Elevator become a reality?"
Author and Futurist Arthur C. Clarke:
Q&A exchange after Clarke's keynote
speech at an early 1990s' conference
Talk about your ultimate high-rise: Scientists are hard at work on a project that will stretch 32 million stories high, topping out at about 62,000 miles (99,200 kilometers). It's the "Space Elevator," and its total projected cost is pegged at between $5 billion and $10 billion.
And it may be a reality within 15 years, say scientists working on the Space Elevator.
Clarke: 'They've Stopped Laughing'But not all of the project's particulars are worked out. That was clear at the second International Conference on the Space Elevator, held earlier this year in Santa Fe, N.M.
Nonetheless, the project represents a coming revolution, many speakers emphasized. One of them was renowned author and futurist Arthur C. Clarke, who used the Space Elevator as a fictional device in his 1978 novel The Fountains of Paradise. The project will fundamentally alter the world in now-unimaginable ways, said the man who penned the mind-bending 2001: A Space Odyssey.
"Really," Clarke responded to an question on the elevator's impact, "what you're asking me is like what you'd ask an intelligent fish if you asked, 'What would it be like if you moved out into this new medium, air?' "
Clarke, who spoke via a satellite link from his home in Sri Lanka, also recalled his earlier remark about the elevator reaching fruition "about 50 years after everybody quits laughing."
He updated that prediction in Santa Fe.
"It will be built about 10 years after everybody stops laughing," Clarke said."And they've stopped laughing."
Going (Very Far) Down:The biggest laugh-stopper is the carbon nanotube. Discovered in 1991, the elongated carbon structure is only one-fifth of the weight of steel, but it's hundreds of times stronger.
Space-Launch Payload Costs
Nanotubes will make up the Space Elevator's key component, its towering cable. That cable would be only about three feet (0.91 meters) wide, but its thickness would be less than that of a newspaper page. Yet nanotubes are so strong that the cable could carry payloads weighing as much as five tons (4.5 metric tons).
Nanotubes have opened the door for the Space Elevator's considerable economies of scale. Current costs for space-launch payloads run between $10,000 to $40,000 a pound. The Space Elevator, though, would cut per-pound costs to $100 almost immediately, dropping them even lower later, project backers say.
"The economics are fantastic," Clarke told the audience in Santa Fe. "I do think it may be the way to space." The Space Elevator, he explained, will facilitate huge advances in fields that include astronomy, processing of materials in microgravity and passenger transport for a suddenly feasible space tourism industry.
Project Likely Headed for Equatorial PacificThe Space Elevator's general site-search parameters are already set. The project will be positioned on an ocean-based platform somewhere in the equatorial Pacific, say the elevator's developers.
That area, they say, has a notable absence of hurricanes and tornados; that's a must to protect a thin base tower that will reach a height of about 31 miles (50 kilometers). The elevator's cable would be attached to the top of the tower.
Once that cable is extended, natural forces will stabilize the entire structure. The Space Elevator's upper half will be thrown outward by the Earth's rotation, while the elevator's bottom end is anchored by gravity.
Four to six payload-carrying platforms would then be attached to the sides of the cable tower. Those platforms will be powered by high-speed electromagnetic propulsion, the same technology that now ferries passengers around many airports.
Only the platform's power system would be much, much stronger, generating speeds that developers estimate could conceivably reach thousands of miles an hour. Payloads will travel all the way to the top of the Space Elevator in about 90 hours, scientists estimate.
Waiting for a Better NanotubeGetting the cable out there, though, seems to be the project's greatest challenge. "The cable is the riskiest part," said Bryan Laubscher, a scientist with Los Alamos National Laboratory, which co-sponsored the Space Elevator conference with ISR.
Project developers have devised a system that they say will put the cable in place in space: A free-electron laser system attached to the platform would power "climbers" that will take the cable toward the heavens. Each of the climbers would increase the cable's length. All told, 300 climbers would be used to extend the cable to 62,000 miles - a process that will take about two and a half years, scientists say.
Only one problem there: Carbon nanotubes don't reach that far yet. In fact, the longest piece of the material made to date has only been a few feet long.
"The length [of the nanotube-made cable] is not the challenge," Rodney Andrews, associate director in Carbon Materials at the University of Kentucky's Center for Applied Energy Research (www.caer.uky.edu), told the Santa Fe conference. "It's getting the strength."
Researchers, however, say that research labs will soon crack the code to devise the right strength, perhaps by using composite fibers containing nanotubes.
Debris, Terrorism Other Major ObstaclesThe Space Elevator also faces some other major hurdles aside from cable strength. One of the biggest is space debris, particularly the tons of dead or dying satellites now floating in space after 40 years of human space exploration.
"I don't quite know how we're going to solve the issue of space debris," Clarke said. "That's going to be a major problem in making the Space Elevator practical."
The project will have a considerable amount of debris to contend with, judging from an analysis by David Smitherman, a scientist with NASA's Advanced Projects Office at the Marshall Space Flight Center. Each month, Smitherman explained, 52.5 objects measuring at least four inches (10 centimeters) across would get within 0.62 miles (one kilometer) of the Space Elevator; and 12.5 of them would pass within 0.31 miles (0.5 kilometers). The elevator will hit its biggest clusters of debris, he added, at altitudes between 564 and 946 miles (910 and 1,525 kilometers).
One way to ward off debris would be to attach the project's base to a mobile platform, suggested ISR Director of Research Bradley Edwards. That would enable the elevator ribbon to be moved out of harm's way. Climbers built specifically for repairs could go up to fix minor debris damage to the cable, Edwards said.
Contending with TerrorismAnother of the project's challenges lies outside the realm of scientific advancements - terrorism.
"The Space Elevator is a physically fragile thing," said Los Alamos Deputy Director for Science and Technology William Press. "We may need a stable world society to support it."
All in all, then, the Space Elevator still faces a long and imposing list of obstacles.
But the project's backers contend that the venture will eventually divide space travel into two epochs, the first being B.C. - "Before Cable." The Space Elevator's many barriers will be broken, they believe.
"There are solutions to all these problems," said Clarke.
And the project isn't without historic parallels, he insisted.
"The first transatlantic cable," Clarke contended, "was the Victorian equivalent of the Space Elevator."
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