Then 229 more climbers will follow, adding more nanofiber-composite filaments until, after two years, the ribbon reaches a width of roughly three feet. All 230 climbers will cluster under the deployment booster to serve as a permanent counterweight. The completed ribbon and counterweight can support a steady stream of climbers, each capable of hoisting 13 tons of cargo and/or people at 125 miles per hour and reaching geosynchronous orbit in seven days. In the early stages, ascended climbers can be put into parking orbits. As more ribbons are constructed and operating costs drop, the climbers can be rounded up and brought back down.
NOT EXACTLY A CABLE
The ribbon on which the climbers travel
will be made of carbon nanotubes embedded
in polymer. The foot-long, half-inch-wide
sample stretched across the frame above is
one-hundredth as strong as the ribbon needs to be.
“The problem is the matrix, not the nanotubes,”
says Edwards. “The carbon-carbon bond
in the nanotubes themselves is the strongest
bond in nature.”
Several ribbons in full-scale operation will open the heavens for solar satellites that can beam power back to Earth, large-scale zero-gravity manufacturing, space tourism, better global environmental monitoring, orbiting observatories, removal of man-made debris from Earth orbit, asteroid mining, and Mars-colonizing ships filled with hundreds of people. “The space elevator could be a catalytic step in our history,” Edwards wrote in his 2002 book (coauthored with Eric Westling), The Space Elevator: A Revolutionary Earth-to-Space Transportation System.
The plan is slowly building an audience of fans. Since he joined the Institute for Scientific Research last year, Edwards has been spending a good deal of his time flying around the world, laying out the blueprint to scientific groups in presentations that take up to five hours. “I go to a place like the Center for Astrophysics, and the room is packed because people have been saying, ‘Let’s go heckle this guy about the space elevator,’” he says with a grin. “They say to me, ‘You didn’t think about this. You forgot about that,’ and I say, ‘Yes, we covered that,’ and I show them. At the end, they come up, give me their cards, and ask if they can help.”
Edwards will need all the assistance he can get. The very first step—making the ribbon—still strikes some as too difficult. “I was overcome by the giggle factor,” says Rodney Andrews, associate director in carbon materials at the University of Kentucky’s Center for Applied Energy Research, as he recalls talking to Edwards two years ago. The physicist had called Andrews about the nanotubes he makes in his lab. “I drive Brad nuts, because he wants me to say we can do this. What I will say is that it’s an interesting project, and there is nothing yet that says you can’t do it.”
Andrews’s skepticism stems not from doubts about the nanotubes themselves—they are more than strong enough for a space elevator—but from the difficulty of embedding them in high concentrations in a material like polypropylene. The little sample in Edwards’s briefcase came from Andrews’s lab. It’s just 1 percent nanotubes; the rest is a polymer matrix. The stresses on the space elevator’s ribbon will require it to consist of 50 percent nanotubes. To get to that point, Andrews says, the nanotube-matrix bond has to improve. “The question is, can we make a system where the nanotube is chemically bonded to the matrix?” To this, he can only say, “Lots of people are working on it.”
Assuming this large problem is solved, many only slightly smaller ones wait their turn. “The one people bring up most often is debris,” says Edwards. Since the dawn of the space age in the late 1950s, low Earth orbit has become a junkyard, with about 110,000 hunks of old spacecraft one half inch or larger hurtling at speeds as high as 30,000 miles per hour. Pieces moving 20 times faster than a high-powered rifle bullet would damage even the space elevator’s superstrong fibers. Edwards’s response: Make the ribbon’s base mobile so that it can dodge the biggest pieces that NASA tracks (a 30- to 60-foot movement would be needed every six days); make the ribbon wider in low Earth orbit, where debris is most plentiful; and regularly patch small gashes.
Other concerns include the viability of laser-powered climbers. In Edwards’s scenario, ground-based solid-state lasers would beam at photovoltaic cells on the climbers’ undersides. Edwards says each 20-ton climber will require 2.4 megawatts of power, roughly the amount needed to power 650 U.S. homes. Is it possible to beam that much power with current technology? At least one expert is optimistic. “Yes, absolutely,” says Neville Marzwell, advanced concepts and technology innovation manager at the Jet Propulsion Laboratory. He points out that the space-based defense investments of the Reagan years led to huge advancements in laser development and that “the technology has made quantum jumps in the last 20 years.” He says ground-based tests have shown it is possible to beam “five times as much power as the space elevator would need.”
