To build a space elevator, you'll need a very light car and a very strong string.
- By Michael Milstein
- Air & Space magazine, March 2006
Steven Jones crouched in a California parking lot, hoping to pioneer the next great stride into space. The clean-cut, 22-year-old senior in engineering at the University of British Columbia was tinkering with a robotic contraption he and fellow students built out of solar cells, motors, hot-tub tubing, and pieces of a purple bicycle.
Cost: about $1,000. Mission: Climb a 220-foot blue strap dangling from a crane at NASA’s Ames Research Center, powered by only a 10,000-watt searchlight aimed at the contraption’s solar panel. Reaching the top in less than three minutes would win Jones and his partners $50,000 in a NASA competition, plus a permanent place in the lore of the far-out, far-off, and far-fetched concept known as the space elevator.
The idea remains little more than a dream, at least for now. But contest promoters boasted that Jones and his competitors possessed nothing less than prototypes of a dream machine that will one day motor us into orbit along super-strong cables as easily as today’s trains carry us to the next town.
The competition offered a glimpse into everything the dream of the space elevator has going for it and against it: on the one hand, energy, ingenuity, and confidence that it is possible, and on the other, monumental technical obstacles and unforeseen mechanical breakdowns that make it seem unattainable.
As Jones’ robot, Snow Star One, inched off the launch platform, the thin crowd of onlookers cheered. But the robot was sluggish. The corrugated hot-tub hoses, clamped onto either side of the strap for grip, kept slipping. After a few feet the climber’s solar cells melted in the searchlight’s beam, black plastic dripping from them like icicles.
Snow Star One struggled to a stop.
“That robot was pretty slow,” a young spectator informed Jones as he disassembled it, rushing to catch a flight home to finish his midterms.
By the contest’s end, none of the robot climbers came close to claiming the $50,000 prize; some didn’t move at all, and only two covered any distance on light power. The same slowness could be said to describe the overall progress in the development of the space elevator itself.
In fact, NASA backed the contest only to encourage precursor space technology. “We have no plans to build a space elevator,” says Brant Sponberg, manager of NASA’s Centennial Challenges program, which offers cash prizes to fuel innovation in the same vein as the X Prize. The idea is to attract interest in space projects from inventors beyond the usual circle of big contractors that routinely seek NASA funding. “But when you take a space elevator apart into all of its pieces, there are a lot of things we’re interested in,” Sponberg adds. “The basic physics are practical, but the material—not yet. That makes it a hard sell for the agency right now.”
But belief is growing that a space elevator may be in our future. A NASA report completed in 2000 predicted a space elevator would become practical in the second half of this century. Optimists say a functioning system is perhaps no more than a few decades away, if someone savvy in the private sector decides to attempt one.
A couple of companies, backed by venture capital, are already investing in the basics and have scoped out the climber robots in California for ideas. Believers say that as crazy as the space elevator sounds, it’s even crazier to not pursue what could be the cheapest and most reliable route into space.
“We need to sort of open up and use our imagination and creativity,” says Robert Cassanova, director of the NASA Institute for Advanced Concepts in Atlanta, which has paid for some initial studies on the idea. “We need to start with a new sheet of paper and come up with some new ideas. That’s sort of the story of the space elevator. It’s one of these really big ideas. Finally people are starting to take a serious look at it.”
Although the gadgets that showed up in California are as far from the real thing as a magnifying glass is from the Hubble Space Telescope, here’s how the finished concept would work: A floating platform of some kind, perhaps a big ship, would station itself somewhere along the equator. From there a ribbon made of a material stronger than diamonds would stretch about 62,000 miles into space.
The end of the cable would carry a counterweight of some kind, maybe rockets or other left over equipment from construction. The fulcrum of the elevator cable mass would have to be positioned at 23,000 miles— at geosynchronous orbit, where satellites constantly tower over the same point on the planet. But for its center of gravity to be positioned at geosynchronous orbit, the far end of the cable must extend way beyond that point. Like a teeter-totter that sticks out to either side of the balancing point, the cable must extend 62,000 miles, according to the most prominent approach being considered.
Earth’s rotation would whirl the enormous wobbly tower, like a tennis ball on the end of a string. The momentum of the spin would keep the cable taut, and roomy elevator cars would shuttle people and cargo between stations along the line.
The elevator cars would be powered by a laser on the ground—much like the searchlight in the California parking lot—beaming energy to collector panels on each car.
Daily elevator departures would make expensive and risky rocket launches obsolete. Costs of lofting satellites could fall substantially, making communications and everything else that depends on them far cheaper. With many more people able to afford it, space tourism would become truly practical. Or so elevator champions, like Bradley Edwards, believe.
Edwards attended the elevator challenge not to compete but to cheerlead. He first got curious about the space elevator as a physicist at Los Alamos National Laboratories in New Mexico after hearing the naysayers proclaim it would never work. The technology conronts many dangers, and Edwards has heard them all. What happens, for example, if the elevator cable collides with something in orbit? About 100,000 pieces of debris big enough to sever a cable speed around Earth. Space junk is so plentiful that a piece could slice through the cable roughly every 250 days. Such a catastrophe would leave anything above the break careening through space, and anything lower falling in a fiery reentry toward the planet.
Edwards has a plan to avoid this. First, the cable would be designed to withstand impacts. Instead of a single strand, the cord would consist of a flat ribbon of nanotube fibers lined up side by side and reinforced at intervals by horizontal strips of high-strength tape. If a speeding meteorite cut through a few fibers, the tape above and below the break would hold the rest tight and shift the load onto adjoining fibers. Also, the flat bundle of fibers would have a slight curve to it, so a small meteorite that hit it sideways would not slash through all the fibers.
A robust system to track orbiting debris, Edwards notes, would spot anything endangering the elevator and alert the ship or floating platform at the base of the cable to steer clear. A mile or two of movement ought to be enough to dodge the dangers, Edwards estimates.
If the materials and money are available, advocates argue that no law of physics prevents an elevator from working. Then again, you could have said the same about building a robot able to climb a rope.
Some of the machines that competed in the challenge resembled assemblies of Erector Sets, while others looked like they could stop a tank. Brian Pierce and his teammates spent more than a year constructing their climber from an extra wheelchair frame that team leader Vincent Lopresti had in his closet in Texas. They sold T-shirts and coffee mugs to raise money for parts and hit up companies such as Dremel for tools and Sunrise Medical, a medical supply company, for the solar cells. The team scavenged the motor from a kid’s Mongoose scooter, and tension springs from a Chevy carburetor.
For Lopresti, 40, the competition signaled that space is finally open to the public, and he wanted in. A software-designer-turned-engineer who thinks his home near Dallas would make a good spaceport, he grew so obsessed with the space elevator he couldn’t think about much else. He turned designs over and over in his head. “It’s almost like a kid in a candy store; there are so many different options,” he said. “I have all kinds of junk in my house, and it just all started falling together.”
Their climber evolved into a kind of sideways wheelchair with a motor on one side and a solar panel as a counterbalance on the other. Lopresti foresees an extraterrestrial gold rush as a space elevator opens the door to mining moons and planets and collecting and recycling satellites that have gone kaput.
“I’m going to do what I can to make sure that happens,” said Lopresti, zipping around in his wheelchair at an industrial park in Mountain View, California, where teams tuned up their climbers before the competition. It was tense as competitors sized up opponents they’d face the next day. Some worked through the night, struggling with last-minute fixes.
The trouble they all ran into was one that has always dogged spacefarers: Lifting even a pretty small craft takes a lot of power. That’s especially true when relying on solar panels, which capture only a small slice of energy from light falling on them. Even the industrial searchlight provided for the contest, as bright as it was, did not generate much juice.
Lopresti’s climber, Space Miner, wouldn’t budge. “We cut off all the extra things, but it’s still 70 freaking pounds,” an exasperated Pierce
Other teams tried novel ways to wring power from the light. Engineer Matthew Abrams arrived from Maryland with his climber in suitcases bearing duct-tape labels that said “Robot parts—fragile.” When he got it together, a reflective dome focused light on a water-filled canister.
The plan was for the water to heat up, producing pressure to drive a piston that would yank the climber up the strap. But the water hit only 150 degrees instead of the 300-plus Abrams needed.
“That’s all?” Abrams asked in disbelief, watching a thermometer tick off the degrees much too slowly. “We’re screwed.”
None of it discouraged Bradley Edwards. He has the cost penciled out at around $10 billion, the price of a few space shuttles. It would take about 15 years to build, he said, once we set our minds to it. “It’s definitely doable. The question is just: When is it going to be built and who’s going to build it?”
That’s why he started his Seattle-based company, X-Tech Projects—to help propel the space elevator toward reality. Edwards, who has a boyish look and wry sense of humor, knows that developing an elevator will require a bit of showmanship. He’s talking with Las Vegas casinos about building mock space elevators that would be part amusement-park ride, part teaching tool, and part public relations gimmick. Tourists would hop in an elevator that, simulating the real space elevator he envisions, would whisk them to a deck where they could see prototype elevators and take in simulations of the scenery of space.
If the real thing comes out anything like Edwards’ dream, it will be quite a ride. Elevators lifting off for space would accelerate upward as they escaped Earth’s gravity, but the trip to orbit would take about a week. Passengers might dine and sleep, as on a modern cruise ship, as they grew lighter and lighter until they enjoyed the effects of microgravity.
The fantasy of such a ride bounced around science fiction circles for decades and was popularized by Arthur C. Clarke in his 1978 novel, Fountains of Paradise. But in the 1990s a Japanese researcher took the concept out of the realm of science fiction when he developed the carbon nanotube, a tiny interlocking lattice of carbon atoms that has taken on such legendary status it’s hard to tell where reality ends and myth begins.
Nanotubes are, without a doubt, unbelievably light and strong—at least 50 times tougher than steel and harder than a diamond. A sewing thread made of them could easily dangle a limousine. The drawback is that the longest nanotubes produced so far are no more than an inch or two. Space elevator boosters, ever the optimists, point out that that’s far longer than only a few years ago.
But it’s also far shorter than the tens of thousands of miles they need to cover. Elevator proponents now hang their hopes on research that will eventually blend nanotubes with materials like high-strength plastic and spin the mix into long fibers as strong as the nanotubes they contain.
“The big issue is how do you put them together so you get their strength in the composite,” says Rodney Andrews, a nanotube researcher at the University of Kentucky’s Center for Applied Energy Research.
Not all hopes are pegged on government funding. A Seattle startup company, LiftPort Group, is gearing up its own nanotube factory to tap into commercial demand while also exploring how nanotubes might serve a space elevator. “A lot of people think: If we just have nanotubes, we start throwing this thing together,” says LiftPort president Michael Laine. “But we still have a lot to learn. We have to build a lot of bad stuff before we start building the good stuff.”
LiftPort built its own ribbon-climbing robot and got clearance from the Federal Aviation Administration to run it up the tether of a 12-foot balloon over the sagebrush of eastern Washington in September. Laine sees profit there too: LiftPort hopes to market the robots for aerial surveillance, generating income to develop better robots and space elevator designs.
“We don’t know what we’re going to get out of a space elevator,” says Laine, “but I’m damn sure it’s going to be profitable.”
One evening during the competition, about 75 people gathered in a big garage where they sipped wine and waited for a string to break. It was the second half of the NASA-sponsored cash challenge, a test to see if anyone could come up with material stronger and lighter than what’s available off the shelf today.
Every entry had to be very lightweight, just like the space elevator cable, with its six feet weighing less than a penny. Contestants had to beat a “house tether” made of the best off-the-shelf material. The house tether had a built-in advantage: It was allowed to weigh 50 percent more than any of the entries. If any could beat the house, the team would win $50,000 and become the frontrunner in a similar competition planned for 2006.
The outcome might hint at whether the elevator can be built within our lifetimes. Ben Shelef, co-founder of the Spaceward Foundation, a non-profit organization that ran the event with NASA money and touts space elevators to schoolchildren and engineers with equal fervor, has a timeline worked out. If the winner of each year’s tether competition proves 50 percent stronger than the year before, the competition should lead by 2013 to material tough enough to string up the space elevator.
But only four people entered the strong string contest, and no one brought a nanotube. The house tether beat all comers: The strongest competitor broke under about 1,250 pounds of stress.
Since no one won the $50,000, Shelef’s schedule was set back at least a year, and all the prize money will roll into next year’s contest.
Tell all the engineers you know. There’s $400,000 available all this year for the owner of a robot climber or a length of stronger-than-imaginable string. Easy money?