Space elevator ups and downs
Posted: Monday, October 02, 2006 6:16 PM by Alan Boyle
The results are in from this summer's balloon-borne broadband test, conducted by LiftPort in the skies over Washington state's Kitsap Peninsula with approval from the Federal Aviation Administration. The test was meant to find out whether balloon-supported aerial platforms could provide Internet service for remote areas - as a small, commercial step toward creating an elevator to outer space. There's good news, and there's bad news.
First, the good news: For most of the 60-day test, the balloons stayed aloft and worked like a charm as a broadband broadcast station in the sky, said LiftPort's founder and president, Michael Laine.
The Internet connection was wired up to a balloon-borne Wi-Fi transmitter from the orchard home that served as the experiment's base of operations, at an undisclosed location near Washington's Hood Canal Bridge. To test the reception, LiftPort's team drove around the area and used a "war-driving" program to hunt for the Wi-Fi connection. "We were able to get 100 percent from 1,000 feet away, 1,500 feet away and so on, as long as you were within the line of sight," Laine told me today.
Laine said the balloons stayed up 59 days in a row, putting in a "flawless performance" at heights of up to 300 feet (90 meters).
Now for the bad news: "On the last day, we did have some problems - we actually got blown down," Laine said. It turned out that there was a "fail-over point" for the balloon design when wind speeds reached 30 to 35 mph (48 to 56 kilometers per hour), he said.
Even when the balloons stayed up, the winds put significantly more of a load on the apparatus than Laine expected. In fact, the winds dragged about a half-ton of anchoring ballast more than 60 feet (18 meters) across the ground, he said.
"Everything that we learned seems kind of obvious in hindsight, but you do the math and you still get surprises," Laine said. "That's stuff that you wouldn't see in a six-hour test."
Six hours was as long as LiftPort's previous tests lasted. In the long run, LiftPort is hoping to develop carbon-nanotube tethers and robotic climbers hardy enough to connect with platforms that are tens of thousands of miles above Earth's surface. Theoretically, this kind of space elevator could be used to carry payloads up to orbit for a fraction of the cost of a rocket launch.
In the shorter run, LiftPort is hoping to adapt elements of the space elevator scheme - such as the nanotubes, the tether setup or the climbers - for more terrestrial commercial applications. That's the point behind the balloon Wi-Fi tests, which concluded Sept. 18.
The conclusion is that the scheme is "not ready for prime time yet," Laine said. "It's still very much a research and development project."
In addition to the wind problem, LiftPort's team found that their off-the-shelf tethers - made out of the kind of material used in seat belts - really weren't up to the challenge. The tension deformed the tethers in such a way that the robot climber couldn't scuttle up on them the way it was supposed to do.
Then there were the bugs, and we're not talking about software here. "Every other day or so, we would take the ribbon down and examine it inch by inch to see if we could detect if there were tears on it," Laine explained. "And that's how we discovered that there were bugs living on it."
Laine had hoped that airborne Wi-Fi would be a "cash cow": Before the experiment, he struck a commercialization deal with a local Internet service provider, Lightspeed Broadband. But the deal didn't work out, and now Laine is focusing on potential applications for the military and emergency response teams.
"An ideal application would be for search and rescue, where a kid is lost in the forest, and you need to be able to get above the scene and coordinate a search-and-rescue team," Laine said. "I think we've got real value for that."
Laine is planning another test of high Wi-Fi late this year or early next year, assuming that the FAA gives its approval again. "We're purposely going to go back to this location with a redesigned system - redesigned such that we can handle some stronger winds," he said.
At the same time, LiftPort is working with Rutgers University and North Carolina State University on a future high-altitude test of its balloon-tether-robot system. For that experiment, the balloon platform would rise to an altitude of 3 miles (5 kilometers), far exceeding LiftPort's previous record of a mile (1.6 kilometers).
It's still a long way from the 62,000-mile (100,000-kilometer) stretch envisioned for the space elevator. And the idea of Wi-Fi in the sky is still a long way off for LiftPort, although other companies are pursuing the idea as well with somewhat bigger budgets.
Nevertheless, Laine is feeling good about the steps taken so far - and he's looking forward to the Space Elevator Games and other activities at the X Prize Cup in New Mexico later this month. "It's going to be like Woodstock for space, man," he told me.
On the other side of the coin, there's a lot of skepticism about whether space elevators could ever work, in the short run or the long run. One research paper, which has been circulating since early this year, says even carbon-nanotube tethers couldn't be made strong enough for a real-world, Earth-based space elevator.
Other questions have been raised about the concept's costs vs. benefits: Sending things to space may indeed be more economical once the elevator is up and running - but would that justify what's likely to be a huge infrastructure cost, plus the significant maintenance costs for a 62,000-mile-long ribbon to the sky?
Many of these technical and business questions are addressed in LiftPort's FAQ file as well as on other resources such as the Space Elevator Reference and the Space Elevator Blog. LiftPort's latest test demonstrates that, in any case, the space elevator effort will have its ups and downs. Will it ultimately get to the top? Register your opinion in our unscientific Live Vote and in the commentary section below.
