SIDECAR: How to Build a Space Elevator
It'll be the cheapest ticket to space. If it can be built. A Canadian firm says it's found a way.
Enter U.S. Patent #9085897. Granted earlier this year, it offers the specs for another “space elevator,” a soaring tower that will lift cargo and eventually, people up to a launch platform 20 km above the earth’s surface. The brainchild of Canadian technology firm Thoth Technology, it seems to offer a new take on an idea that’s more than a century old. The question is whether it can actually be built.
Urgent conversations about space travel usually involve two camps: enthusiasts and scientists. The first group “just wants to go to space,” says Dr. Bryan Laubscher, president of Odysseus Technologies LLC. “[They think], if scientists would just get their acts together, it will happen. [They think], ‘I’ve given them the idea, all they have to do is build it.’”
“…The first thing we hit upon was building up, rather than building down.”
For researchers in the field—Laubscher also spent time as an engineer at Lockheed Martin and a project leader at the Los Alamos National Laboratory—talk of “how” to build a space elevator has intensified in recent years. Until recently, those conversations have centred on a specific concept: a tether suspended from a satellite and anchored to a ground point would host climbing elevator cars carrying cargo or passengers. When researchers presented at the 2015 Space Elevator Conference in Seattle earlier this year, they discussed carbon nanotubes—one of the challenges of building a tether is finding material strong enough to withstand the weight of space-bound cargo—and tether dynamics.
Thoth Technology’s concept for the ThothX Tower is different, according to Brendan Quine, chief technical officer at the Pembroke, Ontario-based company. With so much focus on the tether model, “we started to think about what we could do that would be more practical—the first thing we hit upon was building up, rather than building down.”
Their plan revisits a very early notion for a tower that would take people or cargo to the stratosphere, with some 21st-century adjustments. “This Thoth tower is truer to Konstantin’s vision,” notes Geoff Nunn, adjunct curator for space history, at the Museum of Flight in Seattle. He’s referring to Russian scientist Konstantin Tsiolkovsky, who floated his own space tower plan in 1895. All of the concepts, whether they’re Tsiolkovsky’s “celestial castle,” Quine’s ThothX Tower or the popular tether, take rocket propulsion out of the equation.
Basically, if travellers start their space voyage halfway there, there’s less air resistance, and no need for a complicated –and costly—rocket launch. Lockheed Martin and the Boeing Company’s space travel joint venture, United Launch Alliance, puts the average cost of a rocket launch at $225 million U.S. A Thoth statement says the tower would cut the amount of a conventional launch by 30 per cent.
And the International Space Elevator Consortium, a group of like-minded researchers and industry partners, estimates that an elevator would cut the cost of sending cargo to space to mere dollars per kilogram, compared to the present cost of $20,000 U.S. per kilogram.
If the tether model envisions a thin ribbon stretching from space back down to earth, the ThothX Tower is more like “a space port on a stick,” says Nunn. The plan calls for
flexible, air or gas-pressurized “cells” to build the structure, which would house an elevator leading to a “pod” and launch platform where space planes would leave for the next phase of the journey.
Quine says the Thoth plans address the engineering issues that come with tall, freestanding structures. For one, how would something that high support its own weight?
He and his graduate students at York University’s Lessonde School of Engineering turned to air pressure for an answer. “For every square metre of the surface of the earth, the atmosphere is pressing down with 10,000 kilograms, or ten tonnes per square metre,” he says. “The force encapsulated in a tower-like structure would be enough to hold up the weight.”
It’s not the first tower to consider gas or air pressure. U.S. researcher Nelson Semino has also floated a similar idea with The SpaceShaft, which also uses hydrogen or helium gas-pressurized building blocks.
There’s some merit in the overall idea, according to Dr. Arun Misra, a professor in the department of mechanical engineering at McGill University. “There has been a lot of interest in applying these inflatable structures to space research,” he says, pointing to Bigelow Aerospace’s work on expandable space habitats for NASA. Work with inflatable satellite antennas has also made strides. Smaller satellites can’t handle the bulk of a traditional antenna, so researchers at the Massachusetts Institute of Technology came up with a Mylar-based one that unfurls and deploys to full size once the satellite has launched.
“We don’t need carbon nanotubes or fancy laboratory materials.”
Antennas or other inflatable structures like the Goodyear Blimp are one thing, but a 20 km structure literally takes the concept to the next level. A slender building like the Thoth design could have the potential to buckle, Misra points out. “You’d have to do a lot of detailed stress and dynamics calculations,” he says. “That, to my knowledge, hasn’t been done, at least not in open literature.”
Quine’s team has a solution for that, too. He concedes that guy wires or tethers won’t work. “They would be too long and heavy.” Instead, they took inspiration from human physiology. He notes that our spines are a type of control system that constantly makes adjustments so we don’t fall over. “We realized that that approach could be used to counter things like hurricane force winds.” By tilting the structure by just one degree, he says the tower could withstand a Category 5 hurricane.
Architect Frank Lloyd Wright once envisioned a skyscraper that reached a full mile into the sky, not a workable plan for the time, but “in the future no one can afford not to build it,” he said. To some extent, practicality has been the tether elevator’s main barrier. Work on the strength requirements and carbon nanotube structures is ongoing, but the Thoth plan eyes materials that are already available. “We don’t need carbon nanotubes or fancy laboratory materials,” says Quine. He points to materials like Kevlar 49 and fibreglass tanks that are already used in space and on the seas. “Yachtsmen use them in order to reduce the weight of propane cylinders.”
Can it work? At McGill, Misra says there are still too many unknowns to know for sure. “Right now, the concept looks very promising.” At the very least, the scale of the project seems more manageable, adds Nunn. “A 20 km tower versus a 100,000 km tether seems like a good first step.”
There are still a few missing factors, though. Quine acknowledges that the industrial capacity to manufacture the amounts of Kevlar and glass fibre technology is “lacking.” But he hopes that building a 1.5 km “demo” tower that will help test some of the tower’s capacity and kick start larger-scale industrial production. Though the shorter tower won’t be able to suss out some of the space launch capabilities, he says it will have other uses, like better wind power generation or communications.
And Quine says his company likely won’t be the ones to actually build either the demo or the full-scale tower. “Thoth is a technology company, not a construction company.” But he hopes the demo will be built within the next three to five years. As for the full scale tower, he’s set a timeline for six to ten years.
The right location—a park of at least nine square kilometres, or some other low-density area would work, he says. Though no specific place has been chosen, it seems fitting that his preferred site is the as-yet-to-be-built new capital city in Egypt. “It’s a new city, a new layout, and it would be possible to incorporate the tower,” he says, noting that the tower’s renewable energy capabilities also mesh well with the city’s early plans. “It’s a natural fit.”
Laubscher says the ThothX Tower likely won’t be the final word on the space elevator conversation. “We’re all interested in the next stepping stones to an elevator. I think this Thoth space elevator is a great step forward.”
He sees the concept as a potential partner for the eventual tether-based elevator, once it comes into being. One potential use: once researchers develop the right carbon nanotube strength for a tether that stretches for tens of thousands of miles, the Thoth concept could act as the base. “It could be the bottom node of a space elevator and that’s very exciting.”
The whole idea isn’t as futuristic as it sounds, points out Nunn. He notes that different U.S locations have been applying for spaceport licenses—earlier this year, Houston received Federal Aviation Administration (FAA) approval for a spaceport meant to develop aerospace projects and eventually send tourists into space.
And Quine is bullish on applications both in space and back on earth. The ThothX port will one day send visitors off to space, but shorter ports could one day be used for high speed flights between, say, Melbourne and New York, he points out. “We came at this from a space perspective, but are realizing other benefits.”
But the endgame is still space. Laubscher predicts that developing space elevators will pick up more momentum as demand grows. Eventually, “people are going to demand an elevator. This concept has been around for a long time. Any of these ideas that lower the cost of launch … that will revolutionize life here on earth.”
He considers the histories that have yet to be written, pointing to the impact the moon landing made in the 20th century. “I like to think about people writing about the history of the 21st century. They’ll say one of the best things we ever did was build a space elevator.”