A suspension of disbelief

Space elevators are inching their way up in feasibility

In the early 1980s, as a kid living on an island in the English Channel, I heard a rumour that someone was going to build an underwater tunnel linking England to France. “There’s no way that would ever happen!” I scoffed with seven-year-old certainty, and resumed reading Charlie and the Chocolate Factory. Twenty years later, I took the Eurostar train through the Chunnel from London to Paris, agog with delight that this seemingly unbelievable project had actually come to life.

Large-scale engineering projects like the Chunnel, that begin in absurdity and end in awe, are the beating heart of the space industry. Moving past initial titters into serious consideration is a major milestone for projects that dare to dream big. One such mega-project that is reaching this milestone is the Space Elevator. The recently released report Space Elevators: An Assessment of the Technological Feasibility and the Way Forward by the International Academy of Astronautics (IAA) has come to the conclusion that, “A space elevator appears feasible.” This slightly cautious-sounding statement is further tempered with “the realization that risks must be mitigated through technological progress.” Technical challenges notwithstanding, apparent feasibility is a big step up from laughter disguised as coughs coming from the back row of the space conference.

Space elevator nuts and bolts

Space elevators are based on the relatively simple concept of a mechanical climber crawling up a tether. For the space-bound, it’s a one week trip to geostationary (GEO) orbit, approximately 36,000 km away from earth. The tether itself would be initially constructed as a “seed ribbon” from space down, later strengthened by construction climbers. Balanced on a node structure in space, with a longer length extending past the node into space, the earth end would be linked to a Marine Node. The tension of the approximately 100,000 km long tether would be kept stable by the earth’s rotation. Imagine swinging a rope with a rock or other heavy object attached to one end, and then sliding a bead up and down the rope. The centrifugal force due to rotation keeps the line tight and the journey smooth. Much, much smoother, in fact, than a rocket ride.

Anything you can do I can do better

The IAA report emphasizes several major benefits of elevators over rockets in moving loads to space. One outstanding feature is the low cost involved. Rockets require fuel – a huge amount of it. So much, in fact, that over 90% of the weight of a current launch vehicle is comprised of fuel, vehicle structure and control equipment, most of which gets thrown away. Not only is this wildly expensive, putting launch costs at a price of $20,000 per kilogram but it contributes to environmental damage and the creation of space debris on a massive scale. Space Elevators, once the infrastructure is put into place, are estimated to lift with an average cost of $500 per kilogram, and run clean, utilizing solar energy and laser light.

In addition to the pricing and environmental benefits, elevators also have the potential to move much larger, heavier, and fragile freight, much more safely. The IAA report poetically describes shock loads ”equivalent to petals dropping into a pond instead of the explosive potential and violent rock and roll experienced during rocket lift off.”

That perfect material

Due to the extreme size of a tether to space, a traditional strong material such as steel could not be used, as it would rupture under its own weight. As a result, one of the biggest challenges facing the development of a feasible space elevator is in the arena of materials science. The most favorable material posited for a space tether at this time is carbon multi-walled nanotube. Carbon nanotubes resemble a tube-shaped roll of hexagonal chicken wire made of carbon. With a diameter on the nanoscale, and a length currently in centimetres, it is a material that is incredibly light yet strong. The challenge at this time is to grow longer carbon fibres in order to increase the strength-to-weight ratio by being able to twist the fibres together. Rice University in Texas has made great strides in the development of this particular material. A refinement and maturity of this particular materials technology is one of the necessary developments noted in the final assessment of the IAA report on feasibility.

A historical perspective on the future

The second part of the IAA report’s final assessment notes that, “A Space Elevator Infrastructure will be achievable through a major global enterprise.” To be successful, the project needs international support including legal, political, and financial backing.

The report asks the reader to imagine what the producers of technological mega-projects of the past must have had to accomplish, citing such examples as the installation of gas lamps in London, construction of the bridge between Denmark and Sweden, and yes, drilling the English Channel Tunnel. Reviewing similar past projects serves not only to grow technological understanding, but to help inspire projects of the future, encouraging a sympathetic and respectful view of research and development processes.

While the space elevator community is interested in looking at the history of other projects as models for development and inspiration, it is attempting at the same time to trace its own rich history. The International Space Elevator Consortium (ISEC) website notes that it has formed a History Committee to “document the invention of the concept of the Space Elevator and the ever-increasing research and design which is taking place related to this idea.” The initial committee has formed, and a self-described “aggressive agenda” is set to go. Requests to join or head up this history team can be made directly through Dr. Peter Swan, President of the ISEC and lead editor of the IAA report. Personally, I’d join just to get a sneak peek at the details of this curiously fierce research agenda.

In the lesser-known sequel story, Charlie and the Great Glass Elevator, young Charlie Bucket takes an unexpected ride to space in an elevator. When Willy Wonka is asked what keeps the elevator up, the mad factory owner and inventor replies “skyhooks.” Thanks to the work of the ISEC, that marvellous mad idea might not be so crazy after all.

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