Inflatable tower would bring people to the edge of space

We rely more on more on satellites of all types for both military and commercial purposes. As is the case with other machines, some of these space vehicles malfunction. When they do, we do not only lose their valuable services, but they may fall out of orbit and collide with other space assets. Trouble is, lofting crews from earth into space to fix satellites is an expensive proposition.

Jeff Hecht writes that there is an alternative. A giant inflatable tower could carry people to the edge of space without the need for a rocket, and could be completed much sooner than a cable-based space elevator, its proponents claim. Inflatable pneumatic modules already used in some spacecraft could be assembled into a 15-kilometer-high tower, say Brendan Quine, Raj Seth, and George Zhu at York University in Toronto, Canada, writing in the August-September 2009 issue of Acta Astronautica. If built from a suitable mountain top it could reach an altitude of around twenty kilometers, where it could be used for atmospheric research, tourism, telecoms — or for launching spacecraft.

The team envisages assembling the structure from a series of modules constructed from Kevlar-polyethylene composite tubes made rigid by inflating them with a lightweight gas such as helium. To test the idea, they built a 7-meter scale model made up of six modules. Each module was built out of three laminated polyethylene tubes eight centimeters in diameter, mounted around circular spacers and inflated with air.

To stay upright and withstand winds, full-scale structures would require gyroscopes and active stabilization systems in each module. The team modeled a 15-kilometer tower made up of 100 modules, each one 150 meters tall and 230 meters in diameter, built from inflatable tubes 2 meters across. Quine estimates it would weigh about 800,000 tons when pressurized — around twice the weight of the world’s largest supertanker.

“Twenty kilometers up is about as dark as outer space. You can see about 600 kilometers in any direction,” Quine says. Tourists could get a view almost like that from space, but without the difficulties of coping with zero gravity. He calculates the tower could be extended up to low Earth orbit at 200 kilometers.

There is another advantage to the tower idea. Yes, the tower does a similar job to the much-vaunted space elevator, but while the elevator envisages using ribbons woven from super strong nanotubes — a material which does not yet exist — the tower would use materials that are already available. Should something go wrong with the tower, failure of a few modules would not cause the whole structure to collapse.

-read more in B. M. Quine, R. K. Sethb, and Z. H. Zhua, “A Free-standing Space Elevator Structure: A Practical Alternative to the Space Tether,” Acta Astronautica 65, nos. 3-4 (August-September 2009): 365-75