Inflatable Space Elevator, Eh

(Alternate post title: “Hey to James Nicoll”)

Via John Dupuis, our clever neighbors to the North has come up with a possible (partial) alternative to rockets:

“For decades, scientists have been grappling to find a more efficient means of getting payloads into space,” says Brendan Quine (right), professor of space physics and engineering in York’s Faculty of Science & Engineering, who is heading the project. A paper detailing the design was recently published in the journal Acta Astronautica; it is co-authored by York space engineering Professor George Zhu and graduate student Raj Seth.

“Rocketry is an extremely inefficient way of getting equipment into space,” Quine says. “In the initial stages of flight, you’re wasting an enormous amount of energy fighting gravity and atmospheric drag.”

Constructed from Kevlar, the free-standing structure would use pneumatically-inflated sections pressurized with lightweight gas such as hydrogen or helium, to actively stabilize itself and allow for flexibility. A series of platforms or pods, supported by the elevator, would be used to launch payloads into Earth’s orbit.

It’s a clever idea, and gets around a lot of the problems with the usual space elevator concept, such as the need for ultra-strong materials that don’t exist yet. It’s not without its limitations, though.

The biggest limitation is that the proposed structure doesn’t reach all the way to orbit, but only to a height of 20,000 meters or so (a bit more than 65,000 feet, for those who prefer American units). That’s enough to significantly reduce the need for rocketry (by getting above most of the atmosphere), but doesn’t eliminate it. In the paper, they work out the details of a launch from the platform, and find a significant increase in the fraction of weight given to payload over a launch from the surface.

Conspicuously absent from the paper is any discussion of the Hindenburg Scenario, namely, “what happens if your hydrogen-filled space elevator catches a spark?” OK, it’d probably need to leak first, and then spark, but still, that’s an awful lot of flammable gas. You might think it would merit a mention.

They propose a couple of other possible uses for such a structure, beyond the limited assist to orbit application. One of these is, of course, space tourism– 20,000 meters isn’t enough to get into free fall, but it’s high enough for most sightseeing purposes. Another, more prosaic, use would be as a sort of glorified cell phone tower, providing a high-altitude communications relay point.

It’s a nifty idea, though very much a preliminary proposal sort of thing. It’s also a kind of example of Twain’s famous comment about fiction needing to be more plausible than reality– there’s no problem for a science fiction author who wants to propose an all-the-way-to-space elevator system made of 90% pure unobtanium, but somebody writing a story featuring an inflatable 20km elevator tower would be laughed right out of Analog. Or would’ve been, before now…