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…

Comments

  1. #1 Ethan
    June 18, 2009

    Actually, there are stories where “aerostats” play a role. The details are usually vague, but they sound like much the same thing. I’m thinking of Poul Anderson’s “Orion Shall Rise” in particular, but there have been others.

    Granted none of these stories may have appeared in Analog.

  2. #2 Ethan
    June 18, 2009

    Actually, there are stories where “aerostats” play a role. The details are usually vague, but they sound like much the same thing. I’m thinking of Poul Anderson’s “Orion Shall Rise” in particular, but there have been others.

    Granted none of these stories may have appeared in Analog.

  3. #3 Uncle Al
    June 18, 2009

    Yer gonna set off a freak’n big rocket surrounded by pneumatic inflation? Riiight. Helium at sea level lifts one gram/liter. Helium at 20 km altitude is silly at face value. PV = energy, 101.325 J/liter-atm. Huge surface area mean huge permeation losses (virtual leak) or huge areal mass to contain the light gas. Ozone at the bottom, solar hard UV at the top. Organics disintegrate.

    If NASA had any brains (already sci-fi) it would launch from the planarized summit of Mt. Chimborazo, 6384.4 km from the Earth’s center, 6.2682 km altitude, and 01°28′09″S latitude. The difference in energy to orbit versus Cape Canaveral (6375.5 km from Earth’s center, 0.003 km altitude, and 28°27′20″N) is almost two Space Scuttle SSBs’ outputs for a fully laden and fueled Space Scuttle, plus air resistance difference. This derives from increased altitude above the geoid (gravitational potential energy, mgh) and increased net throw velocity (mv^2/2) vs. the fixed stars (given the local point’s circumference at its radius from Earth’s center, 23.934470 hours sideral day, then net (speed)[cosine(latitude]). Slightly lessened gee at the summit of Mt. Chimborazo for altitude is offset by the extra rock beneath.

    Dr. Schund has the solution! Air has avg. MW = 29, helium is MW = 4 for a 7:1 lift ratio. Hydrogen at MW = 2 is a 14:1 lift ratio. One need only fabricate a small vacuum chamber for a near-infinite lift ratio. That is why the vacuum of space is always up. Riiight.

  4. #4 peter
    June 18, 2009

    Ooooo… this brings up all sorts of nifty ideas: If one can get close enough to orbit then JP Aerospace’s nflatable Orbital ascender should get you the rest of the way: http://en.wikipedia.org/wiki/JP_Aerospace.

    They had envisioned a floating air-station with a two step process: earth -> station -> orbit
    which involved different types of lighter than air vehicle for different stages,but if the first stage was an inflatable space-elevator, then I bet the ascent time would be drastically reduced.

  5. #5 llewelly
    June 18, 2009

    For starters, paint it with conductive paint, but not with a mixture of iron oxide and aluminum oxide (which is what the Hindenburg was painted with).

  6. #6 Douglas
    June 18, 2009

    Holy Hindenburg, batman! Thermite paint??

  7. #7 fvngvs
    June 19, 2009

    The thing that passed through my mind (and is still there!) while reading this is…

    BASE jumping! Ya Hey!

    Eat yer heart out Kittinger!

  8. #8 Eamon
    June 19, 2009

    a bit more than 65,000 feet, for those who prefer American units

    American? Aaaamerican??

    Brittish! British (desu) ;)

    “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.

    Undt flammability vs. altitude might also be a point.

  9. #9 Wilson
    June 19, 2009

    Chad, if you’re going to invoke cultural stereotypes in your blog entry titles for humorous purposes, please respect the conventions. The ‘eh’ at the end of our sentences turns them into questions, and so requires a question mark.

    As written, the ‘eh’ connotes a feeling of dismissal: “Inflatable space elevator. Eh.” But turning it into a question, makes it an expression of interest: “Oh, an inflatable space elevator, eh?”

    Just saying.

    (Note that I’m not complaining about the fact that you did invoke the stereotype, even though doing so makes many of us roll our eyes. Just that it needs the question mark. But “Weird Al” did it best, anyway.)

  10. #10 Defiant Statement
    July 3, 2009

    Brendan Quine,one of the guys behind the idea, calculates the tower could be extended up to low Earth orbit at 200 kilometres, that is roughly 650,00O Imperial/English feet

  11. #11 Defiant Statement
    July 3, 2009

    This should be built at Ground Zero as a fitting tribute to those that suffered 9/11. It would initially not get so far into space, than if it was built on a mountaintop, but the views from 15km up would still be slightly stunning.

  12. #12 Jonathan Vos Post
    July 3, 2009

    I prefer to avoid the Hindenburg Scenario with a space elevator system made of 90% pure unobtanium and supported by a thin coating of Cavorite.

  13. #13 HootyTooty
    August 29, 2009

    Defiant Statement – Umm give it a rest. Unless you were being sarcastic.

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