Inflatable Tower Could Climb To the Edge of Space 296
MonkeyClicker writes with mention of a proposal that could see an inflatable tower helping to carry people to the edge of space without the need for rocket propulsion. This would function in place of previous space elevator designs which featured a large cable and could be completed much faster, if proponents of the project are to be believed. "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 tonnes when pressurized — around twice the weight of the world's largest supertanker."
Where will all the helium come from? (Score:5, Informative)
Their 15km version would need ten years of the entire world's helium production to fill it.
The 200km version would use up over half the world's estimated helium reserves.
Think of it as a railgun or catapult. (Score:4, Informative)
Note that this is would only extend a few tens of kilometers. It's to the edge of space, whereas a full elevator is aimed at getting *out* of Earth's gravity well.
Well if you just use it as a regular elevator and stop at the top, it's a nice tall observation deck where the atmosphere is really thin but not quite "into space".
But if it can support the weight of the elevator and observation platform, it should be able to provide an equal upward force to a lighter payload that is being accelerated. Such a projectile might leave the top of the structure with enough velocity to put the apogee of its trajectory in low-earth-orbit altitudes.
You'd have to provide additional thrust during that hop to bring the PERIGEE above significant atmospheric braking in less than half an orbit. But you've won half the battle by getting above the significant atmosphere on electric power rather than rocket reaction.
Perhaps lean the thing over to get significant downrange velocity - and support its less-vertical run with more compression members of a similar construction while building a broader structure of multiple members to avoid bending between supports. (Octagon truss, anyone?)
And the payload might also be composed of something like a long, thin, "cannon" with a "bullet" that is your final payload. "Fire" it (electromagnetically again) when near apogee. Then the "bullet" is circularized and the "cannon" returns to Earth for reuse with less momentum than when it left the elevator/catapult. Reenter and glide down - or land into another similar elevator structure and be gently lowered for reuse while the energy from the cannon stage's momentum and altitude is recycled into electric power.
Re:Not same as elevator (Score:5, Informative)
15km isn't that far out. You can still use oxygen-burning jets at that altitude if you design them right. The SR-71 went up to 24km. Amature high-altitude ballons can break 30km [natrium42.com] and might get out to 50km if they try hard enough.
If this thing can plausibly get out to 100-200km, they might have something, but 15km isn't very impressive for what it needs to do.
Re:Prior Art (Score:2, Informative)
Buckminster Fuller (my hero ;-) already came up with this, altho' he intended to use concrete. Basically, if the structure is large enough, making the inside of the structure a few degrees warmer than the outside air will cause it to float. Bucky described a sphere about 1 mile in diameter to be airborne, and somewhat smaller cones to be sea cities.
Later . . . Jim
Yeah, that'll go over like a lead balloon [youtube.com].
Re:Extra points ... (Score:4, Informative)
Balloon can only reach an elevation where it matches the buoyancy of the air. The article doesn't say, but I presume that the structure will be heavier than air. For that to work, you need something holding you up from the bottom, or a space elevator.
Re:Not same as elevator (Score:4, Informative)
Re:Not same as elevator (Score:5, Informative)
15 km high superstructure? Pretty good place to start if you are working on a space-elevator-thingy.
Not really. A space elevator works by having its center of gravity at the distance for geosynchronous orbit (or slightly beyond, once you've hooked to the ground). That's about 22,300 miles. To build it, you start at the geosynchronous orbit and start spooling material simultaneously towards the earth and away, so the center of mass remains geosynchronous.
15km isn't a drop in the bucket by that measure. At 15km above a fixed point on earth, you're nowhere close to orbital velocity, whereas if you can climb up to 22,300 miles, you're at orbital velocity. And if you climb higher and time it right, you get a slingshot start to go other places.
I'm not saying that a 15km tower couldn't have valid uses, but it's not going to unlock planetary travel for us.
Prof. Brendan Quine (Score:3, Informative)
Since it's not in the summary, Brendan Quine is an associate professor [yorku.ca] at in Space Engineering at York University in Toronto, Ontario (Canada). He is responsible for the Argus micro-spectrometer [yorku.ca] on the CanX-2 [utias-sfl.net] nanosatellite, currently operating on orbit. The satellite was developed by the University of Toronto's Space Flight Laboratory [utias-sfl.net].
Aikon-
Re:Yah... (Score:2, Informative)
Actually, would you believe 100 km? (Score:5, Informative)
There have been unofficial studies done of 100 km tall towers using "aerospace grade" materials. Balloon-tanks of extremely high-pressure gas made out of boron would be amazingly light but have staggering compressive strength. (You'd use lots of small ones to avoid ultra-high pressure in super-long columns.) There have also been studies of towers made form carbon fiber, aluminum, and steel. These have an exponential profile, and a "fractal truss" structure. Though huge, they'd me mostly empty space, to the point that most of the tower would be hard to see from the ground. The tubular beams would have teardrop-shaped fairings to minimize wind loads. The towers as a whole would be staggeringly heavy, but still *theoretically* possible to build, and *theoretically* affordable by superpowers like the United States. Will they ever happen in real life? No way. But engineers and physicists love thinking about this stuff and doing the calcs.
Re:Babel (Score:1, Informative)
There was still the war of tabs vs. two spaces. Lest we forget those who fell in righteous indentation!
Fixed that for ya