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Inflatable Tower Could Climb To the Edge of Space
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."
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.
No sig today...
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 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.
Not a typewriter
Geosynchronous orbit has nothing to do with escape velocity. You'll always be a factor of sqrt(2) below escape velocity for any (circular) orbit.
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.
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.