Aerovator, Angel fleet, Polywell

[ciphergoth]

Ideas that are currently entertaining me:

• The Aerovator: a spinning wing 2,000km long whose tips rise 100km up and travel at 8 km/s which unlike the Space Elevator can be built (just) with today's materials.
• The Angel fleet: Counteracting global warming with a fleet of 16 trillon solar shades in space between the Earth and the Sun (we can use the Aerovator to put them up)
• Polywell fusion which if it turned out to be possible would save the world - plus we can power the Aerovator with it.

Comments

[martling.livejournal.com]

> which unlike the Space Elevator can be built (just) with today's materials.

"Just" concerns me. If it's only just got the tensile strength required, then it should work in still air, but add in the weather and the resultant additional strains and subsequent oscillations on the wing, and you'll get tension peaks popping up all over the place.

With drive/drag systems distributed all along the wing you might be able to compensate for this to keep the loads evenly distributed, but that woudl add a whole lot of complexity to the structure.

However my main concern would be the ability to actually design a suitable wing. In most aircraft the limiting factor on airspeed, propulsion aside, is not the sheer force on the wings, but flutter: aerodynamic forces combined with elasticity in the structure leading to oscillation.

See here (http://www.youtube.com/watch?v=mxFOHoy-UNQ) for this occuring in practice in a flight test. The pilot increases the speed just enough to induce the flutter, then backs it off. If he took it too far, positive feedback would kick in and the wing would break up.

[ciphergoth.livejournal.com]

I wouldn't be surprised if this were the sort of problem that killed the idea - the guy who writes it has thought through issues about tensile strength etc but he's pretty open about his ignorance on complex matters of aerodynamics. Still, there's some hope that the sheer length of the wing would actually reduce the impact of problems like this, the way tall buildings are better at surviving earthquakes...

[martling.livejournal.com]

The high tension combined with the length does intuitively suggest a longer wavelength of oscillation, but I'm not sure if that means the forces involved will be any less severe.

One thing I do know is that subsonic, transonic and supersonic aerodynamics are three very different things, and that one of the big problems with designing supersonic aircraft is coming up with a shape that works for all three regimes. Whether you could accomplish all three with something that's basically just a ribbon, and be able to actually bootstrap the rotation, I have no idea, but it sounds tough.