I Love Blimps
Idea: hot-air dirigible whose upper surface is a solar concentrator focusing at the center of the long axis. Axis is a tube penetrating and separate from the lifting chamber, with openings front and back, as well as inlet tubes along the sides. Sun heats the air in the balloon, causing lift. Simultaneously, it superheats the air in the inner tube, which expels out either the front or back, depending on the positions of various flaps, gates, or valves. A turbine placed in the flow path provides electricity for onboard systems.
It would be huge, and has an obvious limitation of daytime only, unless a supplemental heat source is included. Hot air instead of helium/hydrogen so no special tanking or materials required. Side inlets also provide steering. It would look boss. I’m guessing it would be pretty slow. Upside, unlimited operation as long as the sun shines and the fabric holds out. Maybe a retractable insulated topside blanket to extend night utility.
Is there enough energy in sunlight to make this work? What balloon shape would maximize solar exposure and minimize drag? Would it be better just to have the turbine generate power for standard propellers? Less cool, but better? Probably need internal lens/mirror to regulate lift/propulsion sunlight distribution.
UPDATE: I don’t know if this picture i’m about to post will show up, or if it will make any sense. But Bryce requested it, so what the hey.
Okay, I don’t know how to point to a pic on Flickr to make it show up here. Watch this space.
July 11th, 2008 at 8:05 pm
Dude, sounds like a winner to me. Balloon maybe should be delta/wing shaped to maximize surface and lift..or would that make heating uneven/more difficult. On the other hand, wing shape with multiple tubes makes for a built in steerage engine.
July 11th, 2008 at 9:25 pm
It’s not unworkable, but once you heat the air, you have to replace it with cool air, perhaps by using more forward motion. This suggests that multiple tubes would be necessary. For bonus points (or maybe redemption points), this is a similar operational principle to a ramjet.
July 11th, 2008 at 11:07 pm
Hot air moves backward or forward, depending on which door is open. The moving air causes a Venturi effect on the inner surface which lowers the air pressure at the inner end of the inlet tubes. The inlet tubes have 1-way flappers on them, so air can only go in, not out. The pressure differential provides the driving force.
So, it’s not in-front out-back, it’s in-sides out-back. It should work starting from a dead stop this way, unlike a ramjet. Although, maybe the front and back could be rigged to only allow flow one direction at a time. Simpler construction.
Funny thought: technically, it wouldn’t be powered flight. I wonder if the FAA would have any jurisdiction?
July 12th, 2008 at 9:33 am
… I would ask that you start including pictures, whether those pictures are drawn on napkins, in Photoshop, or even with that devil MS Paint.
That said, I think I have a better grasp of your description. So the central tube has smaller tubes, perhaps attached axially, leading from the outside to the center, and that is where the air gets replaced. I’m getting a feeling of diminishing returns, though, because I’m not convinced low air pressure X can give way to high air pressure Y strongly enough for the reverse to also occur.
July 15th, 2008 at 7:23 pm
Just upload through WP.