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solar powered jet

a flying wing air plane with fresnel lens or parabol concentrate sun's light to a jet engine
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a large 100x100 meter flying wing would generate more than 10MW enough to keep the airplane flying at a high speed. Fresnel lenses in the transparent hull gives maximum design freedom, but a parabola would also work. Above the clouds there are 30% more sunlight and no clouds, enough to keep up the speed of the earth's rotation and become a virtual satellite. (see image)
janpeternordin, Apr 01 2013

image of jet http://4.bp.blogspo...03-29++08-42-34.jpg
sketch of flying wing with jet [janpeternordin, Apr 01 2013]

Reactor-derived heat for aircraft propulsion http://en.wikipedia..._Nuclear_Propulsion
[bs0u0155, Apr 01 2013]

Laser powered ramjet http://www.dtic.mil...text/u2/a442467.pdf
[Kansan101, Apr 01 2013]

Solar Impact http://www.thephuke...ss-the-us-38583.php
Transcontinental flight of solar aircraft. [whlanteigne, Apr 13 2013]

[link]






       I have no idea whether this would work, but it's a beautiful idea. [+]
pertinax, Apr 01 2013
  

       Welcome to the 'bakery, by the way.
pertinax, Apr 01 2013
  

       Your 100mx100m surface will intercept 10MW, but how are you converting that to usable energy? The current best research grade PV cells are only ~45% efficient, and they aren't on the market yet.   

       If you're going purely solar thermal, you could, in theory, approach the Carnot efficiency which is 86% based on the sun's temperature, but the competing requirements of aerodynamics and optics are going to keep you well below that, even before you account for the real world nature of the engine.   

       Not saying it's impossible, just run the number for something more like 3-4MW for that size wing, rather than 10.   

       And welcome to the bakery.
MechE, Apr 01 2013
  

       Nice idea! I'm not entirely clear how the jet is going to use the 10MW of focussed heat, though...   

       And, indeed, welcome to Care in the Community.
MaxwellBuchanan, Apr 01 2013
  

       "Fasten seat belts" light stays on above 30 degrees latitude, particularly in winter.
lurch, Apr 01 2013
  

       I like the idea of each wing doing double duty as a lens. I would like the hull opaque, if you don't mind, as my piloting regalia might attract comment from the unenlightened.   

       The mechanics of it: one could make a hunk of stuff very hot with a big Frensel lens. I am less clear on how one could make that hot hunk of stuff generate directional thrust. Hot air will surely shoot out the back. But it seems to me that getting cold air into the front of the hot hunk would be difficult. Would a ramjet style thing work? Fuel combustion seems to me directional in a way that conductive heating is not.
bungston, Apr 01 2013
  

       The best I can come up with for simple heating is pulsejet. I suppose you could always use an PV electric compressor fan.
MechE, Apr 01 2013
  

       I'm thinking this type of concept wants to lean closer to an assisted lighter-than-air type of craft, or perhaps an almost-lighter-than-air craft.
RayfordSteele, Apr 01 2013
  

       I think it would be nearly impossible to orient the wing correctly for both horizontal flight and energy capture except at the one place on Earth where the sun is directly overhead.
Kansan101, Apr 01 2013
  

       So if you have a flying wing, with a transparent/fresnel lens upper surface, you've got to get your focused radiation to one or two spots. Common sense dictates that you want your jet engines in the centre, so you've got to get the energy there.   

       Now, the engines I can see working, standard jet engines more or less with the energy coming from sunlight rather than burning kerosene. You'd have to get the light in via some form of super-tough window, diamond or whatever, but after that it's doable. Nuclear aircraft have been designed and tested, and all their engines did was inject heat at the right point.   

       The difficulty is going to come in non-lossy optics and the angles you have to play with. Put simply, you'll need some pretty convoluted optics to get your radiation where it's going without having a prohibitively thick wing. You're also not going to have very much interior space.... there will be wave guides filling the wing.   

       How about a flying wing with a large parabolic collector in the centre.... using focused sunlight from a huge orbital mirror? The mirror could track the aircraft.
bs0u0155, Apr 01 2013
  

       Perhaps Fresnel lenses focusing on a great many vacuum-insulated liquid sodium tubes?
bs0u0155, Apr 01 2013
  

       Here's how I would build it, assuming that the plane could be restricted to flying at noon with the sun straight overhead:   

       The wing would be a Fresnel lens. The engine would be slightly below the wing, mounted forward of the center. The focusing light would strike a parallel flat mirror positioned halfway between the wing and the focal point. The beam would be reflected upwards, where it would focus at the center of the wing. A convex mirror at the center of the wing would reflect directly into the rear of a ramjet, where mirrored surfaces would direct the light to the center of the engine where the air needs to be heated, where all the surfaces would be black.   

       Link to laser powered ramjet that NASA built.
Kansan101, Apr 01 2013
  

       Link to Solar Impact, Swiss-made solar-powered airplane.
whlanteigne, Apr 13 2013
  
      
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