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Thread: Solar aeroplane top speed at high altitude.

  1. #196
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    Smile Re: Solar aeroplane top speed at high altitude.

    Finally we agree...hopefully those will appear in the next decade or so.

  2. #197
    Registered User Birdman100's Avatar
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    Re: Solar aeroplane top speed at high altitude.

    Finally we agree...hopefully those will appear in the next decade or so.
    Hopefully... they will appear, circling above the Arctic, with 100+% efficient side solar panels.

    Decade or so!? Bjahhh Earlier! Surely someone from Boeing or Airbus reads this.

    With inventive people like you, we are tranquil about the energy crisis.

  3. #198
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    Re: Solar aeroplane top speed at high altitude.

    Sometime back the calculation of speed being independent of wing area (power in equals power out both proportional to area) was made and a 'characteristic speed' (my term) dependent only on solar cell efficiency was found (ca 73 mph ) --it then went on 'neglecting induced drag etc..) -- of course for minimum power speed induced drag equals 3/4 of the total and for max range speed equals 1/2 so that the determined speed will no longer be valid by a long shot (divide by 1.4 at least but that is off the cuff ) it seems not to be taken into account that as you scale up anything the weight increases as the cube but the cross section only as the square so that structural efficiency declines rapidly (or weight goes up and starts a viscious circle) -- you can see this for a typical two seater versus a single seater -- not only do you need more spar material for example but the span must be greater to preserve a similar performance so that the thicker spar must also be longer and then it has to be increased to support itself with more wing area etc --just as longer bridge experiences more loads than a shorter one and has to bridge a greater gap as well. Efforts to make two seat Man Powered Aircraft (closest comparison to a solar powered one ) proved to be dismal failures -- the very name of one "Toucan' was a play on words 'if one cannot maybe twocan' --the only possibly serious contender with multiple seats was by well known gliding expert Nicholas Goodhart who proposed a cross channel multisetar rather like the much later Mac Cready Helios --with pilots in separate pods spread along a 200 plus foot span to avoid the growing structural problem (and being unable to turn at all ) --THAT,and that alone, MIGHT just come within a bull's roar of the sort of aircraft being discussed --and wetted area is the key rather than frontal area --and then it is turbulent wetted area that counts.

  4. #199
    Registered User danmoser's Avatar
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    Re: Solar aeroplane top speed at high altitude.

    Aircar,

    The topic question was about the upper speed limit of a vaguely described solar-powered airplane.
    The simplifying assumption of neglecting induced drag is adequate for that purpose only.

    At maximum level airspeed, induced drag can be a very small factor.

    Power to overcome induced drag is inversely proportional to velocity, so at the aircraft's minimum stall speed, the situation is reversed, and parasitic drag becomes the minor factor.

    This explanation may be helpful.
    Parasitic drag - Wikipedia, the free encyclopedia

    BTW, power to overcome parasitic drag is proportional to the cube of velocity. (Power = Force times velocity)

    Obviously, induced drag must be considered when estimating the performance of an actual airplane design over its full speed range, but the question presented was only about maximum speed of a solar powered airplane concept and relevant governing equations.
    Last edited by danmoser; December 27th, 2013 at 12:21 AM. Reason: clarification
    Doggzilla likes this.

  5. #200
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    Re: Solar aeroplane top speed at high altitude.

    I agree Dan...and when I looked closer the USA Today density chart I can see that the speed of sound can be reached at 20 km / FL650 and mach 2 or 3 at 25 km ( FL750 ). Being actually nowhere near the sonic boom..due to low compression. As I gave you the earlier design 50 seater gekko long time ago and this new craft being 100-200 seater..it could carry a huge rocket..big enough to make manned commercial moon flights possible at very low cost !

  6. #201
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    Re: Solar aeroplane top speed at high altitude.


  7. #202
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    Re: Solar aeroplane top speed at high altitude.

    Aircar..the inner passenger hull being connected to the extremely volumetric but slim lifting body and the wings attached to that makes this extremely light...actual wing panel being just 28 metres ! The 6000 kg empty weight is doable in plus minus 500 kg margin.

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    Cool Re: Solar aeroplane top speed at high altitude.

    This will then beat Cassini-Huygens with a great margin !
    Attached Thumbnails Attached Thumbnails Solar aeroplane top speed at high altitude.-tinman2.jpg  

  9. #204
    Registered User ultralajt's Avatar
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    Re: Solar aeroplane top speed at high altitude.

    Yes, with a great margin, as "Everythig he can do, you can do better....."
    ____________________
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  10. #205
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    Post Re: Solar aeroplane top speed at high altitude.

    We can't stop to the moon...we have to go deeper into the space ! With a reusable ship launched from FL750-FL800 altitude at Mach 3-4 equivalent speed. Mitja wouldn't it be great to have some one travelled to IO for instance and cometh back with some specimen from there ?

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    Re: Solar aeroplane top speed at high altitude.

    Cassini Io looks a bit hostile; Io (moon) - Wikipedia, the free encyclopedia Any other suggestions ?

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    Re: Solar aeroplane top speed at high altitude.

    There would be water on Europa; Europa (moon) - Wikipedia, the free encyclopedia

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    Re: Solar aeroplane top speed at high altitude.

    Cassini You have to remember Cassin-Huygens used most of the propellant to reach 68 000 km/h speed on take off !

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    Re: Solar aeroplane top speed at high altitude.


  15. #210
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    Re: Solar aeroplane top speed at high altitude.

    It would take just one day to get there..incredible..you could go there on an extended weekend..into Jupiter and back...kewl or what ?!

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