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Electric Aviation Developments

  1. Jun 17, 2016 #1

    mheslep

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    NASA has press release out today highlighting its electric aviation program via a new 4-seat X plane to explore the concept, the X-57.

    Most interesting to me was this claim:

    which I imagine comes about by having a much large propulsive air flow area across the 14 e-motors, allowing the prop flow velocity to be much lower.

    Goal:
    That goal is interesting but ill-considered IMO, as range is the issue in electric aviation, not power.

    afrc2016-0065-32.jpg

    Video of fourteen motor wing under test

     
    Last edited: Jun 17, 2016
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  3. Jun 18, 2016 #2

    Baluncore

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    If you can do the same for 1/n of the power then you can do it for n times longer. That increases range by a factor n.
     
  4. Jun 18, 2016 #3

    FactChecker

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    That is one optional benefit. It also could allow you to loiter in place and observe for a long time, even if the cruse speed is decreased. It might even allow sustained solar-powered flight where the plane can stay up indefinitely.
     
  5. Jun 18, 2016 #4

    mheslep

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    Point taken.

    Aside: I don't see efforts at many-motor designs among RC electric aircraft hobbyists, or in the UAV arena. Perhaps cost is an issue, though since the RC's with their LiPos are quite range (time aloft) limited, say, 15 mins, there should be ample motivation to try. Edit: here's a competition for time aloft (traditional design) with a maximum of 26 mins.
     
    Last edited: Jun 18, 2016
  6. Jun 18, 2016 #5

    mheslep

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    Overnight unmanned electric flight was accomplished six years ago. http://tucson.com/business/local/tucson-firm-s-solar-batteries-power-record-flight-attempt/article_00ec5266-f412-5b3d-aaa5-04e9d87ec896.html [Broken]made by QinetiQ with Sion batteries flew non-stop for 14 days using PV: dual prop, 70 ft wingspan, 110 lbs. The term of art going forward is "solar powered atmospheric satellites"
    http://www.unmannedsystemstechnolog...for-solar-powered-atmospheric-satellite-uavs/
     
    Last edited by a moderator: May 8, 2017
  7. Jun 18, 2016 #6

    CWatters

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    Presumably the idea behind multiple motors and props is to increase the air flow over the wing meaning a smaller wing can be used?
     
  8. Jun 18, 2016 #7

    mheslep

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    I don't think so. There's some work on a design indicating lower turbulence with aft fuselage mounted engines thus reducing drag by positioning motors in places not practical with combustion engines.

    But as I understand it, the principal advantage of multiple motors is that they are theoretically more efficient than one at producing the same amount of total thrust. That is , thrust is proportional to both air velocity and the area through which the air is driven, but high velocity exit air is wasted kinetic energy in the atmosphere. Thus it is more efficient to achieve thrust by greater engine area when possible than by higher velocity air flow.
     
  9. Jun 18, 2016 #8

    FactChecker

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    The arrangement shown has a very high aspect ratio with very even airflow from the props over the wing. That should give an exceptional lift to drag ratio.
     
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