1669: Planespotting

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Copper Bezel
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Re: 1669: Planespotting

Postby Copper Bezel » Tue Apr 19, 2016 9:08 pm UTC

ps.02 wrote:I love these forum posts trying to explain in detail why the idea to use hydro power to lift a tank of water thousands of times its own dam height is actually not scientifically feasible. In case anyone here was in danger of taking it seriously.

Well, the question was something like "I know it doesn't work, but I can't figure out the math to prove it for all cases." And it wasn't about the reservoir lifting itself, which is certainly simpler to understand.
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Re: 1669: Planespotting

Postby Eternal Density » Tue Apr 19, 2016 10:15 pm UTC

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Re: 1669: Planespotting

Postby Soupspoon » Tue Apr 19, 2016 10:29 pm UTC

I saw this - in an otherwise clear blue sky, at standard cruising altitude, today - and took an opportunistic picture1... Not actually anything to do with this thread/comic, but it just occurred to me to share it, rather than let it sit unused and unloved upon a memory card for the foreseeable future.

Image
Spoiler:
IFO.PNG
IFO.PNG (104.36 KiB) Viewed 3009 times

Too easy? Well, I reckon the basic model isn't that much in doubt.

(What's that site that you can look up global commercial aircraft movements on? I could probably narrow it down to an actual flight, if my camera clock isn't too far wrong...)



1 It's a quite old camera, only my 'carry around just in case' one. Only a 10x maximum optical zoom was available, and then I also cropped the whole massive image down quite a bit to just the rough area of interest. But at least I refrained from any digital zooming/interpolation along the way, so you've exactly the best detail I could give, without my having switched to a RAW format at the time (was stored as .jpg, but copied into .png so as not to add a second, shifted, set of JPEG artefacts). The sun was pretty much dead ahead of the aircraft, as you can see from the nose-glint; but still very slightly to the left, and above the flight-path too, as you can see from the tailplane shadows on the mind control gas contrails.)

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Soup
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Re: 1669: Planespotting

Postby Soup » Tue Apr 19, 2016 11:19 pm UTC

pixeldigger wrote:It appears to actually be a Bombardier Dash 8 Q400

Image

I shared this comic and speculation with a friend who's aware of, but not an xkcd regular, and also "one of those people..." and got this response:

Not much to go on, but based on the position of the elevator on top of the rudder, the shape of the wings, the position of the engine nacelles, and general length and shape, I would have to concur.


That's as good as authoritative for me!

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Spoiler:
I'm also sending him a link to this thread, in case he cares to register and take a bow :mrgreen:
Waiting for it...

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Re: 1669: Planespotting

Postby pixeldigger » Wed Apr 20, 2016 10:35 am UTC

Soup wrote:
pixeldigger wrote:It appears to actually be a Bombardier Dash 8 Q400


I shared this comic and speculation with a friend who's aware of, but not an xkcd regular, and also "one of those people..." and got this response:

Not much to go on, but based on the position of the elevator on top of the rudder, the shape of the wings, the position of the engine nacelles, and general length and shape, I would have to concur.


That's as good as authoritative for me!


does that qualify me as "one of those people..." as well ??? :mrgreen:

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DennyMo
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Re: 1669: Planespotting

Postby DennyMo » Wed Apr 20, 2016 1:25 pm UTC

My first thought when looking at the silhouette was that it kinda looked like a U-2.

Sadly, the attached ID card is of no help.
Attachments
US Military Aircraft Identification Training.pdf
(69.87 KiB) Downloaded 73 times

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orthogon
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Re: 1669: Planespotting

Postby orthogon » Thu Apr 21, 2016 12:21 pm UTC

Here's a few more for you planespotters out there:
Spoiler:
Image

Spoiler:
Image

Spoiler:
r.k=0
xtifr wrote:... and orthogon merely sounds undecided.

pscottdv
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Re: 1669: Planespotting

Postby pscottdv » Thu Apr 21, 2016 12:28 pm UTC

Caesar wrote:Ehm, shouldn't it be "...one of those people who know..."?


Who knows?

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Re: 1669: Planespotting

Postby pscottdv » Thu Apr 21, 2016 12:44 pm UTC

ps.02 wrote:I love these forum posts trying to explain in detail why the idea to use hydro power to lift a tank of water thousands of times its own dam height is actually not scientifically feasible. In case anyone here was in danger of taking it seriously.


I think they are trying to be like Randall and his "What If?" articles. I don't think anyone is really considering eating the sun either, but that doesn't stop Randall from writing about it.

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orthogon
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Re: 1669: Planespotting

Postby orthogon » Thu Apr 21, 2016 3:08 pm UTC

pscottdv wrote:
ps.02 wrote:I love these forum posts trying to explain in detail why the idea to use hydro power to lift a tank of water thousands of times its own dam height is actually not scientifically feasible. In case anyone here was in danger of taking it seriously.


I think they are trying to be like Randall and his "What If?" articles. I don't think anyone is really considering eating the sun either, but that doesn't stop Randall from writing about it.

There are quite a lot of ingenious designs for perpetual motion machines, some of which require significant effort to explain why they wouldn't work. The explanation needs to tackle the proponent's argument head-on, showing exactly where the flaw is, since otherwise you just end up "firing past one another". My personal favourite is the expanded polystyrene wheel half-in and half-out of a tank of water (with low-friction watertight seals where it enters the water). Clearly the centre of buoyancy is somewhere on the wet side, so the (vertical) buoyancy force exerts a torque on the wheel.
xtifr wrote:... and orthogon merely sounds undecided.

pixeldigger
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Re: 1669: Planespotting

Postby pixeldigger » Mon Apr 25, 2016 4:39 pm UTC

orthogon wrote:Here's a few more for you planespotters out there:
Spoiler:
Image

Spoiler:
Image

Spoiler:
r.k=0


you forgot these planes

Spoiler:
.
.
Inclined, wrapped around cylinders

Image

gimmespamnow
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Re: 1669: Planespotting

Postby gimmespamnow » Mon Apr 25, 2016 9:08 pm UTC

GrapeDrank wrote:I really only have a layman's understanding of physics and engineering in general, but in the event that the engines fail, wouldn't an airplane with the hydroelectric system be able to generate power by gliding upward? Or downward for that matter? Or even just turning? A gliding plane with engine failure could sacrifice altitude for power to keep in radio contact, etc etc.

Not water, but many planes do have a wind turbine installed in case of engine failure, while allows them to trade airspeed, (if you aim the plane down it will go faster,) for power to run the radio/control the flaps/etc: https://en.wikipedia.org/wiki/Ram_air_turbine Of course, complete engine failure is rare on large planes, (with the obvious except of running out of fuel.)


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