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JP Aerospace and rotating sun toy



 
 
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  #1  
Old May 9th 04, 05:52 AM
Vincent Cate
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Default JP Aerospace and rotating sun toy

I note that the first airship pictured at:

http://www.hobbyspace.com/AAdmin/arc...alAirship.html

it looks like a dark blue in the front part of the V and then silver
in the 2 back parts. On my shelf next to my desk I have one of
these toys that spins in sunlight. Probably most people are
familiar with it, there are 4 little plates that are black on
one side and white on the other that spin in a glass bulb with
a partial vacuum. So I wondered if this is related to the JP Aerospace
propulsion system. My toy moves away from the black side.
Basically molecules bounce away faster from the hotter black
side and so push on it more.

But this would push the airship backwards as it is colored now.
So this does not seem to be it, unless the builder got things
backwards.

Still, this force seems like it could be some fun for airships
at high altitudes. Imagine a single cylinder shaped airship
that is black in the back half and white in the front half,
with something inside separating the two halves.
Imagine that it is moving perpendicular to the sun and rolling
like a rotisserie to even out the heat. So the back half
that is black would be hotter and would have a net thrust.
Anyone know how to calculate this thrust?

-- Vince
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  #2  
Old May 9th 04, 08:49 PM
Karl Hallowell
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Default JP Aerospace and rotating sun toy

On Sat, 08 May 2004 21:52:04 -0700, Vincent Cate wrote:

snip

Still, this force seems like it could be some fun for airships at high
altitudes. Imagine a single cylinder shaped airship that is black in
the back half and white in the front half, with something inside
separating the two halves. Imagine that it is moving perpendicular to
the sun and rolling like a rotisserie to even out the heat. So the back
half that is black would be hotter and would have a net thrust. Anyone
know how to calculate this thrust?


All I know is that it's miniscule. The dark colored surface absorbs more
energy from the light source and thus heats the adjacent air layers a bit
more than the white colored side does. When the air on the black side
rises and is replaced by cooler air, I believe that generates a net force
on the plate pushing against it. IMHO, most of the heat probably is
reflected or radiated out though and doesn't contribute to the motion of
the system.


Karl Hallowell

  #3  
Old May 10th 04, 06:34 AM
Vincent Cate
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Posts: n/a
Default JP Aerospace and rotating sun toy

The toy is called a Radiometer and the effect is the
"radiometric effect". You can see a picture of one at:
http://store.yahoo.com/explo/radiometer.html

The rest is some notes I made about URLs I found with google.

- Vince

http://www.globalwarmingsolutions.co...otheoscope.htm
several orders of magnitude greater than solar sail force
10E-3 to 10E-4 atmospheres

"Reynolds and Maxwell proposed an explanation involving
'thermal transpiration' but even today there is still no complete
explanation of how this little toy works."

"There has been no attempt to harness the rotational energy to
measure the efficiency of conversion but I suspect that solar
is converted into rotational energy with very high efficiency
in the radiometer."

http://www.betrisey.ch/presbok11.htm
"The mechanism by which it operates is very complex and
frequently stated incorrectly."
Experiments seem to indicate "thermal transpiration" is at least
most of what is going on.

http://students.cec.wustl.edu/~sapph...adiometer.html
AMSAT people used radiometric effect to induce 1/2 rpm in 3 weeks
time

http://eotvos.dm.unipi.it/nobili/ope...r_PRD_2001.pdf
Left side of page 2 has formula for "radiometric effect" given
temp, pressure, ...

http://eotvos.dm.unipi.it/nobili/ope...pe_revised.pdf
Has formula

http://science.howstuffworks.com/question239.htm
Crookes' radiometer

http://math.ucr.edu/home/baez/physic...ight-mill.html
Thermal transpiration / light-mill
Thrust comes at the edges - discounts many other explanations

http://sargentwelch.com/product.asp?pn=WL1734%5FEA
$10 - 99% evacuated - gas expands on black side and so pushes
This looks like the one I have

http://scientificsonline.com/product.asp_Q_pn_E_3116000
Hand made radiometers.
"Energy is released as the heated molecules kick away at great
speeds, causing the vanes to revolve within the vacuum."
  #4  
Old May 29th 04, 01:49 PM
sanman
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Posts: n/a
Default JP Aerospace and rotating sun toy

(Vincent Cate) wrote in message . com...
I note that the first airship pictured at:

http://www.hobbyspace.com/AAdmin/arc...alAirship.html

it looks like a dark blue in the front part of the V and then silver
in the 2 back parts. On my shelf next to my desk I have one of
these toys that spins in sunlight. Probably most people are
familiar with it, there are 4 little plates that are black on
one side and white on the other that spin in a glass bulb with
a partial vacuum. So I wondered if this is related to the JP Aerospace
propulsion system. My toy moves away from the black side.
Basically molecules bounce away faster from the hotter black
side and so push on it more.

But this would push the airship backwards as it is colored now.
So this does not seem to be it, unless the builder got things
backwards.

Still, this force seems like it could be some fun for airships
at high altitudes. Imagine a single cylinder shaped airship
that is black in the back half and white in the front half,
with something inside separating the two halves.
Imagine that it is moving perpendicular to the sun and rolling
like a rotisserie to even out the heat. So the back half
that is black would be hotter and would have a net thrust.
Anyone know how to calculate this thrust?

-- Vince


Would there be any way to create a "nano-radiometric" effect, by
covering the surface of an object (eg. airship) with many nano-sized
radiometric structures?
Suppose you had a surface covered in a nano-sized sawtooth pattern,
with the front slope of each sawtooth reflecting more light and the
vertical backside of each sawtooth that absorbed more light. Could
this generate a net thrust in the rearward direction, to propel an
object forward? Comments?
 




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