Author Topic: Gardum's thread  (Read 3611 times)

Offline raven

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Re: Gardum's thread
« Reply #135 on: September 16, 2017, 02:05:58 PM »
It's not a carburetor filter; it's a banana clip.

https://www.amazon.com/Standard-Banana-Clip-Indispensable-Basic/dp/B00DQD3REE
Valuable info for cosplayers everywhere. :)

Offline AtomicDog

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"There is no belief, however foolish, that will not gather its faithful adherents who will defend it to the death." - Isaac Asimov

Offline Geordie

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Re: Gardum's thread
« Reply #137 on: September 16, 2017, 05:42:51 PM »
Now you're getting into my territory, or my name isn't....

AtomicDog!
How 'bout some extravehicular activity?
« Last Edit: September 16, 2017, 05:57:26 PM by Geordie »
.           She's on fire\  And she burns through the night at the speed of light\
             She's on fire\  With the heat of the beat right beneath her feet\
              She's on fire\  And the name of the game is to fuel her flame\
               She's on fire, fire, fire, fire, fire!

Offline gillianren

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Re: Gardum's thread
« Reply #138 on: September 17, 2017, 12:49:19 PM »
It's not a carburetor filter; it's a banana clip.

https://www.amazon.com/Standard-Banana-Clip-Indispensable-Basic/dp/B00DQD3REE
Valuable info for cosplayers everywhere. :)
 

Somewhere, I even have primary evidence for this; it's specified on one of the "making of" specials.
"This sounds like a job for Bipolar Bear . . . but I just can't seem to get out of bed!"

"Conspiracy theories are an irresistible labour-saving device in the face of complexity."  --Henry Louis Gates

Offline raven

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Re: Gardum's thread
« Reply #139 on: September 17, 2017, 01:44:15 PM »
It's not a carburetor filter; it's a banana clip.

https://www.amazon.com/Standard-Banana-Clip-Indispensable-Basic/dp/B00DQD3REE
Valuable info for cosplayers everywhere. :)
 

Somewhere, I even have primary evidence for this; it's specified on one of the "making of" specials.
Oh, I believe you. I'm pretty sure I heard it too.

Offline Zakalwe

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Re: Gardum's thread
« Reply #140 on: September 17, 2017, 04:12:40 PM »
You don't see that "children that pick on line breaks or grammar" is saying you're childish for noticing?  Okay.

So that makes at least two people at this board who seem to be incapable of distinguishing between noticing something and picking on someone for something, and one of them claims to have worked as a proofreader.

And IMHO, you make at least one person who seems to be incapable of making a cognitive connection between two variations of a common idea that everyone I know understands succinctly.  But that must be because you are so much smarter than everyone else, and certainly aren't childish in your own way to argue about it.

(sarcasm mode off)
Gardum's message was VERY clear, especially in context with the vaguery of everything else he/she wrote.  Your attempt to make it an issue about fairness and honesty has actually been an example of unfair, dishonest obfuscation.  Your arguments on this subject (again, IMHO) are empty, pointless and nonsensical.  What is your real agenda?

Its an example of sealion posting.

"Quod gratis asseritur, gratis negatur"
“That which can be asserted without evidence, can be dismissed without evidence.” – Christopher Hitchens.

Offline Geordie

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Re: Gardum's thread
« Reply #141 on: September 17, 2017, 04:19:14 PM »
It's not a carburetor filter; it's a banana clip.

https://www.amazon.com/Standard-Banana-Clip-Indispensable-Basic/dp/B00DQD3REE
Valuable info for cosplayers everywhere. :)
 

Somewhere, I even have primary evidence for this; it's specified on one of the "making of" specials.
Very interesting. I'd love to craft such eyewear. When TNG first aired, I was delighted to see Laforge's first name, and, forgetting that most people are not as nerdy as myself, I thought it would result in people in general suddenly knowing how to spell my name.
.           She's on fire\  And she burns through the night at the speed of light\
             She's on fire\  With the heat of the beat right beneath her feet\
              She's on fire\  And the name of the game is to fuel her flame\
               She's on fire, fire, fire, fire, fire!

Offline ka9q

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Re: Gardum's thread
« Reply #142 on: September 18, 2017, 04:12:12 PM »
I would have made my own about SPECIAL Film from Kodak with a melting point of 250C with no links to this of course as Kodak sent our photographic club the stats for the film at the time and it was nothing close.
The material in question is ESTAR (Kodak trademark), more specifically polyethylene terephthalate (PET), a member of the class of plastics known as polyesters. Although it was fairly new during the Apollo program, it eventually became widespread in commercially available film stock, replacing the weaker and less stable cellulose acetate (which in turn replaced the highly flammable and unstable cellulose nitrate). The Wikipedia entry for PET gives its melting point as "greater than 250 C".

You may be more familiar with it as the stuff plastic soda bottles are made from.

So if you don't believe the references, there's nothing to stop you from getting some and making your own measurements.


Offline ka9q

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Re: Gardum's thread
« Reply #143 on: September 18, 2017, 04:23:27 PM »
Which is why the Estar base was made.  Kodak was tasked with creating a film that would work in a vacuum precisely because that was the requirement.
I'm sure Estar's other properties were important for the Apollo application, but I think a big one was simply its high mechanical strength. NASA wanted to cram as many exposures as possible into each film magazine, and that meant making the film base as thin as possible. Acetate simply wouldn't have been strong enough.

Estar's strength is actually a disadvantage for movie prints -- a jam can damage a projector instead of snapping the film, which can usually be spliced.

(Reminds me of the sardonic report among electronic engineers and repair technicians that "a transistor blew to protect the fuse".)

Offline ka9q

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Re: Gardum's thread
« Reply #144 on: September 18, 2017, 04:48:02 PM »
Take a Hasselblad camera out on an EVA of 4 hours, and this would suggest that, if it had the same reflectivity as the lunar surface, it's outer casing would heat up by 8 degrees. In fact, it was designed to be more reflective, and hence it would accept less heat than this.
Optical (visible light) reflectivity isn't the only important property. Its behavior at far infrared wavelengths is also important, as is its thermal mass.

Objects in thermal equilibrium with sunlight at our distance from the sun do not get anywhere near hot enough to emit significant visible light, or even near infrared light (the two bands where the sun radiates most of its power). Peak radiation occurs in the far infrared spectrum around 10 microns, where objects can "look" very different than in the visible. (Passive IR motion detectors also work in this region, detecting people by their own thermal emissions.)

A material that appears optically dark to our eyes might be highly reflective in the far IR, and vice versa.

A material that looks bright in the far IR will also be a poor radiator of heat at those same wavelengths, so a material that appears (relatively) dark to our eyes but bright in the far IR will get very hot in sunlight. Examples include metallic gold. It appears yellow because it absorbs blue light, unlike most metals, but like most metals it appears reflective in the far IR, so it radiates poorly.

Conversely a material that looks reflective to us but dark in the far IR will remain quite cool even in direct sunlight; examples include "second surface mirrors" such as thin films of Teflon, Kapton or Mylar with aluminum on their rear surfaces. Kapton and Mylar are (mostly) transparent to visible and near IR radiation but opaque in the far IR, where they radiate well. They're commonly used on the surfaces of thermal radiators, like those inside the Shuttle payload bay doors.

What's crucial is the balance between the visible and far IR properties. Polished aluminum metal (without a film coating) will still get very hot in the sun even though it reflects sunlight well because it's even brighter in the far IR than in the visible. In other words, you can't tell how hot the material will get by just looking at it; you also need to know how it looks in the far IR.

This is fundamental to spacecraft thermal engineering. Because they can only exchange heat with the outside world by means of radiation, various optical coatings and blankets are used as needed to keep the equilibrium temperatures close to the design values.

The Apollo lunar surface cameras were treated with a paint that not only reflected sunlight but kept heat trapped inside. Combined with their relatively large thermal mass, this kept the internal temperatures relatively constant as they were carried around on the surface. But after being jettisoned on the lunar surface, and slowly accumulating a thin layer of dust from electrostatic effects, eventually they'd reach temperature extremes similar to the lunar surface itself during its monthly cycle.

« Last Edit: September 18, 2017, 04:53:23 PM by ka9q »

Offline ka9q

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Re: Gardum's thread
« Reply #145 on: September 18, 2017, 05:16:41 PM »
If I am walking around at high Moon noon, and find myself getting too hot from the Sun, I can duck into the shade of a big rock, but still be heated by the solar energy reflected from the lunar surface (albedo heating), as well as the solar energy absorbed and re-emitted from the surface (infrared heating), even as my suit is radiating heat to deep space. 

But I'm also radiating heat toward the lunar surface, and a (very small) amount of heat energy from deep space is impinging on my suit.  There's no one-way switch depending on your view to certain objects.
There is a "one way switch": possibly different optical properties at different optical wavelengths, as I explained in my last message.

But there's no one way switch that can operate at the same optical wavelength. If there were, you'd have a violation of the Second Law of Thermodynamics.

This is a bigger factor on the moon than you might think. A thermal radiator can work efficiently even in direct sunlight because the low absorptivity (high optical reflectivity) rejects the lion's share of the sun's radiation that arrives as visible and near-IR light. While the sun also radiates in the far IR, which the radiator cannot reject, the sun is very small (0.5 deg diameter) compared with the cold dark sky around it. So it doesn't have much effect.

But a thermal radiator on the moon cannot function effectively if it sees much of the hot lunar surface. Despite being much cooler than the sun, and therefore radiating less per square degree of apparent size even in the far IR, the lunar surface could easily occupy a lot more of the radiator's "sky" than the sun and thereby radiate considerably more heat into it. This was a very real problem for the ALSEP experiments left by the last three Apollo missions where the radiators, despite being pointed straight up, "saw" quite a bit of the warm mountains surrounding the landing sites. (It also didn't help that it was almost impossible to keep them free of lunar dust.)

The warm lunar surface was a significant source of heat even to the well-insulated Apollo pressure suits. The Apollo 12 crew, being the first to make two EVAs, commented on how much warmer things seemed during their second EVA even though the sun's direct thermal input to a vertical surface was essentially the same as during their first EVA. The lunar surface, being essentially horizontal, reached an equilibrium temperature according to the sine of the sun's elevation so it was warmer during the second EVA.
« Last Edit: September 18, 2017, 05:20:44 PM by ka9q »

Offline JayUtah

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Re: Gardum's thread
« Reply #146 on: September 19, 2017, 10:24:31 AM »
...but I think a big one was simply its high mechanical strength. NASA wanted to cram as many exposures as possible into each film magazine, and that meant making the film base as thin as possible.

Very much so.  The same constraints existed for the magazines used in CORONA and in ordinary aerial photography.  At my museum we have some old SR-71 magazines with some stock still in it.  Very, very thin.
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Offline Trebor

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Re: Gardum's thread
« Reply #147 on: September 19, 2017, 12:33:07 PM »
I know one source where Gardum got some figures. (see attached pdf)
He quoted the temperatures from the Storage->Processed Film section in a reply on a youtube thread. Without actually naming the document or including the 'For best keeping'.

Offline smartcooky

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Re: Gardum's thread
« Reply #148 on: September 19, 2017, 09:36:17 PM »
...but I think a big one was simply its high mechanical strength. NASA wanted to cram as many exposures as possible into each film magazine, and that meant making the film base as thin as possible.

Very much so.  The same constraints existed for the magazines used in CORONA and in ordinary aerial photography.  At my museum we have some old SR-71 magazines with some stock still in it.  Very, very thin.

We used to use sprocketless 35mm film which we ran in Perkin Elmer Model 2-18 Minipan cameras.  It was very thin and it broke very easily. We used short pieces (about 1m long) for testing. Trying to load them into one of those stainless wire developing spools was bloody frustrating.
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Offline Bryanpoprobson

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Re: Gardum's thread
« Reply #149 on: September 20, 2017, 06:28:59 AM »
I think this thread should be left as it is for now with no more comments until Gardum dignifies the forum with his presence, I will try and flush him out from YouTube but he has been absent there since his comments here.
"Wise men speak because they have something to say!" "Fools speak, because they have to say something!" (Plato)