Author Topic: YouTube Madness  (Read 33266 times)

Offline Inanimate Carbon Rod

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YouTube Madness
« on: January 31, 2013, 06:50:51 PM »
An often observed and lamented fact around these parts is the raging inferno of stupidity often concerning the "Apollo Hoax" on YouTube.

I've come across a right jaw dropper in a discussion thread concerning Mythbusters, which I thought I'd share:

Quote
White color is no defence against intense IR rays in a vacuum. Just as with radiation on Earth, there is not much difference in wearing white or black on a hot summer's day.

This is so dumb, surely the person who posted it must know it's not true. But then again....  :o

Anyone else got anything to share?
« Last Edit: January 31, 2013, 07:01:27 PM by Inanimate Carbon Rod »
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Offline JayUtah

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Re: YouTube Madness
« Reply #1 on: January 31, 2013, 07:06:13 PM »
Gives new meaning to, "The Stupid -- It Burns!"
"Facts are stubborn things." --John Adams

Offline Inanimate Carbon Rod

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Re: YouTube Madness
« Reply #2 on: January 31, 2013, 07:09:10 PM »
Jay, you can probably answer this - What colour was the external casing of the Hassleblad cameras used on the Lunar Surface? Were they polished aluminium or silver reflective, or were they painted white? I'm sure it was the latter former.

Edit: meant former. Need to pay more attention when I'm posting.
« Last Edit: January 31, 2013, 09:01:13 PM by Inanimate Carbon Rod »
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Offline ka9q

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Re: YouTube Madness
« Reply #3 on: January 31, 2013, 07:40:24 PM »
I'm not Jay, but I think I can answer this. The cameras appear to have had a flat aluminum finish, not white paint.

The two numbers you really want are absorptance (α), the fraction of incoming visible and near-IR light (from the sun) that is absorbed and converted into heat, and emittance (ε), the efficiency of the surface in radiating thermally in the far IR. The ratio of the two, among other things, control the equlibrium temperature in sunlight.

This explains apparent paradoxes like polished metals getting very hot in the sun. Although they have very low absorptance, their emittances are even lower so what little heat they absorb, they hold. If you want to make a solar heat collector, you still want the blackest possible surface.

When you want to isolate a surface thermally from the environment, as you usually do on the moon because of the large changes between shade and sun, you generally want low values for both α and ε -- hence the metallic finishes on the cameras.



Offline Inanimate Carbon Rod

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Re: YouTube Madness
« Reply #4 on: January 31, 2013, 07:45:53 PM »
Ka9q, thanks for your reply. Some moron on YouTube reckons they were painted white and wanted to check before I called bullshit.
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Offline ka9q

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Re: YouTube Madness
« Reply #5 on: January 31, 2013, 07:57:58 PM »
This kind of thing is easy to check; just look up the historical photos:

http://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/images/hasselblad_lg.gif

You can estimate the absorptance by just looking, but the emittance has to be measured or analyzed. Quite a few spacecraft materials have very different values of α and ε, precisely to give the thermal designer control over heat flows and equilibrium temperatures.

Most ordinary materials, metals excepted, have fairly high emittances regardless of how they look in visible light. Even white paints. Human skin, regardless of color, has a very high emittance meaning it is almost perfectly black at far IR and an almost perfect thermal radiator. An average adult human radiates about 1 kW of thermal heat while generating only 100-200W at rest, which is why we get so cold in the desert at night without good clothing even when the wind is calm.


Offline Noldi400

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Re: YouTube Madness
« Reply #6 on: January 31, 2013, 08:06:33 PM »
Ka9q, thanks for your reply. Some moron on YouTube reckons they were painted white and wanted to check before I called bullshit.
Here's a pic of some guy demonstrating the controls on one of the Apollo Hassies that wasn't flown:



It's pretty clearly a brushed metal finish, not a painted one.
"The sane understand that human beings are incapable of sustaining conspiracies on a grand scale, because some of our most defining qualities as a species are... a tendency to panic, and an inability to keep our mouths shut." - Dean Koontz

Offline Inanimate Carbon Rod

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Re: YouTube Madness
« Reply #7 on: January 31, 2013, 08:08:59 PM »
I wanted to check with the people who know™, because you don't just provide the bare facts, you also give helpful associated information. Thanks.
« Last Edit: January 31, 2013, 09:45:28 PM by Inanimate Carbon Rod »
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Offline JayUtah

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Re: YouTube Madness
« Reply #8 on: January 31, 2013, 08:29:10 PM »
Here's a pic of some guy demonstrating the controls on one of the Apollo Hassies that wasn't flown:

Wow that guy has incredibly bad hair.  Why do they let people like that on TV?

Quote
It's pretty clearly a brushed metal finish, not a painted one.

There's a slightly fuzzy close-up at the top of this page.  http://www.clavius.org/techsuit.html

Is it brushed aluminum?  No, not exactly.  Is it a coating?  Yes.  Is it white?  No, it's aluminum-based.  If the finish were entirely intact, the entire body would look like it were brushed aluminum.  But in this photo you can see where the finish has been worn away at the edges.  It looks very much like the aluminized coating on a Thermos bottle, but with a very much smaller "grain."
"Facts are stubborn things." --John Adams

Offline Abaddon

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Re: YouTube Madness
« Reply #9 on: January 31, 2013, 09:00:10 PM »
 
Wow that guy has incredibly bad hair.  Why do they let people like that on TV?

Yeah, I hate that guy, always going on as though he knows anything.   ;D

Offline ka9q

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Re: YouTube Madness
« Reply #10 on: January 31, 2013, 09:07:33 PM »
How did that actor in the suit avoid overheating and suffocation?

Offline Inanimate Carbon Rod

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Re: YouTube Madness
« Reply #11 on: January 31, 2013, 09:13:19 PM »
How did that actor in the suit avoid overheating and suffocation?

NASA's magic?
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Offline JayUtah

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Re: YouTube Madness
« Reply #12 on: January 31, 2013, 09:16:18 PM »
How did that actor in the suit avoid overheating and suffocation?



It was nighttime and therefore reasonably cool.  These are the suits made for From the Earth to the Moon, by Global Effects who sent their designer to help wrangle them.  The PLSS is empty except for a small 12-volt battery and a fan assembly that feeds air through the oxygen hoses.  The fishbowl helmet was not used; only the LEVA, loosely fitted over his head.

Still by the end of the shoot (ca. 3:30 AM) Ollie was pretty worn out.  Also the metal helmet ring seal cuts into your clavicles something fierce.  Between takes the Global Effects technician stood behind him and lifted it to take the weight off.
"Facts are stubborn things." --John Adams

Offline JayUtah

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Re: YouTube Madness
« Reply #13 on: January 31, 2013, 09:17:31 PM »
Wow that guy has incredibly bad hair.  Why do they let people like that on TV?

Yeah, I hate that guy, always going on as though he knows anything.   ;D

  8)
"Facts are stubborn things." --John Adams

Offline Inanimate Carbon Rod

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Re: YouTube Madness
« Reply #14 on: January 31, 2013, 09:34:13 PM »
I see Jay continues to recieve his NASA disinformation paycheque. I read that on abovetopsecret.com.

:)
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