Would the Apollo Moon astronauts have been frozen then cooked like chicken-in-a-bag - One Star Warrior unveiled - page 28

So what happens when we give the film canister the most extreme thermal gradient to deal with ?

If we have a situation where one face of the magazine is fully illuminated and the opposite face is fully shaded, will one face be burning hot and the opposite freezing cold ?

The way the Hasselblad is mounted on spacesuit means that two of of the six faces of the roughly cubic magazine are not exposed to environment ( one attaches to the suit, the other to the camera body ) so the absorbed heat must be radiated out through just four faces.

[link to www.panoramas.dk]

Further more, only three faces of the magazine are available to transfer heat from one side of the magazine to the other, the front face is missing, it's where the film is exposed.

[link to vintagecameraobscura.com]

K

and here I thought that only Yanks were proud to be stupid.

The x-rays the sun puts out are usually low intensity.

Why did your parents keep you away from school...?

[link to www.clavius.org]

Sounds like you have some wisdom on the subject you would like to share with us.

K

Each edge of the magazine is roughly 110 mm long so if only one face is exposed to the sun ( and the lunar regolith is cold ) then the energy input will be -

[link to www.wolframalpha.com]

5.79 W so if each face was equally warm they would radiate 1.45 W. What temperature drop between the illuminated face and the dark face would cause 1.45 W to flow ?

It's hard to know exactly how thick the aluminium case on the magazine is. It has to be strong enough to support the full weight of the camera and lens, without buckling. Furthermore Hasselblad say they replaced all the vinyl fascia with extra aluminium so I think we can say there is at least 1mm thickness in the magazine case.

Aluminium has a thermal conductivity of 237 W.m^-1.K^-1

The total area available to transmit heat through the body will be 3 * 0.11m * 0.001m = 0.00033 m^2

So we have a heat flux density of 1.45 W / 0.00033 m^2 = 4394 W/m^2

And a length of 0.11 m to transmit it through :

( 4394 * 0.11 ) / 237 = 2 K

So in the most extreme case of differential heating on the film magazine, the temperature gradient across the whole body will be no more than 2 K

K

( edit ) This is because the thermal input is relatively modest, the magazine is fairly small and aluminium is a superb conductor of heat.

Another one. Look, if you have some startling insight, please share it it with us. You have obviously spotted some glaring flaw in my method, don't be shy, tell us about it so I can fix up these calculations and get a truer model of what would happen.

K

That Neil Armstrong might just be a genius......

With a phd in astrophysics he would never bring unnecessary weight back to earth......

But from a sound stage......genius

Thanks for that. I think I have covered all of that with the maths to back it up. One thing I want to talk about is this Dr Groves and his oven. That is the biggest mystery, why didn't he understand heat? I would love to hear an explanation.

K

Armstrong's secret moon landing souvenirs surface
[link to www.usatoday.com]

Very interesting thanks. You may like these two threads on that subject.

Thread: Neil Armstrong's secret bag of Moon landing mementos 'that were supposed to remain in space' discovered by his widow in a closet

Thread: Neil Armstrong's secret bag of artifacts there were supposed to be on the moon were found in his closet

K

Just to round up the camera calculations. What would happen if the astronaut went and stood in the shadow of a boulder or the LM. Assuming there is no warm lunar surface to help hold the cameras temperature up, how long until the camera's temperature fell to excessively low levels.

[link to curator.jsc.nasa.gov]

The mass of the film back is a little hard to estimate. The small film back ( magazine ) on the Hasselbad 500c weighs 400g. The much larger magazine on the 500 EDC with its extra aluminium plates must weigh at least 600g.

The specific heat of aluminium is 900 J.kg^-1.K^-1

The last calculation had the film back at equilibrium with a power input and output of 5.79 W. Initially the camera will start cooling at ( 900 * 0.6 ) / 5.79 = 93 seconds / degree K

So the camera will cool by 6.4 K for every ten minutes the astronaut stands in total shade on a cold surface. This rate of heat loss reduces as the camera's temperature falls.

K

Thanks !

There is an interesting summary of the Moon cameras here

[link to www.hq.nasa.gov (secure)]

K

Camera Summary

What NASA and Hasselblad told us about the Hasselblad 500EL DC cameras is that NASA modified them by painting them with silver paint, using different lubricants in the mechanism, adding extra aluminium to the structure and using an ester based film stock that was stable over a wide temperature range.

What we have found is that the cameras temperature range encountered throughout all the lunar missions,

[link to www.wolframalpha.com]

would be at lowest -11 C

and at the highest

[link to www.wolframalpha.com]

would be +6 C

The cameras would be remarkably thermally stable thanks to the careful choice of paint.

We also discovered that the thermal gradient across the camera body.

Thread: Would the Apollo Moon astronauts have been frozen then cooked like chicken-in-a-bag - One Star Warrior unveiled - page 28 (Page 3)

would be at most 2 C

Even in deep shadow

Thread: Would the Apollo Moon astronauts have been frozen then cooked like chicken-in-a-bag - One Star Warrior unveiled - page 28 (Page 3)

The camera would only cool at 0.6 C per minute.

So to answer part of this threads question, the camera design would meet the thermal requirements for operating on the Moon

Soon we will look at the suit again, but before that, Dr Groves.

K

Before finishing with the camera we should look at the source of the claims that the film would be destroyed by excessive heat during the EVA. The assertion was apparently made in a book called Dark Moon by Mary Bennet and David Percy. In the book an experiment conducted by Dr. David Groves is outlined. Apparently Dr. Groves took a colour film canister and baked it in a convection oven for four hours at an air temperature of 355 K, 82 C in order to simulate the thermal environment the film would have encountered during a typical EVA, based on the fact that NASA had recorded lunar regolith temperatures reaching 355 K.

This is very puzzling to me, according to the book not only does Dr. Groves have a PhD. but also "he has a BSc (Hons) Class 1 in Applied Physics" and " He is also a Chartered Physicist and a Member of the Institute of Physics" so he had an excellent grounding in all aspects of physics and is a member of a recognised professional body ( IOP ),

and yet.. he conducts an experiment where the film is thermally soaked at 355 K for four hours by air convection, I simply don't understand why he would conduct such an irrelevant experiment and attempt to draw any useful conclusions form the results.

Here is Dr Groves speaking on another topic. My favourite part was just after 02:05. I nearly fell off my chair with the presenters comment at this point!



[link to www.youtube.com (secure)]

coincidently we now have enough information to suggest an alternative diffuse light source for Dr. Groves to consider.

Neil Armstrong's spacesuit frontal area 1.25 to 1.5m^2, betacloth solar reflectivity ( 1 - absorbtivity ) 0.7
[link to webserver.dmt.upm.es]
solar constant 1362W, solar angle of incidence 14 deg
[link to www.hq.nasa.gov (secure)]

[link to www.wolframalpha.com]

gives us at least 1155W of diffuse visible light being reflected toward the LM.

K

EDIT) This looks like the best place to add some information I found out about Dr Groves' experiment after this thread was sabotaged.

Oh man, oh man! I can hardly wait. IDW is about to produce some of his calculations!!

Prepare for excuses in three... two... one...

Ambient temperature refers to the temperature of the fluid an object is immersed in. Unless you and Dr. Groves are claiming that the Moon has a dense atmosphere then that is meaningless. The lunar regolith has a surface temperature which is one of the factors in it's power radiation.


Unless Dr. Groves has a large vacuum chamber with walls at < 4 K and a surface of lunar regolith warmed to the temperature required I would suggest he can't. Heating film in air does not simulate the the flow of radiation in a vacuum and can't tell you how the camera would perform thermally.


Except that assuming the film will reach the same temperature as the lunar regolith ( incidentally where does this 220 F temperature come from ?) completely ignores the relevant factors of regolith thermal emissivity, radiative view factor, camera paint thermal emissivity, solar absorbtivity of the paint and conductance of the camera body. I would suggest that heating film in a convection oven is exactly the definition of "faking it"

K

No bet.

What work have you attached your real name to?

I am fine with the fact you are denying knowing who I am. I don't believe you, but I am fine with it. Phil Plait and Jay Windley do, and so does agent stalker 74444, and so does NASA and it's contractors.

So you have attached your name to nothing. OK.

Actually, since 74444 is participating in this thread, let's ask him directly.

74444, do you know the actual identity of IDW? Because I certainly do not.

My name is attached to EVERYTHING I write (and I prefer it that way) because this screen ID is the same one I have used for 15 years on the internet and my identity IS ATTACHED TO that screen ID.

Boy you're a real charmer aren't you considering we have never spoken before. So obviosly this post went right over your head Thread: Would the Apollo Moon astronauts have been frozen then cooked like chicken-in-a-bag - One Star Warrior unveiled - page 28 The space suit was generalised to a sphere to simplify calculations. A sphere always presents the same effective area to the Sun regardless of angle of incidence. This negates the need to work out changes in insolation as the solar angle of incidence increases on the astronaut throughout the day, and the astronaut turns to present different proportions of surface area to the Sun. If you think this is a cheat then I can generalise the suited astronaut to a cylinder, it will only make the suit more stable in temperature as the falling suit insolation is compensated by the rising regolith temperature, it's more complicated to work out but still pretty straightforward.

K

Everything except of course this post where you claim it is attached to everything.

Radiative forcing, oh dear, I think you need to put down those news articles about climate change and learn some basic physics.

What the hell does "Perhaps you can attack your real name o your "wok" like Ihave mine. Perhaps n ot ." mean ???



So you would like me to go over heat flows by radiation again ? First things first, polished aluminium is not a good surface if you want to keep something cool in the Sun. The solar absorbtivity is 3 times higher than the thermal emissivity, that's why aluminium objects get hotter than white painted objects in the Sun, the camera was painted, not bare aluminium. Anyway, using aluminium as listed here
[link to www.redrok.com]

If we have a thin polished aluminium plate 1m^2 suspended 1m above an infinite flat isothermal plane made of lunar regolith ( thermal emissivity 0.88 ) at 377 K ( 220 F ) the power radiated from the regolith to the plate is defined by the Stephan-Boltzman law, whether you like it or not.

[link to www.wolframalpha.com]

1008 W

Thermal abosortivity = thermal emissivity = 0.03 for polished aluminium so power input to the plate is = 1008 * 0.03 * 1m^2

Power output is again defined by the Stephan-Boltzman law
0.03 * sigma * temperature ^4 * 2m^2 radiating from both surfaces !

The plate comes into thermal equilibrium when the power output is equal to the power input so those two terms will balance at a particular temperature like so

[link to www.wolframalpha.com]

301 K, 33.9 C, 93 F



K

Firstly you are on a thread I started, not the other way round. Secondly, apart from being an obnoxious specimen you have shown you have next to no knowledge of physics, I don't think you are in a position to call anyone a cretin. Thirdly if you can't work out the modelling advantage of having an object always present 1/4 of it's surface area at 0deg angle of incidence to the source of radiation whatever its orientation then please tell us the average surface area of an astronaut perpendicular to icident radiation as the Moon revolves and the astronaut goes about his work over the course of an EVA, oh and show your calculations.

K

SIMPLE

Remember thermos flask? What keeps your coffee hot for hours? VACUUM.
Vacuum is the best insulator in the world.
So when the astronauts are on the sunny side of the Moon, they quickly heat up from the sunrays and can't cool down just like coffee in the thermos flask - because they are surrounded by vacuum! The cooling system runs at full power but it has limits, and its in vacuum, too, so things are not as simple as a conventional fridge. Moreover, sunrays keep coming, but the astronauts' cooling system looks suspiciously small.

And on the dark side of the Moon, the cold sets in. But that's not such a bad trouble - the spacesuit can be heated, and then will stay warm for hours, surrounded by vacuum better than coffee in the flask