Author Topic: The Absence of Airlocks  (Read 14332 times)

Offline LunarOrbit

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Re: The Absence of Airlocks
« Reply #45 on: September 07, 2019, 04:33:42 PM »
Hi Jay

You didn't answer my questions.

Answering people's questions was one of the conditions I placed on Jr Knowing when he requested that I remove the posting restrictions I had placed on his account. I am beginning to regret lifting the restrictions.
It suddenly struck me that that tiny pea, pretty and blue, was the Earth.
I put up my thumb and shut one eye, and my thumb blotted out the planet Earth.
I didn't feel like a giant. I felt very, very small.
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Offline Von_Smith

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Re: The Absence of Airlocks
« Reply #46 on: September 07, 2019, 05:22:37 PM »


With regards to the main topic, nobody has given any sort of scientific explanation to the questions I have asked. People point out correctly that other spacecraft have carried the same technology, batteries etc. What they are ignoring is the fact is these components were insulated from the harshness of space.

So, as you yourself pointed out in the OP, were the Apollo spacecraft. 

You have this bizarre conceit that once the air in the cabin was evacuated and the hatch opened, that the insulative properties of the LM would have been instantly, drastically and irrevocably compromised, as if the cabin were suddenly flooded with liquid nitrogen or something.  That's not how thermodynamics works.  Vacuum and cold aren't substances.  They don't come rushing in; heat escapes.  And for the LM on the moon, the only significant method by which heat escapes is radiation, which takes time, and which may or may not even be faster than the rate at which the LM produces heat or absorbs it from sunlight.  Evacuating the air in the cabin loses some heat capacity; leaving the hatch open changes the radiative properties somewhat.  I'll defer to Jay and others on the particulars.

Once the hatch is reclosed, though, the LM cabin would be just as spaceworthy as any satellite or space probe, with or without air.  There is no reason to think otherwise.


Offline raven

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Re: The Absence of Airlocks
« Reply #47 on: September 07, 2019, 05:39:26 PM »
Here's a question for the ages, jr Knowing. If someone like you could 'figure out' an airlock would be needed, why didn't the folks at Grumman? Even if it was a hoax, these folks would still be doing their darndest to design and build a functional Lunar Module, right?
NASA contracting isn't simply them handing the contractor a set of blueprints and saying 'build this'.

Offline JayUtah

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Re: The Absence of Airlocks
« Reply #48 on: September 07, 2019, 06:18:47 PM »
They don't come rushing in; heat escapes.

A more accurate picture of what's happening is to consider the mass of the escaping air -- which is very, very small.  The landed mass of the lunar module is still thousands of kilograms.  The air portion of that is negligible.  Having it suddenly go away changes the thermal picture of the LM very little.

Quote
[R}adiation ... takes time, and ... may or may not even be faster than the rate at which the LM produces heat or absorbs it from sunlight.  Evacuating the air in the cabin loses some heat capacity; leaving the hatch open changes the radiative properties somewhat.  I'll defer to Jay and others on the particulars.

I'd rather go the other direction.  In a phrase:  differential equations.  The rate at which heat radiates affects, and is affected by, the temperature of the object, among many other things.  The math to work out that behavior in the particulars of some given design makes strong men cry.  But the important answer to your question is that objects attain a thermal equilibrium in which they are absorbing as much heat as they are rejecting.  This means their temperature remains constant so long as the conditions remain constant.  How long it takes a system to reach that equilibrium depends on factors that are highly specific to each individual configuration.
"Facts are stubborn things." --John Adams

Offline ApolloEnthusiast

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Re: The Absence of Airlocks
« Reply #49 on: September 07, 2019, 07:17:42 PM »
A more accurate picture of what's happening is to consider the mass of the escaping air -- which is very, very small.  The landed mass of the lunar module is still thousands of kilograms.  The air portion of that is negligible.  Having it suddenly go away changes the thermal picture of the LM very little.
But once you let the air out, isn't the LM vulnerable to the "harsh vacuum" oozing into the cabin and putting cold all over everything?

There's basically no point in even discussing this with him until he can demonstrate willingness to get even a basic understanding of the science involved.  I know you mentioned the math behind this "makes strong men cry", but no math is required to understand that vacuum doesn't have a temperature.  No math is required to understand conceptually that there is no meaningful comparison between air temperature at any location on Earth and the fail temperatures of equipment in a vacuum. 

I tried to be respectful to others.
It is not even remotely respectful to enter into a discussion like this without even a basic understanding of the science involved, let alone to presume to tell others they don't understand something when it is painfully obvious you have absolutely no idea what you're talking about. 

Not knowing something is fine, everybody has a vast multitude of things they don't know.  Expounding on these things as though you are an expert and demanding proof that you're wrong is completely unacceptable behavior.  If you ever grow up enough to do a small amount of study in these topics, you will probably discover for yourself, without need of anyone else's explanation, why things don't work the way you currently assume they work.

Offline smartcooky

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Re: The Absence of Airlocks
« Reply #50 on: September 07, 2019, 09:44:41 PM »
Hi Jay,

Here is something I dug up quickly on the fly about battery survival in the Apollo mission. (I am on my phone).This is for the Rover.  Go to pg 39. As you can see, according to NASA themselves, battery “survival is -15 f. Also check out all the other components, virtually all the components won’t even survive the ‘mundane’ cold temps we have on earth. Balls in your court, bub.  :)

https://www.lpi.usra.edu/lunar/documents/NTRS/collection2/NASA_TM_X_66816.pdf

https://www.lpi.usra.edu/lunar/documents/NTRS/collection2/NASA_TM_X_66816.pdf

Pg 39. The DCE and SPU, the on-board electronics can’t even “survive” a cold day in Canada or a hot day in the Sahara. Yet it managed to work just fine in the harsh vacuum of space. This is not me saying this. This is NASA’s words. I guess they thought they were landing in New York City on a nice fall day.


OK, so where do I begin? How about this....

Understanding of of the difference between "Convective heat transfer, Conductive heat transfer and Radiative heat transfer"



Here's a primer for you on heat transfer in space.

http://www.qrg.northwestern.edu/projects/vss/docs/thermal/2-does-heat-move-differently-in-space.html

Now go read it and come back when (if) you understand what it means, and how it applies to your failure here today.

« Last Edit: September 07, 2019, 09:48:29 PM by smartcooky »
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Offline mako88sb

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Re: The Absence of Airlocks
« Reply #51 on: September 08, 2019, 01:21:21 AM »
Just curious JK, what would it take to convince you that the Apollo manned landings on the Moon were real and happened as historically documented? From my many hours debating with hoax believers on youtube, the one thing I can say with absolute certainty is the vast majority of them would rather cut their tongues out before admitting they were wrong about anything. I think you could take most of them to the moon and show them everything left behind including the Apollo 16 UV telescope, LR tracks & astronaut footprints, LR's parked were they were left and the LM ascent stage impact sites and they would still say they weren't convinced. 

Offline BertieSlack

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Re: The Absence of Airlocks
« Reply #52 on: September 08, 2019, 01:44:47 AM »
with regards to the different length shadows of the astronauts in the EVA A11 DAC footage

Explain how you think the astronaut closer to the light source can cast a longer shadow.

Offline ka9q

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Re: The Absence of Airlocks
« Reply #53 on: September 08, 2019, 03:12:08 AM »
Knowing's ignorance of the Apollo systems, as well as of heat transfer physics, is pretty amusing. Here are just a few of the many things he seems not to know:

1. As explained by others, there is only one form of heat transfer in a vacuum: radiation. However, the LM external environment wasn't a total vacuum in one very important respect: steam (gaseous water) was continuously vented from the LM sublimator to space whenever the LM was powered up (as it was during its entire solo flight and lunar stay). E.g., convective heat transfer to the environment was also significant.

2. The sublimator rejected heat that had been collected from the LM systems with a closed loop of glycol/water coolant (essentially radiator antifreeze) that circulated through a set of "cold plates" to which the various pieces of equipment were mounted. This liquid cooling system was actively controlled with thermostats and pumps to maintain everything at the desired temperature. Some of these cold plates were inside the crew compartment, while others were in unpressurized areas (everything outside the crew compartment).

3. None of the LM's batteries were inside the crew compartment. The batteries all operated in vacuum. There were four (five on Apollos 15-17) large batteries in the descent stage plus two smaller ones in the aft equipment bay of the ascent stage. All were mounted to the aforementioned cold plates through which liquid coolant was circulated. The batteries were in fact among the larger point sources of waste heat that had to be actively removed. They were in no danger of freezing.

4. The entire LM was well insulated against radiative heat transfer with thermal blankets, layers of aluminized Mylar and Kapton alternating with Dacron fabric to space them apart and minimize conduction. They were extremely effective. Perhaps he's heard of "space blankets" sold for camping and survival use and wondered where that term came from.

5. Every lunar landing occurred during early morning at the landing site when the lunar surface temperatures were quite modest. To the extent that the thermal blankets didn't totally block all radiative heat transfer between the LM and the sun, deep space and the lunar surface, the equilibrium temperatures were quite tolerable. Indeed, the excellent thermal insulation created a problem of how to get rid of the excess heat generated by the LM systems and crew metabolism (when the astronauts were inside). That's the reason for the liquid coolant loop and the sublimator.
« Last Edit: September 08, 2019, 03:25:52 AM by ka9q »

Online jfb

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Re: The Absence of Airlocks
« Reply #54 on: September 08, 2019, 09:40:27 AM »
In a vacuum, the only methods of heat transfer are conduction and radiation.  Since the crew cabin was fairly well isolated from the lunar surface, I think we can ignore conduction and focus solely on radiation. 

[At this point I have to rely on external sources - I’m a code monkey, not an engineer or physicist]

This page shows how to compute the rate radiative heat loss using the Stefan-Boltzmann law.  With some rearranging and integrating, you can compute the rough amount of time it takes for an object to cool down from a high temperature to a lower one.

Keeping things “simple”, a solid block of unpolished aluminum (emissivity 0.09) just 10 cm on a side will take around 8 hours to go from 300 K (about 80 deg F) to 255 K (just under 0 deg F).  That’s...not that cold. To cool down to 100 K (roughly -280 deg F) would take around 13 days.  And that’s assuming there’s nothing heating that aluminum block (internal electronics or the Sun). 

IOW, this ain’t Hollywood.  Things and people don’t immediately freeze upon exposure to space.  It takes nontrivial amounts of time for objects to lose heat strictly through radiation.

Now, the crew cabin isn’t a solid block of commercial sheet aluminum 10 cm on a side - there are a bunch of different materials with different emissivities, densities, etc., and most of it’s built in thin sheets.  It’s also full of electronics and heaters to maintain stable temperatures, and it’s standing in the Sun the whole time. 

So evacuating the cabin for a few hours is simply not a big deal from a thermal management perspective.

Offline Von_Smith

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Re: The Absence of Airlocks
« Reply #55 on: September 08, 2019, 11:03:48 AM »
They don't come rushing in; heat escapes.

A more accurate picture of what's happening is to consider the mass of the escaping air -- which is very, very small.  The landed mass of the lunar module is still thousands of kilograms.  The air portion of that is negligible.  Having it suddenly go away changes the thermal picture of the LM very little.

Quote
[R}adiation ... takes time, and ... may or may not even be faster than the rate at which the LM produces heat or absorbs it from sunlight.  Evacuating the air in the cabin loses some heat capacity; leaving the hatch open changes the radiative properties somewhat.  I'll defer to Jay and others on the particulars.

I'd rather go the other direction.  In a phrase:  differential equations.  The rate at which heat radiates affects, and is affected by, the temperature of the object, among many other things.  The math to work out that behavior in the particulars of some given design makes strong men cry.  But the important answer to your question is that objects attain a thermal equilibrium in which they are absorbing as much heat as they are rejecting.  This means their temperature remains constant so long as the conditions remain constant.  How long it takes a system to reach that equilibrium depends on factors that are highly specific to each individual configuration.

My stepfather was a nuclear physicist, and he failed diff eq the first time he took it.  Anyway, thanks for this.  And thanks also for pointing out that the LM actually *did* have a vacuum cleaner (even if it spoiled my joke a bit). 

Offline gillianren

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Re: The Absence of Airlocks
« Reply #56 on: September 08, 2019, 11:35:57 AM »
My understanding is that he claims he'd believe it wasn't a hoax if some other country reproduced a Moon landing.  Why that's his standard for this piece of history and how we know he wouldn't claim it was a hoax as well--after all, other countries' agencies have done science that relies on Apollo and proves its validity, but there it is--gets left unanswered, of course.
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Offline mako88sb

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Re: The Absence of Airlocks
« Reply #57 on: September 08, 2019, 01:52:34 PM »
https://www.lpi.usra.edu/lunar/documents/NTRS/collection2/NASA_TM_X_66816.pdf

Pg 39. The DCE and SPU, the on-board electronics can’t even “survive” a cold day in Canada or a hot day in the Sahara. Yet it managed to work just fine in the harsh vacuum of space. This is not me saying this. This is NASA’s words. I guess they thought they were landing in New York City on a nice fall day.

Here's a pdf you should find interesting:

https://www.hq.nasa.gov/alsj/creel_lrv_experiences_alsj.pdf

Offline JayUtah

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Re: The Absence of Airlocks
« Reply #58 on: September 08, 2019, 02:26:21 PM »
The entire LM was well insulated against radiative heat transfer with thermal blankets, layers of aluminized Mylar and Kapton alternating with Dacron fabric to space them apart and minimize conduction.

This needs to be emphasized.  While the Apollo LM incorporated a number of passive thermal control elements, a more straightforward approach is generally to insulate completely from the environment, preventing as much heat transfer as possible in either direction, and then  to use active controls to manage temperature.  From the engineer's perspective, this achieves a more controllable system that is more resilient to unforeseen conditions.  This was the overarching guiding principle in designing all the manned spacecraft and the space suits.  Then Apollo 13 pointed out the vulnerability of the key presumption in that approach:  that there will always be a source of heat somewhere in the system.

The space suits were almost completely insulated from the thermal effects of their environment, preventing heat flow in either direction.  The astronaut's metabolic heat was the presumptive heat source.  And you can imagine how hot you'd get in a suit that let very little heat pass through to the environment.  Then the LCG and sublimator were operated to reject unneeded heat.  That system was sized to reject either no heat, or a phenomenal amount of it, enough that the astronauts could get very cold if it were operated at full blast.  This is considered a safer design than trying to manage the heat flux across the suit boundary by largely passive means.  That doesn't mean the space suit doesn't use passive heat rejection methods -- a bright shiny outer layer of Beta cloth.  But the passive methods were aimed solely at rejecting heat, not absorbing a measured amount of it to maintain an internal temperature.
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Offline Abaddon

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Re: The Absence of Airlocks
« Reply #59 on: September 09, 2019, 04:35:58 PM »
Hi Abaddon,
I tried to be respectful to others.
Nope

I don’t think you have to be disrespectful to get your point across.
Not my problem if confrontation is all that provokes you to respond. YOU initiated that paradigm and only you.

With regards to your picture of shadows, you are using perspective and distance to create distortion.
All photographs have perspective and distortion. It could not be otherwise.

You do realize the A11 photo not only is the picture centred from above, the shadow of the right astronaut crosses back over the Center of the photo and is still bigger than the more “centered” astronaut.
QED.

With all do respect,
It's "due". Learn the word.
I don’t think you understand the dynamics of the vacuum of space correctly.
ORLY? Let's see your corrections shall we?

Why do you think the lunar morning would impact the shaded insulated interior of the Lunar module?
It's called angle of incidence. Go "research" that.

Further, your answer to how they would reheat the cabin escapes me.
The CM and the LM had to get rid of heat not retain it. This illustrates how disconnected from reality you are.

What radiant heat source are they using in the vacuum to bring temperatures back up.
None. The machinery generated far more heat than they needed, hence the use of porous plate sublimators to shed the excess heat.

You seem to be confusing things when you talk about cavemen and problems of overheating.
Nope. CSM and LM in operation generated far more heat that necessary for thermal requirements hence the had radiators to get rid of the excess heat.

In both cases, there is atmosphere. Here there is not.  So what are they using for radiant heat?
The spaceships. They generate heat all of their lonesome simply by dint of operating. The thermal problem for apollo was not keeping things warm, it was getting rid of the excess heat.