There was no ineptitude involved. The cooling system on the CSM was completely shut down; they couldn't have afforded the power, even if it had been needed.

As has been stated previously in this thread, the cooling system of the LM was operating at a minimal level to keep critical components (specifically, the electronics associated with the guidance system, computer, and life support systems) from overheating. This had little impact on cabin temperature, and was unavoidable since an overheated computer is neither a good space heater nor a useful computer.

This is bull, pure and simple. What do you claim to have copyrighted? Anything posted here is in the public domain. Anything you haven't written yet is not copyrightable. What are you claiming rights to, the notion that NASA's been lying about Apollo 13?

Don't worry about us, though. Nobody here would dream of publishing such an absurd claim. Write on, brother, and may it bring you the fame and fortune you richly deserve.

I ban people on the way they post, and not because I disagree with them. Sweeping generalizations that are insults will get you banned, because they are rude. Read the FAQ.

What story? The idea that Apollo 13 was faked? There are lots of websites that make the same claim. David Percy wrote a whole book about how the missions were real, but the pictures were faked.

Also, as has been pointed out, posting here is public domain. I have a copyright on the bottom of every page on this website except this forum. That is not an accident; I won't take a copyright on what other people write. But if you make a post here, others can do whatever they like with the idea.

I agree. The Vietnam vet comment was a despicable, cheep shot. I am ashamed I wrote it.

The Vietnam vets did honorable service for the greatest country on earth during a turbulent time when the justice of events is sometimes hard to determine.

I apologise for the comment. It is not the way I truly feel about the vets. The vets have taken too much stuff like that.

Sincerely
SAMU

<font size=-1>[ This Message was edited by: SAMU on 2001-11-09 22:04 ]</font>

<font color="red">GOOD FOR YOU!</font>



<font size=-1>[ This Message was edited by: David Simmons on 2001-11-09 22:21 ]</font>

SAMU:
Actually, I find the rebuttals of more interest than the argument you've attempted to put forward. That's one reason I keep reading this thread. Then I have enjoyed learning about the subject.

__________________
Time crumbles things; everything grows old under the power of Time and is forgotten through the lapse of Time.
~Aristotle

I was hoping to avoid this because a simple explanation of a complex subject is open to multitudes of oppositions. (Note the opposition to a quote of the commonly given tempreture of things in sunlight and shade in near Earth space of +- 200-250 degrees.) But since some of you seem to be getting it I’ll go ahead and present the following in hopes of clarifying my resistance to albedo measurment as a strategy for measuring the heat absorbtion of Apollo and to perhaps getting more readers looking towards the other simpler strategies as more fruitfull.

Albedo is a more complex subject than it would appear to the layman. In simple terms albedo is defined by Van Nostrand’s Scientific Encyclopedia as the ratio of the radiation reflected from an object to the total amount incident upon it. At first this seems to be a simple statement to understand. But the complexities rise so quickly when you define albedo to a precise tool it uses terms that the layman is not likly to understand.

As Van Nostrand further defines it.A=pq where p is the ratio of the brightness at the phase angle of zero to the brightness of a perfectly difusing disk under the same conditions, and q is a factor representing the phase law.

Did you you get that? Good, you’re smarter than the average bear. Why don’t you try to explain it in laymans terms 300 words or less? Here’s my try at it.

Imagine a red light shining on a red pigmented object and a blue pigmented object. The red light reflected from the red object is much greater than the red light reflected from the blue object. The frequency of the light (phase angle) and brightness (amplitude) relative to the chemical structure of the reflecting object (phase law) is key to measuring albedo. The more complex the chemistry and the more frequencies and amplitudes incedent upon it, the more complex the calculations are to measure total albedo of the pigment. Now imagine a complex structure like an Apollo spacecraft with it’s multitude of chemicals and alloys and imagine the complex of frequencies and amplitudes of which sunlight is composed, all the way from the far infrared to the far ultraviolet to X-rays and cosmic rays. It should be noted here that this decription is just the beginning of how complex it really is. A full understanding to use it as a tool for this purpose requires an understanding of trigonometry, calculus. electromagnetics, chemistry and subatomic physics.

Measurement of reflected energy in terms of albedo can be misunderstood as a simple procsess because the simple definition misleads the layman that the solution is simple.

This does not even get into what can happen to light when it’s absorbed such as florecence (A change in frequency of absorbed light) or radiation (the eletromagnetic release of absorbed light energy ) conduction ( electronic transfer of absorbed light energy to adjacent material) photo electric, (changing light energy to electric current) convection, (just conduction to a moving adjacent material.) and retention (not releasing absorbed energy).

Thus albedo is inaplicable to measure the energy absorbed and active as heat from sunlight by Apollo when simple comparasons to similar structures and environments are available. Especialy when very different structures in similar environments arrive at similar heat levels.

Albedo is most often and applicably used as a tool to determine chemical composition by shining a lightof many frequencies and measuring which frequencies are reflected and/or which are absorbed. Because all elements absorb their own specific frequenciy and molecules absorb their own frequencies. Which is why many carbon molocules such as asphalt (a combination of hydrocarbon molecules) are black because carbon can combine with other elements including itself in so many ways that they can be the most complex and largest of all molocules thus able to absorb or reflect, depending on their structure, many frequencies of light.

PHEW!!! That’s the simple explanation.


<font size=-1>[ This Message was edited by: SAMU on 2001-11-11 16:29 ]</font>

Note that this applies to the CSM; the LM was also a NASA design but may have been somewhat more influenced by the contractor.

See Tom Kelly's "Moon Lander", just published. Kelly claims the LM was a Grumman design.

SAMU: But it does tell you somthing about fruit.

Yes, it tells me that fruit occurs in great variety, and that trying to generalize the behavior of a pomegranate by examining a banana is a foolish plan.

The two derelicts we've discussed exhibited widely varying thermal properties. What does this tell you about the thermal properties of derelicts in general? Nothing useful.

If you study a certain set of derelicts in low earth orbit, and discover their thermal characteristics vary widely, where do you put the CSM/LM stack on that same chart? Near the top? Near the middle? Near the bottom? Off the top or bottom of the scale? What would be your justification?

Your plan is so fraught with methodological uncertainty that I can't imagine how you expect to extract any meaningful data from it.

SAMU: I contend that the people who ran the covert op. and released the story had no accurate knowledge of the true thermal properties of the spacecraft.

Who do you claim ran such a covert operation? Why didn't they do their homework? The thermal properties of the spacecraft had been studied and were available in written form.

SAMU: NASA just kept their mouths shut.

Why would they? Why would they let some other branch of the government run a covert operation whose end result is to make them look like incompetent buffoons, and place upon them the blame for nearly killing three highly-regarded pilots? And why would they accept such a scenario when it is the most commonly cited reason for why the Apollo program was cut short, reducing their budget?

Your scenario simply makes no sense from a human perspective. It requires people to act irrationally within the context of the hypothesis.

It also makes not sense from a technical perspective. Above you argue that both NASA and their contractors would reasonably have understood the thermal properties of the spacecraft. You say NASA kept its mouth shut. What about Grumman? What about North American?

Thousands of Grumman employees flocked to their workplaces unbidden when they heard the flight was in trouble. The "Grummies" in the MCC backroom were looking at the telemetry and hearing the reports from the astronauts. Do you expect me to believe that these people who had spent the better part of a decade designing and building this spacecraft, who had produced 4,000 design documents per week for several years, who were some of the most talented engineers in the business -- not one of these people said, "Hey, why is the spacecraft getting cold? It's supposed to get hot under these circumstances?"

Why didn't the Russian engineers, who had seen the basic designs for the Apollo spacecraft and who had considerable experience with their own spacecraft in cislunar space, say, "Why is the American spacecraft getting cold? It looks to me like it should get hot?"

Could the answer possibly be that all this combined worldwide expertise is right when it predicts that the spacecraft would cool down? And could it be that SAMU's argument for an incredible thermal situation is based on the appearance that SAMU is learning thermodynamics as he participates in the discussion?

SAMU: Some times the people who keep covert secrets believe in what they are doing.

Who do you claim was keeping this secret and what reasons can you give for why they would want to keep this particular secret?

SAMU:Proves nothing, supports my man supports.

I don't understand this sentence.

SAMU: Proof is only to be had by going back in time or conducting an exact reproduction of the mission conditions

Since that's impractical, why don't you do the next best thing and provide a detailed, well-supported set of computations that show, in a manner that a thermodynamics expert would accept as plausible, there is anything remotely meritorious in your argument?

SAMU: or by a confession from the covert operatives if any.

Not sufficient. Anyone can claim, in Bob Lazar style, that he was a member of a covert team who accomplished this. I would require, in addition to the confession from a conspirator, proof that the events to which he confessed actually took place and that he participated in them.

You provided your hypothesis as "food for thought". My thoughts are these:

1. Your analysis of the thermal situation is simplistic and lacks a grounding in the principles of thermodynamics.

2. Your cover-up hypothesis is implausible.

3. Your methodology is ad hoc and amateur.


SAMU
[/quote]

No he isn't! If he were in fact learning, it might be worth the trouble. Otherwise ...

He believes that what you are saying supports his position. With that, I'm gonna Piper Anon out of this one.

__________________
Valiant Dancer

SAMU: I was hoping to avoid this because a simple explanation of a complex subject is open to multitudes of oppositions.

Why do you think you have to provide a simple explanation? Your whole problem is exactly that you're trying to simplify what is really a complext situation.

SAMU: in hopes of clarifying my resistance to albedo measurment as a strategy for measuring the heat absorbtion of Apollo

The only thing you should be resisting is the improper usage of the word "albedo". We got stuck on this term because we brought lunar surface temperatures into the discussion early on. It's common to use "albedo" when discussing the thermal steady state of an entire planetoid. Engineers use terms like "reflectivity" or "emissivity" when discussing radiative heat transfer in constructed objects. These are related to albedo, but of course not identical to it.

There is an inverse relationship between absorption and reflection. Increase one and you lower the other. Since albedo is one way of measuring reflection, it can be considered an inverse quantity to absorption.

SAMU: ... looking towards the other simpler strategies as more fruitfull.

No. Your problem is precisely that you think this question has an answer that can be arrived at simply. You don't seem to understand the effect of surface reflectivity and emissivity on the thermal properties of an object heated and cooled primarily through radiation.

SAMU: Albedo is a more complex subject than it would appear to the layman.

Many of us aren't laymen.

SAMU: Why don?t you try to explain it in laymans terms 300 words or less?

Easy. The amount of reflected light depends on the amount of incoming light. It depends on the angle at which the light hits the surface. It also depends on what color the light is versus what color the surface is, and what that surface is made of.

SAMU: A full understanding to use it as a tool for this purpose requires an understanding of trigonometry, calculus. electromagnetics, chemistry and subatomic physics.

True. Why don't you come back when you can incorporate these various disciplines into an argument in favor of your hypothesis.

SAMU: Measurement of reflected energy in terms of albedo can be misunderstood as a simple procsess because the simple definition misleads the layman that the solution is simple.

True, but are you not the one who wants us to throw out all discussion of light-surface interaction and rely on "simple" comparative methods? Are you not the one who argued, without justification, that all objects in cislunar space arrive at the same steady state temperature regardless of material?

You just got done showing us how complicated and potentially chaotic these models are. Now you want to argue that you can just throw together a comparative solution that ignores thermodynamics and, on that basis, claim Apollo 13 was fraudulent.

Pardon me while I laugh.

SAMU: Thus albedo is inaplicable to measure the energy absorbed and active as heat from sunlight by Apollo when simple comparasons to similar structures and environments are available.

Hogwash. The model is either complex and potentially chaotic, or it is not.

"Albedo" isn't generally an engineering term. Or rather, it applies to radiative heat transfer but in a different capacity. I fear we may have confused you by migrating from a discussion of planetary albedo to a discussion of reflectivity and such, without the necessary intervening change of vocabulary.

But that's not the issue. You still maintain, despite lots of valid objections for which you have provided only vague handwaving answers, that you can just compute some kind of numerical average based on whatever spacecraft you choose ad hoc, and that will give you a answer reliable enough to support an accusation of falsification.

SAMU: Especialy when very different structures in similar environments arrive at similar heat levels.

What environments are you talking about?

You've already agreed that cislunar space and low earth orbit are not similar environments, especially for solar heating. At best low earth orbit would provide only a lower bound for estimates of steady state temperature in cislunar space.

Which structures do you refer to, those that are diversely constructed yet achieve identical steady states in space? Is this due entirely to radiative effects?

Upon what basis can you argue that a spacecraft designed thermally for low earth orbit is identical or even qualitatively comparable to a spacecraft designed for cislunar space?

I'm speaking from the point of view of someone who holds a degree in engineering and who has worked in the field of design engineering for aerospace for a number of years. Perhaps you can explain why the Grumman engineers believe they could significantly alter the steady state temperature of portions of the lunar module by covering with materials of varying reflectivity.

Perhaps you can explain why the suits used by firemen in areas of great radiant heat are silver, just like the command module.

Perhaps you can explain why United Air Lines, whose airplanes are dark gray, have to run their A/C packs at high capacity on the ground in my desert city, while Delta airplanes which are white can run them at a lower setting, and American Airlines, whose planes are silver, can sometimes get by just running one pack?

Perhaps you can explain why the radiative heat transfer module on TMG's thermal modeling software, a standard throughout the industry, lets me select the reflectivity of the materials involved.

SAMU: Albedo is most often and applicably used as a tool to determine chemical composition...

No, it's most commonly used in heat transfer models belonging to meteorology. You're talking about spectroscopy.

Cool! (Um...pun intended...) I didn't know that, but, yeah, it makes perfect sense.

If their air conditioners failed...the three planes would get hot inside...at different rates...

Can I presume the same would be true on a cold (windless) day in Chicago, under a weak and pallid sun, if the planes' heaters failed? All three planes would get cold inside...at different rates?

Now, the next trick is to get those three airplanes into orbit...

Grin!

Silas

SAMU,

I going to try once more to come at this from a different direction.

Imagine for a moment that when the CSM/LM stack was launched into translunar orbit, something else was sent along: a very large, perfectly reflective mirror, one designed to allow no radiation to penetrate, and (for good measure) to stay cool so that it didn't radiate significantly in the IR from the backside. This mirror is arranged such that the CSM/LM is in its shadow completely, all the way to the moon.

Now, we remove the astronauts and turn off all the electrical equipment (including the cooling systems). Thus there are no internal heat sources, and the spacecraft is totally shielded from the sun -- as effectively, say, as if it were on the unlit side of the moon.

You would agree, would you not, that in such circumstances, the capsule would get very cold? Even though there is no active cooling going on?

All right. Now put in the astronauts, but leave the equipment turned off. It would be a bit warmer (as long as the astronauts remained alive), right? But not hot, by any means.

But, you say, there was no mirror, no "parasol" for the Apollo spacecraft. But there was! The designers knew that they had some 1500 - 2000 watts of heat to dissipate from the electrical systems alone, and would have to provide lots of cooling capacity for it. They didn't want to make those systems any larger and heavier than necessary.

Therefore, they designed the spacecraft to absorb as little solar energy as possible. Of course, their "mirror" wasn't perfect, so the heat dissipation systems were made big enough to deal with that. But they did a pretty good job, so good that when the electronics and most of the refrigeration was shut down, the solar gain wasn't enough to keep the interior very much above freezing.

For your scenario to be correct, the Apollo designers would have to be incompetent fools, who couldn't figure out how to keep the sun at bay and therefore added vast amounts of unnecessary weight to provide the cooling capacity to re-radiate what they couldn't reflect away in the first place.

So, were the Apollo designers incompetent fools, or were they not?

Why would it need subatomic physics? Seems like thermodynamics is the key here.

Yes, basic thermodynamics solves the problem and subatomic physics is not strictly necessary.

SAMU was still discussing albedo, which he argues is irrelevant to thermodynamics. Subatomic physics is relevant to the physical phenomenon of reflection, expressed in the macro effect as albedo, because reflection is partially governed by the wavelength of the incident light in combination with the subatomic properties of the surface.

For thermodynamics purposes, where comparison to the blackbody absorber/emitter is encapsulated relatively simply without loss of generality, the subatomic component of light reflection is far more detail than is necessary or helpful.

I wasn't necessarily agreeing to all the implications of SAMU's laundry list of relevant fields, only suggesting that a more complex approach is in order.

Thermodynamics 101

Heat always flows from high to low.

Imagine a thermos bottle with warm coffee inside. Inside is a silvered pressure vessal surounded by vacume (or other insulator) with the coffee inside. Attaching the vessal to the hull is a small spring at the bottom to cushion shocks and a mouth. In a dark and/or cold place the heat of the coffee inside will slowly leak out via conduction through the spring and the mouth to the hull where it radiates or is conducted away. The coffee will then get cooler. Place the thermos in a bright hot light so the hull gets hotter than the coffee inside and now the heat leaks slowly to the inside through the spring and the mouth to the coffee inside and the coffee gets warmer.




Imagine an Apollo Spacecraft with warm men inside. Inside is a silvered pressure vessel surounded by vacume (or other insulator) with the warm men inside. Attaching the vessel to the hull is a combination pressure vessel, insulator, hull. In a dark and/or cold place the heat of the men inside will slowly leak out via conduction through the combination pressure vessel, insulator, hull to the hull. The men then get cooler. Place the Apollo spacecraft in a bright hot light so the hull gets hotter than the men inside and now the heat leaks slowly to the inside through the combination pressure vessel, insulator, hull to the men inside and the men get warmer.

For somthing to get cold it's heat has to escape. If the Apollo insulation is so efficient that it can keep the heat on the outside from comming in but will allow the heat on the inside to escape, then tell me where I can get some of that stuff. It'll save me $2500.00 a year in airconditioning costs.

Or did I miss somthing in my years of study of thermodynamics? Or did you?
SAMU

Utah,

This is not just to you but you have done it most often so it'll be easier for the other readers to find and see your messages and see what I'm talking about.

I don't mind you quoting me but it's only courtesy to get it right.

This is just one of the latest of too many.

Utah
Quote:

"SAMU was still discussing albedo, which he argues is irrelevant to thermodynamics."

Where is the message where I wrote that? I don't remember writing it, I wouldn't have written it and I can't find it in all the messages I posted. Would you mind finding it for me and posting the date I posted it?

The next time just copy what I wrote and paste it into a text editor. Then you can look at it as you respond. Then you cut and paste it back to the post window and then you can be sure you get it right. Also your response will be more appropriate to what I wrote rather than what I didn't write. What would be the point of that? When you do somthing like that it reads like a chatroom/bulleten board flame bait.

Forgive me Utah. Compared to some respondents to this you're not as bad. Some of the others read like such flame bait I'm not even answering them.


SAMU



<font size=-1>[ This Message was edited by: SAMU on 2001-11-13 02:58 ]</font>

Trish,

About your message.

Quote:

"Actually, I find the rebuttals of more interest."

Which one was your favorite?

SAMU

SAMU

I asked this a couple of days ago...

Do you consider it possible that Apollo 13 was exactly what NASA said it was?

Surrounding your home with a high-grade vacuum will probably cost more than the air- conditioning...

The Apollo was both in a dark place AND a light place: mirrored on the light side to decrease heat uptake, and with heat-sink vanes on the other to radiate heat away, and rolling slowly to average things out.

If the heat-sink vanes radiate more heat than is picked up from the sunlight, the apparatus will cool down. If not, it won't. As it turned out, it did, but not a whole heck of a lot: it got down to an uncomfortable 50 or 60 F.

(The heat-sink vanes in earthly electronics both radiate and conduct heat away, but, frankly, non-moving air is such a poor conductor of heat, it might as well be a vacuum. *Moving* air is quite different, but still air is a fairly good insulator.)

Silas

[quote]
SAMU: I don't mind you quoting me but it's only courtesy to get it right.

Fair enough. So long as we're being pedantic, my name is Jay. Utah is where I live. It's a desert state in the Rocky Mountains of the U.S. My nick is intended to be interpreted as "Jay from Utah".

Jay: "SAMU was still discussing albedo, which he argues is irrelevant to thermodynamics."

SAMU: Where is the message where I wrote that?

My mistake. You argue that reflectivity (let's get into correct nomenclature, shall we?) is too complicated to figure out, not irrelevant. I apologize.

Therefore you argue that simple empirical comparisons to radically different spacecraft designs in incomparable environments will give you a reliable basis to accuse somebody of fraud. Unfortunately what it sounds like to me is that you don't know enough about thermodynamics to formulate a valid physically-based argument in favor of your theory. Therefore you're attempting to cobble together an argument based on what you do know, regardless of whether it's valid.

Now that we've got this unpleasantness out of the way, let's concentrate on the questions you aren't answering:

1. You claim that significantly different structures in the same environment reach similar or identical steady states. Which specific structures and environments are you talking about?
2. Your methodology assumes there is an established correlation between the thermal environment of low earth orbit and cislunar space. Can you provide a quantitative thermodynamics argument in favor of this method?

3. You claim an agent other than NASA published the story that Apollo 13 had grown cold. Which agency do you claim did this?

4. You accept the premise that NASA and its contractors understood the thermal properties of the spacecraft. Yet you have provided no satisfactory explanation for why NASA and the contractors did not say anything when reports were published containing spurious allegations of fact.
Please answer these questions.

SAMU: Or did I miss somthing in my years of study of thermodynamics?

Oh, give me a break. It's painfully obvious that most of what you know about thermodynamics you've learned in the past couple of days trying to keep your head above water in in this discussion.

In your thermos example let's remove the mouth attachment and the spring. Let's say the inner vessel is held in place by a magnetic field or something so that there's no solid points of contact. There is a perfect vacuum between the inner and outer vessels. The entire assembly is suspended by a thin cable from the ceiling of a darkened room at room temperature.

Please answer the following questions:

1. Will the coffee still cool?

2. Through what mechanism of heat transfer will the coffee cool?

3. Describe how to compute the steady state temperature of the described system.

4. How would the system be affected if the air temperature in the room were raised to 100 C?

Now in relation to the Apollo spacecraft, assume the following conditions.

- An Apollo CSM is placed in deep space. No appreciable sunlight falls on its surface.

- The cabin is pressurized with 5 psia pure diatomic oxygen.

- Only minimal life support equipment is running: a fan circulates the cabin air through lithium hydroxide canisters, and a passive regulator adds oxygen to the cabin as necessary to maintain a breathable atmosphere.

- Three normal human astronauts occupy the cabin.

- The three astronauts are wearing Beta cloth flight suits.

Under these conditions, giving estimates for values not provided, please answer the following questions:

1. Describe the common method used to compute the thermodynamic steady state of this system.

2. List the modes of heat transfer that exist in this system. Give estimates of quantitative values for each heat transfer mode.

3. Compute or give estimates of the heat flux for each principal element in this system.

When you can discuss these questions intelligently, then you will have established that you have a sufficient grasp of thermodynamics to show that your hypothesis has a valid argument attached to it. You have made a claim that the Apollo 13 scenario represents an unlikely thermal state. Therefore it is up to you to demonstrate that your knowledge of thermodynamics is up to the task of quantifying heat transfer.

Time to put up or shut up.

I don't think you're being entirely fair... I couldn't answer those questions, but I've been able to keep up with the discussion. That's a little like asking you to be able to solve the Shroedinger Wave Equations before you can talk about quantum physics, or being able to solve tensor equations before you can talk about Relativity.

Um...but while we're on the subject, was I right or wrong in saying that non-moving air is a fairly good insulator? It's been my experience that still air does not heat up (or cool down) very fast at all, but I don't have any theoretical defense or mathematical model for this.

I thought that the comparisons to differently colored aircraft in the desert sunlight was a sufficiently evocative description for the ordinary bloke to grok the concepts.

Silas

I don't think you're being entirely fair.

I do. These are questions that relate to basic principles of thermodynamics. Notice I'm not asking for tight numerical answers, only discussions about the method of solving such problems.

SAMU has implied he's studied thermodynamics for "years". If that's true, he should be able to answer these questions without much difficulty at all. If he's relatively new to thermodynamics, as appears to be the case, the investigations he'll need to do in order to answer the questions will provide him with the answers he sought here.

I couldn't answer those questions, but I've been able to keep up with the discussion.

I'm confident that many people have been able to follow the discussion, but would have difficulty understanding and solving the problems. But most people aren't making the kind of claims that SAMU is, and therefore aren't carrying as great a burden of proof. Following the discussion is not as involved a process as having initiated it.

That's a little like asking you to be able to solve the Shroedinger Wave Equations before you can talk about quantum physics, or being able to solve tensor equations before you can talk about Relativity.

I don't consider it the same thing, because SAMU is doing more that "talking about" the thermodynamic problem of spacecraft heating. He's making quantitative claims without any indication that he understands the quantitative or qualitative principles. He's relying simply on a sort of hand-waving approach that tries to equate complicated phenomena with whatever in the lay world most closely resembles the phenomena, whether it's a valid comparison or not.

Unfortunately this is quite a favorite tactic of conspiracy theorists. By referring to intuitive principles which may or may not apply, they propose theories which have the appearance of plausibility, but lack an appropriate degree of rigor. Sadly their audience is often incapable of detecting just how fanciful some of these "intuition-based" theories are.

I'm basically trying to guage how much SAMU knows about thermodynamics. That will help me determine how seriously to take his argument. If he is a relative novice in thermodynamics, then I probably won't pay as much attention to this particular argument.

Someone who has taken a first-semester thermodynamics course would be able to answer most or all these questions.

was I right or wrong in saying that non-moving air is a fairly good insulator?

It depends on what comparison you have in mind. A stationary air layer between two surfaces is a good thermal insulator compared to a layer of water, or a layer of concrete. But it's not as good as a layer of nothing (i.e., vacuum).

With air and other fluids you have a bit of of quandry because in gravity the heat transfer from the solid to the fluid will induce motion in it. Hot air rises. In space, where hot air doesn't rise, you would have a more pronounced boundary layer condition at steady state, a thermal gradient extending from the surface of the solid to a point somewhere in the fluid mass. This means the layer of air immediately next to the surface would be hotter than it would with convective motion (either induced or forced) and that means less heat would transfer conductively away from the surface.



<font size=-1>[ This Message was edited by: JayUtah on 2001-11-13 15:57 ]</font>

[quote]
On 2001-11-13 14:34, Silas wrote:
Quite correct. Still air is, in fact, what does the insulating in most of the common forms of thermal insulation, including fiberglass bats, down jackets, and fiberfill.

Down is a lousy insulater when it's wet for the very reason that it collapses and no longer contains dead air spaces.

However, when it comes to radiating fins on electroncis coolers, they don't rely entirely on radiation, even when they are not force-cooled (no fan). Convection is a major player, when the fins are oriented properly. The warm metal heats the nearby air, causing it to rise and drawing cooler air in at the bottom of the fins. Thus the heat is carried away by a combination of conduction and convection, and that is a much stronger effect than radiation for such devices.

(Edited to clarify: the above discussion applies to coolers used in one atmosphere at the surface of the earth, and does not apply to such devices when they're in vacuum and/or a microgravity environment.)

<font size=-1>[ This Message was edited by: Donnie B. on 2001-11-13 16:04 ]</font>

Jay

Quote:

"My mistake. You argue that reflectivity (let's get into correct nomenclature, shall we?)"

(SAMU: Yes lets do that shan't we?)

Jay:
is too complicated to figure out, not irrelevant. I apologize.

SAMU: Wrong again. I wrote that it's too complicated to use as a strategy to figure out the tempreture of Apollo 13. Kind of like using pre WW 2 radar to measure the length of a two by four rather than using a known standard like a tape measure.

Jay:
"Oh, give me a break. It's painfully obvious that most of what you know about thermodynamics you've learned in the past couple of days trying to keep your head above water in in this discussion."

Well you must be a genious. To be able to teach me all I know about thermodynamics in a couple of days reading your flawed inacurate and false posts.

Your test is flawed by key factors being left out. I have clarified my answers by adding the key factors.

Jay

Quote:

"In your thermos example let's remove the mouth attachment and the spring. Let's say the inner vessel is held in place by a magnetic field or something so that there's no solid points of contact. There is a perfect vacuum between the inner and outer vessels. The entire assembly is suspended by a thin cable from the ceiling of a darkened room at room temperature."

SAMU:To clarify, we are describing a room with walls at room tempreture and air at room tempreture. Not a slimy trick room without walls or a room with walls at absolute zero or walls at room tempreture that don't radiate. It's a room with walls at room tempreture and air at room tempreture. And we're going to eliminate " The entire assembly is suspended by a thin cable from the ceiling" and just say the whole thing, room, air, thermos and all, is in zero g. Unless you can show how gravity affects the thermodynamics of the situation.

Jay

Quote:

Please answer the following questions:

Jay:1. Will the coffee still cool?

SAMU: Yes. It will cool to room tempreture if the air and the walls are at room tempreture.

2. Through what mechanism of heat transfer will the coffee cool?

SAMU: Radiation and conduction if there is air at room temoreture and the walls are at room tempreture. Radiation alone if there is no air and the walls are at room tempreture.

Jay:3. Describe how to compute the steady state temperature of the described system.

SAMU: Sutract the amount of heat escaping to the room from the thermos from the amount of heat entering the thermos from the air and walls of the room.

Jay:4. How would the system be affected if the air temperature in the room were raised to 100 C?

SAMU:The tempreture would stabalize at 100 C if the air and walls are are 100 C.

Jay:Now in relation to the Apollo spacecraft, assume the following conditions.

- An Apollo CSM is placed in deep space. No appreciable sunlight falls on its surface.

- The cabin is pressurized with 5 psia pure diatomic oxygen.

- Only minimal life support equipment is running: a fan circulates the cabin air through lithium hydroxide canisters, and a passive regulator adds oxygen to the cabin as necessary to maintain a breathable atmosphere.

- Three normal human astronauts occupy the cabin.

- The three astronauts are wearing Beta cloth flight suits.

Under these conditions, giving estimates for values not provided, please answer the following questions:

Jay:1. Describe the common method used to compute the thermodynamic steady state of this system.

SAMU:Sutract the amount heat escaping from the amount of heat entering.

Jay: List the modes of heat transfer that exist in this system. Give estimates of quantitative values for each heat transfer mode.

SAMU:Conduction through the insulation at whatever rate the insulation conducts to the hull where it radiates away.

Jay:3. Compute or give estimates of the heat flux for each principal element in this system.

SAMU: The astronauts would lose as much heat as they have or can produce at the rate the insulation allows it to escape to stabilize at the tempreture that allows the escape of heat to equal the heat produced. If they can produce 4 watts per hour and it escapes at 4 watts per hour at a given tempreture then the tempreture will remain the same. If they produce 4 watts per hour and it escapes at 3 watts per hour at a given tempreture the tempreture will rise. If they produce 4 watts per hour and it escapes at 5 watts per hour at a given tempreture the tempreture will fall.


Jay

Quote:

"When you can discuss these questions intelligently, then you will have established that you have a sufficient grasp of thermodynamics to show that your hypothesis has a valid argument attached to it."

SAMU: That is the fallacy of proof by authority. What I know and say about thermodynamics or what NASA knows and says about thermodynamics or what Nixon knows and says about tapes has nothing to do with whether the facts support the assertions.

By the way, what message did you post that tought me all that about thermodynamics?


Jay

Quote:

You have made a claim that the Apollo 13 scenario represents an unlikely thermal state. Therefore it is up to you to demonstrate that your knowledge of thermodynamics is up to the task of quantifying heat transfer.

SAMU: No. It's up to me to post the facts which support the assertion It's up to you to show the facts are in error. If the facts are not in error and support the assertion then the assertion is reasonable.

Fact 1: Objects in steady sunlight in trans lunar space reach a surface tempreture of 200 degrees before they radiate as much energy as they absorb. Unless there is an active heat exchange pumping heat out faster than it comes in. Factual examples already posted. Find some fact to refute those examples. Or post some thermodynamic principals that apply.


Simple thermodynamic test for you:

1) If an object at 200 degrees in sunlight radiates at the same rate that it absorbs, what is it's steady state tempreture?


2) If an object at 400 degrees in sunlight radiates at the same rate that it absorbs, what is it's steady state tempreture?

3) If an object at 38 degrees in sunlight radiates at a lower rate than it absorbs, what is it's steady state tempreture? Higher or lower than 38 degrees?

4) An object in sunlight can radiate more energy than it absorbs only if what?

5) Give examples of objects without active heat exchange in constant sunlight in space at a distance from the sun the same as the Apollo at a tempreture of less than 50 degrees. Besides apollo 13.

Quote:
Time to put up or shut up.

SAMU


<font size=-1>[ This Message was edited by: SAMU on 2001-11-13 16:54 ]</font>

Peter B,
Quote:

"I asked this a couple of days ago...

Do you consider it possible that Apollo 13 was exactly what NASA said it was?"

SAMU: I find no thermodynamic principal that supports thier assertion as stated.

Quote:

(paraphrasing)

"There was no active environmental heat exchanger opperating (approximatly 60 square feet of radiator surface off line. Link to example already posted http://images.jsc.nasa.gov/images/pao/AS13/10075514.jpg ) except that used for the electronics. (Approximatly 8 square feet of radiator surface. Link to example already posted http://www.hq.nasa.gov/office/pao/Hi...rams/ad004.gif ). The spacecraft cooled to 38 degrees. It was in direct sunlight 24 hours a day for 5 days. Objects in direct sunlight reach tempreture of 250 degrees. (link to example already posted http://kids.msfc.nasa.gov/News/2001/...tationCool.asp


Now I have a question for you:

Based on the pictures decribe where the environmental control system radiator panels are and where the electrical power system radiator panels are.

What are their respective sizes (approximatly)?

SAMU

<font size=-1>[ This Message was edited by: SAMU on 2001-11-13 17:38 ]</font>

Have a care here folks. I just deleted a post to this thread, and tempers are starting to heat up, no pun intended. There is still some good science to mine from this topic, so I won't lock the thread... yet.

__________________
Phil Plait
The Bad Astronomer
http://www.badastronomy.com
badastro@badastronomy.com

SAMU: Wrong again. I wrote that it's too complicated to use as a strategy to figure out the tempreture of Apollo 13.

Okay, we're finally converging. Where I used to work we had software that would do just this. You plug in the geometry and the thermal situation and it would give you wonderful simulations that look so good on trade show posters. It's specifically made for modeling the thermal behavior of spacecraft. I'd get myself a copy of it, but it costs more than my car.

If someone handed me a pad of paper, a calculator, and a pencil and told me to compute the various thermal states of an Apollo command module based on the basic principles of heat transfer, I'd tell them to go jump in the lake. A very cold lake.

But you're throwing out very important data by saying we can just compare the steady-state temperatures of objects in space and not consider their construction characteristics.

SAMU: Well you must be a genious. To be able to teach me all I know about thermodynamics in a couple of days reading your flawed inacurate and false posts.

Um, I'm not claiming to be the one teaching you about thermodynamics. What I meant was that you seem to be doing research offline in response to questions raised here. When I say "you're learning" about thermodynamics that isn't to say I'm teaching.

SAMU: Your test is flawed by key factors being left out. I have clarified my answers by adding the key factors.

I left out key factors on purpose. People who know what they're talking about know what they need to fill in. People who are faking it don't necessarily know what's missing.

Note that I didn't specify the temperature of the coffee.

SAMU:To clarify, we are describing a room with walls at room tempreture and air at room tempreture.

Yes. The intent was to introduce hot coffee into an environment that had previously been at equilibrium.

SAMU: And we're going to eliminate " The entire assembly is suspended by a thin cable from the ceiling" and just say the whole thing, room, air, thermos and all, is in zero g.

Fine by me. The point was to eliminate the need to consider conduction through whatever was holding up the thermos.

SAMU: Unless you can show how gravity affects the thermodynamics of the situation.

As long as you know how it would affect the system I don't mind.

SAMU: Radiation and conduction if there is air at room temoreture and the walls are at room tempreture. Radiation alone if there is no air and the walls are at room tempreture.

That's what I was fishing for. You left out radiation in your example, and I just wanted to know if that was an intentional omission for the sake of simplicity. Thank you.

In gravity you have to deal with convection. It's okay with me if you want to consider convection a special case of conduction. I do it all the time for simplicity in discussion.

The coffee transfers heat to the inner vessel via conduction, or convection if you prefer, and also through radiation. The inner vessel transfers heat to the outer vessel through radiation and nothing else. The outer vessel transfers heat to the "environment" through radiation and convection (conduction, whatever).

SAMU: Sutract the amount of heat escaping to the room from the thermos from the amount of heat entering the thermos from the air and walls of the room.

What thermal gradients, if any, would there be? Would there be a thermal gradient in the coffee? Across the inner vessel wall?

SAMU:The tempreture would stabalize at 100 C if the air and walls are are 100 C.

I really only wanted to know if you had considered radiation from the environment back into the vessel. As I said, most of this series of questions was just to determine where radiation fit into your thinking.

I was hoping you'd mention the role of differential equations in the computation of steady state. For heaven's sake I sure didn't expect you solve any, but that's what I was fishing for when I asked for a description of how to deal numerically with systems progressing toward a state of equilibrium.

SAMU:Sutract the amount heat escaping from the amount of heat entering.

I was hoping for something a little more detailed. Specifically I was hoping you'd talk about what thermal gradients might exist in such a situation.

SAMU:Conduction through the insulation at whatever rate the insulation conducts to the hull where it radiates away.

Again, I wanted something more detailed. Astronauts transfer heat through convection and radiation. (I insist on convection here rather than conduction because I'm presuming the astronauts are moving about. That's effective forced convection.) Cabin atmosphere transfers to inner hull via convection and radiation. Inner hull transfers to insulation via conduction and radiation. Insulation transfers to outer hull via conduction and radiation Inner hull transfers to outer hull via conduction through attach points. (The insulation is fundamentally opaque and therefore no transfer occurs between the hulls via radiation.) Outer hull radiates.

SAMU: The astronauts would lose as much heat as they have ...

Okay, I really didn't expect a good answer to this. Those who get really excited about thermodynamics would have solved this numerically.

The answer I was fishing for was that the astronauts are the only "input" source of heat. Everything else in the system is a transfer of some kind.

SAMU: If they produce 4 watts per hour and it escapes at 3 watts per hour at a given tempreture the tempreture will rise.

And as the temperature increases, the rate of radiation increases. In fact, an increase in the temperature of the radiator produces a fourth power increase in the heat flux.

SAMU: That is the fallacy of proof by authority.

I meant "valid" in the sense "worth paying attention to," not "leading toward a true conclusion."

The problems of proof by authority do not apply to expert testimony. This caveat appears in any textbook's discussion of this particular fallacy. You characterize your line of reasoning as a simple "facts support the conclusion" scenario, when in fact that's not the case. The facts in this case require competence in thermodynamics in order to evaluate their relevancy, behavior, and therefore their degree of support for the hypothesis.

SAMU: By the way, what message did you post that tought me all that about thermodynamics?

I have not made any such post, nor have I claimed at any time to have made such a post. I was referring to the posts made early in this discussion by Bad Astronomer, David Simmons, and others. You seem to have completely ignored the implications of those posts.

SAMU: No. It's up to me to post the facts which support the assertion It's up to you to show the facts are in error.

Agreed.

Fact 1: Objects in steady sunlight in trans lunar space reach a surface tempreture of 200 degrees before they radiate as much energy as they absorb.

This is not a fact. Q.E.D.

SAMU: Factual examples already posted.

You gave two examples, lunar material (already discussed) and the space station (discussed below).

SAMU: Find some fact to refute those examples.

Already done. The descent stage of the lunar module was composed of components that had different steady-state temperatures.

SAMU: post some thermodynamic principals that apply.

Already done. Several posters early on gave you computations, examples, and qualitative discussion pertinent to this point.

Now on to your questions. I've collapsed a few of them into algebraically equivalent form for convenience.

SAMU: If an object at K degrees in sunlight radiates at the same rate that it absorbs, what is it's steady state tempreture?

Assuming no other transfer modes apply, the simple answer is K degrees. The definition of steady state in an radiation-only system is when the radiation and absorption rates are equivalent.

SAMU: 3) If an object at 38 degrees in sunlight radiates at a lower rate than it absorbs, what is it's steady state tempreture? Higher or lower than 38 degrees?

Higher. In the simple scenario the temperature of the object rises until its radiation rate is equivalent to the absorption rate.

SAMU: 4) An object in sunlight can radiate more energy than it absorbs only if what?

Only if its temperature is above the steady state temperature suggested by a radiation-only model.

SAMU: 5) Give examples of objects without active heat exchange in constant sunlight in space at a distance from the sun the same as the Apollo at a tempreture of less than 50 degrees.

I assume you mean 50 F.

I'm not going to answer that question. I'm instead going to explain what's been wrong with your questions to me, and what's been wrong with your answers to my questions.

You talk about "objects in space" as if there were no thermal gradients in any of these objects (or structures, in the case of spacecraft). You seem to believe that if you put an object in cisulanar space under constant solar illumination, that object will reach 200 degrees and that all parts of it will be that same 200 degrees.

But we know that's not true.

Say we put a hollow metal sphere filled with air out in cislunar space. We keep it from rotating. The side facing the sun will get hot. The side facing away from the sun won't get as hot. Heat will conduct through the material from the hot side to the cold side. So the cold side will be a little warmer than the temperature it would reach without being connected to the hot side.

But since the radiation rate is proportional to the fourth power of the temperature, just boosting its temperature a little will really lift its radiation rate. The question is: can it radiate faster due to the increase in temperature than it can be replaced via conduction through the material? You betcha. What's the result? A thermal gradient.

Now what happens to the air inside? Let's suppose we have a little mouse in there stirring up the air as he floats around (forced convection). And his metabolism adds to the system. If he moves around enough, we can assume the air becomes reasonably isothermal. Does that mean the outer shell is isothermal? Nope. Does that mean the air is the temperature of the mouse? Not necessarily.

Now we consider two identical spheres, one composed of a dark matte black material, and the other composed of a very bright, shiny material. The mass and geometry of the mouseships are identical.

The black ball obviously absorbs more energy than the silver ball. (The balls transmit no light, therefore what is not reflected has to be absorbed.) But the black ball radiates more energy than the silver ball. Would they then reach an equivalent state of equilibrium (200 F)?

The answer to that question lies chiefly in whether radiation and absorption behave identically in response to temperature. If differences in material properties (i.e., shininess) cause absorption and radiation to behave differently for different materials, then different materials would have different equilibrium temperatures. The equilibrium would still be the temperature at which absorption and radiation were equivalent, but it might not necessarily be the same for different materials.

There exists a quantitative solution to this problem, but we don't need it. The qualitative solution may be inferred from the fact that people who build comm satellites for a living (and who therefore ought to know what life is like for permanent cislunar residents) put matte black stuff on the parts of the spacecraft that should be warm, and shiny silver stuff on the parts of the spacecraft they'd prefer kept cool.

And if everything in cislunar was just always isothermal, the people who sell thermal modeling software to aerospace engineers ought to be the ones we lock up for fraud.

SAMU: The spacecraft cooled to 38 degrees.

The interior air temperature of the spacecraft was 38 F. Was that the temperature of the spacecraft skin? Could the skin of the spacecraft have been at a higher temperature at equilibrium? Could parts of it have been at a higher temperature, and parts of it at a lower temperature? Is an Apollo spacecraft isothermal?

SAMU: Objects in direct sunlight reach tempreture of 250 degrees. Link to example already posted.

Well, your example is for low earth orbit, not cislunar space. You still haven't explained what makes it an applicable example.

And you're only citing half your example. The sunlit side is 250 F. The shady side is -250 F. But it's the same object! Obviously this isn't an isothermal object. Half of it is really hot, and half of it is really cold. So let's fill up that spacecraft with several thousand mice all stirring up the air and making at least the air as isothermal as it can be. What would be the temperature of the air inside? +250 F? -250 F? 0 F? Something in between?

Your statement "all objects in space reach an equilibrium temperature of 200 F" just doesn't hold. Your examples don't support that. Common spacecraft design practice doesn't support that. Radiation and absorption don't support that.

What part of your argument do you believe we haven't completely shot down here?


<font size=-1>[ This Message was edited by: JayUtah on 2001-11-13 19:35 ]</font>

Bad Astronomer,

You do what you think you have to.

I think this thread is getting back on track. Bit by bit as long as messages respecting my authoritah, or anybody elses for that matter, are kept to a minimum and the questions are regarding the facts at issue.

SAMU