I will not put words in his mouth.

I'd like to see numbers come out of his mouth. It's one thing to handwave about "elementary physics" and complain about a hot car. (Believe me, it's August in Utah and I'm about to go climb into mine.) But it's another thing altogether to put a quantitative face on things such as how hot stuff gets in space instead of in an Earth parking lot. Elementary physics still requires computation. It's simplified first-order approximations, but it's still quantitative. Several posters have already applied "elementary physics" to this problem and have challenged what appears to be IDW's presumption.

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I'd like to qualify my post to agree with Jay that the problem needs to be stated quantifiably. If we say "radiative cooling is impossible," that is a simple (if erroneous) statement. If we say "radiative cooling would be insufficient," we MUST use numeric models to show if that is so or not so.

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You read me like an open book, Jay. Your paraphrase hits the gist as well as the nuances of what I attempted to convey. Nobody speaks for me*, but in this instance, you may as well have.

*(... but my libido and my own stubborn pride, and then only sometimes.)

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To my knowledge there were no sublimators on the vehicles themselves, though I could be wrong.

The Apollo CSM ECS did not use a sublimator. It did, however, incorporate an auxiliary chiller in the form of a glycol evaporator. It works according to many of the same principles as a sublimator.

The closed-loop water-glycol coolant cycle was largely self-sustaining, requring only a few watts of electrical power to run its pump. As such it could continue rejecting heat effectively so long as it was provided with electricity. The radiators had a significant margin of heat rejection capacity. In fact, under nominal loads, not all the coolant was even sent to the radiators; some bypassed it and was remixed with the radiator outlet volume. That's to keep some equipment from getting too cold.

During peak heat loads the bypass was closed and all the coolant went through the radiator. During excessive heat loads, the evaporator was activated.

The glycol evaporator passes the water-glycol coolant into an exchanger in a jacket that is vented partially to space vacuum. A valve controls the air pressure in the evaporator jacket. The evaporator does not actually evaporate the glycol, as the name implies. Instead, water from the fuel cells is introduced into the evaporator outer jacket, which is the chamber partially vented to space. At lower pressure the water evaporates more readily. Water vapor escapes to space at a controllable rate through the pressure vent tube. Each unit mass of water that evaporates draws from the water-glycol loop heat equivalent to the heat of vaporization of water, at a rate dictated by the rate of evaporation.

This is very similar to the mechanism used in the suit sublimator. The heat rejection there is through heat of sublimation -- greater per unit mass than the heat of vaporization. And the mechanism of introducing the water to the vacuum is different in the sublimator; through a porous plate into raw vacuum rather than in liquid form through a valve as occurs in the evaporator.

But both transfer the heat from the working fluid into a sacrificial material that is subjected to a heat-consuming state change. Both the evaporator and the sublimator techniques require a supply of water, thus limiting their duty cycle to water on hand. Hence the evaporator was considered only for incidental or emergency use.

Does anyone have a technical description of the apparatus?

Yes, but only in print. Someone else may have a link if that's what you want.

I believe, with this post, that all of IDW's questions have been answered so far.

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Nobody speaks for me*, but in this instance, you may as well have.

I'm relieved. My intent was not to represent you, but to springboard from your statement and address what I believed was a lingering misconception that IDW's "simple-is-sufficient" premise would fly.

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Thank you for the detailed explanation!

As he did indicate vehicles (plural), didn't the LM use a sublimator?

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As he did indicate vehicles (plural), didn't the LM use a sublimator?

Yes, as did the Saturn 1B and V instrument units. The LM and Saturn ECS subcontractor descends to Hamilton Sundstrand, today the leading manufacturer of porous-plate sublimators -- e.g., http://www.snds.com/ssi/ssi/Applicat...rv_sublim.html

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Well. , I think we can all se now why I wanted this to be one on one. This is degenerating into a three ring circus . I am not suprized.
You all know who I am and you know my abilities, let us not go down this road again.

I see a very educational discussion of heat transfer, and it's application to Apollo...maybe it's just me.
Was there a problem with how NASA says they addressed the issue?

To be sure, there are quite a few posts to read through, but there was also a great deal of explanatory material. I don't see a great number of questions directed towards you, so that part shouldn't be that difficult to handle.

Actually, I don't know who you are. I've heard your name mentioned before, but little more than that. Prior to your recent posts at BAUT, I had not read anything by you, so I didn't have many preconceptions coming into this discussion.

What I would appreciate is a clarification of your claim. At this point, it lacks detail. Just what are you saying about heat transfer regarding Apollo? Have the answers in this thread cleared up your concerns? If not, why?

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I never said heat couldn't radiate into a vacuum.What I did say is that that process alone could not shed the heat produced by the equipment, the astonauts themselves and the effects of solar energy being absorbed by the spacecraft. Remember, we are talking about a wide spectrum of energy coming from the Sun, reflective material is not sufficient to prevent heating.
While the outer skin of the vehicles may have been 'really shiny' and the insulation very good between this "skin" and the inside, there is no escaping that a buildup of heat energy would occur that some process would be required to mitigate.

Jay has described in a fairly detailed explaination of the cooling process that was used on one of the spacecraft components and a bit on the other. I need to review carefully the information and compare it with my own ebfore I comment.
I would also request he source his information, if possible, so a detailed review of it can be made. One thing that has never been explained to me as of yet is why A13 would be cold when we all see a cooling apparatus was required during normal operation. How much heat did the electrical circuits that were lost or deactivated contribute to the overall heat budget of the spacecraft? Why would there be excessive heat from properly wired and installed electronics? I know there would be a very minimal amount of heat produced, but it seems irrelevant in the overall heat budget.
What we need to determine is approximately how much heat was being produced internally and how much was being absorbed from the Sun, and determine what temperature the vehicle would have to get to before it reached equilibrium, that is loss of heat through radiative forcing+other processes Jay mentioned=Heat produced internally by the spacecraft and absorbed from the Sun.
It is my contention that an object in space this near the Sun nomatter how well insulated internally will eventually heat up to an very uncomfortable level, and it has basically only one way to shed heat. Jay claims another, radiators.
In my experience radiators work by circulating a coolant such as propylene glycol anti freeze mixed with water through the object to be cooled, and then through a radiator, which removes heat from the coolant when air passes over it. Though it is called a radiator, radiative forcing represents only a small amount of the heat actucally removed. Thats why your car has a fan on the radiator. Now I understand this is a very special radiatorJjay is refering to, and I am looking into it now.

http://ntrs.nasa.gov/archive/nasa/ca...1979077159.pdf

Note the date...February 1964. This was very early in the development process. I found it interesting that the Mylar on the CM exterior was integrated into the design some time later, and was a main reason for the Launch Escape System being designed to completely cover the CM in the launch phase, to protect the CM surface thermal control covering.
Lots of interesting analysis of the problems here, problems that needed solutions.

I don't want to get caught up too much in this, but...

Interdimensional Warrior, some very lengthy posts on the subject were posted on pages 1 and 2. One of them by Jay Windley himself. You haven't said anything to this, but instead chose to respond to a personal attack.

You ask a number of questions, and multiple people respond to them in a very lengthy and detailed way. However, instead of responding to that you decide to respond to a person who has made a negative remark.

Of course, it's not nice to receive an ad hominem, but it's even more rude to completely ignore lengthy explanations and respond to the ad hominem instead.

I can see why you wanted a one-on-one discussion; it's quite easy to be distracted by unrelated things. Just don't get caught up in it too much, and you'll be fine and perhaps even getting some of the discussion you were looking for. As long as you don't avoid it, that is.

- Spread the Love


EDIT: Oh, sorry, I didn't see your post, two posts up.

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What I did say is that that process alone could not shed the heat produced by the equipment, the astonauts themselves and the effects of solar energy being absorbed by the spacecraft.

Can you show computations that prove that?

Remember, we are talking about a wide spectrum of energy coming from the Sun, reflective material is not sufficient to prevent heating.

Can you describe the "elementary physics" that proves the ineffectiveness of optical surfacing in thermal design? Can you attach actual numbers to the energy, reflection, and resultant heating?

...there is no escaping that a buildup of heat energy would occur that some process would be required to mitigate.

The basic nature of radiative heat transfer, especially as it relates absorption to emission, says otherwise. Heat does not continue to "build up" indefinitely.

I would also request he source his information, if possible, so a detailed review of it can be made.

You first.

One thing that has never been explained to me as of yet is why A13 would be cold when we all see a cooling apparatus was required during normal operation.

Because "normal operation" included the energization of electrical equipment, some of whose waste heat was introduced to the cabin. When that operation ceased on Apollo 13 because of the power-conservation measures, the existing heat in the cabin eventually radiated away into space and was not replaced.

How much heat did the electrical circuits that were lost or deactivated contribute to the overall heat budget of the spacecraft?

In terms of the ECS heat rejection capacity, the substantial majority of the heat load came from electronic equipment. In terms of heating cabin air, the primary source was waste heat tapped from the radiator inlet leg of he primary water-glycol coolant loop. Secondary sources included metabolic heat and direct solar heating of cabin surfaces.

Why would there be excessive heat from properly wired and installed electronics?

Why do you say the heat load from electronic equipment is "excessive?" What, in terms of numbers, is an appropriate heat load from 1960s/1970s electronic equipment of aerospace design? How did you compute or estimate it?

I know there would be a very minimal amount of heat produced, but it seems irrelevant in the overall heat budget.

How do you know that?

What we need to determine...

Shouldn't you have already done that before reaching a conclusion? There is no "we" on that question. You have the burden to prove your statement that the CSM thermal design would not have worked. You have made a number of specific (and often quantitative) claims with no supporting arguments. Until you supply the argument, no one is obliged to do your homework for you.

It is my contention that an object in space this near the Sun nomatter how well insulated internally will eventually heat up to an very uncomfortable level...

And it has been explained to you why that contention is not based on physical law. You now have the onus either to reconcile your claims with basic physics or to amend or withdraw them.

In my experience radiators work by circulating a coolant such as propylene glycol anti freeze mixed with water through the object to be cooled, and then through a radiator, which removes heat from the coolant when air passes over it.

The difference between an automotive "radiator" and a real radiator such as used in spacecraft has already been discussed.

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Be warned that you have just made a quantitative argument. Please be prepared to defend will it quantities, calculations, etc. Unless you can back up this claim with numbers, you have no argument at all.

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I found it interesting that the Mylar on the CM exterior was integrated into the design some time later...

The "heat shield" described in that paper is the ablative assembly of phenolic resin injected into steel honeycomb. This is the same layup that is used on the underside of the CM, but thinner for the upper structure. The heat-shield assembly indeed has terribly unfavorable optical properties for solar heating. In the final Apollo design, the lower heat shield was covered by its interface with the SM while the upper heat shield was covered with strips of aluminized Mylar and/or Kapton. In the Earth-orbit Skylab variant, the CM was painted in white thermal paint.

Lots of interesting analysis of the problems here, problems that needed solutions.

Yes. The purpose of this paper seems to be the partitioning and scoping of emerging thermal problems to be solved. It's an appropriate activity for that stage of spacecraft development.

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Properly installed electronics do produce considerable amounts of waste heat, try putting your hand on top of a CRT monitor or television that has been running for a while if you don't believe me, or better still try using a laptop computer actually on your lap while doing something fairly computationally intensive (3d games are a good choice) depending on the model they can heat up enough get quite uncomfortable.

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Properly installed electronics do produce considerable amounts of waste heat...

I built a high-performance computer in 2002 that required a heat-rejection capacity of just over 1 million BTU/h. It was "properly installed" and cruised at about 11 teraflops. Small change today. And equipment in the 1960s was not generally the low-power CMOS used in consumer electronics today, but instead power-hungry and heat-spewing TTL circuitry.

...try putting your hand on top of a CRT monitor or television that has been running for a while...

And imagine that there is no air to help cool it.

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I also made the mistake once of touching a bare Pentium Xeon under load. Second-degree burn. The thermal ramp rate for that component is 50 C /s.

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This all reminds me of the time at Foxtel playout centre when our TV equipment cooling system died. You would think that the gear would not produce that much heat, but within 10 minutes we were all basically stipped to under garments and dealing with cross-muxing (combining of channels onto one signal) of channels which was a hellraiser. Having the adult channels being viewable on a kid's channel frequency was not one of my more enjoyable nights. Thank goodness it was night, and the equipment area had huge doors which could allow a breeze inside. We were still operating in a 45 degrees celcius environment, but the muxing freakouts stopped. All the equipment was properly installed, and was nothing more than video relays and some playback tape machines.

I believe so. After all it isnt that complicated a problem.I know the alloys the various components were covered with and the level of finish as well as the surface area, so we can calculate fairly accurately the amount of energy over time that would be absorbed by the spacecraft, and likewise we can make fairly accurate calculations as to how much heat can be radiated by radiant conversion by the outside skin of the spacecraft. What we need obviously is more detailed heat budget information where the crafts' internal electronics and other hardware are concerned. I am certainly not thoroughly convinced either way, Jay, since you didn't source your cooling apparatus.



Actually I have no doubt of the effectiveness polishing a surface has in reflecting certain spectrum of EMR. What I am saying is , it's not just visable light, infared or ultraviolet radiation we are dealing with, it is a wide spectrum of frequencies of EMR and non EMR radiation, all of which can and do cause heating of metallic surfaces when impacting them.Polished surfaces get hot in the bright Sunlight, though aluminum more effectively radiates this heat buildup.The reason for this in the earths atmosphere is simple, because aluminum is such a good conductor of heat, it brings the heat to the surface efficiciently so it can be removed by air molecules passing over it, and by radiative forcing, of course.
In the relative vacuum of space, 'air cooling' is of course not a factor.
That's exactly what i said. it would reach a point of equilibrium, eventually. I suspect when we get done with the heat budget calculations on Apollo we will see that temperature will be quite high. First we need a source for your cooling apparatus or this thread is pretty much a waste of time.
I have no sources to quote. I am asking for a simple source of a description of the apparatus you said existed.
So by your estimation, the heat produced by the electronics was a major part of the heat budget. Interesting.
So you are saying that not only did the spacecrafts electronics need to be cooled, the spacecraft cabin had to be heated by re routing this heat into the cabin. Excuse me if something about that statement seems just a little odd. You are describing a complex cooling system that you never sourced. All I have is your word.
[QUOTE=JayUtah;1041285]
Why would there be excessive heat from properly wired and installed electronics?

Why do you say the heat load from electronic equipment is "excessive?" What, in terms of numbers, is an appropriate heat load from 1960s/1970s electronic equipment of aerospace design? How did you compute or estimate it?
[/QUOTE}
I can't. Not yet, I don't have crucial information.

That's why I asked you for the information neccessary to do so. I haven't proved anything one way or another , yet.

And I have a feelling you're not going to be able to provide me with the figures. If you can't you can hardly call yourself an expert. You should know approximately at least how much heat was produced by the electronics , I would think this would be a critical consideration in the design process.
When electronic circuits produce heat, that is a sign a percentage of the current flowing through the circuit is being converted to heat energy. This would be a complication in the spacecraft design and a totally unneccessary waste of energy. My guess is the circuits were very efficient and produced very little heat. There's no getting around the heat by product of electronic circuits, but it can be reduced to very low levels.
I have not reached a conclusion. I am simply representing the opposite side that you are in an open ended debate where neither one of us REALY have the answers. I made it clear the purpose of this thread was for my own question to be answered. It hasn't been.
The basic thermodynamic principals involved are not that complicated, but we have a few variables that we do not have values for that we need first to make meaningful conclusions. I have always been undecided on this particular arguement, though I think someone needs to ask hard questions.
One undeniable pattern is that the information I ask of you is never actually provided in a manner that would be helpful to my research.

Sir, with all due respect how do you know? A basic physical law of thermodynamics is that when as more heat energy is produced and absorbed into a system than can be radiated by it in a vacuum ,or removed by other processes, a rise in temperature will occur until a temperature where radiative forcing equals heat being produced and absorbed is reached .


An automotive radiator is not essentially different than the one you describe.The main difference of course is that air moves over the cars radiator and there is no air in space, so your radiator depends on shedding radiant heat and the cooling created by some as of yet unsubtantiated process.

If I understand your description like I think I do, it would work even in a vacuum In fact any experienced backyard mechanic will tell you a full radiator that is leaking coolant will cool BETTER so long as coolant is kept in it, because of the cooling effect of the evaporative process . SO what you describe is a radiator that uses the evaporative process for cooling the radiator, in the vacuum of space, correct?

What I need to know is two things.
1) How much heat was produced by the electronics under normal conditions.
2)How much heat could be removed by Jays' cooling apparatus.

Two unknown variables, without which we cannot continue.

Here is a rather detailed article on the Apollo ECS, including the cooling system (Note that this is a PDF):

http://ntrs.nasa.gov/archive/nasa/ca...1972012252.pdf

Enjoy!

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Don't forget the radiators in the service module.

But almost all of it is visible, IR, and some UV. See here:

http://en.wikipedia.org/wiki/Solar_r...Solar_constant

See the article I provided, or google "Apollo ECS".

How do you know that it is totally unnecessary?

That depends on the requirements and the available technology.

I'd have to disagree. I've seen a lot of information presented here on Apollo and have often used it as a launchpad for my own research. Nevertheless, it isn't our responsibility to do your research for claims that you have made.

What "unsubstantiated process" are you referring to? Heat rejection by radiation is an extremely well substantiated process, and you have already mentioned it yourself. Also, a "radiator" that works primarily using convection is quite different from a true radiator that works by radiation.

No! There is a glycol evaporator system in addition to the radiators for peak heat load situations, but the radiators are the primary heat rejection system. They work by radiation.

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Guessing is irrelevant. You simply need that to be the case for your argument to work.

Usually by putting large cooling systems in place. Even today a large amount of space and power in computers is devoted to cooling apparatus like fans and radiator plates, and my computer still gets very warm after a day in the office. It may be possible to engineer a component to produce very little heat, but if it is cheaper, quicker and easier to use an inefficient component that gets very hot and attach a cooling unit to it than to devote time and research to making a cooler component then that's what will be done. Apollo was done to meet a tight deadline, and the first priority for computers was to make sure they worked as computers, not to make sure they didn't emit heat.

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And besides that, it makes no sense to stuff a lot of time and money in making the computers more energy efficient when you need them not to be efficient.
Without the heat of the computers, you would have to add another system making everything even more complex, a heater....

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I would ask people, where possible, to allow Jay to answer by himself. He is more than capable of doing so. Yes, others amongst us can also answer, but lets leave it to Jay unless we feel there is an important point or issue to be raised.

Just because Jay has said he does not wish to exclude us, that does not mean we HAVE to post.

(Climbs off soapbox)

Thanks for listening.

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Actually Jason, the more heat that is produced by the electronics, the more likely I am right. I am suprised you didn't see that to be honest.


Jason, you fail to realize the enviroment you are refering to is quite different than the near vacuum of open space, and therefor totally irrelevant..

I tryed to download it twice, but failed.
I have a state of the art setup as far as my computer and it's software are concerned, I don't think the problem is on my end. I would really like to download it if possible.