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JimO
2003-Jan-25, 04:11 PM
In reviewing the aspects of HB hoaxing that can be verified in High Schools (and at home), I'm looking at the thermodynamics offered by 'self-taught physicist' Ralph Rene, and wanted to ask some basic questions.

In "NASA Mooned America" chapter 11 ("The LEM's Problem"), page 90-91 in my edition, he offers to calculate the equilibrium temperature of the LM on the lunar surface.

Solar heating is 1353 watts per square meter.

He assumes the LM sunlit area is 18 square meters.

"I have chosen an emissivity factor of 0.5 simply because that lies halfway between a perfect mirror and a perfect black body".

Thus he computes "12,168 watts per hour" (he frequently shows confusion over units).

Then he offers to compute the temperature at which the LM would be emitting this much heat (plus some from the crewmen and electronics). Using "the Stefan-Bolzmann formula", he computes a temperature of 120 deg C for the LM, at equilibrium.

"Did I miss something?" he asks. To start with, I'd suggest his absorption number (he states that absorption and emissivity values are the 'same number') of 0.5 is way too high.

What's the true 'equilibrium temperature' of the LM in space? Assume lighting angles as on the Moon.

In chapter 12 ("Blowholes of Sea & Space"), page 101, he gets even more amusing by calculating how the cooling water for the spacesuit sublimator was totally inadequate. He states that heat is rejected from the suit BY COOLING AND FREEZING WATER, so that each gram of water can account for so many calories from dropping to 0 deg C and then 80 calories for freezing (the 'heat of fusion', a term he does not use). He writes, "When that gram freezes it absorbs another 80 calories..."

Now, the physics I learned in High School is that water freezing 'gives off' heat to that amount (it resists cooling further until it is frozen solid). Rene seems to have it totally backwards -- the heat that a gram of water can dispose of is the calories absorbed when it rises from ambient to 100degC plus the heat of vaporization when it boils off. That value is about seven times the 'heat of fusion', so naturally a gram of water can cool a whole lot more than in the upside-down computations of our home-schooled 'physicist'.

Sure there is ice, since some of the water is 'over-cooled' by evaporation, but it then sublimates and absorbs heat just like it was supposed to. Any flecks of ice that get ejected with the water vapro stream are 'wasted' because they don't serve to cool the syste, -- sublimator or flash evaporator or water spray boiler, whatever it's called ("swamp cooler" in New Mexico).

I'm counting on High School physics teachers to be able to run through these numbers in a one-hour lecture, and to point to Rene's claims as a good example of 'intellectual over-reaching' that deserve laughs and giggles rather than credulity.

But first I wanted to run the numbers here to see if I've forgotten anything.

Glom
2003-Jan-25, 06:14 PM
"I have chosen an emissivity factor of 0.5 simply because that lies halfway between a perfect mirror and a perfect black body".


He doesn't seem to want to actually find out what the true value for the emissivity factor is.



Thus he computes "12,168 watts per hour"


That's not homogeneous.



Then he offers to compute the temperature at which the LM would be emitting this much heat (plus some from the crewmen and electronics). Using "the Stefan-Bolzmann formula", he computes a temperature of 120 deg C for the LM, at equilibrium.


First, isn't it Boltzmann. The value he calculates is correct for the values he cites, but is that a particularly high value?



Now, the physics I learned in High School is that water freezing 'gives off' heat to that amount (it resists cooling further until it is frozen solid).


Ooh! I remember this one. You're right.

I must admit, I am impressed with Rene for trying to actually put in some physics instead of just handwaving his arguments like everyone else, but it's a shame he doesn't take the time to learn the right physics.

JayUtah
2003-Jan-25, 06:58 PM
he [Ralph Rene] offers to calculate the equilibrium temperature of the LM on the lunar surface.

Uh, the LM did not have one single equilibrium temperature.

He assumes the LM sunlit area is 18 square meters.

You know, if you're going to prove (or even suggest) that something is bogus and someone is lying, assumptions just don't cut it. I have no idea what the sunlit area of the LM would be, but if I had to determine it, I'd certainly show my work.

The LM did not always land at a constant azimuth, and is variously illuminated on all the missions.

Thus he computes "12,168 watts per hour" (he frequently shows confusion over units).

As does Der Voron, another "genius" (I.Q. at least 160, he tells me) and "self-taught physicist." Units are everything in these types of computations. That's how you check your derivations. If you're trying to derive a computation that's supposed to give you an acceleration and the units come out to be "kilogram-liters per second" you know you've done something wrong.

Using "the Stefan-Bolzmann formula", he computes a temperature of 120 deg C for the LM, at equilibrium.

Stefan-Bolzmann, or the "fourth-power" law, is the correct equation, but since he's simply guessing at absorption and emissivity parameters he might as well be using the Pythagorean formula, or a rate of return on investment.

The LM was coated with different substances in different places. Those substances have entirely different thermal spectral properties. They have complex conductive and internally radiative relationships.

He's guessing at the values, simplifying the problem, and then coming up with some number.

To start with, I'd suggest his absorption number (he states that absorption and emissivity values are the 'same number') of 0.5 is way too high.

Yes, I heartily agree. Aluminum's absorptivity is about 0.05, with radiation in the 10 micron range. At equilibrium its emissivity is very low, therefore it will heat up.

Aluminized mylar has complicated radiant properties. The mylar itself has an emissivity of about 0.4. Put the mylar side out and see what happens.

What's the true 'equilibrium temperature' of the LM in space?

There is no one equilibrium temperature. Pick a point on the LM and then we can start talking about it.

jrkeller
2003-Jan-26, 12:29 AM
There's so much wrong with this I could spend all night working on this one. In the mean time, here are a few things that are blantantly wrong. No heat transfer person in their right mind would even do what he did. He's obviously not an expert. The worst heat transfer student I ever had would do a better job.

Jim, if you are looking for a good starting point, you might want to get the following NASA contractor report, "Development of a Computer Program External Radiation Absorbed by the Apollo Spacecraft," by Harold Finch and Duncan Sommerville of the Midwest Research Institute, MRI Project Number 2846-E

First, as Jay has previous stated one cannot lump the LM as a single uniform temperature object. There are criteria to do that. As us heat transfer folks call it the lumped parameter method. In the above mentioned report, NASA used about 300 surfaces to represent the LM ascent stage and about 100 to represent the lower stage. There just a lot more stuff on the ascent stage to worry about.

Second, even if one were to use Rene's very simple approach, while two surfaces are in the sunlight (one top and one side), there are at least three sides that are not illuminated and only view cold of deep space or the lunar surface.

Third, the angle of incident with the sun must be included as well. The only way his method works is if the incoming solar energy is perpendicular the absorbing surface. We all know that the LM landed a day or two after sunrise.

I'll get back to you with some really good stuff. All I can say is that Rene has ventured into a realm he knows nothings about.



<font size=-1>[ This Message was edited by: jrkeller on 2003-01-25 19:31 ]</font>

JayUtah
2003-Jan-26, 01:37 AM
There's so much wrong with this I could spend all night working on this one.

I know this is your field of expertise so I'm laying off on this a bit. I'd rather sit back and learn.

In the above mentioned report, NASA used about 300 surfaces to represent the LM ascent stage and about 100 to represent the lower stage.

It might not be obvious to people why you have to do this.

Objects than have many inside and outside corners formed by different substances will radiate and reflect heat to each other. So to determine its equilibrium, you have to account not only for radiation directly from the sun, but interreflection of heat from surfaces that sort of face each other. Obviously this depends on the distances and angles between them ("form factors").

The best way to solve this problem is to model the geometrical relationships of the important surfaces in a computer and simulate the reflection and radiation between them. Radiated energy depends on temperature, and temperature depends on radiation, so you have to iterate adaptively and wait for the feedback to converge.

... there are at least three sides that are not illuminated and only view cold of deep space or the lunar surface.

This is sort of what I was alluding to when I said there are complex heat transfer issues to consider, and not just the radiative kind. A surface will absorb a certain amount of energy and will re-emit a certain amount of energy, but equilibrium has to take into accout the energy that's carried away from that object by convection and conduction.

Take a cube of solid material and put it in in the sun, and it won't be isothermal (the same temperature all over). You'll have gradients.

Third, the angle of incident with the sun must be included as well.

This is the other reason why the precise geometry of the object must be accounted for.

Apollo 11 landed when the sun was approximately 10&deg; above the theoretical horizon. The aluminum skin of the aft equipment bay, a broad expanse of vertical surface at the back of the ascent stage, would be the worst case for absorption.

Compare that to the inside of the footpads, covered in H-film and aluminized mylar, but with the sun striking it at about 10&deg;.

And as long as we're being rigorous, think again of the back of the ascent stage. Not only does it absorb energy directly from the sun, it will absorb energy reflected and emitted by the lunar surface. The lower part of that panel is closer to the lunar surface (remember the inverse square law) but "sees" the surface at a lower angle. The upper part of the panel is farther away, but more perpendicular.

In a serious, iterative solution you would probably break up that one flat panel into several subdivided areas, each of which has its own properties with respect to radiative heat transfer. Even that one panel wouldn't necessarily be the same temperature at every point along the surface.

Ideally what we'd see is one of those really cool color-coded pictures that shows the equilibrium temperature at each point on the spacecraft.

All I can say is that Rene has ventured into a realm he knows nothings about.

I can't agree more, but keep in mind that Rene's intended audience knows much less than he does about any of it. They aren't in a position to question him, even if they were motivated to.

jrkeller
2003-Jan-26, 02:55 AM
What I'll do post a series of messages to refute and attempt to explain what Rene did and what he should have done.

About the only thing right that Rene did was to assume that a steady-state condition existed. This is actually a good assumption, since the environment on the moon changes very slowly. This is a common practice here at NASA. I'd say it is the standard practice for evaluting the temperature of objects on the moon. Using steady state analyses verses time dependant analysis method saves a lot of computer time.

Rene's first mistake was to assume that the LM is at a uniform temperature. This is an exceeding poor assumption and is only reserved for small objects like a small metal ball on the order of a quarter inch or less. Also, this assumption usually implies a regular shaped object like a sphere or cylinder. Ball bearings and powered electrical wires can be evaluated this way. When the objects becomes more complex with multiple surfaces, say something even as simple as a rectangular oven, there is interaction between the surfaces. In other words, the temperature of one surface effects the temperature of all the others.

The problem with Rene's simple analysis method is that the LM is an extremely complex object, at least from a heat transfer analysis point of view. It has numerous surfaces, many oddly shaped, which transfer heat to each other and well as deep space and the lunar surface. This is futher influenced by how the LM is orientated on the lunar surface. Furthermore, the solar energy is absorbed by many but not all of the LM surfaces and they all don't absorb solar energy equally.(another topic).

To solve a problem of this nature, a heat transfer analyst divides the object in question into many smaller regular surfaces. This division of the object, it called nodalization in the heat transfer world. It takes lots of skill, lots of experience and a bit of intuition to correctly nodalize the object. To make the problem just a bit more enjoyable, conduction between each adjoining surface (node) is also added. In the case of the LM, there is convection (air flow) within its cabin which also must be accounted for.
Needless to say, a computer program is needed to accomplish this task.

As I said early, no heat transfer analyst would ever take the Rene approach. Those that do wouldn't be employed long.

For further reading see,

http://www.amazon.com/exec/obidos/tg/detail/-/1560328398/qid=1043548862/sr=1-1/ref=sr_1_1/002-3201458-0960855?v=glance&s=books

Notice that this book is 864 pages long.

JayUtah
2003-Jan-26, 04:06 AM
I'd say it is the standard practice for evaluting the temperature of objects on the moon.

And this would work even in the J-missions where the sun angles changed several degrees during the astronauts' sojourn. The thermal state wouldn't lag behind the change in sun angle. But it's important to recall that the thermal state right after touchdown would not be expected to match exactly the thermal state just prior to liftoff. But see below.

Using steady state analyses verses time dependant analysis method saves a lot of computer time.

As a provider of such computer time, I can testify to how important that is.

This is an exceeding poor assumption ...

You're being kind: it's a monumentally stupid assumption. /phpBB/images/smiles/icon_smile.gif

Furthermore, the solar energy is absorbed by many but not all of the LM surfaces and they all don't absorb solar energy equally.

In another thread I mentioned the hypergols, which like to be at about room temperature. Hence the different colored panels on the bulbous ascent stage tank housings. Grumman paid very careful attention to the thermal properties of their spacecraft. I have in my possession a smattering of drawings diagrams showing some of the thermal design of the LM's skin.

To solve a problem of this nature, a heat transfer analyst divides the object in question into many smaller regular surfaces.

This is what I was trying to describe above about the aft equipment cover.

It takes lots of skill, lots of experience and a bit of intuition to correctly nodalize the object.

Question: Is there any reliability in an adaptive nodalization performed automatically to refine that suggested by the analyst?

Specifically, let's take the example of the aft equipment bay cover. Someone may naively nodalize that surface as a single node. Could a computer algorithm subdivide it based on inferences from its geometry (e.g., just split it in fourths or something by bisecting it along its principal axes), perform one pass of the transfer modeling, and attempt to see from a first-order approximation whether that subidivision is warranted?

Let's say you had an abundance of computing power and a need to be fairly accurate. Do you know of any theoretical barrier to this refinement?

Intuition says that you should nodalize finely in, say, the gutters of inside corners where two planar surfaces join, if that kind of accuracy were important. But would it be possible to hand a computer the two planar surfaces and have it determine how likely a subdivision of either will improve the results?

Yes, yes, more CPU cycles.

In the case of the LM, there is convection (air flow) within its cabin which also must be accounted for.

Ah, but interestingly only sometimes. When the astronauts are outside, there's no air. When they're inside, there's air.

And when it's there, it's forced convection. There are fans blowing the air around. Not to mention that the temperature of the air is controlled by a separate system that adds or removes heat as required. So not only does convection complicate the thermal analysis, it's not even typical convection.

Those that do wouldn't be employed long.

Not as engineers, perhaps, but maybe as conspiracy theorists.

Let's be charitable; most people didn't learn anything like this in high school. Most of the world operates according to the maxim, "Things left out in the sun get hot." Anything beyond that is rocket science. And it's important to realize that for most people, this is a perfectly workable level of understanding.

This is what makes conspiracism such an easy way to make a buck. Take an audience full of people, pretend to educate them a bit, throw around a few fancy words like "emissivity" and "Stefan-Bolzmann", give 'em the old razzle-dazzle, and then declare yourself much more clever than NASA. It doesn't matter whether you've explained radiant heat transfer correctly. It only matters whether you've told a good story and used plenty of scientific-sounding words.

Dispelling the bunk sometimes requires -- as it does in this case -- explaining something that's quite complicated. That's not nearly as exciting as lurid tales of government coverup. And that's why people buy Ralph Rene's book. They don't give a rat's behind about radiative heat transfer, and likely they'll skip over that part, confident in the idea that Rene has proved his case.

Radiative heat transfer? The guy can't even get pi right.

johnwitts
2003-Jan-26, 02:48 PM
HBs often think that the LM had a single skin (the CM too for that matter), so that if you pressed your hand against the inside of the spacecraft, your hand would be just the other side of the skin that you can see from the outside. In reality, the crew compartment was 'embedded' within the structure with layers and spaces in between the inner and outer skin.

Things left out in the sun get hot. Anyone who has a car knows this. On a summers day, the inside can be like an oven. The 'skin' of the car on the ouside is also the 'skin' on the inside. Now if we take our car sat in the sunshine, wrap some blankets round it to cover it, then wrap the whole thing in aluminium cooking foil, you get something more like how the LM was constructed. How hot would the inside of the car get?

I've used this method while camping in hot countries. UK tents are dark coloured, cos it's always cold here. European tents are all silver coloured because they get more sunshine. When abroad, the duvets we use to keep warm on the way down Europe are used to keep the tent cool in the hotter places. I throw the duvets over the tent and tie them in place. I then cover the whole thing with a silvery plastic car cover to keep it all dry and in place out of the wind. The result is that our tent is pretty much the coolest place on the campsite. These coverings also protect against radiation and micrometeorite impacts. /phpBB/images/smiles/icon_smile.gif

This Is Your Brain On FOX
2003-Jan-26, 11:40 PM
Wow, that guy is worse than some of the creationist 'geologists' and 'biochemists' I have encountered

calliarcale
2003-Jan-27, 05:09 PM
Awesome! I love basking in the knowledge of some of the folks here. /phpBB/images/smiles/icon_wink.gif

I still can't understand why Rene thinks the LM (and CSM, and EMU, etc) has to be isothermal. Hasn't he ever burned anything in the oven?

For a great demonstration of how things don't heat up uniformly when the heat is coming from only one direction, try putting a steak under the broiler on full blast for a few minutes. It'll be well done on top and rare on the bottom, even if the oven has had time to warm up completely inside. I'm very familiar with this property, having on several occasions forgotten to change the oven from "preheat" to "bake". /phpBB/images/smiles/icon_razz.gif (Preheat is a more direct heat, similar to how the broiler works. Bake relies more on maintaining the temperature inside the oven, although of course you'll still find the food getting more cooked on the side nearest the heat source.)

darkhunter
2003-Jan-27, 06:58 PM
On 2003-01-27 12:09, calliarcale wrote:
Awesome! I love basking in the knowledge of some of the folks here. /phpBB/images/smiles/icon_wink.gif

I still can't understand why Rene thinks the LM (and CSM, and EMU, etc) has to be isothermal. Hasn't he ever burned anything in the oven?

For a great demonstration of how things don't heat up uniformly when the heat is coming from only one direction, try putting a steak under the broiler on full blast for a few minutes. It'll be well done on top and rare on the bottom, even if the oven has had time to warm up completely inside. I'm very familiar with this property, having on several occasions forgotten to change the oven from "preheat" to "bake". /phpBB/images/smiles/icon_razz.gif (Preheat is a more direct heat, similar to how the broiler works. Bake relies more on maintaining the temperature inside the oven, although of course you'll still find the food getting more cooked on the side nearest the heat source.)


Yep--my works the same way--put two identical pizzas in, and unless I keep an eye out, the bottom one burns and the top one ends up half raw....

JayUtah
2003-Jan-27, 07:03 PM
I still can't understand why Rene thinks the LM (and CSM, and EMU, etc) has to be isothermal.

Because that's the difference between someone who can look up equations in a book or on the web, and someone who has studied thermodynamics and can apply knowledge of it to real-world problems.

My oven has a "preheat" setting. It simply turns on both top and bottom elements to more quickly transfer heat to the air and inner walls of the oven. I don't use it, precisely because I forget to turn it to "bake".

The idea that materials and coatings were specifically chosen for absorptive and emissive properties is key to understanding the design of the lunar module. But still, the concept of a temperature gradient is so fundamental and so basic to the study of heat transfer that I can't imagine anyone like Rene not understanding it, yet claiming any sort of expert knowledge.

This is akin to a carpenter hammering with the claw end of the hammer. You kind of get the idea he doesn't know a darn thing, but just looks good in overalls. (And I've seen Rene; he doesn't look good in overalls.)

As I said above, he doesn't have to fool experts. He knows he can't. He just has to fool the masses into shelling out a few bucks for his book, hailing him as a hero, and writing glowing reviews.

jrkeller
2003-Jan-27, 08:15 PM
The thing that struck me more than Rene's use of a uniform temperature to evaluate the LM's equilibrium is his use of a single value for the emissivity. I don't know if he did this deliberately to get the answer he wanted or just didn't know what any better.

Just a little background information here. All objects absorb thermal radiation from other objects and emit thermal radiation as well. The term emissivity comes from emit and is the percentage of thermal radiation compared to an ideal situation, called a black body. The emissivity of an object is typically a function of the material and the temperature it is at. For most materials, the emissivity is constant from 0-400F.

Another equally important thermal radiation property is called absorptivity. It is defined as the percentage of thermal radiation an object absorbs from another object. Absorptivity is a function of several factors. It is a function of the receiving material and its operating temperature, but it is also a function of the temperature of the object that sends the thermal radiation. In actuality, it is a function of the wavelength of the incoming radiation, however, since the emitted wavelength and temperature are related (Wein's Law), I find it easily for most people to remember temperature.

Going to the following website which was lifted from a NASA report,

http://www.tak2000.com/data/finish.htm

clearly shows that using a constant properties is also a very bad assumption.

Another nice site which explains in some detail, how coatings are used to reduce or increase thermal radiative heat transfer is found here.

http://klabs.org/DEI/References/design_guidelines/design_series/1239.pdf

In summary, when Rene made his calculation to determine the equilibrium temperature of the LM, he needed to use a value that reflects the true percentage of absorbed solar energy and the percentage of black body heat rejection. Any heat transfer book at any library I've ever been too, contains tables of emissivity and absorptivity.

According to Jim "Did I miss something?" he asks. You bet. Just about everything related to radiative heat transfer.

Since Rene is a "Self-taught physicist" he should have know about Maxwell relationships for determining the emissivity and absorptivity of some materials like metals and dielectrics. He could have estimated the theoretical values and then done the calculation. Of course some of the equations use the accepted value of PI and I guess he figured that they must be wrong.

More to follow.


<font size=-1>[ This Message was edited by: jrkeller on 2003-01-27 15:18 ]</font>

calliarcale
2003-Jan-27, 10:57 PM
Regarding his use of a single value for emmissivity, even a clueless novice like me can see it's bunk because he makes a point of saying that he's assumming it. He gives no background as to *why* he's made this particular assumption, so the only conclusion we can make is that he doesn't know and is just making it up as he goes along.

Which, come to think of it, is precisely what he is doing....

Jim
2003-Jan-28, 01:18 PM
Just to add my penny's worth (probably not two pennies' worth, but...):

"I have chosen an emissivity factor of 0.5 simply because that lies halfway between a perfect mirror and a perfect black body".

and

"Did I miss something?" he asks. ... (he states that absorption and emissivity values are the 'same number') ...

Rene is trying to use Kirchkoff's Law, that emissivity and absorbtivity are equal. Unfortunately, this is true for only a small number of materials... and certainly untrue for the materials used on the LM (aluminized Mylar, white paint...).

The "trick" is to maximize the emissivity (heat being radiated) and minimize the abosrbtivity (heat being retained). Any heat transfer engineer would know this and would never willingly choose a material with equal e and a when an alternative exists.

Bad first assumption = bad result. (Garbage in = garbage out.)

Here's a neat primer on thermal control of space vehicles specifically, with diagrams and e/a tables:
http://faculty.erau.edu/ericksol/courses/sp300/ch10/thermal_ch10.html
(I'm guessing Rene hasn't read it.)

_________________
<font color=000099>Never attribute to malice what can be adequately explained by ignorance or stupidity.</font>
Isaac Asimov

<font size=-1>[ This Message was edited by: Jim on 2003-01-28 08:19 ]</font>

calliarcale
2003-Jan-29, 04:18 PM
On 2003-01-28 08:18, Jim wrote:
Bad first assumption = bad result. (Garbage in = garbage out.)


Reminds me of a great Charles Babbage quote that I saw on the 'net once and now have in my quotefile. (For those who don't know, Babbage was the guy who built the famous steam-driven calculator, the Difference Engine, in the 19th Century. He was working on its successor, the Analytical Engine, which would have been the world's first general-purpose computer had he ever managed to scrounge up enough funding.)

On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question.

JayUtah
2003-Jan-29, 06:32 PM
If you burned garbage in the boiler that generated the steam, would incorrect results be produced?

Babbage's quote is legendary in the computing field, and is often cited by other scientifically-minded people in support of arguments that legislative bodies in general lack a certain connection with reality.

JimO
2003-Jan-29, 06:37 PM
But I'm still faced with the original problem -- if somebody were to make realistic average estimates for absorbtivity and emissivity and area, what would some justifiable ranges be, and what ranges of 'equilibrium temperature' would they provide?

Guessing 0.5 because it's in the middle is obviously deceitful, but if we guessed absorbtivity of 0.2 and emissivity of -- what? -- and also radiating surface three times absorbing surface, and given a known solar constant (even with an offset angle of 20 degrees the cosine effect is small), do we get a LM stable temp that's "cold"? I'd sure hope so.

Moose
2003-Jan-29, 07:18 PM
On 2003-01-29 13:32, JayUtah wrote:
If you burned garbage in the boiler that generated the steam, would incorrect results be produced?


I'm not sure your analogy holds very well JayUtah.

x + y = 5 when x = 2 and y = 3.

If you typo and set x = 3 and y = 2, you get a deceptively compatible answer for incorrect values. (The next use of x and y may not be so compatible.)

Whereas if you set x = 3 and y = 42, your answer is outright incorrect.

In the case of the steam engine, garbage may or may not provide enough heat to generate steam, but might generate too little or too much heat such that it damages the engine or related systems. (For example: enough to boil water but not enough to keep high-temp lubrication hot enough to be properly viscous.)

In computing, the right answer with the wrong data is still problematic.

calliarcale
2003-Jan-29, 07:32 PM
On 2003-01-29 13:37, JimO wrote:
Guessing 0.5 because it's in the middle is obviously deceitful....

I was telling my husband about this on the way to work this morning. (We are lucky -- or unlucky -- enough to work at the same company.) He just laughed. /phpBB/images/smiles/icon_razz.gif

Then we got into a discussion about the time I tried to cook salmon and forgot to change the oven from "preheat" to "bake". I had also (for reasons unknown to me now) opted to cook the salmon skin-side-up. I can tell you that the smell of burned fish scales is definitely one to avoid! /phpBB/images/smiles/icon_biggrin.gif

JayUtah
2003-Jan-29, 09:55 PM
JimO, any single-value estimate would be misleading, and it will be hard to get an engineer to stand behind one. Rene's method is the real villain. He's taking a very naive, simplistic approach to solving what is inherently a very difficult problem.

The secondary problem is his guess of initial parameters. Obviously Rene's guess proves nothing, but we don't improve the situation by plugging more realistic values for emissivity and absorptivity into a computational method we know to be flawed. This tacitly validates the method.

Obviously the strongest approach would be a reasonably thorough thermal analysis of the lunar module. But I don't know of anyone that would undertake that just for the fun of it. With any luck, existing analyses may prove sufficient.

This is how conspiracists deftly shift the burden of proof. They come up with a cockamamie solution that appears valid and produces dire results, perhaps knowing full well that it won't stand up to rigorous scrutiny. And so you can point out all that's wrong with it, but the seeds of doubt have been sown. They can only be uprooted by performing the lengthy, costly analysis according to appropriate methods that -- in the final summation -- conveys very little to the layman.

Another approach then is to instill critical thinking into the layman. Point out that the method is wrong (describing the correct method) and that the initial estimate is just a guess. Ask how likely it is that such a procedure will arrive at a real answer.

Is this handwaving? No. There's no evasion in pointing out the absurdity in a naive estimate.

JimO
2003-Jan-29, 10:03 PM
Everything you say is true -- and also is the reason our side often loses arguments in front of an intelligent but uninformed audience.

How about just doing a parametric study to show how sensitive the answer is to initial conditions? After all, it's his 'calculation' that must be discredited.

What would be the results, EVEN granting all his simplifying assumptions, if you made a MORE (but still partially) realistic set of 'assumptions':


Absorbtivity of 0.2, say..

Emissivity of still 0.5 (HIS figure)..

Solar constant -- give him that.

Area of heating -- OK, let him have it.

Area of radiation -- THREE sides, not just one. So 3x his value.

What pseudo-temperature does THAT provide?

JayUtah
2003-Jan-29, 11:24 PM
I sympathize with your plight. I'm in the same boat. Do I give people the equivalent of an engineering education or do I gloss over the details? I don't have the answer.

I feel strongly that the reader needs to come away understanding that you could place a thermometer at various places on the LM and come up with temperatures from -200 F to 150 F or so -- and that this is perfectly okay. This can be established informally. Most people understand that grass feels cooler to bare feet in summer than sand or asphalt. They don't have to understand necessarily why, just that it happens that way.

A parametric analysis would be a suitable way to address Rene's arbitrary choice of radiation parameters. The most vulnerable parts of any argument are the admitted guesses. And I think that would be valid even in Rene's uselessly simplified method. Showing a simple table of "estimated" temperatures versus guesses for alpha and epsilon might show that the estimation is useless.

I'm less excited about the Slightly More Sophisticated Approximation because it still sidesteps important issues like radiation between mutually-visible nodes and the angles of irradiation. Perhaps I've got my engineer hat on too snugly, but to me these are too important to ignore.

If you present such a model quantitatively, it will soon be reported in conspiracist circles that, "NASA engineer James Oberg computed the lunar module temperature as XXX degrees," and that becomes the basis for a straw man. If, say, you compute a singular LM equilibrium temperature at 150 F, and someone points out that some piece of LM equipment or provisions becomes unusable at 90 F, that's just more to explain.

But all is not lost. It might be useful to introduce the concept of the complexity of radiant heat transfer by use of a simple cubical example of a known material, on the lunar surface. You could point out the difference in angles, the difference between light and shadow, and then apply those concepts to the lunar module. If the reader sees that the LM is an unwieldy problem for radiant heat transfer, he might be persuaded to conclude that Rene's estimate is as thoroughly absurd as it is. And he might also be persuaded to understand why you don't want to attempt a thorough "authoritative" answer.

Telling a reader something is complicated is fairly unsatisfying. Giving him a glimpse of that complexity is more satisfying.

Perhaps I'm just a demanding individual, but I see little value in validating any of Rene's estimated values. So much of this conspiracy nonsense is based on numbers plucked out of thin air that I usually demand conspiracists justify their estimates.

jrkeller
2003-Jan-30, 04:00 AM
I think to solve this problem, it would be best to state from basic principles. The first thing to do is apply the first law of thermodynamics, which is the conservation of energy. For a steady-state system

Qin = Qout

where Qin is the amount of heat into the LM and Qout is the amount of heat rejection by the LM.

The amount of Qin is equal to the solar flux, multiplied by the illuminated area, multiplied by the absorptivity. So we get

a(Area Illuminated)Qsolar = Qout

Here is one part of the equation where Rene has again fallen flat on his backside. The area term is not the total surface area or even the total surface area illuminated, but it is the illuminated surface area multiplied by cosine of the angle between the incoming rays and the normal to the surface.

To determine Qout, the heat rejection, one can apply the Stefan Boltzman equation, which states that the heat emitted is equal to the emissivity multipled by the total surface area, multipled by the Stefan-Boltzmann constant, multipled by the temperature difference between the object temperature raised to the fourth power and the temperature of the surroundings raised to the fourth power. Therefore,

Qout = e (Total Surface Area) SB [(Tobject)4 - (Tsurroundings)4]

Again we see that Rene has screwed up again. The temperature of the lunar environment is not absolute zero.

If I rewrite the equations I get,


a(Area Illuminated)Qsolar = e (Total Surface Area) SB [(Tobject)4 - (Tsurroundings)4]

To get the answer that Rene got, he made three wrong assumptions.

1) Illuminated area is equal to total surface area. Absolutely false. This is impossible for a three dimensional object.

2) The temperature of the surroundings are at absolute zero.

3) The emissivity and absorptivity are equal. Real materials don't behave this way, except for a very few materials. The material on the LM is probably mylar with a gold finish. Very good for keeping things cool.

JimO hope this helps.



<font size=-1>[ This Message was edited by: jrkeller on 2003-01-29 23:00 ]</font>

SAMU
2003-Jan-30, 07:17 AM
On 2003-01-29 18:24, JayUtah wrote:


If you present such a model quantitatively, it will soon be reported in conspiracist circles that, "NASA engineer James Oberg computed the lunar module temperature as XXX degrees," and that becomes the basis for a straw man.



Is that not "Attacking your opponent's position without asserting a position of your own."?
You are then vulnerable to reversing the situation where you are thrashing his "straw man".

calliarcale
2003-Jan-30, 03:51 PM
On 2003-01-29 18:24, JayUtah wrote:
I sympathize with your plight. I'm in the same boat. Do I give people the equivalent of an engineering education or do I gloss over the details? I don't have the answer.


I think the answer is to give them a real-world example of why the basic reasoning is wrong. You can't give them an engineering education, and it's dangerous to gloss over details, but you *can* give them enough to see why Rene's approach is wrong.

It's the same technique used so often on children's science shows -- find a real-world example to answer the question. Think of yourself as Beakman. /phpBB/images/smiles/icon_razz.gif

So in this case, the fundamental problems with Rene's argument are: 1) absorptivity and emissivity are not the same thing, 2) assuming 0.5 is essentially picking a nubmer halfway between nothing and everything and that's just a wild guess, and 3) things don't heat evenly.

Some real-life examples that work with common sense to debunk Rene's method are:

1) Absorptivity is how much heat a thing absorbs, and reflectivity is how much it reflects. Why does a pan in the oven get hot faster than the food inside of it? Why does Reynold's Wrap let things cook without burning? Why does your seat-belt buckle burn your hand in the summer but the seat-belt webbing doesn't?

An extension of the aluminum foil thing is to ask a person: if Reynold's Wrap keeps your pie crust from burning on top, what would happen if there was no air in your oven? Would the pie get done? What if you replace the Reynold's Wrap with something that doesn't reflect much heat but absorbs a lot?

2) Guessing 0.5 for emissivity is guessing a value halfway between nothing and everything. This is like knowing that your car can hold twenty gallons of gas and then assuming that it has ten gallons (halfway between nothing and everything) in it without looking at the gauge. Is it a good idea to make this assumption and then head off on a two hundred mile drive in the wilderness, or should you check the fuel gauge first?

3) Things don't heat evenly, so Rene is wrong to assume that the entire LM would heat evenly. On a hot summer day, touch the side of your car that is in the sun. Then touch the side that is in the shade. Are they the same? Which is hotter? Going back to the Reynold's Wrap example above, you can put a sheet of Reynold's Wrap over sandwiches or pies when you back them to keep the top from burning. Why would the top burn without the aluminum foil draped over it? What heats up the pie if the foil is keeping so much of the radiative heat away from the top crust? Going back to the though exercise above, what would happen if there was no air in your oven, as there is no air on the Moon?

I guess this becomes an excersize in teaching critical thinking. /phpBB/images/smiles/icon_wink.gif But I like to try to find real-world examples because it helps people to understand based on things that they're already familiar with. They don't need to know the nitty-gritty of engineering to understand why Rene is wrong. I'm a software engineer; I don't understand a lot of the nitty-gritty of thermodynamics myself because it isn't my field. But that doesn't mean I can't tell that Rene is talking **. /phpBB/images/smiles/icon_wink.gif

Thumper
2003-Jan-30, 04:19 PM
But I like to try to find real-world examples because it helps people to understand based on things that they're already familiar with.

I like this approach. I think it works well for adult learners who are not particularly technically trained. I think the BA does a wonderful job of this in his book. He starts out explaining as simple as he can, a topic or process, using a real world familiar example. Then he adds in some complicating elements one by one in hopes the reader figures out, "Hey, there's alot of things going on here." But they don't forget the original simplified example.

I do see Jay's concern however, that simplifying the engineering can be heading down a slippery slope. You'd have to be clear that you were giving a simplified example of something and not representing it as the actual process or solution.

JayUtah
2003-Jan-30, 04:47 PM
Simplification per se is essential. Nobody would learn anything otherwise.

I have a problem with simplification applied to a real-world situation in a context where the resulting inaccuracy would raise questions. Conveying information for purposes of education is one thing. Conveying information intended to debunk a theory is quite another: debunking is closer to a court case where the least error can often compromise an otherwise valid point.

JimO
2003-Jan-30, 04:55 PM
What I'd like to show is how sensitive the answer is to the assumptions, by running the same 'pseudo-calculation' with other assumptions one can argue are more realistic, if still not totally realistic.

calliarcale
2003-Jan-30, 04:58 PM
That's very true. I guess I wasn't talking about legal-level debunking but simply about educating the general public. What to say when you meet an average Joe who has been suckered in by the Fox special or Sibrel's flick or one of those.

For serious debunking, obviously you need to get technical. But then comes the question of whom you're actually trying to convince with the debunking. Most of the people who will understand the technical debunking already know why this stuff is bunk. The rest are the people spouting the bunk, and they have reached that peculiar place in their minds where they will not accept anything that contradicts their beliefs. Because that's what it comes down to -- they believe that Apollo was a fraud, and they believe it so firmly that anything contradicting it must be wrong.

I know one guy who believes Apollo was hoaxed simply out of spite. /phpBB/images/smiles/icon_frown.gif It's very sad. He literally hates the government, and literally hates science. He'll swallow anything that makes them look foolish. I've tried the common-sense critical-thinking debunking and I've tried the deeply technical debunking. When I gave him the deeply technical reason why the crosshairs in the Apollo pictures don't show evidence of a hoax, he didn't have an answer. But that didn't bother him. He just assumed that even though he couldn't see what was wrong with my logic, something had to be wrong, because he *knew* Apollo was hoaxed.

He was the first moon hoax proponent I met in my personal life. What's more, he was a friend before that episode. He isn't anymore, though I am civil to him for my husband's sake and for the sake of the rock band we all belong to.

Thumper
2003-Jan-30, 05:14 PM
Maybe you should ask your friend what his life would be like if there was no government and there was no scientific discoveries. I know, this is probably a usless exercise to someone so filled with anger. It sounds like a sad case.

As to what Jay said about official debunking, I agree:
If your goal is to enlighten or educate the average person, you could use much less detail in your discussions. While presenting a case or arguement for public scrutiny would certainly require accurate and very technical evidence if you had any hope for it to stand up.

jrkeller
2003-Jan-30, 05:26 PM
On 2003-01-30 11:55, JimO wrote:

What I'd like to show is how sensitive the answer is to the assumptions, by running the same 'pseudo-calculation' with other assumptions one can argue are more realistic, if still not totally realistic.





I can make you an Excel spreadsheet model, if you'd like. Shouldn't take more than an hour or so.

JimO
2003-Jan-30, 06:46 PM
Since I expect to 'do good' with this information (and lord knows i'm not getting rich on it), I'd appreciate such results very much -- but no hurry. I'm cutting back hours on the writing until I settle a writing contract.

Irishman
2003-Jan-31, 02:02 PM
Some very good points in this thread.

One thing about presenting a simplified version to explain something detailed, Jay is right. It's like analogies. People make analogies all the time to convey meaning. But most analogies are not perfect corollaries. Just because they share one similarity does not make them identical. An analogy only has to have similarity in the aspect in which you are comparing the two issues.

This is fine when you are just trying to educate. But when you are arguing a point, the analogy is quickly hammered by people extending it beyond your intended comparison and then calling the analogy flawed. Of course it's flawed when you go beyond the limited zone of comparison I was using, because the two cases are not identical, they're only similar. Often the offender refuses to accept they are overextending the analogy.

However, something else peaks my interest on this point. I've run across several complaints against "things we learned in school that are wrong" applied to science. These sometimes boil down to simplifications made in the explanation process to reach a younger audience without the full technical background, but the simplification becoming the bedrock of understanding and later you have to get over the simplification.

GrapesOfWrath
2003-Jan-31, 02:12 PM
On 2003-01-31 09:02, Irishman wrote:
However, something else peaks my interest on this point. I've run across several complaints against "things we learned in school that are wrong" applied to science. These sometimes boil down to simplifications made in the explanation process to reach a younger audience without the full technical background, but the simplification becoming the bedrock of understanding and later you have to get over the simplification.

Worse, sometimes a simplified explanation is misunderstood, and someone grows up believing that that is how the world works, and that their teacher is to blame for the misinformation. OK, sometimes the teacher takes that first step, but the end result is that the student blames the science establishment for the "lie."

BTW, it's "piques", unless you're saying that this is your number one fascination. /phpBB/images/smiles/icon_smile.gif

CJSF
2003-Jan-31, 02:42 PM
On 2003-01-31 09:12, GrapesOfWrath wrote:
Worse, sometimes a simplified explanation is misunderstood, and someone grows up believing that that is how the world works, and that their teacher is to blame for the misinformation.


Like the raging debates we've had in the past on the "baloon analogy" and such? Has anyone heard from old JW in a while?

CJSF

poorleno
2003-Jan-31, 09:52 PM
on a different note, does anyone know if there are any publications (partial or not) of this rene guy online? I'm not spending a dime to read some psychopaths confused babble, but it might prove fun to disprove some specific 'theories' in class.

Zathras
2003-Jan-31, 11:16 PM
On 2003-01-31 16:52, poorleno wrote:
on a different note, does anyone know if there are any publications (partial or not) of this rene guy online? I'm not spending a dime to read some psychopaths confused babble, but it might prove fun to disprove some specific 'theories' in class.



Start with his website:
http://www.rene-r.com/

Irishman
2003-Feb-01, 10:30 AM
The Balloon Analogy! That's the one I was trying to remember. I knew we had gone around and around over something here and just couldn't recall what the topic was. That's a perfect example of what I meant.

"But it's an analogy!" /phpBB/images/smiles/icon_wink.gif

poorleno
2003-Feb-01, 11:07 AM
Start with his website:
http://www.rene-r.com/


No examples there :[ Just big tabloids like
- "I'll sell you the correct PI some whatshisname discovered for 6 bucks!!!"

jrkeller
2003-Feb-27, 02:55 PM
Jim O,

You might try this website. It's got a nice summary of thermal radiant barriers. Again, I think all this folks would have to be in a the hoax.

http://www.spacetechhalloffame.org/inductees.cfm?view=2&id=25