On UCLA’s main website there is a ‘space missions’ page. On it there is a section for the Diviner mission, which mapped the Moon’s surface temperature. We covered it in a series of posts a while back, as it is crucial to our understanding of Earth’s climate:
Diviner: The Diviner Lunar Radiometer is one of seven instruments aboard NASA’s Lunar Reconnaissance Orbiter spacecraft, which was launched on June 18, 2009. It is the first instrument to create detailed, global maps of surface temperature over the lunar day and year. Diviner’s measurements are also used to map compositional variations, derive subsurface temperatures, assess the stability of potential polar ice deposits, and infer landing hazards such as roughness and rock abundance. Read more here.
But the links to the diviner subdomain are broken, and although references to other pages about the mission such as press releases and news articles are found by searching the UCLA site, the science has gone. OK, so websites get changed, links get broken, servers crash and don’t get rebooted for a while. So what? Why does this matter?
Vavasada et al 2012 J. Geophys. Res., 117, E00H18, 2012.
It matters because the results that Diviner produced enabled Dr Ashwin Vavasada et al to calculate an average surface temperature for the Moon’s equatorial band of 214.4K. Tim Channon then built a very neat model to replicate the Vavasada result. Ned Nikolov showed that the way that the average surface temperature of an airless Earth are calculated using the Stefan-Boltzmann equation are wrong.
All of which caused certain members of the Lukewarm church of orthodox climatology to get a bit potty mouthed, because the implication of this is that the average temperature of -18C touted by the CO2 worriers (and Willis Eschenbach), as the temperature the Earth’ surface would be at without GHG’s in the atmosphere, is plucked out of… thin air.
Back in early January I missed this comment on our suggestions page:
| RKS |
Submitted on 2014/01/09 at 11:05 am
With respect to Nikolov and Zeller. – Please help if you can. By calculating the arithmetic average temperature of the moon N&Z arrived at the actual temperature of 197K as measured by Lunar Diviner IRRESPECTIVE of the moon’s rotational speed, thus allowing them to determine the same value for the grey body of the Earth which has a similar regolith. Unfortunately there are those who tend to hog discussion at Bishop Hill and who shout loudly, and rudely, that N&Z are incorrect BECAUSE of the difference in rotation of the Earth and Moon. Is there an accepted proof to rebut this argument as N&Z will not e accepted at Bishop Hill until this is dealt with conclusively? |
I raised the rotation rate issue myself, but we never got a quantitative answer to the question. So I asked Tim C to rerun his model for a body rotating in 24hrs as opposed to 29.53 days. he needs to check a few things and will hopefully get back to us on this soon.
http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
Black-body temperature (K) 270.7
This figure is in error. The error arises out of the incorrect application of the Stefan-Boltzmann law.
The Moon is a spherical rotating body strongly illuminated from one side by the Sun at a zenith rate of 1360.8W/m^2 (or whatever the solar ‘constant’ is this week). But the calculation treats the Moon as a stationary body under a constant dimmer illumination from all sides.
The erroneous formula used is:
Pi*R^2 S0 (1 – AMoon) = 4Pi*R^2 TMoon^4
where Pi*R^2 is the projected geometrical area of the Moon, S0 is
the solar constant (or, solar irradiance at the mean Sun-Earth
distance, 1360.8 W/m2, as given by Kopp and Lean, 2011),
and AMoon is the planetary albedo of the Moon (nominal value,
AMoon = 0.12).
Adapted from a similar equation for the Earth in:
The role of long-lived greenhouse gases as principal LW control knob that governs the global surface temperature for past and future climate change : Hansen Lacis et al 2013 :Tellus – SERIES B CHEMICAL AND PHYSICAL METEOROLOGY
*Corresponding author, e-mail: Andrew.A.Lacis@nasa.gov Accepted for Publication (Preprint Version) “This paper is part of a Thematic Cluster in honor of the late Professor Bert Bolin for his outstanding contributions (sic) to climate science.” Tellus B 2013. © A. A. Lacis et al. Citation: Tellus B 2013, 65, 19734, http://dx.doi.org/10.3402/tellusb.v65i0.19734
The albedo difference between Moon and Earth using the same equation gives us the spurious 255K figure for Earth.
This equation is a load of nonsense, as Nikolov and Zeller ably demonstrated in their paper:
https://tallbloke.wordpress.com/2012/01/17/nikolov-and-zeller-reply-to-comments-on-the-utc-part-1/
Despite being vilified, attacked, denigrated and censored by Anthony watts and his pig-ignorant and potty mouthed compadre Willis Eschenbach.
Nikolov and Zeller derive the correct equations for the calculation of surface temperature of a slowly rotating black body illuminated from one side.
Their theoretical figure, once modified to take account of the heat capacity of the lunar regolith, gives the correct answer in Line with the Diviner empirical data. The true average surface temperature of the Moon is in the region of 198K, some 90K less than the average surface temperature of the Earth.
Clearly, if the co2 theory proponents claim that ‘greenhouse gases’ warm the Earth by 33K, then another factor or factors is/are responsible for the bulk of the elevation of the Earth’s average surface temperature above that of the Moon. I covered some of the possibilities in a non-technical essay a while ago.
__________________________________
- Vasavada, A. R., J. L. Bandfield, B. T. Greenhagen, P. O. Hayne, M. A. Siegler, J.-P. Williams, and D. A. Paige, Lunar equatorial surface temperatures and regolith properties from the Diviner lunar radiometer experiment, J. Geophys. Res., 117, E00H18, 2012.
- Bandfield, J. L., R. R. Ghent, A. R. Vasavada, D. A. Paige, S. J. Lawrence, and M. S. Robinson, Lunar surface rock abundance and regolith fines temperatures derived from LRO Diviner radiometer data, J. Geophys. Res., 116, E00H02, 2011.
- Paige, D. A., et al., Diviner Lunar Radiometer observations of cold traps in the Moon’s south polar region, Science, 330, 479-482, 2010.
- Paige, D. A., et al., The Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment, Space Sci. Rev., doi:10.1007/s11214-009-9529-2, 2010.
Tallbloke's Talkshop 
The site is accessible via the Wayback Machine up to November 2013.
http://web.archive.org/web/20131102125512/http://www.diviner.ucla.edu/blog/
Thanks for this post. I’ll read your links and think it all over. So much to think over and digest, and so little time.
Great place this talkshop.
~ Mark
I found this :
http://pds-geosciences.wustl.edu/missions/lro/diviner.htm
Looks like they have more data, so they may be in the process of updating.
1. Diff between temp decay rate and temp growth rate as funnction of solar input =lunar near surface temp input rate from tidal smd radioactive sourced.
2. Full dark temp decrease trend looks hyperbolic: show natural temp in vacuum at space background (3.3?A).
3. Lunar geotjermal gradient from above (?) How deep must dig to get to livable temps, no need heating source?
One graph, much info?
Doug: The Equatorial average at all depths measurable below 4cm is around 32C below freezing.
That’s at the equator. It get’s colder towards the poles. Much colder.
As you can see from Vavasada’s fig 7, the diurnal swing below 0.3m (12 inches) is negligible.
There is something I don’t understand but it looks like I went into this a couple of years ago, no idea what I figured then. Plot is showing equatorial lunar but also how the heat behaves as it flows into and out of the ground, a phase retardation occurs, go deep enough and it settles as an integrating instrument (fancy name for very slow responding). This measures at 215K but simulation is still settling, goes a little lower.
Taking the surface temperature I expect RMS to give the true figure and mean to be erroneous given the waveshape. That is not the case, why? Is that an error in mature software, seems unlikely.
Tim: Vavasada gets 240K average from a few cm below surface. My guess is your model isn’t capturing the insulating aspect of the regolith.
Some comments made in 2012 by Jinan Cao to a discussion group of which I’m a member might be of interest. He said …
“…Basically, the 15°C (or 14.5°C in the article) Earth’s mean near-surface air temperature is the temperature for N2 and O2 that constitute 99% of the air. It is a physical quantity different from the surface temperature defined by the SB equation.
Secondly, the emissivity of the earth-atmosphere is something that can be determined from the outgoing radiation spectra, which is a figure close to 0.7. While SSD has given wrong reason explaining why it is 0.7, this article’s estimate of 0.95 is obviously a preferred guess work. ”
I haven’t heard from inan in a while but will email him the URL for this topic and maybe he’ll respond.
There is no mystery over heat conduction, the process shown, same everywhere, parameters vary.
The actual surface is where there will be dispute. What I am showing is extremely simple, it says nothing about how, only what happens.
The two limit cases are, assume for all wavelengths
1. the surface is a perfect insulator, the surface temperature is the temperature of the source, zero heat passes through.
2. the surface is a perfect absorber, in which case the full source flux perfectly couples into whatever is below, talking atomic level. The temperature depends on the conductance of this material, all the way down.
Ground phase lag just like that appears in terrestrial soil temperature, where too it is a bidirectional heat flow. Related to this is a good deal of the so called UHI effect. Urban areas increase the thermal coupling and hence the delayed daytime peak and reduced nighttime min.
I note from the diviner website http://pds-geosciences.wustl.edu/lro/lro-l-dlre-4-rdr-v1/lrodlr_1001/errata.txt that old copies of data will not be kept in the archive and that new data to be released will contain changes to historic data.
Also wayback machine only keeps copies of non data files.
Maybe history is being re-written as we speak?
“During the course of the LRO mission the DLRE science team may update
previously released data products or documentation; for example, updates may
occur due to changes in calibration data or procedures. Updates will be
reported in this file. Older versions of data and documentation will not be
retained in the archive.”
Tallbloke,
Thanks for an excellent post. This is a problem where amateurs such as your flock can improve our understanding of surface temperature on airless bodies. We will know when we have it right as the equations will predict temperature profiles that match the Diviner observations.
That “tchannon” model is a fascinating approach and in one sense he has already solved the problem. I have a functioning copy of PSPICE and plan to have some fun with it. Certainly it should give some insights as to the effect of rotation.
What I am trying to build is a mathematical model to do the same thing starting from Scott Denning’s equations and the corresponding N&Z equations.
The first thing I noticed was that Denning’s equations are exactly correct if the Moon was at a uniform temperature. This would require that the Moon be a thermal superconductor which clearly it is not.
Then I looked at N&K’s equations and they are exactly correct for a body that reaches thermal equilibrium instantly. This would require that the Moon be a perfect insulator which it is not.
Neither set of equations is any help when you try to take rotation into account. One needs equations that include realistic assumptions of surface thermal properties.
The Diviner web site used to show the Moon’s average equatorial temperature as 206 Kelvin while Vavasada says 214.4 Kelvin. Is there a simple explanation for this discrepancy?
Galloping Camel: At low temperatures, smallish energy differences make a bigger difference to T. Not sure why the difference between diviner website and Vavasadas paper, and I doubt he will have much to say about it, as he has since moved on to newer projects.
This discrepancy raises some issues which can be investigated.
1. The process going on subsurface is unimportant, no dispute. The only changes would be conduction properties. (conduction in a solid)
2. What actually happens at the contact point between a thermal flux and an actual substance is likely disputed.
Vasavada plot is a model
http://faculty.washington.edu/sew2/publications/ includes this one
Cited paper is this on
Vasavada, A. R., D. A. Paige, and S. E. Wood (1999),
Near-surface temperatures on Mercury and the Moon and the stability of polar ice deposits. Icarus 141, 179-193, 1999.
A lot on DIVINER instruments here, not had time to go through it.
The Lunar Reconnaissance Orbiter Diviner Lunar
Radiometer Experiment
D.A. Paige ·M.C. Foote ·B.T. Greenhagen ·J.T. Schofield ·S. Calcutt ·
A.R. Vasavada ·D.J. Preston ·F.W. Taylor ·C.C. Allen ·K.J. Snook ·B.M. Jakosky ·
B.C. Murray ·L.A. Soderblom ·B. Jau ·S. Loring ·J. Bulharowski ·N.E. Bowles ·
I.R. Thomas ·M.T. Sullivan ·C. Avis ·E.M. De Jong ·W. Hartford ·D.J. McCleese
Received: 24 January 2009 / Accepted: 7 May 2009 / Published online: 26 June 2009
© The author(s) 2009. This article is published with open access at Springerlink.com
Click to access art_10.1007_s11214-009-9529-2.pdf
I scaled the simulation parameters for 709 hour “day” length (day and night), result the same.
Changed day length to 24 hours, mean temperature rises slightly so I was wrong to say it had a large effect. Alas I have no idea what I did previously to come to the wrong conclusion.
For the likely good it will do here is Simetrix SPICE dialect netlist
The underlying SPICE might be portable, details won’t.
Possibly the most widely available open source SPICE is ngspice. Front ends tend to be rare so it’s mostly text editors and plotting.
Tim, given that the deep craters near the poles have a temperature above the Cosmic Backgroundradiation (~25K vs 2,77K), this could be due to a hot core.
This means that the temperature just below the surface where the daily variation just isn’t noticeable anymore is set by geothermal heat. Going deeper the temperature should rise towards the core, same as on earth.
In these cold craters the temperature should rise from 25K, also warming towards the core.
So you have to take a “base” temperature into account for every latitude using the average surface temperature there.
I have insightful advice from Roy Clark about this application which I have pasted to follow:
“The Stefan-Boltzmann equation is correct, within the blackbody equilibrium constraints that are used to define it [equilibrium cavity etc.]. It is the application of the S-B equation by the IPCC that is wrong. The whole concept of an average planetary temperature is little more than a mathematical abstraction. These issues go back much further than the IPCC. The climate models made the wrong assumptions back in the 1960s. They were stated quite clearly by Manabe and Wetherald in 1967. The arguments can be traced back to ‘equilibrium IR atmospheres’ that were introduced in the 1920s or before.
There are (at least) 4 levels of assumptions that need to be addressed. The first level involves static effects related to angle of incidence and surface reflectivity. The second level involves the dynamic heating effects. There is thermal conduction below the surface. The third level is that 75% of the Earth’s surface is water, and the cooling of the ocean surface is mainly by ocean evaporation, not by LWIR radiation. Lunar temperatures are irrelevant when considering the Earth’s water/air based climate. The fourth level is that the IPCC is not using surface temperature to measure ‘global warming’, but is using the weather station temperature instead. This is the air temperature measured at eye level above the ground.
Level 1: The moon’s surface only absorbs part of the solar flux. A fraction is reflected that depends on the materials involved. (We can see the solar reflection). Similarly, the surface may only be a partial LWIR emitter. In addition, the effective illumination area and the reflectivity of a dielectric surface changes with the angle of incidence (Lambert’s cosine law and Fresnel’s laws of refraction). The moon is not a blackbody billiard ball. The use of ‘average’ surface properties is only a partial solution.
Level 2: The Second Law of Thermodynamics gets lost in the temperature averaging assumption. The surface heating establishes a thermal conduction gradient between the surface and the subsurface layers below. Heat is stored and released by these subsurface layers. This means that the maximum surface temperature may be below that predicted by S-B. In addition, there will be a time delay (phase shift) between the peak solar flux and the peak surface temperature. In fact, the whole temperature profile will be shifted from the flux profile. There is also dust at the surface that can scatter light (that one gets complicated).
Level 3: The dominant cooling process for the Earth’s oceans is wind driven evaporation. The maximum ocean surface temperature is near 30 C. This is found in the equatorial warm pools. Here the full tropical flux is balanced by the ocean surface cooling at the average wind speed. Using TRITON buoy data for 0° lat 156° E, the average wind speed is near 5 m s-1 and the evaporative cooling flux is about 40 W m-2 / m s-1. The wind speed fluctuations are also large (at least 1 to 10 m s-1). The 30 C temperatures extend to about 50 m in depth and the warm pool stores about 6 months worth of tropical solar flux. Most of the solar flux is transmitted through the ocean surface. 90% is absorbed within the first 10 m depth and the rest is absorbed within the first 100 m. The ocean surface is also a good blackbody emitter and absorber, but most of the surface LWIR emission is exchanged with the atmosphere. The net LWIR flux is nominally 50 W m-2. This provides about 20% of the cooling needed to dissipate the tropical solar flux. The rest is evaporation with a little sensible heat (dry air convective cooling). There is no ‘equilibrium greenhouse effect’.
Level 4: The solar and LWIR fluxes interact with the surface (air-land or air-ocean interface). The climate record is derived from the weather station temperature or meteorological surface air temperature (MSAT), which is the air temperature measured inside a ventilated enclosure placed at eye level, 1.5 to 2 m above the ground. The maximum daily MSAT is generally a measure of the maximum temperature produced by the convective air mixing at the thermometer level. A dry surface below the MSAT enclosure can easily exceed 50 C under these conditions. The minimum MSAT is generally a measure of the bulk air temperature of the local weather system as it is passing through. Since a majority of weather systems originate over the oceans, this is the source of the ocean surface temperature signal seen in many weather station trends. This is why the climate models were ‘calibrated’ using the ocean surface temperature. The climate record should follow the ocean temperatures downwards for another 20 years or so. Then we will find out how the low sunspot level influences things.
There can be no ‘CO2 signature’ in the weather station record.
The real question that needs to be addressed by the IPCC is: why is the ocean warm pool temperature near 30 C?
Regards
Roy Clark”
Peter
Lot of good stuff in there.
“In addition, the effective illumination area and the reflectivity of a dielectric surface changes with the angle of incidence (Lambert’s cosine law and Fresnel’s laws of refraction).”
I found it necessary to add a cosine correction factor to the lunar model. When I originally did this I asked for any theories or comments, silence. What you mention was in mind. I also considered polarisation. (it’s in the function box driving the current source)
I put this down to the effect of surface roughness varying path lengths.
I agree, water dominates.
Ben, I don’t know. A flux from the core through a thick crust, not as the moving terrestrial crust with ocean floor and a smaller body which has had time to cool, points to a very low figure.
tchannon says: March 18, 2014 at 12:27 am
“points to a very low figure.”
Absolutely, a flux of only ~20 mW/m^2 would explain the low temperatures in the craters where the sun never shines.
But at the equator the temperature just below 30 cm would be maintained by this flux around the average surface temperature, and increase with depth towards the core.
A flux means heat is creeping up, however slowly.
Tim, a hot core on the moon seems very likely:
http://en.wikipedia.org/wiki/Lunar_mare
A thought experiment:
We move the moon to outer space. No solar warming it, and after some time the whole surface will be this 25K due to my assumed flux of ~20 mW/m^2. On earth the temperature towards the core rises with ~25K /km, lets assume the same for the moon.
No we heat a sufficiently large circle with 100 W/m^2. After warming up the upper 20-30 cm the surface will be 205K and a stable situation will exists. NO further heating of the deeper layers, no energy left for that !! At 205K the surface radiates the same 100 W/m^2 to space as it receives.
Due to the small flux the deeper layers below the circle will warm up until they reach the surface temperature and the lapse rate towards the core (25K/km) is set.
Good news, the Diviner website is in the air again 😉
http://www.diviner.ucla.edu/
I was almost certain that the Diviner site had a technical issue (most likely a server crash), which happened before, and that it would come back online …
Couple comments regarding Tallbloke’s article above:
1. The mean annual surface temperature at the lunar equator (based both on Diviner measurements and NASA thermo-physical modeling) is 213 K;
2. The global average annual surface temperature of the Moon is 197.3 K based on the verified TWO thermo-physical model of Vasavada et al. (2012). TWO has been shown to accurately reproduce the Diviner-measured equatorial temperatures over complete diurnal cycles.
3. The reason that the simple form of the SB equation does not work for spherical bodies is not the rotational speed (rotation has no impact on the average T whatsoever), but a mathematical feature related to non-linear functions called Holder’s inequality between integrals.
4. The best estimate of the thermal effect of Earth’s atmosphere is at present 90.3 K. Yes, this large enhancement cannot be explained by the observed 155 W m-2 atmospheric absorption of outgoing LW radiation due to greenhouse gases… Something else is going on!
I concur with Ned’s comments above.
Tim’s model correlated superbly with the Diviner observations and he also found that rotation rate had very little effect on average temperature. It seems that 197 Kelvin is the correct average temperature of the Moon and also for an airless Earth now we all agree about the effect of rotation rate.
Tim,
There are plenty of FEAs out there but I wanted one that was free and easy to use. It seemed that Energy2D was what I wanted. Free downloads available from:
http://energy.concord.org/energy2d/
I constructed a three layer model consisting of two meters of basalt covered with 2 meters of regolith with vacuum on top of that. Add solar radiation and push the “Run” button. It worked but did not produce anything resembling Tim’s model. It seems there is a problem with the vacuum object but I can’t figure out how to fix it.
Just in case I did something really dumb here is my input file: [mod: code follows a couple of comments down –Tim]
Next I decided to try Vavasada’s one dimensional model of the lunar regolith which appears to be almost as good as Tim’s PSPICE model.
While all the thermal properties are easy to find I could not find the model itself. Maybe it is in one of those related Diviner papers behind paywalls. Not to worry as it is easy to construct your own one dimensional FEA where there are two partial differential equations (as in this case). Even someone like me with limited programming skills can do it. All you need is an Excel spreadsheet and a little time.
The Excel spreadsheet produced plots that looked just like Tim’s but with poorer correlation with the Diviner data. For example I was 50 Kelvin low on the peak temperature. I could improve the correlation by changing the regolith properties but that is “cooking the books” so I am trying to figure out where I went wrong.
WordPress tip
How to post “code” and you can make it collapsed for most readers by putting this in the opening shortcode
[code collapse=”true” ]
http://en.support.wordpress.com/code/posting-source-code/
[mod: it had defaulted language CSS, sheesh, flipped it to XML, language highlighting appears –Tim]
I see, a Java program. (anyone should be using V7, long history of security issues with Java)
Okay, if anyone wants to try, get it then select the XML above, copy to clipboard or whatever, paste or whatever into a text editor, save a new file with the file suffix e2d
eg. galloping.e2d
Start the Java, open the file you just created.
Seems to do something. Not sure what. 🙂
Had a play, can’t figure it so…
A long time ago I was involved with Russian software for PCs. They started to try to sell it in the west, I was kind of involved as a past go-between for US/Russian academics, bit of a tale there about broken Internet connectivity even for SMTP. The poor chaps were brilliant but barely had enough to eat, were desperate. There was a lot of extremely clever technical software in Russia , a case of needs must when few computers are available and all very low power. This is why the Russians were so good at the maths and science behind things where instead of throwing money at a problem you have to get clever.
The result in the west was the Quickfield FEA package. (as I recall from a very long time ago)
I’ve only ever dabbled with the demo / student version, but I have done some fun things, so long ago I can’t remember what. Probably to do with heat flow in electronics, lots of design problems when you are designing stuff.
Went and had a look, yep, Quickfield (Tera) are still going.
The Student edition is real but very limited in mesh count. This might be enough. Deadly serious software, real CAD. Mechanical models can be imported as DXF, Draftsight ought to be good for that, but more heavy CAD (in this case the free version is the full version, no catch)
Looks like Quickfield can do it provided the limitations are sufficient. It seems to load the parametric editor so I assume it allows parametric simulation. (move the sun around the moon, solve for each step)
Want registration details before download. (I used to get email from them, not a problem)
For the brave Quickfield, 30M download, Windows only,
http://www.quickfield.com/index.htm
Draftsight (Dassalt systems, Solidworks 3D)
http://www.3ds.com/products-services/draftsight/overview/
Tim,
Your comments on Russian software were on the money.
In 1996 I had a visit from a Russian engineer who had a 6,000 point 3D FEA program for analyzing magnetic fields. We set up an input file describing our magnet geometry and hit [Enter]. Gavrilov (the Russian) said we would have to wait 20 minutes for the program to complete. Instead it closed in a few seconds so we thought something was wrong.
It turned out that our high end ($5,000) 486 based PC we used to run AutoCAD was significantly faster than Gavrilov’s 286 machine (12 MHz, 16 bit, if I recall correctly).
However, the primitive nature of Russian PC hardware does partly explain the magnificent efficiency of their software.
Moving on, I do have a copy of QFIELD and it still works even though it is at least 12 years old (I retired in 2002). It is slow compared to the Russian program but I like it because the “Post Processor” is nifty. Probably later versions are even better.
Before getting into the business of building free electron lasers I worked on many productivity improvement projects. My greatest achievenment reduced the design time for a dry type (no cooling oil) “Medium” transformer from 13 weeks to one day. At the GE plant in Rome, Georgia a medium transformer was defined by what could be shipped in one piece by rail. These transformers weighed up to 40 tonnes and had ~100,000 parts.
The software used was “Concept Modeler” a true “Expert System” that relied on a combination of “Solids Modeling” and FEA. It was originally created by Babcock & Wilcox for designing nuclear power plants. Each copy of the software cost $120,000.
Later when I was working at Duke university I was offered a free copy of the software in exchange for a basketball autographed by the 1991/2 team! I did not take up the offer as “Concept Modeler” was way too sophisticated. ProEngineer was also too sophisticated so we used AutoCAD to design the Duke University Free Electron Laser. My old office is on the left side of the picture on the ground floor.
http://www.tunl.duke.edu/web.tunl.2011a.higs.php
Nicola Scafetta has an office directly above mine while the magnificent Robert G. Brown who got my chestnuts out of the fire on several occasions has an office in the main physics building on the other side of the “X” parking lot. I love the fact that these guys are honest scientists who won’t tell lies even though that hurts their prospects of obtaining government funding.
Last year on my way to a teaching assignment in Alabama I found myself in Rome so I looked for the GE plant to see how things were going and find out whether the approach had been applied to oil cooled transformer designs.
It was a great disappointment to find that the factory had relocated to Mexico.
Back in1989, I really liked the Dassault CATIA software over IBM but “Concept Modeler” was even better for transformer design.
Tim,
Thanks for that Quickfield link. You were right about it not running in Linux but it works well with Windows Vista.
Given that the student version has a limited number of nodes you get some strange effects around the edges. Thus far I have not been able to replicate your PSPICE results using transient thermal analysis but it has to work!
The heat problem is fairly trivial as a basic SPICE problem since heat is a valid dual. The basics are ridiculously simple.
Apply a thermal flux to a thermal resistance with a thermal flux sink dependent on the temperature of the domain interface.
A physical surface needs a thermal delay line into a thermal capacity. This is where thermal characteristics of materials appear. As I recall back of envelope was about right for supposed characteristics.
And that is it, less spinning, less handling a sphere.
FEA is more suited to higher physically dimensionality, complicated shapes. Put another way, SPICE is trivial where lumped entities can be used but modelling a complex regime would mushroom in complexity. The fun mental gymnastics is finding equivalence, same in most fields.
Right now I am finishing writing a NETCDF parser, spits out decoded info including data. Good stuff on the way.
Okay, this is brief so you are not left out in the cold. I think this problem can be handled, painfully, by a massive package, shame about the documentation unless you are multilingual.
http://www.scilab.org/ (yes it is 100 to 200M)
Look at XCOS therein
This does not cover XCOS but might be worth reading first, to get some idea of what is involved in learning SCILAB, big again, powerpoint 6.8M, hundreds of pages, must have taken him ages.
http://www.heikell.fi/downloads/scilab.ppt
I’ll take a pop at using this later. (I have an oldish version installed)
Tim,
Thanks for the comments above. While I am more than impressed by your PSPICE model I wanted to validate it in terms of the thermal properties of the lunar regolith as measured by Apollo 15.
I am now up to speed with QuickField and find that applying it to a one dimensional heat transfer problem is like using a steamroller to crack a nut.
I now have pretty plots that match yours, Vavasada’s and the Diviner observation quite well. That is the good news. The bad news is that I had to introduce fudge factors just as you had to do with PSPICE.
To get the peak temperature right (390 K) I had to set TSI = 4,350 W/m^2. Anybody with a scientific calculator can tell you that would correspond to a black body temperature of 526 Kelvin.
To get the low temperature right (95 K) I had to set the regolith conductivity at 0.03 W/K-m as opposed to Vavasada’s 0.007 W/K-m.
I don’t believe that QuickField does not know how to apply Stefan-Boltzmann to calculate equilibrium temperatures so I need to find out where I went wrong.
Amateurs find more comets than professionals do. Maybe “Climate Science” could use a little help from amateurs.
That’s brilliant getting a different domain tool to fly on the same problem.
The only fudge I used, changes result by I think 1% was adding a sine power correction term, the difference between Diviner and straight model gave a simple functional error difference. This was added as a functional shape change to the solar flux, input to sine voltage to current conversion, a practical point to insert the change.
I put this down to some kind of incident light or conductivity of dust effect on a rough surface, asked but there were no takers on suggesting an answer. This assumes of course the Diviner data is accurate. Instrumentation is questionable. Do it again in 100 years, answer will be different.
My result is empirical, adjust real physical surface “loading” until there is a match. The values can be turned into thermal units but I make no attempt at a layered ground. (doesn’t seem to matter)
I expect Vavasada is assuming an earth like behaviour of solid ground but this is unwise. In reality the presence of a hard vacuum has dramatic effects thermally because it is only then that conductivity and convection is finally broken and radiative dominates. This is documented and used in engineering for space based insulation.
This will do, see Figure 2, noting log-log scales, two orders of magnitude drop. Same applies on Dewar / vacuum flasks.
Click to access ICEC19_MLI.pdf
What I have in mind is the difference between the thermal conductivity of a porous material with gas present and that without. Hence the very low thermal conductivity of the Stephan-Boltzmann surface, where it all happens. You might need a few microns of shell. This is the thermal resistance against which SB operates both day and night.
I have some ideas on what might be wrong. Rather than play guessing games on-line, my email address book knows you so you will have my email. I need some clues on how the result is wonky.
If you are in a position to difference results the shape ought to give clues. If you need a reference dataset at some particular sample rate, maybe I can compute something.
[…] tchannon on One of our spacecraft is missi… […]
[…] Scott Denning’s calculation assumes that the surface of an airless Earth would be at a uniform temperature. Given that solar energy is not evenly distributed over the Earth’s surface the planet would have to be composed of a thermal superconductor to achieve this. So does that mean that the mavericks are right? While I am inclined to encourage the underdog, it turns out that N&Z are wrong too. Their calculation would be correct if an airless Earth was a perfect insulator! One interesting result of their simplifications is that the temperatures they predict are not affected by the rate of rotation (see Ned Nikolov’s explanation here). […]
Tim,
As commented on the other Diviner thread I have fixed my dumb errors.
Much of the Moon’s bedrock appears to be Basalt with a thermal conductivity of 1.70 W/m/K.
According to Apollo 15 data the regolith has conductivity in the range 0.001 to 0.008 W/m/K.
My model has one layer of regolith sitting on basalt bedrock. The precision of the model could be improved simply by adding layers to better represent the variations with depth. My guess is that the student version of Quickfield can handle between five and ten layers but the result won’t be any better than your PSPICE model! However, it is good to know that QF validates your efforts.
Sad to say I have managed to lose your email address. You could use my [snip address] [mod: have the address anyway –Tim]