NASASpaceFlight.com Forum
General Discussion => Q&A Section => Topic started by: aero on 01/31/2014 04:16 am
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I just finished adding an extended standard atmosphere model to my simulation. I used the standard model up to the altitude of the given data, 84852 km altitude then I extended it using data taken from the attached graph.
Does anyone know where I can find data to validate my implementation? That is, I could use some data points for atmospheric temperature, pressure and density at altitudes above 90,000 km, and a data point above 120,000 km would be very helpful, too. Data within the range of the standard model is given with the model so I have that. Of course I can read temperature off of the attached figure, it is pressure and density, or their ratios, delta and sigma that I need to use to check my code.
Thanks
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If you can use matlab here's implementation of the 1976 US standard atmosphere up to 1000km
http://www.mathworks.com/matlabcentral/fileexchange/13635-complete-1976-standard-atmosphere
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If you can use matlab here's implementation of the 1976 US standard atmosphere up to 1000km
http://www.mathworks.com/matlabcentral/fileexchange/13635-complete-1976-standard-atmosphere
Thanks but I don't have access to matlab and don't know anything about the program beyond general ideas.
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Did you mean to say km, or is that meters? 120,000 km is almost 1/3 the way to the moon, well beyond GSO ...
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Did you mean to say km, or is that meters? 120,000 km is almost 1/3 the way to the moon, well beyond GSO ...
My bad. It's high, but not that high. 120,000 meters, 120 km. Thanks for pointing that out.
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Thanks but I don't have access to matlab and don't know anything about the program beyond general ideas.
You don't need to. Just open the *.m files in Notepad. The programming can be easily translated to your language of choice. It's all fairly straightforward.
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If you're looking for actual measured data at those altitudes, you'll have two issues:
* Data will be sparse due to difficulty of access - too high for balloons, too low for satellites (it's sometimes known as the ignorosphere)
* The atmospheric properties in that region and higher are quite variable with solar activity and weather.
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The thing is, I can't believe my answers. Why, well look at the data I get for 90,000 meters.
density, kg/m^3 error calculation pressure, Pa error calculation
2.71595203E-06 -1.82741457E-05 1.45747E-01 -1.82741457E-05
I have never seen anything like this and the errors being identical has to be an artifact of something not real. I just don't know what. I'm sure it is circular but I don't have density or pressure numbers at 90,000 meters so I am forced to use what I have generated. It's wrong but look as I might, I don't see the error. That's why I'm asking if someone has some numbers. By the way, I calculate temperature = 186.95 K at this altitude.
Where I have data, the error values seem quite rational, ~10^-6 using difference divided by standard value.
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Someone's already mentioned the 1976 US Standard Atmosphere, which goes up to 1000 km. You can google up a pdf of this document which has both tables of properties and the equations used.
As also already mentioned, the high atmosphere is pretty variable. The main factor affecting it is solar activity.
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You can use Octave, which is a free implementation of Matlab. Also, Scilab is very similar too Matlab but slightly different syntax and is also free (and much better maintained than Octave, IMHO).
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Thanks, but I've got it now. I programmed it in Excel.
The problem with most all of the choices is that I can't use existing computer programs as I don't know how to interface them with Excel and I can't find the equations upon which they are based. Generating data from the existing programs isn't very helpful except as verification as I don't have the underlying equations and inflection altitudes ... Anyway, I'm set for now.
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The Matlab model should have the equations in it.
But there's a big, bright world out there beyond Excel. You should visit sometime. :)
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The Matlab model should have the equations in it.
But there's a big, bright world out there beyond Excel. You should visit sometime. :)
@Robotbeat - Why? I have been programming computers for over 40 years in more languages than I care to remember. I could use any number of languages but I don't want to bother installing a development system on my new machine. Excel works fine for me, and when I have problems there are a bunch of helpful people here at NSF with ready replies. And just because I ask a question doesn't mean I stop striving to find an answer.