Atmosphere Incorporation: USatm1976, MIL_SPEC_210A Hot/Cold/Polar/Tropical, and Offsets #950

ehariton · 2026-01-05T19:09:51Z

Summary

Incorporates USATM1976 directly into aviary as the default atmosphere so we no longer need to rely on the dymos atmo library.

Incorporates open-source MIL_SPEC_210A atmospheres (hot/cold/polar/tropical) which the user can switch to via options.

Individual atmosphere data is now separated into it's own file, while the core component that imports the data and does the calculations has been named atmosphere.py.

Adds an temperature offset option, allowing the user to shift an atmosphere profile by a specific number of degrees kelvin to mimic hotter / colder days.

Geometric vs. Geopotential input option is preserved.

Removed option to add dsos_dh as an output. This is now always provided. This is only used by solved 2DOF ODE.

Removed drhos_dh output as it was not used in Aviary.

Many tests that relied on atmosphere, including some engine conversion tests, referenced the atmosphere model. Because the original dymos atmosphere model was based on English units and used an English akima spline, the values changed slightly when converted to the SI units and the new akima splines. SI units is what the original 1976 atm standard was published in. There were noticeable small differences, rounding etc, between the dymos atmosphere implementation in imperial units and the values published in SI units in the original standard.

Related Issues

Resolves Add ability to use hot day (non standard atmosphere) #133

Backwards incompatibilities

None

New Dependencies

None

… files for raw MIL_SPEC_210A data in its original units for easy comparison. changed references to USATM to just atmosphere.py and moved atmosphere group, and atmospherecomp, and akima generator into atmosphere. Removed unused reference to usatm in GASP comments

… of drhos_dh and dsos_dh which were used for calculating MaxQ for spacecraft, reverted density to be computed based on raw density plus a correction factor, reverted speed of sound and dynamic viscosity to be calculated from equations instead of akima since raw data was calculated from equations for USatm1976 and for MIL_SPEC_210A did not have any of that info

…a extractor out of individual raw atmosphere files and consolidated into one call inside of _build_akima_coefs

…ecause the raw data could be in different units.

…d partials to match updated compute, added (int,float) option to to delta_T_Kelvin to allow for user typing in 15 without a decimal point

…e values in init, tested outputs against source data manually and good match. requres inHg60 unit conversion which was added to OM lib

…tmosphere.py

… atmosphere user guide doc

…0 mixup

…plines for tropical

…odelling

…ries

… as those value changes were small

…e values in the engine model because original source data is not complete and needed to be extrapolated

aviary/docs/user_guide/atmosphere.ipynb

jkirk5 · 2026-01-09T21:27:50Z

aviary/models/engines/turbofan_23k_1.csv

@@ -1,4 +1,4 @@
-# created 06/06/25
+# created 01/08/26 at 14:09 by omdao


Suggested change

# created 01/08/26 at 14:09 by omdao

# created 01/08/26

jkirk5 · 2026-01-09T21:30:04Z

aviary/subsystems/atmosphere/atmosphere.py

+        self.options.declare(
+            'delta_T_Kelvin',
+            default=0.0,
+            desc='Temperature delta from International Standard Atmosphere (ISA) standard day conditions (degrees Kelvine)',


Suggested change

desc='Temperature delta from International Standard Atmosphere (ISA) standard day conditions (degrees Kelvine)',

desc='Temperature delta from International Standard Atmosphere (ISA) standard day conditions (degrees Kelvin)',

Deg C and K have the same magnitude so it might be more natural language to state that the delta is in Celsius

jkirk5 · 2026-01-09T21:35:16Z

aviary/subsystems/atmosphere/atmosphere.py

+        self.options.declare(
+            'data_source',
+            default='USatm1976',
+            desc='The atmospheric model used. Chose one of USatm1976, tropical, polar, hot, cold.',


Can we simply call it "standard"? It is much simpler to remember than a very specific shortening of "1967 standard atmosphere", and we are using generic terms for the milspec atmospheres anyway

Sounds good to me.

jkirk5 · 2026-01-09T21:38:14Z

aviary/subsystems/atmosphere/atmosphere.py

+            desc='Temperature delta from International Standard Atmosphere (ISA) standard day conditions (degrees Kelvine)',
+        )
+
+        self.options.declare(


This should get updated to use a new Enum that is linked to a new Aviary variable, so users can set this from the csv. Maybe in Mission?. Adding a types argument here pointing to that Enum will also catch incorrect options getting passed - see the speed type option for an example

jkirk5 · 2026-01-09T22:01:12Z

aviary/docs/user_guide/atmosphere.ipynb

+    "You will need to make a new `_raw_data` dictionary inside your new file. Look at the example `_raw_data` contained in `StandardAtm1976` for reference. \n",
+    "\n",
+    "## Converting Raw data Proper Units\n",
+    "From here on our we need to be especially mindful of units. We are going to use a non-openmdao helper function `_build_akima_coefs` to help create the akima coefficients. \n",


Suggested change

"From here on our we need to be especially mindful of units. We are going to use a non-openmdao helper function `_build_akima_coefs` to help create the akima coefficients. \n",

"From here on our we need to be especially mindful of units. We are going to use a helper function `_build_akima_coefs` to help create the akima coefficients. \n",

I don't think specifying non-openmdao adds any useful info. It's also not a dymos, numpy, pyoptsparse, etc. helper function so why single out OM?

jkirk5 · 2026-01-09T22:02:25Z

aviary/subsystems/atmosphere/atmosphere.py

+            partials['dsos_dh', 'h'] *= dz_dh**2
+
+
+def _build_akima_coefs(out_stream, raw_data, units):


This should probably get moved to a util folder, it feels odd to have here. Maybe an atmosphere/utils.py file?

I also just noticed it probably shouldn't be a private function if we want it to be used by users

jkirk5 · 2026-01-09T22:02:50Z

aviary/subsystems/atmosphere/data/MIL_SPEC_210A_Cold.py

Can you move all the atmosphere data files to an atmosphere/data folder?

jkirk5 · 2026-01-09T22:06:20Z

aviary/docs/user_guide/atmosphere.ipynb

+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Adding your own Atmosphere Model\n",


Maybe this is developer guide atmosphere info. I'm starting to think we need to completely re-organize how we organize the docs anyway though, splitting up the subsystems into different places doesn't seem useful...

jkirk5 · 2026-01-09T22:09:43Z

aviary/subsystems/atmosphere/data/MIL_SPEC_210A_Hot.py

+        Density in kg/m^3.
+    """
+
+# turn off ruff linting


Technically formatting, linting is when actual code besides whitespace gets touched

…ns suggestions

…low for building atmosphere models

ehariton added 30 commits December 8, 2025 14:36

added unit conversion to _build_akima_coefs

7e84114

successfully generating akimas from _build_akima_coefs, moved atm_dat…

e14d024

…a extractor out of individual raw atmosphere files and consolidated into one call inside of _build_akima_coefs

calculated akimas for all raw data

52fac6c

added peroperly interpolated altitude data to each atmosphere model b…

2dffa1c

…ecause the raw data could be in different units.

fixed error in density calcs thanks to Jess for spotting that. update…

c5ff59d

…d partials to match updated compute, added (int,float) option to to delta_T_Kelvin to allow for user typing in 15 without a decimal point

half started test_atmosphere and USatm1976TestCase1, it needs more work

9e2b4ea

moved library option load from init to setup because options dont hav…

0296736

…e values in init, tested outputs against source data manually and good match. requres inHg60 unit conversion which was added to OM lib

revised user guide to atmosphere model and added testing section to a…

ffa7825

…tmosphere.py

updated notes on atmosphere origins as well as added those notes into…

838c505

… atmosphere user guide doc

tweaking documentation and notes

736c993

updated doc wording

6030e83

small wording changes to test

c29ff8b

merge main

8aa488b

merge main

9a2c888

removed unused constants

1e52575

half way through checking corrected pressure based on inHg32 vs inHg6…

f308e0f

…0 mixup

found small 0.00009 value error on tropical data, re-computed akima-s…

ca9d89a

…plines for tropical

spacing

92b28ed

fixed typo in value

26d248c

added note on usage of MIL_STD_210A atmosphere models for transient m…

90d618c

…odelling

note spacing

603b92c

typos

f0c2b94

removed StandardAtm1976.py because no longer needed

64af4b7

added back source data for standard atmosphere

3ec7454

ruff formatting on two files

8473e65

added dsos_dh akima calculation and akima spline info the mil spec`

6bc73bf

added akima for dsos_dh for USatm1975 comp

a8b176d

lint

8d44865

ehariton added 2 commits January 6, 2026 20:32

added inHg60 tests back in

d105713

added geodetic test to atmosphere, failing one tests on dsos_dh wrt h

5f3353e

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ehariton added 3 commits January 7, 2026 14:54

added tests for geodetic cases

c162208

all added tests passing

758544b

formatting

b33f673

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ehariton added 14 commits January 7, 2026 17:17

added figures and removed extrapolated data from raw mil-spec data se…

1ab3e8e

…ries

recompoted akima tables based on non-extrapolated source data

13c21f6

updated default if name == main behavior of atmosphere model

839a18c

added user guide to toc and removed references to padding MILSPEC tables

05c5b8a

changed values for tests that relied on amosphere model input as long…

2aba740

… as those value changes were small

small value adjustments based on tests failing

d159fab

small values changes

1f35483

multiple tiny values fixes

05f6243

small value check tweaks

f8cda9e

small values tweaks due to atmosphere update which changes some of th…

70dd0ba

…e values in the engine model because original source data is not complete and needed to be extrapolated

small value changes in test_reports

1b9e315

small numerical updates based on new values from atmosphere model

46c0a21

lint

a3586ab

merge main

50bb1f9

ehariton requested a review from Kenneth-T-Moore January 8, 2026 18:45

Kenneth-T-Moore approved these changes Jan 9, 2026

View reviewed changes

Kenneth-T-Moore and others added 2 commits January 9, 2026 13:03

Merge branch 'main' into atm2

12577c3

merge main

493a042

jkirk5 requested changes Jan 9, 2026

View reviewed changes

ehariton added 4 commits January 12, 2026 20:40

changed US1976standard to standard, other small changes based on Jaso…

423917f

…ns suggestions

added Atmosphere Enums

f874ac6

moved build_akimas to its own file, updated docs to reflect new workf…

03abe73

…low for building atmosphere models

merge main

e74729b

		@@ -1,4 +1,4 @@
		# created 06/06/25
		# created 01/08/26 at 14:09 by omdao

	desc='Temperature delta from International Standard Atmosphere (ISA) standard day conditions (degrees Kelvine)',
	desc='Temperature delta from International Standard Atmosphere (ISA) standard day conditions (degrees Kelvin)',

	"From here on our we need to be especially mindful of units. We are going to use a non-openmdao helper function `_build_akima_coefs` to help create the akima coefficients. \n",
	"From here on our we need to be especially mindful of units. We are going to use a helper function `_build_akima_coefs` to help create the akima coefficients. \n",

		partials['dsos_dh', 'h'] = dz_dh*2


		def _build_akima_coefs(out_stream, raw_data, units):

Atmosphere Incorporation: USatm1976, MIL_SPEC_210A Hot/Cold/Polar/Tropical, and Offsets #950

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Atmosphere Incorporation: USatm1976, MIL_SPEC_210A Hot/Cold/Polar/Tropical, and Offsets #950

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Summary

Related Issues

Backwards incompatibilities

New Dependencies

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ehariton commented Jan 5, 2026 •

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