Add option for geodetic/geopotential altitude input to the atmosphere model.

[robfalck]

Issue Type

• Bug
• Enhancement
• Docs
• Miscellaneous

Description

The atmosphere model in Dymos was originally intended to be a low-fidelity model intended to support some example cases.
As our userbase has grown, a number of projects are using this model and requesting higher fidelity.

The 1976 standard atmosphere implementation should correct the geodetic altitude input and perform the interpolation using the geopotential altitude. The Dymos implementation currently assumes that the input altitude is already the geopotential altitude.

To address this, we will add an option to the atmosphere component:

h_def

Which will take one of two options: geopotential and geodetic.

The default will be geopotential and will provide the current behavior.
If h_def is geodetic, then the incoming geodetic altitude will first be converted to the geopotential altitude using Equation 19 from Reference 2 (Equation 25 from Reference 1)

z = R0 * h / (R0 + h)

Where Re is 6356.766 km, z is the geopotential altitude, and h is the geodetic altitude.

References

1. A Discussion of Various Measures of Altitude
2. US Standard Atmosphere 1976

Example

N/A

Environment

N/A