Atmospheric Case 08: Dropped Sphere in Varying Wind Field
Atmospheric scenario 8 tests a simple sphere with constant drag (CD = 0.1) falling from an altitude of 30,000 ft through a varying wind field while starting with an initial roll rate of -0.004178073 deg/s. The wind initially flows from the west, gradually changing to an easterly course as the sphere nears the surface. The wind speed can be calcaulated as follows: Vwind = (0.003h - 20) ft/s, where h is altitude MSL in ft.
Constants and Models
This scenario uses a spheroid body model with fixed inertias and aerodynamic coefficients unless otherwise specified in the scenario. The original details of the model can be found here. The 1976 STD atmosphere model defines atmospheric properties at various altitudes, specified here. The sphere's source of gravity is the J2 gravity model, specified here. The geodesy model used for this scenario is the WGS-84 rotating model, specified here.
Initial Conditions
| Scenario | Atmospheric Case 08: Dropped Sphere with Wind Shear | |||
|---|---|---|---|---|
| Body | Atmospheric Spheroid | |||
| Geodesy | WGS-84 rotating | |||
| Atmosphere | US 1976 STD; wind varies linearly with altitude, Vwind = (0.003h - 20) ft/s | |||
| Orientation | Body x-axis pointed north Body y-axis pointed east Body z-axis pointed down |
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| Gravitation | J2 | Duration | 30 s | |
| Initial states | ||||
| Aerodynamic Characteristics |
S (ft2) CL CD CY Cl Cm Cn |
0.1963495 0.0 0.1 0.0 0.0 0.0 0.0 |
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| Geodetic Position (deg, deg, ft MSL) |
Latitude Longitude Altitude, Mean Sea Level |
0 0 30,000 |
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| Velocity (NED Frame) (ft/s) |
X Velocity (North) Y Velocity (East) Z Velocity (Down) |
0 0 0 |
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| Body Attitude (NED Frame) (deg) (3-2-1 Rotation) |
Roll Pitch Yaw |
0 0 0 |
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| Body Angular Rate (NED Frame) [1]
(deg/s) |
Roll Rate Pitch Rate Yaw Rate |
-0.004178073 0 0 |
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Errata
Below is the list of erratum that are relevant to changes made on this page that no longer match the report. The full list can be found on the Home Page.
[1] Page 56, the Rate section should specify body-axis quantities relative to the local frame: Volume II Report ↩︎