Documentation

COESA Atmosphere Model

Implement 1976 COESA lower atmosphere

Library

Environment/Atmosphere

Description

The COESA Atmosphere Model block implements the mathematical representation of the 1976 Committee on Extension to the Standard Atmosphere (COESA) United States standard lower atmospheric values for absolute temperature, pressure, density, and speed of sound for the input geopotential altitude.

Below 32,000 meters (approximately 104,987 feet), the U.S. Standard Atmosphere is identical with the Standard Atmosphere of the International Civil Aviation Organization (ICAO).

The COESA Atmosphere Model block icon displays the input and output units selected from the Units list.

Parameters

Units

Specifies the input and output units:

Units

Height

Temperature

Speed of Sound

Air Pressure

Air Density

Metric (MKS)

Meters

Kelvin

Meters per second

Pascal

Kilograms per cubic meter

English (Velocity in ft/s)

Feet

Degrees Rankine

Feet per second

Pound-force per square inch

Slug per cubic foot

English (Velocity in kts)

Feet

Degrees Rankine

Knots

Pound-force per square inch

Slug per cubic foot

Specification

Specify the atmosphere model type from one of the following atmosphere models. The default is 1976 COESA-extended U.S. Standard Atmosphere.

MIL-HDBK-310

This selection is linked to the Non-Standard Day 310 block. See the block reference for more information. Selecting MIL-HDBK-310 enables the parameters Atmospheric model type, Extreme parameter, Frequency of occurrence, and Altitude of extreme value.

MIL-STD-210C

This selection is linked to the Non-Standard Day 210C block. See the block reference for more information. Selecting MIL-HDBK-310 enables the parameters Atmospheric model type, Extreme parameter, Frequency of occurrence, and Altitude of extreme value.

Atmospheric model type

Select the representation of the atmospheric data.

ProfileRealistic atmospheric profiles associated with extremes at specified altitudes. Recommended for simulation of vehicles vertically traversing the atmosphere or when the total influence of the atmosphere is needed.
EnvelopeUses extreme atmospheric values at each altitude. Recommended for vehicles only horizontally traversing the atmosphere without much change in altitude.

Selecting Specification > MIL-HDBK-310 or Specification > MIL-STD-210C enables this parameter.

Extreme parameter

Select the atmospheric parameter that is the extreme value.

High temperatureOption always available
Low temperatureOption always available
High densityOption always available
Low densityOption always available
High pressureThis option is available only when Envelope is selected for Atmospheric model type
Low pressureThis option is available only when Envelope is selected for Atmospheric model type

Selecting Specification > MIL-HDBK-310 or Specification > MIL-STD-210C enables this parameter.

Frequency of occurrence

Select percent of time the values would occur.

Extreme valuesThis option is available only when Envelope is selected for Atmospheric model type.
1%Option always available
5%This option is available only when Envelope is selected for Atmospheric model type.
10%Option always available
20%This option is available only when Envelope is selected for Atmospheric model type.

Selecting Specification > MIL-HDBK-310 or Specification > MIL-STD-210C enables this parameter.

Altitude of extreme value

Select geometric altitude at which the extreme values occur. Applies to the profile atmospheric model only.

5 km (16404 ft)
10 km (32808 ft)
20 km (65617 ft)
30 km (98425 ft)
40 km (131234 ft)

Selecting Specification > MIL-HDBK-310 or Specification > MIL-STD-210C enables this parameter.

Action for out-of-range input

Specify if out-of-range input invokes a warning, error, or no action.

Inputs and Outputs

InputDimension TypeDescription
First Contains the geopotential height.

OutputDimension TypeDescription
First Contains the temperature.
Second Contains the speed of sound.
Third Contains the air pressure.
Fourth Contains the air density.

Assumptions and Limitations

Below the geopotential altitude of 0 m (0 feet) and above the geopotential altitude of 84,852 m (approximately 278,386 feet), temperature values are extrapolated linearly and pressure values are extrapolated logarithmically. Density and speed of sound are calculated using a perfect gas relationship.

Examples

See the aeroblk_calibrated model, the aeroblk_indicated model, and the airframe in aeroblk_HL20 for examples of this block.

Reference

U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C.

Introduced before R2006a


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