Aerospace Blockset™

Non-Standard Day 310 - Implement MIL-HDBK-310 climatic data

Library

Environment/Atmosphere

Description

The Non-Standard Day 310 block implements a portion of the climatic data of the MIL-HDBK-310 worldwide air environment to 80 km (geometric or approximately 262,000 feet geometric) for absolute temperature, pressure, density, and speed of sound for the input geopotential altitude.

The Non-Standard Day 310 block icon displays the input and output units selected from the Units list.

Dialog Box

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 MIL-HDBK-310.

1976 COESA-extended U.S. Standard Atmosphere

This selection is linked to the COESA Atmosphere Model block. See the block reference for more information.

MIL-HDBK-310

This selection is linked to the Non-Standard Day 310 block. See the block reference for more information.

MIL-STD-210C

This selection is linked to the Non-Standard Day 210C block. See the block reference for more information.

Atmospheric model type

Select the representation of the atmospheric data.

`Profile`	Realistic 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.
`Envelope`	Uses extreme atmospheric values at each altitude. Recommended for vehicles only horizontally traversing the atmosphere without much change in altitude.

Extreme parameter

Select the atmospheric parameter which is the extreme value.

`High temperature`	Option always available
`Low temperature`	Option always available
`High density`	Option always available
`Low density`	Option always available
`High pressure`	This option is available only when `Envelope` is selected for Atmospheric model type.
`Low pressure`	This option is available only when `Envelope` is selected for Atmospheric model type.

Frequency of occurrence

Select percent of time the values would occur.

`Extreme values`	This 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.

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)

Action for out of range input

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

Inputs and Outputs

Input	Dimension Type	Description
First		Contains the geopotential height.

Output	Dimension Type	Description
First		Contains the temperature.
Second		Contains the speed of sound.
Third		Contains the air pressure.
Fourth		Contains the air density.

Assumptions and Limitations

All values are held below the geometric altitude of 0 m (0 feet) and above the geometric altitude of 80,000 meters (approximately 262,000 feet). The envelope atmospheric model has a few exceptions where values are held below the geometric altitude of 1 kilometer (approximately 3,281 feet) and above the geometric altitude of 30,000 meters (approximately 98,425 feet). These exceptions arise from lack of data in MIL-HDBK-310 for these conditions.

In general, temperature values are interpolated linearly, and density values are interpolated logarithmically. Pressure and speed of sound are calculated using a perfect gas law. The envelope atmospheric model has a few exceptions where the extreme value is the only value provided as an output. Pressure in these cases is interpolated logarithmically. These envelope atmospheric model exceptions apply to all cases of high and low pressure, high and low temperature, and high and low density, excluding the extreme values and 1% frequency of occurrence. These exceptions arise from lack of data in MIL-HDBK-310 for these conditions.

Another limitation is that climatic data for the region south of 60°S latitude is excluded from consideration in MIL-HDBK-310.

This block uses the metric version of data from the MIL-STD-310 specifications. Certain data within the envelope are inconsistent between metric and English versions for low density, low temperature, high temperature, low pressure, and high pressure. The most significant differences occur in the following values:

For low density envelope data with 5% frequency, the density values in metric units are inconsistent at 4 km and 18 km and the density values in English units are inconsistent at 14 km.
For low density envelope data with 10% frequency,
- The density values in metric units are inconsistent at 18 km.
- The density values in English units are inconsistent at 14 km.
For low density envelope data with 20% frequency, the density values in English units are inconsistent at 14 km.
For low temperature envelope data with 20% frequency, the temperature values at 20 km are inconsistent.
For high pressure envelope data with 10% frequency, the pressure values in metric units at 8 km are inconsistent.

Reference

Global Climatic Data for Developing Military Products (MIL-HDBK-310), 23 June 1997, Department of Defense, Washington, D.C.