Efficient General Computational Method for Estimation of Standard Atmosphere Parameters

Abstract

Knowledge of standard air temperature, pressure, density, speed of sound, and viscosity as a function of altitude is essential information in aircraft design, performance testing, pressure altimeter calibration, and several other aeronautical engineering and aviation science applications. A new efficient computational method for rapid calculations of standard atmospheric parameters up to 86 orthometric km is presented. Additionally, mass and weight of each standard atmospheric layer were calculated using a numerical integration method. The sum of all fractional masses and weights represents the total mass and weight of Earth’s atmosphere. The results obtained here agree well with measurements and models of the real atmosphere. Various ISA scale heights were estimated from numerical integration of atmospheric masses and weights. The nature of the geopotential and the orthometric heights and the definition of MSL have been explained. Essential thermodynamic considerations of still and dry air were highlighted. In addition to general working equations for air pressure and density vertical distribution for each atmospheric layer an extensive table of calculated values up to 86 km has been provided in appendix. Several models of air viscosity were also compared. It was found that simple Granger’s model agrees well with the widely accepted Sutherland-type viscosity equation. All computations were performed with the fourteen significant-digits accuracy although only seven significant digits were typically presented in tables.

Author

• Daidzic, Nihad E, Ph.D., Sc.D. Embry-Riddle Aeronautical University

Keywords

• standard atmosphere
• ideal-gas law
• isothermal atmosphere
• constant temperature lapse-rate atmosphere
• mass and weight of atmosphere
• scale heights
• viscosity
• geopotential height
• orthometric height
• Aerodynamics and Fluid Mechanics
• Atmospheric Sciences
• Engineering Physics