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The density altitude is the altitude relative to standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation. In other words, the density altitude is the air density given as a height above mean sea level. The density altitude can also be considered to be the pressure altitude ...
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
A primary use of this model is to aid predictions of satellite orbital decay due to atmospheric drag. This model has also been used by astronomers to calculate the mass of air between telescopes and laser beams in order to assess the impact of laser guide stars on the non-lasing telescopes.
"Density altitude is a measure of air density, expressed as the altitude that corresponds to a given air density under standard atmospheric conditions." As with air density, air pressure, temperature, humidity, etc., we can then talk about the density altitude observed at a given place and time, but places and times of observation aren't part ...
To calculate the density of air as a function of altitude, one requires additional parameters. For the troposphere, the lowest part (~10 km) of the atmosphere, they are listed below, along with their values according to the International Standard Atmosphere, using for calculation the universal gas constant instead of the air specific constant:
A reference atmospheric model describes how the ideal gas properties (namely: pressure, temperature, density, and molecular weight) of an atmosphere change, primarily as a function of altitude, and sometimes also as a function of latitude, day of year, etc. A static atmospheric model has a more limited domain, excluding time.
In this episode of Football 301, Nate Tice and Matt Harmon are ringing in the New Year with their resolutions for NFL teams as the playoff race heats up. Matt's resolutions focus on teams in the ...
Compressiblity is noticeable from Mach 0.3. And depends on what "noticeable" means. If by it we mean as commonly implied "noticeable on drag effects" then from 0.3 to up 0.7 the Prandtl–Glauert correction works decently. So you notice it but it's easy to calculate a "reasonably precise" value for most of the involved quantities.