World of Aerospace
What is Standard Atmosphere, How to Calculate Standard Atmosphere Computationally, Experimentally, Pressure Altitude,Density Altitude, Temperature Altitude, Geometric Altitude, Geopotential Altitude, Absolute Altitude, Value of Gravitational acceleration g
and Standard Atmosphere Table...
Standard Atmosphere
The pressure, density and
temperature can be defined as the functions of the altitude. This is
known as the standard atmosphere. The standard atmosphere is useful as
it gives us a way to find out the pressure, density and temperature
values at a certain altitude above the surface of the earth or above
sealevel.
Secondly, the standard
atmosphere is useful as it gives us a way to determine altitude if we
know the local density, pressure and temperature values. We can use the
standard atmospheric data and by comparison we can calculate the
altitude which can be either pressure, density or temperature altitude.
One standard atmospheric method
is to defined the temperature as a function of the altitude. The
temperature values are computed in Kelvin. The temperature of the
atmosphere and this standard atmosphere method is based on experiment
using hot air balloons to measure pressure, density and temperature
above the surface of the earth.
There are two layers which are
important in the standard atmosphere plot if the temperature versus
altitude is being used. One is the gradient layer and the other is the
isothermal layer. In the gradient layer the temperature of the
atmosphere either decrease or increase according to a fixed slope value.
If the slope is negative temperature decreases in that region. If the
slope is positive the temperature rises in that region. Secondly, in the
isothermal region as the name suggests the temperature of the atmosphere
remains constant in that region. Here in this region the temperature of
the atmosphere neither increase nor decrease.
How to Calculate Standard
Atmosphere Experimentally:
The
standard atmosphere can be calculated experimentally and thus generating
the pressure, density and temperature plots versus altitude by using hot
air balloons. Pressure, density and temperature sensors are mounted in
large helium filled balloons and released. The balloons rise high in the
air and record the surrounding pressure, density and temperature values
at different increments of height. The data is then transmitted to a
ground station where the data is collected and thus analyzed.
Altitude:
Altitude of a flying vehicle is
defined as the distance above the ground to the point where the aircraft
is flying. In simple words, altitude is the distance above the ground.
Types of Altitudes:

Geometric Altitude
 Geopotential Altitude

Absolute Altitude

Pressure Altitude

Density Altitude

Temperature Altitude
Geometric Altitude:
The geometric
altitude of a flying vehicle is the height or the distance above the
surface of the earth to the point where the vehicle is flying.
Absolute
Altitude of a flying vehicle or a space vehicle is the height or the
distance from the center of the earth to where the vehicle is flying.
Mathematically, Absolute Altitude = Geometric Altitude + Radius of the
Earth.
Pressure
altitude is the altitude above the ground to the point where the
atmospheric pressure has some fixed value defined by that altitude.
Density
altitude is the altitude above the ground to the point where the
atmospheric density has some fixed value defined by that altitude.
Temperature
altitude is the altitude above the ground to the point where the
atmospheric temperature has some fixed value defined by that altitude.
Free Calculation Programs on
Standard Atmosphere

Calculate Standard Atmosphere Table

Calculate Geopotential Altitude

Calculate Pressure Altitude

Calculate Density Altitude

Calculate Temperature Altitude
 Calculate Value of g at Altitude
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