The low drag altitude is defined as the altitude at which a body in orbit experiences an air deceleration smaller than 0.00001 m / s^2; about one millionth of earth's gravity. Earth's low drag altitude for a typical spacecraft is one hundred and fifty kilometers. When the atmosphere is practically a vacuum, the low drag altitude is zero.

Given deceleration, orbital velocity and column height of the atmosphere, low drag altitude is calculated which is in turn used to calculate low drag orbital velocity.

orbital drag = deceleration * orbital velocity * orbital velocity
maximum drag = 0.00001

low drag altitude = 0
if ( orbital drag > maximum drag ) {
    low drag altitude = log( orbital drag / maximum drag ) * column height
}

low drag orbital = ground orbital * sqrt( radius / ( radius + low drag altitude ) )
 

This is used in astropolis, atmospheric spacecraft, multi stage spacecraft, and spacecraft cost.
 
 

Feedback   Free Electronic Nation Home    Spacecraft   GNU Free Documentation License