Ground orbital is the orbital velocity at zero altitude. Since ground orbital velocity is equal to the square root of the product of radius and gravity and since, for a given density, gravity is proportional to the radius; therefore for a given density, ground orbital velocity is proportional to the radius. Ground orbital velocity for earth is about seven thousand nine hundred meters per second. Ground orbital velocity for mars is about three thousand five hundred meters per second. Ground orbital velocity for luna is about one thousand seven hundred meters per second.

Given gravity and radius, ground orbital is calculated which is in turn used to calculate low drag orbital velocity and orbital velocity at an altitude.

ground orbital = sqrt( gravity * radius )

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

orbital velocity = ground orbital * sqrt( radius / ( radius + altitude ) )
 

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

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