Bobcent

Hello!

I have some questions about the drag equation and aerodynamics:

[itex]F = \frac{1}{2}ρv^2CA[/itex]

I'm trying to calculate the atmospheric drag on a streamlined body (the drag coefficient will be a very small number) with a velocity of about 8 km/s at about 38,000 meters altitude, where the atmospheric density is only about [itex]5.4\times10^-3[/itex][itex]kg/m^3[/itex]. So my question is; is the drag equation valid even for these extreme values, or is there a better equation that I can use?

Secondly, which is the optimal geometrical shape for [itex]\frac{Volume}{Drag}[/itex]? Is it a streamlined body shape? If it is a streamlined body shape, what is the equation for calculating its volume, and what is the equation for calculating its reference area? Can't find it!

Really appreciate any help on this!