Let's collect the facts we've reverse-engineered from KSP's drag model,
that we sometimes need to know when playing KSP.
By convention, people describe drag, the force opposite the airspeed, as a product
D = ½ ρ V² A Cd
for an object with frontal area A, in m², moving at speed V (m/s) through air with density ρ (1kg/m³ at sea level). The coarse dependence on speed, etc, is factored out leaving the more subtle dependence on speed in a coefficient Cd. Cd is dimensionless, independen