pub fn launch_lug_drag(
length_m: f64,
outer_radius_m: f64,
inner_radius_m: f64,
mach: f64,
) -> Result<(f64, f64), AeroError>Expand description
Parasitic drag of a launch lug (Niskanen 2009 eq. 3.95–3.96): the coefficient
max{1.3 − 0.3 l/d, 1} (C_D•)_stag on the area π r_ext² − π r_int² max{1 − l/d, 0}, returned
as (coefficient, area_m2).
A short lug blocks only its wall’s annulus and drags like a wire (Hoerner’s 1.1, the 1.3
factor); a lug longer than its diameter blocks its whole face like a solid protrusion. d is
taken as the outer diameter 2 r_ext: Niskanen’s rail pin, a solid lug “with a length equal to
its diameter”, only reads that way.
§Errors
AeroError::Domain for a negative or non-finite Mach number, or for a
negative length, a non-positive outer radius, or an inner radius outside [0, r_ext].