Aerodynamics of Model Rocketry and Drag Coefficients
Predicting a model rocket's peak altitude (apogee) requires modeling the aerodynamic forces acting on it during flight. The primary resisting force is aerodynamic drag, which acts in opposition to the rocket's velocity vector.
The drag force is calculated as: \(F_d = \frac{1}{2} \rho v^2 C_d A\), where \(\rho\) is air density (1.225 kg/m³ at sea level), \(v\) is rocket velocity, \(A\) is the cross-sectional area: \(A = \pi \left( \frac{d}{2} \right)^2\), and \(C_d\) is the drag coefficient. The drag coefficient is determined by body tube friction, fin area (approximately 0.05 added per square decimeter), and nose cone shape (Ogive = 0.45, Parabolic = 0.50, Cone = 0.60, Flat = 0.85). Lower drag coefficients yield significantly higher apogees.