Drag Coefficient

[3allan]

The drag coefficient of the generally multi-staged rocket needs to be determined as a function of geometry, Mach number, and possibly Reynolds number.

The drag coefficient is a "slop" term that accounts for variations in incoming flow, vehicle orientation, etc. experienced during flight. As such, the procedure in finding an accurate drag coefficient that's valid for subsonic, supersonic, and hypersonic flight regimes of a slender-bodied vehicle at small angles of attack is both extremely important and difficult.

The current implementation makes no attempt at determining the drag coefficient; its value is set to a constant (1) and is located here. A seemingly popular method of determining the drag coefficient (as well as other relevant aerodynamic coefficients) of such a vehicle is outlined in James Barrowman's dissertation "The Practical Calculation of the Aerodynamic Characteristics of Slender Finned Vehicles" (NASA document ID: 20010047838). There are errors in places throughout his work, so results should be regularly checked.

Barrowman's method of determining the drag coefficient requires use of second-order shock expansion theory to determine the pressure distribution over a rocket's nosecone.

Priority: High

• The drag coefficient strongly dictates important flight characteristics through the atmosphere and in orbit
  • Suborbital rockets are strongly influenced by the drag coefficient (maximum velocity, apogee, etc.)
  • Orbital vehicles sometimes use a ballistic coefficient in place of the drag coefficient, but regardless are affected by orbit decay
• We want to have an independent method from other rocketry programs for calculating the drag coefficient