@UVU_Team_Rocket --
Yes, the empirical data are a result of years -n- years of subsonic aerodynamic research and development.
Check Appendix II -- Dr. Gregorek's suggested reading list.
Hmmm ...
If one wants to understand model rocket drag, I would say that one needs to read and understand ALL of it
But if you want the punch line, maybe read the section: COMBINING DRAG COEFFICIENTS starting at the bottom of page 26 ( PDF page 30 ).
That section calculates the zero-lift drag coefficient of a rocket by combining the individual coefficients of drag of each wetted component.
But it may not make much sense unless one understands the concepts developed in pages 1-26.
At least a print out of the List of Symbols in Appendix III
I believe Appendix I starting on page 47 is a deeper dive into applying the concepts developed in the paper to a different rocket with arbitrary properties.
Appendix II on page 50 is a bibliography.
Appendix III on page 51 is a List of Symbols which is very handy to have when reading pages 1-50.
Final note: the specifics presented in the paper are for subsonic model rockets.
Transsonic aerodynamics are a whole 'nuther animal ...
HTH.
-- kjh