The reference to the Fay-Riddell equation is:

Fay, J.A. and Riddell, F.R., "Theory of Stagnation Point Heat Transfer in Dissociated Air", Journal of the Aeronautical Sciences, Vol. 25, No.2, pg. 73-85, February 1958.

Note the date (I was in Kindergarten then). Most of the really good work in aerospace was done between 1950-1970. The Fay-Riddell equation is to aerothermodynamics like the Maxwell equations are to electrical engineering.

The best representation of the Fay-Riddell equation is in:

"Hypersonic and High Temperature Gas Dynamics" by John D. Anderson, Jr., McGraw-Hill, Inc., 1989.

In Anderson, go to page 634 amd see Equ. 17.90. This form of the Fay-Riddell equation assumes a spherical nose, chemically frozen boundary layer and fully catalytic wall. This is the most accurate form of the Fay-Riddell but is hard to use. There are dumbed down versions that over predict the wall heat flux but are easier to use.

Gary