JD,
it might be the formula of Raleigh for supersonic speeds :
Pt-p/p =[ 166,92158M^7/(7M^2-1)^2,5]
-1
Pt = Total Air Pressure
p = Static Air Pressure
M^7 = Mach to the power 7
M^2 = Mach to the power 2(square)
^2,5 = power 2,5
/ = diveded by. ...
hope this helps, but don't try to commit this formula to memory.
bm.