NASA formula, can someone decipher

[Stevetuc]

(04-18-2020 08:42 PM)Don Shepherd Wrote:  See the attached formula from an IBM employee newsletter from 1969 related to the space program. Does anyone know what all this (the delta t) means?

Both the temperature ratio and the pressure ratio(delta) have the subscript t.
In the key, the t subscript = total conditions and o subscript = reference conditions