The aim of this work is to provide an upper estimate of the theoretical maximum specific thrust of the hydrocarbon fueled scramjet An idealized thermodynamic cycle analysis is carried out to evaluate the performance of scramjet engines at different flight conditions, inlet pressure ratio and fuel equivalence ratio. Contrary to known Brayton cycles for the gas-turbine and ramjet engine, the inherent total pressure loss with heating must be taken into account in the high speed flow of the scramjet. The results show that the specific thrust initially grows asymptotically with fuel equivalence ratio, then reaches a maximum, and finally reduces rapidly for a given flight Mach number. The optimum inlet pressure ratio and fuel equivalence ratio at which the value of the specific thrust attains a maximum are presented. Variations of maximum specific thrust with freestream Mach numbers and material temperature limit are analyzed respectively. (C) 2014 Elsevier Ltd. All rights reserved.