For a scramjet-powered waverider vehicle, computations were performed to investigate the operability limits that occur due to excessive heating of the external surface and the heating of the hydrogen fuel, which is used as coolant. To compute operability limits, efficient aerodynamic heating and thermal protection system models were added to the reduced order model MASIV. Results show the effects of varying the thickness of the three-layer thermal protection system that consists of a radiation shield, an insulation layer and the vehicle wall. The heat exchanger heat flux is modeled assuming the hydrogen fuel is a supercritical fluid and lookup tables for the fuel properties at supercritical conditions are incorporated. By extending the active cooling system to a small region of the inlet, the operability limits are increased from a flight Mach number of 7.3 to 8.6. Optimizations for the active and passive thermal protection systems are performed. For the passive TPS, the minimum required insulation thickness is computed. For the active TPS, the parameters impacting the final fuel temperature are optimized to find the minimum fuel temperature at the end of a 40-minute cruise.