Heat Transfer Operability Limits for an Actively and Passively Cooled Hypersonic Vehicle

For a trimmed hypersonic waverider vehicle, computations were performed to investigate the operability limits that occur due to excessive heating of the external surface, including the nose region and combustor wall region, and the heating of the liquid hydrogen fuel, which is used as coolant. The operability limits computed include the maximum values of flight Mach number, dynamic pressure, and the flight time before one of several temperature limits is exceeded. To compute operability limits, efficient aerodynamic heating and thermal protection system models were added to the reduced-order model MASIV, which contains an advanced combustion analysis and a trim code. 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. Results also show the effect of varying the fraction of fuel in the active cooling system that is recirculated back into the fuel tank. Recirculating the heated fuel raises the fuel tank temperature and decreases the fuel density (increasing the volume); the analysis computes the maximum flight time before the fuel tank temperature and fuel volume exceed acceptable limits. By extending the active cooling system to a small region of the inlet (instead of just around the combustor), the operability limits are increased from a flight Mach number of 7.3 to 8.6.