Sensitivity of Flight Dynamics of Hypersonic Vehicles to Design Parameters

Dynamic stability is an important concern for air-breathing hypersonic vehicles. Certain design strategies can be used to ensure the stability of the vehicle, such as placing ballast at the nose of the vehicle or increasing the size of the horizontal stabilizers. However, these changes may also increase the drag and thus fuel consumption of the vehicle. To investigate these tradeoffs, this paper uses a trajectory analysis to calculate the sensitivity of both stability parameters and fuel consumption. The most effective parameter to affect the stability is the location of the center of gravity, but other design variables explored include dihedral angle of the horizontal stabilizers and several others. The trajectory used includes both ram-mode and scram-mode flight conditions, and the Mach number at which ram-scram transition occurs is another important consideration. To investigate these sensitivities, a vehicle model called MASTrim designed specifically for flight dynamics applications has been developed. The low-order fundamental model used accounts for complex phenomena such as shock interactions, fuel-air mixing, finite-rate chemistry, and the adjusting shape of the nozzle exhaust plume.