Abstract The dynamics of hypersonic flight present significant challenges due to extreme thermal conditions and the strong coupling between the airframe and propulsion system, making vehicle design highly complex. Scramjet engines, while structurally simple, require extensive optimization, particularly in material selection and thermodynamic efficiency. To address these challenges, this study developed and integrated a complete six-degree-of-freedom (6DoF) dynamic model with a detailed thermodynamic representation of a scramjet-powered LOGAN hypersonic vehicle. This coupled framework enables a holistic assessment of the interactions between flight dynamics and engine thermodynamics, capturing the mutual influence of propulsion variations on vehicle trajectory and vice versa. The model was validated through simulations of a high-speed cruise scenario, where the vehicle transitioned from 65,000 to 100,000 ft at Mach 10, demonstrating stable altitude capture and performance consistency. The results revealed that scramjet operation at higher Mach numbers enhances thermal and exergy efficiencies, exceeding 70% at Mach 10, although these values do not include propulsive efficiency effects. However, the improved thermodynamic performance at higher Mach regimes is accompanied by significantly higher fuel demand, with fuel mass flow rates stabilizing above 6.5 kg/s at Mach 10 compared with values below 3 kg/s at Mach 5, while intermediate regimes between Mach 7 and Mach 8 presented a more balanced operational condition between efficiency and fuel consumption. The propulsion model effectively regulated thrust-to-drag balance, ensuring an efficient transition between flight phases. The combustion process was identified as the primary source of exergy loss, with heat addition generating peaks exceeding 3 × 10 6 W, reinforcing the need for advanced fuel injection and thermal management strategies. The integrated approach developed in this study provides a valuable framework for assessing next-generation conceptual hypersonic vehicles studies.
Moura et al. (Mon,) studied this question.