Performance Evaluation of a Conceptual Turbo-Ramjet Engine for a Two Stage To Orbit Launch System

The increasing demand for efficient, cost-effective, and reusable launch systems has driven research into novel propulsion technologies for two-stage-to-orbit (TSTO) vehicles. This study investigates a conceptual turbo-ramjet propulsion system, proposed by Princeton Satellite Systems. The analysis presented uses an exergy-based performance framework to assess energy utilization, component-level losses, and improvement opportunities across both turbofan and ramjet regimes. Results show that while propulsive efficiency improves with Mach number, combustion remains the dominant source of irreversibility, accounting for over 68\% for turbofan and over 85\% of losses for ramjet. A parallel sustainability assessment highlights the challenges of large-scale hydrogen fuel supply, showing that cleaner production methods are either too energy-intensive or reliant on fully decarbonized electricity sources, while distribution via natural gas pipelines introduces significant cooling energy penalties. These findings highlight that although hydrogen-powered turbo-ramjet propulsion possesses substantial performance potential for TSTO applications, realizing improvements in system efficiency will necessitate not only the use of high-energy fuels but also a strategic reduction of exergy losses related to combustion as well as ongoing investment in clean hydrogen infrastructure.