An aerothermodynamic performance analysis is conducted for a supersonic transport propulsion system, evaluating the feasibility of a single-stage and a two-stage fan configuration. The propulsion system is modeled using a parametric approach, incorporating variations in fan pressure ratio, bypass ratio, and high-pressure turbine inlet temperature to assess their impact on cruise and off-design performance. A two-shock external compression intake is assumed. The analysis is performed for a cruise speed of Mach 1.7 at an altitude of 60,000 feet, similar to the cruise conditions proposed for the Boom aircraft. The results demonstrate that the two-stage fan configuration offers superior performance, achieving an 8.5% increase in specific range compared to the single-stage fan while maintaining a reduced fan diameter and lower overall engine mass. The off-design analysis reveals a significant performance penalty associated with the long-proposed idea of boom-less, overland supersonic cruise. A 22% reduction in specific range is predicted when shifting from a Mach 0.95 to Mach 1.2 over land cruise. The off-design analysis further highlights the efficiency advantages of the two-stage fan, with a 3.5% reduction in specific fuel consumption at lower Mach numbers and a broader operational envelope.