Operating costs and fossil fuel consumption of civil transports can be reduced through use of efficient counter rotating open rotor (CROR) propulsion systems, thereby addressing both key industry needs and long-term NASA technical goals. To develop such next-generation systems, multiple design variables must be assessed and optimized efficiently within a conceptual design software environment. A blend of physics-based, low- and mid-fidelity tools featuring rapid turnaround time and ease of setup can provide this capability; implementation represents a serious technical challenge, though, and there is a high premium on developing tools that are both sufficiently accurate to capture current technology performance metrics while permitting the rapid re-calculations necessary for design trades. The proposed approach centers on a blend of enhanced features and novel departures for two complementary aeroanalysis methods: an evolved version of an established subsonic lifting surface free wake mdoel for propellers as a fast,'low-fidelity' tool; and a more computationally intensive, fully compressible Cartesian Grid Euler model as a 'mid-fidelity' tool. The projected Phase I will implement and test key modeling and formulation improvements for these methods to enable them to support the design of multi-stage open rotor configurations to meet current and projected performance targets.