A methodology for exploring the design space for lunar return entry trajectories and vehicle design is proposed, using the Orion Crew Exploration Vehicle as an example. This methodology simplifies the vehicle and trajectory design space by focusing on two entry parameters: flight-path angle at entry interface and hypersonic lift-to-drag ratio. Flight-path angle is a governing trajectory design parameter, while lift-to-drag ratio captures entry vehicle performance. Landed accuracy, aeroheating, deceleration, other entry constraints are addressed within the design space. Several entry trajectory scenarios are examined, consistent with the current Orion concept of operations. Analysis and evaluation of parameters is accomplished through high-fidelity six-degree-of-freedom simulation using NASA's ANTATRES simulation. Monte Carlo analysis indicates that the proposed methodology provides a valid means of designing entry trajectories to maximize performance margin while satisfying constraints for a given vehicle capability. Additionally, results indicate that, while performance margin decreases with increasing entry range and lower lift-to-drag ratios, adequate performance margin exists for the Orion Crew Module for the current lunar return concept of operations and vehicle design.