<p>The design and manufacturing technologies used for inflatable aeroshells, a new concept in atmospheric entry systems, are being increasingly researched for improving the performance of aeroshells. In this study, we developed a feasible design method for an inflatable aeroshell to obtain a tension-shell structure with a single inflatable ring and applied it to ballistic suborbital flights of sounding rockets. The requirements of an inflatable aeroshell can be defined in terms of the maximum aerodynamic heating experienced during atmospheric entry, resistance to maximum aerodynamic loads, durability of gas filling, and terminal velocity that enables a soft landing for recovery. The upper limit of the ballistic coefficient required for the vehicle was determined based on the aforementioned requirements. This ballistic coefficient facilitated the direct determination of the aeroshell size with the largest vehicle mass considering the durability of the aeroshell. The proposed design method was used to estimate the inflatable aeroshell size required for application to sounding rocket flights; the mass of the aeroshell was approximately 20% of the total vehicle mass. Furthermore, the storage space was estimated using the storage method by wrapping a gas-evacuated inflatable aeroshell around a central pillar. The study findings confirm that the estimation is appropriate when compared with an actual flight capsule.</p>