A common bulkhead (CB) structure that separates the oxidizer and fuel regions without an interstage single tank reduces the weight of the propellant tanks of launch systems. CB structures can be designed into various shapes, such as hemispherical, elliptical, or torispherical. Therefore, a lightweight shape with high structural stability is important. ABAQUS, a commercial software for nonlinear finite element analysis, was employed in this study to model and analyze elliptical CB structures with eccentricities. The single dimple imperfection approach (SDIA) was applied to simulate the geometric initial imperfection, and thermal–structural coupled analyses were performed to model the thermal imperfection. In order to predict the buckling knockdown factor (KDF), nonlinear postbuckling analyses were performed. With increasing eccentricity, the KDF decreased, altering the buckling characteristics. The lowest KDF was obtained from the model with semiminor radius ( a ) = 0.40 m. However, the derived KDFs in this paper were higher than NASA′s buckling design criteria by at least 88.89% and 55.43%, respectively, from NASA SP‐8032 and CR‐1457. Therefore, the present KDFs may enable lightweight CB structural designs.
Kim et al. (2026) studied this question.