Abstract: It is well known that the buckling response of thin shell structures can be very sensitive to the presence of small geometric imperfections in the shell. The Shell Buckling Knockdown Factor Project (SBKF) was established by the NASA Engineering and Safety Center to develop new analysis-based shell buckling design recommendations for stiffened-metallic and composite launch-vehicle shell structures. Large-scale buckling tests are used to validate the modeling and analysis methods applied in dev…