The current Creo/Simulate is unable to perform buckling analysis on pressurized structures. Every rocket and airplane uses pressure stabilization in order to dramatically increase vehicle stiffness without the need to "add solid mass". The lack of this ability is a huge hole in PTCs Simulate offereing as it is THE major strength analysis that all of aerospace needs for primary structural load paths.
My understanding is that other codes accomplish this by defining the pressure as a pre-load somehow.
4/14/2015- Everyone at my company is now being asked to use NX for all future development. I have learned enough about NX NASTRAN to confirm that for buckling analysis, pressure is entered as a pre-load. Creo really, really, is at a disadvantage in many mega-aerospace companies without this ability.