Spherical shape stability of shells and cavities

Thin-walled shells characteristic of their light weight and strength are used everywhere – in household items to ocean liners and space rockets. Their applications are so diversified and uncountable that one can safely say, ”The world consists of shells; the world rests on shells.” After all, the Earth’s crust is also a shell. The wide application of thin-walled structures has triggered the need for developing reliable methods to calculate their strength and stability, and this is just the research subject of the shell theory, a new branch of mechanics arisen in the past century. The important role is found to be played by their interaction with working media. The present paper discusses the issues on the stability of spherical thin-walled shells and gas cavities in liquid.