the present invention is a composite munitions vault adapted for use underground . the munitions vault includes a watertight , non - corrosive , composite hull . the hull includes an upper section with a top , two short sides , and two long sides , where each of the two short sides and two long sides have a hexoid shape , and the upper section has no flat surfaces . the hull also includes a lower section with a convex bottom and a gravity ring spanning the circumference of the vault between the upper and lower sections .