Hull is a term that can refer to the both the entire body and framework of a Ship or just its external layer. Hulls are typically constructed out of metal, composites, or plastics, although alternative materials such as ceramic or even organic matter like in the Tournan Hive Ship can be used. As an internal framework, the hull serves as the core of a ship to which other things, like engines or crew compartments, are attached. It must be able to withstand the stresses of the acceleration and deceleration any vessel encounters during its travel, as well as managing the internal tension and strain inherent in giant capital ships. Most vessels have an airtight hull that covers the exterior of the craft, which provides both structure and protection from hazards like micrometeorites and the vacuum of space. Warships may have a reinforced hull that is armored to withstand enemy fire to complement or substitute for Shields.