An airship is a type of powered flying machine that is designed to float in the air, utilizing the principles of buoyancy. These vehicles generate lift by containing a lifting gas, such as heated air or hydrogen, within a voluminous envelope structure. The design can range from non-rigid airships, which maintain lift primarily through the buoyant gas, to rigid airships, which feature an internal skeleton to maintain shape and withstand pressure differentials. Propulsion is typically achieved through external motors and propellers, allowing for controlled movement. The operation of airships involves navigating using aerodynamic principles, relying on directional control surfaces and precise management of altitude through gas volume and internal ballast systems.