What is a separate, streamlined enclosure on an aircraft for housing crew, cargo, or an engine called?

The term for a separate, streamlined enclosure on an aircraft that is designed for housing crew, cargo, or an engine is known as a nacelle. Nacelles are specifically designed to improve the aerodynamics of the aircraft while also serving functional purposes. For example, engine nacelles house the engines of larger aircraft, providing protection and allowing for easier maintenance. Additionally, they contribute to the overall balance and performance by minimizing turbulence and drag during flight.

The other options, while related to aviation concepts, do not accurately define this specific structural component. Rotors are associated with helicopters and refer to the rotating blades that provide lift. VTOL (Vertical Take-Off and Landing) refers to aircraft capable of taking off and landing vertically, rather than denoting a specific structure. Logistics pertains to the planning and execution of the movement and support of forces, rather than a physical structure on an aircraft. Thus, nacelle is the most precise and appropriate answer to the question.