Aerospace engineering is a complex, rapidly changing field. Its primary application is the design and development of flight vehicles, such as aircraft, missiles, spacecraft, and satellites. Aerospace engineering is also important and applicable to other vehicles and systems – including submarines, automobiles, trucks, and rapid transit – and can include advanced robotics, exotic materials, and computational simulations. Working in both aeronautics (planes) and astronautics (space), aerospace engineers conduct research and design and develop vehicles and systems for air, space, and any fluid environment. Aerospace engineers commonly focus on specific areas in the fields of aerodynamics and propulsion, dynamics and controls, or materials and structures.