Aerospace engineering is the branch of engineering behind the conception, design, construction, and operation of aircraft and spacecraft, including all of their associated systems and the exciting scientific problems involved in their development. Aerospace systems are high-technology products designed to operate reliably in hostile environments. They are usually the products of various technologies including fluid mechanics and aerodynamics, structural engineering, avionics, materials science, propulsion and flight mechanics, with control playing a central role to enable flight capabilities. These technologies are collectively known as aerospace engineering.