Aeronautical engineering degrees represent the branch of engineering that deals with the research, design, development, construction, testing, science and technology of aircraft. A division of aerospace engineering, aeronautical engineering focuses on applying physics, mathematics and other disciplines in order to construct aircraft. Aeronautical engineers work to make sure propulsion systems operate efficiently and that aircraft's aerodynamic performance is sufficient. Aspiring aeronautical engineers should get their bachelor's degree in aeronautical or aerospace engineering, though some related majors may be sufficient. Aeronautical engineering was the original term for the field, but as flight technology advanced to include craft operating inouter space, the broader term "aerospace engineering" has largely replaced it in common usage. Aerospace engineering, particularly the astronautics branch, is often referred to as "rocket science.