The X-43 is an experimental unmanned aircraft developed by NASA as part of the Hyper-X program. It is designed to test technologies for hypersonic flight, which refers to speeds greater than five times the speed of sound. The X-43 achieved a record speed of Mach 9.6 during its flight tests, demonstrating the potential for advanced propulsion systems. This aircraft uses a scramjet engine, which operates efficiently at hypersonic speeds. The X-43's successful flights contribute to research in areas such as aerospace engineering and future space travel, paving the way for faster and more efficient air and space vehicles.