Flight control system for the automatic landing flight experiment

This paper discusses the flight control system developed for the Automatic Landing FLight Experiment, ALFLEX. ALFLEX is an experimental program conducted by the National Aerospace Laboratory and the National Space Development Agency of Japan in order to investigate the automatic landing technology for a future unmanned reentry space vehicle. The ALFLEX vehicle is a dynamically similar sub-scale model of the planned Japanese HII Orbiting Plane, HOPE. Since the HOPE program is in a preliminary conceptual design phase, the ALFLEX vehicle is a scaled model of one of the proposed configurations from 1992 research. The vehicle bare airframe is statically unstable in the pitch axis. In the lateral-directional axes, it has negative weather cock stability and strong dihedral effect, which introduce severe instability. The airframe's instability and the landing performance requirement drive the flight control system design to be one of the key technologies in the HOPE program. Since the vehicle's maximum L/D is approximately 4, it needs the same landing guidance technique as lifting body research vehicles and the Space Shuttle. This paper discusses the flight control design and the design methods applied to ALFLEX, and discusses lessons learned so far. The results from a preliminary flight test are briefly introduced. The series of automatic landing flights are scheduled for the middle of 1996, at Woomera, Australia, and will verify the guidance, navigation and control design.