Development of ground taxiing control law for automatic landing fight experiment(ALFLEX)

This paper discusses the development of a ground taxiing control law for Automatic Landing Flight Experiment, ALFLEX and introduces results from ground taxiing tests and flight tests. ALFLEX project is an experiment program conducted by National Aerospace Laboratory of Japan and 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 dynamically similar sub-scale model of the planned Japanese H2 Orbiting Plane, HOPE. The automatic landing flight experiment program was conducted, and a series of tests were carried out successfully, at the Woomera Airfield, Australia in 1996. Before its first flight, some ground taxiing tests were conducted to determine vehicle characteristics in ground taxiing conditions. Ground taxiing tests were conducted under four conditions; the initial velocities 8.3, 13.8,19.4, and 25m/s. The steering characteristics derived from ground taxiing tests were different from those of a design model. But from the results of linear and non-linear analyses based on ground test results, it turned out that the ground-taxiing controller could keep the vehicle in a runway from touch down speed to zero speed with no modification. All flight test results supported that conclusion. This paper describes details of the ground taxiing controller, and the results of ground taxiing tests and flight tests.