Estimating aerodynamic characteristics of automatic landing flight experiment vehicle using flight data

The Automatic Landing Flight Experiment (ALFLEX) project was conducted as part of the research on the H-II orbiting plane-experimental (HOPE-X) unmanned reentry vehicle. One of the aims of the ALFLEX was to estimate the low-speed aerodynamic characteristics of a delta-winged vehicle with wingtip fins and experiments for this purpose, such as α/β sweep and control surface excitation, were conducted during hanging (suspended from a mother ship) and automatic landing test flights. When flight test data are analyzed, the aerodynamic characteristics of the ALFLEX vehicle are estimated and the results are compared with those predicted by wind-tunnel tests. Flight results show that estimated characteristics are similar to the predictions except for a few characteristics. Although the results from the hanging flight tests exhibit scattering that is due to measurement errors caused by the effects of an umbilical cable, the hanging test method will be useful if this problem is solved by means such as using an internal battery to supply power to the vehicle instead of the umbilical cable.