HYFLEX (Hypersonic Flight Experiment) is performed for the purpose of accumulation of designing, constructing and operating technology of a vehicle flying at hypersonic speed like a plane and acquisition of various data which are difficult to obtain by ground tests.
The surface of the vehicle is covered with carbon/carbon, ceramic tiles, and flexible insulator, which are planned to be used on the HOPE. The navigation of the vehicle employs IMU and the attitude control is to be performed by using combination of RCS and elevons. The vehicle is equipped with temperature and pressure sensors, and refectometers.
HYFLEX vehicle was launched by J-I launch vehicle in February 1996. It collected several useful data in flight and splashed down in the ocean. But it was unsuccessfully recovered.