NACA High-Speed Flight Station test pilot Stan Butchart flying the Iron Cross, the mechanical reaction control simulator. High-pressure nitrogen gas expanded selectively, by the pilot, through the small reaction control thrusters maneuvered the Iron Cross through the three axes. The exhaust plume can be seen from the aft thruster. The tanks containing the gas can be seen on the cart at the base of the pivot point of the Iron Cross.NACA technicians built the iron-frame simulator, which matched the inertia ratios of the Bell X-1B airplane, installing six jet nozzles to control the movement about the three axes of pitch, roll, and yaw.