NASA engineers used an F/A-18 aircraft to simulate a rocket in its early flight phase to test adaptive software for NASA's Space Launch System (SLS), the largest, most powerful launch vehicle for deep space missions.

NASA's F/A-18A aircraft validated the effectiveness of the Adaptive Augmenting Controller developed for the Space Launch System. (NASA/Carla Thomas)

Large rockets like the SLS have complex computers and software that swivel the rocket engines to steer the vehicle along its flight path. NASA's new software algorithm will make real-time adjustments as the vehicle pushes toward space, helping improve performance and enhancing crew safety in the particularly stressful parts of the flight.

One of first project tasks for engineers at NASA Armstrong was the development of a mission trajectory that an aircraft could fly that would simulate the SLS launch. Other responsibilities were the implementation of the software on the F/A-18 and mission planning. Part of that mission plan called for the pilot to engage the adaptive controller to mitigate the simulated effects of extreme scenarios, like bending instability during the simulated rocket trajectory.

In one of the tests, the F/A-18 flew a sequence of test points that maximized the bending excitation of the actual airplane based on data collected from earlier flights and prior structural tests. The bending response was isolated and the key features were reproduced in simulation, allowing the control variables to be modified accordingly to induce a real structural instability that the adaptive controller would have to mitigate.

Subsequent tests used that data to intentionally place the airplane in structural resonance, which causes the aircraft to vibrate while in flight. The adaptive augmenting control system then responded to these vibrations, suppressing them when they were large, meeting one of the major objectives of the adaptive controller.