Overview of Flight Guidance, Navigation, and Control for the DLR Reusability Flight Experiment (ReFEx)

Abstract

This paper gives an overview of the proposed GNC architecture for DLR's Reusability Flight Experiment (ReFEx), which is split into two main subsystems: The Guidance and Control (G&C) subsystem, which determines the desired trajectory from the current flight state to a designated target and issues the necessary commands to the actuators (canards and rudder, as well as a reaction control system for flight phases outside the atmosphere) by calculating the necessary forces and torques based on the required changes of velocity and attitude for following this trajectory; the Hybrid Navigation System (HNS), which is responsible for estimating position, velocity, attitude, angular rates, and other parameters of the flight state. It does so by real-time fusion of measurements of inertial sensors (accelerometers and gyroscopes) with the measurements of GNSS receivers, Sun sensors, laser and radar altimeters. The requirements and boundary conditions set by the mission, the current design baseline for both subsystems, the stability analyses for flight control, the basic guidance strategy chosen as well as the navigation performance assessment through covariance analysis are described and discussed.