ESA GNC Conference Papers Repository

The Intermediate eXperimental Vehicle (IXV) program achieved a major success for Europe, when the IXV was launched on February the 11th, 2015, and returned to Earth with a flawless re-entry. IXV was an ESA re-entry lifting body demonstrator built to verify in-flight the performance of critical re-entry technologies. The IXV´s flight and recovery represents a major step forward with respect to previous European re-entry experience. In particular, the increased in-flight manoeuvrability achieved from the lifting body solution permitted the verification of technologies over a wider re-entry corridor. A key part of the IXV developments and advances was the IXV GNC. The IXV GNC represents a big step from previous European GNC solutions for re-entry vehicles. It provided a fully autonomous GNC subsystem that operated during the full sub-orbital flight from the Guiana launch-pad, a few minutes prior to Vega lift-off, to splashdown in the Pacific, through the entire set of flight phases; pre-liftoff, ascent, orbital, re-entry and descent. The IXV GNC included the guidance algorithm for the lifting body, the use of the IMU measurements with GPS updates for navigation, and the flight control by means of a combination aerodynamic flaps and reaction control thrusters. The Guidance algorithm was based on an improved formulation derived from the original Shuttle guidance, and decouples the trajectory control within the trajectory plan (longitudinal guidance) and the lateral control (lateral guidance). The longitudinal guidance is an evolved drag tracking algorithm. The Control algorithm included the combination of a model-based feed-forward strategy which accounted also for non-linear dynamic inversion components, combined with a robust multiple-input-multiple output feedback control law, and a light thruster management function. The DRS algorithm included multiple-criteria thresholds for parachute deployment that guaranteed deployment under multiple nominal and off-nominal scenarios. This paper provides an overview of the performance of the IXV GNC during the atmospheric entry phase, focusing in detail on the Re-entry Guidance, the Re-entry Control and the DRS algorithms. The analysis concentrates on the comparison of the flight performance, relative to the pre-flight predicted performance from Phase E of the project, using the IXV-FES in SIL configuration and, also, relative to post-flight updated simulated recreation of the flight using an updated configuration of the IXV-FES, including the basic flight parameters (e.g. Vega injection performance). The paper includes a discussion on the main similarities and differences among these results. This allows to conclude on the overall effectiveness of the Re-entry GNC of IXV, and in particular the design solution chosen for the Re-entry Guidance, the Re-entry Control and the DRS algorithms for IXV, with implications on future European re-entry GNC activities.