ESA GNC Conference Papers Repository
IXV GNC Subsystem Design and Performances
This paper presents the overall design constraint, architecture and performances achieved by the Guidance, Navigation and Control (GNC) subsystem of the Intermediate eXperimental Vehicle (IXV). The IXV is an European re-entry demonstrator built to verify in-flight the performance of critical re-entry technologies. Among such critical technologies of interest, special attention is paid to GNC aspects including the guidance algorithms, the use of the inertial measurement unit coupled with GPS for navigation, and the flight control by means of aerodynamic flaps and reaction control thrusters. The IXV will be injected by the VEGA launcher into an equatorial suborbital trajectory. After the injection, three main phases are distinguished for the IXV vehicle: the Orbital phase, the Re-entry phase and the Descent phase. The Flight Control Function of the IXV is based on four 400N thrusters and two aerodynamic flaps located at the base of the vehicle. Thrusters are used to control the attitude around the three axes during the orbital phase and the yaw during the atmospheric re-entry whereas Flaps are used to trim and control the vehicle on the longitudinal (symmetrical deflections) and lateral (unsymmetrical deflections) axes. Vehicle position and velocity are estimated by the Navigation function based on IMU measurements (i.e. velocity or acceleration and attitude estimations) improved with GPS PVt updates and Drag Derived Altitude (DDA) pseudo-measurements during the blackout. The Guidance function is responsible for keeping the vehicle on track during the flight to reach the desired location for parachute triggering. It gets the actual vehicle location from the Navigation function and provides the reference attitude to the Control. The overall coordination of the Guidance, Navigation and Control functions is implemented by the Flight Management function which handles both higher levels communication with the system Mission Vehicle Management function and with the lower levels consistency with each GNC unitary function. Additionally, the vehicle is equipped with a descent and recovery system (DRS) composed by a set of parachutes, flotation and localization devices. The descent phase starts with the first parachute supersonic opening. During this phase IXV is in open loop mode (no guidance and control), although navigation still provides estimates of the vehicles dynamic state and detection of the splashdown event. This paper will also focus on presenting the GNC detailed design currently under CDR and reporting on the overall system performance validation. Finally an overview of GNC subsystem qualification approach will be illustrated.