Design of an On-board Flight Safety System for Space Microlaunch Vehicles
Creators: name: POU, C.
name: VALLVERDU, D.
name: DIEZ, E.
Publisher: name: Proceedings of the 8th European Conference for Aeronautics and Space Sciences. Madrid, Spain, 1-4 july 2019
Year: 2019
Subjects: AEROSPACE SYSTEMS
EMBARKED SOFTWARE

description: The growth of the microlaunch market is breaking the relationship paradigm between a spaceport and launch services operated by a single organization. Microlaunch services initiatives are planning to launch from more than one spaceport to reach the necessary launch rate to succeed in their business plan goals. Simultaneously, spaceports are preparing themselves to be able to provide base services to multiple launch concepts (vertical, horizontal, reusable, airborne...) operated by different private organizations. In such scenario, standard and modular systems, which contribute to cost-effectiveness, responsiveness and flexibility of the launch campaigns, are becoming essential for both microlaunch service providers and spaceports to achieve launch rate and cost fitting the payload market. The on-board flight safety system (OBFS) of the launcher avionics provides the embedded real-time safety algorithms with a single standard interface with ground stations devoted to mission tracking. Considering the OBFS to be a tested and validated standard equipment, its integration in the launcher allows for the optimization of ground operations and infrastructures, radar stations in particular, by first reducing the pre-flight phase dedicated to mission configuration, equipment preparation and safety operators training; and secondly providing autonomous real-time operations devoted to the processing of tracking means and safety decision making. The present work is in the frame of the ALTAIR H2020 project, devoted to the design of an airborne launch service concept. This paper is focused on the architecture and algorithms of the OBFS on-board the ALTAIR avionics. The architecture is based on two major components: the navigation module, based on GNSS-IMU hybridization, and the safety assessment module. The objective is to validate the performance (reliability, precision and availability) of the safety module serviced by a light-weight and cost-effective navigation system in the critical operational scenarios identified for an airborne concept: the carrier manoeuvre to initialise the launcher navigation system, the release consent procedure, the ignition consent after release and the ascend flight timeline. The critical algorithms covering the abovementioned functions are in the frame of state estimation, filtering and propagation. Two main algorithms are implemented and tested: the impact area of a ballistic fall based on the FG Series concept for state uncertainty propagation and the attitude propagation of the rocket free flight, based on Runge-Kutta propagation of attitude and attitude rate state. The impact area algorithm provides safety criteria for the release consent and the nominal ascent flight considering the safety of people and goods in case of launcher failure leading to a neutralisation or uncontrolled descent trajectory. The attitude propagation provides safety decision making for ignition consent procedure in degraded release scenarios. The OBFS architecture is tested in nominal and degraded mission scenarios with two objectives: the characterization of the system operational frame limits through a sensitivity analysis and the validation of safety outputs with respect to operational safety standards. The results of the present study contribute to the airborne system definition loop (alignment manoeuvre, release system, launcher aerodynamics) and provide real-time safety operations scenario awareness.