In this article, an on-line guidance strategy for terminal area energy management phase of a re-entry flight is proposed. In order to fulfil the objectives of this flight phase, the algorithm continuously performs long- and short-term on-line trajectory generation, also accounting for the most relevant vehicle and trajectory constraints. Long-term guidance computes a reference trajectory which minimizes the distance from the final target. Short-term guidance generates the control commands by computing a trajectory that minimizes the displacement from the reference one, thus compensating for the errors due to the environmental disturbances and to the uncertainties of the vehicle model. In the proposed guidance strategy, the main vehicle performance constraints are appropriately accounted for, thus guaranteeing adaptivity in the failure situations where the manoeuvring capabilities are reduced. The proposed guidance strategy has been developed in the framework of the unmanned space vehicle program of the Italian Aerospace Research Centre for the execution of Dropped Transonic Flight Test second mission. In this article, the algorithm performances and robustness to the vehicle initial state have been assessed through a preliminary Monte Carlo analysis. Furthermore, several simulations with bank angle and angle of attack limitations have shown the effectiveness of the algorithm in the presence of reduced manoeuvring capabilities.

No abstract

No abstract

No abstract

The study of a novel navigation system for Unmanned Airborne System (UAS) based on bistatic Synthetic Aperture Radar (SAR) is presented. The innovative bistatic configuration builds on spaceborne radar transmitters and airborne receivers, the latter mounted in a forward-looking geometry. Such approach, impossible or extremely demanding with a monostatic approach, allows one to achieve dual information with two different radar working modes: imaging capability can be in fact coupled with the possibility of moving target indication. The study is particularly suited on one of the most common UAS platforms: a close range, medium takeoff weight, with an endurance of roughly 7 hours and cruise speed of about 50m/s, whose requirements have been identified. The finalization of the study is achieved by the definition of a strawman system concept with different approaches. Four options are identified, with different performance and system complications/challenges. The study herein reported was carried out under ESA contract 22449/09/F/MOS.