THE SUB-ORBITAL RE-ENTRY TEST OF THE CIRA'S USV PROGRAM: PHASE A TRAJECTORY OPTIMIZATION AND CONTROL U.Tancredi ∆ , L.Verde † , E.Filippone ‡ ∆ Seconda Università di Napoli - Via Roma 29 81031, Aversa (CE), urbano.tancredi@unina2.it † CIRA, Flight Systems Laboratory - Via Maiorise , 81043 Capua(CE), l.verde@cira.it ‡ CIRA, Flight Systems Laboratory - Via Maiorise , 81043 Capua(CE), e.filippone@cira.it ABSTRACT This work deals with the problem of identifying and controlling the trajectory of a small winged vehicle performing an aero-assisted re-entry maneuver from sub-orbital conditions. The vehicle considered is the Unmanned Space Vehicle (USV), currently under development at the Italian Aerospace Research Center (CIRA). The unusual mission objective of maximizing thermal stress on the vehicle’s structure required particular attention in the Flight Mechanics problem statement and solution. Furthermore, the analysis conduced provided the maximum attainable performance of the mission objective, and also an estimate on the minimum performances requested to the command and actuation system. Finally, evaluation of the augmented vehicle performances has been performed by means of numerical simulation under nominal and perturbed conditions, including atmospheric disturbances. INTRODUCTION In the last decades, spacecraft mass and requirements have been strongly reduced in order to limit costs, risks and development time, leading to the better-faster- cheaper trend, that has one of its better expressions in microsatellites. Thanks to cost reduction, microsatellites can allow frequent re-flight, opening new opportunities for small, cost-effective, re-usable launch vehicles, that seem to be their natural completion in the launch vehicle sector. In this frame the Unmanned Space Vehicle (USV) Program is actually being performed by the Italian Aerospace Research Center (CIRA). USV Program focuses on the technologies involved in the development of an autonomous, fully re-usable winged launch vehicle, planning for this purpose five flight test. The focus of this paper will be on the Sub-Orbital Re- entry Test (SRT); specifically, this paper deals with SRT's longitudinal flight plane re-entry trajectory optimization and control. Main objectives are to perform flight mechanics feasibility analysis, provide the maximum attainable performance of the mission objective, and also an estimate on the minimum performances requested to the command and actuation system, in terms of actuator's speed and command maximum amplitude. MISSION’S DESCRIPTION AND OBJECTIVES In the Sub-Orbital Re-entry Test (SRT) all the technologies linked with the re-entry of an autonomous winged vehicle are approached. SRT's main objective is to reproduce thermal stress conditions as high as those typically encountered in an orbital reentry maneuver, specifically on advanced TPS materials samples inserted in vehicle's surface. As depicted in Figure 1, in this test the height of 35 Km will be gained by the use of an aerostatic balloon, subsequently the vehicle, propelled by a solid state motor, will reach the maximum height of 120 Km from whom it will start the re-entry maneuver, reaching high thermal flux values (> 650 W/m 2 ) for the maximum attainable time. The mission ends with a parachute deploy, and a successive recovery from sea. The flight test bed configuration is shown in Figure 2 and summarized in Table 1. The performed analysis has focused only on the longitudinal flight plane motions, controlled by means of elevators symmetric deflection δ e , wherever the dynamic pressure is significant to perform an aerodynamically based control, otherwise through the action of cold gas thrusters T RCS . Figure 1- Sub-orbital Reentry Test Mission Profile