The Conceptual Structural Design of an Unmanned Space Vehicle with Re-entry and Landing Capabilities

CIRA, the Italian Aerospace Research Centre, in the framework of the national space program has carried out a feasibility study of a future re-entry spacecraft concept with automatic re-entry and landing operational capabilities, code named USV-3. Such a vehicle will be injected in a LEO orbit (i.e. 300km) by the VEGA launcher to execute few revolutions around the Earth and then it will perform an automatic re-entry flight. After deboosting by the VEGA AVUM upper stage, the vehicle will execute an autonomous flight from hypersonic to subsonic regime allowing terminal area energy maneuvers, approach and landing on a conventional runway. The present paper describes, after a general overview of the mission and vehicle requirements, outcomes from the feasibility study concerning the structural design of wing and fuselage cold structures. The aim of the work is to assess the feasibility of the whole USV-3 cold aero-structure by evaluating different structural concepts for wings and fuselage according to requirements of maximum overall dimensions, weight and technological constraints. As regards the wing, a certain number of feasible structural architectures have been analyzed in order to identify the solution that better fulfills requirements of maximum overall dimensions, weight, and quality indexes such as stiffness, feasibility and cost of fuselage-wing joints. The best solution shows consistent structural stresses and absence of structural instabilities at a given number of preliminary load conditions. The fuselage has been conceived to fulfill dynamic constraints from the launcher side, and to withstand structural loads occurring at each mission phase. It is made of advanced composite materials able to maintain sufficient mechanical properties up to 160°C. A comparison with an aluminum alloy fuselage cold structure has also been done by respecting the dynamic requirement imposed by the launcher manual. The results show that an aluminum structure weights more than 2.4 times with respect to the CFRP fuselage structure. Moreover aluminum performance at high temperature show no convenience in the use of AA instead of CFRP. The conceptual design of the cold structure also includes a first idea and a basic sizing of the wing-fuselage junctions. All studies presented herein are of a conceptual nature, i.e. to be improved in the future design phases by increasing the detail level and at the same time by investigating also the behavior of these solutions with the respect to thermal and manufacturing process requirements.