Conceptual design of the composite sandwich fuselage of a re-entry vehicle

CIRA, the Italian Aerospace Research Centre, is carrying out two projects among the others: one is focused on a feasibility study of a future re-entry spacecraft, USV-3; and the other is a technological project aimed at developing anisogrid lattice composite cold structures, ICCS. The two projects are linked since the benchmark structure for ICCS project is the structure of the fuselage of USV3, sharing the same requirements. The present paper is focused on the conceptual design of the USV-3 fuselage conceived in composite sandwich, used also as a benchmark for the ICCS project. The low level requirements of the structure have been obtained from launcher and mission high level requirements. Among all load types experienced by the vehicle during its mission, a first set of mechanical loads for conceptual design have been selected and evaluated. Analytical relations from literature have been used to choose materials, stacking sequence and core geometry against strength and typical core instability phenomena for the design of an equivalent cylindrical geometry made in sandwich composite. Then a simplified finite element model of the real cold structure shape has been set up, by using the same properties which came out from initial sizing of the cylindrical structure. Modal analyses have been carried out to verify natural frequencies compatibility with the launcher, with iterations on design. Once launcher compatibility was fulfilled, static strength and global buckling analyses have been carried out against launch and landing load factors showing a good behavior of the selected structural concepts for the fuselage cold structure.