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

Abstract

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.

Analysis of aerodynamic loading on a rocket and design

“…As the launch vehicle was expendable, minimising the costs was paramount to a successful design.  By adding lithium to the aluminium, the specific strength and stiffness can be significantly increased (Boyer et al, 2015)  Not as strong at titanium or steel and susceptible to high temperature softening (Akin, 2014) (Wijker, 2008)  Al-Li alloys have low transverse toughness and are anisotropic (Boyer et al, 2015)  Monocoque and stiffened skins, pressure vessels, cryogenic fuel tanks, struts and primary structures (Wijker, 2008)  High strength interstages (Dunn, 2016)  2014 (Henson & Jones, 2017)  2219 (Boyer et al, 2015)  2024 (Belardo et al, 2015)  Al-Li (e.g. 2195) (Boyer et al, 2015)  7XXX series (Henson & Jones, 2017) Low Titanium  High strength, moderate density and low thermal conductivity (Boyer et al, 2015)  High strength at high temperature and stiffer than aluminium (Boyer et al, 2015)  Difficult to manufacture, costs more than aluminium (Boyer et al, 2015)  Poor ductility and can crack during welding (Wijker, 2008)  Composite parts attachment points (Boyer et al, 2015;Farley, 2013)  Thermal isolation (Farley, 2013)  Fuel tanks, pressure vessels and cryogenic structures (Henson & Jones, 2017;Wijker, 2008)  Truss structures (Hörschgen et al, 2006;Wijker, 2008)  Ti6Al4V (Boyer et al, 2015) Very High  Rods, trusses, pipes and LH2 tanks (Henson & Jones, 2017;Wijker, 2008)  N/A Very High Sandwich Panels  Increased moment of inertia and bending stiffness without a large increase in mass (Wijker, 2008)  High specific stiffness, good fatigue properties, good sound attenuation and thermal insulation and high impact absorption (Terhes, 2014;Wijker, 2008)  Complex failure modes due to the potential for debonding of face sheets and core (Wijker, 2008)  Instrument panels and mounts (Wijker, 2008)  Primary fuselage of the space shuttle …”