Multi-bubble scheme and structural analysis of a hypersonic stratospheric flight vehicle

Abstract

The STRATOFLY MR3 vehicle is the main objective of the STRATOFLY project, which aims to develop a hypersonic air breathing concept capable of covering antipodal routes in less than three hours. The aircraft architecture features a waverider configuration, internally supported by multi-bubble integral cryogenic tanks hosting LH2 propellant, being one of the major challenges the integration of lightweight structures with the high-speed propulsion system. The objective of this research is to completely define an efficient structural scheme of the multi-bubble structures. To do so, a multidisciplinary analysis of the full-scale aircraft model is carried out to assess the viability of the vehicle prototype. Once the flaws of the initial structural layout are identified, a set of stiffener elements were developed to generate a scheme which can withstand the loads that hypersonic flight entails. In the multi-bubble structures, a topology optimization strategy was applied to obtain a set of tension rods connecting the top and bottom parts of the bubbles to support the pressure loads. The proposed configuration was sized and analyzed for multiple points of the aircraft mission, obtaining stress levels below the failure criteria adopted for each material. In addition, the results show low displacements that guarantee an adequate aerodynamic behavior and engine performance, while mantaining global natural frequencies in the range of commercial airplanes.