Design optimization of multi-functional multi-lobe cryogenic fuel tank structures for hypersonic vehicles

Hypersonic hydrogen-powered cruise vehicles offer promise for economical and reliable high-speed atmospheric transport. In recent years, several vehicle concepts have been developed in which the integration of fuel tanks is a major challenge, as they feature complex aerodynamic designs. In this work, we explore the viability of multi-lobe hydrogen tanks as a solution to obtain lightweight and volume-efficient structures. To do so, a parametric finite-element model was developed to fit multi-lobe geometries inside hypersonic vehicles. The parametric model was then incorporated into an optimization that minimizes the mass and maximizes the fuel capacity of the tank. The methodology is organized in two steps: the global search is driven by a two-level optimization consisting of a genetic algorithm with a nested gradient-based method; and a local search where each design is further improved to obtain a Pareto front. As presented in the results, this is a promising approach for designing multi-lobe tanks for complex geometries.