Sustainability Assessment of Liquid Hydrogen Aircraft Tanks

Using liquid hydrogen (LH₂) in aviation creates a difficult design problem for cryogenic storage systems, especially in the early design stage. At that point, environmental, economic, and technical aspects need to be considered together. Here, a sustainability assessment framework is presented for LH₂ aircraft storage tank configurations from a life-cycle perspective. The study includes 24 design alternatives. These are obtained by changing the material combinations of the main structural components, while the overall tank architecture is kept unchanged. The environmental and economic dimensions are assessed through Life Cycle Assessment (LCA) and Life Cycle Costing (LCC), whereas the technical dimension is represented by system mass. Since the relative importance of the criteria is usually not fixed at this stage, Unweighted TOPSIS (UW-TOPSIS) is first used to examine the alternatives under different weighting scenarios. The most competitive solutions are then re-evaluated by a standardised TOPSIS variant (vector-normalised weights, Z-standardised distances) with objective weighting methods. The results show that the configurations based entirely on Al2219-T8 for the main structural components remain top-ranked and more stable under the examined scenarios, whereas mixed-material configurations are more sensitive to changes in weighting assumptions. In this way, the exploratory stage is kept separate from the later weighting stage, where the weights are computed from the decision matrix of the reduced set. This is suitable for early aerospace design, where subjective preferences are often not yet available.