Economic and environmental sustainability of liquid hydrogen fuel for hypersonic transportation systems

Based on recent research activities, the cost of the propellant may represent up to the 90% of the Direct Operating Cost for a hypersonic vehicle. Therefore, it can be considered the most relevant cost item of the overall Life Cycle Cost. In this context, the paper focuses on the estimation of the cost of liquid hydrogen, one of the most promising fuels for high-speed applications, considering its specific energy content. In particular, a methodology is here presented to guide engineers through the evaluation of the impact of the LH2 price on Direct Operating Cost and then onto the overall Life Cycle Cost for a long-haul point-to-point transportation system. Starting from an overview of the current H2 productive scenarios, future possible technological improvements allowing an increment of the production rate and a reduction of the related socio-economic impact are described. Then, a detailed cost-estimation model is presented for the so-called “green” hydrogen. Eventually, the developed cost model is applied to the LAPCAT A2 and LAPCAT MR2.4 vehicles and mission concepts, demonstrating that in a future scenario (2050) the LH2 cost can be lowered down to 2 €/kg. With this fuel price, the share of fuel cost onto Direct Operating Cost can be reduced down to 70%.