Functional and thermal 1D modeling of a reusable LH2-tank using EcosimPro/ESPSS and comparison to CFD results

The CALLISTO reusable vertical take-off and vertical landing prototype vehicle (VTVL) is a joint project between CNES, DLR and JAXA. In order to analyze the operational processes and thermal behavior at a system level within the scope of the liquid hydrogen tank of the CALLISTO vehicle, a 1D thermal and hydraulic model of the LH2 tank has been developed which is taking the thermal environment of the mission into account. The model features the capability to simulate the entire mission from initial tank chill down, propellant loading, boil-off venting and pressurization to postflight residual propellant venting. This way the required propellant mass, boil-off rates and heat fluxes to the structure can be evaluated and their impact on the overall mission can be analyzed. In order to correlate the effect of external forces on propellant sloshing but also to predict the pressurant budget and thermal residuals, data from dedicated CFD simulations has been used. The combination of multiple tools enables a more detailed understanding of all effects that have an impact on thermal and hydraulic behavior of the LH2 tank system during the mission. This paper compares both approaches, shows the advantages each has and their limits