Architecture study for in-orbit long term cryogenic storage to support space exploration

The space community is currently focusing on defining mission architectures able to perform multiple interplanetary missions to support deep space exploration. In particular, placing orbital propellant depots in strategic locations in space would allow to increase the useful mass transferred. The design of the propellant depot depends greatly on the propellant storage duration and the thermal environment the depot experiences. Furthermore, different cryogenic propellant combinations are being considered for use, including hydrolox and methalox. For both, efficient boil-off reduction strategies are fundamental. The aim of this work is to evaluate different depot architectures for different thermal environments and mission durations. The approach taken in this work included the development of a propellant depot sizing model that allows determining the effect of different thermal control design options, thermal environments, and depot configurations for varying mission duration. The design options include, amongst others, Multi-Layer Insulation and Vapor Cooled Shields. The model also allows for a multi-nodal thermal analysis to estimate boil-off rates for the different designs. Main objective for the studies is to identify the architecture that is most mass efficient. Preliminary results show that mass efficient designs can be achieved with only passive insulation for mission durations below one year, with further improvements when adding a vapor cooled shield to the design.