The purpose of this Thesis is to develop the design process of the pressurised propellant tank for a water resistojet, applicable to nanosatellite missions. The motivation of this system is its use on the CubeSat mission DelFFi, from the Technical University of Delft. The need for a small-sized pressure vessel is covered by the Detail Design delivered in this Thesis, which is a result of the application of decision making techniques as well as a structural analysis. It is possible to distinguish two ?elds of investigation throughout the work: design and structures. The design of the propellant tank is tackled following the Design Trades: a systems engineering approach which makes use of decision making, a trade-off process and uncertainty analysis. By applying a 10-step methodology, a set of conceptual designs is developed and further re?ned into a preliminary design. As far as the structural analysis is concerned, both an analytical study and a Finite Element Analysis are completed. The former is mainly used for veri?cation and validation of the latter. The result is a Detail Design, ready for manufactureandtesting. As a result, a design compliant with the requirements is delivered, together with CAD and Finite Element models. This design involves a rectangular section pressurised tank, compatible with CubeSat structures, manufactured from aluminium via CNC milling. The conclusion is a successful application of the methodologies, a complex design and guidelines with expected correct performance and a know how on pressurised propellant tank design and analysis.