The course illustrates the fundamental aspects of modern space system design with a practical, hands-on approach. The core part of the course is dedicated to a near-Earth or interplanetary space mission design project, to be carried out by student teams on the basis of a broad-scope mission definition statement. Starting with the identification of the mission requirements derived from a critical analysis of the high-level mission goals, the main design choices and the main criteria involved in the design the various elements of the mission are reviewed, including specialized orbits, space vehicle architecture, ground segment and launch systems. The main issues involved in the design of a space mission are addressed: from the definition of mission goals, to the evaluation of alternative mission concepts, to the selection of a launch system, to mission operations. Team work aspects for a concurrent engineering approach and presentation techniques for complex projects are also introduced and discussed. Special attention is given to the specific design issues of small spacecraft missions and to modern low-thrust trajectory design. Projects deal with assessment of the technical feasibility and economic viability of different mission scenarios; selection of mission profile and timeline; design of orbits and trajectories; launch and in-orbit operations; sizing of the main onboard subsystems (attitude, power, thermal conditioning, propulsion, telecommunications, sensors, etc.) for the relevant space vehicles; and basic project management.