"The ELSA project has the goal of improving European capacity to independently manufacture commercial and scientific satellites by bringing a new actuator for attitude and orbit control systems to a higher level of maturity. This goal is in line with ESA’s technology strategy and long term plan. Support for initial development activities for this innovative actuator technology was provided within the framework of ESA’s GSTP program.The concept consists of a levitated sphere that can be accelerated about any axis producing a resultant torque in any direction. This system aims at replacing the three (or four) traditional reaction wheels or control moment gyroscopes commonly used in satellites and spacecrafts. It reduces the mass and power supply allocated to theattitude and navigation unit. The mass and power saved can be allocated to the payload. The concept offers performance gain; it provides more momentum for a given system mass in comparison with the current inertial subsystems. It improves the system reliability as no mechanical bearings are present and allows more flexible mission planning.This project, proposed for activity 9.2, ""Strengthening the foundations of Space science and technology"", topic SPA.2011.2.1-02, ""Research and development for space exploration"", comprises three phases.Phase 1 will define the system specifications, based on an extensive market study of potential user's requirements, and identify a reference mission that will provide requirements in term of attitude and navigation control.Phase 2 will comprise the system design, manufacturing and integration, including a feasibility study of the steps necessary to spatialize the design and increase its technology readiness level. Where possible some of the identified spatialization steps will be implemented as part of this project.The project will conclude with phase 3, which will include system tests and performance assessments to demonstrate the potential of the Reaction Sphere."