CNES, the French Space Agency, has been leading for nearly six years intensive research on alternative green propellants for spacecrafts thrusters. More precisely, research has been focused on premixed monopropellant formulations based on state-of-the-art energetic materials and green chemistry approaches. The goal of this program is to provide an innovative propulsion system to replace standard hydrazine technology, demonstrating total breaking performance, low toxicity and high versatility. Hydrazine, mostly used in its anhydrous form as catalyzed monopropellant, is indeed an old and undoubtedly flight-proven product, but suffers from relatively poor propelling performance and from a high toxicity (both acute and suspected CMR). This paper describes the origins of the project and the main requirements we have imposed on ourselves. It also gives an overview of both the organization and the roadmap of the development plan, then concluding on the achievements and breakthroughs obtained to date.