Toward net-zero in space exploration: A review of technological and policy pathways for sustainable space activities

Space exploration's environmental impact presents a critical challenge to global net-zero objectives, particularly through launch emissions, orbital debris accumulation, and energy-intensive manufacturing processes. This narrative review examines technological and policy pathways toward sustainable space activities, analyzing emerging green propulsion systems, renewable energy integration, and circular economy applications in spacecraft design. The review evaluates the efficacy of current sustainability initiatives, including hydroxyl-free hydrazine propulsion, solar-electric systems, and advanced satellite technologies for environmental monitoring. Critical assessment of regulatory frameworks reveals gaps in international governance, highlighting the need for standardized carbon accounting and emissions trading schemes in space operations. The analysis extends to public-private research and development partnerships (PPRDPs), examining their role in accelerating sustainable innovation through information spillover effects and agglomeration externalities. While technological advancements demonstrate promise, particularly in reusable launch systems and space-based solar power (SBSP), significant challenges persist in deep-space mission sustainability, regulatory enforcement, and cost barriers to green technology adoption. This review synthesizes current progress and limitations in sustainable space exploration, providing insights for policymakers, industry stakeholders, and researchers working toward net-zero space operations. The findings emphasize the necessity of harmonizing space exploration objectives with environmental preservation through integrated technological innovation and international cooperation frameworks.