Non-Terrestrial Networks for Space Vehicles beyond 6G: Applications, Architecture, and Capacity Limits

In this work, we present a comprehensive study of using Non-Terrestrial Networks (NTNs) with sub-terahertz (sub-THz) connectivity to serve space users, offering a novel perspective on expanding NTN applications beyond terrestrial communications. For the first time, we provide a detailed analysis of the advantages and challenges of this approach, supported by in-depth numerical simulations. Our results demonstrate that NTNs significantly enhance connectivity robustness for space users compared to ground station (GS)-based systems. By leveraging state-of-the-art sub-THz technology, our study reveals performance improvements of nearly two orders of magnitude in downlink capacity over conventional Ku-band GS systems. We further highlight the potential scalability and energy efficiency of NTNs for serving low Earth orbit (LEO) satellites and beyond. The results underscore the transformative potential of integrating NTN systems into the broader space communication ecosystem, paving the way for seamless, high-capacity connectivity for scientific, commercial, and exploration missions.