An Investigation of Phased Mission Reliability Analysis for Tethered HAP Systems

High-altitude platforms (HAPs), are becoming a viable option for long-term and cost-effective tasks like environmental monitoring, surveillance, and telecommunications. Tethered HAPs provide better stability, power supply, and data transmission capabilities because they are physically tethered to the ground. Addressing the reliability of a tethered HAP system as a phased mission system (PMS) is crucial due to the integration of many phases, such as launch station-keeping, and descent. Each phase presents unique performance requirements and environmental challenges. Ensuring reliability at every stage is essential for the success of the mission and the safety of operations over the entire lifespan of the system. This article addresses the feasibility and necessity of conducting a reliability analysis of tethered HAP systems, specifically considering them as PMSs with distinct operational stages. A comprehensive reliability analysis has been carried out for every single phase by considering the risks and challenges connected to each phase. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.