An unmanned aerial system (UAS) includes a lighter-than-air (LTA) airship configured for autonomous long-duration flight; a hybrid propulsion system including at least one hydrogen fuel cell and at least one solar photovoltaic (PV) module disposed upon an outer surface of the LTA airship; an electrolyzer configured to generate hydrogen gas from water using power from the at least one solar PV module; a hydrogen storage system operatively connected to the at least one hydrogen fuel cell and the electrolyzer; and an autonomous resource management system configured to dynamically allocate power between the at least one hydrogen fuel cell, the at least one solar PV module, and the electrolyzer.