Small Unmanned Aerial Systems (UASs) have great potential for many different applications [1- 5]. The small UASs are lightweight, man-portable, and capable of carrying payloads. For military applications, these systems provide valuable intelligence, surveillance, reconnaissance, and target acquisition (ISRTA) capabilities for units at the infantry battalion, company, and platoon levels. The power system is a key component for small UASs to perform extended and long-range missions. We have selected, examined, developed, and evaluated several cutting-edge power and energy technologies to power small UASs. Currently, the capabilities of a small UAS are limited by its power source. Small UASs are mainly powered by advanced batteries, which cannot sustain extended operations. Small engine generators are not a viable solution because they generate pollutants and can be noisy, which could be detected by the adversary. Solar cells are not efficient enough to be used as the primary power system and are limited by weather conditions. Polymer Electrolyte Membrane Fuel Cells (PEMFCs) still have the same technical constraint, the source of hydrogen, as they did many years ago. The objective of this work is to develop, demonstrate, and integrate a highly efficient, lightweight 350 W Solid Oxide Fuel Cell (SOFC) system for small UAS applications. The result of this developmental effort will be a power system to support increased mission duration, power, and reliability of the small UAS, resulting in improved situational awareness. Improved situational awareness capabilities will specifically benefit Department of Defense convoys, route clearance missions, base/defense patrols, and other reconnaissance objectives. The research and development efforts presented here not only apply to small UASs but can also help extend mission operations for unmanned ground vehicle systems and Soldier-portable power application.