本文將運用最佳化理論，探討太陽能無人飛行載具之最佳飛行軌跡。不同於以往 之大多數的最佳飛行軌跡研究通常多針對燃油消耗率進行設計，本文的研究則是 著重於能量消耗率對於飛行軌跡的影響，期以配合太陽能無人飛行載具研發之應 用。研究顯示在最佳的爬升軌跡下，飛機的升力係數與指示空速均保持定值；在 給定的發動機輸出功率之下，固定高度之最佳轉彎飛行時，載具之控制參數(滾 轉角)僅與速度有關。此二者之結果有助於太陽能飛機維持最佳爬升以及最佳水 平轉彎軌跡的導引應用。 The optimal trajectories of solar powered Uninhabitant Aerial Vehicle (UAV) flying in atmosphere are studied. The solar powered UAV will not expel the fuel during the flight. Therefore its mass keeps constant during the flight. The energy loss does not affect the motion of the vehicle explicitly. In the study the energy expense is the cost function. The standard procedure of finding optimal trajectory which cooperate the Pontryagin theory is applied. The study shows that during the optimal climbing, the vehicle keeps the constant lift coefficient and the indicated airspeed. And during the optimal turn at constant altitude for given power, the control variable (bank angle) is a function of velocity only. Those two results make the design of guidance law easier.