Pressure Vessel Mass Estimation for High Altitude PEM Unmanned Aircraft System

Abstract

The power to weight ratio of the power plant is an important consideration, especially in design of Unmanned Aircraft System (UAS). In this paper, a UAS with an MTOW of 35.3 kg, equipped with a fuel cell as a prime power supply to provide electrical power to the propulsion system is being considered. A pressure vessel design is proposed that can estimate and determine the total size and weight of the combined power-plant of a fuel cell stack with hydrogen and air/oxygen vessels and the propulsion system of the UAS for high altitude operation. Two scenarios are adopted in determining the size and weight of pressure vessels required to supply oxygen to the fuel cell stack. Different types of stainless-steel materials are used in the design of the pressure vessel in order to find an appropriate material that provides low size and weight advantages. Also, hydrogen pressure vessel design and mass estimation are also considered. The estimated sizes and weights of hydrogen and oxygen vessels of the power-plant and propulsion system in this research offers a maximum of four hours of flying time for the UAS mission; this is based on a Horizon (H-1000) PEM stack.