JMS was contracted to design a new lightweight aluminum hypobaric hatch cover and hinge mechanism for the Hypobaric/Hyperbaric Chamber at the Naval Submarine Medical Research Laboratory at the SUBASE New London, CT. Currently the chamber can only be used at depth. With the addition of the new hypobaric hatch cover the chamber will be suitable for use at altitude as well as at depth. The hatch cover and hinge will be constructed of aluminum to guarantee a lightweight structure that is easily maneuvered and handled by a single operator. A finite element analysis (FEA) of the structure was performed to ensure that the design is in accordance with the requirements of the Safety Standard for Pressure Vessels for Human Occupancy, Unified Facilities Criteria Design: Hyperbaric Facilities, and the Boiler and Pressure Vessel Code. The use of FEA tools allowed JMS to optimize the design to best meet the objectives of the Naval Submarine Medical Research Laboratory and achieve an adequate level of safety and reliability.