View through the door of the SOFIA project

The National Aeronautics and Space Administration (NASA), and Deutsches Zentrum Mir Luft- und Raumfahrt e.V. (DLR) are working together to create a Stratospheric Observatory for Infrared Astronomy (SOFIA) based on a modified Boeing 747-SP aircraft. One of the key elements of the modification is a new door system that protects the 2.5 meter infrared telescope during flight by covering the aircraft cavity within which the telescope resides. The door system follows the telescope\´s motion to provide an unvignetted view of the sky, while reducing turbulence inside the cavity. This paper describes the value added by a productive interaction of reliability engineering with the integrated product design team at NASA Ames Research Center that was responsible for the design of this "cavity door" system. The intent of this paper is to describe the interaction with the design team, to point out key reliability improvement strategies applied to the cavity door system, and to offer a few principles to guide interaction of reliability engineers with a design team. It is shown, for example, that significant assistance to improve reliability is achievable with a thorough, detailed understanding of the system\´s intent, and an organized approach to how it might fail to carry-out its intent. The specifics of the analyses performed are briefly summarized, but the paper emphasizes the key insights that were gained into the reliability of the system.