Failure Rates and Failure Reduction Efforts in the U.S. National Deep Submergence Facility’s Autonomous Underwater Vehicle Sentry

The Autonomous Underwater Vehicle (AUV) Sentry is a part of the U.S. National Deep Submergence Facility (NDSF) and is deployed on scientific missions 120 - 200 days per year. Here we present a detailed analysis of failures, failure tracking methods, and failure reduction techniques as used within the Sentry program between 2009 and 2016. We have tabulated data from more than 400 dives conducted on dozens of expeditions with a wide variety of mission objectives that are used to describe a detailed picture of failures, failure rates, and initiatives to address failures. We begin by discussing the nature of Sentry and the missions it is tasked with. We then define metrics for failures and reliability. AUVs are complex systems often comprising both the vehicle and tens of sensors and ancillary systems. Because the vehicle is expected to deliver data for scientific users, we adopt a mission focused view of failure. After defining metrics, we discuss overall reliability rates and the breakdown of when failures occur relative to cruises, overhauls, and major vehicle changes. We present failure pareto charts and discuss the changes in major failure modes as the system has matured.