Design and Testing of a Self-Mooring AUV Brian McCarter * , Robert Briggs † , Stephen Portner † , Dan Stilwell * , Wayne Neu † , Ryan Coe † , Richard Duelley † , Dexter Malley ‡ , and Jason Mims ‡ * The Bradley Department of Electrical and Computer Engineering, † Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA {mccarter,rcbriggs,sportner,stilwell,neu,ryancoe,nifty}@vt.edu ‡ Naval Oceanographic Office, Stennis Space Center, MS {dexter.malley,jason.mims1}@navy.mil Abstract—The Virginia Tech Self-Mooring AUV is capable of mooring itself on the seafloor. Its principal mission is to deploy bottom-mounted sensors without the need for a support ship to visit the mooring location. The mooring concept was previously demonstrated using a small-scale prototype. It has, more recently, been transitioned to a full-scale system and successfully demonstrated in the field. In this paper, we document the design of the full-scale vehicle and present results from field trials. I. I NTRODUCTION Autonomous underwater vehicles are commonly used to collect environmental data where manned missions are either impractical or infeasible. One desirable application is the long- term monitoring of a specific location, a task that is generally restricted to bottom-mounted sensors deployed from a ship. The Virginia Tech Self-Mooring AUV is designed so that fixed bottom-mounted sensors can be deployed without the need for a ship to visit the deployment location. A typical mooring mission has three phases: ingress where the vehicle is deployed and transits to its target, mooring where it anchors itself and remains in a low power state near the seafloor, and egress in which the vehicle returns to a recovery point. The anchor is left behind upon egress, so the mooring system can be used only once per deployment. The Self-Mooring AUV is designed to be moored on station for up to a year (depending on the power draw of the sensor payload) with a total transit range of 100 nautical miles at 4 knots and a 0.5 knot head current. Its maximum transit and mooring depth is 500 meters. It is man portable, and can be deployed and recovered by a small craft with one or two crew. Table I summarizes the principal characteristics of the Self- Mooring AUV. A. Ingress The vehicle starts at the deployment point D in Fig. 1, and transits toward the target surface location T . The AUV is required to end its ingress within a 200 meter circular error probable (CEP) on the surface. It will then deploy an anchor, release buoyancy and fall to the seafloor. On the bottom, the vehicle is required to be within a 50 meter CEP of its last TABLE I: Self-Mooring AUV Principal Characteristics Parameter Ingress Egress Length 95.7 in 81.3 in Weight 111.5 lb 92.5 lb Diameter 6.9 in Cruise Speed 4 knots Range 100 nautical miles (against 0.5 knot current) Max. Deployment Time 1 year (assuming max. travel range) Maximum Depth 500 meters Communication GPS, Acoustic, 900 MHz RF, Iridium Satellite, 802.11g WiFi known surface fix. The CEP requirements are intended to allow a survey craft to easily find the AUV and record its exact position, as ground truth reference for sensor data. B. Mooring The AUV remains moored on the seafloor for a pre- determined period or until it receives an acoustic release command. While moored it remains in a low power state. Only the sensor payload remains active during this phase. C. Egress At the end of the mooring phase, the vehicle will release the anchor by burning a galvanic release attached to the mooring line. The AUV will float to the surface and proceed to a predetermined recovery point R in Fig. 1. The satellite communication link provides an opportunity for operators to command a new egress destination once the AUV reaches the surface. When it arrives at the recovery point, the vehicle will activate a strobe and wait on the surface to be picked up. D Deployment S R Recovery T Ingress Egress Target Surface Location Actual Surface Location Surface CEP Mooring CEP Fig. 1: Mission Profile