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16 st / July 2014 www.sea-technology.com There were a total of six BIRNS Millennium 3M connector pairs throughout the pressure vessel. The BIRNS Millennium 3M connectors each had a 0.58-inch electrical insu- lation diameter and a fange dimen- sion of 1.5 inches. The 3M connectors had fve 16-AWG conductors and eight 20-AWG conductors. Two of the 3M cable assemblies were molded, and four were designed with pres- sure-balanced oil-flled (PBOF) cables with advanced oil-flled adapters in- corporating double-ferrule hydraulic fttings. This system reduced the risk of cut tubing found with the use of hose clamps in PBOF assemblies. It included two small rings that together formed a gentle wedge. When pushed down by the main nut, the rings gen- tly yet securely pressed against the tubing, which was supported internally with a stain- less steel tube insert, in turn sealing and re- taining it. A right-angle PBOF cable assem- bly with a mating pair of BIRNS Millennium 3O (0.70-inch electrical diameter) had 23 20-AWG conductors. The free-fooded architecture necessi- tated wet cables for individual components. These wet cables were either PBOF as- semblies, wherein the individual wires are immersed in an incompressible oil that is encased in a plastic tube, or molded cables where the entire cable is encapsulated in a custom polyurethane sheath. The functions of the wet cables include the emergency dropweight system, Bluefn battery power, propulsion, vehicle power switch, shore power connection, acoustic navigation and communications, nose line release, sound velocity sensor, and sonar or acoustic payloads. Connector Development Developing custom solutions for great depth and extend- ed use required precision engineering, including matching high pin density with glass reinforced epoxy (GRE) inserts capable of performing under great pressure. This provided superior dielectric characteristics and solid construction throughout, as it was developed with exclusive potting and bonding techniques, along with durable O-ring seals, to protect the connections when the AUV would operate in extended missions. The BIRNS Millennium connectors had replaceable electrical inserts for both receptacles and plugs to provide the option for future system modifcations if Blue- fn opted to change any confgurations. Each connector had insulated solder pots to reduce electrical interference, and integrally machined stainless square keys on the cable plug (CP) shells. This keying methodology greatly increased key strength and made the keying process more seamless, se- cure and user-friendly for AUV operators while mating and unmating connectors at sea. The connectors further provid- ed rugged connectivity by means of hard phosphor bronze hardware are those installed in the Bluefn sphere. The con- nectors ranged in size from the BIRNS Millennium 3G to the 3O, with a variety of pin quantities and pin diameters, from 10 22-AWG conductors installed on 3G connectors to combinations of 16-AWG and 20-AWG pinouts in con- nector pairs of the 3M. The 3G size in particular was an enabling component in that it was highly compact. It had an electrical insulation diameter of 0.33 inches and tight toler- ances between pins, with spacing of 0.08 inches center-to- center distance, and socket-to-socket clearance of only 0.02 inches. A slightly larger (0.46 inches) BIRNS Millennium 3K mating pair had 16-AWG conductors. (Top) Minute BIRNS Millennium 3G connector (0.33-inch) in- sert during rigorous continuity and insulation resistance test- ing procedures. (Bottom Left) BIRNS Millennium connectors served as the primary connector type for the AUV's main elec- tronics housing (MEH), the air-tight pressure vessel where sys- tem-critical electronics reside. (Bottom Right) Bluefn marine operations engineer removing foam to gain access to the MEH.