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The spheres were tested to 1, atm at Vitrovex plant in Germany. Provision was made for two bulkhead connectors and a single purge port. The purge port is used to cycle air over a desiccant to dry it prior to deployment, preventing condensation on electronics or camera lenses at the cold temperatures found at depth. The Edgetech BART Board was selected for acoustic command and control because it has two release commands, with an optional daughter board providing four more.
These proved invaluable at-sea. Photo by Charlie Arneson, used with permission, Earthship Productions. The upper plate holds the recovery beacons and battery. Below the lower plate, the bulkhead connectors bring copper connections through from the outside. The camera internal to the sphere used rechargeable LiPO camera battery packs. Camera sphere The camera, the controller, and all other recorders and components were mounted in one hemisphere. The matching hemisphere was polished to optical clarity and was closed once the detailed pre-cruise checkout was complete. The spacious interior volume of the Vitrovex glass spheres and ability to take high quality images directly through their polished glass walls was a powerful combination.
In the black depths of the sea, the camera would need to shoot with the lens nearly wide open — resulting in extremely limited depth-of-field. Accurate focusing was critical. A 1-ft deep ft long focusing trough was built to gather focusing data through a horizontal water column, with the camera lens positioned close to the inner apex of a polished glass hemisphere. Standard SubConn connectors were used with adapter ports to bridge between standard thread lengths and the longer threads needs for glass spheres. A special high-pressure fitting was also made by the Lander Team to adapt a fiberoptic feedthrough, designed by Acheron, to the lander camera sphere.
Connectors made by SeaCon were used in the back-up timer and junction bottle. The unit was adapted with some effort to both the submersible and landers. Given the attenuation of the transmitted source level through the 13 to 15 km operational slant range, the L3 Nautronix was designed with a very sensitive receiver. Samplers and sensors Samplers on the lander included Niskin Bottle water samplers, fish net traps, and sediment corers.
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The fish traps worked well for amphipods. An additional Niskin bottle was mounted on the drop arm to lay on the seafloor and capture animals. The sediment samplers could benefit from further refinement. DR, a selfcontained, submersible depth recorder. Underwater connectors and fully assembled glass spheres were individually tested to 18, psi. Load tests were performed on critical load-bearing components. Photo used with permission, Earthship Productions. The lander lay horizontally on deck to make access to all segments convenient and the platform more stable on deck in transit.
With multiple dives, the deck crew became quite adept at handling the large lander. The lander dove largely straight down and back as expected. The fall and rise rates were high enough that little time was spent in any current, minimizing lateral offset. The Edgetech comm system provided good slant ranges. It was important to recover the biological samples as soon as possible. Utilization of common components across several vehicle platforms dramatically shortened the development time.
In similar application by Dr. Ken Richter, SPAWAR, sediments are captured in a free vehicle microbial power cell by spring-loaded doors that snap shut with the anchor release and vehicle rise.cansinolingders.ga/1661-fakeababy-coupon.php
April Editorial Focus EdgeTech/Global Ocean Design | Featured Stories
The transpond function may be used for Long Baseline Navigation LBL , where a group of four or more transponders are positioned hundreds of meters apart, providing navigational waypoints for AUV ops, mooring motion measurements, and even tracking for fish migration studies.
A ship uses the transponder function for precision navigation.
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An LBL system has two main components. The first element comprises a number of acoustic transponders moored in fixed locations on the seabed. The transponders are typically mounted in the corners of the operations site.
LBL systems yield very high accuracy of generally better than 1 m and sometimes as good as 0. The positions can be converted from relative X, Y, Z position to real world coordinates. One of the stranger applications is the detonation of unexploded ordnance UXO , hazardous leftovers from the two Great Wars dumped at sea. These pose an active danger to fisherman, boaters, offshore construction and pipe laying. Once identified by side-scan surveys, an Acoustic Actuator is used with a high explosives charge to remotely detonate the UXO, activated from a safe distance either acoustically or with a timer.
An unexploded mine left , has an acoustic actuator center to trigger an explosives charge right using an acoustic release or a timer.
Benthic landers are observational platforms that free fall and land on the seafloor to sense and sample the physical, chemical, and biological activity. Benthic landers are autonomous and have deployment durations from a few days to multiple years. Benthic landers come in a variety of shapes and sizes depending upon the instrumentation they carry and the deployment vessels available. They are capable of working at any ocean depth. An artist's conception of a proposed complex benthic lander.
The right side shows the sub-systems retracted during descent, the left side shows the systems deployed. Once on the seafloor, acoustic commands deploy drop arms, rotate the vehicle for an in situ panorama photo, and other functions.
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Through-hull connectors bring the commands where needed: Once the mission is complete, additional commands are used to close traps, drop light arms, and other pre-release functions. A burnwire loop held the anchors and the pair of Niskin bottles open. Operational tips 1 Transducer placement It is important to place the release transducer in a location where it has a relatively open view to the surface to provide the clearest acoustic path for the shipboard transducer signals.
Isolation of the release housing from a benthic lander frame may be advised. Likewise, pelican hook and drop link should be of the same material. Three choices are common: This will passively dry the air, but relies on dispersion of water vapor, which requires 1 or 2 days lead time; 2 high pressure dry nitrogen bottles and a vacuum pump are used to cycle in dry N2 the high-pressure bottles have some obvious shipping drawbacks and inherent dangers in the field ; or 3 a deck purge box uses a vacuum pump to draw moisture laden air out, then uses the vacuum to draw air back in, forcing it to pass through a desiccant cartridge, dynamically drying the air.
Acoustic releases can do more than just drop an anchor. Clever mechanical mechanisms can provide secondary functions without compromising the anchor release. And while not a true acoustic modem, the BART Board provides ocean engineers and marine system designers a powerful command-and-control system in a small, power efficient package at a very affordable cost.