Plumes extending nearly 1000 m from the 1500–2000 m deep seafloor of Guaymas Basin were detected from below by the 23.5‐kHz inverted echo‐sounder of the Scripps Deep Tow vehicle. Individual sound reflectors (bubbles or drops) rise at approximately 17 cm/s in one plume. The Deep Tow side scan records provide more information on the plumes' structure at the altitude of the vehicle (75 m), where some form multiple side scan targets, one 20 m across. Near‐bottom 4‐kHz profiles show that plumes overlie either young fault traces associated with extensional faulting at the basin's spreading centers or outcrops of tilted beds beside strike‐slip faults. We infer from analysis of the Deep Tow observations, field relationships, and knowledge of the geology of this basin that the plumes are made of light hydrocarbons, perhaps mainly methane, that emanate from seabed seeps. One of the acoustically detected plumes was at a spreading‐axis hydrothermal field, which has many buoyant, acoustically transparent thermal plumes, some of which are rich in dissolved hydrocarbons.
Spherical flotation units of 99.9% Al 2 O 3 ceramic have been successfully produced by Deepsea Power & Light for application to 11 km ROV/AUV systems. The 3.6-inch (91.45 mm) OD seamless hollow spheres with 0.34 weight/displacement ratio have routinely withstood proof testing to 30,000 psi (207 MPa), 1000 hour sustained pressurization to 25,000 psi, and 10,000 pressure cycles to 20,000 psi (138 MPa). Each of the spheres provides 0.6 lb (272 gr) of lift. When encased in a 0.2-inch thick buoyant elastomeric boot, they withstood impact on concrete from a 6 ft elevation. Together with syntactic foam, they will provide most of the required lift for the WHOI HROV system with 36,000 ft (11 km) depth capability. An extensive QA procedure has been developed for each sphere, which requires not only adherence to tight dimensional and thickness specifications but also acoustic emission criteria during pressure testing.Deepsea Power & Light is also in the process of developing a roto-molding process for casting of alumina ceramic spheres with larger diameter for the whole range of ocean depths from 10,000 ft (3000 m) to 36,000 ft (11,000 m). Spheres with 5-inch (127 mm) and 8-inch (203.2 mm) outside diameter have already been successfully cast. The casting of even larger spheres will proceed upon acquisition of a larger furnace.
Spherical flotation units of 99.9% Al2O3 ceramic have been successfully produced by DeepSea Power & Light for application to ocean trench systems, such as the Woods Hole Oceanographic Institution (WHOI) hybrid remotely operated vehicle (HROV) Nereus and other high-performance systems requiring maximum buoyancy with minimum air weight. WHOI successfully operated their HROV in the Mariana Trench Challenger Deep in Summer 2009, scooting across the trench floor for a total of 11 h at 36,000 feet (11,000 m). More than 1,750 3.6-inch (91.45 mm), OD seamless hollow ceramic spheres, each generating 0.6 lb (272 g) of lift, provided Nereus its buoyancy. The spheres, with a 0.34 weight/displacement ratio, withstood proof testing to 30,000 psi (207 MPa), 1,000 h of sustained pressurization to 25,000 psi and 10,000 pressure cycles to 20,000 psi (138 MPa). In addition, each of the WHOI spheres withstood 15 h at 18 ksi static pressure hold. When encased in a 0.2-inch thick buoyant elastomeric boot, they withstood impact on a concrete floor from a 6-foot elevation. An extensive quality assurance (QA) procedure is applied to 100% of manufactured spheres, with strict adherence to tight dimensional and thickness specifications as well as pressure test acoustic emission criteria (<xref ref-type="fig" rid="fig1">Figure 1</xref>).<fig id="fig1"><label>FIGURE 1</label><caption>Engineers at WHOI demonstrate the toughness of DSPL’s jacketed hollow ceramic spheres they use to provide lift at extreme pressures for their deep diving HROV, Nereus. (Photo by Tom Kleindinst, WHOI).</caption><graphic href="MTS43524fig01.tif"/></fig>DeepSea Power & Light has additionally demonstrated the process for casting larger alumina ceramic spheres with an 8.6-inch (218.4 mm) outside diameter for the whole range of ocean depths from 10,000 feet (3000 m) to 36,000 feet (11,000 m). The larger spheres were successfully used offshore by Scripps Institution of Oceanography/UCSD in summer 2005 in an experimental free vehicle sediment sampler that impacted the seafloor at 2 m/s at a water depth of 2,200 m, dropped a weight, then rebounded to the surface with its cargo of sediment.
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