Undersea Vehicles and National Needs (1996) / Chapter Skim
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Undersea Vehicle Capabilities and Technologies
Undersea Vehicle Capabilities and Technologies
Pages 18-46
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From page 18... ...
An understanding of development trends and influences within, and external to, the undersea vehicle industry is the next important step in determining research and development strategies and priorities. Indeed, some of the valuable aspects of vehicle development are driven largely by advances in other industries, both domestic and foreign.
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From page 19... ...
DSV endurance at the work site is limited by prolonged surface periods for crew change and vehicle replenishment. The cost per operating hour is usually much greater than for other vehicle types because of the extra cost attributable to crew accommodation and life support, the larger surface support ship needed to handle the heavier human-occupied vehicle in launch and retrieval, and the more limited availability therefore, the normally higher day rate of support ships.
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From page 20... ...
; adaptable to tools and sensors Depends on ROV size arid mission requirements Depends on ROV size Relative to surface/seafloor Real-time feedback to operator, long endurance capability, low cost per operating hour Tether cable potentially limits maneuverability arid range Untethered undersea vehicle, may be totally pre-programmed arid equipped with decision aids to operate autonomously; or operation may be monitored and revised by control instructions transmitted by a data link. Several to 1,000 m Few to 3,000 m Very few to 6,000 m 6 to 48 hours of propulsion May sit on bottom for extended periods 350 km demonstrated; near-term potential 1,500 km, depending on energy source 11 to 45 kg (25 to 100 lb)
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From page 21... ...
The mobility of ROVs is often restricted by tether drag, and their stability can be affected by wave action on the surface vessel, which is transferred down the tether. Despite the constraints to horizontal operations within the sea imposed by the tether, ROVs have provided a platform for conducting in situ observations within the water column with little disturbance of surrounding sea life.
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From page 25... ...
They are also generally stable. Viewing facilities for the human operator are good and continue to be improved, including stereo and new "augmented reality" compatibility.3 Hence, ROVs are inherently suited for working for extended periods, performing local surveys, operating in high-risk areas, and passing large quantities of realtime sensor information back to a surface support vessel.
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From page 26... ...
The performance UNDERSEA VEHICLES AND NATIONAL NEEDS characteristics of available energy sources are compared in Table 2-3. The table is divided into four types of energy systems: secondary batteries, primary batteries, fuel cells, and heat engines.
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From page 27... ...
For undersea vehicles, some new 4This information is based on current Lockheed Martin Corporation programs and plans and on independent research and development related to energy sources as described in internally published documents (Gentry, 1995)
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From page 28... ...
In this concept, stored hydrogen and oxygen are reacted in a fuel cell with the potential of rechargeability and specific energies of over 600 Wh/kg. The newer proton exchange membrane fuel cells offer many advantages over alkaline fuel cells, including lower cost, higher power capacities, improved tolerance to impurities in the reactant gases, and better long-term cycle performance.
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From page 29... ...
Most research and development in the field of energy storage occurs outside the undersea vehicles area. The committee anticipates that future energy system development applicable to undersea vehicles will derive mostly from the aerospace and automobile industries, where batteries and fuel cells are being evaluated for near-term use, and from the telecommunications and personal computer industries, where small-format lithium batteries are in development.
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From page 30... ...
Such a vehicle depends on advanced materials for structures to support its performance goals. Russian and Ukrainian undersea vehicle programs have developed advanced techniques for fabricating structures of titanium, ceramic, and composite materials, according to two teams of experts who recently surveyed the undersea vehicle programs of western Europe and the former Soviet Union, under the auspices of the World Technology Evaluation Center (Mooney et al., 1996; Seymour et al., 1994~.5 5These study teams included two members of this committee, J.B.
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From page 31... ...
Guidance and control of an undersea vehicle are generally implemented in a layered or hierarchical architecture. Guidance involves higher-level mission management activities, such as planning and directing vehicle movement through the water column; control operates at a lower functional level to interact with specific equipment on the vehicle.
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From page 32... ...
. UNDERSEA VEHICLES AND NATIONAL NEEDS techniques are being applied to offer AUVs an interpretive logic capability based on processing probabilistic data.
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From page 33... ...
Enhancements in undersea vehicle capabilities are closely tied to advancements in microprocessors and computer science. In the past 10 years processing signals and managing underwater vehicle systems have progressed from implementing a single desk-sized minicomputer to incorporating many, in some cases hundreds, of printed circuit board processing elements.
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From page 34... ...
Data incorporation from multiple sensors through a single analog to digital converter has given way to on-vehicle networks that extend through the data transmission system to the support platform to provide better displays of sensor information and increase reliability. AUV missions are clearly the most computation-intensive of undersea vehicle applications; yet these are easily being implemented with current computational capabilities.
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From page 35... ...
The vertical communication path enabled transmission of command signals at a rate of 2,400 bps and freezeframe video images were transmitted using data compression at a rate of 4,800 bps. The incorporation of compurationally capable, low power, algorithm-specific signal processing by Woods Hole Oceanographic Institution and Northeastern University (Stojanovic et al.,1993; Stojanovic et al., 1995)
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From page 36... ...
An important area of communications for undersea vehicles is the use of satellite or radio frequency links. Both the Woods Hole Oceanographic Institution and the Monterey Bay Aquarium Research Institute have used this method to display science results from ROVs working offshore in real time at the laboratories on shore.
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From page 37... ...
, and the Pennsylvania State University and Woods Hole Oceanographic Institution joint program. Sensors An important undersea vehicle mission is collecting data from various types of sensors.
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From page 38... ...
Chemical Sensors. Chemical sensors allow undersea vehicles to perform tasks that would otherwise require collecting water samples for laboratory analysis.
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From page 39... ...
The state of the art in CTDs has advanced to the point that commercial, off-the-shelf CTD sensors are acceptable for most situations encountered by undersea vehicles, including AUV requirements. Fouling of electrodes can be a problem for long-term deployments in shallow water (Bales and Levine, 1994)
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From page 40... ...
If the launch and recovery system can be designed to work safely in higher sea states, then the on-station time of the support vessel increases, and the vehicle is made more productive, that is, more diving days are available without shutting down operations because of weather and sea state. Undersea vehicles are usually positioned navigationally UNDERSEA VEHICLES AND NATIONAL NEEDS and launched, tracked, and recovered by surface ships, semisubmersibles, or platforms.
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From page 41... ...
The undersea vehicle Vehicle Subsystem Other Industries and Disciplines Unique Requirements and Adaptations for Undersea Vehicles Energy Propulsion Materials and Structures Navigation and Positioning Guidance and Mission Control Data Processing Communications Task-Performance Systems and Tools Sensors Launch and Recovery Auto industry/electric cars, computers, and communications Hydraulics, pumps, motors, valves, filters, plumbing, brushless do motors, propellers Aerospace, boat building, aluminum composites, 316 SS, acrylics, graphite reinforced plastics Aerospace/compass and gyros, video cameras, lighting, global positioning system/inertial navigation system (GPS/INS) PC industry, automatic control PC industry, object-oriented programming, computer-aided software engineering, computer science Fiber optics, signal processing, electronics Construction, robotics, and automation Other ocean sciences, instrumentation, micromachinery, medical sensors Other marine applications/boat handling Air independence, shipboard handling Hydrodynamics, pressure tolerance, ability to work .
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From page 42... ...
ARPA has supported work fuel cells, specifically for undersea vehicles, and progress is being made. However, there is a need for high-energy-density, lowcost-energy sources that can be commonly used on vehicle systems and that are not under development elsewhere.
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From page 43... ...
held June 3-6, 1994 in Monterey, California. MIT Sea Grant Report 94-24J.
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From page 44... ...
MIT Sea Grant College Program, Industry Collegium held January 15-16, 1991 in Cambridge, Massachusetts. EDO Report No.
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From page 45... ...
MIT Sea Grant Report 93-2J. Washington, D.C.: Marine Technology Society.
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From page 46... ...
Pp.25-28 MIT Sea Grant College Program' s Marine Industry Collegium and C.S. Draper Laboratories Workshop on Scientific and Environmental Data Collection with Autonomous Underwater Vehicles held March 3-4, 1992 in Cambridge, Massachusetts.
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