Sea Technology

NOV 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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editorial SEA TECHNOLOGY ® I NCLUDING U NDER S EA TECHNOLOGY The Industry's Recognized Authority for Design, Engineering and Application of Equipment and Services in the Global Ocean Community Charles H. Bussmann Founder and Publisher 1924-1999 publisher managing editor assistant editor editorial consultant production manager assistant design/ website manager advertising service manager C. Amos Bussmann Aileen Torres-Bennett Alaina Monismith Charles W. Covey Russell S. Conward Joshua Ortega Susan M. Ingle Owen ADVERTISING REPRESENTATIVES: HEADQUARTERS C. Amos Bussmann 1600 Wilson Blvd., Suite 1010 Arlington, VA 22209 Tel: (703) 524-3136 • FAX: (703) 841-0852 e-mail: NORTH AMERICA EAST COAST Clive Bullard Bullard Communications 107 Lane Gate Road Cold Spring, NY 10516 Tel: (845) 231-0846 • FAX: (845) 265-9695 e-mail: NORTH AMERICA WEST COAST John Sabo Barbara Sabo John Sabo Associates 447 Herondo St. #305 Hermosa Beach, CA 90254 Tel: (310) 379-8455 • FAX: (310) 798-1394 e-mail: EUROPE John Gold John F. Gold & Associates "Highview" 18a Aultone Way Sutton, Surrey, SM1 3LE, England Phone/FAX Nat'l: 020-8641-7717 Int'l: +44-20-8641-7717 e-mail: Sea Technology back issues available on microform. Contact: NA Publishing, Inc. P.O. Box 998, Ann Arbor, MI 48106-0998 1-800-420-6272 COMPASS PUBLICATIONS, INC. 1600 Wilson Blvd., Suite 1010 Arlington, VA 22209-2510 Tel: (703) 524-3136 FAX: (703) 841-0852 publishers of: Sea Technology Commercial Fisheries News Fish Farming News Commercial Marine Directory Fish Farmers Phone Book/Directory Sea Technology Buyers Guide/Directory Sea Tech e-News Donald Brown, ISS Fleet Support Team, Boeing Harry Henshaw, ISS Chief System Engineer, Boeing Inertial Navigation Technology: Cold War-Era Tool Evolves S tarting in the early 1950s, with nuclear deterrence as the top military priority, the United States set out on a path that produced remarkable technological advances, including nuclear power for propulsion, solid fuels for rocket motors, and accurate inertial navigation equipment for missile alignment and ship positioning. An achievement sometimes overlooked is the development of a machine to navigate without the need for external references, such as star readings, land sightings, radar and radio beacons. The concept seemed simple: maintain a steady platform through use of gyroscopes and conduct acceleration measurements on that platform using mathematics and knowledge of the Earth's dynamics to compute the position, velocity and attitude of the vehicle. Initially, these were very crude devices, but through a continuous series of technological breakthroughs in instruments, computers and mechanization improvements, these machines, known as inertial systems, achieved extraordinary levels of accuracy. Those used for guiding missiles were soon called inertial guidance systems, and those used to navigate over the surface of the earth became known as inertial navigation systems (INSs). In 1954, the USS Nautilus was launched using nuclear propulsion, allowing it to remain submerged for a seemingly endless period. While the USS Nautilus was breaking records and traveling to locations previously beyond the limits of submarines, Russia launched Sputnik 1 in October 1957, and the space race was on, with the U.S. far behind. The American need to show the world that the U.S. was just as technologically advanced was answered in one way when the USS Nautilus made the frst under-ice transit of the North Pole. The ability to navigate under the ice with no access to stars or other references at extreme latitudes was enabled by the N6A-1 inertial navigation system, a naval adaptation of the N6A Navaho supersonic intercontinental cruise missile. Following the success of the N6A-1, the MK 2 Mod 0 ship inertial navigation system (SINS) was developed using a gas-bearing, single-degree-of-freedom gyro and pendulous velocity meter. The frst U.S. nuclear ballistic missile submarine, the USS George Washington, departed for its frst 60-day operational mission on November 15, 1960 with SINS, which allowed the submarine to remain submerged and hidden for long periods, creating a truly credible nuclear deterrent. As the Cold War escalated in the 1970s, the need for more stealth and accuracy became apparent. Industry responded by developing more technology, such as the electrostatically supported gyro navigation (ESGN) system. ESGN was based on the dynamics of a spinning mass; if one could isolate this spinning object from all environmental effects, its accuracy would be unlimited. This complex machine proved to be a strikingly accurate inertial navigator and is the primary inertial navigation system for the entire U.S. Trident feet today. An effort to fnd a new gyro technology that could eventually replace the ESGN turned out to be a diffcult task. No other technologies in the commercial or military complex could meet the accuracy needed. Eventually, in the late 1990s, it was recognized that a fber-optic rate-sensing gyro, with a mechanization that exploited the benefts of fber-optic technology while suppressing its weaknesses, had the potential to satisfy the Navy's need for precision and endurance. Today, new breakthroughs are being sought to address future weapons systems requirements and meet the need for reduced lifecycle cost through modularity, automation and usage of open architecture. To meet those needs, industry is exploring advancements in fber-optic INS, ground-reference velocity, signals of opportunity, gravity matching for bounding of position errors and measuring ship shaft speed as a back-up source for velocity references. Inertial navigation technology will continue to evolve to customer needs and mission requirements. n November 2013 / st 7

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