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Cog·i·ta·tion [koj-i-tey'-shun] – noun: Concerted thought or
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The Bottom Line Trumps Security
technology necessary to create acoustically silent submarines is the
production of the precisely machined massive propellers that provide
the motive force. Cavitation, a phenomenon that generates air bubbles
in regions around the propeller where the local pressure is lower than
the vaporization pressure of water, generates noises that sound like
fingers snapping, and is a major betraying sonar signature of submarine
models. Cruising at great depths where pressure is higher helps mask
the effect, but the time submarines are most vulnerable are when nearer
to the surface. The good news it that finite element computer modeling
has produced shapes capable of eliminating the cavitation, but extremely
precise machinery is required to craft the 20-foot-plus diameter, 40-ton-plus
behemoths. Such technology would provide significant advantage to the
Navy. The bad news is that a few years back Toshiba, who was contracted
by the Navy to build the milling machines to do the job,
illegally sold the technology to Russia, thereby undermining the