These original Kirt's Cogitations™ may be reproduced
(no more than 5, please) provided proper credit is given to me, Kirt Blattenberger.
here to return to the Table of Contents.
Cog·i·ta·tion [koj-i-tey'-shun] – noun: Concerted
reflection; meditation; contemplation.
Kirt [kert] – proper noun: RF Cafe webmaster.
The Bottom Line Trumps Security
A key 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,
the technology to Russia, thereby undermining the effort.