The torpedo doesnt surround itself using a bubble of air, but water vapour.
Cavitation is the principle where in area's of water with very low pressures (think bernoulli's eqn) the water vapourises to create a bubble (or
cavity hence the name). It is a form of low temperature boiling. The front tip of the torpedo is designed to form a large enough cavity for the rest
of the torpedo to be in thereby reducing the frictional drag (torp is in vapour not water- hence a massive difference in density=> reduction in drag).
This can normally only occur at speeds over 100knots (below that the full cavity wont form), hence the use of rockets on the russian
design(remember-its in vapour not water so a prop wont work!).
Most of the past reseach has been to avoid cavitation, when the cavities meet areas of high pressure again they implode causing massive damage to
metal surfaces such as propellers and rudders (it will eat through a metal prop in no time whatsoever if the prop isnt designed right!!! - have seen
it, is v. funny).
Directional control of the cavity is extreamly difficult hence the russian torp only being able to travel in a straight line. It is however being
worked upon by a number of countries invluding russia, US, UK, Farnce and India (probably china too, but not sure).
The US has conducted reseach into supercavitating projectiles for use as mine clearance (from a heicopter) and self defense systems for submarines.
None are known to be in service yet.
The ultimate aim is to produce small quick subs with the speed and agility of jetfighters but underwater. This scenario has been used to devlop a
sci-fi/future tech film at
www.deepangel.com... This site also has some links to further information of supercavitation. (and yes i know it is
fiction, but gives a good idea of what the tech's are working on).
As it says on the site run silent, run deep is history the fuure is to run fast run deep!!!
[edit on 13-11-2004 by paperplane_uk]
[edit on 13-11-2004 by paperplane_uk]
