[PSUBS-MAILIST] Unusual propulsion system

[TeslaTony@aol.com]

A long time ago I read about using flippers (like those of a fish, shark or 
whale) on a boat and how much more efficient they are, but I can't help 
noticing that muscles are difficult to imitate with motors or selenoids 
efficiently and you always get a side-to-side or up-down motion in the body 
of the craft, plus it is rather difficult to go into reverse with.

The second problem isn't that hard to remedy, just imitate a Mantaray with 
the wings on either side rippling to push itself along, which has some nice 
advantages in the maneuverability department, but the thing still has to be 
powered.

Next I found out about a material called  "Muscle Wires," an alloy of Nickel 
and Titanium developed by the Naval Ordinance Laboratory (hence another of 
its names, NiTiNOL). The unusual property of this material is it contracts up 
to 8% (prefereably only 4% though) when heated and expands when cooled, 
meaning that properly thin wires can be heated with an electrical current to 
act just like muscles.
 Now there is a book out that has several projects that use muscle wires, and 
one project is for a tube that has two muscle wires running through it and 
one power wire, allowing the thing to bend in one of three directions on 
command.

But suppose that there were several tubes made between one and five feet long 
(or whatever size tilts your wagon), designed to go up and down then encased 
in a gelatinous or rubbery plastic that isn't bothered by water or high 
pressure, attached to a controller then strapped onto the sides of a sub, 
creating a weed-free silent propulsion system for a sub that may negate the 
need for a ballast tank (although some Mantarays might think the sub is 
rather sexy and lead to some very interesting experiences for you, the Manta 
and the sub.

What is all of your takes on this?

Anthony