Re: Waterjet Propulsion? [Not just AIP anymore <g>]

[Ray Keefer <Ray.Keefer@eng.Sun.COM>]

Hi Coast,

> Seems like I've read or heard
> that waterjet propulsion isn't practical for slower moving vehicles.
> 

I don't know. I have heard either way.

>         It seems to me that a waterjet system would eliminate the 
> problems [if any] associated with sealing a through-hull drive shaft 
> turning a propeller.

Depends where the impeller is. If it is outside of the hull then you
have to get the power out to it some how. A shaft through-hull would be a
way to do that. If the impeller is inside the hull then you have even more
complication. 

The duct for the water to flow to the impeller and the duct back out would
have to be stressed to handle the pressure differentials. In other words if
you have a 1 atm sub then the ducting would have to be as strong as the 
hull. Else the duct would just be a weak spot exposed to the pressure
of water at depth. Ready to burst open and flood your sub.

Still you have to get power to the impeller. There will have to be a
seal. If you drive the impeller with a shaft you will need a seal for the
shaft. 

>   It would also eliminate any dangers a spinning
> prop would have on anyone swimming near the sub.

Good point. Shrouded propellors are probably the next best choice.

Regards,
Ray