|
In response to Bill Atkins:
Water doesn't compress. The pump simply sucks water in and increases it's
velocity. The nozel then decreases the apeture which creates pressure as the
large volume of water increases speed to get out of the smaller opening.
Since water doesn't compress, the pump can suck and blow just as
efficiently at 1,000ft as 10ft. Certain other fluids have been created that do
not compress, but also lubricate and protect. These hydraulic fluids would be
the best thing to seal an electric motor at depth. As long as the seal can
keep the fluid in at sea-level, it should be capable of doing the same when
submerged. Then a seal much like a dripless packing tube found on
inboard-powered boats may be an adequate seal.
I would still rather have two pumps on board, in case one failed, and to
give added manueverabilty. Also I'd want to be able to aim the nozels.
My question, however, is this- would a jet stream be as efficient as a
propeller AT SLOW SPEEDS? The benefit of a propeller is that it can be tuned to
the work it is doing. Angle, pitch, diameter- a psub like ours will have a lot
of resistance and won't be very fast.
That being said, consider this: A hydraulic pump mounted inside the hull,
driven by an electric motor. This pump works on a closed-system, and
recirculates hydraulic fluid which drives propellers. Again, I'd choose two
pumps (one for each side, which provision to drive both props off just one
pump), for added safety and manueverabiltiy. You don't have to
pressure-compensate anything, and no moving parts are exiting the main hull,
just a few pipes with cut-off valves.
|