Re: [PSUBS-MAILIST] enquiry - Surface Propulsion

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

Hi Peter,

To surface transit to your dive location you have about 3 options.

1. Go all electric. Use the same motors to get you there and back that you use when submerged. The positives are that you only have one propulsion system to design, build, install, and maintain. Once in you are set and you have already designed it to handle pressures. The draw back is limited range and you are using your limited submerged battery power traveling on top.

2. Go internal combustion engine. The only type I would recommend is diesel. Why? Proven doable for years in Naval submarines. DO NOT USE A GAS ENGINE!
Gas fumes are explosive. That is why the military went to diesel as soon as
diesel engines got reliable enough. Positives are plenty of power, good range, possibilities of powering generators and compressors, oily fumes and the sweat sickly smell of diesel exhaust. Negatives is added complexity. Direct drive to a prop requires a pressure seal. Driving a generator gives you power that you can feed to your submerged propulsion system. The engine will need air intake piping, exhaust piping, fuel filling, cooling water intakes and cooling water exhaust. That creates the
need for more through holes with their compounding safety concerns.

3. Use a suface tender. Use a surface boat to do the transiting. You can push, tow, or carry your submersible. With a surface boat you can use inboard, outboard, or whatever type of engine you want. Diesel or gasoline is ok. It can be used without the sub for recreation which might be a selling point to your spouse. With a big enough boat you could put air compressors and generators on it and be able to turn you sub around quickly for another dive right there on the dive site. Or you could just
use a rubber dingy as George Kittredge showed in his video.

If you truely want fully autonomous operations. I would go diesel-electric with the diesel driving a generator. If you plan to travel more then a mile or two to get to your dive site, make sure the hull form is steamlined. More like a WWII military submarine as opposed to the blunt face science sub look. A sub like Kittredges might get up to around 6 knots with enough power thrown at it. Any more speed will require more streamlining and wetted hull length.

Regards,
Ray 

peter mckellar wrote:
> 
> Hi All,
> 
> how does everyone provide propulsion when on the surface with a fully autonomous submersible?
> 
> At this stage I'm entertaining all options, with maximum speed and range the preference (though no expectation that either could be adequately met with the limitations imposed below).  For safety's sake, i'm inclined to design with a pure electric engine for sub-marine propulsion and a separate surface engine to get to the dive location.  This leaves it pretty open (for surface anyway).
> 
> Something that works in both environments would be great, but I suspect is out of the question.
> 
> What sort of considerations would I need to make if i shut down the surface motor and expect it start again when i re-surface?
> 
> Some issues that the group may be able to clarify for me:
> 
> 1.  Pressure proofing/ambient tolerance
> 2.  Electrical insulation
> 3.  Corrosion
> 4.  Temperature stress if submerging when the engine is hot
> 5.  Safe fuel storage, combustion issues etc
> 
> Does anyone make engines with these demands in mind?
> 
> thanks in advance
> peter