Re: Unmanned sub crosses ocean

From: Mark Borgerson (m-a-r-k_at_oes.to)
Date: 11/23/04 

Date: Tue, 23 Nov 2004 00:30:11 GMT

In article <pbo4q09fgoop9ts5jim138gsc3j3m0s8eb@4ax.com>, hans-
georgNoEmailPlease@michna.com says...
> On Sun, 21 Nov 2004 15:45:03 -0500, Alan Browne
> <alan.browne@FreeLunchVideotron.ca> wrote:
>
> >A sailboat requires control of sails (via winches), rudder, etc. An energy
> >outlay similar to that required by the device described for the ride it gets for
> >free from gravity v. buoyancy. (It's just moving some fluid a few cm every hour
> >or so, the rest is indeed 'free').
>
> Alan,
>
> the whole story prompted me to try to invent a GPS-navigating
> robotic sailboat. The rough theory is finished. I'm thinking of
> a mostly submerged vessel with a ballasted keel and only one
> sail consisting of an airfoil, looking a bit like an upwards
> protruding paddle, that can be moved in two axes, rotation and
> forward-backward inclination. No rudder. Control is similar to a
> windsurfing board.

If your vessel is semi-submerged, how will it react to waves where
the wave height is a significant fraction of the sail height?
It would seem that you would need a lot of steering engergy
to overcome turbulent wave action at the surface. If you
have ever tried to steer a normal sailboat down wind with
the seas behind you, you know what I mean about steering
energy.
>
> The aim is for simplicity and ruggedness. Such a vessel could
> transport some load over very long distances at a leisurely pace
> and actually quite quickly in strong winds. It could also serve
> as a fixed buoy, sailing a figure of 8 all the time to
> essentially keep its GPS-defined position.

I think there are critical scale factors relating vessel length,
wave height and period, and sail height.
>
> If the robotic vessel is too sluggish to tack, it would be
> programmed to always jibe instead. No big deal, as it could then
> sail mile-long tacks on the open ocean.

How is this robotic vessel going to obey the rules of the
road? A 5-m long research glider which spends most
of its time far below the surface is a lot less dangerous
to passing surface traffic than a 50-m multi-ton vessel
with no maneuverability and no clue about surface traffic
in its vicinity.
>
> Arriving at its destination, it would again sail a figure-of-8
> pattern until collected.
>
> It could be designed to be stable in relation to the wind
> direction to minimize energy consumption, i.e. it would adjust
> its direction, then freeze and sail roughly straight for a long
> distance without using any electricity at all, while accepting
> some deviation from the programmed track. The next adjustment or
> tack would then compensate for the accumulated track error. This
> way the vessel could move on very little energy, possibly
> economically enough to be recharged from solar panels during the
> day. But this is probably not required, as controlling the sail
> wouldn't use much energy anyway.
>
> Apart from the buoy task the only thing I could think of that it
> could be used for is smuggling. (:-) As the thing isn't all that
> difficult to conceive, I'm sure somebody will actually build it
> soon.
>
> Hans-Georg
>
Mark Borgerson

Relevant Pages

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