Re: Unmanned sub crosses ocean

From: Hans-Georg Michna (hans-georgNoEmailPlease_at_michna.com)
Date: 11/23/04 

Date: Tue, 23 Nov 2004 11:26:47 +0100

On Tue, 23 Nov 2004 00:30:11 GMT, Mark Borgerson
<m-a-r-k@oes.to> wrote:

>In article <pbo4q09fgoop9ts5jim138gsc3j3m0s8eb@4ax.com>, hans-
>georgNoEmailPlease@michna.com says...

>> 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.

Mark,

thanks for these interesting questions!

I don't know. I'm actually thinking of a sail that is much
smaller than wave height in bad weather. A very simple
assumption is that the vessel tries its best to maintain course.
If it really can't make it, it can try to let itself be driven
back along its course, rather than wandering about aimlessly.
Essentially it would wait for smoother weather.

I could imagine though that, as long as it can roughly keep its
body's orientation, it can probably keep going even in rough
seas. It's got to be rugged enough not to break even in the
worst weather, of course.

>> 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.

I'm envisioning a sail that is relatively small in relation to
the overall size of the vessel.

>> 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.

My idea is a pretty small one, no longer than 1 m, possibly even
shorter, only the size of a model boat. Too small to make a dent
into other ocean-going vessels. And since it would normally sail
the high seas, it wouldn't be a danger to small coastal boats or
to anything else. It would be comparable to a piece of wood
floating around.

All this is still extremely hypothetic, but I still think it
could come true soon.

I've put it up as a web site now, just for fun. Check
http://www.michna.com/sailbot.htm. Would you like your name on
it if I cite your questions from this message? I'll put it on
now with your last name abbreviated to a single letter. If you
don't like it or if you don't mind your full name appearing,
please let me know.

Hans-Georg 

-- 
No mail, please.

Relevant Pages

  • Re: Unmanned sub crosses ocean
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