Equip submarines with external sails sans masts. Control the sails via cables attached to the sails at various points.
Ride the currents just like a schooner rides the tradewinds, tacking to move "upcurrent" or just up and down.-- phoenix, Oct 28 2003 http://picasaweb.go...5468869949219650354 for when the wind dies [xenzag, May 12 2010] 1800 Submarine http://en.wikipedia...us_(1800_submarine)Robert Fulton's Nautilus [whlanteigne, Apr 14 2013] I suspect the ocean currents are not generally fast enough for your porpoises.-- DrCurry, Oct 28 2003 You mean porpoises, surely [DC].-- squeak, Oct 28 2003 Porpoises don't ride in submarines.-- phoenix, Oct 28 2003 you can only get propulsion from these currents if you are in a spot of water that mover the other way (just like sailing) ocean currents reach a few miles per hour max, so you wil not be able to go very fast.-- nietsch, Mar 21 2004 I'm sure that there are extremely fast currents and "thermals" and everything else that there is with winds, probably can be found similarly in sea currents. Wind sails can run the wind sailships at speeds that are faster than the wind itself, by pushing sideways, and water energy is concentrated because of the extremely higher mass to area, so it SHOULD be possible to reach high speeds even in slow moving currents.
(PS. I just deleted my entry with the same name...)-- pashute, May 12 2010 I don't think this would work; you would drift like a hot air balloon. Sailing ships extract energy to propel them by using the fiddrence between the movement of air and the movement of water. Hence having a keel & rudder as well as sails.-- pocmloc, May 12 2010 [pomloc] is right (except his spelling "fiddrence "?), this is bad science. Sailing works by using the energy between the air and the water vectors. Subs are in the water so there is no differential to harvest, so they will just drift with the current. (-)-- MisterQED, May 12 2010 I thought this was going to be a sub with atmospheric kites, which would work and perhaps be useful in rough seas.-- FlyingToaster, May 12 2010 The OP describes a "sea anchor."
I believe Robert Fulton (of "Clermont" or "Fulton's Folly" fame) designed a sail-powered submarine (the Nautilus), but the sail was above the water and caught the wind.-- whlanteigne, Apr 14 2013 What with the high drag on an object the size of a submarine, you won't need a sea anchor in order to "catch" the current. You're located in a medium which is moving, and sans external forces (like your propellor) - you will very rapidly adopt the same speed and direction of the current you're in.
Sailing is different because you have a toe-hold in a different medium - you're playing on the different speeds, directions, and purchase you can get from the different mediums of the water and the air.
Anyhow, a submarine chucking out a sea anchor in order to "ride" a current is just a little bit inconsiderate of the physics involved.-- Custardguts, Apr 15 2013 I think sea anchors only work for floating vessels, and only to offset the effects of wind. Just about useless for a sub, and some of the experienced sailors I've met say they aren't much use for surface vessels either.-- whlanteigne, Apr 15 2013 The relevant analogy, shirley, would be with a hot air balloon rather than with a schooner? I don't think a submarine could schoon.-- MaxwellBuchanan, Apr 15 2013 It could if it had wheels.-- spidermother, Apr 16 2013 I believe Fulton's 1808 sub design was more like a sloop.-- whlanteigne, Apr 16 2013 random, halfbakery