h a l f b a k e r yClearly this is a metaphor for something.
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If a ship sinks while at deep ocean it's
often during a storm. The surface waters
are wild and cold the rain soaks your skin
and the possibility of colliding violently
with other pieces of floating wreckage is
fairly high. Further down, the waters are
still churning, but there is less violence
and, possibly, a higher chance of
survival.
Enter the submersible liferaft - a
pressure sphere with enough air to last
several days underwater, enough food
for several weeks and air bladders and
inflatable skirts so that the craft can bob
to the surface when the storm subsides
and stay the right way up when it gets
there.
Upon the order to abandon ship, the
occupants would be strapped into crash
couches and the liferaft catapulted
overboard. Following this, it would lurk
under the surface for 24 hours then bob
up and transmit a distress signal.
Submersible liferaft
[bristolz,
Jun 22 2005]
[link]
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I have no idea if this would work but it sounds really cool. I'm still concerned that debris could puncture or snag the raft and I'm not sure how something so buoyant would stay under the surface. |
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Perhaps something like that inflatable ball from a recent Bond film but on a larger scale? |
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Think steel ball with designer interior. |
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With its internal bladders filled with water, it would be neutrally buoyant about 30m down (I'm guessing that's deep enough). With the internal bladders filled with air it would float on the surface. A skirt could be inflated around the edge to give it additional stability and buoyancy when at the surface. |
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Brilliant. Probably useless, but still brilliant. |
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useless, probably brilliant but still useless :) |
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How would the air/sea rescue services rescue the occupants? |
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By clamping onto the hull with a big electro-magnet and hauling. Lot quicker than all that tedious mucking about with ropes and winches. |
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[Mayfly], on remote command, airbags could inflate to give it positive buoyancy. |
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Surface transponder towed on a wire for distress signalling. |
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Launch via vertical tube exiting through hull of ship below water level. Chlorate candles/lithium peroxide for air regeneration. |
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You only need to go down about 10m to avoid the worst of the storm effects. |
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Richard Branson would want one, I feel sure. |
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If the liferaft was built by the same people who constructed the ship then I think that I'd take my chances on the surface with the expendable poor people.
The mere provision of air tanks, wouldn't be sufficient. You'd also need some sort of air-cycling equipment much as they have on submarines. That means having a motor or engine of some description which in turn means a fuel supply. All this would need an engineer to be stationed aboard the survival globe in case any of the mechanisms went wrong plus a shed-load of safety equipment. I think I'll stick with the row-boat if it's all the same to you. |
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Air/sea rescue helicopter pilots have a difficult enough job trying to locate standard life rafts and plucking the occupants from the surface. Same with sea rescue boats. |
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I simply can't imagine any of them locating and connecting to a small submerged capsule in storm weather. Even if they could, it would cause the rescuers to be out at sea for far longer than necessary. Don't forget that they put their lives at risk too. |
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Forget elaborate GPS systems and "remote command airbags". Emergency equipment must be simple, robust and reliable. Emergency equipment is never checked often enough, but when it's needed it HAS to work. What's more reliable than a damn-great orange raft that floating on the surface and can be seen from a distance? |
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Hypothetical scenario 1:
Ship sinks. Everybody jumps into “submersible liferafts”. Emergency services turn up. No transponders are working. Emergency services declare everybody dead, as they can’t see any signs of life (nothing on the surface, sonar is confused by debris from accident). Emergency services go home. |
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Hypothetical scenario 2:
Ship sinks. Everybody jumps into “submersible liferafts”. Emergency services turn up. Detect a submersed liferaft. Man in rescue boat presses the “remote control airbags” button on his dashboard. Nothing happens. It’s still to stormy to send out divers. The rescue boat is rolling on the swell too much to send down a “big electro-magnet to clamp on the hull”. It would be like trying to thread a needle after 15 pints of lager. Weather worsens. Rescue craft have to go home, as it’s becoming dangerous for them to be there. |
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I could go on, but you get the idea… |
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Mayfly: If submersible liferafts were in existence it would be pretty irresponsible of the emergency services to turn up and declare everybody dead without checking back 24 hours after the wreck to see the liferafts pop up. Point 2's valid, though. You just have to weigh the reliability (and cost) of the craft against the advantage of being out of the storm for 24 hours. (and yes, it does have to pop up to the surface to make retreval even remotely likely) |
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DrBob: I'm not certain of my ground, but I think an engine is probably over the top. |
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UnaBubba: Only if you pressurise to depth. |
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Rigid submersible? Yes, but only for shallow depths. |
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[operating pressure of a nuclear submarine is about 40 atmospheres. Pressure at 30m below sea level is about 4 atmospheres.] |
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/The rescue boat is rolling on the swell too much to send down a “big electro-magnet to clamp on the hull”. It would be like trying to thread a needle after 15 pints of lager/ |
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Then what chance does a man on the end of a rope stand? In that respect it's no worse than the current system. |
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Take one St. Threef Sphere-O-Life and add to it, on a huxter tether, one Mayfly, Inc. Damn-Great Orange Raft that, floating on the surface, can be seen from a distance and carried the transponder antennae, etc. |
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I think this idea could work. Suggest these additions/modifications: |
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1) Floating platform. The sphere itself is connected by one or more nylon ropes to a really-really-big version of those donut-shaped flotation devices. This platform would be bright safety-orange, visible to helicopters. |
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2) Fixed bouyancy. The sphere itself doesn't float, the platform does; replace the complicated air-bladders with a simple mechanical winch to wind in the ropes and raise the sphere to sea-level(would rise to the surface in the middle of the donut) |
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Admittedly this would increase tossing from the waves and such quite abit through movement transmitted through the ropes; due to the large vertical size of the structure, however, there would still be little chance of overturning. |
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Wow, [bristolz] beat me to it. |
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