Missing sub construction material

[Colin Bignell]

That doesn't seem to be what they wanted with this vehicle.

[SteveW]

No, but it would have been an option and I was responding to the comment of "It is probably easier to achieve neutral buoyancy with a lighter structure."

[Colin Bignell]

A vessel that relies upon a separate buoyancy tank is vulnerable if that tank is damaged. One that is light enough to be inherently buoyant and needs ballast to keep it neutral, seems to be the safer option.

[Rod Speed]

Significantly cheaper, Titanium isnt cheap and neither is working it.

True.

[The Natural Philosopher]

Extremely high tensile strength, almost no *plastic* deformation before failure, and the ability to create complex shapes without massive tooling.

[soup]

Well only up to a point remember the sub/vessel has to be gotten from the water to the deck if it was very heavy the cranes on the ship would have to be larger this may well entail enlarging the ship which may be beyond what the hull (of the mothership) is capable off so... .

[Colin Bignell]

In this case, the vessel seems to launch from a submersible platform, so that weight has to be factored in too.

[mechanic]

Gosh, you should notify the US Navy/Coastguard about that, I bet they never thought about this!

[Colin Bignell]

Unless it was attached to the vessel. I have a reel of 0.75mm OD 7x7 stranded 316 stainless steel wire, which was used to make guide wires for introducing stent catheters. The drum is a bit smaller than the reel my garden hose is wound on and, when full, it contained 2.5 miles of wire.

[jon]

With all the money being splashed about, one would think they would have a specially designed ship with a float-in dry dock.

[Colin Bignell]

The Royal Fleet Auxiliary Bay class vessels, which have that, cost an average of £149 million each, although some of that would have been the weaponry. Even at the prices charged, it would take a lot of passengers to cover the cost.

[soup]

I would hazard they (and lots of other people) did, that will be why the sub is not outfitted with such a bouy

[soup]

Look at a ruler and get a grip in your minds eye just how small 3/4 of a mm is. Lets see wire of that diameter cope with undersea currents and surface winds.

Always remembering that you would need a lot more than the 2.5 miles(4Km)you have on your reel to go up but still bending to the various currents . Imagine undersea current was a constant four knots directly north-south and sub is 4,000 metres straight down, any wired floating beacon would need to cope with the depth and also the drift imposed by the current So we will imagine the float to the surface speed is 8 times that of the descent speed so 15 minutes (1/8) 2 hours) to surface so bouy will drift 1/4 X 4 =1 so 1 Nautical mile of drift. and 2.5 miles depth. This is two sides of a right angled triangle.

So using (that schoolboy favourite) Pythagoras theorem A^2+ B^2=C^2

2.5^2 + 1^2 = 7.25 so total length of wire required is root 7.25 2.69 say 2.7 (or even three to cope with minor depth variations)

TLDR For a wire of sufficient strength and sufficient length the reel would have to be enormous

[Chris Hogg]

A commentator on our local TV with naval experience suggested that the cable would have to be very strong not simply to break under its own weight.

On the national TV news tonight they reported that a debris field had been found near the Titanic wreck. They were being cautious because the debris field from the Titanic itself is vast, but I would have thought they'd have it all mapped in detail by now.

In a way, I hope it was a catastrophic failure. Death would have been virtually instantaneous, rather than the slow process of running out of oxygen and hoping against hope, but not really expecting to be rescued - that would be grim.

[Colin Bignell]

I don't need to do that. I have a couple of miles of the stuff left I can look at.

I have worked with the stuff and know just how strong and flexible it is. 7x7 cable laid was chosen to give it the flexibility to follow the arterial system from wrist or groin into the heart. Fitted on a free-running reel on the buoy, it doesn't need to hold the buoy in place; simply act as a guide back to where it came from.

As I said, the reel is a bit smaller than the one I wind my garden hose on. One that carries two or three times the amount would still be quite manageable.

A smaller diameter might well be strong enough to act as a guide wire, but the then problem might be sourcing that. I only managed to find one company willing to make the wire to my specification and I suspect that was only because it was a recent management buyout and they were quite desperate for work.

[Colin Bignell]

Such cables must exist, or they wouldn't be considering recovery from that depth. However, I am only suggesting a guide wire that can be followed back down to the vessel and the wire I have has absolutely no problem in lifting quite a bit more than the weight of wire on the reel.

[Chris Hogg]

Now confirmed that the sub imploded catastrophically. Five pieces located. Probably happened at the time contact was first lost. Recovery of bodies very unlikely.

[Rod Speed]

In spades now that that one has imploded.

[alan_m]

Do you mean like the small spool of wire for a shoulder launched wire guided missile with a range of 3Km+ ?

[soup]

Completely different environments.