Is It Possible to Build an "Unsinkable" Ship? | Hacker News Reader

Is It Possible to Build an "Unsinkable" Ship?

scientificamerican.com

40 pointsrobdoherty238 comments

Of course you can build an unsinkable ship, as a matter of fact for some uses it's mandated by law.

If you build in fibreglass you will usually make a sandwich construction with fibreglass on either side and a layer of stiff foam in the middle. This construction technique is widely used because you can make strong and light boats with it. If you place enough foam in the lower part of the boat (enough to displace the weight of the ship) you have an unsinkable ship. Even if it breaks apart the pieces will still float.

I've seen small boats of this design in the harbour where I live that have been left unattended for years, and they don't sink, even when they're full of water.

The question is whether you can build a large and commercially viable ship that's unsinkable. For larger vessels it's usually not an option to have the lower decks filled with foam, since it detracts substantially from the cargo or passenger carrying ability.

For me, there's a difference between a boat (like a small sailing boat used by, let's say, 4 to 10 people) and a ship meassured in thousands of tons.

Good interview anyway. What I liked was the interviewees remarks on failure safe and failure tolerant, it's the later one you want. And no sound engineer will tell you absolute statements like this.

Whats also interessting after the Titanic sinking where the changes to the operating procedures they made. The sad thing is that seemingly a lot of engineers (and designers of whatever technical device) still have a hard time to think of the overall system instead of thinking in devices. The Space Shuttle programm is only one of the more prominent examples.

This. It's a classic risk-reward tradeoff. We can make most things much safer than they are, but we generally accept a lower level of safety for practical reasons.

Formula 1 racing was once one of the most dangerous activities on earth. Before the 1980s, a driver had a greater than 1 in 20 chance of dying in any given year. Since the death of Ayrton Senna in 1994, there has not been a single death in the sport.

We could achieve a similar change in the number of automobile-related deaths on public roads, but we consider the costs to be prohibitive. The public just aren't prepared to buy cars with roll-cages and bucket seats and multipoint harnesses. Not unreasonably, most people won't wear a helmet and a HANS device on their commute.

No-compromise engineering is often surprisingly straightforward. The hard bit tends to be working out the best compromise between your various design goals.

I clicked to post exactly this. I live on the Chesapeake Bay, and it seems like half the boats in the local Craigslist are of the unsinkable variety.

I think what the article is really getting at is whether or not it's possible to build an indestructible ship, and of course, the answer to that is no.

It's possible to make a ship that is much stronger than the people it carries -- most ships are, but that doesn't make the people any less fragile or more susceptible to death, injury or drowning.

Submarines are perhaps a superior design for this, on paper, but generally speaking, a submarine isn't where you want to be if the submarine is in any danger whatsoever.

So yeah, unsinkable boat? Check. Unsinkable passengers? No check.

A friend of mine has built the largest homemade submarine in the world (http://en.wikipedia.org/wiki/UC3_Nautilus) and they're clearly dangerous vessels, exactly because of what you're saying: If something goes wrong you're under 100 feet of water with no way of getting out. Even though UC3 Nautilus has a lot of built-in safety there have been a few situations that I would consider much more dangerous than sailing a dinghy across the bay of Biscay in a force gale 12 storm.

Unsinkable passengers? Sure. Just make everybody wear drysuits and floaties. It may not be Titanic chic, but you can't have everything.

If you get caught under deck while the unsinkable ship is flooding with water and possibly going belly-up, that might not help you much.

Our little 2 crew 303 had a shitload of foam inside the front of the hull. We used to tip it over all the time when racing. Once we sailed back to the club with the hull almost completely submerged (but not sinking).

It was unsinkable. But it wasn't a ship.

You're confusing ships with boats. They are not the same and are not interchangeable.

Correct.

Boats run under water.

Just because something is mandatory by law doesn't mean that it is possible.

I don't see why it would be impossible to make an unsinkable ship. Just make it out of material that's less dense than water.

Less dense than water and strong enough to withstand choppy seas, storms, pirates, accidents ...

It might not sink, but if it won't hold together, you can't keep people and stuff inside it. Of course, I'm not a materials expert, but this seems like a good reason our ships are made of metal.

There are many materials that are stronger than steel and lighter than water.

It's all about costs, not about technology.

Such as?

And stronger by weight or by volume? Stronger in tensile strength or by compression? In resisting flexing? Can it handle vibration and bending without cracking? Is it tough enough not to be abraded? Can it distribute stress (by giving a bit)?

The word "stronger" by itself has no meaning in engineering. You need to specify all those things I listed when describing stronger.

Like Pykrete: http://en.wikipedia.org/wiki/Pykrete

Ah - Project Habakkuk, wartime Britain at our lunatic best - 2 million ton unsinkable aircraft carriers immune to 1000kg bombs:

http://en.wikipedia.org/wiki/Project_Habakkuk

I've always assumed this gave Iain Banks the idea for the aerial battles fought over gigantic icebergs in Use of Weapons.

I think the issue here is the material being workable for a ship. The Titanic carried hundreds of people and tonnes of cargo.

The density of the material would have to make up for the weight it was carrying, plus any water it was liable to take on in case of an accident.

The entire volume of the ship (ie, the hull, the compartments, containers, etc) must have an overall lesser density than salt water. Having a less-dense hull is not enough.

I have a minor quibble with this article. We have a pretty good reason why they didn't either extend the watertight compartments or use a double hull in the construction.

Extending the watertight compartments up into the ship makes passenger movement much harder; a killer for a ship built around luxury.

The double hull would have added a lot of weight to the ship. Titanic's sister ship Britannic required a bigger engine to maintain the same speed and was less economical as a result. Titanic was expected to perform weekly Atlantic crossing over a very long lifetime and the cost would have been substantial.

Baseline for me is, the Titanic was built in 1912 to the standards they had back then (afaik even the insufficient number of live boats was accepted then), SOLAS was aresult of that disaster.

Imagine the Costa Concordia would have been lost not at shore but at high sea, the same result.

What happened in both cases, or is currently happening, is a review design and operating guidelines, which is good. And double-hules are still not common place, even today.

And yes, after all it has been, is and will most likely be for quite a long time about the trade off between safety and profitability.

These guys tout an unsinkable sailboat. Boat inside a boat with foam in between. Apparently you can punch a big hole in it, flood the inner compartment and it will still be able to sail. I suppose if you snap off the keel then it could go upside down, which isn't very good to you even if it floated. So really "unsinkable" means more than the ability to float.

http://www.etapyachting.com/

Isn't a better question: Is it possible to build a ship that ensures passenger survival even if the boat is partially destroyed?

My best idea is to build your ship out of a dozen smaller ships and then tie them together.

Be careful they don't drag each other down if a number of them sink.

http://en.wikipedia.org/wiki/Boston_Whaler#Unsinkability

Boat != Ship

The Titanic wasn't the largest ship ever built. It had a sister ship that was built earlier and of the same size. About two weeks after Titanic was built, an even larger ship was constructed.

Wouldn't it be cheaper to focus on emergency failsafe devices or similar safety solutions to those incorporated by modern aircraft?

Examples include:

-Self-righting mechanisms

-Self-sealing compartmental design

-Re-floating devices

-"Carefree" fly-by-wire preventing dangerous manoeuvering

All of these already exist in some form:

> Self-righting mechanisms

Modern ships can easily transfer ballast fluids (typically sea water, but sometimes fuel or distilate water) to correct any listing. There are no methods of righting an overturned ship because that would require an astronomical amount of moment.

> Self-sealing compartmental design

Watertight doors can be controlled from multiple stations on the ship, such as the bridge or the engineering control room.

> Re-floating devices

If you mean safety devices: Ships carry liferafts that, in the event of sinking, automatically detach from the ship, float to the surface, and inflate. If you mean re-floating the entire ship: Not feasible to re-float something that weighs hundreds of thousands of tons just to save some scrap steel.

> "Carefree" fly-by-wire preventing dangerous manoeuvering

Ships have automatic navigation and piloting, though not in shallower waters such as in ports.

I'm not reinventing the wheel here, or suggesting anything new - just that focusing on improving these would be a better investment of resources than creating an unsinkable ship.

For example:

* How good are the systems that realise that ships need righting and transfer the ballast automatically before it overturns?

* Refloating may not be feasible once the ship is overturned, but by then it'll be too late. How about self-inflating bags that inflate as the ship starts to sink, buying valuable time for people to escape?

* Automatic navigation is one thing, but how can we improve it? Does it identify foreign objects above/below the waterline? Does it have stabilisation assistance? Does it pump ballast around to ensure the best possible handling under any condition?

Just because these things already exist doesn't mean they can't be improved. In some cases this could potentially be done relatively cheaply.

> "Carefree" fly-by-wire preventing dangerous manoeuvering

Note that this caused the crash Air France Flight 447 because it trained the pilot to react incorrectly (too aggressively) in an emergency.

Yes, it also almost caused a crash on the Eurofighter because the display pilot knew he could operate at a more aggressive envelope than the system would let him. I'd still wager it has saved more situations than it has caused, and even if it hasn't - surely that just means the software has to get better?

Sure it's possible, but is it economical?

Every person is only willing to pay so much for a ticket, you could make ships that couldn't be sunk but it would cost so much that it wouldn't be worth it.

Instead of making unsinkable ships, we put lifeboats on sinkable ships.

Exactly - these are pretty unsinkable, but not very comfortable for a cruise - https://en.wikipedia.org/wiki/Tamar_class_lifeboat

tldr: "The short answer is no."

http://en.wikipedia.org/wiki/Betteridge%27s_Law_of_Headlines

Maybe, but probably not a ship that carries 1000 passengers, 1 million barrels of oil, fish, bring iPads from China or whatever ships are generally built for. So the answer for the real world is probably not.

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