Debris found came from missing Titan sub, says friend of passengers • Hacker News Board

Re: Debris found came from missing Titan sub, says friend of passengers

#581

Post by dragonwriter » Thu, Jun 22, 2023, 10:43 PM UTC

throw310822 wrote: post #558

Hamuko wrote: post #231

Earlier quoted context omitted.

He seemed especially proud about combining titanium and carbon fibre against the advice of others, which seems to now have been in a pretty active role in the demise of the Titan. > "I'd like to be remembered as an innovator. I think it was General MacArthur who said "you're remembered for the rules you break." And I've broken some rules to make this. I think I've broken them with logic and good engineering behind me…

I'm curious about this detail, and I have what is surely a very dumb question. Both titanium and carbon fiber are, afaik, known and used for their strength to weight ratio; so aerospace is a natural application. But in deep sea diving is weight a factor at all? Could one just build vehicles with, I don't know, a 30 cm thick steel plate?

> But in deep sea diving is weight a factor at all?

You need to be able to attain both positive and negative buoyancy, which constrains density within a range, right? That limits design choices like “giant block of steel with a tiny passenger cavity”.

Re: Debris found came from missing Titan sub, says friend of passengers

#582

Post by ikiris » Thu, Jun 22, 2023, 10:44 PM UTC

tptacek wrote: post #414

dpedu wrote: post #351

Earlier quoted context omitted.

You're in luck, the Mythbusters tried this: https://www.youtube.com/watch?v=LEY3fN4N3D8

... and that was like, a couple hundred feet. The Titanic is at 12,500 feet. An unfathomable amount of pressure.

objection, that is clearly 2083 1/3 fathoms of pressure.

Re: Debris found came from missing Titan sub, says friend of passengers

#583

Post by jb12 » Thu, Jun 22, 2023, 10:49 PM UTC

hawk_ wrote: post #364

jb12 wrote: post #326

Earlier quoted context omitted.

What's your definition of reckless? Were the boys stuck in the cave in Thailand reckless? Should we not have rescued them? Where is the line of who is deserving of our sympathy?

The grown ups involved in that who didn't pay heed to warnings would be reckless. We still rescue them but we can charge those who can pay for it.

And the 19 year old who didn't want to go on the submarine but wanted to spend time with his dad? Was he reckless? Was he worth searching for?

Re: Debris found came from missing Titan sub, says friend of passengers

#584

Post by Tuna-Fish » Thu, Jun 22, 2023, 10:51 PM UTC

tptacek wrote: post #350

dmonitor wrote: post #337

Earlier quoted context omitted.

would they be vaporized or instantly compacted? my morbid curiosity kind of wants to see what would happen to a body under such insane pressure conditions.

As I understand it: the pressure vessel was full of air, and at the moment it failed, that air-filled space became the equivalent of the cylinder of a 2-stroke engine, instantly heating as the air compressed.

Correct. Except it is heated to a much, much higher temperature.

Re: Debris found came from missing Titan sub, says friend of passengers

#585

Post by Kailhus » Thu, Jun 22, 2023, 10:53 PM UTC

cowmoo728 wrote: post #501

gamblor956 wrote: post #484

Earlier quoted context omitted.

Aircraft grade aluminum is 2024 or 7075, not 6061, because those alloys are more resistant to fatigue from repeated pressurization cycles. 6061 is more commonly used in automotives than in aircraft.

the comment above you is correct that consumer goods will often brag about "aircraft grade" when referring to 6061. like flashlights, tools, combs, pens, cufflinks, money clips, etc.

This made me realise how little I know about alumiunium and made me summarise this from a quick wiki search:

- “2024 aluminium alloy is an aluminium alloy, with copper as the primary alloying element. It is used in applications requiring high strength to weight ratio, as well as good fatigue resistance. It is weldable only through friction welding, and has average machinability.

- “7075 aluminium alloy is an aluminium alloy with zinc as the primary alloying element. It has excellent mechanical properties and exhibits good ductility, high strength, toughness, and good resistance to fatigue. It is more susceptible to embrittlement than many other aluminium alloys because of microsegregation, but has significantly better corrosion resistance than the alloys from the 2000 series.”

- “6061 is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. It has good mechanical properties, exhibits good weldability, and is very commonly extruded. It is one of the most common alloys of aluminium for general-purpose us.”

Re: Debris found came from missing Titan sub, says friend of passengers

#586

Post by krisoft » Thu, Jun 22, 2023, 10:53 PM UTC

nicce wrote: post #481

crazygringo wrote: post #394

Earlier quoted context omitted.

Can you expand? To a layman like myself, tracking is part of communications and it seemed clear there was no tracking because they didn't know where the sub was. What is the specific type of tracking device you're referring to? What signals does it emit? And if overall power was lost, for example, why wouldn't the tracking stop just like communications stopped?

Both will be lost at the same time. We don't really know such signal. Submarines cannot communicate more hundred meters in the bottom of sea. Sea water absorbs the signal quite well. When the signal is lost, the expectation is that the submarine is under the water. https://en.wikipedia.org/wiki/Communication_with_submarines

> Submarines cannot communicate more hundred meters in the bottom of sea.

Sorry if I am misunderstanding you. It sounds like you are saying that it is impossible to design a system which would be able to keep in contact with the submarine/submersible all the way down to the bottom?

Because if that is what you are saying that is simply false. We have the technology to keep in contact with a submarine all the way to the bottom of even the deepest oceans.

This is not even speculative. We know it is possible because James Cameron had full communication during his dive all the way to the deepest point on earth. Here is a really cool article about the technical challenges with that system: https://www.hydro-international.com/content/article/communic...

Re: Debris found came from missing Titan sub, says friend of passengers

#587

Post by CydeWeys » Thu, Jun 22, 2023, 10:57 PM UTC

tromp wrote: post #388

Hamuko wrote: post #231

Earlier quoted context omitted.

He seemed especially proud about combining titanium and carbon fibre against the advice of others, which seems to now have been in a pretty active role in the demise of the Titan. > "I'd like to be remembered as an innovator. I think it was General MacArthur who said "you're remembered for the rules you break." And I've broken some rules to make this. I think I've broken them with logic and good engineering behind me…

Serotta did too when making this bike: https://www.bigshark.com/articles/serotta-road-bikes-pg318.h...

Bicycles are not submersibles.

Re: Debris found came from missing Titan sub, says friend of passengers

#588

Post by lamontcg » Thu, Jun 22, 2023, 10:58 PM UTC

gdubs wrote: post #510

TrackerFF wrote: post #452

Earlier quoted context omitted.

At that depth, the pressure is quite intense - around 6000 psi. That means 6000 pounds pr square inch - that's almost a Ford F150 truck pr square inch, everywhere. And now imagine how many square inches the surface area of a human is - especially your upper torso where your lungs are located. The sub (hull) is made of a carbon fiber and titanium mix - and I'm not sure how that would react, if it buckles / collapses l…

What if the impassion happened higher towards the surface, like, 2000 feet?

A 10 psi pressure wave can kill you instantly, which is just 22 feet of pressure under the surface. At any depth that a pressure vessel can rupture and implode spontaneously, it will just crush any humans within it.

Re: Debris found came from missing Titan sub, says friend of passengers

#589

Post by inferiorhuman » Thu, Jun 22, 2023, 10:59 PM UTC

raldi wrote: post #472

hawk_ wrote: post #456

Earlier quoted context omitted.

Which of the victims asked those planes to be sent their way?

I'm not sure what you're trying to say.

You're comparing a terrorist attack (9/11) to reckless malfeasance (this sub). The more apt comparison would be of 9/11 to the Andriana disaster. It's a bit ridiculous to champion the humanitarian benefits of sending a throng of people to look for a handful of people in a very unusual situation while ignoring the larger humanitarian disaster that is far more likely to happen again (ergo far more important to practice for).

And, yes, it's a zero sum game. People looking for the five rich guys are people that cannot look for the hundreds of children trapped on a sinking ship.

Re: Debris found came from missing Titan sub, says friend of passengers

#590

Post by robomartin » Thu, Jun 22, 2023, 11:00 PM UTC

Philip-J-Fry wrote: post #513

itake wrote: post #457

Earlier quoted context omitted.

Do you have any details about why it was a death trap? I watched one video that complained about off the shelf parts being used, but the two examples was an RV light (not safety related) and the gaming controller (which they had multiple back ups). They also claimed to have been reviewed by Boeing and University of Washington. There was 7 different mechanisms that could force a return. Some of those were purely mecha…

Using off the shelf components is probably the best thing they did. You don't want to reinvent the wheel if you can help it. I don't know why the game controller is a sticking point for most of social media. It's funny to think of a vehicle being piloted by one, but they really are designed to be used for thousands of hours. Game controllers have been used in all sorts of military applications. The issue as far as I…

> Using off the shelf components is probably the best thing they did

No. Not really. It's a horrible idea. It's irresponsible. It's negligent.

Consumer grade components are not designed for the kind of reliability and failure tolerance requirements these kinds of applications have to face every mission. A simple example of this would be no conformal coating anywhere to prevent failures due to condensation on the circuit board. Also, tin whiskers due to RoHS solder. No redundancy or failure tolerance in any portion of the design. It isn't enough to say "we have extra game controllers". That's not how you build reliable failure-tolerant systems where people's lives depend on things working perfectly 99.9999% of the time.

Also, it is a fallacy to say that millions of people use these controllers. The most obvious problem with this statement is that we have zero data on failure rates and failure modes. And, of course, nobody dies. As a parallel example, you would be hard-pressed to find toy controllers on medical equipment, even in situations where there might be time to deal with failures.

> the hull was made of carbon fibre In the sub world that tried and true method is just thick steel.

Yup. Fundamental principle: Carbon fiber is best used under tension, not compression. Not a good choice for a life-support compartment under incredible external pressure. One way I think of it is: In compression you are mostly relying on the epoxy to keep things together. Without epoxy carbon fiber will support as much compression as a common string. Zero.