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

bbc.com

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

#811

Post by sparky_z »

AYBABTME wrote: post #802
adql wrote: post #631

Earlier quoted context omitted.

Your intuition is spot on, carbon fiber is much better at tensile loads than compressive loads. Tensile load capacity is pretty much the resin that keeps the fibers from moving. The most I could find about the design > The entire pressure vessel is comprised of two titanium hemispheres, two matching titanium interface rings, and the 142 cm (56") internal diameter, 2.4-m (100") long carbon fiber wound cylinder – the l…

Aren't most/all materials much stronger in tensile load than compressive loads, because of buckling anomalies?

No, brittle materials like concrete are famously weak in tension and strong in compression. Ductile materials are generally equally strong in both. I can't think of any material offhand that's stronger in tension and weaker in compression.

Buckling is not a material failure, it's a structural failure. In pure buckling [0], the strength of the material is not actually a factor in whether something buckles or not. In most cases, material failure does occur as a side effect of the buckling, but not always. (The material's stiffness does matter, though. All else equal, something that's more flexible will buckle sooner than something stiff.)

[0] https://en.wikipedia.org/wiki/Euler%27s_critical_load

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

#812

Post by somenameforme »

pests wrote: post #622
helios_invictus wrote: post #285

Earlier quoted context omitted.

They do, but not the depths we're talking about (12,500 feet) https://navalpost.com/how-deep-can-a-submarine-dive/ The depth limits of the most known nuclear powered submarines’ depth limits, as follows; Typhoon-class: Test depth 900 m (3,000 ft) Astute-class: Over 300 m (984 ft 3 in) Akula-class: 480 m (1,570 ft) test depth for Akula I and Akula I Improved, 520 m (1,710 ft) for Akula II and III, 600 m (2,000 ft) max…

Wow these numbers blow my mind. I imagined much deeper but some of these seem literally just below the surface.

Not sure why somebody downvoted this. 'Just below the surface' is an odd phrasing, but I had the exact same sort of initial reaction as I think anybody would. The numbers are just so shocking here. The 'average' military sub isn't fit for travel much beyond 300 meters. The peak theoretic technology has subs that may be about to travel to around the 2000 meter mark.

The Titanic is at 3800 meters. That it's reachable, by private organizations no less, is just a marvel.

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

#813

Post by timthelion »

AYBABTME wrote: post #802
adql wrote: post #631

Earlier quoted context omitted.

Your intuition is spot on, carbon fiber is much better at tensile loads than compressive loads. Tensile load capacity is pretty much the resin that keeps the fibers from moving. The most I could find about the design > The entire pressure vessel is comprised of two titanium hemispheres, two matching titanium interface rings, and the 142 cm (56") internal diameter, 2.4-m (100") long carbon fiber wound cylinder – the l…

Aren't most/all materials much stronger in tensile load than compressive loads, because of buckling anomalies?

No, concrete and bricks are much stronger in compressive loads.

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

#814

Post by s1artibartfast »

MisterBastahrd wrote: post #756
hahajk wrote: post #703

Earlier quoted context omitted.

There's a difference between knowing that a certain number of people are statistically dying right now vs knowing that 5 specific people are currently dying in a specific way.

Most of the people getting shot in mass shootings aren't doing something stupid on purpose.

Most of the people shot in Mass shootings (by the definition) are doing something stupid,specifically drug dealing and gang warfare. Very boring stuff

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

#815

Post by kelthan »

lsh123 wrote: post #767
carabiner wrote: post #708

Earlier quoted context omitted.

Just fucking insane. In aerospace everyone knows that when a crack starts, IT'S OVER. Crack propagation is extremely rapid after that once nucleation has occurred. Your only hope is to prevent nucleation sites in the first place. Except it's extremely hard to characterize fatigue limits without tons of testing and even for metals there is wide variation for identical parts, not even getting into composites. Which of…

Not quite true. Stop drilling is commonly used on airplanes: http://o-si-sec.com/2018/10/11/5-facts-to-know-about-stop-dr...

Air pressure decreases as you go up at a far lower rate than water pressure increases as you go down. Air pressure at 30K feet is ~0.3 Bar compared to 1.0 Bar at sea level.

Water pressure increases by 1 Bar every 32ft (10m) of depth. To see the equivalent change in pressure in water (0.6 bar) as you see going up to 30K in the air, you only have to go down ~20ft (6m). The pressure on the submersible at 9000ft (2750m) is 276 Bar.

F16s and other planes with composite body panels will sometimes lose a panel due to water buildup between layers of the composite. The water freezes between the layers popping the panel loose from the frame or retainers holding it in place. That is usually not a life-threatening problem (though not desirable). A crack in a submersible pressure vessel at more than a couple hundred feet is usually fatal.

The description of the Byford Dolphin accident in ~300ft (~90m) of water or 9 Bar pressure, is illustrative: https://www.iflscience.com/byford-dolphin-accident-how-livin...

The pressure on the Titan would have been ~30 times greater than what occurred on the Dolphin.

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

#816

Post by ta8903 »

richk449 wrote: post #770
kortilla wrote: post #764

Earlier quoted context omitted.

“Mass shootings”, as in the people who were shot had mass. Redefining mass shootings to conveniently include gang violence really dilutes the term to meaninglessness.

Why is it not a mass shooting if a gang is involved?

Don't know why, but people just don't take gang violence seriously in America.

I've been in lots of discussions about gun violence, but I've never seen someone argue for reducing gang crime, even though they cause a majority of the gun deaths.

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

#817

Post by bobbylarrybobby »

sparky_z wrote: post #811
AYBABTME wrote: post #802

Earlier quoted context omitted.

Aren't most/all materials much stronger in tensile load than compressive loads, because of buckling anomalies?

No, brittle materials like concrete are famously weak in tension and strong in compression. Ductile materials are generally equally strong in both. I can't think of any material offhand that's stronger in tension and weaker in compression. Buckling is not a material failure, it's a structural failure. In pure buckling [0], the strength of the material is not actually a factor in whether something buckles or not. In m…

I believe wood is stronger in tension than it is in compression?

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

#818

Post by snek_case »

activiation wrote: post #463

I'm surprised millionaires/billionaires didn't do better research on that company before going on the trip

I'm looking at this and wondering why anyone would risk their life for an extremely dangerous trip in a cramped underwater vessel with no toilet when you could just... send a drone.

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

#819

Post by somenameforme »

WalterBright wrote: post #722
jacquesm wrote: post #440

Earlier quoted context omitted.

It's an interesting question. (One of very few on this subject that are really interesting.) Those who cause progress to happen to some extent have to have something in them that causes them to ignore conventional wisdom. Because they're swimming against the current. And if they succeed it may well pay off, both in credits and financially. Montgolfier brothers, Lilienthal, the Wright brothers and so on, and that's ju…

> Every one of them went against conventional wisdom and the laws of physics as they were known or suspected to be at the time. This is not true of the Wrights. Their first step was to gather together all the known aeronautical knowledge at the time. They relied on them, too, until they discovered the coefficient of lift was off by a factor of two. Then they built their own wind tunnel to determine the correct value.…

Correcting knowing knowledge always comes with the chance that what you're observing may be invalid for reasons you aren't considering. So in this regard you're largely agreeing with the post you're ostensibly arguing against. Everybody else says e.g. the coefficient of lift is x, I say it's y - is not just a "discovery", but going against the conventional knowledge of laws of physics of a given time.

It's not like the aviation enthusiasts prior to the Wright Bros were just strapping aluminum sheeting to their backs and jumping off cliffs. Well I mean maybe somebody somewhere at some time did do that, but for the most part people always try to start from a basis of what's known, and work their way up from toy experiments. Same with this story, or even the 'flat earth guy' who was launching himself in rockets. [1] For those who didn't 'get it', the flat earth stuff was just an overtly transparent schtick for interest/funding.

[1] - https://en.wikipedia.org/wiki/Mike_Hughes_(daredevil)

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

#820

Post by jnsaff2 »

jtriangle wrote: post #706
failuser wrote: post #635

Earlier quoted context omitted.

Russia has a Losharik nuclear submarine that was tested up to 2500m (8200ft) if Wikipedia is to be believed. It got in the news when it had a fire that killed half a dozen decorated officers. USA probably has something similar.

No doubt, depth capability is one of the big features you go after when building a combat submarine. The deeper you go, the faster you can go while retaining stealth (cavitation is the limiting factor which decreases with the added hydrostatic pressure), and, if you can go significantly deeper than your adversaries, you're more or less invulnerable to attack because they can't shoot at you. That's also why military s…

Wouldn’t drag increase with the pressure?
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