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Why isn't Titan classed? (2019)

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Re: Why isn't Titan classed? (2019)

#291

Post by phkahler »

flaminHotSpeedo wrote: post #274
phkahler wrote: post #162

Earlier quoted context omitted.

If I recall correctly, even NASA found unit testing to be of limited value, finding a small fraction of software bugs. That's not to say "don't do it" but my stance is that the developer should do some ad-hoc testing for everything they write, just don't formalize and document it or you'll land on the wrong end of cost/benefit. I can point to some subtle logic bugs that no sane unit test would have caught.

"even NASA" implies that NASA is the objective paragon of software development. There are many ways to develop software, and while I have never worked for NASA I can virtually guarantee that their development process is not the same as some random web service. I've found that it's better to think of unit tests as a contract. You don't write them to check your code for bugs, you write them to declare an explicit (thou…

>> "even NASA" implies that NASA is the objective paragon of software development.

Sure. They have some of the highest costs of failure post-deployment of anyone, and they have some solid development practices. I'll cite NASA in this context any time. Feel free to pull in other sources if you don't like them though.

Re: Why isn't Titan classed? (2019)

#292

Post by mustacheemperor »

dm319 wrote: post #288
mustacheemperor wrote: post #176

Earlier quoted context omitted.

It seems they felt this was one of the novel innovations that enabled this design - that the monitoring system was so good, they'd never be at risk in the pressure hull at depth. James Cameron said it looks like they had dropped their emergency ascent ballast before the implosion, so they may have gotten enough warning to take action. But I would guess that system was never tested to failure in real life. It will be…

Do you know in what way it was 'acoustic'? I.e. was it listening for sounds, or was it more like sonar?

I looked over the patent yesterday, I think someone linked it in this thread. It would “listen” for the sounds of impending structural failure, by comparing the sounds in the hull to a dataset of previous test dives. One of the passengers on Titan’s 2nd dive said it made cracking and popping noises as it got deeper but the patent intended to detect a change in acoustics (in conjunction with stress sensors) far enough in advance for corrective action.

Re: Why isn't Titan classed? (2019)

#293

Post by gerdesj »

elcomet wrote: post #278
gerdesj wrote: post #234

Earlier quoted context omitted.

You guys are tall ship masters. Your vessels are generally well understood these days but let's not forget some comparable disasters: Vasa and Mary Rose. Yes both are from a long time ago but both were based on top of a lot of good solid engineering but both pushed the envelope somewhat and perished. Vasa design basically forgot to sort out the various CoGs for a ship - it was top heavy. Mary Rose loss is a bit more…

> It isn't the same as running up Everest or going into space. Deep sea is way, way more dangerous That doesn't seem right to me. Deep sea and space seem equally dangerous

Space has different issues but basically -1 atmosphere vs 180 atmospheres is a constant. 180 atmospheres is absolutely brutal.

Without any real justification, I invite you to imagine an elephant pirouetting on top of your skull. Hmmm, nice image, does it stack up:

180 atmos is 186 kg/cm^2 according to random online calculator. That's 2645 psi in old money, according to Google calc. An adult african elephant is about 5-6 tonnes according to several sites (max 6.8 tonnes). So 6000/186 = 32 cm^2. root 32 is about 5.7cm. I really did pluck the elephant thing out of the air and it does seem to work out (please check my 'rithmetic).

Imagine that every 5.7cm^2 of your body/vessel/submarine has an adult african elephant's weight bearing on it.

Now in space we have a bit of a problem with keeping everything in, instead of out but we can lower the internal atmospheric pressure and up the oxygen content (fire risk - procedures!) and other tricks and we have to scrub the CO2 (and so below surface). We also have to worry about very, very fast moving anything, radiation and other issues.

But in space you do not have an elephant's weight crushing each 2.5" square of your body, all the time! That's why deep sea is far more dangerous than space (which is also very dangerous).

Re: Why isn't Titan classed? (2019)

#294

Post by gerdesj »

bradknowles wrote: post #279
gerdesj wrote: post #234

Earlier quoted context omitted.

You guys are tall ship masters. Your vessels are generally well understood these days but let's not forget some comparable disasters: Vasa and Mary Rose. Yes both are from a long time ago but both were based on top of a lot of good solid engineering but both pushed the envelope somewhat and perished. Vasa design basically forgot to sort out the various CoGs for a ship - it was top heavy. Mary Rose loss is a bit more…

With respect, the "DevOps attitude" is not "move fast and break things". That's the Facebook attitude. DevOps is, in part, about using repeatable methods of automation and extensive testing throughout the software development lifecycle to try and make sure that the software you deliver in production will do exactly what it should do and nothing else, and so long as it is properly designed, should be able to withstand…

Soz mate, I was a little enthusiastic in making my point and I picked on an easy target. I'm well aware how DevOps works.

Re: Why isn't Titan classed? (2019)

#295

Post by marcosdumay »

johnwalkr wrote: post #284
marcosdumay wrote: post #255

Earlier quoted context omitted.

From the design they published of it, I do really think they intended to have the carbon fiber tensioned between a pair of titanium rings. I understand epoxy doesn't deal well with that, but with the right plastic, I believe it could work very well.

That would only be possible if the rings were fixed relative to each other, which they are not.

Yeah, you are right. It's not tensioned between the rings then.

Re: Why isn't Titan classed? (2019)

#296

Post by ummonk »

adamjgs wrote: post #219
ummonk wrote: post #93

Earlier quoted context omitted.

The epoxy in carbon fiber makes it stiff. Stiffness helps reduce buckling loads.

The buckling load is the load at which a structure buckles. I think you mean that stiffness helps resist buckling.

Err yeah I mean that stiffness reduces the internal stress caused by external compression force. Stiffness increases the buckling load of a material.

Re: Why isn't Titan classed? (2019)

#297

Post by int_19h »

cbzoiav wrote: post #270
ineedasername wrote: post #177

Earlier quoted context omitted.

>Whether it can do it reliably / survive fatigue accross repeated cycles is a different question. Imagine we'll find out as the investigation progresses. Seems like we already found out the answer is “no”. The overall ship design failed.

The ship failed. What we don't know yet is whether the carbon fiber hull is why.

All evidence so far points at implosion, which is kinda by definition a hull failure.

Re: Why isn't Titan classed? (2019)

#298

Post by scarnie »

“OceanGate’s submersibles are the only known vessels to use real-time (RTM) hull health monitoring. With this RTM system, we can determine if the hull is compromised well before situations become life-threatening, and safely return to the surface. This innovative safety system is not currently covered by any classing agency.”

That is going to come back and bite them.

Re: Why isn't Titan classed? (2019)

#299

Post by efraim »

stickfigure wrote: post #202
wkat4242 wrote: post #133

Earlier quoted context omitted.

It also wasn't built with parts from camper world and cheap Xbox controller knockoffs. NASA actually had a strong focus on safety. They just went about it the wrong way, calculating safety ratings backwards. Considering the pressure vessel of this sub was only meant to handle 1300m as per another article, the way it survived 50 dives at 4000m is pretty amazing though.

> this sub was only meant to handle 1300m There seems to be a lot of confusion around this, let me try to clear it up. The 1300m limit of the glass number comes from an interview with the "whistleblower" in 2018. That would mean it refers to the Cyclops 1 vehicle they had then. A couple years later they built the Cyclops 2, which has the 5" thick hull, titanium bells, and first dove in 2021. That's the ill-fated Tita…

The report by the whistleblower David Lochridge is specifically about Cyclops 2, also called Titan, and the quality control of the carbon fiber cylinder. It also mentions the viewport only being certified to 1300 meters. Some of it can be read in the lawsuit that came from Oceangate firing David.

https://storage.courtlistener.com/recap/gov.uscourts.wawd.26...

Re: Why isn't Titan classed? (2019)

#300

Post by Ajedi32 »

gerdesj wrote: post #293
elcomet wrote: post #278

Earlier quoted context omitted.

> It isn't the same as running up Everest or going into space. Deep sea is way, way more dangerous That doesn't seem right to me. Deep sea and space seem equally dangerous

Space has different issues but basically -1 atmosphere vs 180 atmospheres is a constant. 180 atmospheres is absolutely brutal. Without any real justification, I invite you to imagine an elephant pirouetting on top of your skull. Hmmm, nice image, does it stack up: 180 atmos is 186 kg/cm^2 according to random online calculator. That's 2645 psi in old money, according to Google calc. An adult african elephant is about…

With current technology the most dangerous part about space isn't being in space, it's getting there (and back). So far, nobody has ever died just sitting in orbit. (Closest was the Soyuz 11[1] and even that was a result of an incident during the re-entry process.)

[1]: https://en.wikipedia.org/wiki/Soyuz_11#Re-entry_and_death

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