British divers make contact with missing Thai football team • Hacker News Board

Re: British divers make contact with missing Thai football team

#101

Post by scarejunba » Tue, Jul 03, 2018, 4:38 PM UTC

jdietrich wrote: post #45

cimmanom wrote: post #15

Assuming the divers will have to shuttle supplies to the trapped team: is there a way to make repeated dives less risky, such as stringing a guide line that divers can follow?

Guide lines are absolutely essential in cave diving. At almost any point in a cave dive, there's a risk of disturbing silt and losing visibility. Cave divers have developed a sophisticated set of tools and techniques for navigating in conditions of low or zero visibility. Many underwater cave entrances are marked with a stark warning sign bearing an image of the grim reaper, imploring the diver to "prevent your death…

Top quality video. Thanks for sharing, man.

Re: British divers make contact with missing Thai football team

#102

Post by ahelwer » Tue, Jul 03, 2018, 4:45 PM UTC

fabricexpert wrote: post #96

SagelyGuru wrote: post #64

Earlier quoted context omitted.

I assume it was his decision to take all those children down there, so it was not beyond his control. Did he at least check the weather forecast? If my comment was designed to provoke, then it was to provoke people to think. We need to be able to think for ourselves sometimes. I actually find your comment somewhat unhelpful and grating. It is all very well everyone being a hero and never admitting to any wrong decisi…

Your idea of learning from this is to say "What was he thinking?", which in your context is is a rhetorical question. You're not trying to understand the thought process, instead you're making a statement to imply that the leader wasn't thinking about the group's safety when taking them into the cave and is negligent. This may or may not be true, or could be somewhere in between. But it specifically does not, and act…

Blaming the system works in urban environments or corporate engineering processes. Vast swathes of the world have no "system" to protect you, except for maybe a sign if sufficiently many people have died from a hazard and somebody cared enough to make one (and overcame pushback about disturbing the environment). Examples of such environments include backcountry travel, rural living (even in developed countries), and most certainly caving.

Re: British divers make contact with missing Thai football team

#103

Post by Someone » Tue, Jul 03, 2018, 4:59 PM UTC

PeterisP wrote: post #100

cm2187 wrote: post #69

Earlier quoted context omitted.

What I don't understand is that surely there must be a wide enough passage for them to have got in in the first place. It may be flooded but if one can walk into them vertically, surely they should be fairly accessible to a diver horizontally. Can't they just follow / be attached to a string or something like that?

It's a 2.5 km (a bit less than 2 miles) underwater swim. Right now they've been without food for 10 days and are barely able to stand. At the moment they wouldn't be able to walk the distance, much less spend many hours (it was about four hours for the experienced divers, so more for the boys) swimming underwater in unpredictable currents with no visibility due to silt, so if they get confused and let go of the strin…

”only accompany them behind them”

I think they would have them tied to a rope between divers, so that one of them can pull (gently, in narrow areas) and the other can guide the package to prevent it from scratching the rocks.

Re: British divers make contact with missing Thai football team

#104

Post by bitL » Tue, Jul 03, 2018, 4:59 PM UTC

CydeWeys wrote: post #94

cm2187 wrote: post #69

Earlier quoted context omitted.

What I don't understand is that surely there must be a wide enough passage for them to have got in in the first place. It may be flooded but if one can walk into them vertically, surely they should be fairly accessible to a diver horizontally. Can't they just follow / be attached to a string or something like that?

It's not logically following to me that just because it's easy to walk through a place it must necessarily be easy to dive through it. Diving is always significantly harder (you're wearing bulkier equipment for starters). It costs more energy to swim through water than it does to walk through air, the water has currents which you have to fight against, and the waters are murky so you have to go slow and can easily ge…

You have those small engines/jets/scooters for divers, so exhaustion from swimming should not be a problem, right? They also can place long glowing ropes in murky water; it's been done all the time in caves (or bind them to scuba divers, one in front, one in the back of a group). Once those boys get proper proteins/water and wait for a day or two to recover, they should be able to work it out, unless rain picks up - they are old enough to be considered adults in some Asian cultures, perfect age for an adventure of lifetime. But then even their current position is under danger as it could be flooded further or if a large flash flood occurs, then all bets are off.

Re: British divers make contact with missing Thai football team

#105

Post by JshWright » Tue, Jul 03, 2018, 5:10 PM UTC

cellularmitosis wrote: post #91

elil17 wrote: post #86

I’m curious about why they aren’t using robotics to driver food - seems like it would be safer than having human divers go back and forth

I'd imagine the psychological relief of seeing a human being rather than a robot has a lot to do with it.

It has nothing to do with it... Robots are not an option because it's a zero visibility environment (cameras for remote operation are useless).

Re: British divers make contact with missing Thai football team

#106

Post by Sevrene » Tue, Jul 03, 2018, 5:10 PM UTC

bitL wrote: post #104

CydeWeys wrote: post #94

Earlier quoted context omitted.

It's not logically following to me that just because it's easy to walk through a place it must necessarily be easy to dive through it. Diving is always significantly harder (you're wearing bulkier equipment for starters). It costs more energy to swim through water than it does to walk through air, the water has currents which you have to fight against, and the waters are murky so you have to go slow and can easily ge…

You have those small engines/jets/scooters for divers, so exhaustion from swimming should not be a problem, right? They also can place long glowing ropes in murky water; it's been done all the time in caves (or bind them to scuba divers, one in front, one in the back of a group). Once those boys get proper proteins/water and wait for a day or two to recover, they should be able to work it out, unless rain picks up -…

I'm no expert but I don't believe those diving jets are going to help in such an environment because A) takes up space of which they most likely don't have and B) it kicks up a lot of silt and dirt, making visibility conditions terrible. This can make or break such a rescue attempt and be really dangerous even for a seasoned cave diver.

Re: British divers make contact with missing Thai football team

#107

Post by ergothus » Tue, Jul 03, 2018, 5:13 PM UTC

cm2187 wrote: post #69

A_Person wrote: post #62

Earlier quoted context omitted.

You can't be serious. Taking 13 people, with an absolute maximum of Open Water level training (if that), back out through hundreds (or thousands?) of meters of low or zero visibility diving, including (apparently) tight restrictions, without risking the lives of all concerned? Aint gonna happen - unless the water level drops to the point where they can just float back out.

What I don't understand is that surely there must be a wide enough passage for them to have got in in the first place. It may be flooded but if one can walk into them vertically, surely they should be fairly accessible to a diver horizontally. Can't they just follow / be attached to a string or something like that?

My wife and I were doing a dive under very controlled circumstances. My wife tried to swim through a circular opening wider than your outspread arms. She couldn't. Fighting panic (rule 2: dont panic!) She kept trying, growing ever more aware of being both underwater and underground.

Then our dive master reached out and pushed her down a foot, and suddenly her tank could clear the top. From her perspective she kept swimming lower, but that was counteracted by buoyancy and she couldn't tell, with every failed attempt reducing her mental capacity to figure it out.

Fight or flight is not the reflex we need in diving, but it is the reflex we have.

Re: British divers make contact with missing Thai football team

#108

Post by Filligree » Tue, Jul 03, 2018, 5:23 PM UTC

SagelyGuru wrote: post #76

danilocesar wrote: post #74

Earlier quoted context omitted.

"learn to swim and dive right down there or die." It's quite common to see non-drivers saying this kind of non-sense. I have more than 150 dives and even with wreck training and experience I would never, never, never do cave diving. It's ridiculous dangerous, even for experienced cave divers. Without visibility and training, people die. Experienced cave divers get panic attacks and die. It's hard to control someone d…

You are right of course and that is why I said they will still be very lucky to get out alive. They don't even know how to swim and must be quite weak already. Somehow I do not see keeping them there till September, with water levels possibly rising further, as much of an option either.

The water levels might not rise further, and there's also the drilling option. There's even a chance that the water will recede enough to walk out; the weather report for the next week or two has ~no rain.

It's far too early to assume that only the most dangerous option is an option at all.

Re: British divers make contact with missing Thai football team

#109

Post by cma » Tue, Jul 03, 2018, 5:33 PM UTC

JshWright wrote: post #60

icebraining wrote: post #52

Earlier quoted context omitted.

By robot I meant remote controlled, not self-driving. But fair point - adding another obstacle would be tragic, yes.

The situational awareness of an ROV operator (who can only get visual feedback (in very low visibility conditions) is far lower than a diver (Who can feel their way along). Way too easy for an ROV (which has to tow along a tether) to get itself tangled somewhere.

Is sonar an option at the kind of scales involved?

Re: British divers make contact with missing Thai football team

#110

Post by streety » Tue, Jul 03, 2018, 5:44 PM UTC

jarvist wrote: post #35

mehrdadn wrote: post #18

How does cave oxygen supply work? Would they not run out of oxygen by the time they can get out? Also, one detail that CNN got that I didn't see in this article: it seems the cave is one kilometer underground ! [1] EDIT 1: The CNN article partially answers my first question: "Rescuers will also pump air into the cave to improve conditions." EDIT 2: Another important bit here [2]: "It won't be anything like diving tha…

There's usually plenty of air underground in a cave. They are actively being weathered / formed by little streams, which drag down air with them, forming a natural circulating draft. So even though the human-sized exit is flooded, there are likely to be multiple small inlets + cracks in the rock. The situation is very different in an (artificial) mine, which often have a single entrance/exit and no flowing water, so…

Do you have a link where I could learn more about that "Lazy Boy Sump Mapper"? I've found several mentions of its use, but would be interested in more technical information.