3 ms·

Interesting, I don't see any "first principles" reason why this couldn't be done, except for some bend radius that might be just too tight [0]. Also the pipe wo

Interesting, I don't see any "first principles" reason why this couldn't be done, except for some bend radius that might be just too tight [0]. Also the pipe would have to be made of something more solid than rubber to overcome the water pressure (it's not much but it's still there). From a risk management point of view however this solution seems a bit reckless, as a rescuer you never want to cause more damage/hazard than what's already present and this untested solution could fail in some catastrophic ways. What to do if the pipe becomes punctured? How do you rescue somebody that becomes stuck for whatever reason? (think also psychological factors) If you compare this to just waiting a few months and walking out you might conclude that it's not worth the risk. https://www.theguardian.com/world/ng-interactive/2018/jul/03/thailand-cave-rescue-where-were-the-boys-found-and-how-can-they-be-rescued https://www.theguardian.com/world/ng-interactive/2018/jul/03...

eesmith 8y ago
Such a pipe would have to be placed with water inside, then pumped out once its installed. Why? Because it takes a lot of force to put an air-filled tube through water. I see no way that such a pipe could be deployed. Even without buoyancy issues, there will be a lot of friction from the cave walls, and going around bends. The force can't come from simply pushing it it, as anything flexible enough to bend around curves will also crumble from the pushing force. If I read it right, the pipe would need to be 6 meters deep in some points in the cave. As you might recall from Star Trek IV The Voyage Home, the transparent aluminum scene, the whale tank needed 6" of Plexiglass. If I use the "Aquarium Thickness Calculator (xls)" from http://www.sdplastics.com/aquaria1.html http://www.sdplastics.com/aquaria1.html and plug in 200 inches (for about 6 meters), then it says it would need 16 inches of Plexiglass. You might shave that down, with better materials that don't need to be clear, but, as The Guardian points out elsewhere, there isn't much room: "Parts of the cave system are reportedly so narrow that Thai Seal teams and the volunteer rescue divers had to remove their own breathing apparatus to get through" Furthermore: "It’s about 11 hours – six on the way from the entrance to where the kids are and five on the way back" Who will guide the pipe at it goes through the route? Once the pipe has gone through one of those constrictions, can anyone else get by? If the pipe blocks the route, then what? And, how long would it take to lay such a pipe?
- simon_acca 8y ago
  To eliminate some of the raised issues, particularly around the forces acting during the installation, the conduit could be assembled from sections, in the guise of HVAC ventilation shafts[0]. With that said, I won't add any further speculation since mechanical/materials engineering is really not my area of expertise. Someone knowledgeable could provide insight on: what material (steel?) is suitable for such a task and what are processes for watertight bonding performed underwater (welding?). 0: https://bigreddog.com/wp-content/uploads/2016/02/Ductwork-1-1-768x337.jpg https://bigreddog.com/wp-content/uploads/2016/02/Ductwork-1-...
  - eesmith 8y ago
    There is no need for a materials engineer. We can look to existing structures which hold water to get an idea. Above ground pools use 1/8" steel for about 1-1.5 meters of water depth. (Eg, https://www.answers.com/Q/How_thick_is_a_swimming_pool https://www.answers.com/Q/How_thick_is_a_swimming_pool ) Pressure is linear with depth, so 6 meters would require about 1/2" of steel. HVAC ducts like you pointed to are about 1/40". (Based on numbers I see at https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/Chapter%206_Duct%20Systems.pdf https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/... ).
    - simon_acca 8y ago
      I just pointed at hvac ducts to illustrate the kind of tech I was referring to (pipes assembled from small sections), wasn’t suggesting that actual hvac pipes should be used
      - eesmith 8y ago
        Ahh, I see. I misunderstood. Your model, I think, is that the divers would lay at least 1km of 1/2" thick steel pipe, from the far end backwards (since otherwise there's no way to get the segments to the end). Call it 1cm for easy of calculation. Steel is 8g/cubic centimeter. Assuming the divers can carry 20kg (which seems large), each segment is at most 25 cm long. That's at least 4,000 segments, each to be welded. Assuming it takes 5 minutes per weld, that's 13 days of non-stop work. And I am assuming that the welding equipment doesn't need to be moved in. As Johnny555 pointed out elsewhere in these threads, the divers are having problems putting in a communications cable, which is much smaller and more flexible.

eesmith 8y ago

Such a pipe would have to be placed with water inside, then pumped out once its installed. Why? Because it takes a lot of force to put an air-filled tube through water. I see no way that such a pipe could be deployed. Even without buoyancy issues, there will be a lot of friction from the cave walls, and going around bends. The force can't come from simply pushing it it, as anything flexible enough to bend around curves will also crumble from the pushing force. If I read it right, the pipe would need to be 6 meters deep in some points in the cave. As you might recall from Star Trek IV The Voyage Home, the transparent aluminum scene, the whale tank needed 6" of Plexiglass. If I use the "Aquarium Thickness Calculator (xls)" from http://www.sdplastics.com/aquaria1.html http://www.sdplastics.com/aquaria1.html and plug in 200 inches (for about 6 meters), then it says it would need 16 inches of Plexiglass. You might shave that down, with better materials that don't need to be clear, but, as The Guardian points out elsewhere, there isn't much room: "Parts of the cave system are reportedly so narrow that Thai Seal teams and the volunteer rescue divers had to remove their own breathing apparatus to get through" Furthermore: "It’s about 11 hours – six on the way from the entrance to where the kids are and five on the way back" Who will guide the pipe at it goes through the route? Once the pipe has gone through one of those constrictions, can anyone else get by? If the pipe blocks the route, then what? And, how long would it take to lay such a pipe?

simon_acca 8y ago
To eliminate some of the raised issues, particularly around the forces acting during the installation, the conduit could be assembled from sections, in the guise of HVAC ventilation shafts[0]. With that said, I won't add any further speculation since mechanical/materials engineering is really not my area of expertise. Someone knowledgeable could provide insight on: what material (steel?) is suitable for such a task and what are processes for watertight bonding performed underwater (welding?). 0: https://bigreddog.com/wp-content/uploads/2016/02/Ductwork-1-1-768x337.jpg https://bigreddog.com/wp-content/uploads/2016/02/Ductwork-1-...
- eesmith 8y ago
  There is no need for a materials engineer. We can look to existing structures which hold water to get an idea. Above ground pools use 1/8" steel for about 1-1.5 meters of water depth. (Eg, https://www.answers.com/Q/How_thick_is_a_swimming_pool https://www.answers.com/Q/How_thick_is_a_swimming_pool ) Pressure is linear with depth, so 6 meters would require about 1/2" of steel. HVAC ducts like you pointed to are about 1/40". (Based on numbers I see at https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/Chapter%206_Duct%20Systems.pdf https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/... ).
  - simon_acca 8y ago
    I just pointed at hvac ducts to illustrate the kind of tech I was referring to (pipes assembled from small sections), wasn’t suggesting that actual hvac pipes should be used
    - eesmith 8y ago
      Ahh, I see. I misunderstood. Your model, I think, is that the divers would lay at least 1km of 1/2" thick steel pipe, from the far end backwards (since otherwise there's no way to get the segments to the end). Call it 1cm for easy of calculation. Steel is 8g/cubic centimeter. Assuming the divers can carry 20kg (which seems large), each segment is at most 25 cm long. That's at least 4,000 segments, each to be welded. Assuming it takes 5 minutes per weld, that's 13 days of non-stop work. And I am assuming that the welding equipment doesn't need to be moved in. As Johnny555 pointed out elsewhere in these threads, the divers are having problems putting in a communications cable, which is much smaller and more flexible.