large air bubble on a deep dive

[Bob DBF]

Actually, this raises an interesting question of locking into a submarine. Even at periscope depth that is still something like 60 feet below the surface to the hull where the escape trunk is. I'm not sure how fast they can pump out the trunk once closed, but it seems like something you would have to watch because you would be going from several atmospheres to one, which is ambient inside the boat. Do they have fine enough control over the pumping to account for deco?

No pumps, the water can be drained to the bilge. There are gauges, as I remember, that monitor both pressure and depth, so one can do a deco procedure if necessary. There is compressed air so one can drain the water while maintaining the pressure.

The sub I was on only had the emergency escape trunks, they were set up and could be used as wet or dry hyperbaric chambers that could be operated from the inside the trunk or the sub, but were rather small. The spook subs during my era had much greater capabilities to move men and equipment in and out easily. God knows what they can do today, pretty much the same thing only better.

 

[rongoodman]

See this was why I’d initially overlooked the pressure being equal. Thinking that sometimes there’s ways for fresh air to get in, what keeps the pressure high enough to keep the water out and equal to the water depth

If there was some way for air to get in there would be no reason for it to be there in the first place, as the water would just push it out through those same openings and fill the space. Domes such as the one mentioned in Palau or in the Mexican cenotes lie above water level.

 

[admikar]

True but the premise was an air pocket. We haven't even mentioned HPNS, compression arthralgia, or hypothermia yet.

@Powertrip see what you have started? (tongue in cheek comment, I see BoltSnap's comment the same)

 

[ABUnderwater]

This is just some further speculation on my part, but it seems that dive computers (at least the oceanics that I’ve used) only use the wet sensor to turn on, since they start to“end” the dive when you are within a meter or so of the surface and the computer is still wet. If they detect that pressure increases again before 10 mins, they resume the dive. If not, they totally end it and start counting the surface interval.

So, speculating based on that behavior, I’d bet that emerging in a pressurized pocket would still be interpreted as being at depth and diving even with a dry contact.

Of course, this is not in the manual - but it’s the behavior that makes sense based on how they operate.

Not to continue the tangent too much, but my understanding of the argument against pressurizing computers in air is that the pressure transducers are actually set in a gel that protects them from water damage. If pressurized in air, gas could penetrate into the gel and form bubbles in the gel matrix, which would totally change the transducer's response to pressure thereafter. Turns out your computer can get bent after all...

As an aside, I believe this is a problem that has been solved (at least for some computers?). Where I work, we take our computers down annually to 130' on a chamber ride just to check the accuracy of the sensors. We used to to do this with them in buckets of water, but since chatting with Shearwater support, we've been advised that they are perfectly able to handle air pressurization, so we did away with that water. We've had no issues.

 

[MrVegas]

For the OP -- you might find the diving history threads interesting.

 

[Lorenzoid]

I haven't read all the replies, but this sort of theoretical question gets discussed from time to time. Here are a couple of old threads I found:

Cave-diving and water pressure question

I'm trying to wrap my head around pressure experienced while in a cave. Now my confusion may be based on overly simplified information forming my base understanding. So first off here are my beginning thoughts: 1) Pressure is due to the amount of matter above you and the make-up of said...

scubaboard.com

inhaling/exhaling from underwater air pockets

in the scene from the Big Blue, where Enzo freedives into the flooded ship to save the scuba diver, had there been an air pocket in a compartment (say 5m deep), could the freediver rest in it & breathe, obviously exhaling it in bubbles on his way up? could the scuba diver he just rescued do the...

scubaboard.com

Fun stuff to ponder.

 

[vjb.knife1]

Commercial "deep sea divers" would work at that depth for days doing "saturation diving". They use hundreds of millions of dollars of equipment and have hundreds of people looking after them. They get paid a lot of money too and it takes a week to come to the surface after spending their two weeks at depth.

This is what I used to do in the 1970's and 80's. You have a bit of an exaggeration here especially the part about hundreds of people looking after them, try perhaps a dozen.

To the OP you should take a first year college level physics course.

 

[Akimbo]

Commercial "deep sea divers" would work at that depth for days doing "saturation diving". They use hundreds of millions of dollars of equipment and have hundreds of people looking after them. They get paid a lot of money too and it takes a week to come to the surface after spending their two weeks at depth.

You have a bit of an exaggeration here especially the part about hundreds of people looking after them, try perhaps a dozen.

Probably more like a dozen/shift today on a modern DSV (Diving Support Vessel), unless you are talking about one of the few small sat systems on drilling rigs that are still operating. I guess you could get to a hundred if you count the both shifts on larger 2-bell and 2-ROV DSVs. More than $200 Million is a stretch unless you count other non-exclusive support services like choppers, supply boats, and heavy-lift vessels, etc.

For other readers:

Info - What is Saturation Diving?

A lot of divers are not sure what Saturation diving is so I thought a quick summary might be useful. Saturation diving was developed by the US Navy's Captain George F. Bond (affectionately known as Papa Topside) in the 1960s. All divers know that the deeper we go and longer we stay, the longer...

scubaboard.com

 

[Wibble]

This is what I used to do in the 1970's and 80's. You have a bit of an exaggeration here especially the part about hundreds of people looking after them, try perhaps a dozen.

To the OP you should take a first year college level physics course.

Isn’t the ship dedicated to diving? Had included the ship's crew including all ancillary workers. If not hundreds it’s a lot

My source was The Last Breath. Needed that person to reboot the pee sea to get the dynamic positioning system back on line.

 

[vjb.knife1]

I never worked on a ship for Saturation jobs. The system was on a barge which was towed to the drill rigs where we worked. I worked on a flat deck work boat with a surface deco lock on bell system in shallower water with shorter duration work. Still either one of the diving operations may have had 40 to 50 people on board but they also did other work, welding, machinist, pipe fitters, etc. But then that was a long time ago and regulations require different procedures and support personnel. Now I work with a crew of three other divers / mechanics on a Submarine in scuba gear and shallow water. It is a lot simpler, safer and easier.