Request for accuracy for a film...

[pbnj]

The submersible they're escaping from is actually just a supply module rated for extreme pressure, but not life support. It itself is something they escape to when their research sub fails. Pressure on the hull is no problem, but there needs to be a point at which they are forced to bail on it and head for the surface alone. The crux is figuring out a daunting depth to do that from, even if it takes a little MacGuyver-ing.

---------- Post added May 5th, 2015 at 08:24 PM ----------

If you want a dramatic illustration of what happens.... kill someone. have a character die in an accident. An embolism will make it pretty clear what you don't want to have happen. air at 10 atm is one tenth the volume of what it would be at the surface a liter of air will compressed to 10 atm will expand to 10 liters at the surface. if you fail to vent that from your chest.... well, lets just say drowning will not be your big problem.

But does catching air from a submersible pressurised at 1 ATM in something like a Steinke hood help at all even if you're bailing at 15 ATM and making a quick ascent?

 

[DBF]

Hi pbnj
What you describe in post 7 is what is taught to military submariners. I have done it from 30m and known of others that have done it from 100m. No ill effects except from a adrenaline rush and lunched clean out of the water.

Do a YouTube search on submarine escape training tower to see it happen
30m takes about 10 seconds
Training to do this is quite quick


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[pbnj]

Hi pbnj
What you describe in post 7 is what is taught to military submariners. I have done it from 30m and known of others that have done it from 100m. No ill effects except from a adrenaline rush and lunched clean out of the water.

Do a YouTube search on submarine escape training tower to see it happen
30m takes about 10 seconds
Training to do this is quite quick


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Is that a 10 second ascent aided by by external buoyancy, or just a man, his lungs and a controlled breath out?

The final ascent should be tense, and the audience would probably look for inhuman breath holding for that. But l can explain the pressure effect on lungs and get tension from a 30-60 second ascent.

I'm not adverse to requiring decompression on the surface, so long as they can have a minute or two relief before having to enter a chamber.

 

[DBF]

There is some buoyancy as the escapees are wearing an exposure suit similar to a dry suit and have a hood over their head that traps air.

I have seen it done in the training tower from 30m only wearing a pair of speedos by the trainers with no problems much slower.
I believe one of the trainers was going to try 100m. Just after I discharge. Never herd what happened so I assume he survived


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[pbnj]

Okay, here's where I'm at:

The submersible is completely out of life support. It was never built for it, it's a slow ascent and now they're getting into territory where CO2 will start impeding their decision making.

They have no choice but to exit at somewhere between 300-500ft (the deeper the better) and make a short swim for a nearby wet bell, where they know is at least one buoyancy compensator they can use to make the rest of the ascent faster.

They make their improvised thermal suits to alleviate at least some of the cold, flood the whole submersible, take their breath, exit and head for the bell.

Once at the bell, they are mindblown at just how much worse that short swim was than they thought it would be. They don't think they can make it, but they have no choice. There's no contact with the surface, the bell is cut off and they are already assumed dead. Nobody is looking for them.

They put on their suit or buoyancy compensator (with or without a hood of trapped air, but preferably not), then just go for it.

It takes them 30-60 seconds to surface (the longer the better), and it was sheer torture. But they made it.

Then they either need tank time or not, but they get that minute or two of sheer adrenaline-fuelled relief.

Would any of this immediately be 'Busted' on an episode of Mythbusters, or could it at least fall under 'Plausible'?

How low could I start at to give me that longer final ascent? Real time. They'll probably stretch the screen time to 2-3 minutes anyway. Or do you think I could even push the depth lower to ratchet up the tension while staying outside of hopeless odds?

I shouldn't have even said 50/50 odds. 60/40, 70/30, as long as it's not hopeless and downright impossible.

 

[CT-Rich]

Submarine Escape Immersion Equipment - Wikipedia, the free encyclopedia
This is the current state of the art, or so Wikipedia says. Which is rated to 600 fsw. Just for clarification, if you trap air at 1 atm and immediately go to 15 atm, the air will instantly compress to 15 atm. the practical effect is that a dry suit will lose all its volume, 6 liters of air (about 1.5 gallons) will become 400 ml (less than 1 pint), your lungs would probably collapse in an irreversible way. Even more importantly a traditional dry suit would collapse onto you like shrink wrap on a ding-dong, rendering you completely paralyzed. The rapid implosion of your eardrums will prevent you from hearing your own scream of agony (but with no air in your lungs, I wouldn't worry about screaming anyway). If escaping from a sub isn't the main plot issue is should be, because you are more likely to survive a high speed car chase in that doing a blow and go from 600 fsw. Interestingly, if you start at depth and breath out you can actually make it to the surface on one breath (although, there is going to be the greates volume change closer to the surface.)

 

[DBF]

Just had some info sent to me by a mate.

Brits did an escape in 1970 from a keel depth of 600 ft. With a survival suit and no chamber ride

See Submarine Escape and Rescue





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[emoreira]

In this famous movie The Abyss (1989) - IMDb, a similar scene is shown.
Another source of information about submarine escapes is in the Sealab book from Ben Hellwarth.

 

[danvolker]

In the absence of a lock, would flooding the whole submersible work if you were to capture air in an improvised hood first?

And if you were to go from a submersible at 1 ATM to 15 ATM outside and then to a bell pressurised at depth (maybe a little higher up at 10 ATM), stop for a few minutes to refill your hood and then go for the surface - would that stop in the bell and its He content really throw you off?

My thought was to stop at the bell, despite the risks, to retrieve life jackets to make the rest of the ascent faster. Or is this way off base?

And here's one that is completely Hollywood:

Would referring to PSI instead of ATM underwater be just absurd? It would be an embellishment for drama, because the more dramatic jump in numbers between atmospheres is easier for the average joe to derive tension from. Going from 220 PSI to 14 PSI sounds more dramatic than going from 15 ATM to 1 ATM.

Thanks again, guys - this is unbelievably helpful.

If the submersible begins to flood, lets water in, and air is compressed by the water entering, then you can have a pressurized submersible at that point, though there is a much reduced area your heroes are within....
If they are going to make a mad dash to the surface after the stop at the bell, or if they are going straight to the surface from the flooded submersible, you absolutely do NOT want them on a Helium mix ..You want them breathing air.....If they were breathing a helium mix, they could not surface quickly...if breathing air, it does not supersaturate anywhere near as easily as trimix ( supersaturate equals fizzing) , and a 300 foot per minute ascent could easily be survivable from the submersible--little time for nitrogen saturation, which is why freedivers can do a drop to 300 or 400 feet and not get bent.
.
The smart way up without fins, is probably to have some kind of upside down bag full of air, held by a rope, that will act as a float to drag them to the surface rapidly.
For this reason, I'd pass on the bell, and go straight for the surface the moment I could get into the water.....even a 400 foot per minute ascent, with ascent occurring immediately, could be survivable as long as they exhaled all the way up ( and did not have asthma)....Some individuals might get bent if they had a PFO or bad genetics....most should be just fine. I would assume no oxygen will be available on the surface---though that would be ideal if possible, to mitigate any possible dcs , until a chamber ride was possible.

They do need a mask to make it feasible...though someone with skills could do it without a mask....and you probably could MacGyver a Dry suit with the material you suggested--with lots of warm clothes inside for insulation, as long as the escapees know that without an OPV valve, they will have to dump air out of suit sleeves or neck area as they ascend.....some place that can not be held by duct tape, but must be elastic to allow for the dumping and sealing.

 

[CT-Rich]

Okay, here's where I'm at:

The submersible is completely out of life support. It was never built for it, it's a slow ascent and now they're getting into territory where CO2 will start impeding their decision making.

They have no choice but to exit at somewhere between 300-500ft (the deeper the better) and make a short swim for a nearby wet bell, where they know is at least one buoyancy compensator they can use to make the rest of the ascent faster.

They make their improvised thermal suits to alleviate at least some of the cold, flood the whole submersible, take their breath, exit and head for the bell.

Once at the bell, they are mindblown at just how much worse that short swim was than they thought it would be. They don't think they can make it, but they have no choice. There's no contact with the surface, the bell is cut off and they are already assumed dead. Nobody is looking for them.

They put on their suit or buoyancy compensator (with or without a hood of trapped air, but preferably not), then just go for it.

It takes them 30-60 seconds to surface (the longer the better), and it was sheer torture. But they made it.

Then they either need tank time or not, but they get that minute or two of sheer adrenaline-fuelled relief.

Would any of this immediately be 'Busted' on an episode of Mythbusters, or could it at least fall under 'Plausible'?

How low could I start at to give me that longer final ascent? Real time. They'll probably stretch the screen time to 2-3 minutes anyway. Or do you think I could even push the depth lower to ratchet up the tension while staying outside of hopeless odds?

I shouldn't have even said 50/50 odds. 60/40, 70/30, as long as it's not hopeless and downright impossible.

Thermal protection is the least of their problems. Even if they breath air in the bell for just a couple of minutes to catch their breath and get rid of CO2, they will be hitting the surface bent, possibly (more like probably) fatally. swimming to the surface you are talking about a CO2 saturated body, needing 30 feet per minute, hell double that It would be worth the risk to cut a 300 fsw ascent from ten minutes down to 5. You are still talking about FIVE minutes. 100 fsw is do able, I bet it has been done from 150. I would look for a technical fix inside the sub and skip the free ascent. By the way, a buoyancy compensator is not a parachute for scuba divers, its to maintain trim underwater (correct depth/ body position). Buoyant ascents of any type from 300+ are best done if your primary interest is in providing your nest of kin with a body to bury. Free divers do it because they are taking advantage of the mammalian diving reflex and are not going to be breathing going down or back. Even then, it is a high risk sport.