[PSUBS-MAILIST] onboard gear

Tue Apr 23 19:38:43 EDT 2019

A compact bail out rebreather might be the most surviveable solution however it would require a significant commitment in training, maintenance as well as the cost of the equipment itself. I personally have not been following the development of bailout rebreathers, although i'm aware that some are working on this. My dive group relies on planning for open circuit bailout in the event of rebreather failure. 

If money is no object, I am partial to the ISC Megalodon classic CCR. In terms of robustness and deep water capability,  you will find none better. 

It will get you home and flies itself. It is an electronic CCR which maintains PPO2 for the user. This is the unit I dive myself and feel very confident in. 

KISS classics, which are a simple and reliable mechanical CCR apparatus, often come up on the used market in affordable price ranges. 

Both would require significant equipment specific training but would get you out of a 400 ft jam with only two small cylinders and gas to spare. CCR duration is driven by metabolic rate and is the same irrespective of operational depth. Even the lowest end units will give you an hour plus. 

On ascent, rebreathers do require the diver to be monitoring the oxygen level display in the breathing loop and very likely adding oxygen manually - particularly in the mCCR type on a fast ascent.

The other benefit of this setup is that an air cell for buoyancy can be integrated easily in one compact package. 

It sounds like a lot of effort for the non diver, but it is a functional answer to the risks of a sub disabled in deep water. 

What is a life worth? 

How much risk can one accept for a hobby? 

Food for thought anyhow. 

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On Tue, Apr 23, 2019 at 7:34 PM -0400, "Alan via Personal_Submersibles" <personal_submersibles at psubs.org> wrote:

As an alternative to possible death or even worse, the loss of your submarine,I am in early stages of designing a buoy release mechanism that is usedfor surfacing safely but has an emergency beacon that can be activated with an electro magnet.Thoughts are to use 150 lb braid with a tensioning mechanism & have anautomatic boat latch mechanism that can slide down the braid but is fixedto the buoy with instructions, "tie a long rope to the ring & let down untilllatch attaches to submarine. Pull up"The automatic latch is a device that Phil described & provided a drawing for,but there may be a cheap & suitable automatic boat latch ( used on release& retrieve on boat launching) on the market. I am still searching & if anyoneknows of one that may be suitable I would be interested.Alan
On 24/04/2019, at 10:51 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

There is a significant difference between submarine escape and a planned SCUBA dive with regard to both the dive profile and the equipment that you can reasonably carry.  An escape is more akin to what is known as a buoyant emergency ascent in recreational diving, where you need to get to the surface yesterday and all other considerations are secondary.  In this specific case, trying to keep to a slow ascent rate would significantly increase the incurred decompression obligation that you must necessarily then blow off as you ascend through the shallows, introducing an even greater risk.  You also have the hypothermia issue to deal with if you are not equipped with exposure protection specifically intended for submersion at depth. Being cold reduces decompression effectiveness. In order to keep to a target ascent rate or perform decompression stops, you would need diving instrumentation (depth gauge and timer), would need the skills and experience to perform gas switches and hold stops, and would need significantly more bulky equipment to have enough gas to perform a proper decompression (slow ascent, gas switches, etc.).

When I dive to these depths on SCUBA, I wear twin cylinders (>100 cu. ft. each) on my back with the bottom gas (10/70 or whatever for the planned depth and time), plus three or four off-board cylinders (80s) carrying the decompression gases (typically 21/35, 35/25, EAN50 and oxygen), plus a small bottle of argon for drysuit inflation.  Obviously, as an escapee you are not so equipped.  Far better to lockout as quickly as possible and rapidly ascend (with buoyant assist) to get clear of those depths where you are ongassing the most, and if at all possible, to slow the ascent as you approach the surface, and then have your surface support or emergency responders administer oxygen as transport is arranged to recompression.  To be clear, an emergency escape from a disabled submarine at these depths is not even remotely a good idea - it is simply a marginally better idea than dying on the bottom.

To illustrate, if you were to attempt a continuous ascent from 300 fsw, the average depth is 150 fsw, which is about 5.5 atmospheres absolute.  If you assume a surface air consumption rate of 1 cu. ft. / minute (high, but typical of a diver who is stressed or working hard, which is inevitable in a submarine escape scenario), that corresponds to 5.5 cu. ft. / min at the average depth of the ascent.  At a 30 ft/min ascent rate, that's 10 minutes, or 55 cu. ft. of gas consumed just for the continuous ascent with no decompression stops, without consideration for the gas consumed while blowing down and locking out.  You can judge for yourself the practicality of carrying an 80 on a PSub sized vessel just for emergency escape purposes.

Sean

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
 On Tuesday, April 23, 2019 12:32 PM, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Guys, This topic is fascinating and scary at the same time. Accent rates form the old Navy logs had 60ft / minute max with a recommended max accent rate of 30 ft/ min. At 300ft escape depth, what volume of mixed gases would you need for a 10 minute accent assuming you choose not to swim 60ft/min.

Best Regards,
David Colombo

804 College Ave
Santa Rosa, CA. 95404
(707) 536-1424
www.SeaQuestor.com

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Personal_Submersibles at psubs.org
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As an alternative to possible death or even worse, the loss of your submarine,
I am in early stages of designing a buoy release mechanism that is used
for surfacing safely but has an emergency beacon that can be activated 
with an electro magnet.
Thoughts are to use 150 lb braid with a tensioning mechanism & have an
automatic boat latch mechanism that can slide down the braid but is fixed
to the buoy with instructions, "tie a long rope to the ring & let down untill
latch attaches to submarine. Pull up"
The automatic latch is a device that Phil described & provided a drawing for,
but there may be a cheap & suitable automatic boat latch ( used on release
& retrieve on boat launching) on the market. I am still searching & if anyone
knows of one that may be suitable I would be interested.
Alan

> On 24/04/2019, at 10:51 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> There is a significant difference between submarine escape and a planned SCUBA dive with regard to both the dive profile and the equipment that you can reasonably carry.  An escape is more akin to what is known as a buoyant emergency ascent in recreational diving, where you need to get to the surface yesterday and all other considerations are secondary.  In this specific case, trying to keep to a slow ascent rate would significantly increase the incurred decompression obligation that you must necessarily then blow off as you ascend through the shallows, introducing an even greater risk.  You also have the hypothermia issue to deal with if you are not equipped with exposure protection specifically intended for submersion at depth. Being cold reduces decompression effectiveness. In order to keep to a target ascent rate or perform decompression stops, you would need diving instrumentation (depth gauge and timer), would need the skills and experience to perform gas switches and hold stops, and would need significantly more bulky equipment to have enough gas to perform a proper decompression (slow ascent, gas switches, etc.).
> 
> When I dive to these depths on SCUBA, I wear twin cylinders (>100 cu. ft. each) on my back with the bottom gas (10/70 or whatever for the planned depth and time), plus three or four off-board cylinders (80s) carrying the decompression gases (typically 21/35, 35/25, EAN50 and oxygen), plus a small bottle of argon for drysuit inflation.  Obviously, as an escapee you are not so equipped.  Far better to lockout as quickly as possible and rapidly ascend (with buoyant assist) to get clear of those depths where you are ongassing the most, and if at all possible, to slow the ascent as you approach the surface, and then have your surface support or emergency responders administer oxygen as transport is arranged to recompression.  To be clear, an emergency escape from a disabled submarine at these depths is not even remotely a good idea - it is simply a marginally better idea than dying on the bottom.
> 
> 
> 
> To illustrate, if you were to attempt a continuous ascent from 300 fsw, the average depth is 150 fsw, which is about 5.5 atmospheres absolute.  If you assume a surface air consumption rate of 1 cu. ft. / minute (high, but typical of a diver who is stressed or working hard, which is inevitable in a submarine escape scenario), that corresponds to 5.5 cu. ft. / min at the average depth of the ascent.  At a 30 ft/min ascent rate, that's 10 minutes, or 55 cu. ft. of gas consumed just for the continuous ascent with no decompression stops, without consideration for the gas consumed while blowing down and locking out.  You can judge for yourself the practicality of carrying an 80 on a PSub sized vessel just for emergency escape purposes.
> 
> Sean
> 
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>> On Tuesday, April 23, 2019 12:32 PM, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> 
>> Hi Guys, This topic is fascinating and scary at the same time. Accent rates form the old Navy logs had 60ft / minute max with a recommended max accent rate of 30 ft/ min. At 300ft escape depth, what volume of mixed gases would you need for a 10 minute accent assuming you choose not to swim 60ft/min.
>> 
>> Best Regards,
>> David Colombo
>> 
>> 804 College Ave
>> Santa Rosa, CA. 95404
>> (707) 536-1424
>> www.SeaQuestor.com
> 
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
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