Optimal Pony Bottle Size for Failure at 100ft?

[MarkA]

With all the joviality that the last seven pages have engendered, I thought I'd actually go back and read the whole thread!
And to my pleasant surprise, there were lots of proponents of 19, 13 and even 6 CF pony's, early in the thread. Cool!
Just for fun, I plugged in my own SAC, assumed that I wouldn't freak out much, but gave myself 15 seconds to make the switch before I started up. Damned if even a 6 wouldn't get me out of 130 feet!
View attachment 879432
I'm not kidding. The doubles, or AL40 that you left at home is clearly inferior to the 6, 13 or 19 that you threw in your carry-on and filled with @Couv 's portable transfil adapter in your resort room.

Maybe the thought process is different depending on how you get to your diving. The difference between flying to holiday diving compared to driving with your own cylinders to go diving.

Driving would allow the smallish twinset or larger pony cylinder for diving in the 30 to 40m range.

 

[Celt]

FWIW, we are talking about an ascent on a pony after a failure or out of gas on a single tank rig. Not a CESA.

At least that's what we started with. At this point? ¯\_(ツ)_/

From 100 feet 2 breaths is plenty.

 

[OMyMyOHellYes]

Dude, just STOP with the 1 minute stops thing already.

If you feel that you have to stop every 3m/10' , just a 10 second pause absolutely ensures that you can't be exceeding 60' per minute even if you are teleporting between stops.

Interesting question that brings.

On Star Trek, the crew usually always used the transporter on and off the Enterprise. They also seemed to ignore the varying mass of the planetary bodies onto which they transported, or more to the point, the gravitational effect of the planetary mass.

Now, if they were on a giant planet for a few days, and their musculature and skeleton could handle it somehow, the atmosphere would also likely be much much higher pressure than that onboard. How did they not get bent coming back up? Or did the transporter matrix, at an atomic particulate level, screen for and purge excess nitrogen before the re-materialization phase?

Same when transporting to much lower mass planetoids, but in reverse.

 

[OMyMyOHellYes]

Interesting question that brings.

On Star Trek, the crew usually always used the transporter on and off the Enterprise. They also seemed to ignore the varying mass of the planetary bodies onto which they transported, or more to the point, the gravitational effect of the planetary mass.

Now, if they were on a giant planet for a few days, and their musculature and skeleton could handle it somehow, the atmosphere would also likely be much much higher pressure than that onboard. How did they not get bent coming back up? Or did the transporter matrix, at an atomic particulate level, screen for and purge excess nitrogen before the re-materialization phase?

Same when transporting to much lower mass planetoids, but in reverse.

So to extend that even further, if the transporter is actually eliminating the nitrogen load prior to the re-materialization phase, why wouldn't they just transport directly from depth in an OOA emergency?

Also could we use transporter technology to make hyperbaric chambers obsolete? From first surfacing, just transport a bent diver and drop him right back on the deck, not bent.

 

[Tigerpaw]

Transporter compensates for it, just like the bio filters takes out any pathogens.
Scotty is the BEST hands down, nuff said!!!

 

[rjack321]

This is ridiculous! The calculations are simply WRONG. You forgot the 3 minutes on the bottom that are required to free yourself from fishing line, nets and fight off a Kraken or two.

As someone who was attacked by a Kraken (large giant pacific octopus on my head) I can say the buoyancy goes to sh*t and gas consumption is off the charts, although it's hard to distinguish how much is from breathing and how much is from the Octo pushing on the purge button.

This was at Sares Head wall off Fidalgo Island for the locals.

 

[SpaceX Aquanaut]

Dude, just STOP with the 1 minute stops thing already.

Novice divers are not taught to dive that way, so it is objectvely irrelevant to gas calculations for them.

I'll admit it is an "interesting" ascent methodology. But other than ensuring that you can't be ascending too fast, it seems worse than any normal strategy in: deep nitrogen loading, air consumption (just plain getting to the surface), SS & shallow SLOW ascent "reserve", and consequence of secondary failure.

If you feel that you have to stop every 3m/10' , just a 10 second pause absolutely ensures that you can't be exceeding 60' per minute even if you are teleporting between stops.

Alright, spoon-fed for ya: 100fsw, with 1 minute to problem solve, and then 30fpm to 20fsw for a three minute “safety stop” (because you don’t want deep nitrogen loading, and want a shallow SLOW ascent reserve -etc etc and so forth -whatever), and given a stressed RMV of 1 cubic feet per minute:

4.0 ATA x 1min x 1 cf/min = 4 cf

3.7 ATA x 0.3 min x 1 cf/min= 1.1 cf

3.4 ATA x 0.3 min x 1 cf/min = 1.0 cf

3.1 ATA x 0.3 min x 1 cf/min = .93 cf

2.8 ATA x 0.3 min x 1 cf/min= .84 cf

2.5 ATA x 0.3 min x 1 cf/min = .75 cf

2.2 ATA x 0.3 min x 1 cf/min = .66 cf

1.9 ATA x 0.3 min x 1 cf/min= .57 cf

1.6 ATA x 3min x 1 cf/min= 4.8 cf


Total cubic feet: 14.65 cf for one diver.


Total MGR backgas volume for 2 Divers: 14.65 x 2 = 29.3 cf ~round it to 30 cf

An AL40 pony as the OP figured & chose to use will cover this entire scenario with plenty of margin, bringing the solo diver after the 3min Safety Stop (or longer), the final 20fsw to surface.

Happy, Happy now

Couldn’t objectively figure it out for yourself -so you derisively dismiss something as simple as the above, as an irrelevant gas calculation . . . (actually it is quite vital to know for 30fpm ascent -same as 30 feet every 60 seconds; same as 10 feet every 20 seconds or same as 1 foot/2 seconds continuous ascent rate -or just easier to hold 10 seconds, and move 10 seconds to avoid “teleportation” between stops).

 

[-JD-]

Alright, spoon-fed for ya: 100fsw, with 1 minute to problem solve, and then 30fpm to 20fsw for a three minute “safety stop” (because you don’t want deep nitrogen loading, and want a shallow SLOW ascent reserve -etc etc and so forth -whatever), and given a stressed RMV of 1 cubic feet per minute:


An AL40 pony as the OP figured & chose to use will cover this entire scenario with plenty of margin, bringing the solo diver after the 3min Safety Stop (or longer), the final 20fsw to surface.

Happy, Happy now

Couldn’t objectively figure it out for yourself -so you derisively dismiss something as simple as the above, as an irrelevant gas calculation . . . (actually it is quite vital to know for 30fpm ascent -same as 30 feet every 60 seconds; same as 10 feet every 20 seconds or same as 1 foot/2 seconds continuous ascent rate -or just easier to hold 10 seconds, and move 10 seconds to avoid “teleportation” between stops).

I don't have an issue with that calculation. And I have figured out gas/ascent calculations for myself "longhand" and built my own spredsheet for fun to more easily play with different variations. I haven't needed much spoonfeeding for about 55 years, but of course things do have a way of coming around.

But that is NOT calculated with the parameters that you have been repeatedly discussing - that is moving the goalposts. The one minute STOP after ascent of EVERY 3m/10' was what I took issue with. The resulting average ascent rate is a quater of the generally-accepted, current "safe" ascent rate.
[I am pre-editing here to be thorough and point out that I went back and you did explain that your procedure is actually a one minute NET ascent and hold cycle which would result in a 10'/minute average ascent rate. You have repeatedly referred to one-minute stops in susequent posts and I believe that variability is significantly clouding the issue here (certainly for me.)]

In actual practice, it's an "ascent hold" at depth for 30sec -at each "triad" cardinal number depth by-threes in meters, or "decade" by-tens in US Imperial), and then "move up" to the next cardinal depth in 30sec.

So for example, stop at 36m/120' for 30 seconds, then move up to next depth of 33m/110' in 30 seconds; do a hold at 33m/110' for 30 seconds, then move to 30m/100' in 30 seconds; and so on etc.

And that IMO does make the resulting calculations irrelevant to novice divers who would reasonably be expected to ascend at the nominal 30'/minute rate they were trained to.



I actually find your methodolgy conceptually intriguing. It does bind the ascent into an arguably more controlled situation. I do find the length of those stops unnecessarily long at the expense of other important factors - boiled down: more time at depth, less available gas for the unexpected and time at more beneficial offgassing depths.

As I pointed out, a 10 second stop guarantees a maximum of 60'/minute rate. Even if you actually ascend (between stops) at 60'/minute, with the 10 second stop, your average ascent rate is only 30'/minute. And if you ascend (between stops) at 30'/minute your average ascent rate only falls to 20'/minute - a bit safer if you are concermed that 30' is too aggressive, but with far less negative impact (IMO). In other posts you have made much the same profile suggestion.

No . . . but IMHO better repeated pauses -under control- than constantly looking at your computer's ascent rate indicator all the way up from 130'/39m, making sure it reads no more than 30fpm (better to just stop and hold for 10 seconds, and then move up taking 10 seconds to ascend 10'/3m -->essentially again, an overall rate of 30fpm/9mpm. . .

[Reiterating: There seem to be several different intermixed profiles presented and this has been confusing (again - at least to me - sorry to the extent that my loss of context led to more critical tone. ) The coceptual ascent methodology is worth thoughtful discussion.]

 

[Diver-Drex]

@SpaceX Aquanaut
Doing the math isn’t the issue. That is not ascent strategy that makes sense to me or several others. That’s the issue.

You did you use the term ‘min deco’ somewhere in there. May I ask where you got this particular ascent strategy?

 

[steinbil]

As someone who was attacked by a Kraken (large giant pacific octopus on my head) I can say the buoyancy goes to sh*t and gas consumption is off the charts, although it's hard to distinguish how much is from breathing and how much is from the Octo pushing on the purge button.

This was at Sares Head wall off Fidalgo Island for the locals.

Wow. Talk about having an octo in the golden triangle...