Questions from 3A.M.

[Gryphon_Man]

It is nearly 3A.M. as I write this, just after finals week as ended. I've realized I need more stimulation than just video games. A few questions will have to do. I'm not sure I'm in the right place, but as there is no thread for stupid 3 in the morning questions, I'm gonna put these here.

1. Oxygen supply using electrolysis. It seems possible to produce oxygen and hydrogen from just zapping water, I've even read people using both together for deep diving, could that be used for regular diving?

2. How much air do people use diving, google seems to think we breath 7-8 litters per minute, does that number hold true under water? does the mammalian diving reflex come into play?

3. How long as anyone stayed under for, I don't see an obvious reason why we could stay under forever, provided we had air.

4. Can you eat/drink underwater.

 

[Danseur]

1. The amount of energy needed is absolutely huge. No practical way to make one sufficiently powerful enough which is also compact enough for personal use.

2. Relative to pressure, workload, and stress, yes. Mamalian diving reflex, not so much. Best we can do is put our face in the water at rest on the surface and spend 3-5 minutes just breathing at rest. Lower heart rate and reduces stress.

3. There are different records, all eclipsing a full day. Are we talking Scuba, CCR, or in a Habitat? Do air pockets count?

4. Yes. Capri Sun pouches are a favorite. Chewing is harder because we can't breathe through our noses. Food better done in a bell or habitat.

Get some rest and dream of your favorite dive.

 

[atdotde]

2. this value is determined by your metabolism. The breathing is controlled by the build up of carbon dioxide in your blood, so you cannot lower the rate (in gas volume per minute) by increasing the amount of oxygen.

3. Capri sun or camel back. It’s much harder to drink from a Glas bottle since there you have to replace the consumed volume (probably with water).

 

[Akimbo]

FYI: Nuclear submarines generate Oxygen through electrolysis, but are not energy limited. It is more weight, volume, and cost effective to store oxygen than the energy to generate Oxygen through electrolysis -- with current technology and under practical constraints of Scuba divers.

 

[KevinNM]

Iirc, the problem with oxy-hydrogen as a breathing gas is that it’s flammable until you get quite deep. I forget the depth, but it is well below recreational depths. Then as you as dive and ascend you need to switch to and away from a highly flammable mixture.

 

[Gryphon_Man]

Iirc, the problem with oxy-hydrogen as a breathing gas is that it’s flammable until you get quite deep. I forget the depth, but it is well below recreational depths. Then as you as dive and ascend you need to switch to and away from a highly flammable mixture.

How much of a concern is fire underwater? It seems pretty safe.

 

[atdotde]

No, you definitely don't want your breathing apparatus burning, in particular since there are high pressures around that can cause quite impressive explosions.

 

[Akimbo]

Hydrox (Hydrogen-Oxygen) breathing mixtures are used for very deep saturation dives, typically below about 1.400'/425M.
Oxygen percentages are considerably under 1% in order to maintain a safe PPO2, typically 0.3-0.5. Hydrox is not explosive or flammable at such low O2 levels. The reason for Hydrox is to reduce gas density/breathing resistance below Heliox or HeO2.

 

[Bob DBF]

FYI: Nuclear submarines generate Oxygen through electrolysis, but are not energy limited. It is more weight, volume, and cost effective to store oxygen than the energy to generate Oxygen through electrolysis -- with current technology and under practical constraints of Scuba divers.

And occasionally there is an explosion and associated shrapnel, it is known as the bomb.


Bob

 

[KevinNM]

No, you definitely don't want your breathing apparatus burning, in particular since there are high pressures around that can cause quite impressive explosions.

Burning your lungs has potential issues too. Most people use them fairly often. So filling them with a burning gas seems rather undesirable. IIRC some flammable mixtures of oxygen and X stop being flammable when the O2 percentage drops below 10%. Hydrogen will burn in quite a bit lower oxygen concentrations.