Just to clear up; the last paragraph above was not referring to work done while on the saturation mission. That would have been very dangerous (even deadly). One does not approach the surface while saturated. Decompression for 24 hours or even longer is mandatory.
mipsman
A diver on surface air is not sucking though as hose. The air is either being pumped down to him, or he is being given a gas mixture from a pressure tank [think of a topside SCUBA tank]. To get the air down to him, it has to be at a sightly higher pressure than the water pressure at his depth. The differential pressure across his chest is more or less the same as at the surface. Of course, there are still demand valves so that air is pumped in when he tries to breath. This keeps you from blowing up his lungs.
The diver does not need the pressure suit. The old fashioned ones you are thinking about were designed that way so they could have a place to seal the helmet. The new ones can seal to his face, they to not have to seal to a suit which then blows up like a balloon. That pressurized suit makes it harder for the diver to bend his arms and legs, and so makes it harder to do useful work.
No nitrogen in the lungs/bloodstream equals no nitrogen narcosis, AND no inconvenient “bends.” You can just pop up like a little cork.
Lordy me, DON’T DO IT!! <grin>
Oxy-helium does indeed avoid nitrogen narcosis but, if anything, it increases the danger of the bends. The “bends” is caused by the decrease in solubility of gases in your body as the pressure decreases, and doesn’t have a lot to do with the nature of the gases.
Oxy-helium has no effect on the danges of oxygen toxicity, which you affect by changing the percentage of oxygen in the breathing gas rather than the nature of the inert gas.
Finally, “popping up like a cork” (the technical term is “emergency ascent”) raises the danger of internal explosion. People have ascended quickly from great depths, but only by opening their mouths, tilting their heads back (to straighten the airway) and breathing out like **crazy[/b} while ascending.
[Aside - I once thought I was going to put that into practice. I was about 60 feet down in the vicinity of St. Johns when something worked its way into my regulator and I was breathing water. Unpleasant. However, my rig has a buddy-regulator (although I don’t carry a pony bottle) which I was able to use until I could clear my main regulator.]
jrf
[Note to Teeming Millions: When Ukulele Ike makes a pronouncement in the Science Arena, do NOT put his theories into practice without first checking with someone who actually Knows Science.]
Hey, guys! Know what makes your Seven-Up even FIZZIER?
Potassium cyanide!
Try it today!
Uke