I think you guys may mean hypothermia rather than hyper…
You're right, typo on my part. Correction made
On a related note, some divers were killed in the mid-70s from
hyperthermia. We all know about "heat of compression" from filling Scuba tanks. The same happens in chambers. Many sat complexes allow cross-connecting gauges in order to check them for accuracy and as backup in case of failure. Somebody had opened the cross-connect and the word didn't get back to the console operator (human factors sort of sucked).
The chamber that the gauge was actually connected to was unmanned and was about to be "surfaced" (pressure bled off) in order for crews to clean and repair. Bottom line, the operator heard gas blowing off, the pressure drooped on the gauge he thought was to the manned chamber, and started adding Helium as fast as possible in an attempt to overcome the "leak" (standard procedure). Lots of noise, yelling topside and over the unscrambler, and not much time passed.
By the time they figured it out the manned chamber was at or below the rated working pressure (not sure if relief valves popped), at least two guys were dead (don't recall exactly). As I understood it, they didn't know how hot it actually got. A byproduct of living in Helium's high thermal conductivity is shirt sleeve comfortable at say 600' is about 90° F... +/- about 1°. 93° is far more sweltering than the hottest day in Houston and teeth chatter at 88°.
I had dinner with some of the diver's onboard about a month later. Pretty sad.
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...I have mixed feelings about the rebreather bailout. We all know how bailout rigs are treated topside. Rebreathers obviously will have to be treated differently.
Mark Longstreath has very cryptically hinted that there is a very rugged rebreather that is being built solely as bailout for very deep commercial divers....
Saturation divers are more than technically competent enough to learn to maintain and dive rebreathers. But I ask anyone to imagine making a rebreather that is
absolutely reliable when not used beyond pre-dive checks, on the back of a working diver that must squeeze through a small hatch, could wear holes in his hot water suit in one dive (without coveralls), uses a hat instead of a mouthpiece, and has about as much as he can monitor now.
Now picture two of these rigs inside a 6' diameter sphere with two divers, bellman, hats, umbilicals, and all the rest of the systems that goes in a bell... unless you leave them outside and put them on after the hatch is open on the bottom. Slipping on an open-circuit bailout hung outside with one small LP hose to the hat with a QD (Quick Disconnect like a BC but larger) is one thing, but hooking up and keeping water out of two big flex hoses and breathing bags, plus connecting the readout display??? Sounds awfully ambitious.
I can see keeping the CO
2 canister and electronics over-pressured off the umbilical to keep them dry when not in use, but what about the flex hoses and breathing bags? The US Navy put breathing bags on the back in a cowling like the GE Mark 10 rebreather, but the "work of respiration" is bad enough at 1000' using a modern open circuit or reclaim hat. I am all for an improved and ruggedized rebreather, but sat divers will be the last to use them, not the first.
Oh, and then there is the issue of the efficiency of the CO
2 absorbent at 36° F, unless we heat it with hot water too. Even all this would be OK if we could keep the diver from passing out from hypothermia within a few minutes. The phrase "diminishing returns" comes to mind.
Now, after sharing some of the technical obstacles with others, I sure hope it works because I would love a rebreather that reliable! No bubbles and constant PPO
2 is as good as it gets, especially if reliability is so good that backup open circuit bottles are redundant.