SEALAB II, what did they breathe?
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Dr Deco
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Hello MikeC:
I am not sure about SEALAB. I am more familiar with NASAs NEEMO. The SEALAB was probably similar, but I believe it was helium filled.
NEEMO Decompression
The habitat is filled with air. When it is time for the return to the surface. The habitat is sealed, and the pressure is decreased over a period of 16 hours to surface pressure [though the habitat physically is still anchored to the bottom]. There are also three oxygen-breathing periods. When the time comes for the crewmembers to exit to the outside (surface), the habitats internal pressure is quickly pressurized to 60 fsw, the hatch is opened, and the aquanauts swim out and ascend.
Dr Deco :doctor:
I am not sure about SEALAB. I am more familiar with NASAs NEEMO. The SEALAB was probably similar, but I believe it was helium filled.
NEEMO Decompression
The habitat is filled with air. When it is time for the return to the surface. The habitat is sealed, and the pressure is decreased over a period of 16 hours to surface pressure [though the habitat physically is still anchored to the bottom]. There are also three oxygen-breathing periods. When the time comes for the crewmembers to exit to the outside (surface), the habitats internal pressure is quickly pressurized to 60 fsw, the hatch is opened, and the aquanauts swim out and ascend.
Dr Deco :doctor:
Bob3
Contributor
I did a quick look-see in a book by Bob Barth [Sea Dwellers], he didn't mention the mix but did say it was pretty amusing when Scott Carpenter tried to call the Whitehouse (with the chipmunk voice) & the operator didn't want to let him through to LBJ.
The deco schedule was mentioned as being 2 days, they hauled them up in a bell for topside deco.
15% O2 was a common mix for the heliox because it could be used from a hair over 300' on up to surface w/o gas switches, depending on time used & workload.
I don't have a clue about what mix was actually used in the habitat, but the PP shouldn't have been over 1.6
The deco schedule was mentioned as being 2 days, they hauled them up in a bell for topside deco.
15% O2 was a common mix for the heliox because it could be used from a hair over 300' on up to surface w/o gas switches, depending on time used & workload.
I don't have a clue about what mix was actually used in the habitat, but the PP shouldn't have been over 1.6
SEALAB Author Ben H.
Contributor
Hello! I just noticed this old thread and wanted to let you know that the answers to these and many other questions anyone might have about SEALAB I, II or III and a number of related experimental diving ventures - including some by Jacques Cousteau - can be found in my new book, SEALAB: America's Forgotten Quest to Live and Work on the Ocean Floor, available on Amazon (hardcover and e-book) and all the usual places. There have been some great comments recently in the Books and Media Reviews forum and elsewhere on ScubaBoard. Other reviews can be seen on my website, too, along with an excerpt so you can get a sense of the story. . .
I understand it was essentially the same one used today published in the US Navy Manual, Revision 6, Page 15-3:
Table 15‑9. Saturation Decompression Rates.
[TABLE="class: grid, width: 500"]
[TR]
[TD]
[TD]Rate
[/TD]
[/TR]
[TR]
[TD]
[TD]6 feet per hour
[/TD]
[/TR]
[TR]
[TD]
[TD]5 feet per hour
[/TD]
[/TR]
[TR]
[TD]
[TD]4 feet per hour
[/TD]
[/TR]
[TR]
[TD]
[TD]3 feet per hour
[/TD]
[/TR]
[/TABLE]
They would often stop decompression during sleeping hours because guys would sleep on a leg or arm and get joint hits. The tables were developed at the old EDU (Experimental Diving Unit) at the Washington Navy Yard and were pretty solid down to 200' by Sealab II.
Info on the Mix
Standard procedure is to pressurize the habitat or DDS (Deep Diving System) with pure helium. Assuming no leaks (never the case with any of the Sealab experiments) the PPO2 stays at 0.21 ATA regardless of depth.
Oxygen is automatically added (through a venturi to ensure mixing) to a set-point, usually around 0.30 ATA. They used off-the-shelf oxygen analyzers made by Teledyne wired to small a LP solenoid valve by Sealab III, and maybe earlier. I was an electronics tech on the Mark II DDS that was built for Sealab III a few years after Cannons death. One of the Sealab III Master Divers was still onboard told me they used the same controls.
I understand these controls were first tested and used at EDU so I imagine that they would have also been used on Sealab II. Tuck (Chief Cyril Tuckfield Jr) was the only guy still around that had been on all three Sealab projects by the time I came along. He was an Engineman so we never talked about monitoring and control systems.
They used a rich HeO2 pre-mix in the water since they were on semi-closed circuit rebreathers.
Table 15‑9. Saturation Decompression Rates.
[TABLE="class: grid, width: 500"]
[TR]
[TD]
Depth
[/TD][TD]Rate
[/TD]
[/TR]
[TR]
[TD]
1,600 200 fsw
[/TD][TD]6 feet per hour
[/TD]
[/TR]
[TR]
[TD]
200 100 fsw
[/TD][TD]5 feet per hour
[/TD]
[/TR]
[TR]
[TD]
100 50 fsw
[/TD][TD]4 feet per hour
[/TD]
[/TR]
[TR]
[TD]
50 0 fsw
[/TD][TD]3 feet per hour
[/TD]
[/TR]
[/TABLE]
They would often stop decompression during sleeping hours because guys would sleep on a leg or arm and get joint hits. The tables were developed at the old EDU (Experimental Diving Unit) at the Washington Navy Yard and were pretty solid down to 200' by Sealab II.
Info on the Mix
Standard procedure is to pressurize the habitat or DDS (Deep Diving System) with pure helium. Assuming no leaks (never the case with any of the Sealab experiments) the PPO2 stays at 0.21 ATA regardless of depth.
Oxygen is automatically added (through a venturi to ensure mixing) to a set-point, usually around 0.30 ATA. They used off-the-shelf oxygen analyzers made by Teledyne wired to small a LP solenoid valve by Sealab III, and maybe earlier. I was an electronics tech on the Mark II DDS that was built for Sealab III a few years after Cannons death. One of the Sealab III Master Divers was still onboard told me they used the same controls.
I understand these controls were first tested and used at EDU so I imagine that they would have also been used on Sealab II. Tuck (Chief Cyril Tuckfield Jr) was the only guy still around that had been on all three Sealab projects by the time I came along. He was an Engineman so we never talked about monitoring and control systems.
They used a rich HeO2 pre-mix in the water since they were on semi-closed circuit rebreathers.
I put this on the Vintage Scuba Supply website, under Diving Media.
According to Part 1, they were breathing the following mixture: He 80%, N2 16%, O2 4%.
The Rubicon Foundation also has several papers on the subject:
http://archive.rubicon-foundation.org/xmlui/search?query=SeaLab
SeaRat
The Rubicon Foundation also has several papers on the subject:
http://archive.rubicon-foundation.org/xmlui/search?query=SeaLab
SeaRat
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