Ask an Aquanaut: Breathing Mix?
Ron Peters Asks:Breathing mix question. What atmospheric mix are you using inside the habitat? Are you using the standard 21% or a richer mix? Is the same breathing mix used in the tanks during the aquanauts excursions outside the habitit? What is the deco profile for recovery of the aquanauts at the end of the mission?
Dear Ron
Aquarius, with its open ambient wet porch, has a constant air bleed throughout a mission, good old 21% like we breathe on the surface. The partial pressure of oxygen however is .45ATA and not .21 ATA because of the 47′ depth inside Aquarius. Nitrox or enriched air could be used for a habitat mix and diver breathing gas, this has been done in previous habitats in the 70’s with depth ranges of >50′. Mixes were selected to provide partial pressures of oxygen similar to atmospheric air at .21 ATA for that depth-called “normoxic” mixes.
Aquanauts are breathing air in their tanks, we have two high pressure compressors on the Life Support Buoy overhead, with 86,000 cu ft of storage air in flasks on the seabed.
Decompression, which was completed at 0830 yesterday morning, takes 17 hours, we close the swinging door to the wet porch, then slowly exhaust the atmosphere through an umbilical to the surface. Once we reach 0 FSW or “surface” inside Aquarius, we pressurize back to hatch depth of 45 FSW, open the door to the wet porch, and are greeted by two escort divers for a two minute ascent to the real surface on a short repetitive dive.
Craig Cooper
Aquarius Reef Base, Operations Director
Comment On This Post