1st deep (750 ft) hydrogen CCR dive: Gateway to deep exploration?

[kimh]

Simon Mitchell takes us back to New Zealand's Pearse Resurgence with Richard “Harry” Harris & the Wet Mules. Really interesting physiological & logistics/gear details.
~250 meters, 16 hours, 6°C…

"In February 2020 the Wet Mules diving team pushed the Pearse Resurgence cave to 245m. Further progress required overcoming the high-pressure neurological syndrome [HPNS] and reducing respired gas density. The solution to both problems would be a light and slightly narcotic gas; properties possessed by hydrogen. In February 2023 the team successfully tested hydrogen in a rebreather dive to 230m. This presentation is the story of that adventure."

 

[wetb4igetinthewater]

That is super interesting and I look forward to further research.

I did a chemistry experiment with hydrogen in high school. It was a "hydrogen generator." Mr. Davis told us to light it right away, and when it blew up and a glass tube was hanging out of my wrist, Mr. Davis said "well that was interesting!"

 

[GDHLEWIS]

Loved that the juvenile delinquency still exists in the giants of our sport. How to test it in a rebreather, inject and run like hell...brilliant and the obvious blowing a bag of the stuff up. Boys will be boys in the end

 

[kimh]

“He pressed the button of the Automatic Diluent Valve (ADV) on his rebreather, introducing hydrogen to the loop, and finally activated the solenoid before he started breathing from it. The first breaths were pleasant, he said. ‘It did feel very light and very slippery, and the hydrogen voice is even sillier than the helium voice, as you would expect,’ he said. ‘I don’t want people to rush away thinking this is a safe and sensible thing to do. I’m under no illusions I’ve produced any evidence for you to see, but this is an honest account of the hydrogen trials at my house.’”

“The unit had not exploded with a fill of oxygen from zero to 70%, and very low humidity. ‘Harry, dog, and CCR survive,’ as Harry wrote in his report of the trials. ‘Nothing bad had happened, so it was reasonable to move to the next step…’”

N=1: The Inside Story of the First-Ever Hydrogen CCR Dive

On Valentine’s Day, Dr. Richard Harris, aka ‘Dr. Harry,’ and the Wetmules made the first reported hydrogen (H2) rebreather dive to a depth of 230m/751 ft, in The Pearse Resurgence, New Zealand. The 13 hour dive, which was nearly two years in planning, was a field test to determine the efficacy...

gue.com

 

[elmo]

This is really interesting. And exciting to see what happens from here. Hopefully good exciting.
I can’t believe there are seemingly competent and experienced people on this forum wasting countless hours arguing over whether or not valve drills are difficult, when dives and expeditions like this are happening pushing the bounds of what can be achieved on scuba.

 

[kimh]

This is really interesting. And exciting to see what happens from here.

Agreed. I'll never do anything like this, but it's still totally fascinating to me. E.g. it never occurred to me that they would be adding gases for narcotic effect, to balance out HPNS.

 

[elmo]

I am curious how narcotic the hydrogen mix is. Clearly more narcotic than the 4/91 trimix they had used earlier. But how much more? At that depth, especially in a cave, you really need to be aware of the situation.

 

[admikar]

If I understood correctly, it's similar, but done for gas density purposes

 

[bletso]

Yes,
Simon Mitchel has long theorised that gas density must be included in gas calculations for deep technical dives. This in part to avoid or mitigate static lung pressures especially with rebreathers where negative static lung pressures can be experienced. Ref David Shaw accident analysis

 

[kimh]

If I understood correctly, it's similar, but done for gas density purposes

Yes, that’s the big reason for dealing with hydrogen. But apparently it also has a narcotic effect, along with the nitrogen. They’re trying to find the right balance. Richard Harris has said he’s more susceptible to HPNS than his diving partner.