Cis Lunar Mk 6

Tony_Q

While applauding the creativity embodied in the output from the developers of the new Cis Lunar Mk6 rebreather, I believe their achievements are being cheapened by the intellectual dishonesty of the marketing-spin embedded in the Poseidon Whitepaper.

It is patent nonsense to state or infer that Active Sensor Validation is better than a conventional 3-cell voting logic Oxygen control system, it is merely a different solution which may be better, or worse than, the 3-cell system.

What appears to have been over-looked in discussion to date is the primary purpose of the Oxygen control system (maintenance of a life-sustaining oxygen level within the breathing loop). The frequency and extent of diver intervention required (automatic/passive etc) for calibration/validation is merely a means to and end, not the primary purpose itself.

Quite apart from the adequacy of the calibration of the oxygen cell measuring loop gas PO2, for the oxygen control system to operate correctly, it needs a representative and uncontaminated sample of loop gas upon which to measure PO2 and base its control.

Whilethe Cis Lunar Mk6 ASV system makes great improvements with respect to standardisation of oxygen sensor calibration and elimination of diver intervention in the process, it does so at the cost of introducing a new source of gas sample contamination via leakage from the calibration gas injection valves.

The developers (as one would expect) obviously recognised this new failure mode and introduced a second oxygen sensor to help mitigate this risk. It is somewhat ironic that a very sophisticated oxygen calibration/validation system requires a “guardian angel” in the form of another oxygen cell!

An undetected contaminated gas sample at the primary oxygen sensor could very easily lead to the loop oxygen concentration going hyperoxic or hypoxic with dire consequencies for the diver.

Let us hope the guardian angel is up to its task.

I certainly hope this rebreather is very successful, but this should not be achieved by denigration of an oxygen control system (3 cell model) as inherently inferior, when the real point of difference is the degree of diver training and skill level required to safely utilise the respective oxygen control systems.

Tony

dave t

Ok many thanks Rich/Nigel for having the patience to answer my/our questions, you will be pleased to hear that for the moment I dont have any more, well maybe one more )

Lets look for a moment not at the technical stuff but at the practicals. I should say that if you were presenting this stuff as the new technology in the high end successor to the mk5p I would be wetting myself with excitement and working out who I can mug to get the money to buy one,but you are not are you? its aimed at the new diver whos stood in the shop deciding if he/she should be buying the xhundred dollar rig (tank, reg,bc,ect) or the xthousands dollar rig (cis). So whats the difference then? (he asks) they both go to 30m or is it 40m right? Yes! so apart from the bigger hole in my wallet why should I buy the xthousands then? ah RIGHT NO BUBBLES, SOLD!!!
Now hes sat on the dive boat, all his mates are diving, his xthousands has just told him when he jumped in the water and started to descend "a fault has been detected please make your way to the surface as quickly as possible"
Actually his mate had a problem as well on his xhundreds, too many bubbles or something!! the nice divemaster got out his multi-tool and tightened something and now his mate is back in the water. he asked the divemaster to tighten something on his xthousands but the divemaster says he doesnt understand how it works!!and it must go back to a service tech. But its a nice day, seas flat but he cant dive anymore this week cos his xthousands is all packed in its box ready to be shipped to the service tech!, the divemaster offered to lend him a xhundred rig but he doesnt know how to dive one!!


my last question, is this the future of rebreather diving for the masses?

best

Dave

najones

Actually Dave you are only partly correct. This is my real point. If the FO2 in the oxygen supply is known a priori, then it is a simple matter for the oxygen calibration system to compensate for this lack of purity. The down side to this is that it requires the user to:

1. Accurately measure the FO2 of each fill.
2. Enter it into the MKVI after each new fill.

Of course if you are diving in Europe or the USA and buying your O2 from a reputable supplier, then you could eliminate these steps and use the default value of 100%.

I have discussed this issue with Bill Stone and will be talking with Rich Pyle and others about it. My inclination will be to allow a sophisticated diver (and I'll deliberately avoid the definition of a sophisticated diver) to set the FO2 of the O2 supply. Once a definitive decision is made, I'll let you know.

As an aside, I'd like to thank Dave for bringing this up. My intentions on posting here were not completely altruistic. I was hoping to learn something - and I have. Keep up the probing questions!

najones

A little historical perspective. When we first introduced to the public the MKIV and MKV rebreathers the reactions were very similar to what has happened with the MKVI. There were legions of people standing up to denounce us. Statements such as "irresponsible", "idiotic", "can't work" etc were plastered all over the bulletin board systems and then internet forums. Conversely there were even more people that looked at what we did and concluded that a paradigm shift was underway in the technical diving field. There was a big "debate" whether electronically controlled rebreathers could work, or whether we should all be diving semi-closed systems. Well, I think a quick walk around DEMA this year has shown that the market has spoken and electronically controlled rebreathers do work and are now the work horse of technical diving.

So, is the MKVI the future of sport diving? I think so. Will there be situations like you described for the early adopters - probably. Will this prevent the inexorable conversion of sport diving over to rebreathers - I doubt it. Check back with me in a few years and we can compare notes!

najones

Rich has basically answered this. Notwithstanding the fact that doing rapid descents on rebreathers is contra-indicated for a long happy life, it's worth reiterating that the calibration / validation procedure is very quick (seconds).

netmage

I suppose thats the true value the partnership w/ Poseidon brings to the table. An existing service and supply channel infrastructure...

Heck, If it was <insert one of two large NA manufacturers who think they rule the world>, I could see rep's strong arming every dealer to have one in their shop for risk of being dropped.

esc

What kind of PC interface the system have?

There are quite few people who have left Windows world behind (me included) so I hope you will also introduce OSX "client" for diagnosing(?) the data from the unit via USB interface.

Actually even better (and what I would have done) would be "own" web based interface much like modern WLAN access points. You can log into them with any PC, Mac, Unix machine as long as it has a web browser and go through menus there for various things.

Yeah, all you rebreather manufacturers can send me donation for this idea :P

/esc

dave t

Ok point taken and I well remember the debates, I seem to remember I got called a few names for designing the original inspiration as well. But we are talking at slightly different angles here, I am not suggesting rebreathers are not for whoever wants to dive one for whatever reason I am just saying that No device ever built is foolproof and never will be. The mk6 will turn out to be a fine unit and maybe the safest rebreather yet, its not so much that that worries me its the divers who will use them. I work and dive a lot in the red sea and whenever I am on a boat with a load of sport divers I am constantly staggered at the incompetence of a lot of them. even with some of the excellent sport diver training which is available they still make stupid mistakes. If the mk6 training doesnt encompass everything that we teach to Rebreather divers now and more. If the mk6 doesnt allow the diver to take full advantage of the wealth of training info that is avalible now and more importantly to tap into the wealth of get me out the sh1t skills, I believe we will go backwards not forwards.

Actually as I have said before I hope I am wrong I really do and from a technical point of view you guys are coming out with some truly innovative stuff but the guys who are in charge of the marketing and training are maybe looking through rose tinted specs.

Can I ask how many of the team that will implement the training and marketing program are already rebreather instructors with a good 3-4 years of teaching rebreathers to base there intentions on?

best

Dave

Ben Field

Hi, Firstly I'd like to echo the thanks of others for you chipping in and answering our many questions, I recall as well you stated previously you're a tech man not a diver so please don't take this as personally

I am truly staggered, bought to a standstill, borderline speachless that; considering the team behind this and the research that must surely have been done to bring a recreational rebreather to a worldwide market you are needing to thank Dave for flagging up the variability of O2 quality. At a point where you've started to show the unit in public.

I thought this kind of info was known to all divers, its covered in nitrox lessson 1 if not before, even pure common sense says a manufactured product must have variable output?

My work involves testing new products and enhancements before they are released and I find issues like this from time to time, frightening things that R&D "didn't know."

We have a saying at work- "Its a good thing we don't make Helicopters..."

(Because our stuff has a nasty habit of stopping completely when it breaks)
Its an inconvience in our industry, in a piece of life support equipment its potentially fatal.

This makes me think the Mk6 is alot further back in its developement than is advertised.

Just my 2p's worth...

__________________

Beware Fridge Suck

onetime

First, I just want to give you my perspective on the thread. I don't believe there're "legions of people standing up to denounce" you. Remember that you're dealing with a lot of people who have spent a fair amount of time on rebreathers and that we simply want to understand the latest product in the market. To understand we question, probe, challenge. It's just the nature of this community here. It happens in pretty much every thread. I think, overall, most of the response here to your product is positive. There are some details that some disagree with but it seems that most recognize some of the changes as potentially significant.

That said, there are some excellent points being brought up. Variability of oxygen concentration would seem to be something that would have been considered but since it wasn't it's a great thing that this potentially major issue has been brought to the forefront and will be addressed. I have no doubt that it will be.

Another great point was just made by dave here:

Obviously if there is considerable demand for your unit then many current rebreather instructors will gain certification to teach it. They will certainly be among the best instructors you'll have. But, if the unit is successful, there will be more demand for courses than current rebreather instructors could fill. You'll then have to bring in recreational instructors that have experience diving Rebreather's to train up on teaching your unit. But again, if the product is successful demand will exceed even that supply. Then you'll be into trying to turn open circuit instructors into closed circuit instructors. That will entail a good bit of lag time for them to get comfortable/knowledgeable about RBs in order to safely teach new students to fly Rebreather's.

It will be interesting to see for sure.