CCR Liberty - a new fault-tolerant rebreather

[descent]

Jakub at GG has revealed something nice from his secret workshop: the CCR Liberty.




4 oxygen sensors
2 helium sensors – patented
2 methods of ppO₂ measuring
2 independent computers
2 solenoid valves
4 displays

"No single malfunction in the electronic system can cause a breakdown of the whole apparatus."

MOD: 100m
WOB: 1.58 J/l @ 100 m

Weight of the CCR Liberty prepared for diving (without ballast): 36.5 kg (80.5 lbs)
Transport weight (without tanks, without scrubber filling): 23.5 kg (51.8 lbs)
Endurance according to EN 14143:2013 (CO₂ production of 1.6 l/min): 2:48 h
Endurance with CO₂ production of 1 l/min (corresponds to increased effort in cold water and at great depth): 4 h
Endurance with CO₂ production of 0.7 l/min (corresponds to moderate effort in favorable conditions): 6 h
Maximum depth in tests according to EN 14143:2013: 100 m (330 feet)
Depth gauge precision test: 350 m (1,150 feet)
Pressure test of all components: 600 m (1,960 feet)

Deepest dive of which we are aware: 140 m (460 feet)
Longest dive of which we are aware: 9 h (though we consider this to be somewhat unreasonable)

 

[Dr. Lecter]

It's a front lung unit...where's all that weight coming from? Heavier than my SS rEvo, looks like.

What's the rationale behind the HE sensors...sanity check on the O2 cells?

 

[descent]

... What's the rationale behind the HE sensors...sanity check on the O2 cells?

Yes.

The redundant He sensors deduce the pp02 based on the remaining fraction of inert gases. Clever. They got a patent on it.

---------- Post added February 6th, 2015 at 12:54 AM ----------

It's a front lung unit...where's all that weight coming from? Heavier than my SS rEvo, looks like. ...

I was wondering about that. The engineering drawings of the loop components and the "air-mass treatment" section don't show any huge voids that need to be offset with stacks of lead roofing tiles. I am at a loss.

God, it would be flat-out terrifying to get a boom while strapped to something that heavy.

Best guess after midnight on a weeknight is ... the nice looking built-in stainless steel frame/stand?

 

[Omisson]

Wouldn't the weight itself be a turn off given what's out there ?

What is the scrubber volume - and how is it set up to work - packed, preformed?

What's the electronics set up ? What helium computer/sensors?
Why add the helium sensors but not a CO2 sensor unit?

 

[Dr. Lecter]

I'm curious how they're pegging ppO2 from ppHE when there's an unknown fraction of N in play...but I'll assume for now they've figured it out somehow and just say cool!

 

[descent]

Wouldn't the weight itself be a turn off given what's out there ?

What is the scrubber volume - and how is it set up to work - packed, preformed?

What's the electronics set up ? What helium computer/sensors?
Why add the helium sensors but not a CO2 sensor unit?

For an expedition diver, maybe a massive rig is reassuring. Out in the middle of nowhere, it's all you've got.

For me, extra mass is a liability. I like to be able to twist around and get into unusual positions. Large volume and mass create an extra separation between me and the immediate environment that I like to try to avoid.


Absorbent:

The CO2 scrubber is hand packed, and uses uses bulk loose grain absorbent.

"The recommended scrubber filling material is Sofnolime 797 sorbent (producer: Molecular Products). The cartridge holds approximately 2.5 kg of sorbent."


Helium sensors:

Each helium sensor contains a cavity of known dimension where the speed of sound is measured. Two sensors are used, for redundancy.

If the operator has previously entered the analyzed fractions of inert gases present in the diluent before the dive, the computers can measure the helium present to estimate the partial pressure of oxygen of the breathing gases. This is less accurate than direct measurement of oxygen, and is considered an emergency fallback.

In the case of failure of all four electrogalvanic oxygen sensor cells, these additional sensors ensure that the diver will have some indirect knowledge of loop oxygen contents while considering options, but it is recommended that a diver without functioning direct O2 measurement hardware bail out immediately.


Computer Controlled Oxygen Delivery:

"Predictive regulation is used. Measured ppO2 is adjusted according to the physical model of the breathing loop. The calculation of O2 delivery and possible subsequent opening of the solenoid is performed with at six-second intervals. Oxygen is added alternately using the solenoids corresponding to both control units."

In Surface mode, a .19 to .23 pp02 is maintained in the loop to prevent accidental hypoxia before transitioning to a diving mode.

Other operating modes include CCR, mCCR, Bailout, and Setup, each with decompression settings.


Computers:

The dual control units receive user input from either of the two redundant handsets, as well as oxygen measurement sensors, pressure and temperature sensors.

The handsets operate independently, and can display different information simultaneously. A three-LED HUD provides summary information within the operator's field of view. A single-LED buddy display on the back of the unit provides similar status indications in the field of view of a trailing diver.


Initial Lack of CO2 sensor:

Jakub says, "The CO2 sensor we were working on few years ago was a prototype. We were never able to get meaningful results with it. It is still a project but currently on back burner."

 

[descent]

A disassembled CCR Liberty head.

One helium sensor is in place, in the left socket. At the far left edge of the photo - two stainless steel solenoids?

 

[fishb0y]

That helium sensor sounds like a solution looking for a problem. I guess I would actually see this in the wild before I really come to judgement.

 

[descent]

... I would actually see this in the wild before I really come to judgement.

The design and manufacturing team in the Czech Republic put up a Youtube video showing seven of the thirty-something prototypes being tested in an iced-over quarry.




At the end, they celebrate a successful dive in a heartwarming way.