The device that could save your life?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

If people rely on the sensors, computer and solenoids to maintain PPO2 in a rebreather why it is any more horrible to do the same with a BC? A depth gauge and computer analyzing ascent rate controlling solenoids adding or dumping air from a bladder is a straight foward system. Certainly no more complex than what constant constant PPO2 closed circuit rebreathers are doing.
For the record... until I can go a week without my laptop or phone locking up I will not dive a rebreather. But for someone willing to trust one the other should be no different.

I'm no engineer, but there are some problems with that analogy. CCR training involves having "know your PO2" drilled into your head and all of the various things that we do to make sure that the readout is accurate. It's not just set it and forget it.

A system with physical inputs and outputs like a bladder controlled by dumping and adding air, based on detecting and rapidly responding to an ascent rate, is a lot more difficult to design and implement. In an eCCR, the program is basically "open the solenoid, and shut it off when the PO2 hits the high setpoint. Any problem with an automatic BC - like the latency of the feedback loop or the difference in dump rate based on orientation of the wing - could cause a runaway ascent, which very recently seems to have killed an incredibly skilled diver on the Doria. That vicious cycle in a novice diver would be even more of a problem. The analogous situation with an eCCR (stuck open solenoid) is something that could be addressed immediately by shutting off the O2, and bailing out if a dil flush isn't enough to cool down the loop.
 
I like bringing Occam's razor to my dive planning


occam.jpg
 
Started reading this when it is already 4 pages in really reminds me of all the ways I can die horribly diving, yet nothing of this knowledge can keep me from the water. What a fascinating hobby we all have.
 
Some background on the creator. I believe he is active on spearboard.

Terry Maas Biography

Dr. Terry Maas

Terry Maas is a veteran freediver. He started diving when he was 14 years old and has been freediving steadily for the last 47 years. In his early years Terry won the individual U.S. National Spearfishing championships 4 times. His team won 10 championships. In 1982, his interests turned to blue water hunting. For the next 10 years he captured 3 world records for yellowfin and bluefin tuna ( IBSRC, bluefin tuna, Pacific, record, spearfishing ). His 398-lb Pacific bluefin tuna record still stands. In 1995, Terry published his first book, BlueWater Hunting and Freediving. This book is richly illustrated with pictures and stories from Mexico. Several years later he published his second book on the subject of freediving Freedive.

Terry studied marine biology in his undergraduate work at the University of California. He holds 3 advanced degrees, Doctor of Dental Science from University of the Pacific, Resident in Oral Surgery from the University of Southern California and Masters of Business Administration from Pepperdine University.

His 1992 video, Bluewater Hunters for PBS has been viewed by over 25 million people and has helped introduce the sport of bluewater spearfishing to the world. His diving has been featured in such publications as Sports Illustrated, American Airlines magazine, The Miami Herald and the Los Angeles Times. He lectures nationally using his slides and video presentations to educate those interested in the adventure of bluewater hunting and marine resource conservation. Terry is the director of the International Blue Water Spearfishing Records Committee an organization that documents and maintains world records for blue water species taken freediving. It is affiliated with the Underwater Society of America.

Maas is an accomplished videographer. His rare footage of wild yellowfin tuna taken at Socorro Island is displayed in two sections of the Monterey Bay Aquarium open water exhibit. He has produced two commercial videos, The Joy of Freediving and Freediving Made Easy. November 08, Terry captured video of marlin, sea-lions and whales all attacking bait balls of sardines off the coast of Baja California, Mexico. The footage is available on YouTube: . This production won the first place in the 09 amature video competition at the Our World Underwater film expo 2009 and was featured at the Boston Sea Rovers Evening film exposition.

Terry loves to document the underwater world on still film and in magazine articles. His recent article documenting the natural history of manta rays was the featured as the front-cover exhibit in Mexico Desconocido (July 2002). His articles and photographs have been featured in such US magazines as Sport Diver, Skin Diver, Scuba Times, Western Diver and California Diving News. Internationally, his articles appear in Sterne (Germany), Focus (Italy), Dive New Zealand and Australian Freediving and Spearfishing News. In 2000, he was inducted as a fellow into the Explorers’ Club of New York.

Terry was the principal under water videographer and co-host for the TV series SPEARGUN HUNTER on the Outdoor Channel where he filmed 23 consecutive episodes.

Terry’s most recent documentation project is a recreation of the marine environment off the Channel Islands of California. He was commissioned by the National Parks Service to create a mural demonstrating biodiversity at the islands. Using his painting of white seabass in a kelp forest, Terry incorporated many other photographs of reef and pelagic animals frequenting the islands.

While Terry remains an avid hunter, he is very selective in his take and is deeply concerned with conservation of the ocean’s bounty. He shares his underwater images of sea creatures captured in commercial poaching nets and on hooks with many environmental organizations. He is an active supporter of Sea Watch an organization dedicated to the preservation of the Sea of Cortez in Mexico. In California, he is a member of the committee to form Marine Protected Areas off the coastline.

Terry is an expert witness for speargun and blackout related injuries.

Maas is currently working with a broad coalition of national and international freedivers to develop a vest for the management of freediver blackout. This device is analogous to a biker’s helmet, a skydiver’s back-up safety chute, and the car driver’s airbag. Initial prototype testing is underway after an investment of over 3 years of product development and research. See www.oceanicss.com
 
I'm no engineer, but there are some problems with that analogy. CCR training involves having "know your PO2" drilled into your head and all of the various things that we do to make sure that the readout is accurate. It's not just set it and forget it.

A system with physical inputs and outputs like a bladder controlled by dumping and adding air, based on detecting and rapidly responding to an ascent rate, is a lot more difficult to design and implement. In an eCCR, the program is basically "open the solenoid, and shut it off when the PO2 hits the high setpoint. Any problem with an automatic BC - like the latency of the feedback loop or the difference in dump rate based on orientation of the wing - could cause a runaway ascent, which very recently seems to have killed an incredibly skilled diver on the Doria. That vicious cycle in a novice diver would be even more of a problem. The analogous situation with an eCCR (stuck open solenoid) is something that could be addressed immediately by shutting off the O2, and bailing out if a dil flush isn't enough to cool down the loop.

I am an engineer. Conceptually there is no difference. You are opening and closing solenoids based on inputs to a control algorithm. The implementation is different but not by much. Sensors provide input to an algorithm that controls valves.
Reaction to a failure of the system also seems similar. Identify an out of control ascent - disconnect the supply and dump the air in the wing. How is this different from an uncontrolled ascent in any diving? How is this different that your reaction to a stuck O2 solenoid?
The major difference is really in the purpose. We are discussing an emergency device not an autopilot BC. If you become unresponsive at depth what are your options? Drowning if no action is taken. A less than perfect device that would get you moving to the surface doesn’t seem like a horrible alternative. Yes it could fail. If you’re conscious you react. If not it’s a matter of whether or not you are better off at depth or on your way to the surface.
I don’t dive an eCCR and I’m not arguing for this device either. But if someone can justify accepting the failure risk of one it is not much of a leap to accepting the other.
I’ll stick to OC diving.
 
I am an engineer. Conceptually there is no difference. You are opening and closing solenoids based on inputs to a control algorithm. The implementation is different but not by much. Sensors provide input to an algorithm that controls valves.

I totally agree with you about the larger question, and that was my first response to the OP. It is ALWAYS going to be better to be blown to the surface if you are really unresponsive and alone. My objection was the idea that an OC diver is likely to become unresponsive in the first place. As I said, if that’s a statistically significant problem, we really need to worry about drivers, not divers. I also drifted off the OP’s question, in responding to Diver-Drex’s point about an automatic BC being no different than an eCCR, and I pointed out why I thought that those two things were different.

I’m not competent to argue engineering with you, I defer to your experience and training. And conceptually there is no difference - some sensor gives you a reading, you open or close a solenoid based on that reading. But by that logic, there is no difference between a self driving car that brakes to avoid a collision and a toaster that shuts off when the toast is done. The implementation is the whole problem, and I do think that it’s much different with these two applications.

Dumping gas isn’t just dependent on a valve being open or closed, it’s dependent on orientation and the position of the gas bubble in the bladder relative to the valve. I guess that engineering efforts could address that too, not sure. But there are differences between dealing with a runaway ascent and dealing with a hot loop which are beyond the scope of this discussion.
 
https://www.shearwater.com/products/swift/

Back
Top Bottom