Where to Find the Best Diving Gear? Not the U.S. Navy

Military diving tech lags behind civilian equipment

Where to Find the Best Diving Gear? Not the U.S. Navy Where to Find the Best Diving Gear? Not the U.S. Navy

Uncategorized December 7, 2014 0

Thousands of people around the world explore the underwater world every day using self-contained, underwater breathing apparatuses known as scuba gear. Invented during World... Where to Find the Best Diving Gear? Not the U.S. Navy

Thousands of people around the world explore the underwater world every day using self-contained, underwater breathing apparatuses known as scuba gear.

Invented during World War II by Jacques Cousteau and Emile Gagnan, this simple but effective system for breathing compressed gas from a cylinder revolutionized diving during the 20th century.

But the U.S. Navy took their time adopting scuba gear, and are slow to adopt improved diving technologies today. Naval conservatism and procurement friction keep military divers from using better equipment.

The result is that civilians are heading out into the waters with much more reliable, and safer equipment than their military counterparts.

To understand the gap, it’s worth taking a look at the history of diving gear — and how this hardware keeps people alive.

For a century before the arrival of scuba gear, divers used the classic hardhat system. Diving gear consisted of an iconic metal diver’s helmet fitted with portholes, a waterproof canvas suit and large amounts of lead weight—which kept the buoyant diver on the bottom. Surface crews pumped breathing gas into the diver’s suit through long hoses.

Hardhat divers never ran out of air, as long as their surface tenders kept pumping gas through the hoses. But the hoses limited a diver’s range and movement—and risked the diver’s life if the hoses failed.

It was not a self-contained system, like scuba, which enabled the freedom to explore the underwater realm on one’s own terms. As a consequence, civilian divers enthusiastically adopted scuba after World War II.

Naval divers took much longer. The Navy only replaced its classic hardhat rigs with scuba systems—for shallower dives—in the 1960s.

One reason is that very long-duration dives still require modern versions of hoses and hardhats, because divers simply can’t carry enough gas.

In order to carry enough breathing gas, free-swimming scuba divers use portable storage tanks pressurized to thousands of pounds per square inch. Regulators control the flow of compressed gas to a diver’s lungs, and lower the tank pressure to something a human can breathe without injury.

Basic physics also require that this regulated system respond to changes in depth.

At sea level, the Earth’s atmosphere subjects a human body to more than 14 pounds per square inch. We normally don’t feel it, because our bodies regulate internal and external pressure on their own. Changes in altitude quickly bring this surrounding pressure to our attention, as anyone who’s tried to pop their ears on a plane flight has experienced.

During diving, these changes in pressure are even more intense. Every 33 feet down, a diver adds a full atmosphere’s worth of pressure to their body. At 100 feet down, the pressure is more than four times greater than at the surface.

Scuba gear allows a diver to breathe in compressed gas at a pressure matching the surrounding pressure.

Standard scuba systems are also known as “open-circuit.” This means that a diver’s exhaled breath vents into the water and bubbles away. The deeper you go, the more gas you breathe to compensate for the increasing depth. That means more gas you have to carry on your back. This continuous loss of gas is one factor limiting the duration of a dive.

However, if a system can recycle the diver’s breath, they can stay down much longer.

Humans metabolize only about four percent of the oxygen in a single breath of air, leaving plenty left for more breathing. Replacing the lost oxygen—and removing the exhaled carbon dioxide—means a diver can “re-breathe” the air mixture.

Submariner wearing a Momsen Lung escape rebreather, 1930. US Navy photo. At top—Canadian Lt. Robert Watt wearing an oxygen rebreather in 1997. Photo via Defenseimagery.mil

Breathing from a bag

Here’s how rebreathing works. An oxygen source replenishes the metabolized oxygen, and a scrubber removes the carbon dioxide. The system is self contained and “closed-circuit” — almost nothing gets vented from the loop.

Using a rebreather, underwater endurance can last hours, not minutes.

For decades, rebreathers provided mine rescuers with safe breathing gas in toxic environments. Astronauts used rebreathing systems on the Moon, and still use them today on the International Space Station.

Rebreathing predates scuba by centuries. The first known account of the concept dates from the 17th century. Divers also used a rebreathing apparatus in 1880 to close valves deep inside a flooded tunnel under the Severn River in England.

During the first half of the 20th century, submarine crews used rebreathers to escape from downed subs. During World War II, Italian, British, German and American frogmen used the systems for attack and reconnaissance missions. For commandos, rebreathers offer endurance as well as stealth, since there are no telltale bubbles give away the diver’s presence.

All these systems worked by adding pure oxygen and removing built-up carbon dioxide. But keeping these gases within safe limits is tricky.

Too much oxygen causes seizures, but too much carbon dioxide causes unconsciousness and death. There’s very little room for error.

Until the end of the 20th century, even advanced rebreather systems lacked methods of alerting divers about problems. Divers planned their dives based on how long the CO2 absorbent could last, and they watched their gauges carefully. Even experienced naval divers ran into trouble using early deep-dive rebreathers. Some died.

The Navy is still getting a handle on rebreather risks today. In the September issue of Faceplate, the journal of the Navy’s diving and salvage community, researchers announced a prototype device for measuring the CO2 absorbent reaction in a rebreather scrubber.

According to the magazine, technicians created a “gas-gauge” bar that indicates a scrubber’s status and remaining life—and added it to a wrist console that displays the oxygen content of the diver’s breathing gas.

A second prototype device measures the CO2 content of recycled breathing gas, and alerts the diver when the level rises above critical levels. Navy scientists and divers are currently evaluating the two systems for possible adoption by the fleet.

This sounds great—but qualified civilian divers are using the same technology right now in a commercially available rebreather.

At left—AP Diving’s CO2 sensor in yellow. At right—evolution rebreather console displaying scrubber monitor bar & CO2 alarm. Photos via AP Diving

Diving evolution

Some of these cutting-edge rebreathing systems were on display in November at the Diving Equipment Manufacturers Association conference in Las Vegas.

One rebreather from British manufacturer Ambient Pressure Diving can be upgraded now with a scrubber monitor, a CO2 sensor and a real-time heads-up display. We also spoke with Mike Fowler of Silent Diving Systems, which sells the system.

All it takes is proper training—they won’t sell you a unit without it—and a credit card. And the gear is years ahead of what the Navy uses. We asked Fowler why Navy divers haven’t simply bought off-the-shelf gear.

“It’s both the natural conservatism of mariners and the huge sunk costs of their existing systems,” he said.

In general, marine technology works on the if-it’s-not-broke, don’t-fix-it rule, so it takes time for the Navy to accept innovations.

The Navy has more than a century of diving experience, and decades of investment in their suppliers, the technology, the spare parts for the technology—and the training regimens to use it. That’s a lot of inertia to overcome.

Other navies with less diving experience are adopting the newer tech more quickly. Fowler noted a Latin American nation just purchased his company’s products for its naval divers.

The rebreathers do fall under export controls, because of their status as a dual-use civilian and military technology. In addition to requiring proof of proper training before selling their equipment, the company maintains lists of countries they can legally sell to.

So even though you can charge an advanced rebreather to your credit card, you still can’t just get one. Just like the Navy.

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