The Hindenburg wasn’t brought down by lightning, static, or sabotage. History’s most famous airship was destroyed by helium. Or rather, the lack thereof. The zeppelin’s Nazi builders balked at the price of this rare, lighter-than-air gas. So instead, they filled the blimp with hydrogen, which is much less expensive, just as buoyant, but way more
explosive. So no matter what chain of events led up to the explosion, it was helium’s scarcity that killed the airship. And today, the same gas – rare as ever – is putting a major cramp in deep sea diving operations.
The U.S. Navy’s divers are responsible for a wide variety of salvage and rescue tasks, from prying sunken wrecks off the sea floor to bringing distressed submarines to the surface. But every one of those divers needs oxygen that’s cut with expensive helium (rather than nitrogen, which makes up most of the atmospheric cocktail we breathe on the surface). So to reduce costs – an enable more missions – the Navy has developed a new diving apparatus that rescues the helium from a diver’s exhalations.
For shallow diving, a mixture of oxygen and nitrogen is fine. But nitrogen is bad for deep divers, because it’s impractical for them to ascend slowly enough to prevent the gas from causing the bends and other agonizing physiological conditions. So for deep operations, divers get pumped a mixture of oxygen and helium from the surface. “But metabolically, the diver’s only used about 5 percent of the helium gas in each breath,” says John Camperman, the senior diving and life support scientist at the Naval Experimental Diving Unit in Panama Beach, Fl. A lot of oxygen gets wasted this way, too, bubbling away to the surface with every exhale.
Divers could re-use that exhaled air, using up the rest of the oxygen and helium, if only for all the carbon dioxide that comes with it. The solution? A suit that recycles the air back into a breathable composition. “Instead of exhaling your entire breath into the sea, you now are exhaling into a carbon dioxide scrubber,” says Camperman, whose lab developed the technology. The scrubber, carried in a backpack, is actually a canister full of granular calcium hydroxide. This material chemically binds to carbon dioxide molecules, pulling them out of the diver’s dirty breath. Now, instead of of flooding the diver with fresh air, the supply from the surface is a measured trickle. “It operates on the principle of injecting just the right amount of helium and oxygen to maintain the balance of gases,” says Camperman. He says the rebreather saves about 80 percent of the helium from each breath.
This pack won’t just slash the Navy’s helium budget. “It also reduces the size of our logistical footprint,” says says Warrant Officer Coy Everage, the diving officer at the Navy’s Explosive Ordinance Disposal unit based in Little Creek, Va. (The explosive ordinance groups handle the Navy’s salvage and rescue operations.) This is because cylinders of oxygen and helium take up a lot of space, and cutting down on that load will help put divers where they need to be a lot quicker. “Figuratively speaking, it’s a lot easier get on Delta Airlines with a suitcase as a carry-on rather than bringing aboard a whole truck,” says Everage. (Figuratively, because trying to bring even a shampoo-bottle sized container of compressed gas on a commercial airliner would get you put on the TSA’s naughty list. Navy divers move their compressed gases around the world – carefully! – using Navy planes and ships.)
Reducing helium costs could also give the Navy reason to reconsider salvage operations that had been sidelined, says Camperman. And unlike the Hindenburg, cutting down on helium probably isn’t going to cause any subsurface explosions.
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