As much as bullets or body armor, rations or radios, an army needs water to survive – especially when it's fighting in the blistering heat of an Iraqi summer. But hauling a soldier's daily requirement of three to four gallons of water has become a gargantuan burden to U.S. armed forces. So Darpa, the Pentagon's mad science division, has come up with a plan for thirsty GIs: Cut the amount of the water they're carrying in half, and pluck the rest from out of thin air.
Even in the parched Mesopotamian desert, the air holds plenty of water. The trick is getting it out. Machines have been around for years that can cool the air down to the point where water droplets will condense like dew beading on an oak leaf. But they're energy hogs, using almost 650 watt-hours just to get a single quart of H20. The goal of Darpa's Water Harvesting program is to extract that water without using up so much power.
That would make a huge difference to troops stationed in the Middle East. "With the temperatures in August soaring well above 125 degrees (Fahrenheit)," writes Chief Warrant Officer Gordon Cimoli, a Black Hawk helicopter pilot who served 10 months in Iraq, "water is life."
"If Darpa can pull it off it would be a tremendous weight off our back, both literally and figuratively," a U.S. Army captain currently stationed in Iraq added in an e-mail. Water takes up to 40 percent of the Army's daily logistical load, according to one military report – nearly 55 pounds of water per soldier per day, when medical treatment, meal rehydration and bathing are factored in.
The folks at Sciperio – a Darpa-funded research firm based in Stillwater, Oklahoma – think they've found a way to effectively wring water from the skies. When air passes over liquid lithium chloride, water vapor becomes trapped, instantly, explains Sciperio managing partner William Warren. The result is a brackish fluid, undrinkable by even the toughest soldier. Fresh water can be extracted, however, using a filtration process known as reverse osmosis. To oversimplify, the setup uses high pressure to drive the undrinkable liquid through a semipermeable membrane, which traps the salt and allows H20 to flow through. Usually, the process has to be repeated several times in order to get something potable. That wastes energy. But advanced pumps from Spectra Watermachines use the salty leftovers to re-pressurize the system, letting it act more efficiently.
Darpa has given Sciperio and its research partners about $4 million, so far, for the project. But while the individual components have been tested, the system as a whole won't be ready until January or February, Warren said.
By then, three prototype Humvees could be in Iraq, supplying troops with water from an even less likely source than desert air: the fuel the vehicles run on. Diesel fuel is made of about 13 percent hydrogen. So when diesel exhaust is combined with oxygen and cooled down, water is the result, notes Marit Mazzeti, a manager at LexCarb, which has received about $2.5 million from the Army and Darpa for its water-extraction research.
It's a fairly efficient way to get the water – two gallons of diesel yield a gallon of H20. And the system, which fits inside the Hummer's wheel arch, only uses about 5 percent of the engine's power. That's about the same as what the air-conditioning unit gobbles up. But the water that's produced is full of highly acidic sulfur and nitrogen oxides, as well as soot, benzene and other organic compounds. LexCarb's first carbon filter "significantly improved the appearance of the condensate from a particulate-laden black liquid to a clear brownish-yellow liquid," an Army report (.pdf) notes. Several other filter passes were needed before the water became clear and safe to drink.
If the LexCarb prototypes work, the system could make military operations in the Middle East significantly easier. It might "prevent most, if not all, heat casualties," one Army captain told Wired News.
"The body armor makes it feel at least 10 degrees hotter than the air temperature. We all are issued CamelBaks (water pouches) to hook on our body armor but you can go through a CamelBak pretty quickly when it's 120 degrees outside," the captain explained. "We go through the bottled water at a fairly quick pace. (Every few days), they'll bring in an entire truckload with several large pallets and probably a couple thousand bottles of water. We'll get 20 to 30 soldiers out there to form a chain, and it still takes a while to stack all the bottles up."
During the early days of the Iraq invasion, some American troops complained that water was agonizingly hard to come by. "It seemed impossible to maintain our necessary supplies of water and food. We all carried five days of supply with us ... with the intent of utilizing it only in an 'emergency' situation. The problem being that because our logistics lines were so poor, we had to break into them during the trip," one senior noncommissioned officer told Soldiers for the Truth.
The Army would like to see that dependence on water carriers dramatically cut back. That's why the service has been funding LexCarb's H20-making Hummers.
"This will provide military units with a radically more mobile and flexible water-production capability," a military research paper asserts. If the Humvees work as planned, troops might be able to go without resupplying one of their most vital resources – the water they drink – for as long as a week.
