The U.S. Army sent the first of its Stryker Mobile Gun Systems to Iraq last year. This is a Stryker armed with 105mm gun. There is a three man crew, mainly because the gun has an automatic loader. The gun is stabilized, and can be fired on the move. Once in Iraq, the gun performed well. There were some problems, however. In order to get all the gear needed for a 105mm gun into a Stryker vehicle, there was no room for air conditioning. In summertime Iraq, this presents a problem. The three man crew had to be equipped with something that would prevent heat stroke. The solution was the "air conditioned suit" of legend, and science fiction. Back in 2003, after three years of development, the U.S. Army put into service the "Air Warrior Microclimate Cooling System." It's a vest full of tiny tubes that carry cooled water (with some non-toxic antifreeze added). Worn under the flak jacket, it keeps the trunk of the wearer cool, thus greatly reducing the "heat load" and potential for heat stroke or heat fatigue. It was originally meant to be used by pilots in smaller (un-air-conditioned) helicopters or door gunners of larger choppers.
Helicopter crews, especially the crew chiefs who man a machine-gun mounted on an open door, have always had a problem with the weather. Few military helicopters have air conditioning, even for the pilots, and the crew chief on the UH-60 Blackhawk has to stay on his feet, and alert, for up to three hours at a time. In tropical areas, be they Vietnam four decades ago, or Iraq today, that can be a real chore. The crew chief wears a fire-resistant jumpsuit, flak jacket and helmet. Flying low to the ground, the heat is often over 100 degrees. Often there's not much breeze, for the chopper frequently hovers or moves slowly (under fifty kilometers an hour.) So the crew chief has to fight the heat while staying alert to any potential threats below. When the helicopter lands, the crew chief has to help with loading or unloading personnel or cargo, and maybe run around the chopper to check for any damage.
The cooling vest can only be used in vehicles, because the entire unit consists of the vest, a 13 pound cooling unit and an umbilical cord that attached to the vest. The cooling unit is plugged into the vehicle electrical system. Those first vests cost about $7,000 each, but the price has come down a bit as more were manufactured. Some of the vests had already been used in armored vehicles, usually for the turret gunner, who had his chest and head out in the heat for hours at a time.
Before getting the vests, the Mobile Gun System crews tried other solutions, one being an intravenous drip (water going into their body via a needle). This was awkward, especially if you had to get out of the vehicle in a hurry. That, in turn, revealed another problem with the Mobile Gun System; the hatches were too small for larger troops, wearing the cooling vest and their protective vest, to quickly exit the vehicle. Moreover, two of the hatches are blocked by the overhang from the turret. The crews were rather amazed that all these design flaws could have occurred in the first place, and then remained through years of development. The real problem was that a lot of senior officers and civilians wanted the Mobile Gun System really, really bad. They were less concerned with crew survival.