According to Walter Teal, an engineer in Natick's micro-climate lab, throughout the U.S. Army in 2005 there were six heat-related deaths, 1,400 cases of heat exhaustion, and 2,500 cases of heat stroke. It's bad enough if a Soldier collapses on the ground, but the consequences can be even worse for Soldiers behind the controls of the Army's helicopters.
Natick engineers listened to the feedback from pilots operating in the hot environments of Iraq and Afghanistan and, with the assistance of private contractors, designed and produced "liquid-cooled underwear." Basically, the garment is a vest the pilots wear that hooks into a cooling system integrated into the helicopter. The system is comprised of a lunchbox-sized black box that houses the liquid cooling components, a series of tubes routed to each pilot's seat, a quick-disconnect fitting that allows the pilot to egress without worrying about reaching down to detach the vest, and the vest itself.
As with any airplane that has systems added to it as it continues its service life, finding the real estate to house the black box (one for each crew member) and tubing was an issue. The Blackhawk has six feet of tubing between the cooling unit and the respective seat; the Chinook has twenty-two feet of tubing. But whatever the design challenges have been along the way, the helicopter pilots have seemed happy with the results. One went so far as to proclaim the liquid cooled underwear system as "the best thing to happen to helicopters since the rotor."
And Natick isn't forgetting the guys on the ground either. They're in the process of testing two different types of individual cooling units. One is a single 1.5 liter cylinder that weighs four pounds, the other is a pair of brick-sized devices, one housing the compressor, the other housing the fan and condenser - not unlike the HVAC system in many homes. The units are designed to be worn at the hip. Both units are hoping to meet Military Standard 810 (duh . . .), which of course states that these sorts of devices have to provide 120 BTUs/hour of cooling. Both units provide about four hours of cooling.
The Navy's approach to the overheated personnel issue is a bit more basic. Blessed with the luxury of freezers on ships, they simply use Steele vests, which are nothing more than vests with pouches that hold ice packs.