OVIEDO, Fla., 24 May 2010. The latest generation of U.S. laser weapons is providing warfighters with giant improvements in capability, but these directed-energy weapons also are giving weapons-grade laser systems designers with substantial challenges when it comes to the thermal management and cooling technologies necessary to keep laser weaponry cool enough to avoid malfunctions and early wearout.
"Lasers produce an incredible amount of laser power to destroy their targets, but they produce a ridiculous amount of heat," says Dr. Dan Rini, president of RINI Technologies in Oviedo, Fla. "They produce 5 to 10 times as much heat as they do laser beam power. They make a lot of heat is the problem," he summarizes. (See related story, Laser weapons development is pushing laser technology out of the laboratory and into directed-energy weapons applications in the field)
The laser divisions of some large companies -- such as Northrop Grumman, Textron, and Boeing -- have developed "very powerful lasers that can shoot down missiles and burn holes in things," Rini explains. Current solid-state laser systems "are relatively compact -- the size of a couple large office desks."
The laser system might be very compact, but the cooling system required is much bigger and can take up most of the airplane or ground vehicle upon which is to be deployed. "They can fit the laser on the airplane rom a size and weight point of view," Rini says, "but the cooling system doesn’t fit because the water chillers are extremely large. Instead of inventing this flying refrigerator to keep the laser cool, we have developed two technologies that solve two different problems."
In a nutshell, a laser will shoot at a target for a short period of time and then be off for a much longer period of time, Rini explains.
"The laser only comes on for a short period of time but, during that time, it produces an incredible amount of heat," Rini notes. "We have thermal energy storage technology that can store the heat that the laser generates during those short bursts and then slowly rejects it through the aircraft’s cooling system over a longer period of time that it takes to fly to a new area.
"It has been developed through Technology Readiness Level 5; it has been proven in lab environments and interfaced with laboratory lasers, and it is ready to be integrated with a laser demonstrator when appropriate," Rini says.
RINI Technologies’ second laser cooling innovation for directed-energy weapons gets inside the laser to cool the laser components with evaporative spray cooling. Spray cooling is conducive to a compact system. "Nobody wants a laser that is like a flying laboratory; they want a laser that is compact, lightweight, and efficient," Rini mentions. "Evaporative spray cooling can reduce the size and weight of the cooling systems by factors of 3 or 4.
"If you look at the whole laser system, the biggest, heaviest part is typically the cooling system; and when you want to fly it, put it on a Humvee, or put it in a military environment, you have to carry everything," Rini explains. The power supply typically comes in at a close second, and the laser is likely the lightest element. "So the power and the cooling are huge slices of the pie when it comes to the size, weight, and power of a laser system."
