Bromine-based halons, previously used to fight fires in situations where water would not be effective or appropriate-such as in computer centers, for aircraft, and in libraries and other document storage areas-were banned worldwide in 1998 because they were damaging to the earth’s ozone layer. Since then, industry has been attempting to come up with a cost-effective, environmentally friendly replacement, one will not damage property by requiring large quantities of water.
A new commercial firefighting system that was designed to put out fires with a fine water mist has been developed and will be tested on the STS-107 Space Shuttle Columbia 16-day mission in January, according to Mark Nail, director of the Space Product Development Program at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
According to Dr. Thomas McKinnon, lead scientist for research at The NASA Center for Commercial Applications of Combustion in Space at the Colorado School of Mines in Golden, water mist seems to be the best choice for replacing halon. The Center helps industry to conduct combustion research in space through NASA’s Space Product Development Program at the Marshall Center.
The Shuttle tests, according to Dr. Angel Abbud-Madrid, the project scientist at the NASA Commercial Space Center, will use “a humidifier-like device to produce water drops about 20 microns in size … about one-tenth the diameter of a human hair, as opposed to drops produced by conventional sprinklers that are about one millimeter, or 50 times the size of our droplets.”
Working with the research team on the water-mist system to be tested is MicroCool Inc., a division of Nortec Industries Inc. (Palm Springs, California), and FOGCO Systems Inc. (Gilbert, Arizona). Both companies manufacture water-mist systems for firefighting and other applications such as outdoor cooling and industrial humidification.
The information acquired from the STS-107 experiment will be used to make adjustments to the firefighting system designs, according to FOGCO President Gary Wintering. The systems create a fog instead of releasing blasts of water. The fog removes heat and replaces oxygen as the water evaporates, thereby preventing the fire from spreading.
Water-mist systems have been found to be especially effective for fires in the closed compartments of a ship, an aircraft, and even the Space Shuttle. The U.S. Navy has been working on water mist studies with the airline industry and The Center for Commercial Applications of Combustion in Space.
“Testing the system in space makes it easier to observe the interaction between a flame and water,” says Dr. Frank Schowengerdt, director of The Center for Commercial Applications of Combustion in Space. “Earth’s gravity does not cause air currents around the flame and water droplets to settle.” Abbud-Madrid adds that the Shuttle experiment will help researchers and developers to determine the optimum water concentration and water droplet size needed to suppress fires. Short tests on NASA’s KC-135 reduced-gravity aircraft and inside drop towers have shown that water mists use one-tenth the water of traditional sprinklers to extinguish a flame, he explains.
Test protocol will include igniting a mixture of propane and air inside a clear tube to produce a thin flame, known as a “laminar flame.” A water mist will be released on the opposite end of the tube. Digital images will record how different size water droplets and water concentrations affect the flame. the test will be conducted inside the safety of the Combustion Module-a NASA facility flown on a previous Shuttle flight.
Larger and longer water-mist investigations on the Space Station are planned for the future. Companies will be able to test different water injection systems, droplet sizes, and fire scenarios.
The STS-107 mission is a dedicated science mission recommended by the National Research Council and approved by the U.S. Congress.
