NASA engineers say they’re making progress in their efforts to help the U.S. Forest Service design a better emergency fire shelter for wildland firefighters.
The NASA Convective Heating Improvement for Emergency Fire Shelters or CHIEFS project started because of the deadly Yarnell Hill fire in Arizona in 2013. Nineteen firefighters were trapped in a raging, wind-driven wildfire and the emergency shelters they carried and used were unable to save them.
“When I saw that on the news, it just shook me to the core,” said Mary Beth Wusk, now the acting program manager of NASA’s Game Changing Development Program in the Space Technology Mission Directorate. “The huge loss of those firefighters made some of us at NASA think about how our research might help improve firefighter survivability.”
At the time Wusk was part of a group at NASA’s Langley Research Center in Hampton, Virginia, that is developing flexible thermal protection systems for inflatable heat shields for spacecraft. NASA Langley signed an agreement with the Forest Service in early 2015 to see if some of its space-age materials could help save firefighters’ lives.
“We’ve been able to use our decade of experience developing flexible heat shield materials, which have a lot of things in common with fire shelter materials,” said Josh Fody, CHIEFS task lead. “We have approached the challenge of designing a new shelter from an engineering perspective, starting with screening small samples of 70 materials and over 290 unique combinations of those materials.
NASA is working with the U.S. Forest Service’s Missoula Technology and Development Center (MTDC) in Montana and Fire Shelter Project leads Anthony Petrilli and Mary Ann Davies. The MTDC team had started a review of the fire shelter design and new materials technology in 2014 with the goal of producing an improved shelter by 2018.
Petrilli has personal knowledge that he can apply to the redesign. As a wildland firefighter in Colorado in 1994 he survived a blaze by using the fire shelter that was part of his gear. Seven others fighting the fire with him also lived, but 14 others did not.
“Our project is trying to take advantage of advances in materials that may offer better protection by slowing the transfer of heat through the shelter layers,” said Petrilli. So the Forest Service and NASA have been testing layered combinations or lay-ups of materials to see which might prove the most effective.
“We learned quickly we couldn’t repurpose our materials directly,” said Fody. “You can’t just take an inflatable heat shield and turn it into a fire shelter. The constraints for mass and volume are far too strict for the fire shelter world.”
Fody says the current shelters are less than a millimeter thick, weigh 4.3 pounds (1.95 kilograms) and pack into a size similar to a half gallon of milk.
“What we ended up doing was drawing more on the test experience and expertise that our senior engineers have and using that to benefit the CHIEFs project,” added Fody. “We’ve learned how to make the insulations more efficient, how to get them smaller and lighter and then we learned even more when we tested the lay-ups in the real world.”
That real world consisted of two different set-ups in Canada, where the Forest Service tests its shelters, and additional tests at North Carolina State University.
“Last summer we were in Canada at the University of Alberta,” said Wusk. “We spent three days testing 22 full-scale shelters representing nine different configurations. Four of those configurations were NASA designs.”
University researchers set up a test rig that included a small metal shed equipped with eight large propane burners. The shelters were placed inside the shed, instrumented with heat and gas measuring devices, and then torched so NASA and the Forest Service could see how well the different layups performed.
The team had already tried to assess the new designs in an actual woods fire set in a remote section of Canada’s Northwest Territories, but those tests had to be stopped when the firefighters overseeing the controlled burn were called away to fight an actual wildfire.
“I was really proud of the NASA shelters. The materials did really well,” said Wusk.
The materials proved effective, but researchers noted challenges with the actual designs during the testing. Flames ended up entering under the bottom, in part because there was no one inside holding the test shelters down. Hot gasses also penetrated the seams.
So the team came up with second-generation shelter concepts that they put through flame tests this year. The team returned to the University of Alberta in Edmonton to evaluate five concepts and then traveled closer to home to the Thermal Protection Laboratory at the North Carolina State University College of Textiles in Raleigh to assess 22 shelter prototypes over three months.
The NASA CHIEFS project, which is funded by the Game Changing Development Program in NASA’s Space Technology Mission Directorate, plans to wrap up its research this fall with more tests in Canada. Engineers expect to turn over their findings to the U.S. Forest Service by early 2017. The Forest Service has said it wants have new test shelter prototypes to firefighters by next summer and an approved updated fire shelter ready for use by 2018.