NASA to adapt heat shield technology to fire shelters

Researchers are looking into flexible, high-temperature space materials for personal fire shelters; the project is expected to finish up in 2018

October 26, 2015 08:44 AM

Daily Press

HAMPTON, Va. — When 19 Granite Mountain Hotshots were trapped by a raging wildfire in Arizona in 2013 and died inside their emergency shelters, Mary Beth Wusk took notice.

Then she took action.

A materials expert at NASA Langley Research Center in Hampton, Wusk and her team develop new flexible heat shield technologies for spacecraft that must withstand blistering thermal loads on reentry.

“I talked to the team — is there any chance that we can take the technology that we’re developing for the heat shields and transfer them to an application for the fire shelters for entrapment situations?” Wusk recalled recently.

Then they reached out to the U.S. Forest Service, whose National Technical and Development Center was also working on a fast-tracked redesign of its shelters after the Arizona wildfire tragedy.

“It was a welcome inquiry from NASA,” said Anthony Petrilli, a fire shelter project lead with the Forest Service center in Missoula, Mont. “I knew it would be a great entity to extract some technology and some materials and just some intelligence from, that’s for sure.”

Now the two agencies are partnering to incorporate next-generation space technologies into emergency shelters in an effort to better protect firefighters in the future.

Fire shelters now
A fire shelter is rarely put to use. But when it is, it’s typically a matter of life and death: to protect a trapped firefighter from smoke or ember showers and from heat from wildland fires that can reach a searing 2,000 degrees Fahrenheit.

NASA Langley’s research into flexible thermal protection systems for inflatable heat shields, the light pink cover seen here during testing in 2012, spurred the partnership with the U.S. Forest Service that could result in space-age technology being used in personal fire shelters.

Since the 1960s, Petrilli said, emergency shelters have saved the lives of more than 350 firefighters. In 1994 outside Glenwood Springs, Colo., he said, he deployed one himself in a burned-out area to escape heavy smoke and a big ember shower.

According to Forest Service guidelines, shelters must be rapidly deployable — unfold, “shake out,” climb inside and lie flat.

They must be portable, which means as lightweight as possible, ideally about 4 pounds, since firefighters are required to lug them around along with about 40 pounds of other essential gear while they operate for days and weeks at a time in hot, difficult and dangerous terrain.

And, just as critically, they must be cost-effective.

Building a better fire shelter that’s also practical, then, isn’t as simple as it may sound.

“We couldn’t just take a flexible heat shield material and literally stick it to a fire shelter template,” said Josh Fody, a thermal analyst at NASA Langley. “So we began developing our own lighter, thinner insulations that were more targeted for the fire shelter applications.”

The current fire shelter used by the Forest Service was introduced in 2003, and at the time represented the best available combination of design and materials.

It’s comprised of two layers: an outer layer of woven silica laminated to aluminum foil to reflect radiant heat and slow any heat transfer to the inside, and an inner layer of fiberglass laminated to aluminum foil to keep out re-radiated heat and toxic gases. It’s shaped like a long half-cylinder with rounded ends.

The shelter works great in radiant heat situations, or when it’s not in direct contact with flames, said Petrilli. But it’s much less effective with convective heat, when flames contact the shelter directly.

For that reason, firefighters are trained to deploy shelters in areas that are clear of brush and other fuels that can feed a fire, and away from steep slopes and draws.

It was convective heat, said Petrilli, that doomed the Granite Mountain crew battling the fire at Yarnell Hill, Ariz.

“There was just heavy brush in the area,” Petrilli said. “Firefighters were not able to find a large enough clearing. And 50-mile-an-hour winds pushing flames pretty much parallel to the ground. And just, basically, in nonscientific terms, a ton of red-flame contact.”

Building a better one
The original Forest Service timeline called for a product review of its emergency shelter system beginning in 2015 to identify any possible improvements in materials, design or training. But that timeline was stepped up by a year after Yarnell Hill.

To help with that effort, the NASA Langley specialists screened about 200 sample materials, then presented the most feasible to Petrilli’s team, which has been working on its own designs.

They call their partnership Convective Heating for Improvement for Emergency Fire shelters, or CHIEFS. Fody is the team led.

This summer, the CHIEFS team joined with the University of Alberta in Edmonton, Canada, to conduct real-fire tests on 22 full-scale shelter prototypes in a remote region of Canada’s Northwest Territories. Each shelter was instrumented inside and out to see how it performed.

“The big, eye-catching test is the full-scale fire shelter flame test,” said Petrilli. “And it’s basically blasting a fire shelter with direct flame contact on a test stand.”

The 22 shelters represent nine unique designs, said Fody. Eight of the shelters were NASA Langley’s, representing four unique designs, built by S.D. Miller and Associates PLLC, in Flagstaff, Ariz.

One of those designs had the same shape and weight as the current shelter, while one weighed a bit more. A third is more a thermal pod — a stockier, shorter structure that would require less surface area and thus could be made of a heavier, more protective material. The fourth design, said Wusk was a heavier, tougher shelter that could be stored in a truck rather than carried by a firefighter.

Wusk and Fody are meeting with Petrilli in Montana this week to go over the test results. They’ll also be making plans for more tests in April, said Wusk.

“We all want to work together to make sure we’re getting the best product,” Wusk said. “This is something that’s changing people’s lives.”

The fire shelter project is expected to finish up in 2018.