Studying the Physics of Flame Spread to Minimize Structural Fire Hazards on Earth and in Space

December 23, 2019 • By Anne Wainscott-Sargent, Contributing Author

Fire in confined spaces is inherently more dangerous than in the open, and no place is more confined than an orbiting spacecraft. This week, International Space Station (ISSInternational Space Station) crew members worked on an ISS U.S. National Laboratory experiment aimed at making structures on Earth and in space safer by examining how flame spreads in confined spaces in microgravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment..

The investigation, funded by the National Science Foundation (NSF) and led by researchers at Case Western Reserve University and the NASA Glenn Research Center, launched on SpaceX’s 19^th commercial resupply services mission(Abbreviation: CRS mission) A CRS mission is a cargo resupply mission contracted by NASA to deliver supplies and research to the International Space Station on commercial spacecraft as part of the CRS contract with three commercial companies. As part of CRS missions, experiments currently return to Earth on SpaceX Dragon spacecraft that splash down in the ocean. earlier this month.

Flames inside confined spaces such as buildings, warehouses, and spacecraft behave differently than those in open spaces and can pose a more serious fire hazard because they spread faster and hotter than in open fires. In 2017, a tragic fire at the 24-story Grenfell Tower apartments in London is believed to have spread rapidly in a confined space on the building exterior, resulting in the deaths of 72 residents.

“Because the flames are in a confined space, the expanding hot gases have no place to go, which makes the fire dramatically more dangerous,” said Principal Investigator Dr. Ya-Ting Tseng Liao of Case Western Reserve University.

In the United States, nearly two in five fires occur inside structures, which catch fire at a rate of one every 63 seconds, according to a 2018 report from the National Fire Protection Association. Better understanding what factors can accelerate a fire—such as the type of construction material and how the material is spaced between air gaps—could help builders and engineers make safer material and design decisions not only for buildings on Earth but also for future space habitats.

Studying fire in space has advantages over studies on Earth. On the ground, buoyancy caused by the pull of gravity displaces hot air, causing it to rise upward in a turbulent flow. Whereas, in space, heated air expands uniformly and doesn’t flow in any singular direction.

“When you remove the confounding factors of buoyancy, you can more easily study the underlying physics of fire,” explained Liao.

The research team anticipates that under certain confinement conditions, flames will grow more quickly. Studying flame spread on the ISS National Lab will help the team learn:

• Under what types of confinement will flame accelerate?
• How does gap spacing (the distance between a combustible solid and a surrounding wall) affect flame spread?
• As the gap space is squeezed tighter, how will radiation from the flame be reflected from the surrounding walls?
• How will radiation feedback from the surrounding walls alter the fire behavior?

Studying Flame Spread in Space

ISS crew members need not worry about fire escaping during the experiment: The tightly controlled tests will run inside a miniature wind tunnel enclosed inside a science glovebox, providing two levels of containment.

Photo courtesy of NASA Glenn Research Center

The investigation will test two materials: a cotton blend fabric used in astronaut suits and a type of plastic called polymethyl methacrylate (PMMA). The researchers will rely on a computational model at Case Western Reserve University to guide and validate their findings. Built on many layers of data, this three-dimensional, high-resolution model simulates the flames to model the experiment in space and on Earth.

Results from this investigation could enable better material choices and gap spacing in building construction on Earth to help prevent catastrophic fires. The research could also influence the design of spacecraft components to avoid gap spacings that would be hazardous in the event of a fire, observed Co-Principal Investigator Dr. Paul Ferkul of the NASA Glenn Research Center.

“The immediate goal is how to make habitats for astronauts or other off-world habitats safer from a fire safety point of view,” Ferkul said.