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There is one particular challenge facing human missions in the near future that most terrifies mission planners. It’s a fire.<\/p>\n
A new paper by researchers at NASA’s Glenn Research Center, Johnson Space Center, and Case Western Reserve University details a planned mission to test the flammability of materials on the moon’s surface, where flames are expected to behave very differently than on Earth.<\/p>\n
On Earth, gravity causes hot gases to rise and draw fresh, cool oxygen to the base of the flame. If the material is slightly flammable, a phenomenon called “blow-off” may occur and actually extinguish the fire.<\/p>\n
Such flows exist on the Moon, but they are much slower, so oxygen is continually resupplied to the flames without causing a fast enough movement of steam to allow blowout conditions.<\/p>\n
In other words, materials that aren’t actually flammable on Earth can burn for a very long time on the Moon.<\/p>\n
Future lunar explorers don’t want heavy fires in their habitats for obvious reasons. Therefore, given the deadline for when we will be permanently stationed on the moon, it is better to figure out how to prevent fires sooner rather than later.<\/p>\n
For decades, we have relied on a NASA test known as NASA-STD-6001B to screen the flammability of materials for flight. But space is much more complex than experiments on Earth.<\/p>\n
To understand the problem, it helps to first understand the test.<\/p>\n
NASA-STD-6001B requires a 6-inch flame to be maintained at the bottom of the vertically mounted material. If the material flares up more than 6 inches from the bottom or drips burning debris, the material fails the test. Sounds reasonable enough, but there’s a catch. The test will take place on Earth.<\/p>\n
In the global environment, air moves around causing convection. There is also “up” and “down”, but in an environment like the International Space Station, such directions do not exist.<\/p>\n
As a result, fires do not point “up” in a microgravity environment. The fire forms a spherical mass of flame that slowly spreads outward, almost entirely fed by the station’s ventilation system.<\/p>\n