When engineers at NASA's Glenn Research Center in Cleveland sat down to prepare humanity's return to the Moon, they knew they'd face a problem that keeps mission planners up at night: fire. Not the dramatic, out-of-control blazes Hollywood loves—but the quiet, invisible danger that could threaten a sealed habitat millions of miles from the nearest fire station. Now, their solution is literally heading to the lunar surface.
The team has spent decades relying on NASA-STD-6001B, a standardized test that holds a six-inch flame to the bottom of a material mounted vertically. If the material burns more than six inches upward, or drips burning debris, it fails the test. Simple enough—but here's the catch: that test was designed for Earth. And Earth, it turns out, is a very unusual place when it comes to fire.
On our planet, gravity pulls hot gases upward, creating convection currents that feed fresh oxygen into flames. In some cases, that rush of air can actually blow a small fire out entirely—a phenomenon called "blowoff." But in the International Space Station's microgravity, fires don't point upward at all. They form eerie spherical blobs that spread slowly outward, almost entirely dependent on the station's ventilation systems for oxygen.
Researchers have studied this phenomenon before. The Saffire experiments ignited large sheets of cotton, fiberglass, fabric, and acrylic inside uncrewed Cygnus cargo capsules after they'd detached from the ISS, watching them burn before the capsules tumbled back into Earth's atmosphere. During one series of tests, they deliberately lit 1,500 smaller fires just to understand how combustion behaves without gravity's influence.
But microgravity isn't quite the same as lunar gravity, which is one-sixth of Earth's—a condition impossible to recreate anywhere on our planet. The FM2 experiment, formally called Flammability of Materials on the Moon, will soon change that. When it launches aboard a Commercial Lunar Payload Service mission, a self-contained chamber aboard will burn four solid fuel samples in long-duration lunar gravity for the first time, equipped with cameras, radiometers, and oxygen sensors to monitor every flicker.
What they've already predicted is striking: on the Moon, that convective flow still exists, but it moves much more slowly. Oxygen gets continually resupplied to the flame without creating the fast vapor movement needed for blowoff. The practical result? Materials that would safely self-extinguish on Earth might burn for a very long time in a lunar habitat. By mapping exactly how that works, the FM2 team hopes to design those habitats—and the materials inside them—before a single astronaut sets foot inside.
"Materials that might not truly be flammable on Earth could burn for a very long time on the moon," the researchers noted in their paper, a collaboration between NASA's Glenn Research Center, Johnson Space Center, and Case Western Reserve University. That's not a reason to panic; it's a reason to test. And now, finally, they can.