Recent progress, including the Artemis II flight, shows that humans can safely return near the Moon. Yet a critical safety gap persists. Scientists still do not fully understand how fire spreads in environments with weaker gravity than Earth’s, a concern for planned lunar habitats.
Fire represents one of the most immediate dangers in space missions. Inside spacecraft or habitats, a small ignition can quickly become uncontrollable. NASA researchers aim to address this issue by studying combustion directly on the Moon rather than relying only on Earth-based simulations.
A Safety Standard That Was Never Built for Space
On Earth, flames are shaped by gravity. Hot gases rise while cooler air moves in, creating a steady flow that feeds combustion. This process produces the familiar teardrop-shaped flame seen in everyday conditions.
In microgravity, that mechanism changes completely. Flames become slower and more spherical because there is no upward flow to sustain them. NASA has already studied these effects through drop towers and experiments conducted near the International Space Station, where only brief periods of weightlessness are available.
Flame ignited as part of the Flame Design investigation on the International Space Station – © NASA
According to ZME Science, current safety standards such as NASA-STD-6001B rely on tests performed under Earth gravity. Materials are exposed to a six-inch flame, and their behavior determines whether they are considered safe for spaceflight. This method assumes that materials passing Earth-based tests will behave similarly in space, an assumption now being questioned.
The Moon’s Partial Gravity Could Be the Most Dangerous Scenario of All
The Moon presents a unique environment, with gravity at about one-sixth of Earth’s. This is stronger than microgravity but still significantly weaker than conditions on Earth. That difference introduces unexpected behavior in flames.
Researchers suggest that this intermediate gravity could make some materials more flammable. The airflow is strong enough to feed a fire but not strong enough to extinguish it through a process known as blowoff, where rapid airflow disrupts combustion.
Top: FM2 experiment design showing solid model and cross section of the combustion chamber. Four flat samples are burned in separate tests. Small,pressurized gas bottles provide air for each test. Cameras record flame images while sensors include thermocouples, radiometers, and O2 concentration. Bottom: FM2 Hardware. Left: Chamber exterior; Right: Internal components – © NASA
According to NASA researchers cited in the report, materials considered marginally non-flammable on Earth might ignite more easily in lunar conditions. The slower airflow allows chemical reactions to keep pace with oxygen supply, potentially sustaining combustion longer than expected.
A Robot Will Light the Matches And Cameras Will Watch Closely
To study these effects directly, NASA has developed the Flammability of Materials on the Moon mission, known as FM2. The experiment is scheduled for a launch no earlier than late 2026.
The mission will send a sealed, robotic chamber to the Moon. Inside, four solid fuel samples will be ignited under controlled conditions. Instruments including cameras, radiometers, and oxygen sensors will monitor flame behavior over extended periods.
According to NASA researchers, these tests are intended to provide benchmark data on how lunar gravity influences fire. The findings will support the development of safer materials for future missions, especially as astronauts may live in oxygen-enriched environments that can make combustion easier to sustain.
The experiment addresses a practical limitation: full-scale fire testing cannot yet be performed on the Moon. While broader studies will require a sustained human presence, early results from FM2 could answer a key question, whether materials considered safe on Earth remain safe in lunar habitats.