Fire behaves very differently in microgravity — and this ISS experiment shows it beautifully. 🔵 With no “up” in 0g, hot gases don’t rise, so the flame becomes a perfect sphere. Combustion completes more cleanly, giving the flame its blue color. When you see sudden orange patches, that’s soot forming — a brief moment of incomplete burning, similar to flames on Earth. As the droplet burns, tiny asymmetries push it gently through the air until the fuel is gone and the flame silently disappears. |

What happens when fire burns in space? A fascinating experiment aboard the International Space Station (ISS) reveals that in microgravity, flames behave in ways impossible on Earth. Using a 50/50 mix of iso-octane and heptane, scientists observed something striking: a nearly perfectly spherical flame. Why? On Earth, hot air rises, shaping flames into the flickering, teardrop forms we’re used to. But in zero gravity, there’s no “up”—so the flame expands symmetrically in all directions. The result