Gui Haichao and Zhu Yangzhu from China’s Tiangong space station light a candle while giving a livestream lecture to viewers. Their goal was to show how flame moves in the space environment. As hot gases from flames rise on Earth, gravity pulls cooler, denser air towards the bottom of the flame. In the microgravity environment of a space station, this does not happen and the flame becomes spherical.
While great for spectacle, flame and space don’t pair well. An actual fire broke out on Mir in 1997, lasting several minutes and cutting off access to one of the Soyuz escape vehicles docked with the space station. The crew managed to extinguish the fire, but the situation was quite dangerous for a while.
European Space Agency (ESA) astronaut Reinhold Ewald said the following about the incident: “The fire was so big and the smoke and steam coming out of the fire area was so much that we could not even see in front of us, and I could not even imagine that we could continue the mission at that moment.”
Another problem with flames on space stations is that the zero-gravity environment makes it difficult to detect flames.
Guillaume Legros from the Institut de Combustion Réactivité et Environnement in France told ESA that as the gravitational field decreases on Mars (0.38 g) or the Moon (0.16 g), the buoyancy force will decrease and it will not be compatible with normal equipment. The typical time it takes to detect a fire will also increase, he says. To make matters worse, there is no buoyancy on a spacecraft, and smoke consequently follows the complex air movement imposed by the ventilation system, leading to a longer fire detection time by smoke detectors typically placed along the ventilation lines.
In case of a fire, cosmonauts in the Russian section of the International Space Station (ISS) have water-based fire extinguishers, while the US section has a carbon dioxide extinguisher.
“Of course, we have to be careful when using the fire extinguisher to either secure ourselves to a wall or have a second astronaut stand behind us and hold us in place,” ESA astronaut Matthias Maurer says in a video by the German Space Agency.
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