Astronauts aboard NASA’s International Space Station (ISS) intentionally started fires in space in order to study how flames react in microgravity. The experiment was also conducted to identify ways of making combustion cleaner.

For the experiment, the astronauts used a special onboard equipment known as the Combustion Integrated Rack (CIR). Through the CIR, the astronauts on ISS were able to start fires in a safe and controlled manner.

According to NASA, the microgravity conditions in the ISS had a huge impact on the fires they created. Unlike fires on Earth, which move upwards and form an almost triangular shape, flames in space have spherical structures.

The astronauts explained that fire moves away from its source or epicenter as the hot gas expands due to the lack of gravity. Based on the images provided by NASA, the fire the astronauts created looked like a swarm of fireflies moving in a circular formation.

Through the experiment, the astronauts were able to understand how fires react in space. Aside from the fire’s unusual shape, they noticed that the soot remains longer within the flame in space than on Earth. Soot comes from the incomplete burning of organic matter. It is the carbon by-product of combustion that has negative environmental effects.

Through the CIR as well as another study known as the Advanced Combustion via Microgravity Experiments (ACME), NASA was able to understand how environmental conditions influence how much soot is produced by fires.

“It turns out, it has a big impact on the flame,” ACME’s principal investigator Richard Axelbaum said. “In this case, even though the temperatures of the flames may be the same whether you introduce the inert with the oxidizer or the fuel, the impact for soot formation or flame strength is substantially different.”

In addition to finding ways to make cleaner combustions, NASA also gained a deeper understanding of how fires work in space. With this information, the agency will be able to develop effective methods in suppressing accidental fires in space. According to the agency, this will serve as a crucial safety aspect for the ISS as well as future human colonization missions on the Moon and Mars.

space-flame This flame was one of many ignited as part of the Flame Design investigation inside of CIR to investigate the amount of soot that is produced in different conditions. The yellow spots are soot clusters that glow yellow when hot. These clusters grow larger in microgravity than on Earth because the soot remains within the flame longer. Photo: NASA