In Space, Flames Behave in Ways Nobody Thought Possible

Combustion experiments conducted in zero gravity yield surprising results

A composite false-color image of fire in space. The bright yellow traces the path of a drop of fuel, shrinking as it burns, producing green soot. (Paul Ferkul / NASA)
Smithsonian Magazine | Subscribe

Recent tests aboard the International Space Station have shown that fire in space can be less predictable and potentially more lethal than it is on Earth. “There have been experiments,” says NASA aerospace engineer Dan Dietrich, “where we observed fires that we didn’t think could exist, but did.”

That fire continues to surprise us is itself surprising when you consider that combustion is likely humanity’s oldest chemistry experiment, consisting of just three basic ingredients: oxygen, heat and fuel.



Such fires might appear eerily tranquil to people accustomed to the capricious nature of earthly flames. But a flame in microgravity can be more tenacious, capable of surviving on less oxygen and burning for longer periods of time.

NASA has practical applications in mind with its research. Scientists hope to learn if certain materials are more flammable in space, and thus to be avoided. Experiments suggest that space station fire extinguishers that squirt gases at a flame are less effective than on terra firma, since they direct air (and oxygen) to the fire, providing additional fuel.

Moreover, the data obtained aboard the space station—through experiments such as comparing how fire spreads on flat objects versus spherical ones—will help engineers better understand the behavior of fuel and flames on Earth, where approximately 75 percent of our power comes from some form of combustion.

NASA scientists are especially excited about the potential applications for a bizarre, unprecedented type of combustion they observed in space this past spring: When certain types of liquid fuel catch fire, they continue to burn even when the flames appear to have been extinguished. The fuel combustion occurs in two stages. The first fire burns with a visible flame that eventually goes out. But shortly afterward, the fuel reignites, taking the form of “cool flames” that burn at lower temperatures and are invisible to the naked eye.

Scientists do not yet have an explanation for this phenomenon. But engineers say that if this chemical process could be duplicated on Earth, the result could be diesel engines that use cool flames to produce fewer air pollutants.

NASA researcher Paul Ferkul says the microgravity experiments provide a unique opportunity to study the underlying dynamics of fire “from a more fundamental point of view” by looking at combustion processes “that would otherwise be masked or at least complicated by gravity.”

Comment on this Story

comments powered by Disqus