It sounds like fodder for a campy sci-fi flick or one of those heady moments when you’ve been chilling too hard with the reggae eel: What does fire do in zero gravity? The intrepid scientists have been testing exactly that in the International Space Station, and have observed zero-gravity flames that shouldn’t be able to exist. The image above, which you can see in full, shows a space fire in false color. Taken by NASA researcher Paul Ferkul, it shows a drop of fuel burning and shrinking in yellow, surrounded by soot in green.
I found the image via a new Smithsonian article that looks in depth at NASA’s current flame research:
Here on Earth, when a flame burns, it heats the surrounding atmosphere, causing the air to expand and become less dense. The pull of gravity draws colder, denser air down to the base of the flame, displacing the hot air, which rises. This convection process feeds fresh oxygen to the fire, which burns until it runs out of fuel. The upward flow of air is what gives a flame its teardrop shape and causes it to flicker.
But odd things happen in space, where gravity loses its grip on solids, liquids and gases. Without gravity, hot air expands but doesn’t move upward. The flame persists because of the diffusion of oxygen, with random oxygen molecules drifting into the fire. Absent the upward flow of hot air, fires in microgravity are dome-shaped or spherical—and sluggish, thanks to meager oxygen flow. “If you ignite a piece of paper in microgravity, the fire will just slowly creep along from one end to the other,” says Dietrich. “Astronauts are all very excited to do our experiments because space fires really do look quite alien.”
The result is that space flames can burn on much less oxygen than we expect on Earth, which means fires that burn longer. One aim of NASA’s fire experiments is to figure out ways of burning things more efficiently here on Earth — which has big potential when you consider the vast majority of Earth’s energy production is still based on lighting stuff on fire. To that end, Ferkul ran NASA’s Burning and Surpression of Solids experiments, which looked at the burning and extinction characteristics of a number of fuels burnt in space, including the ball below, which was made of the thermoplastic that Plexiglas is made of).
Of course, testing fires in space wouldn’t be complete without looking at how to extinguish them. To that end, NASA’s Flame Extinguishment Experiment was designed to look at various methods for fighting microgravity fires. Using a rather complicated-looking apparatus, the team ignited fuel droplets that produced stunning spherical flames. But while extinguishing flames is safe, watching space flames burn is the cool part. For more info on NASA’s space fire work, check out the video below.
Follow Derek Mead on Twitter: @derektmead.