Jellyfish flames on the ISS

September 11, 2014 by Dr. Tony Phillips, NASA
Jellyfish flames on the ISS

Fire is inanimate, yet anyone staring into a flame could be excused for thinking otherwise: Fire dances and swirls. It reproduces, consumes matter, and produces waste. It adapts to its environment. It needs oxygen to survive.

In short, fire is uncannily lifelike.

Nowhere is this more true than onboard a spaceship.

Unlike flames on Earth, which have a tear-drop shape caused by buoyant air rising in a gravitational field, flames in space curl themselves into tiny balls. Untethered by gravity, they flit around as if they have minds of their own. More than one astronaut conducting experiments for researchers on Earth below has been struck by the way flameballs roam their test chambers in a lifelike search for oxygen and fuel.

Biologists confirm that fire is not alive. Nevertheless, on August 21st, astronaut Reid Wiseman on the ISS witnessed some of the best mimicry yet.

"It was a jellyfish of fire," he tweeted to Earth along with a video. Wiseman was running an experiment called FLEX-2, short for Flame Extinguishment Experiment 2. The goal of the research is to learn how fires burn in microgravity and, moreover, how to put them out. It's a basic safety issue: If fire ever breaks out onboard a spacecraft, astronauts need to be able to control it. Understanding the physics of flameballs is crucial to zero-G firefighting.

"Combustion in microgravity is both strange and wonderful," says Forman Williams, the PI of FLEX-2 from UC San Diego. "The 'jellyfish' phenomenon Wiseman witnessed is a great example."

A new ScienceCast video looks at the lifelike behaviour and underlying physics of jellyfish flames on the ISS.

He points out some of the key elements of the video:

"Near the beginning we see two needles dispensing a droplet mixture of heptane and iso-octane between two igniters. The fuel is ignited … then the lights go out so we can see what happens next."

"The flame forms a blue spherical shell 15 to 20 mm in diameter around the fuel. Inside that spherical flame we see some bright yellow hot spots. Those are made of ."

Heptane produces a lot of soot as it burns, he explains. Consisting mainly of carbon with a sprinkling of hydrogen, soot burns hot, around 2000 degrees K, and glows brightly as a result.

"Several globules of burning soot can be seen inside the sphere," he continues. "At one point, a blob of soot punctures the flame-sphere and exits. The soot that exits fades away as it burns out."

There is also an S-shaped object inside the sphere. "That is another soot structure," he says.

The 'jellyfish phase' is closely linked to the production of soot. Combustion products from the spherical flame drift back down onto the fuel droplet. Because sooty material deposited on the droplet is not perfectly homogeneous, "we can get a disruptive burning event," says Forman. In other words, soot on the surface of the fuel droplet catches fire, resulting in a lopsided explosion.

Remarkably, none of this is new to Forman, who has been researching combustion physics since the beginning of the Space Age. "We first saw these disruptive burning events in labs and microgravity drop towers more than 40 years ago," he says. "The space station is great because the orbiting lab allows us to study them in great detail."

"Tom Avedisian at Cornell is leading this particular study," Forman says. "We're learning about droplet burning rates, the soot production process, and how soot agglomerates inside the flame."

At the end of Wiseman's video, the soot ignites in a final explosion. That's how the put itself out.

"It was a warp-drive finish," says Wiseman.

Explore further: Space image: Burning

Related Stories

Space image: Burning

May 26, 2011

(PhysOrg.com) -- Because of the absence of gravity, fuels burning in space behave very differently than they do on Earth. In this image, a 3-millimeter diameter droplet of heptane fuel burns in microgravity, producing soot. ...

FLEX-ible insight into flame behavior

November 30, 2011

(PhysOrg.com) -- Whether free-burning or smoldering, uncontrolled fire can threaten life and destroy property. On Earth, a little water, maybe some chemicals, and the fire is smothered.

Space Image: Aflame

June 24, 2011

Fire acts differently in space than on Earth. Sandra Olson, an aerospace engineer at NASA's Glenn Research Center, demonstrates just how differently in her art. This artwork is comprised of multiple overlays of three separate ...

Is it safe to breathe yet?

April 26, 2010

Anyone who has ridden behind a truck belching black exhaust knows the smell and discomfort caused by soot, the airborne carbon particles that result from the incomplete combustion of hydrocarbons such as diesel fuel. Those ...

Recommended for you

Birth of massive black holes in the early universe revealed

January 23, 2019

The light released from around the first massive black holes in the universe is so intense that it is able to reach telescopes across the entire expanse of the universe. Incredibly, the light from the most distant black holes ...

Astronomers discover an unusual nuclear transient

January 23, 2019

An international group of astronomers has detected an unusual nuclear transient in the nucleus of a weakly active galaxy. The new transient was identified by the OGLE-IV Transient Detection System and received designation ...

Scientist sheds light on Titan's mysterious atmosphere

January 23, 2019

A new Southwest Research Institute study tackles one of the greatest mysteries about Titan, one of Saturn's moons: the origin of its thick, nitrogen-rich atmosphere. The study posits that one key to Titan's mysterious atmosphere ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

axemaster
5 / 5 (2) Sep 11, 2014
I love that phrase "Biologists confirm that fire is not alive".
d_robison
not rated yet Sep 15, 2014
I love that phrase "Biologists confirm that fire is not alive".


Haha, that gave me a good laugh to start the day :).

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.