Jellyfish Flames on the ISS   
       
   Sept. 10, 2014:  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.   
       
   http://www.youtube.com/watch?v=bE13FREpFVo&feature=youtu.be   
       
   A new ScienceCast video looks at the lifelike behaviour and underlying physics   
   of jellyfish flames on the ISS. Play it   
   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."   
       
   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."   
       
   http://tinyurl.com/mowyyqw   
       
   Click to visit the FLEX-2 home page.   
       
   "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 soot."   
       
   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 fire put itself out.   
       
   "It was a warp-drive finish," says Wiseman.   
       
   For more amazing tweets from the ISS, follow Wiseman @astro_reid.   
       
   Credits:   
   Author: Dr. Tony Phillips |  Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More information:   
       
   Flame Extinguishment Experiment -- FLEX home page   
       
   More information about FLEX -- from the Glenn Research Center   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.99   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)