Starting Fire With Water   
       
   Jan. 10, 2014:  When firefighters want to extinguish a blaze, they often douse   
   it with water. Astronauts on board the ISS, however, are experimenting with a   
   form of water that does the opposite.  Instead of stopping fire, this water   
   helps start it.   
       
   "We call it `supercritical water,'" says Mike Hicks of the Glenn Research   
   Center in Ohio. "And it has some interesting properties."   
       
   http://www.youtube.com/watch?v=TysrIYJOlpk   
       
   A new ScienceCast video explores the unfamiliar properties of supercritical   
   water.   Play it   
       
   Water becomes supercritical when it compressed to a pressure of 217   
   atmospheres and heated above 373o C. Above that so-called critical point,   
   ordinary H2O transforms into something that is neither solid, liquid, nor   
   gas.  It's more of a "liquid-like gas."   
       
   "When supercritical water is mixed with organic material, a chemical reaction   
   takes place-oxidation." Says Hicks.  "It's a form of burning without flames."   
       
   This really comes in handy when you want to get rid of certain unpleasant   
   materials--like sewage.  Cities, corporate farms, ships at sea and manned   
   spacecraft accumulate waste materials that could benefit from this kind of   
   treatment.   
       
   Auroras Underfoot (signup)"When we push a wet waste stream above the critical   
   point, supercritical water breaks the bonds of the hydrocarbons. Then, they   
   can react with oxygen." In other words, the slurry ignites. Sometimes,   
   hotspots in the slurry produce visible flame, but usually not. "This is a   
   relatively clean form of burning that produces pure water and carbon dioxide,   
   but none of the toxic products of ordinary fire."   
       
   What does all of this have to do with the ISS? "The International Space   
   Station provides a unique microgravity lab for studying the properties of   
   supercritical water," explains Hicks.   
       
   http://www.nasa.gov/mission_pages/station/research/news/SCWM/   
       
   More than an image   
       
   This is the rack onboard the ISS where the Super Critical Water Mixture   
   experiment takes place.  MoreOne of the problems with supercritical water has   
   to do with salt.  Above the critical point, any salts dissolved in water   
   quickly precipitate out.  If this happens in a reactor vessel, the metallic   
   components of the vessel become coated with salt and they begin to corrode.   
       
   "In any realistic waste stream, we have to learn how to deal with salt. It's a   
   major technological hurdle."   
       
   Dealing with salt is the ultimate goal of the Super Critical Water Mixture   
   experiment on the ISS, a joint effort between NASA and CNES, the French space   
   agency.   
       
   "By studying supercritical water without the complicating effects of gravity,   
   we can learn how precipitating salts behave on a very fundamental level," says   
   Hicks, who is the principal investigator of the experiment. "We might even be   
   able to figure out how to draw salt away from corrosion-sensitive components."   
       
   The experiment, which uses French-built hardware (DECLIC) located in the   
   station's Japanese Experiment Module (JEM), began during the first week of   
   July 2013.  It will continue for a full year in a series of six test runs,   
   each lasting approximately 15 days.   
       
   The results could have down-to-Earth applications. The US Navy has already   
   started using supercritical water technologies to purify waste streams onboard   
   some of their ships, while the City of Orlando has started a supercritical   
   treatment plant for processing municipal sludge.   
       
   Says Hicks, "we're just getting started."   
       
   Credits:   
   Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.98   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)