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)