Starting Fire in Water: Investigating Supercritical Water in Space for Earth Applications

Astronauts on the International Space Station (ISS) are experimenting with a form of water called supercritical water that a strange property - it can help start fire. Above the critical temperature of 705 degrees Fahrenheit, water behaves like a dense gas where its distinct liquid and vapor phases no longer exist. At this point, any salt in the water is no longer soluble so it precipitates from the water and attaches itself to surfaces like heating coils and pipes. To study this phenomenon, the Supercritical Water Mixture (SCWM) investigation currently is running aboard the ISS. "By studying supercritical and near-critical water without the effects of gravity, we'll look at how salt precipitates on a very fundamental level," says Mike Hicks of NASA's Glenn Research Center. Learning how to use water efficiently in its supercritical phase is of great interest to researchers since many waste streams - like city sewage, agricultural wastes, and paper mill wastes - contain water. SCWO provides a way to oxidize sewage in a closed system that will burn out all the organics in a wet waste stream. The combustion products are also relatively benign compared with incineration, which produces sulfur and nitrogen oxides. The SCWO processing of an organic waste stream should leave behind only carbon dioxide and water.