Clean technology in 'hot water'

The experiment, called DECLIC-HTI, is studying supercritical water that could lead to spin-offs in the field of clean technologies for treating waste here on Earth.

A supercritical fluid is any substance at a temperature and pressure above its critical point -- the point at which the fluid is one homogeneous phase and exhibits properties of both liquids and gases. In this form, the substance can flow through solids like a gas and dissolve materials like a liquid. Water and carbon dioxide are the most commonly used supercritical fluids. Using extremely high temperatures, supercritical water can completely break down waste into benign forms.

DECLIC, or DEvice for the study of Critical LIquids and Crystallization, is a miniaturized, automatic thermo-optical laboratory that studies transparent fluids by finely tuning the temperature of a sample and sending images and video to the ground. The HTI, or high temperature insert, can measure fluid temperatures up to 400 degrees Celsius.

For the experiment, astronauts plug an insert, containing the water sample cell, into the DECLIC payload. The sample is precisely heated and observed in real time by investigators on the ground.

"These phenomena will be of interest to understand the behavior of supercritical fluids in space, but also to improve industrial processes on the ground," said Gabriel Pont, DECLIC mission manager with the CNES, or Centre National d'Etudes Spatiales, in Toulouse, France.

"A typical example is burning completely organic or industrial waste in supercritical water at a much lower temperature than in conventional systems, thus saving energy and being cleaner. Microgravity will provide the ideal environment to understand how to do that."

The supercritical water temperature is very sensitive to gravity and has never been measured in microgravity conditions. "We expect HTI to give us the best measurement of this temperature ever found," added Pont.

The experiment began in October 2009 when the High Temperature Insert commissioning was performed. Since then, four experimental sequences have been performed, leading to more than 80 running days. "We are very excited about what we've seen thus far, and cannot wait to see the potential benefits of our work on Earth," added Pont.