MicroCATS in space
While some people are planning summer vacations to theme parks with wild amusement rides, researchers at Pacific Northwest National Laboratory are planning a trip on a reduced gravity aircraft—affectionately known as the Vomit Comet.
Through a contract with the National Aeronautics and Space Administration, the Laboratory is furthering the development of micro chemical and thermal systems, or MicroCATS, for chemical processing in space applications. The contract calls for both ground testing and testing in reduced-gravity situations. For Ward TeGrotenhuis and Susie Stenkamp of the Laboratory's chemical and biological processes development group, this means that one or both of them may be experiencing weightlessness and performing mid-air laboratory tests.
"Most conventional chemical process equipment requires gravity to operate," TeGrotenhuis said. "However, the vapor-liquid separator that we're testing has extremely small channels that cause other forces, such as surface tension, to dominate."
When a two-phase fluid—fluid that contains a mixture of liquid and gas—flows through the device, it separates the liquid into one stream and the gas into another. As simple as it may sound, this process can be so problematic without gravity that it can affect which technologies are selected for space systems.
NASA is interested in new technologies for advanced systems for life support, extra-vehicular activity and even for missions to Mars. One concept involves converting carbon dioxide from the Martian atmosphere into propellant for the return trip to Earth after a robotic mission to retrieve rock samples.
The vapor-liquid separator that will be tested as soon as this summer was originally developed for the U.S. Department of Energy's Office of Transportation Technologies as part of its Fuel Cells for Transportation program. "There is very little room for a vehicle's fuel processing system, so separation technologies have to be small," TeGrotenhuis said. "It was a natural fit to adapt this technology for space applications where size and weight are driving factors."
The single-channel test unit is about the size of a pocket tape recorder. It holds a thimbleful of liquid in a channel about as wide as a toothpick. An actual unit would incorporate a stack of these channels with thin walls between them, intensifying the process and increasing the system's throughput.
TeGrotenhuis and Stenkamp will be trained and qualified for the trip on NASA's Reduced Gravity Aircraft, which can climb at a 45 degree angle from 24,000 feet to 32,000 feet and drop back to 24,000 feet about every 65 seconds. They have been told, however, that the ride is not as bad as a roller coaster because it is much smoother. After getting their feet wet, they might even look forward to a second trip to test a condenser gas-liquid separator and a microchannel distillation device that will be developed if the project for NASA continues.
This project is funded by the NASA Office of Biological and Physical Research and is managed by the Microgravity Research Division of the NASA Glenn Research Center. The results will be useful in Pacific Northwest's continued development of MicroCATS for multiple applications. See www.pnl.gov/microcats.