A combustion experiment jointly designed by scientists and engineers at NASA’s Glenn Research Center (Cleveland, OH) and the Universities Space Research Association (USRA) is currently in operation onboard the International Space Station (ISS). The Burning and Suppression of Solids (BASS) experiment will bridge the gap among normal-gravity material flammability screening tests, short-time ground-based microgravity tests, and actual zero-gravity spacecraft conditions. The basic applied hypothesis is that in certain conditions, a material in zero-gravity will be more flammable than it is in normal gravity.

In space, the lack of gravity provides the opportunity to study a larger range of flame characteristics than could be studied on Earth. The absence of gravity’s effects on convection aboard the ISS or other space vehicle makes flames behave in a different manner. Similarly, suppressing fires in microgravity is different than on Earth, since in microgravity it may not be clear where the base point of a flame is, and the stabilization zone may not be apparent. While microgravity conditions can be achieved on Earth using drop towers, these facilities only provide microgravity for a few seconds. Of particular interest to scientists is the long-duration burn of combustible materials that can only be achieved in space.

The BASS experiment will burn 41 fuel samples (the majority of the samples will be ignited and burned multiple times). BASS will also assess the effectiveness of an inert, gaseous extinguishing agent (similar to that used on ISS) in putting out flames over different materials, in different geometries, and at different flows. Astronaut Don Pettit is conducting the BASS experiment within the Microgravity Science Glovebox. The glovebox, designed as an enclosed work area, is sealed to contain fluids, gases, and equipment. The Operations Team will work with Pettit to position and ignite the fuel samples, control the relative flow speeds, allow time for burning, and extinguish the flames. Images and video will be captured and downloaded.

To date, five BASS samples have been successfully burned and extinguished, one of which was re-burned three more times to vary airflow and suppression technique. After two minutes of burning, the flow was turned off and the flame was extinguished rapidly, supporting the protocol that the best initial response to a fire in microgravity is to turn off any forced airflow. In another test, after about a minute of burning, nitrogen was turned on, and the flame responded but did not go out. In fact, the flame appeared to get brighter. This new observation in which the nitrogen jet was able to entrain air all by itself will be studied further, and has important implications for gaseous fire suppression systems like the one currently employed on the ISS.

Burning and Suppression of Solids (BASS) experiment
Universities Space Research Association (USRA)
Columbia, MD

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