In the microgravity environment of the International Space Station (ISS), telling the difference between an actual fire and a false alarm may not be simple. To understand how to detect smoke in space, researchers from NASA's Glenn Research Center flew the Smoke Aerosol Measurement Experiment (SAME) aboard the ISS. This experiment was originally conducted in 2007 and ran a second time in 2011.
Fire is commonly detected by measuring changes in the amount of airborne microscopic particles in smoke. Among other things, smoke can include soot, ash, polymers, solids, and even liquids. More complex products are common in the early stages of a fire, in smoldering fires, and in charring and scorching. It is the early stage of fire that is the target for a space-based fire detection system.
Smoke detectors currently in use on the ISS are based on detectors used on Earth where gravity dominates. The first experiments suggested that fires in low gravity could have more time for development of smoke particles. The particle size appears to be different enough that it impacts the best design for smoke detectors. The goal is to make a smoke detector that functions in low gravity and has a very low probability of false alarm. To achieve that, you need to know what the particle size is apart from the background nuisance sources like dust.
In the time between the runs of the investigation, NASA Glenn engineers developed the Multi-Parameter Aerosol Scattering Sensor (MPASS), which measures and characterizes particulates in real time. MPASS replaced an existing commercial device that measured one of the three moments of smoke: concentration. MPASS provided that measurement as well as the additional measurement of surface area. Researchers could eventually develop the logic that could tell the difference between smoke and dust. A future smoke detector could say, “This aerosol does not have the proper size distribution. I don’t think it is smoke.”
Researchers can use the data from SAME and MPASS to advance the understanding of fundamental science. By knowing more about the behavior of smoke and particles in low gravity, better nuisance-free early warning systems can be developed for both spacecraft and homes.