NASA's current flammability testing method for non-metallic solids is NASA-STD-(I)-6001A Test 1. Materials that allow for an upward flame propagation of six inches or more fail the flammability test. The flames in the Earth-based Test 1 are dominated by the upward-flowing buoyant gases, and this is not representative of actual flame behavior in microgravity, where there are no buoyant effects on flames. Scientists at NASA have shown that by spatially confining a horizontally spreading flame in the vertical direction, buoyant forces can be minimized in an Earth-based flame spread test. Results from flammability tests conducted in San Diego State University's Narrow Channel Apparatus (SDSU NCA) closely match results from NASA's Narrow Channel Apparatus at 1 atmosphere of pressure and 21% oxygen. The advantage of the SDSU NCA is that it not only minimizes buoyant effects, but it also allows flammability tests to be performed at normoxic equivalent atmospheres that more closely match future spacecraft cabin atmospheres. Normoxic conditions are achieved in the SDSU NCA by varying the total pressure, opposed flow oxidizer velocity, and oxygen concentration in the test channel. In our previous research we measured the flame spread rate across Whatman 44 ashless filter paper at total pressures from .27 to 1.0 atm and oxygen mole fractions from 0.77 to 0.21 respectively, along the normoxic curve for a gap height of 5 mm above and below the thin fuel. Significant differences in the flame spread rate were found, with much higher spread rates at the low pressure/high oxygen concentrations. This paper extends that work by comparing flame spread results from flammability tests conducted on Kimwipes* in the SDSU NCA and in true microgravity in NASA's Zero-Gravity Research Facility at several points along the normoxic curve. Also, a scaling analysis is conducted to study the effect of pressure on certain flame length scales.
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