Solid Fuel Ignition Testing for Lunar Applications, Theory and Experimental Results

To address the risk of enhanced flammability in lunar gravity, NASA has initiated a program to develop a new test method that provides an estimate of the flammability enhancement expected in lunar gravity. An overview of the physical phenomena that control NASA material flammability testing is presented with discussion of how this testing is being adapted to evaluate material flammability in lunar gravity. Testing in drop towers and on reduced gravity aircraft has shown that there can be enhanced flammability (flames can exist at lower ambient oxygen concentrations compared to terrestrial gravity) at partial gravity levels close to those found on the moon. This was identified as a risk for the Human Landing System program. However, lunar gravity testing is largely limited to using a centrifuge in the NASA GRC 5.2 second drop tower. This paper discusses the fundamentals of material flammability and extinction, and develops a Damköhler-number based estimate of the blow-off flammability limit. This relationship is compared to the results from material flammability tests in a highspeed blow-off facility at the NASA White Sands Test Facility (WSTF) (1-g) and the Glenn Research Center (GRC) Zero Gravity Facility partial gravity centrifuge.