Over the past decade, NASA has sponsored a growing amount of microgravity combustion research that has afforded considerable insight into a wide variety of fundamental problems. The vast majority of earlier funded projects claimed strong 'relevance' to fire safety aboard spacecraft, but unfortunately the actual connections are often weak (their clear value is in the fundamental knowledge that is gained). In contrast, the experiments we plan are aimed directly at testing, understanding and unproving NASA 's existing policies and practices toward spacecraft fire safety. In this study, we examine several previously unaddressed issues regarding these fire safety practices and policies. Specifically,
a. NASA Test 1(an upward flame spread test) is the primary qualification test for materials' use on spacecraft. NASA Test 1, however, does not consider some possible fire sources and some of its assumptions remain unvalidated. These include, among others: a. Premixed fires can occur and heat and ignite solid materials, but these are unconsidered in Test 1; b. Solid materials may be heated well above normal spacecraft air temperatures at the time of an accidental exposure to an ignition source (again unconsidered); c. The effect of firebrands in 1g is assumed to be worst case.
b. Configuration control in microgravity is unvalidated. NASA requires that flammable materials be separated by 5 cm or more, so that fire from one material cannot ignite a neighboring material.
c. There are also concerns with the fire suppression practices and policies. For example, there is uncertainty about the time to extinguish a fire upon termination of ventilation. The application of a jet of suppressant may itself produce firebrands from molten or charring material, and cause an accidental spread of fire. Finally, carbon dioxide, the suppressant of choice for the International Space Station, behaves differently than other diluent, in regard to its impact on the range of oxygen concentrations that will support a flame [1]. The goal of the proposed research is to contribute to improved fire safety practices and policies for spacecraft and Martian habitat through the achievement of the following objectives: 1. Determine systematically the conditions that will ignite onboard flammable materials upon passage of an initial premixed gas, firebrand, or aerosol flame over these materials. 2. Test the effect of firebrands and configuration spacing. 3. Determine the effectiveness Of the flow Of C02 extinguisher or other extinguishing agents.
Ross, H.D., Mell, W., Pettegrew, R., Hicks, M., Urban, D., Fire Accident Testing Evaluation (FATE), Sixth International Microgravity Combustion Workshop, NASA Glenn Research Center, Cleveland, OH, CP-2001-210826, pp. 413-416, May 22-24, 2001.