Volume 30, Issue 2 (March 2002)
Test Method to Determine Flammability of Aerospace Materials
Qualitative correlations between ground upward flammability tests and flammability testing in microgravity indicate that the NASA STD 6001 Test 1 provides conservative results by sustaining flaming combustion in less severe environments than those in which extinguishment occurs in quiescent microgravity environments. The upward flammability test is conducted in the most severe flaming combustion environment expected in the spacecraft. Its pass/fail test logic does not allow a precise quantitative comparison with other ground or microgravity materials flammability test results. Thus, although reasonable from a flammability safety point of view, the test is likely to eliminate materials that may be safe for use on spacecraft. A different test logic that will determine materials self-extinguishment limits is suggested to address these impediments. Data to support this approach are presented, including self-extinguishment limits in concurrent and countercurrent flows and under quiescent conditions. The proposed method will allow continued use of existing NASA flammability data and make possible quantitative correlations between ground testing and microgravity test results. Quantitative correlations between ground test results and microgravity combustion data will improve the aerospace materials selection process and allow realistic estimates of spacecraft fire extinguishment requirements. Theoretical analyses of flaming combustion will be possible, leading to a better understanding of materials combustion. This will benefit not only the aerospace community, but also the combustion community at large.