Results of Large-Scale Spacecraft Flammability Tests

The preliminary results for two flights of the Spacecraft Fire Experiment (Saffire), conducted on an orbiting spacecraft, are presented. These experiments directly address the risks associated with our understanding of spacecraft fire behavior at practical length scales and geometries. The result of this lack of experimental data has forced spacecraft designers to base their designs and safety precautions on 1-g understanding of flame spread, fire detection, and suppression. However, low-gravity combustion research has demonstrated substantial differences in flame behavior in low-gravity. Over the past several years, NASA and an international team of investigators have worked to address open issues in spacecraft fire safety. NASA’s Spacecraft Fire Safety Demonstration Project was developed with a goal to conduct a series of large-scale experiments in true confined spacecraft environments that represent practical spacecraft fires. The first two flights are complete and examined spread over a large thin sheet of flammable fuel (cotton/fiberglass 41 x 94 cm) and over 9 samples (5 x 30 cm) of various materials (silicone (4), PMMA (2), cotton/fiberglass (2) and Nomex®) that addressed the conditions of NASA STD 6001 Test 1 (material flammability). These experiments were performed on two separate unmanned ISS re-supply spacecraft after they had delivered their cargo and had begun their return journeys to Earth (destructive reentry). Preliminary flame spread rates and flammability assessments are presented for the conditions studied with comparison to prior data. A computer modeling effort is underway to complement the experimental effort. In addition, conceptual development has begun for three more flights that will include fire detection and suppression objectives to the program.