Browsing by Author "Fernandez-Pello, A. Carlos"
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Item Applying Flammability Limit Probabilities and the Normoxic Upward Limiting Pressure Concept to NASA STD-6001 Test 1(44th International Conference on Environmental Systems, 2014-07-13) Olson, Sandra L.; Beeson, Harold; Fernandez-Pello, A. CarlosRepeated Test 1 extinction tests near the upward flammability limit are expected to follow a Poisson process trend. This Poisson process trend suggests that rather than define a ULOI and MOC (which requires two limits to be determined), it might be better to define a single upward limit as being where 1/e (where e (=~2.7183) is the characteristic time of the normalized Poisson process) of the materials burn, or, rounding, where approximately 1/3 of the samples fail the test (and burn). Recognizing that spacecraft atmospheres will not bound the entire oxygen-pressure parameter space, but actually lie along the normoxic atmosphere control band, we can focus the materials flammability testing along this normoxic band. A Normoxic Upward Limiting Pressure (NULP) is defined that determines the minimum safe total pressure for a material within the constant partial pressure control band. Then, increasing this pressure limit by a factor of safety, we can define the material as being safe to use at the NULP + SF (where SF is on the order of 10 kPa, based on existing flammability data). It is recommended that the thickest material to be tested with the current Test 1 igniter should be 3 mm thick (1/8”) to avoid the problem of differentiating between an ignition limit and a true flammability limit.Item Results of Large-Scale Spacecraft Flammability Tests(47th International Conference on Environmental Systems, 2017-07-16) Ferkul, Paul; Olson, Sandra; Urban, David; Ruff, Gary; Easton, John; T'Ien, James; Liao, Ya-Ting; Fernandez-Pello, A. Carlos; Torero, Jose; Eigenbrod, Christian; Legros, Guillaume; Smirnov, Nickolay; Fujita, Osamu; Rouvreau, Sebastien; Toth, Balazs; Jomaas, GrundeThe 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.Item Spacecraft Fire Experiment (Saffire) Development Status(44th International Conference on Environmental Systems, 2014-07-13) Ruff, Gary A.; Urban, David L.; Fernandez-Pello, A. Carlos; T'ien, James S.; Torero, Jose L.; Legros, Guillaume; Eigenbrod, Christian; Smirnov, Nickolay; Fujita, Osamu; Cowlard, Adam J.; Rouvreau, Sebastien; Minster, Olivier; Toth, Balazs; Jomaas, GrundeThe status is presented of a spacecraft fire safety research project that is under development to reduce the uncertainty and risk in the design of spacecraft fire safety systems for exploration missions. The Spacecraft Fire Safety Demonstration Project is developing three Spacecraft Fire Experiments (Saffire-I, -II, and -III) to conduct a series of material flammability tests at a length scale that is realistic for a serious spacecraft fire in low-gravity. The objectives of these experiments are to (1) determine how rapidly a large scale fire grows in low-gravity and (2) investigate the low-g flammability limits compared to those obtained in NASA’s normal gravity material flammability screening test. The experiments will be conducted in Orbital Science Corporation’s Cygnus vehicle after it has deberthed from the International Space Station. Although the experiment will need to meet rigorous safety requirements to ensure the carrier vehicle does not sustain damage, the absence of a crew removes the need for strict containment of combustion products. The tests will be fully automated with the data downlinked at the conclusion of the test before the Cygnus vehicle reenters the atmosphere. A computer modeling effort will complement the experimental effort. An international topical team is collaborating with the NASA team in the definition of experiment requirements and performing supporting analysis, experimentation and technology development. The status of the overall experiment are summarized in this paper along with a brief look at future experiments that could further enhance NASA’s approach to spacecraft fire safety.