Browsing by Author "Ruff, Gary"
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Item Analysis of Saffire II two-sided concurrent flame spread over a thick PMMA slab(48th International Conference on Environmental Systems, 2018-07-08) Olson, Sandra; Urban, David; Ruff, Gary; Ferkul, Paul; Toth, Balazs; Eigenbrod, Christian; Meyer, FlorianThis paper reports the results of the microgravity flame spread over a 10 mm flat slab sample and a 4-10 mm structured sample. The samples were 50 mm wide and 290 mm long. They were ignited for 30 seconds in a constant air flow rate of 200 mm/s at one atmosphere pressure. The flame over the structured sample grew faster and was much more luminous than the flat sample. Interestingly, it was also quite non-symmetric on the two sides of the fuel card based on the radiometer readings. This non-symmetry affected the flow in the duct, implying the flame significantly affected the local flow field even in microgravity. The total radiometric output increased for the entire test time, indicating that the overall flame strength was increasing. Both flames over the samples grew to be 80-100 mm long, with soot streaming out the tip of the flames. Compared to normal gravity tests, the microgravity pyrolysis front spread rates were 18 to 24 times slower, but the fuel burnout rates were only 1.6 to 3 times slower. This resulted in a significant difference in overall flame size, with the microgravity flames being much smaller. Vapor jetting of bubbles of MMA monomer rupturing at the surface caused violent perturbations in the flame that got progressively worse as the test progressed. Both tests set off the vehicle smoke detector at levels well above the background reading of the sensor. The highest smoke detector reading occurred after the flow was turned on at the start of the flat sample test, as the residual smoke in the flow duct was flushed out. This may be due to soot agglomeration and/or the generation of a cloud of condensed fuel vapor.Item Battery Fire Risk Assessment(50th International Conference on Environmental Systems, 7/12/2021) Padilla, Rosa; Dietrich, Daniel; Pitz, William; Ruff, Gary; Urban, DavidLithium ion batteries (LIB) are crucial for future power systems and are being adapted across a span of applications in the ISS, planetary and earth science missions. Their prevalence requires the evaluation of their severe hazards in light of the unique spacecraft environment (reduced gravity, low pressure, high oxygen, limited egress opportunities, etc.). A LIB under an abuse condition can rupture and eject electrolyte vapor that can result in a flammable mixture of toxic gases that can subsequently ignite and burn. These hazards can pose an immediate risk to both the health of the crew, life support equipment and hardware. To evaluate the risks of a LIB fire in a spacecraft, this work will focus on quantifying the failure characteristics in LIB, such as, peak heat release, total energy release and combustion products. Heat release rates provides an estimate of fire growth and overall assessment of the risks to the crew and the vehicle. The peak heat release and total energy release from a single pouch cell and tablet fires are approximated using the t2 growth model and oxygen consumption calorimetry. Preliminary measurements show peak heat release rates between 2-15 kW and total energy levels between 218-290 kJ. This work has focused in quantifying the most energetic component of a LIB the electrolyte solvent, dimethyl carbonate mechanism (DMC). Flame temperatures reach above 1700 ? and major and minor gases were predicted, showing, a high level of CO2 and CO, in addition, other gases such as, acetylene (C2H2), ethylene (C2H4) and ethane (C2H6), will all be prevalent in a fire. Measurements of heat release rates and the gaseous species calculated will be used to estimate the impact that a fire has to the health of the crew member and the vehicle by calculating pressure rise and environmental temperatures.Item Characterization of Laptop Fires in Spacecraft(49th International Conference on Environmental Systems, 2019-07-07) Padilla, Rosa; Dietrich, Daniel; Lynch, Kelly; Juarez, Alfredo; Harper, Susana; Nagel, Christopher; Ruff, Gary; Urban, DavidAn accidental fire involving the Lithium-Ion (Li-ion) battery in a laptop computer is one of the most likely fire scenarios on-board a spacecraft. These fires can occur from a defect in the battery that worsens with time, over-charging the battery and leading to failure or accidental damage caused by thermal runaway. While this is a relatively likely fire scenario, very little is known about the how a laptop computer fire would impact a sealed spacecraft. The heat release would likely cause a pressure rise, possibly exceeding the pressure limit of the vehicle and causing a relief valve to open. The combustion products from the fire could pose a short-term and long-term health hazard to the crew and the fire itself could cause injury to the crew and damage to the spacecraft. Despite the hazard posed by a laptop fire, there is little quantitative data on the fire size, heat release and toxic product formation. This paper presents the results of initial attempts to quantify the fire resulting from a failed laptop battery tested at the NASA White Sands Test Facility (WSTF). The fire size and characteristics such as maximum heat release rate, total heat release, maximum temperatures and fire duration are determined. Using existing models and correlations for fires, the measured fire characteristics are extrapolated to laptop fires on a vehicle the approximate size of the Orion spacecraft.Item A Comparison of CFD and Lumped Capacity Analyses of Fires in Spacecraft(49th International Conference on Environmental Systems, 2019-07-07) Brooker, John; Dietrich, Dan; Gokoglu, Suleyman; Ruff, Gary; Urban, DavidComputational fluid dynamics (CFD) simulations of flows inside a spacecraft offer a high level of detail and fidelity and are invaluable tools in the design of spacecraft environmental control and life support systems (ECLSS). They are, however, time and resource intensive and not efficient for large scale sensitivity analyses over a range of possible design parameters. Lumped capacity analysis (LCA) treatments are simple and fast, but lack the detailed treatment of flow and heat transfer that CFD simulations offer. Their speed and low level of required resources, however, make them more convenient for large sensitivity analyses. Both approaches have the potential to be design tools to assess the impact that an accidental fire will have on a spacecraft. This paper compares the results of CFD and LCA simulations for a given volume approximately the size of the Orion spacecraft. The CFD model uses the open source Fire Dynamics Simulator for the simulation and includes, as sensitivity parameters, changes in ECLSS ventilation (direction and speed), fire location, and wall boundary condition. The results show that the LCA model can reasonably predict pressure rise in a spacecraft if the prescribed fire scenario approximates the model assumptions. The sensitivity studies show how variations in parameters not captured directly in the LCA model (e.g., direction of ventilation flow) influence the results and provide limits on the predictive capability of the LCA. We also demonstrate how CFD simulations can improve LCA predictions by providing more realistic estimates of heat transfer coefficients between the gas and various cabin walls.Item Concurrent Upward Flame Spread over a Fire Resistant Fabric (Nomex) under External Heating(47th International Conference on Environmental Systems, 2017-07-16) Thomsen, Maria; Huang, Xinyan; Alonso, Alain; Fernandez-Pello, Carlos; Urban, David; Ruff, GaryFire resistant materials are used in multiple applications (clothing, curtains, tents, etc.) were protection from a potential fire is needed. Particularly relevant for this work is the application for astronaut space suits since a spacecraft environment may be different than atmospheric ones. Furthermore, their fire resistant capacity are often tested under very specific conditions that might not represent the real fire situations. For example, when a material is exposed to a near fire or different environmental conditions like reduced pressure, enriched oxygen concentration and micro-gravity, its flammability and fire behaviors can be altered. In this work, an experimental study was performed to investigate the effect of ambient pressure and oxygen concentration on the upward flame spread over a typical fire resistant fabric (Nomex HT90-40) exposed to two different external heat sources. One is the radiation from infrared lamps and the other is the flame from a burning polymethyl methacrylate (PMMA) sheet placed below the fabric. The limiting oxygen concentration (LOC) was first quantified under different external heating, and then the upward flame-spread rate above LOC was measured. Experiments show that the flame from nearby burning object not only can ignite the fire resistant fabric, but also extend the LOC of the material to lower oxygen concentrations. Moreover, the heating from the attached flame is different from an external radiant flux. The results of this work also provide important information about the fire interactions of different materials, and guide the future fire safety design in space exploration.Item The Effect of Buoyancy on Upward-Concurrent Flame Spread over Thin Paper(49th International Conference on Environmental Systems, 2019-07-07) Thomsen, Maria; Fernandez-Pello, Carlos; Urban, David; Ruff, GaryUnderstanding material flammability inside a spacecraft is important because the conditions in spacecraft environments can greatly differ from those on earth. Because in a gravity field there is a flame-induced buoyancy, it is very difficult to reproduce on Earth the environmental conditions of a spacecraft, thus making fire testing harder. To overcome this problem, alternative approaches that reduce buoyancy are required. One possibility to reduce buoyancy effects relies in using reduced ambient pressure. The objective of this work is to study the effect of pressure, and consequently buoyancy, on upward/concurrent flame spread over a thin combustible solid, and by comparison with partial gravity data, observe up to what point low-pressure can be used to replicate flame characteristics observed in different gravity levels. Experiments in normal gravity were conducted over pressures ranging between 100 and 30 kPa and a forced flow velocity of 10 cm/s. Results show that reductions of pressure slow down the flame spread over the material surface. As pressure is reduced, flame intensity is also reduced. Comparison with partial gravity data shows that as the pressure is reduced, the normal gravity flame spread rate approaches that observed at different gravity levels. The data presented is correlated in terms of a mixed convection non-dimensional number that describes the convective heat transferred from the flame to the solid, and that also describes the primary mechanism controlling the spread of the flame. The correlation provides information about the similitudes of the flame spread process in variable pressure, flow velocity and gravity environments, providing guidance for potential ground-based testing for fire safety design in spacecraft.Item The effect of reduced pressure on the characteristics of spreading flames(50th International Conference on Environmental Systems, 7/12/2021) Carmignani, Luca; Thomsen, Maria; Fereres, Sonia; Gollner, Michael; Fernandez-Pello, Carlos; Urban, David; Ruff, GaryFlame spread over solid fuels is a canonical problem in fire science, due to its direct implications on material flammability and importance in fire development. In a microgravity environment, such as onboard a spacecraft, flames can behave very differently than on Earth. This is concerning for spaceflight life safety, especially in higher-oxygen environments. Due to the difficulties associated with microgravity testing, low-pressure environments have been proposed as an alternative to approximately replicate reduced gravity conditions because of the reduction in buoyancy. However, the roles played by gravity and pressure on flame length, standoff distance, and flame spread rate vary with the burning configuration. In concurrent flame spread, the buoyant flow enhances the spread rate by bringing the flame closer to the fuel surface and increasing the heating of the solid fuel. In opposed flame spread, the sample is preheated by the flame ahead of the flame leading edge, which is strongly affected by the surrounding flow field. In this work, we consider flames spreading over thin cotton samples in both downward (opposed) and upward (concurrent) configurations to investigate the effect of pressure (30-100 kPa) on flame characteristics, such as spread rate and standoff distance. A small forced flow is induced upward so that the flames are exposed to a mixed (forced and free) flow. By reducing pressure, flames become less bright, their standoff distance increases, and their spread rates decrease in analogy with low-gravity flames. These results could in help understanding the differences between flames at low pressure and low gravity environments for these similar, yet very different, spreading configurations. They could also provide further information about potential Earth testing of the flammability of materials in spacecraft environments.Item Evaluation of Combustion Products from Large-Scale Spacecraft Fires during the Saffire-IV and Saffire-V Experiments(50th International Conference on Environmental Systems, 7/12/2021) Fortenberry, Claire; Casteel, Michael; Graf, John; Easton, John; Niehaus, Justin; Meyer, Marit; Urban, David; Ruff, GaryThe aim of the spacecraft fire safety series of experiments (Saffire) is to investigate the behavior of large-scale fires in microgravity. During these experiments, materials are ignited within the Northrop Grumman Cygnus resupply vehicle following its departure from the International Space Station. Saffire-IV and Saffire-V introduced a far-field diagnostics (FFD) unit to house sensors for smoke characterization, including gas monitors and particle detectors. The FFD also housed a prototype �smoke eater� device and a CO2 scrubber, which are designed to remove combustion products from a spacecraft atmosphere. Remote sensors installed at six locations throughout the Cygnus cabin measured CO2 concentrations and temperature, allowing evaluation of smoke plume transport. In this work, we report on gas and particle measurements from the Saffire-IV and Saffire-V experiments, presenting the first effort to comprehensively characterize combustion products from large-scale microgravity fires. We evaluate the transport of key species throughout the spacecraft cabin. Finally, we address post-fire cleanup methods and discuss remaining science questions to be targeted in future work.Item Fire Detection tradeoffs as a function of Vehicle Parameters(46th International Conference on Environmental Systems, 2016-07-10) Urban, David; Dietrich, Daniel; Brooker, John; Meyer, Marit; Ruff, GaryFire survivability depends on the detection of and response to a fire and before it has produced a lethal environment in the vehicle. This is an interplay between the fire burning and growth rate; the vehicle size; the detection system design; the transport time to the detector (controlled by the level of mixing in the vehicle); and the rate at which the life support system filters the atmosphere, potentially removing the detected property. Given the large differences in critical vehicle parameters (volume, mixing rate and filtration rate) the detection approach that works for a large vehicle (the ISS) may not be the best choice for a smaller crew capsule. This paper examines the impact of vehicle size and environmental control and life support system parameters on the detectability of fires in comparison to the hazard they present. A lumped capacity model was developed that considers smoke, heat, and toxic product release rates in comparison to mixing and filtration rates in the vehicle. Recent work has examined the production rate of smoke and several hazardous species from overheated spacecraft polymers. These results are used as the input data set in the lumped capacity model in combination with the transport behavior of major toxic products released by overheating spacecraft materials to evaluate the necessary alarm thresholds to enable appropriate response to the fire hazard.Item Fire Safety Implications of Preliminary Results from Saffire IV and V Experiments on Large Scale Spacecraft Fires(50th International Conference on Environmental Systems, 7/12/2021) Urban, David; Ruff, Gary; Ferkul, Paul; Easton, John; Owens, Jay; Olson, Sandra; Meyer, Marit; Fortenberry, Claire; Brooker, John; Graf, John; Casteel, Michael; Jomaas, Grunde; Toth, Balazs; Eigenbrod, Christian; T'Ien, James; Liao, Ya-Ting; Fernandez-Pello, Carlos; Meyer, Florian; Legros, Guillaume; Guibaud, Augustin; Smirnov, Nikolay; Fujita, OsamuThe spread and growth of flames over large solid fuel samples and their effect on the pressurized spacecraft were studied inside Cygnus spacecraft while in orbit after departing the International Space Station. These experiments were developed by NASA�s Advanced Exploration Systems Division in the Human Exploration and Operations Mission Directorate. The ignited materials consisted of poly-methyl methacrylate (PMMA), cotton fabric and a cotton/fiberglass fabric blend. The samples were all 40 cm wide and with various lengths ranging from 18 cm for the PMMA samples to 50 cm for the fabrics. The overall results from these tests and their impact on the spacecraft are presented with emphasis on the fire safety implications of the results. The experiments included, a post-fire cleanup system, vehicle internal volume measurements, and transport of acid gases (HCl and HF). Measurements included video images, flame spread rate, flame temperatures and radiant heat output; energy release through oxygen calorimetry; distributed measurements of CO2 concentration and temperature at six locations in the spacecraft; CO2, CO, O2, HF and HCl concentrations; vehicle pressurized volume; and aerosol concentrations. Details of the flame growth and spread are discussed in other papers as are details of the post-fire cleanup system performance. The fire events had a measurable impact on the vehicle pressure, temperature, and carbon dioxide concentration. However, despite having heat release rates up to 10 kW, the average vehicle conditions did not rise to unacceptable levels. The combined results of the experiments provide significant new understanding of the impact of sample and flow duct height on flame spread and growth in addition to an improved perspective of the impact of a fire event on a spacecraft.Item Hazardous Effects of Li-Ion Battery Based Fires(2020 International Conference on Environmental Systems, 2020-07-31) Padilla, Rosa; Alcantara, Ilse; Meyer, Marit; Juarez, Alfredo; Dietrich, Daniel; Urban, David; Ruff, Gary; Nagel, Christopher R.A potential thermal runaway (TR) failure from a computer with a lithium ion (Li-ion) battery is one of many energetic fuel sources present on-board a spacecraft vehicle that poses a fire safety concern. Tests were performed inside an 8 m$^{3}$ test chamber at White Sands Test Facility (WSTF) to emulate a spacecraft, addressing major aspects related to fire safety prevention, detection, suppression and post fire cleanup. A tablet was forced into TR by using a 60 W patch heater on a single pouch cell and comparisons with a higher energy unit laptop are presented as the worst-case representation of a fire. Initial venting of electrolyte is first observed on a failed pouch cell followed by an open fire. Pouch cell surface temperatures reach a maximum thermal runaway between 340-544 $^{\circ}$C across all units tested and during this event a large presence of toxic gases are released. Tablet fires with a maximum of two pouch cells that underwent TR reached a maximum of 14 kW aggressively and over 0.4 m in height. A large presence of carbon monoxide, CO and carbon dioxide, CO$_{2}$ was measured for higher energy fires and, prior to fire suppression. Levels of acrolein, C$_{3}$H$_{4}$O and CO are present above the maximum allowable concentrations levels inside a spacecraft vehicle. Additional gases, such as, measured benzene, C$_{6}$H$_{6}$, propylene, C$_{3}$H$_{6}$ and acrylonitrile are also present. This work provides insight in to the detection capability and required response times for triggering fire alarms aboard a vehicle. In addition, the data can be used to assess the capacity at which the life support systems capability to provide a hazard free environment.Item Modeling Characterization of Smoke Particle Transport and Fate in Lunar Gravity(2023 International Conference on Environmental Systems, 2023-07-16) Fortenberry, Claire; Urban, David; Ruff, GarySpacecraft fires present one of the most dangerous scenarios threatening crew safety for future lunar and deep space missions. Spacecraft fire detection strategies are challenged by transport phenomena unique to reduced gravity environments. To date, spacecraft fire detection studies have focused on microgravity systems, but, as NASA plans to return to the Moon, more research is needed to evaluate optimal fire detector placement in lunar gravity. This placement must consider a balance between the buoyant flow towards the ceiling due to lunar gravity and the cabin air filtration. Here, we present results from a study to evaluate smoke particle transport from an early-stage fire in lunar gravity. This model, built in COMSOL Multiphysics, combines turbulent flow, heat transfer, and particle transport from a simulated material overheating (pre-flame) event under varied temperature conditions. Particle velocities are tracked in lunar gravity and compared to results from terrestrial gravity calculations to evaluate timescales for buoyant transport. Results suggest that in lunar gravity, small (~1 µm) particles travel upward at velocities similar in magnitude to average air velocities on the ISS. However, maximum smoke plume velocities are dependent on fuel configuration and location, and smoke particle transport must be evaluated considering particle properties like size, density, and morphology. Finally, we consider a hypothetical ventilation strategy with a low-velocity forced flow applied from ceiling air supplies to floor air returns. Under the tested conditions, the upward flow of a buoyant lunar smoke plume may enable strategic placement of smoke detectors on ceilings of future lunar spacecraft cabins depending on the cabin ventilation velocity, air filtration, and habitat design.Item Modeling the Effect of Buoyancy and External Heating on the Flame Spread in Fire Resistant Fabrics(48th International Conference on Environmental Systems, 2018-07-08) Thomsen, Maria; Fereres, Sonia; Alonso Ipiña, Alain; Fernandez-Pello, Carlos; Urban, David; Ruff, GarySpacesuits are fabricated with Nomex, Kevlar and other fire resistant fabrics. The flammability behavior of these materials has been widely studied experimentally, mostly under standard sea level atmospheric conditions. However, future human space exploration vehicles and habitat environments will very likely have different environments, i.e. reduced pressure and enriched oxygen concentration. Experiments under these conditions, particularly in microgravity, can become a difficult and expensive task. Numerical investigations of the flammability of high performing fibers/fabrics may be a viable alternative to experiments. Here we present a numerical model formulated to understand the effect of environmental conditions on the flame propagation characteristics of thin fire-resistant material such as Nomex. Moreover, the effect of external radiant heating on material flammability is also studied. Thermogravimetric analysis (TGA) experiments were performed with Nomex to estimate the kinetic parameters, which were then used to model the thermal decomposition of the fabric sample using a Computational Fluid Dynamics (CFD) code, Fire Dynamics Simulator (FDS6). Two-dimensional simulations are performed using finite-rate single-step combustion kinetics in the gas phase and an Arrhenius reaction mechanism with multiple steps for the solid phase decomposition. The model results are then compared to previous experimental results at high oxygen concentrations and/or reduced pressure conditions. It is shown that with the appropriate kinetic parameters the model is able to capture the main physical aspects of the flame spread of a thin solid fuel and it provides a basis for future modeling of fire resistant fabrics for space exploration.Item NASA Environmental Control and Life Support Technology Development for Exploration: 2020 to 2021 Overview(50th International Conference on Environmental Systems, 7/12/2021) Broyan, James; Gatens, Robyn; Schneider, Walter; Shaw, Laura; McKinley, Melissa; Ewert, Michael; Meyer, Marit; Ruff, Gary; Owens, Andrew; Meyer, CatlinThis paper provides an overview of NASA supported activities developing Environmental Control and Life Support (ECLSS) technologies in the following capability areas: life support, environmental monitoring, fire safety, and logistics. NASA has been refining technology needs for deep space missions including Gateway, lunar surface, Mars transit, and Mars surface missions. Validating technologies in relevant environments, both in low earth orbit (LEO) and ground tests is critical in understanding technology performance and long duration performance. On-orbit and ground tests inform NASA�s technology decisions to fill exploration gaps. NASA has multiple technology projects across the technology readiness spectrum with potential to fill or partially fill exploration gaps. For each capability area, this paper will describe select capability gaps, NASA technology project maturation over the past year, and how key performance parameters (KPPs) are being used to measure the degree of capability gap closure. KPPs are evolving but they still provide a useful measure in communicating progress and identifying development needs to fill exploration gaps. The intent is to provide a very high-level overview describing the strategic approach to gap closure and provide references to additional technical details, progress, and KPPs.Item NASA Environmental Control and Life Support Technology Development for Exploration: 2021 to 2022 Overview(51st International Conference on Environmental Systems, 7/10/2022) Broyan, James; McKinley, Melissa; Stambaugh, Imelda; Ruff, Gary; Owens, AndrewOver the past year, significant progress has occurred in technology development, ground testing, and ISS technology demonstrations within the NASA Environmental Control and Life Support (ECLSS) community. This paper provides a technology development update in the following capability areas: life support, environmental monitoring, fire safety, and logistics. Technologies for exploration missions must be reliable in their operation which support crewed mission phases. However, they also need to be put into reduced use or dormant states to support uncrewed mission phases and then successfully and reliably returned to a nominal state to support crew. Multi-year demonstration of systems operation across this range of conditions are essential to mission success. Project overviews will include how the current activity supports the goal of multi-year demonstrations, planned follow-on activities, and what type of exploration mission elements are targeted for infusion. Technologies must be demonstrated and validated early enough to inform early exploration element milestone reviews (mission concept reviews, systems requirement reviews and no later than preliminary design reviews) so that supporting vehicle systems can also be matured.Item Operation and Development Status of the Spacecraft Fire Experiments (Saffire)(46th International Conference on Environmental Systems, 2016-07-10) Ruff, Gary; Urban, DavidSince 2012, a series of Spacecraft Fire Experiment (Saffire) have been under development by the Spacecraft Fire Safety Demonstration (SFS Demo) project, funded by NASA’s Advanced Exploration Systems. The overall objective of this project is to reduce the uncertainty and risk associated with the design of spacecraft fire safety systems for NASA’s exploration missions. This is accomplished by defining, developing, and conducting experiments that address gaps in spacecraft fire safety knowledge and capabilities identified by NASA’s Fire Safety System Maturation Team. The Spacecraft Fire Experiments (Saffire-I, -II, and -III) are material flammability tests at length scales that are realistic for a spacecraft fire in low-gravity. The specific 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 ATK’s Cygnus vehicle after it has unberthed from the International Space Station. The tests will be fully automated with the data downlinked at the conclusion of the test before the Cygnus vehicle reenters the atmosphere. This paper will discuss three topics from the SFS Demo project. First, a status of the Saffire-I, II, and III experiments will be presented including an update on the initial results from the Saffire-I mission. Second, the objectives and development status for the next series of experiments, Saffire-IV, V, and VI, will be discussed including how these results will address spacecraft fire safety knowledge and capability gaps for NASA’s exploration missions. Finally, several ground-based activities that support these experiments and address other fire safety gaps for exploration will also be addressed.Item Opposed-flow spreading flames: Effect of sub-atmospheric pressure on spread and burning rates(51st International Conference on Environmental Systems, 7/10/2022) Carmignani, Luca; Garg, Priya; Thomsen, Maria; Gollner, Michael; Fernandez-Pello, Carlos; Urban, David; Ruff, GaryFlame spread over solid fuels is a canonical problem in fire science, due to its direct implications on material flammability and importance in fire development. Flames in a microgravity environment can behave very differently than on Earth, posing additional risks for spaceflight life safety. Due to the difficulties associated with microgravity testing, sub-atmospheric pressures in ground-based experiments have been proposed to approximately replicate the burning behavior of solid fuels in reduced gravity conditions because of similar effects on heat and mass transfer mechanisms from the flame to the solid. However, the roles played by gravity and pressure vary with the flame spread configuration. In opposed flame spread, the solid fuel is heated by the flame ahead of its leading edge, and this process is strongly affected by the ambient conditions. In this work, we consider flames spreading over acrylic samples exposed to a forced flow of 20 cm/s, and pressures between 30 and 100 kPa. Flame characteristics such as spread rate, standoff distance, and length are obtained from the video analysis of the experiments and compared at different pressures. Mass burning rates are calculated from the samples weight measured before and after the experiments. Additionally, gas emissions measured during the experiments are used to estimate the heat release rate of the spreading flames. Results show a decreasing non-monotonic behavior of flame length, spread rate, and mass burning rate with reducing pressure. The comparison of the heat release rate obtained from the measured emissions and the estimated mass burning rate, suggests that chemical kinetics is not driving the decrease in flame spread rate observed at low pressures. These results could provide more information to guide future Earth-based flammability testing of materials for spacecraft applications. This research was supported by NASA Grant NNX12AN67A.Item Optimization of Fire Detection Limits for Manned Spacecraft(47th International Conference on Environmental Systems, 2017-07-16) Dietrich, Daniel; Meyer, Marit; Brooker, John; Urban, David; Ruff, GaryThe ability to safely and reliably detect an incipient fire is critical to the safety of both the crew and spacecraft for manned spaceflight missions. At the same time, however, false alarms to non-fire conditions can, at best, waste valuable crew time and, at worst, create a situation where the crew fails to respond adequately to a real fire because of too many false alarms. In a recent paper, we considered the fire size (based on experimental particulate generation rates) that would trigger a particle sensing fire detector based on realistic vehicle parameters such as ventilation flow, filtration and detector set point. The results showed the importance of filtration and ventilation flow for early detection of any incipient fire. This paper continues that work to consider background sources of indoor aerosols in addition to smoke particles. The lumped capacity model considers fire-generated particulate, smoke and toxic gases. It simplifies the flow inside the vehicle but contains the most relevant physics in a computational model that is amenable to large-scale parametric studies. In this paper, background aerosol sources such as that from clothing, Velcro and other human-generated particles are considered in addition to fire. For test cases we consider three vehicles relevant to space exploration, a node inside the International Space Station (ISS), an exploration vehicle with the specifications of the Crew Exploration Vehicle (CEV) and, for legacy purposes, the Space Shuttle. In addition to the different vehicles, we consider variations in ventilation flow and filtration and examine the likelihood of a false trigger as compared to the ability to successfully identify a fire before it reaches a size where it poses a significant threat to the crew or vehicle.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 Safety Technology Development Plan For Exploration Missions(2020 International Conference on Environmental Systems, 2020-07-31) Urban, David; Ruff, Gary; Dietrich, DanielTo date, NASA’s spaceflight operations in the past 5 decades have been limited to a narrow range of conditions from a fire safety perspective. The currently anticipated missions outside of low earth orbit will substantially expand this parameter space to include, extended durations, dormancy intervals, increased oxygen concentrations, partial gravity conditions and the presence of surface dust. All of these changes can have significant impacts on fire safety system design and operations. The overall state of understanding is discussed in this paper along with the identification of the needs for spacecraft fire safety technology development. These needs have been assembled into a roadmap maintained by the Environmental Control and Life Support System Capability Leadership Team that has evolved as the exploration mission concepts have changed. This roadmap continues to communicate the spacecraft fire safety needs for exploration and guide technology development efforts. This paper summarizes the major recent developments in our understanding of spacecraft fire behavior and mitigation. A review of the major technology development needs and discussion of their objectives, status, and future plans is presented. The plan for transitioning knowledge, hardware, and modeling capability resulting from these development efforts to specific exploration vehicle programs and missions is also discussed.