Gary Ruff - Academia.edu (original) (raw)

Papers by Gary Ruff

42nd International Conference on Environmental Systems, Jul 15, 2012

Results are presented from the Reflight of the Smoke Aerosol Measurement Experiment (SAME-2) whic... more Results are presented from the Reflight of the Smoke Aerosol Measurement Experiment (SAME-2) which was conducted during Expedition 24 (July-September 2010). The reflight experiment built upon the results of the original flight during Expedition 15 by adding diagnostic measurements and expanding the test matrix. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The smoke was initially collected in an aging chamber to simulate the transport time from the smoke source to the detector. This effective transport time was varied by holding the smoke in the aging chamber for times ranging from 11 to 1800 s. Smoke particle samples were collected on Transmission Electron Microscope (TEM) grids for post-flight analysis. The TEM grids were analyzed to observe the particle morphology and size parameters. The diagnostics included a prototype two-moment smoke detector and three different measures of moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and, by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations can also be calculated. Overall the majority of the average smoke particle sizes were found to be in the 200 nm to 400 nm range with the quiescent cases producing some cases with substantially larger particles.

International Conference on Environmental Systems, Jul 7, 2019

An accidental fire involving the Lithium-Ion (Li-ion) battery in a laptop computer is one of the ... more An 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, overcharging 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 shortterm 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.

SAE technical paper series, Jul 12, 2009

46th AIAA Aerospace Sciences Meeting and Exhibit, Jan 7, 2008

Results from a recent smoke particle size measurement experiment conducted on the International S... more Results from a recent smoke particle size measurement experiment conducted on the International Space Station (ISS) are presented along with the results from a model of the transport of smoke in the ISS. The experimental results show that, for the materials tested, a substantial portion of the smoke particles are below 500 nm in diameter. The smoke transport model demonstrated that mixing dominates the smoke transport and that consequently detection times are longer than in normal gravity.

47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, Jan 5, 2009

Smoke particle size measurements were obtained under low-gravity conditions by overheating severa... more Smoke particle size measurements were obtained under low-gravity conditions by overheating several materials typical of those found in spacecraft. The measurements included integral measurements of the smoke particles and physical sample of the particles for Transmission Electron Microscope analysis. The integral moments were combined to obtain geometric mean particle sizes and geometric standard deviations. These results are presented with the details of the instrument calibrations. The experimental results show that, for the materials tested, a substantial portion of the smoke particles are below 500 nm in diameter.

Proceedings of the Combustion Institute, 2019

The flammability of combustible materials in spacecraft environments is of importance for fire sa... more The flammability of combustible materials in spacecraft environments is of importance for fire safety applications because the environmental conditions can greatly differ from those on earth, and a fire in a spacecraft could be catastrophic. Moreover, experimental testing in spacecraft environments can be difficult and expensive, so using ground-based tests to inform microgravity tests is vital. Reducing buoyancy effects by decreasing ambient pressure is a possible approach to simulate a spacecraft environment on earth. The objective of this work is to study the effect of pressure on material flammability, and by comparison with microgravity data, determine the extent to which reducing pressure can be used to simulate reduced gravity. Specifically, this work studies the effect of pressure and microgravity on upward/concurrent flame spread rates and flame appearance of a burning thin composite fabric made of 75% cotton and 25% fiberglass (Sibal). Experiments in normal gravity were conducted using pressures ranging between 100 and 30 kPa and a forced flow velocity of 20 cm/s. Microgravity experiments were conducted during NASA's Spacecraft Fire Experiment (Saffire), on board of the Orbital Corporation Cygnus spacecraft at 100 kPa and an air flow velocity of 20 cm/s. Results show that reductions of ambient pressure slow the flame spread over the fabric. As pressure is reduced, flame intensity is also reduced. Comparison with the concurrent flame spread rates in microgravity show that similar flame spread rates are obtained at around 30 kPa. The normal gravity and microgravity data is correlated in terms of a mixed convection non-dimensional parameter that describes the heat transferred from the flame to the solid surface. The correlation provides information about the similitudes of the flame spread process in variable pressure and reduced gravity environments, providing guidance for potential on-earth testing for fire safety design in spacecraft and space habitats.

SAE Technical Paper Series, Jul 11, 2005

The history and current status of spacecraft smoke detection is discussed including a review of t... more The history and current status of spacecraft smoke detection is discussed including a review of the state of understanding of the effect of gravity on the resultant smoke particle size. The results from a spacecraft experiment (Comparative Soot Diagnostics (CSD)) which measured ...

Aerosol Science and Technology, Mar 9, 2015

Combustion and Flame, Dec 1, 2012

ABSTRACT This work presents a numerical modeling investigation of the mechanisms controlling the ... more ABSTRACT This work presents a numerical modeling investigation of the mechanisms controlling the dependence on ambient pressure of the piloted ignition of a solid fuel under external radiant heating. The focus is to confirm the hypotheses and phenomenological arguments generated by previous experimental studies of the problem. For this purpose, the effect of ambient pressure on the piloted ignition of thermally irradiated samples of PMMA is modeled using the Fire Dynamics Simulator (FDS5) code. Two-dimensional simulations were performed using finite-rate single-step combustion kinetics in the gas-phase and a single-step Arrhenius reaction rate for the solid phase decomposition. Oxidative pyrolysis is not considered and the in-depth formed pyrolyzate is assumed to flow unrestricted through the PMMA. The objective is to understand the thermo-physical mechanisms leading to ignition and how they may be affected by a reduction in ambient pressure. The model is able to reproduce the main physical aspects of the piloted ignition of a solid fuel and confirms previous phenomenological explanations developed to describe recent experimental results at a range of ambient pressures. Reduced pressure environments result in: (1) shorter ignition times mainly due to reduced convective heat losses from the heated material to the surroundings, allowing for the material to heat more rapidly and pyrolyze faster; (2) a lower fuel mass flux at ignition, due primarily to a thicker thermal boundary layer and a thicker fuel species profile. The appearance of a premixed flame at the pilot, its propagation through the combustible mixture above the solid surface, and the subsequent sustained burning conditions are also explored in this work. The calculated ignition times and mass loss rates at ignition are compared to those measured experimentally in a laboratory-scale combustion wind tunnel. It is shown that with appropriate kinetic parameters the model qualitatively agrees with the experimental data.

SAE technical paper series, Jul 12, 2009

Combustion and Flame, Apr 1, 2015

The influence of environmental conditions on solid fuel ignition is of particular interest in spa... more The influence of environmental conditions on solid fuel ignition is of particular interest in spacecraft fire safety because of the large difference in environments between a spacecraft and earth (low gravity, low gas flow velocities, low pressure, elevated oxygen concentration). Considering that fire safety is essential when dealing with spacecraft vehicles, where space is confined and egress is difficult or almost impossible, low gravity fire initiation has a prominent importance. In addition to microgravity, low cabin pressure may further decrease the convective heat losses from the solid, leading to a faster heating of the materials and therefore raising the fire hazard on board. A numerical model developed with the CFD code Fire Dynamics Simulator (FDS) was used to analyze the effect of reduced gravity and ambient pressure on the transport processes taking place in the piloted ignition of an externally irradiated solid fuel. The model simultaneously solves the gas phase and solid phase conservation equations, using a one-step second order Arrhenius reaction rate for the gas phase kinetics and a one-step global Arrhenius reaction rate for the solid phase decomposition. The transition from an incipient premixed reaction at the pilot to the establishment of a self-sustained diffusion flame anchored on the solid fuel surface is analyzed and described in detail and compared for several cases of reduced pressure and gravity. The influence of these parameters on the ignition delay time and the mass flux at ignition is also calculated and compared to experiments at 1 g for a range of sub-atmospheric pressures. The results show that reduced pressure and reduced gravity have similar effects on the piloted ignition of a solid fuel in low velocity flows, indicating that heating and pyrolysis of the solid are the primary mechanisms in the process. The results of this work may guide in the selection of materials in future space exploration vehicles and indicate when microgravity testing may be substituted by reduced ambient pressure conditions to analyze their ignition properties.

Combustion and Flame, Jul 1, 2011

Ignition of solid combustible materials can occur at atmospheric pressures lower than standard ei... more Ignition of solid combustible materials can occur at atmospheric pressures lower than standard either in high altitude environments or inside pressurized vehicles such as aircraft and spacecraft. NASA's latest space exploration vehicles have a cabin atmosphere of reduced pressure and increased oxygen concentration. Recent piloted ignition experiments indicate that ignition times are reduced under these environmental conditions compared to normal atmospheric conditions, suggesting that the critical mass flux at ignition may also be reduced. Both effects may result in an increased fire risk of combustible solid materials in reduced pressure environments that warrant further investigation. As a result, a series of experiments are conducted to explicitly measure fuel mass flux at ignition and ignition delay time as a function of ambient pressure for the piloted ignition of PMMA under external radiant heating. Experimental findings reveal that ignition time and the fuel mass flux at ignition decrease when ambient pressure is lowered, proving with the latter what earlier authors had inferred. It is concluded that the reduced pressure environment results in smaller convective heat losses from the heated material to the surroundings, allowing for the material to heat more rapidly and pyrolyze faster. It is also proposed that a lower mass flux of volatiles is required to reach the lean flammability limit of the gases near the pilot at reduced pressures, due mainly to a reduced oxygen concentration, an enlarged boundary layer, and a thicker fuel species profile.

SAE International Journal of Aerospace, Jul 12, 2009

SAE International Journal of Aerospace, Jun 29, 2008

Smoke detection experiments were conducted in the Microgravity Science Glovebox (MSG) on the Inte... more Smoke detection experiments were conducted in the Microgravity Science Glovebox (MSG) on the International Space Station (ISS) during Expedition 15 in an experiment entitled Smoke Aerosol Measurement Experiment (SAME). The preliminary results from these experiments are presented. In order to simulate detection of a prefire overheated-material event, samples of five different materials were heated to temperatures below the ignition point. The smoke generation conditions were controlled to provide repeatable sample surface temperatures and air flow conditions. The smoke properties were measured using particulate aerosol diagnostics that measure different moments of the size distribution. These statistics were combined to determine the count mean diameter which can be used to describe the overall smoke distribution.

Aerosol Science and Technology, Mar 6, 2015

A series of smoke experiments were carried out in the Microgravity Science Glovebox on the Intern... more A series of smoke experiments were carried out in the Microgravity Science Glovebox on the International Space Station (ISS) Facility to assess the impact of low-gravity conditions on the properties of the smoke aerosol. The smokes were generated by heating five different materials commonly used in space vehicles. This study focuses on the effects of flow and heating temperature for low-gravity conditions on the pyrolysis rate, the smoke plume structure, the smoke yield, the average particle size, and particle structure. Low-gravity conditions allowed a unique opportunity to study the smoke plume for zero external flow without the complication of buoyancy. The diameter of average mass increased on average by a factor of 1.9 and the morphology of the smoke changed from agglomerate with flow to spherical at no flow for one material. The no flow case is an important scenario in spacecraft where smoke could be generated by the overheating of electronic components in confined spaces. From electron microcopy of samples returned to earth, it was found that the smoke can form an agglomerate shape as well as a spherical shape, which had previously been the assumed shape. A possible explanation for the shape of the smoke generated by each material is presented.

42nd International Conference on Environmental Systems, Jul 15, 2012

Results are presented from the Reflight of the Smoke Aerosol Measurement Experiment (SAME-2) whic... more Results are presented from the Reflight of the Smoke Aerosol Measurement Experiment (SAME-2) which was conducted during Expedition 24 (July-September 2010). The reflight experiment built upon the results of the original flight during Expedition 15 by adding diagnostic measurements and expanding the test matrix. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The smoke was initially collected in an aging chamber to simulate the transport time from the smoke source to the detector. This effective transport time was varied by holding the smoke in the aging chamber for times ranging from 11 to 1800 s. Smoke particle samples were collected on Transmission Electron Microscope (TEM) grids for post-flight analysis. The TEM grids were analyzed to observe the particle morphology and size parameters. The diagnostics included a prototype two-moment smoke detector and three different measures of moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and, by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations can also be calculated. Overall the majority of the average smoke particle sizes were found to be in the 200 nm to 400 nm range with the quiescent cases producing some cases with substantially larger particles.

International Conference on Environmental Systems, Jul 7, 2019

An accidental fire involving the Lithium-Ion (Li-ion) battery in a laptop computer is one of the ... more An 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, overcharging 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 shortterm 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.

SAE technical paper series, Jul 12, 2009

46th AIAA Aerospace Sciences Meeting and Exhibit, Jan 7, 2008

Results from a recent smoke particle size measurement experiment conducted on the International S... more Results from a recent smoke particle size measurement experiment conducted on the International Space Station (ISS) are presented along with the results from a model of the transport of smoke in the ISS. The experimental results show that, for the materials tested, a substantial portion of the smoke particles are below 500 nm in diameter. The smoke transport model demonstrated that mixing dominates the smoke transport and that consequently detection times are longer than in normal gravity.

47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, Jan 5, 2009

Smoke particle size measurements were obtained under low-gravity conditions by overheating severa... more Smoke particle size measurements were obtained under low-gravity conditions by overheating several materials typical of those found in spacecraft. The measurements included integral measurements of the smoke particles and physical sample of the particles for Transmission Electron Microscope analysis. The integral moments were combined to obtain geometric mean particle sizes and geometric standard deviations. These results are presented with the details of the instrument calibrations. The experimental results show that, for the materials tested, a substantial portion of the smoke particles are below 500 nm in diameter.

Proceedings of the Combustion Institute, 2019

The flammability of combustible materials in spacecraft environments is of importance for fire sa... more The flammability of combustible materials in spacecraft environments is of importance for fire safety applications because the environmental conditions can greatly differ from those on earth, and a fire in a spacecraft could be catastrophic. Moreover, experimental testing in spacecraft environments can be difficult and expensive, so using ground-based tests to inform microgravity tests is vital. Reducing buoyancy effects by decreasing ambient pressure is a possible approach to simulate a spacecraft environment on earth. The objective of this work is to study the effect of pressure on material flammability, and by comparison with microgravity data, determine the extent to which reducing pressure can be used to simulate reduced gravity. Specifically, this work studies the effect of pressure and microgravity on upward/concurrent flame spread rates and flame appearance of a burning thin composite fabric made of 75% cotton and 25% fiberglass (Sibal). Experiments in normal gravity were conducted using pressures ranging between 100 and 30 kPa and a forced flow velocity of 20 cm/s. Microgravity experiments were conducted during NASA's Spacecraft Fire Experiment (Saffire), on board of the Orbital Corporation Cygnus spacecraft at 100 kPa and an air flow velocity of 20 cm/s. Results show that reductions of ambient pressure slow the flame spread over the fabric. As pressure is reduced, flame intensity is also reduced. Comparison with the concurrent flame spread rates in microgravity show that similar flame spread rates are obtained at around 30 kPa. The normal gravity and microgravity data is correlated in terms of a mixed convection non-dimensional parameter that describes the heat transferred from the flame to the solid surface. The correlation provides information about the similitudes of the flame spread process in variable pressure and reduced gravity environments, providing guidance for potential on-earth testing for fire safety design in spacecraft and space habitats.

SAE Technical Paper Series, Jul 11, 2005

The history and current status of spacecraft smoke detection is discussed including a review of t... more The history and current status of spacecraft smoke detection is discussed including a review of the state of understanding of the effect of gravity on the resultant smoke particle size. The results from a spacecraft experiment (Comparative Soot Diagnostics (CSD)) which measured ...

Aerosol Science and Technology, Mar 9, 2015

Combustion and Flame, Dec 1, 2012

ABSTRACT This work presents a numerical modeling investigation of the mechanisms controlling the ... more ABSTRACT This work presents a numerical modeling investigation of the mechanisms controlling the dependence on ambient pressure of the piloted ignition of a solid fuel under external radiant heating. The focus is to confirm the hypotheses and phenomenological arguments generated by previous experimental studies of the problem. For this purpose, the effect of ambient pressure on the piloted ignition of thermally irradiated samples of PMMA is modeled using the Fire Dynamics Simulator (FDS5) code. Two-dimensional simulations were performed using finite-rate single-step combustion kinetics in the gas-phase and a single-step Arrhenius reaction rate for the solid phase decomposition. Oxidative pyrolysis is not considered and the in-depth formed pyrolyzate is assumed to flow unrestricted through the PMMA. The objective is to understand the thermo-physical mechanisms leading to ignition and how they may be affected by a reduction in ambient pressure. The model is able to reproduce the main physical aspects of the piloted ignition of a solid fuel and confirms previous phenomenological explanations developed to describe recent experimental results at a range of ambient pressures. Reduced pressure environments result in: (1) shorter ignition times mainly due to reduced convective heat losses from the heated material to the surroundings, allowing for the material to heat more rapidly and pyrolyze faster; (2) a lower fuel mass flux at ignition, due primarily to a thicker thermal boundary layer and a thicker fuel species profile. The appearance of a premixed flame at the pilot, its propagation through the combustible mixture above the solid surface, and the subsequent sustained burning conditions are also explored in this work. The calculated ignition times and mass loss rates at ignition are compared to those measured experimentally in a laboratory-scale combustion wind tunnel. It is shown that with appropriate kinetic parameters the model qualitatively agrees with the experimental data.

SAE technical paper series, Jul 12, 2009

Combustion and Flame, Apr 1, 2015

The influence of environmental conditions on solid fuel ignition is of particular interest in spa... more The influence of environmental conditions on solid fuel ignition is of particular interest in spacecraft fire safety because of the large difference in environments between a spacecraft and earth (low gravity, low gas flow velocities, low pressure, elevated oxygen concentration). Considering that fire safety is essential when dealing with spacecraft vehicles, where space is confined and egress is difficult or almost impossible, low gravity fire initiation has a prominent importance. In addition to microgravity, low cabin pressure may further decrease the convective heat losses from the solid, leading to a faster heating of the materials and therefore raising the fire hazard on board. A numerical model developed with the CFD code Fire Dynamics Simulator (FDS) was used to analyze the effect of reduced gravity and ambient pressure on the transport processes taking place in the piloted ignition of an externally irradiated solid fuel. The model simultaneously solves the gas phase and solid phase conservation equations, using a one-step second order Arrhenius reaction rate for the gas phase kinetics and a one-step global Arrhenius reaction rate for the solid phase decomposition. The transition from an incipient premixed reaction at the pilot to the establishment of a self-sustained diffusion flame anchored on the solid fuel surface is analyzed and described in detail and compared for several cases of reduced pressure and gravity. The influence of these parameters on the ignition delay time and the mass flux at ignition is also calculated and compared to experiments at 1 g for a range of sub-atmospheric pressures. The results show that reduced pressure and reduced gravity have similar effects on the piloted ignition of a solid fuel in low velocity flows, indicating that heating and pyrolysis of the solid are the primary mechanisms in the process. The results of this work may guide in the selection of materials in future space exploration vehicles and indicate when microgravity testing may be substituted by reduced ambient pressure conditions to analyze their ignition properties.

Combustion and Flame, Jul 1, 2011

Ignition of solid combustible materials can occur at atmospheric pressures lower than standard ei... more Ignition of solid combustible materials can occur at atmospheric pressures lower than standard either in high altitude environments or inside pressurized vehicles such as aircraft and spacecraft. NASA's latest space exploration vehicles have a cabin atmosphere of reduced pressure and increased oxygen concentration. Recent piloted ignition experiments indicate that ignition times are reduced under these environmental conditions compared to normal atmospheric conditions, suggesting that the critical mass flux at ignition may also be reduced. Both effects may result in an increased fire risk of combustible solid materials in reduced pressure environments that warrant further investigation. As a result, a series of experiments are conducted to explicitly measure fuel mass flux at ignition and ignition delay time as a function of ambient pressure for the piloted ignition of PMMA under external radiant heating. Experimental findings reveal that ignition time and the fuel mass flux at ignition decrease when ambient pressure is lowered, proving with the latter what earlier authors had inferred. It is concluded that the reduced pressure environment results in smaller convective heat losses from the heated material to the surroundings, allowing for the material to heat more rapidly and pyrolyze faster. It is also proposed that a lower mass flux of volatiles is required to reach the lean flammability limit of the gases near the pilot at reduced pressures, due mainly to a reduced oxygen concentration, an enlarged boundary layer, and a thicker fuel species profile.

SAE International Journal of Aerospace, Jul 12, 2009

SAE International Journal of Aerospace, Jun 29, 2008

Smoke detection experiments were conducted in the Microgravity Science Glovebox (MSG) on the Inte... more Smoke detection experiments were conducted in the Microgravity Science Glovebox (MSG) on the International Space Station (ISS) during Expedition 15 in an experiment entitled Smoke Aerosol Measurement Experiment (SAME). The preliminary results from these experiments are presented. In order to simulate detection of a prefire overheated-material event, samples of five different materials were heated to temperatures below the ignition point. The smoke generation conditions were controlled to provide repeatable sample surface temperatures and air flow conditions. The smoke properties were measured using particulate aerosol diagnostics that measure different moments of the size distribution. These statistics were combined to determine the count mean diameter which can be used to describe the overall smoke distribution.

Aerosol Science and Technology, Mar 6, 2015

A series of smoke experiments were carried out in the Microgravity Science Glovebox on the Intern... more A series of smoke experiments were carried out in the Microgravity Science Glovebox on the International Space Station (ISS) Facility to assess the impact of low-gravity conditions on the properties of the smoke aerosol. The smokes were generated by heating five different materials commonly used in space vehicles. This study focuses on the effects of flow and heating temperature for low-gravity conditions on the pyrolysis rate, the smoke plume structure, the smoke yield, the average particle size, and particle structure. Low-gravity conditions allowed a unique opportunity to study the smoke plume for zero external flow without the complication of buoyancy. The diameter of average mass increased on average by a factor of 1.9 and the morphology of the smoke changed from agglomerate with flow to spherical at no flow for one material. The no flow case is an important scenario in spacecraft where smoke could be generated by the overheating of electronic components in confined spaces. From electron microcopy of samples returned to earth, it was found that the smoke can form an agglomerate shape as well as a spherical shape, which had previously been the assumed shape. A possible explanation for the shape of the smoke generated by each material is presented.