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Olson, Sandra

Publications and source records attributed to Olson, Sandra.

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Solid Fuel Ignition and Extinction (SoFIE) Project on ISS

The Solid Fuel Ignition and Extinction (SoFIE) project studies ignition and flammability of solid spacecraft materials (fuels) in practical geometries and realistic atmospheric conditions. It is an experiment insert designed for use within the existing Combustion Integrated Rack (CIR). The CIR chamber provides a level of containment and permits testing at variable oxygen concentrations and pressures representative of current and planned NASA Space Exploration Atmospheres. The applications of SoFIE include: (1) Determining safer selection of cabin materials and validating NASA materials flammability selection using 1-g test protocols for low-gravity fires, (2) Improving understanding of early fire growth behavior, (3) Validating material flammability numerical models, (4) Determining optimal suppression techniques for burning materials by diluents, flow reduction, and venting, (5) Obtaining burning behavior of actual engineering materials planned for spacecraft, (6) Developing corresponding models of microgravity flame spread, flammability, and extinction, and use the results to improve normal gravity combustion models for terrestrial applications. The hardware permits a wide range of solid-material combustion and fire suppression studies. It supports multiple investigations using common infrastructure including sample holders, flow control, test sections, external radiant heaters, igniters, and diagnostics. SoFIE has been developed to meet the requirements of five unique investigations. It is currently being built and slated to begin operations on the ISS in July 2021. Given the general capabilities of the hardware insert, it is intended to be used as a facility for future researchers who can propose to NASA for related solid combustion studies.

Ferkul, Paul↗
NASA NTRS2019

Infrared Measurements of Forward Heat Conduction during Simulated Microgravity Flame Spread in the Narrow Channel Apparatus

An infrared (IR) camera provides a way of examining temperature trends associated with simulated microgravity flame spread in the Narrow Channel Apparatus (NCA). The IR camera measures the surface temperature of solid poly methyl methacrylate (PMMA) fuel. These tests examine the forward conduction of heat ahead of the flame front in the non-thermally thin fuel.The NCA is a combustion wind tunnel that simulates a microgravity flame spread environment by employing a narrow gap between the fuel and ceiling of the device, limiting the effects of buoyancy. Test conditions of a 5 mm gap, mean opposed flow velocity of 15 cm/s, and fuel thickness of 3 mm are used.PMMA is selected as the fuel due to repeatability of test results, ease of computational modeling, and known combustion mechanics. Using specific lens and bandpass filter combinations the PMMA can be imaged as effectively opaque. The spectral emissivity for PMMA was calculated and incorporated into the calibration of the camera.Surface temperatures from the IR camera are compared to results from thermocouples embedded in the surface of the fuel. The IR camera results show that nontrivial forward conduction occurs during tests, and therefore must be included in computational models of the process.

Berry, Michael↗
NASA NTRS2017

Saffire: A Novel Approach to Study of Spacecraft Fire Safety Using Un-Manned Spacecraft

The Saffire Experiment represents the first test of spacecraft fires at a scale relevant to real spacecraft. Although large-scale fire tests on Earth are conducted for every type of habitable structure (buildings, planes, trains, automobiles, ships and mines) they had never been attempted in a space experiment for obvious reasons of practicality and safety. This is despite the fact that fire is a catastrophic hazard for spaceflight where the crew has very limited or no escape options. The spread and growth of a fire, combined with its interactions with the vehicle cannot be expected to scale linearly from small-scale test data, and so there is a substantial gap in our ability to predict the behavior of spacecraft fire and also its impact on the spacecraft habitability and operability. The experiments were performed aboard the Cygnus vehicle, a large unmanned resupply spacecraft to the International Space Station (ISS). The experiment was installed in the Cygnus vehicle, and remained dormant during docked operations. Once the vehicle was reloaded with ISS trash, it unberthed and moved to a separate orbit. The Saffire experiment was initiated by ground command and downlinked the data before the vehicle re-entered into the earth's atmosphere. The downloaded test data show resolved the question of whether flame growth will achieve a steady size and demonstrated that the size of the enclosure surrounding the sample has more impact on the flame spread than anticipated.

microgravity↗
NASA NTRS2017

Results of Large-Scale Spacecraft Flammability Tests

For the first time, a large-scale fire was intentionally set inside a spacecraft while in orbit. Testing in low gravity aboard spacecraft had been limited to samples of modest size: for thin fuels the longest samples burned were around 15 cm in length and thick fuel samples have been even smaller. This is despite the fact that fire is a catastrophic hazard for spaceflight and the spread and growth of a fire, combined with its interactions with the vehicle cannot be expected to scale linearly. While every type of occupied structure on earth has been the subject of full scale fire testing, this had never been attempted in space owing to the complexity, cost, risk and absence of a safe location. Thus, there is a gap in knowledge of fire behavior in spacecraft. The recent utilization of large, unmanned, resupply craft has provided the needed capability: a habitable but unoccupied spacecraft in low earth orbit. One such vehicle was used to study the flame spread over a 94 x 40.6 cm thin charring solid (fiberglasscotton fabric). The sample was an order of magnitude larger than anything studied to date in microgravity and was of sufficient scale that it consumed 1.5 of the available oxygen. The experiment which is called Saffire consisted of two tests, forward or concurrent flame spread (with the direction of flow) and opposed flame spread (against the direction of flow). The average forced air speed was 20 cms. For the concurrent flame spread test, the flame size remained constrained after the ignition transient, which is not the case in 1-g. These results were qualitatively different from those on earth where an upward-spreading flame on a sample of this size accelerates and grows. In addition, a curious effect of the chamber size is noted. Compared to previous microgravity work in smaller tunnels, the flame in the larger tunnel spread more slowly, even for a wider sample. This is attributed to the effect of flow acceleration in the smaller tunnels as a result of hot gas expansion. These results clearly demonstrate the unique features of purely forced flow in microgravity on flame spread, the dependence of flame behavior on the scale of the experiment, and the importance of full-scale testing for spacecraft fire safety.

microgravity↗
NASA NTRS2014

Large-Scale Spacecraft Fire Safety Tests

An international collaborative program is underway to address open issues in spacecraft fire safety. Because of limited access to long-term low-gravity conditions and the small volume generally allotted for these experiments, there have been relatively few experiments that directly study spacecraft fire safety under low-gravity conditions. Furthermore, none of these experiments have studied sample sizes and environment conditions typical of those expected in a spacecraft fire. The major constraint has been the size of the sample, with prior experiments limited to samples of the order of 10 cm in length and width or smaller. This lack of experimental data forces 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. This, combined with the differences caused by the confined spacecraft environment, necessitates practical scale spacecraft fire safety research to mitigate risks for future space missions. To address this issue, a large-scale spacecraft fire experiment is under development by NASA and an international team of investigators. This poster presents the objectives, status, and concept of this collaborative international project (Saffire). The project plan is to conduct fire safety experiments on three sequential flights of an unmanned ISS re-supply spacecraft (the Orbital Cygnus vehicle) after they have completed their delivery of cargo to the ISS and have begun their return journeys to earth. On two flights (Saffire-1 and Saffire-3), the experiment will consist of a flame spread test involving a meter-scale sample ignited in the pressurized volume of the spacecraft and allowed to burn to completion while measurements are made. On one of the flights (Saffire-2), 9 smaller (5 x 30 cm) samples will be tested to evaluate NASAs material flammability screening tests. The first flight (Saffire-1) is scheduled for July 2015 with the other two following at six-month intervals. A computer modeling effort will complement the experimental effort. 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. This will facilitate the first examination of fire behavior on a scale that is relevant to spacecraft fire safety and will provide unique data for fire model validation.

Combustion↗
NASA NTRS2012

Flammability Aspects of a Cotton-Fiberglass Fabric in Opposed and Concurrent Airflow in Microgravity

Microgravity combustion tests burning fabric samples were performed aboard the International Space Station. The cotton-fiberglass blend samples were mounted inside a small wind tunnel which could impose air flow speeds up to 40 cm/s. The wind tunnel was installed in the Microgravity Science Glovebox which supplied power, imaging, and a level of containment. The effects of air flow speed on flame appearance, flame growth, and spread rates were determined in both the opposed and concurrent flow configuration. For the opposed flow configuration, the flame quickly reached steady spread for each flow speed, and the spread rate was fastest at an intermediate value of flow speed. These tests show the enhanced flammability in microgravity for this geometry, since, in normal gravity air, a flame self-extinguishes in the opposed flow geometry (downward flame spread). In the concurrent flow configuration, flame size grew with time during the tests. A limiting length and steady spread rate were obtained only in low flow speeds ( 10 cm/s) for the short-length samples that fit in the small wind tunnel. For these conditions, flame spread rate increased linearly with increasing flow. This is the first time that detailed transient flame growth data was obtained in purely forced flows in microgravity. In addition, by decreasing flow speed to a very low value (around 1 cm/s), quenching extinction was observed. The valuable results from these long-duration experiments validate a number of theoretical predictions and also provide the data for a transient flame growth model under development.

Ferkul, Paul V.↗
NASA NTRS2011

Convective Heat Transfer Scaling of Ignition Delay and Burning Rate with Heat Flux and Stretch Rate in the Equivalent Low Stretch Apparatus

To better evaluate the buoyant contributions to the convective cooling (or heating) inherent in normal-gravity material flammability test methods, we derive a convective heat transfer correlation that can be used to account for the forced convective stretch effects on the net radiant heat flux for both ignition delay time and burning rate. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone heater to minimize buoyant effects while at the same time providing a forced stagnation flow on the sample, which ignites and burns as a ceiling fire. Ignition delay and burning rate data is correlated with incident heat flux and convective heat transfer and compared to results from other test methods and fuel geometries using similarity to determine the equivalent stretch rates and thus convective cooling (or heating) rates for those geometries. With this correlation methodology, buoyant effects inherent in normal gravity material flammability test methods can be estimated, to better apply the test results to low stretch environments relevant to spacecraft material selection.

Olson, Sandra↗
NASA NTRS2001

Radiation-Driven Flame Spread Over Thermally-Thick Fuels in Quiescent Microgravity Environments

Microgravity experiments on flame spread over thermally thick fuels were conducted using foam fuels to obtain low density and thermal conductivity, and thus large spread rate (Sf) compared to dense fuels such as PMMA. This scheme enabled meaningful results to lie obtained even in 2.2 second drop tower experiments. It was found that, in contrast conventional understanding; steady spread can occur over thick fuels in quiescent microgravity environments, especially when a radiatively active diluent gas such as CO2 is employed. This is proposed to be due to radiative transfer from the flame to the fuel surface. Additionally, the transition from thermally thick to thermally thin behavior with decreasing bed thickness is demonstrated.

Honda, Linton K.↗
NASA NTRS2000

Testing and Selection of Fire-Resistant Materials for Spacecraft Use

Spacecraft fire-safety strategy emphasizes prevention, mostly through the selection of onboard items classified accord- ing to their fire resistance. The principal NASA acceptance tests described in this paper assess the flammability of materials and components under "worst-case" normal-gravity conditions of upward flame spread in controlled-oxygen atmospheres. Tests conducted on the ground, however, cannot duplicate the unique fire characteristics in the nonbuoyant low-gravity environment of orbiting spacecraft. Research shows that flammability an fire-spread rates in low gravity are sensitive to forced convection (ventilation flows) and atmospheric-oxygen concentration. These research results are helping to define new material-screening test methods that will better evaluate material performance in spacecraft.

Friedman, Robert↗
NASA NTRS1999

Ignition, Transition, Flame Spread in Multidimensional Configurations in Microgravity

In the inhabited quarters of orbiting spacecraft, fire is a greatly feared hazard. Thus, the fire safety strategy in a spacecraft is (1) to keep any fire as small as possible, (2) to detect any fire as early as possible, and (3) to extinguish any fire as quickly as possible. This suggests that a material which undergoes a momentary ignition might be tolerable but a material which permits a transition from a localized ignition to flame spread would significantly increase the fire hazard in a spacecraft. If the transition does not take place, fire growth does not occur. Therefore, it is critical to understand what process controls the transition. Many previous works have studied ignition and flame spread separately or were limited to a two-dimensional configuration. In this study, time-dependent phenomena of the transition over a thermally thin sample is studied experimentally and theoretically in two- and three-dimensional (2D,3D) configurations. Furthermore, localized ignition can be initiated at the center portion of thermally thin paper sample instead of at one end of the sample. Thus, the transition to flame spread could occur either toward upstream or downstream or both directions simultaneously with an external flow. In this presentation, the difference in the transition between the 3D and 2D configurations is explained with the numerically calculated data. For sufficiently narrow samples edge effects exist. Some results on this issue are presented. New analysis of the surface smoldering experiments conducted in the space shuttle STS-75 flight is also described.

Kashiwagi, Takashi↗