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NASA NTRS2015

Buoyant Effects on the Flammability of Silicone Samples Planned for the Spacecraft Fire Experiment (Saffire)

Flammability experiments on silicone samples were conducted in anticipation of the Spacecraft Fire Experiment (Saffire). The sample geometry was chosen to match the NASA 6001 Test 1 specification, namely 5 cm wide by 30 cm tall. Four thicknesses of silicone (0.25, 0.36, 0.61 and 1.00 mm) were examined. Tests included traditional upward buoyant flame spread using Test 1 procedures, downward opposed-flow flame spread, horizontal and angled flame spread, and forced-flow upward and downward flame spread. In addition to these configurations, upward and downward tests were conducted in a chamber with varying oxygen concentrations. In the upward buoyant flame spread tests, the flame generally did not burn the entire sample. As thickness was increased, the flame spread distance decreased before flame extinguishment. For the thickest sample, ignition could not be achieved. In the downward tests, the two thinnest samples permitted the flame to burn the entire sample, but the spread rate was lower compared to the corresponding upward values. The other two thicknesses could not be ignited in the downward configuration. The increased flammability for downward spreading flames relative to upward ones is uncommon. The two thinnest samples also burned completely in the horizontal configuration, as well as at angles up to 75 degrees from the horizontal. Upward tests in air with an added forced flow were more flammable. The upward and downward flammability behavior was compared in atmospheres of varying oxygen concentration to determine a maximum oxygen concentration for each configuration. Complementary analyses using EDS, TGA, and SEM techniques suggest the importance of the silica layer deposited downstream onto the unburned sample surface.

Flammability↗

NASA NTRS1978

Characterization of flammability properties of some thermoplastic and thermoset resins

The thermochemical and flammability properties of some thermally stable polymers considered for use in aircraft interiors are described. The properties studied include: (1) thermomechanical properties such as glass transition and melt temperature; (2) dynamic thermogravimetric analysis in anaerobic environment; (3) flammability properties such as oxygen index, flame spread, and smoke evolution; and (4) selected physical properties. The thermoplastic polymers evaluated included polyphenylene sulfide, polyaryl sulfone, 9,9-bis(4-hydroxyphenyl)-fluorene polycarbonate-poly(dimethylsiloxane) and polyether sulfone. The thermoset polymers evaluated included epoxy, bismaleimide, a modified phenolic and polyaromatic melamine resin. These resins were primarily used in the fabrication of glass reinforced prepregs for the construction of experimental panels. Test results and relative rankings of some of the flammability parameters are presented and the relationship of the molecular structure, char yield, and flammability properties of these polymers are discussed.

Kourtides, D. A.↗

NASA NTRS2003

Correlating Flammability of Materials with FTIR Analysis Test Results

The purpose of this experiment was to correlate flammability data with FTIR test results. Kydex 100 is a blend of chlorinated polyvinyl chloride and polymethylmethacrylate, with some filler materials. Samples supplied were 0.125 in. thick. 10 samples were taken from a sheet of Kydex and analyzed for flammability and by FTIR spectroscopy. This material was utilized as a round robin sample for flammability testing. The flammability test results were found to vary across the same sheet.

Moore, Robin↗

NASA NTRS2004

Organizing Questions for Reduced-Gravity Flammability

A team consisting of of the Microgravity Flight Project Scientists for solid flammability experiments has been reviewing and prioritizing a set of organizing questions for fire prevention (material flammability).In particular the team has been charged with determining:What experiments must be conducted to best answer these questions, and can some of the quest ions be answered using existing/planned hardware or experimental concepts?Is the NASA STD 6001, Test 1 configuration conservative or non-conservative in assessing material flammability in reduced gravity?NASA ST D 6001, Test 1 is an upward flammability test, considered the most stringent test in normal gravity. A material that passes this test would most likely not burn in a quiescent microgravity environment.A forced ignition and spread test is described.

Miller, Fletcher↗

NASA NTRS2004

Spacecraft and Navy Materials Flammability: Review of Some Concepts and Test Methods

The agenda covered by this viewgraph presentation includes: 1) Concepts of Spacecraft Fire Safety; 2) Spacecraft materials flammability test methods; 3) Evaluation of flight hardware flammability; 4) Review of flammability data in conditions of interest to the Navy; 5) Overview of some flammability test methods recommended for the Navy.

Hirsch, David↗

NASA NTRS2007

Oxygen Concentration Flammability Thresholds of Selected Aerospace Materials Considered for the Constellation Program

Materials selection for spacecraft is based on an upward flammability test conducted in a quiescent environment in the highest expected oxygen concentration environment. The test conditions and its pass/fail test logic do not provide sufficient quantitative materials flammability information for an advanced space exploration program. A modified approach has been suggested determination of materials self-extinguishment limits. The flammability threshold information will allow NASA to identify materials with increased flammability risk from oxygen concentration and total pressure changes, minimize potential impacts, and allow for development of sound requirements for new spacecraft and extraterrestrial landers and habitats. This paper provides data on oxygen concentration self-extinguishment limits under quiescent conditions for selected materials considered for the Constellation Program.

Hirsch, David B.↗

NASA NTRS2005

An Approach to Evaluate Precision and Inter-Laboratory Variability of Flammability Test Methods for Aerospace Materials

Materials selection for spacecraft is based on conventional flammability or ignition sensitivity acceptance tests. Current procedures for determining the inter-laboratory repeatability and reproducibility of aerospace materials flammability tests are not considering the dependence of data variability on test conditions and consequently attempts to characterize the precision of these methods were not successful. The inter-laboratory data variability is determined with tests conducted under arbitrary conditions, which consequently may not provide sufficient information to enable adequate determination of a method's precision. For evaluating the precision of NASA's flammability test methods, the protocol recommended includes selecting critical parameters and determining the 50% failure point by considering the specific failure criteria of each method using the critical parameter as a variable. Upon performing inter-laboratory round robin testing using this approach, the laboratories' performance could be evaluated by comparing the repeatability of the 50% failure point and/or the repeatability of critical conditions where the probabilities of passing and failing are unity, i.e., the transition zone repeatability. When a sufficient amount of data has been acquired with this method, an adequate estimation of precision of aerospace materials flammability test methods will be possible.

Hirsch, David↗

NASA NTRS2009

Applicability of Aerospace Materials Ground Flammability Test Data to Spacecraft Environments Theory and Applied Technologies

This slide presentation reviews the use of ground test data in reference to flammability to spacecraft environments. It reviews the current approach to spacecraft fire safety, the challenges to fire safety that the Constellation program poses, the current trends in the evaluation of the Constellation materials flammability, and the correlation of test data from ground flammability tests with the spacecraft environment. Included is a proposal for testing and the design of experiments to test the flammability of materials under similar spacecraft conditions.

Hirsch, David↗

NASA NTRS2010

Pressure Flammability Thresholds in Oxygen of Selected Aerospace Materials

The experimental approach consisted of concentrating the testing in the flammability transition zone following the Bruceton Up-and-Down Method. For attribute data, the method has been shown to be very repeatable and most efficient. Other methods for characterization of critical levels (Karberand Probit) were also considered. The data yielded the upward limiting pressure index (ULPI), the pressure level where approx.50% of materials self-extinguish in a given environment.Parametric flammability thresholds other than oxygen concentration can be determined with the methodology proposed for evaluating the MOC when extinguishment occurs. In this case, a pressure threshold in 99.8% oxygen was determined with the methodology and found to be 0.4 to 0.9 psia for typical spacecraft materials. Correlation of flammability thresholds obtained with chemical, hot wire, and other ignition sources will be conducted to provide recommendations for using alternate ignition sources to evaluate flammability of aerospace materials.

Hirsch, David↗

NASA NTRS2011

Interstage Flammability Analysis Approach

The Interstage of the Ares I launch platform houses several key components which are on standby during First Stage operation: the Reaction Control System (ReCS), the Upper Stage (US) Thrust Vector Control (TVC) and the J-2X with the Main Propulsion System (MPS) propellant feed system. Therefore potentially dangerous leaks of propellants could develop. The Interstage leaks analysis addresses the concerns of localized mixing of hydrogen and oxygen gases to produce deflagration zones in the Interstage of the Ares I launch vehicle during First Stage operation. This report details the approach taken to accomplish the analysis. Specified leakage profiles and actual flammability results are not presented due to proprietary and security restrictions. The interior volume formed by the Interstage walls, bounding interfaces with the Upper and First Stages, and surrounding the J2-X engine was modeled using Loci-CHEM to assess the potential for flammable gas mixtures to develop during First Stage operations. The transient analysis included a derived flammability indicator based on mixture ratios to maintain achievable simulation times. Validation of results was based on a comparison to Interstage pressure profiles outlined in prior NASA studies. The approach proved useful in the bounding of flammability risk in supporting program hazard reviews.

Little, Jeffrey K.↗

NASA NTRS2012

Evaluating Material Flammability in Microgravity and Martian Gravity Compared to the NASA Standard Normal Gravity Test

Drop tower tests are conducted at Martian gravity to determine the flammability of three materials compared to previous tests in other normal gravity and reduced gravity environments. The comparison is made with consideration of a modified NASA standard test protocol. Material flammability limits in the different gravity and flow environments are tabulated to determine the factor of safety associated with normal gravity flammability screening. Previous testing at microgravity and Lunar gravity indicated that some materials burned to lower oxygen concentrations in low gravity than in normal gravity, although the low g extinction limit criteria are not the same as 1g due to time constraints in drop testing. Similarly, the data presented in this paper for Martian gravity suggest that there is a gravity level below Earth s at which materials burn more readily than on Earth. If proven for more materials, this may indicate the need to include a factor of safety on 1g flammability limits.

Oslon, Sandra. L.↗

NASA NTRS2014

Non-Flammable Containment Bag and Enclosure Development for International Space Station Use

Work conducted on the International Space Station (ISS) requires the use of a significant quantity of containment bags to hold specimens, equipment, waste, and other material. The bags are in many shapes and sizes, and are typically manufactured from polyethylene materials. The amount of bags being used on ISS has grown to the point where fire safety has become a concern because of the flammability of polyethylene. Recently, a new re‐sealable bag design has been developed that is manufactured from a specialized non‐flammable material called Armorflex 301 that was designed specifically for this application. Besides being non‐flammable, Armorflex 301 is also FDA compliant, clear, flexible, and damage tolerant. The bags can be made with closure mechanisms that resemble ZipLoc® bags, or can be open top. Sample bags have been laboratory tested by NASA to verify materials properties, and evaluated by astronauts on the ISS in 2012. Flexloc bag manufacturing will commence in 2014 to support a transition away from polyethylene on ISS. In addition to re‐sealable bags, other larger containment systems such as flexible gloveboxes, deployable clean rooms, and other devices manufactured from Armorflex 301 are being explored for use on ISS and in similar confined space locations where flammability is an issue. This paper will describe the development of the Armorflex 301 material, the Flexloc bag, and other containment systems being explored for use in confined areas

Inamdar, Sunil↗

NASA NTRS2014

Flammability Configuration Analysis for Spacecraft Applications

Fire is one of the many potentially catastrophic hazards associated with the operation of crewed spacecraft. A major lesson learned by NASA from the Apollo 204 fire in 1966 was that ignition sources in an electrically powered vehicle should and can be minimized, but can never be eliminated completely. For this reason, spacecraft fire control is based on minimizing potential ignition sources and eliminating materials that can propagate fire. Fire extinguishers are always provided on crewed spacecraft, but are not considered as part of the fire control process. "Eliminating materials that can propagate fire" does not mean eliminating all flammable materials - the cost of designing and building spacecraft using only nonflammable materials is extraordinary and unnecessary. It means controlling the quantity and configuration of such materials to eliminate potential fire propagation paths and thus ensure that any fire would be small, localized, and isolated, and would self-extinguish without harm to the crew. Over the years, NASA has developed many solutions for controlling the configuration of flammable materials (and potentially flammable materials in commercial "off-the-shelf" hardware) so that they can be used safely in air and oxygen-enriched environments in crewed spacecraft. This document describes and explains these design solutions so payload customers and other organizations can use them in designing safe and cost-effective flight hardware. Proper application of these guidelines will produce acceptable flammability configurations for hardware located in any compartment of the International Space Station or other program crewed vehicles and habitats. However, use of these guidelines does not exempt hardware organizations of the responsibility for safety of the hardware under their control.

Pedley, Michael D.↗

NASA NTRS2018

Development and Flammability Testing of Magnesium Alloys for Space Applications

This project will be comparing the flammability of select lightweight Mg alloys for use in a simulated ISS environment. It will also be determining the factors that influence flammability of selected alloys in elevated oxygen, including the formation of an oxide layer. The significance of this work is that such alloys can reduce weight saving by up to 30%. This work is adding to knowledge base of lightweight Mg alloys for possible future applications, as no previous flammability testing of Mg alloys have been conducted at elevated oxygen concentrations.

International Space Station↗

NASA NTRS1971

Flammability testing of components

Flammability testing of components in the design of Apollo spacecraft is discussed. The purpose of component flammability testing was to determine the flammability characteristics of a variety of different sizes, shapes, and configurations of nonmetallic materials of similar or different types that make up a functional assembly, subsystem, or system in a spacecraft. The test criteria and requirements for the nonmetallic materials are presented.

Primeaux, G. R.↗

NASA NTRS1982

Antimisting kerosene atomization and flammability

Various parameters found to affect the flammability of antimisting kerosene (Jet A + polymer additive) are investigated. Digital image processing was integrated into a technique for measurement of fuel spray characteristics. This technique was developed to avoid many of the error sources inherent to other spray assessment techniques and was applied to the study of engine fuel nozzle atomization performance with Jet A and antimisting fuel. Aircraft accident fuel spill and ignition dynamics were modeled in a steady state simulator allowing flammability to be measured as a function of airspeed, fuel flow rate, fuel jet Reynolds number and polymer concentration. The digital imaging technique was employed to measure spray characteristics in this simulation and these results were related to flammability test results. Scaling relationships were investigated through correlation of experimental results with characteristic dimensions spanning more than two orders of magnitude.

Fleeter, R.↗

NASA NTRS1983

Rheological behavior of FM-9 solutions and correlation with flammability test results and interpretations

The rheological behavior of progressively shear thickening FM-9 solutions, a time-dependent shear thickening material with characteristics of threshold behavior, is investigated as part of a study of the rheological properties of antimisting jet fuel. Flammability test results and test configurations from various sources are evaluated. A correlation is obtained between the rheological behavior and the flammability tests such that, for a given system, such as a fixed solvent system and the FM-9 polymer system, the flammability criterion can be applied to a wide range of concentrations and temperatures.

Peng, S. T. J.↗

NASA NTRS1983

Antimisting fuel breakup and flammability

The breakup behavior and flammability of antimisting turbine fuels subjected to aerodynamic shear are investigated. Fuels tested were Jet A containing 0.3% FM-9 polymer at various levels of degradation ranging from virgin AMK to neat Jet A. The misting behavior of the fuels was quantified by droplet size distribution measurements. A technique based on high resolution laser photography and digital image processing of photographic records for rapid determination of droplet size distribution was developed. The flammability of flowing droplet-air mixtures was quantified by direct measurements of temperature rise in a flame established in the wake of a continuous ignition source. The temperature rise measurements were correlated with droplet size measurements. The flame anchoring phenomenon associated with the breakup of a liquid fuel in the wake of bluff body was shown to be important in the context of a survivable crash scenario. A pass/fail criterion for flammability testing of antimisting fuels, based on this flame-anchoring phenomenon, was proposed. The role of various ignition sources and their intensity in ignition and post-ignition behavior of antimisting fuels was also investigated.

Parikh, P.↗