NOTE: End date changed to 7/31/2022 per PI (Ed., 10/5/20)

NOTE: Changed end date to 3/31/2021 per PI (Ed., 6/3/19)

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test methods such as NASA-STD-6001B.

Experiment 1-2 was conducted during the 2022 operations. NASA has received data from JAXA for analysis in collaboration with the JAXA Principal Investigator (PI) Torikai. A manuscript is being drafted of the parabolic aircraft test campaign collaboration.

The 2022 annual international Flammability Limits At Reduced-g Experiment (FLARE) workshop, originally planned to be held in Tsukuba, Japan, was held Sept. 6-8, 2022. [Ed. Note: see FY22 report for additional information.] The next workshop is scheduled for Sept. 2023 in Tsukuba, Japan.

NOTE: End date changed to 7/31/2022 per PI (Ed., 10/5/20)

NOTE: Changed end date to 3/31/2021 per PI (Ed., 6/3/19)

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test methods such as NASA-STD-6001B.

Experiment 1-2 was conducted during the 2022 operations. I am receiving the data from the Japan Aerospace Exploration Agency (JAXA) for analysis in collaboration with the JAXA Principal Investigator, Hirosaki Torikai. I am also working on a manuscript of our parabolic aircraft test campaign collaboration. My experiment is 1-3 and will operate from June through August, 2023.

The 2022 annual international Flammability Limits At Reduced-g Experiment (FLARE) workshop, originally planned to be held in Tsukuba, Japan, was held virtually again this year, from Sept. 6-8, 2022, due to the coronavirus pandemic. Participants were asked to record their talks to be viewed in advance of the scheduled workshop so that discussion during the workshop could focus on international collaboration efforts and discussion of the talks. The next workshop is scheduled for Sept. 2023 in Tsukuba, Japan.

NOTE: End date changed to 7/31/2022 per PI (Ed., 10/5/20)

NOTE: Changed end date to 3/31/2021 per PI (Ed., 6/3/19)

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test methods such as NASA-STD-6001B.

The Solid Combustion Experiment Module (SCEM) was installed in the Multipurpose Small Payload Rack (MSPR) in Jan.-Feb. 2021. Hardware checkout occurred starting in February. In early April, the control computer froze, and subsequent troubleshooting determined that the solid-state hard drive (SSD) on the motherboard had failed. JAXA decided in September 2021 to re-stow the hardware after removing the failed motherboard for return to Earth for a forensic analysis. A replacement motherboard with both an SSD and a standard hard drive will be built and launched to the ISS in Feb. 2022. A second motherboard will be built based upon the forensic analysis conclusions and a new interface plate for easier access to the computer for debugging will be launched later, if warranted.

A preliminary new schedule, which depends on coordination with other experiments scheduled to go in the MSPR, is that setup and checkout could start in June 2022, and experiments could start as early as July 2022. The operations may need to be split up to accommodate other experiments in the MSPR.

The 2021 annual international Flammability Limits At Reduced-g Experiment (FLARE) workshop, originally planned to be held in Tsukuba, Japan, was held virtually again this year due to the coronavirus pandemic. Participants were asked to record their talks to be viewed in advance of the scheduled workshop so that discussion during the workshop could focus on international collaboration efforts and discussion of the talks. The next workshop is scheduled for Sept. 2022 in Tsukuba, Japan.

Due to the pandemic and mandatory telework, no testing was possible at NASA Glenn Research Center this past year.

NOTE: Changed end date to 3/31/2021 per PI (Ed., 6/3/19)

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

At the FLARE workshop, it was announced that the setup of the hardware on ISS will occur in Nov.-Dec. 2020, with experiment operations starting as early as Dec. 2020. JAXA astronaut Soichi Noguchi, who is launching on Space-X Crew-1, will be doing the setup and initial checkout tests later this year.

Additional microgravity drop tower tests at low pressure were performed prior to the mandatory telework situation to add to the results from last year’s low-gravity aircraft parabolic trajectory tests and atmospheric microgravity drop tower experiments. The goal of these tests is to determine blowoff extinction limits for thin sheets of bleached grade#90 cheesecloth as a function of oxygen concentration flow velocity, and now pressure. To avoid confusion with ignition limits, the flames were ignited under a flammable condition, and the conditions were changed (flow, oxygen) to determine if the flame would blow off. These blowoff boundaries will help in the selection of the flight experiment conditions.

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

Low-gravity aircraft parabolic trajectories and microgravity drop tower experiments have been conducted to study blowoff extinction limits for thin sheets of bleached grade#90 cheesecloth. To avoid confusion with ignition limits, the flames were ignited under a flammable condition, and the conditions were changed (flow, oxygen) to determine if the flame would blow off. Preliminary blowoff boundaries were mapped for both opposed and concurrent flow. The concurrent blowoff boundary occurs at lower oxygen concentrations for the same ambient flow velocities than the opposed blowoff boundary, and the slopes do not appear to be parallel. This is hypothesized to be due to the a higher Damkohler number at the flame base of a concurrent flame (stagnation flow) than at the leading edge of an opposed flow flame (boundary layer flow) under the same flows.

Local blowoffs were observed during testing, where a significant fraction of the opposed flame width extinguishes, and where one whole side of the concurrent flame blows off. Often, the remaining flame will again spread to the affected area, only to have the event occur, often repeatedly, during the test. Due to the stochastic nature of the local extinctions along the 2D stabilization region [leading edge (opposed flow), flame base (concurrent flow)], they do not always result in total extinction of the flame, indicating the flammability boundary is a band rather than a sharp boundary of conditions (flow, oxygen concentration).

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

A series of NASA Glenn Zero Gravity Research Facility (ZGRF) tests were continued this year to determine the approximate high velocity blowoff limits for thin cotton fabrics for both opposed and some concurrent flow conditions. For concurrent flow, flame spread was obtained over the accessible range of flow at 12% oxygen at one atmosphere pressure. These results were shared with the Flammability Limits At Reduced-g Experiment (FLARE) Co-Investigator while planning his aircraft campaigns.

Concurrent blowoff parabolic aircraft testing was conducted in Japan in the G-II aircraft in August and September, 2018. A number of blowoff conditions were obtained as well as flame spread. The data was shared, and analysis is underway of the flame spread and blowoff onset. Concurrent blowoff of thin cotton sheet occurs frequently on only on one side of the sample at near-limit conditions. Often, during a single test, the flame will blow off one side only to re-form, wrapping around the base from the flame on the other side. This is possible because the cotton fabric burns away at the base. Definitive blowoff occurs when both sides of the flame blow off. This one-sided blowoff behavior creates a larger band of uncertainty along the blowoff boundary.

A successful Technical Interchange Meeting (TIM) was held at NASA White Sands Test Facility (WSTF) Aug. 22-23, 2018. The FLARE project status and the ISO standardization plan were discussed. Extensive data was shared on JAXA parabolic aircraft testing and 1g blowoff testing of practical materials (Nomex HT90-40, Polycarbonate, Kevlar, Kapton, Conex, Technora, Kydex). NASA has proposed an improved upward flame spread Test 1 of NASA STD 6001B which evaluates the upward limiting oxygen index and maximum oxygen concentration (ULOI/MOC) of a material in 1g. JAXA is pursuing a downward burning limiting oxygen index (LOI) method as a potential alternative index for flammability. For either of these methods, there is a discrepancy in the actual flammability limit in microgravity since material flammability can be higher in microgravity.

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

An international workshop was held at European Space Research and Technology Centre (ESTEC), in Noordwick, Netherlands in January, 2017. At that meeting, the science teams presented their status to the group. In addition, plans for a parabolic aircraft campaign were discussed.

A series of NASA Glenn Zero Gravity Research Facility (ZGRF) tests were continued this year with the updated Microgravity Wind Tunnel, which includes a new longer test section and two high resolution GIGE cameras. The tests were performed to determine the approximate high velocity blowoff limits for thin cotton fabrics for both opposed and some concurrent flow conditions. The materials were ignited in normal gravity and then the experiment was dropped. The ambient gas oxidizer concentration was switched to the test atmosphere to determine if the flame could survive in the reduced oxygen concentration during the 5.18 second drop.

For opposed flow flame spread, the lowest section of the flammability boundary is filled in with microgravity drop data, and the wings of the boundary include normal gravity blowoff data from Fernandez-Pello, Ray, and Glassman (18th Symposium on Combustion, 1981) and Solid Surface Combustion Experiment (SSCE) quiescent microgravity data from Ramachandra et al. (Combustion and Flame 100, 1995). The minimum in the flammability boundary is at an oxygen concentration of ~13% O2 at approximately 10 cm/s, which is in the range of spacecraft ventilation flow velocities.

The normal gravity buoyant only limit occurs at a limiting oxygen concentration of ~15.9% O2, significantly higher than the observed minimum in the flammability boundary. This demonstrates how a normal gravity test is not a conservative test to evaluate microgravity flammability. However, it may be possible to account for the buoyant flow and correct the data to predict a conservative microgravity limit, since the blowoff boundary is linear with flow down to very low velocities. If the blowoff boundary is determined via 1g testing, and the buoyant flow contribution is included, the minimum in the flammability boundary can be estimated by extrapolating to zero flow.

Some concurrent ZGRF tests have also been conducted near the bottom of the flammability boundary, and the blowoff limits are even lower than opposed limits.

Steady flames are obtained as low as 12% O2. The 12% O2 concurrent ZGRF flame spread tests were tracked to determine if they appeared to be stable. The flame length appears to grow linearly with flow, and the flame spread rate increases linearly with flow as well. This is in agreement with numerical modelling (Ferkul and T'ien, 1994). The flame length increases linearly with the flame spread rate, in agreement with the Markstein and deRis paper (1973) where they indicate a concurrent flame over a given material should have a constant burnout time (length/spread rate) for fixed oxygen and pressure.

References

Fernandez-Pello, A. C., Ray, S. R., and Glassman, I. (1981). "Flame spread in an opposed forced flow: the effect of ambient oxygen concentration." Symposium (International) on Combustion. Vol. 18. No. 1. Elsevier.

Ramachandra, P. A., Altenkirch, R. A., Bhattacharjee, S., Tang, L., Sacksteder, K., & Wolverton, M. K. (1995). The behavior of flames spreading over thin solids in microgravity. Combustion and flame, 100(1), 71-84.

Ferkul, P. V., and J. S. T'ien. (1994). "A model of low-speed concurrent flow flame spread over a thin fuel." Combustion science and technology 99.4-6 : 345-370.

Markstein, G. H., & De Ris, J. (1973, January). Upward fire spread over textiles. In Symposium (International) on Combustion (Vol. 14, No. 1, pp. 1085-1097). Elsevier.

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

A series of NASA Glenn Zero Gravity Research Facility (ZGRF) tests were performed this year with the updated Microgravity Wind Tunnel, which includes a new longer test section and two high resolution GIGE cameras. The tests were performed to determine the approximate high velocity blowoff limits for thin cotton fabrics. The materials were ignited in normal gravity and then the experiment was dropped. The ambient gas oxidizer concentration was switched to the test atmosphere to determine if the flame could survive in the reduced oxygen concentration during the 5.18 second drop.

For opposed flow flame spread, the low gravity blowoff limits were determined at three oxygen concentrations. These were compared to normal gravity data. The 1g data indicates the limiting (zero flow) oxygen concentration is ~15.9% O2, significantly higher than the observed ZGRF limits at ~13% O2. This demonstrates how the 1g test is not a conservative test to evaluate microgravity flammability. However, it may be possible to account for the buoyant flow and correct the data to predict a conservative microgravity limit.

Some concurrent ZGRF tests have also been conducted, and the blowoff limits are even lower than opposed limits, but further drop and 1g testing is required to determine if a similar shift in the limits is feasible for concurrent flow. Because concurrent flames grow rapidly, it is difficult to get a 1g flame blowoff before the flame exceeds the apparatus size.

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

The investigation strategy is to perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in International Space Station (ISS)/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2018 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

This year, a summer student performed microgravity forced convection drop testing using cotton fabric sheets, and blowoff limits were obtained and compared with normal gravity buoyant blowoff limits at low oxygen. Limits are lower in microgravity, consistent with previous results. Testing to study blowoff of acrylic slabs has started.

NASA and JAXA are discussing a collaboration that would utilize the BASS-II (Burning and Suppression of Solids) hardware in the ISS Microgravity Science Glovebox for FLARE’s thick polymethylmethacrylate (PMMA) samples in microgravity.

Objective: To develop a methodology to correlate material flammability limits in normal gravity and microgravity, which allows quantitative estimation of material flammability limit in microgravity based on the flammability data obtained on the ground. The project involves an international team including JAXA, NASA, ESA and universities in Japan, USA, and France.

To establish global standards for fire safety in space, we seek to develop a fundamental understanding of how NASA’s material flammability test, NASA-STD-6001.A Test 1, relates to the actual flammability of materials in micro and partial gravity.

Investigation Strategy: Perform extensive research via ground-based experiments, including 1g and parabolic flight tests, and via theoretical formulations. Flight experiments on orbit in ISS/KIBO will be performed to verify the correlation. The flight experiments on orbit are expected in 2017 or later.

By the end of the project, a new fire safety standard test method for screening spacecraft materials will be proposed that addresses the shortcomings of existing standard test method such as NASA STD 6001B.

Relevance/Impact:

Fundamental Science – studying materials flammability in space allows us to accurately control the flow field and thus elucidate the importance of a critical Damkohler number (flow time /reaction time) on flame extinction.

Efficiency - The anticipated improved methodology should reduce time and cost for the spacecraft material screening.

Safety - Terrestrial fire safety; spacecraft fire safety

(Editor's Note: added to Task Book in April 2015 when information received.)