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1. Burning and Suppression of Solids–II (BASS-II) Summary Report

   Sandra L. Olson, Paul V. Ferkul, Subrata Bhattacharjee, Fletcher J. Miller, Carlos Fernandez-Pello, Shmuel Link, James S. T'ien, Indrek Wichman. 2021. technical memorandum.

   Test matrices (Tables 7.1, A.1, A.2) and apparatus description.

   NTRS record

   20210011385 · PDF

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   5ffa911fd9b6356f204646003fb9342e341810dcdfdf5cb15756e7f01ec5f770

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   19 findings

   Abstract

   The Burning and Suppression of Solids (BASS) experiment hardware is a small flow duct that provides containment for small scale burning of solid samples within the Microgravity Science Glovebox (MSG) aboard the International Space Station (ISS). A video camera with a data overlay and a 35-mm still camera record the combustion events. The controls (ignition, fan speed, etc.) are operated by an astronaut while the principal investigator team monitors the experiment from the ground and communicates directly with the astronaut. For the first time on ISS, BASS–II utilized MSG working volume dilution with gaseous N2. We developed a perfectly stirred reactor model to determine the N2 flow time and flow rate to obtain the desired reduced O2 concentration in the working volume for each test. We calibrated the model with the Compound Specific Analyzer-Combustion Products (CSA-CP) O2 readings offset using the Major Constituents Analyzer reading of the ISS ambient atmosphere data for that day. This worked out extremely well for operations, and added a new vital variable, ambient O2 level, to our test matrices. The main variables tested in BASS–II were ambient O2 concentration, ventilation flow velocity, and fuel type, thickness, and geometry. BASS–II also utilized the onboard CSA-CP for O2 and CO readings, and the Carbon Dioxide Monitor for CO2 readings before and after each test. Readings from these sensors allow us to evaluate the completeness of the combustion. The O2 and CO2 readings before and after each test were analyzed and compared very well to stoichiometric ratios for a one-step gas-phase reaction. The CO versus CO2 followed a linear trend for some datasets, but not for all the different geometries of fuel and flow tested. We calculated the heat release rates during each test from the O2 consumption and burn times, using the constant 13.1 kJ of heat released per gram of O2 consumed. The results showed that most of the tests had heat release rates well below 100 W. Lastly, the global equivalence ratio for the tests is estimated to be fuel rich, 1.3 on average using mass loss and O2 consumption data.

2. Combustion of Solids in Microgravity: Results from the BASS-II Experiment

   Ferkul, Paul V., Bhattacharjee, Subrata , Fernandez-Pello, Carlos, Miller, Fletcher , Olson, Sandra L., Takahashi, Fumiaki , T’ien, James S.. 2014. presentation.

   BASS-II overview findings (low-flow dim flames, test counts).

   NTRS record

   20160000593 · PDF

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   9f2c89db9e1954c3c44409364ed6764f7e7466250264c28ff2d425350287546c

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   not quoted, data or context only

   Abstract

   The Burning and Suppression of Solids-II (BASS-II) experiment was performed on the International Space Station. Microgravity combustion tests burned thin and thick flat samples, acrylic slabs, spheres, and cylinders. The samples were mounted inside a small wind tunnel which could impose air flow speeds up to 53 cms. 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, fuel thickness, fuel preheating, and oxygen concentration on flame appearance, growth, spread rate, and extinction were examined in both the opposed and concurrent flow configuration. The flames are quite sensitive to air flow speed in the range 0 to 5 cms. They can be sustained at very low flow speeds of less than 1 cms, when they become dim blue and stable. In this state they are not particularly dangerous from a fire safety perspective, but they can flare up quickly with a sudden increase in air flow speed. Including earlier BASS-I results, well over one hundred tests have been conducted of the various samples in the different geometries, flow speeds, and oxygen concentrations. There are several important implications related to fundamental combustion research as well as spacecraft fire safety. This work was supported by the NASA Space Life and Physical Sciences Research and Applications Division (SLPSRA).

3. Microgravity Flammability of PMMA Rods in Concurrent Flow

   Olson, Sandra L., Ferkul, Paul V.. 2015. conference paper.

   PMMA rod flammability in concurrent flow.

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   20150008961 · PDF

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   8cee8a023d9f0aab214996ebaeefb842080b0c935ba9e01db0096a47379519f7

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   2 findings

   Abstract

   Microgravity experiments burning cast PMMA cylindrical rods in axial flow have been conducted aboard the International Space Station in the Microgravity Science Glovebox (MSG) facility using the Burning and Suppression of Solids (BASS) flow duct, as part of the BASS-II experiment. Twenty-four concurrent-flow tests were performed, focusing on finding flammability limits as a function of oxygen and flow speed. The oxygen was varied by using gaseous nitrogen to vitiate the working volume of the MSG. The speed of the flow parallel to the rod was varied using a fan at the entrance to the duct. Both blowoff and quenching limits were obtained at several oxygen concentrations. Each experiment ignited the rod at the initially hemispherical stagnation tip of the rod, and allowed the flame to develop and heat the rod at a sufficient flow to sustain burning. For blowoff limit tests, the astronaut quickly turned up the flow to obtain extinction. Complementary 5.18-second Zero Gravity Facility drop tests were conducted to compare blowoff limits in short and long duration microgravity. For quenching tests, the flow was incrementally turned down and the flame allowed to stabilize at the new flow condition for at least the solid-phase response time before changing it again. Quenching was observed when the flow became sufficiently weak that the flame could no longer provide adequate heat flux to compensate for the heat losses (conduction into the rod and radiation). A surface energy balance is presented that shows the surface radiative loss exceeds the conductive loss into the rod near the limit. The flammability boundary is shown to represent a critical Damkohler number, expressed in terms of the reaction rate divided by the stretch rate. For the blowoff branch, the boundary exhibits a linear dependence on oxygen concentration and stretch rate, indicating that the temperature at blowoff must be fairly constant. For the quenching branch, the dominance of the exponential nature of the Arrhenius kinetics reaction rate indicates that the temperature is critical.

4. Concurrent Flame Growth, Spread and Extinction over Composite Fabric Samples in Low Speed Purely Forced Flow in Microgravity

   Zhao, Xiaoyang, T'ien, James S., Ferkul, Paul V., Olson, Sandra L.. 2015. conference paper.

   SIBAL fabric concurrent flame growth and quenching.

   NTRS record

   20150008962 · PDF

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   50590fd7e6619203eb75a46f49e83556e6798a53e67869cd52ea89961c692c30

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   2 findings

   Abstract

   As a part of the NASA BASS and BASS-II experimental projects aboard the International Space Station, flame growth, spread and extinction over a composite cotton-fiberglass fabric blend (referred to as the SIBAL fabric) were studied in low-speed concurrent forced flows. The tests were conducted in a small flow duct within the Microgravity Science Glovebox. The fuel samples measured 1.2 and 2.2 cm wide and 10 cm long. Ambient oxygen was varied from 21% down to 16% and flow speed from 40 cm/s down to 1 cm/s. A small flame resulted at low flow, enabling us to observe the entire history of flame development including ignition, flame growth, steady spread (in some cases) and decay at the end of the sample. In addition, by decreasing flow velocity during some of the tests, low-speed flame quenching extinction limits were found as a function of oxygen percentage. The quenching speeds were found to be between 1 and 5 cm/s with higher speed in lower oxygen atmosphere. The shape of the quenching boundary supports the prediction by earlier theoretical models. These long duration microgravity experiments provide a rare opportunity for solid fuel combustion since microgravity time in ground-based facilities is generally not sufficient. This is the first time that a low-speed quenching boundary in concurrent spread is determined in a clean and unambiguous manner.

5. Thickness and Fuel Preheating Effects on Material Flammability in Microgravity from the BASS Experiment

   Ferkul, Paul V., Olson, Sandra L., Takahashi, Fumiaki, Endo, Makoto, Johnson, Michael C., T'ien, James S.. 2013. presentation.

   Thickness and preheating effects (BASS).

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   20140011099 · PDF

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   fd5e89467bddd426e40081311f0b36541aac6a29236b2d3fc3758a901bc8c072

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   3 findings

   Abstract

   The Burning and Suppression of Solids (BASS) experiment was performed on the International Space Station. Microgravity combustion tests burning thin and thick flat samples, acrylic spheres, and candles were conducted. The samples were mounted inside a small wind tunnel which could impose air flow speeds up to 40 cms. 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, fuel thickness, fuel preheating, and nitrogen dilution on flame appearance, flame growth, and spread rates were determined in both the opposed and concurrent flow configuration. In some cases, a jet of nitrogen was introduced to attempt to extinguish the flame. Microgravity flames were found to be especially sensitive to air flow speed in the range 0 to 5 cms. The gas phase response is much faster compared to the solid and so as the flow speed is changed, the flame responds with almost no delay. At the lowest speeds examined (less than 1 cms) all the flames tended to become dim blue and very stable. However, heat loss at these very low convective rates is small so the flames can burn for a long time. At moderate flow speeds (between about 1 and 5 cms) the flame continually heats the solid fuel resulting in an increasing fuel temperature, higher rate of fuel vaporization, and a stronger, more luminous flame as time progresses. Only the smallest flames burning acrylic slabs appeared to be adversely influenced by solid conductive heat loss, but even these burned for over 5 minutes before self-extinguishing. This has implications for spacecraft fire safety since a tiny flame might be undetected for a long time. While the small flame is not particularly hazardous if it remains small, the danger is that it might flare up if the air convection is suddenly increased or if the flame spreads into another fuel source.

6. Effects of Confinement on Flame Spread in Microgravity

   Yanjun Li, Ya-Ting T Liao, Paul V Ferkul, Michael C Johnston, Charles Bunnell. conference paper.

   Saffire vs BASS confinement comparison.

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   20205004657 · PDF

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   3096713e1da5122b0d06235a0194ecc2ccaa0fac0df40d11095241401bfb916a

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   2 findings

   Abstract

   Solid fuel combustion experiments aboard the ISS examine the effects of confinement on a concurrent, purely-forced-flow flame spread in microgravity environment. The results for a thin, cotton-fiberglass-blended textile fabric fuel are presented. Flat baffles of differing materials are used to alter the radiative boundary conditions with transparent polycarbonate, black anodized aluminum (reflectance ~ 0), and highly polished aluminum (reflectance ~ 1). The baffles are parallel to the fuel sheet and placed symmetrically on each side. The inter-baffle distance is varied to change the boundary conditions for the flow. In all tests, samples are ignited at the upstream leading edge and allowed to burn to completion. Results show that the flame reaches a steady length and spread rate at low flow speeds (< 15 cm/s) for all tested inter-baffle distances. As the distance decreases, the flame length and spread rate first increase then decrease showing an optimal inter-baffle distance. For all baffle types, the flame either fails to ignite or extinguishes before reaching the end of the sample when the inter-baffle distance is too small (~ 1 cm). This is attributed to the reduction of oxygen supply to the flame zone and heat loss to the baffles. The results also show at the same inter-baffle distance, flame length and spread rate are highest for polished aluminum baffles, and lowest for transparent polycarbonate baffles. The differences are most prominent at intermediate tested baffle distances. While the radiative heat feedback from the baffles is expected to increase when the baffle distance decreases, the combustion is limited by the reduced oxygen supply. Near this limit, flame lengths and spread rates are similar for all baffle types.

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

   Oslon, Sandra. L., Ferkul, Paul. 2012. conference paper.

   Microgravity vs Martian gravity vs NASA-STD-6001 Test 1.

   NTRS record

   20130010991 · PDF

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   2b0cabdfe7942f56bad38967e9c870dd1c73f3cb52f614a1873a93f8cc51436e

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   2 findings

   Abstract

   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.

8. Lunar Combustion Investigation: Flammability Results from a Rotating Sounding Rocket

   Paul V Ferkul, Michael C Johnston, Nathan Kralik, Ya-Ting Liao. presentation.

   Lunar-gravity flammability from a rotating sounding rocket.

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   20250010653 · PDF

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   bb0aadd2f9543483467b86796e6aa19f4e13c3f8169eec96134015f95ed61d79

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   2 findings

   Abstract

   The Lunar Combustion Investigation (LUCI) demonstrates the feasibility of conducting material flammability experiments in partial-g. A spinning Blue Origin New Shepard sounding rocket yields Lunar gravity by using centrifugal acceleration. These are the first-ever, extended-duration (greater than 25 seconds) combustion tests performed in simulated Lunar gravity. A steady vehicle rotation of 11 RPM is established, with an effective radius of rotation of 1.22 m at the experiment location. Two samples are burned simultaneously in air at normal pressure. The first sample is a cotton-fiberglass composite fabric sheet and the second a 4-mm diameter rod of acrylic plastic (polymethyl methacrylate). Flame images from two orthogonal cameras are used to determine flame spread and growth rates, and the burn lasts for over two and a half minutes. The oxygen concentration in the chamber is measured. As the burns progress, the oxygen concentration drops, enabling a limiting value for extinction to be defined. The effect of Coriolis force is discussed. Results from this experiment are compared to related 1-g work, drop tower tests, aircraft experiments, and modeling. The results are applicable to NASA’s exploration efforts in that they guide the selection of fire-safe materials and environments and ensure safety of future spacecraft and Lunar habitats. The data also provides fundamental understanding of fires. Finally, the experiment is a steppingstone to the ultimate goal of performing burn tests on the Lunar surface in the Flammability of Materials on the Moon (FM2) experiment which is planned to launch in late 2026.

9. Results of a 3-day Pilot Study to Validate Planetary Prebreathe Protocols Using a 56.5 kPa 34% O2, 66% N2 Saturation Cabin Atmosphere

   Alejandro Garbino, E Lichar Dillon, Patrick Estep, Monica Hew, Karina Marshall-Bowman, Jason Norcross, Kadambari Suri, Andrew F J Abercromby. presentation.

   Source for the 56.5 kPa, 34 % O2 exploration cabin atmosphere scenario.

   NTRS record

   20220009546

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   1 finding

   Abstract

   INTRODUCTION: Apollo missions used 100% O2 cabin atmospheres which effectively eliminated the risk of decompression sickness (DCS) during extravehicular activities (EVAs, ‘spacewalks’); however, this atmosphere presented a flammability risk that is no longer acceptable to NASA. Denitrogenation prebreathe protocols used to mitigate DCS risk for Space Shuttle and International Space Station EVAs are validated for the microgravity environment, but the significantly increased risk of DCS during equivalent ambulatory surface EVAs make these protocols inapplicable to planetary/Lunar missions. An “exploration atmosphere” of 56.5 kPa (8.2 psia), 34% O2, 66% N2 has been recommended by NASA for future Moon and Mars missions as a compromise that balances subsequent pre-EVA prebreathe duration, hypoxia, and flammability risk, assuming a 29.6 kPa (4.3 psi) spacesuit. Prebreathe validation studies was initiated utilizing a three-story 6m diameter hypobaric chamber at NASA’s Johnson Space Center. Here, we report the results of a 3-day human-in-the-loop system checkout. METHODS: Six volunteers acclimated to the 56.6kPa/34% O2 66% N2 environment for 48hrs prior to conducting a 20-minute prebreathe and a 6-hour simulated EVA at 34kPa/85% O2 / 15% N2. The EVA simulation was designed to include tasks that are physically and ergonomically representative of future planetary EVAs. Decompression stress was evaluated by serial doppler and echocardiographs, as well as by clinical features of DCS signs/symptoms. RESULTS AND DISCUSSION: Preliminary data analysis noted venous gas emboli (VGE) in 3 of 6 subjects, with peak Grade II VGE by Doppler and peak E-B score of 5 by cardiac ultrasonography. No volunteers were diagnosed with DCS during this initial test. No acute hypoxic symptoms were noted. Musculoskeletal and gastrointestinal complaints were noted, likely associated with the exercise load and the food system. Validation of exploration prebreathe protocols has since been initiated with an 11-day saturation test using the same facility and protocol.

10. Nasa Exploration Atmosphere Tests 3 & 4: Development and Validation of Planetary Extravehicular Activity Prebreathe Protocols for Alternate Atmospheres and Suit Pressures

    A Garbino, M Y Hew-Yang, P Estep, B Siders, K Marshall-Goebel. abstract.

    Exploration Atmosphere Tests 3 and 4: the alternate 66.2 kPa, 28.5 % O2 cabin atmosphere.

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    20240013238 · PDF

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    727b246ec75eebcbac10b3da199bf299071c41a216f5b5324d791e1e08fbfa0e

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    2 findings

    Abstract

    INTRODUCTION: Space suits operate at low pressures to optimize astronauts’ performance. The drop in pressure from the habitat environment to the suit carries a risk of decompression sickness (DCS), which is mitigated by a 95% O2 prebreathe protocol. Prebreathe protocols for the lunar surface have a significantly higher risk compared to International Space Station microgravity Extravehicular Activities (EVA). In previous studies, we validated a prebreathe protocol from a 56.5 kPa 34% O2 cabin to a 29.6 kPa EVA pressure; however, the enriched oxygen cabin environment poses a flammability risk that requires significant changes to material design and selections. Here, we report outcomes for prebreathe protocols from a sub-30% O2 cabin and associated changes necessary to control DCS risk critical to upcoming lunar missions. METHODS: Fourteen volunteers completed 11-day hypobaric chamber studies with an “alternate exploration atmosphere” of 66.2kPa, 28.5% O2. Subjects acclimated for 48 hrs and then participated in five 6-hour simulated EVAs at 29.6 or 35.6kPa, 95% O2. Prior to EVA, subjects underwent a 20, 90, or 150-minute prebreathe. The EVA simulation was designed to be representative of future planetary EVAs, proportionate to the subject’s VO2max. Decompression stress was monitored by real-time doppler and echocardiograph alternating every 15 min, as well as clinical monitoring for DCS signs/symptoms. Venous gas emboli (VGE) and DCS outcomes were verified against NASA-STD-3001 acceptance criteria. RESULTS AND DISCUSSION: Venous gas emboli (VGE) were identified during all EVAs. A neurological DCS case was identified in the 90-min/29.6kPa prebreathe, terminating further testing of this protocol. No DCS cases were identified in the 150 min/29.6kPa protocol. The 20 min/36.5kPa protocol was rejected due to a Type II DCS case. All DCS symptoms resolved with treatment, with no sequelae post initial treatment of DCS. These various test points highlighted to the significant benefit of elevated suit pressure to shorten prebreathe protocols, but also the difficulty in assessing and managing DCS during sustained EVA operations in remote planetary surfaces.

11. Flammability of Materials on the Moon

    Jennifer Zayac, Michael Johnston, Gary Ruff, Paul Ferkul. poster.

    FM2: planned lunar-surface burns of SIBAL fabric and PMMA rods, and what they will measure.

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    20240008623 · PDF

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    b96e5a0e72466792c3a135c232084ec9cc729f33b4906ac6b3fc32ff051bcbac

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    Abstract

    Some materials have recently been found to exhibit increased flammability in Lunar gravity. The reduced buoyancy driven flow on the Moon may present a goldilocks region of decreased convective cooling, while still supplying adequate oxidizer to the flame zone. Combined with the desired elevated oxygen habitat of exploration architectures and the difficulty of rescue, the combination could present increased risk to crew. Flammability of Materials on the Moon will be delivered to the Lunar surface on an HLS lander, and will burn four samples; SIBAL fabric will be exposed to normal air while the PMMA rods will be exposed to the normoxic Space Exploration Atmospheres (SEA) with elevated oxygen in a small atmospheric chamber. Each fuel will have two tests each, one burning upward and one burning downward. The results of flame size, spread rate, atmosphere changes, and extinction oxygen concentration will then be analyzed and used to help quantify the risk and mitigation for future exploration missions.

12. Flammability of Materials on the Moon

    Jennifer Zayac, Michael Johnston, Gary Ruff, Paul Ferkul. poster.

    FM2: planned atmospheres, samples, and SIBAL burning downward in lunar gravity.

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    20240015307 · PDF

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    eb86f426ee83c3edb3eda8053f33382248394f5bcb6aa6be171b59ddab5c3e47

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    4 findings

    Abstract

    Lunar gravity has been found to increase the limits of flammability for some materials compared to Earth gravity, presenting a goldilocks zone of reduced convective heat loss, while generating enough buoyant flow to replenish fresh oxygen into the flame zone. Combined with the elevated oxygen concentrations of planned Space Exploration Atmospheres (Sea), a long duration fire experiment in Lunar gravity is important to help understand and mitigate the increased risk. Flammability of Materials on the Moon (FM2) is a robotic, self-contained, combustion chamber which will be sent to the surface of the Moon on a Commercial Lunar Payload Services (CLPS) lander mission CP-21. The environmental control system can replicate and conduct fire experiments automatically in the expected atmospheres, specifically 21% oxygen at 14.7 psia, and 34% oxygen at 8.2 psia, which are of immediate interest to the Human Lander System (HLS) and Lunar Rover. The laboratory prototype became operational this summer. There are four samples currently planned; two SIBAL fabrics (cotton/fiberglass blend) which will be burned in air and two acrylic rods which will be burned in Normoxic Space Exploration Atmospheres (SEA). One of each fuel will be burned upward and downward. SIBAL fabric has been found to only burn downward in air in lunar gravity (via Lunar gravity centrifuge and parabolic flight) where on Earth’s gravity it extinguishes immediately after ignition.

13. NASA Exploration Atmosphere Test 6: Back to Back EVAs

    Alejandro Garbino, Monica Hew-Yang, Patrick Estep, Brett Siders, Stijn Thoolen, Karina Marshall-Goebel. presentation.

    Exploration Atmosphere Test 6: 66.2 kPa, 28.5 % O2 named the proposed Exploration Atmosphere.

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    20260003261 · PDF

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    9f9a88f8a91efdd80c456236a0c7739541812b6d16ec3b4dd1e12f8bec698d45

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    1 finding

    Abstract

    INTRODUCTION: Space suits operate at low pressures to optimize astronauts’ performance. The drop in pressure from the habitat environment to the suit carries a risk of decompression sickness (DCS), which is mitigated by a 95% O2 prebreathe protocol. Prebreathe protocols for the lunar surface have a significantly higher risk compared to International Space Station microgravity Extravehicular Activities (EVA). In previous studies, we validated a prebreathe protocols for single (independent) EVA exposures. However, Artemis mission plans include daily (‘back to back’) EVAs. NASA has minimal data exploring the DCS risk impacts of ~16hrs ‘surface intervals’, ie, breaks between EVAs. METHODS: Sixteen volunteers completed 7-day hypobaric chamber studies simulating daily EVAs. Subjects acclimated for 48 hrs at the proposed Exploration Atmosphere (66.2kPa, 28.5% O2) and then participated in five 6-hour simulated EVAs at 29.6 kPa, 95% O2. Prior to EVA, subjects underwent a 120 or 150-minute prebreathe. The EVA simulation was designed to be representative of future planetary EVAs, proportionate to the subject’s VO2max. Decompression stress was monitored by real-time doppler and echocardiograph alternating every 15 min, as well as clinical monitoring for DCS signs/symptoms. Venous gas emboli (VGE) and DCS outcomes were verified against NASA-STD-3001 acceptance criteria. RESULTS AND DISCUSSION: Two neurological DCS cases occurred in the 120-min/29.6kPa prebreathe, terminating further testing of this protocol. One Type I DCS case was identified in the 150 min/29.6kPa protocol. All DCS symptoms resolved with treatment, with no residual sequelae post HBOT treatments of DCS. Venous gas emboli (VGE) were identified during all EVAs. Within the statistical power of these limited exposures, there was no apparent increase or decrease in VGE as a result of back-to-back EVAs (within +/- 1 VGE grade). This test highlighted the importance of characterizing DCS risk factors, and the difficulty in assessing and managing DCS during sustained EVA operations in remote planetary surfaces.

14. Results of Large-Scale Spacecraft Flammability Tests

    Ferkul, Paul , Olson, Sandra , Urban, David L., Ruff, Gary A., Easton, John , T'ien, James S., Liao, Ta-Ting T., Fernandez-Pello, A. Carlos, Torero, Jose L., Eigenbrand, Christian, Legros, Guillaume, Smirnov, Nickolay, Fujita, Osamu, Rouvreau, Sebatien, Toth, Balazs, Jomaas, Grunde. 2017. presentation.

    Saffire I-III: large-scale flame spread aboard Cygnus.

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    20170008805 · PDF

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    e38ec36f54817aa97e0c01a05f12b212521d6320ce3f4cb7a38bb7c837cfea8d

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    5 findings

    Abstract

    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.

15. Fire Safety Implications of Preliminary Results from Saffire IV and V Experiments on Large Scale Spacecraft Fires

    David L. Urban, Gary A. Ruff, Paul Ferkul, John Easton, Jay Owens, Sandra Olson, Marit Meyer, Claire Fortenberry, John Brooker, John Graf, Michael Casteel, Balazs Toth, Florian Meyer, Christian Eigenbrod, James S. T’ien, Ya-Ting T. Liao, A. Carlos Fernandez-Pello, Guillaume Legros, Nickolay Smirnov, Osamu Fujita, Grunde Jomaas. presentation.

    Saffire IV and V: large-scale fire safety implications.

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    20210017780 · PDF

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    1f75e833ec50e42a253424a6ffb44b5699a1e046a5e34b7060e026f63a7d2077

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    3 findings

    Abstract

    The spread and growth of flames over large solid fuel samples and their effect on the pressurized spacecraft were studied inside the 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.

16. Preliminary Results from the Saffire VI Experiment

    David L Urban, Gary A Ruff, Paul Ferkul, John Easton, Michael Johnston, Jay Owens, Sandra Olson, Claire Fortenberry, John Graf, Oageng George, Balazs Toth, Florian Meyer, Christian Eigenbrod, James S T'ien, Ya-Ting T. Liao, A Carlos Fernandez-Pello, Guillaume Legros, Augustin Guibaud, Nickolay Smirnov, Osamu Fujita, Ulises Rojas Alva, Grunde Jomaas. conference paper.

    Saffire VI preliminary results (ICES 2024 paper).

    NTRS record

    20240002981 · PDF

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    may include copyright material

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    7f875da1d6abeeeeac64aeba67d3f160074cf98430e714fe7606b34b37e0aa59

    Quoted here

    5 findings

    Abstract

    Preliminary results are presented for one test of the last flight of the Spacecraft Fire Experiment (Saffire VI) which was conducted on an orbiting Cygnus spacecraft. These experiments directly address the risks associated with our understanding of spacecraft fire behavior at practical length scales and geometries. The lack of this experimental data has forced spacecraft designers to base their designs and safety precautions on 1-g understanding of flame spread, flame self-extinguishment, fire detection, and suppression. The Saffire experiment was developed by an international team of investigators with the goal of addressing open issues in spacecraft fire safety. NASA’s Spacecraft Fire Safety Demonstration Project was formulated with the goal of conducting a series of large-scale experiments in spacecraft environments that represent practical spacecraft fires. These tests spanned 1.5 to 3.2 kW with free air volumes of 17 to 19 cubic meters. The final flight in the series of six experiments examined concurrent spread over large samples (all 41 cm wide) including a thin sheet of flammable fuel (cotton/fiberglass 50 cm long); 2-sided spread over 1 cm thick polymethyl methacrylate (PMMA) (18 cm long); 1-sided spread over 0.5 cm thick (18 cm long); and Nomex fabric (7 cm long). Results are presented for the PMMA samples, the SIBAL sample, and the thin cotton samples from Saffire IV and V. The flame heat release is determined and compared to the overall temperature rise in the spacecraft and the change in the concentration of carbon dioxide and carbon monoxide in the spacecraft. Overall, the temperature and pressure rise in the spacecraft were found to be less significant than the increase in carbon dioxide and carbon monoxide.

17. Detailed Results from the Flame Extinguishment Experiment (FLEX) March 2009 to December 2011

    Dietrich, Daniel L., Ferkul, Paul V., Bryg, Victoria M., Nayagam, M. Vedha, Hicks, Michael C., Williams, Forman A., Dryer, Frederick L., Shaw, Benjamin D., Choi, Mun Y., Avedisian, C. Thomas. 2015. technical publication.

    FLEX droplet combustion and extinguishment results (mechanistic evidence only).

    NTRS record

    20150023456 · PDF

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    public use permitted

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    b4f6ca983e2792c33a0b92220a791a818f426bb635b94f7fd33dc8c9c471e79d

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    3 findings

    Abstract

    The Flame Extinguishment Experiment (FLEX) program is a continuing set of experiments on droplet combustion, performed employing the Multi-User Droplet Combustion Apparatus (MDCA), inside the chamber of the Combustion Integrated Rack (CIR), which is located in the Destiny module of the International Space Station (ISS). This report describes the experimental hardware, the diagnostic equipment, the experimental procedures, and the methods of data analysis for FLEX. It also presents the results of the first 284 tests performed. The intent is not to interpret the experimental results but rather to make them available to the entire scientific community for possible future interpretations.

18. Solid Fuel Ignition and Extinction (SoFIE) Project on ISS

    Ferkul, Paul, Brown, Lauren, Mroczka, Christopher, Bhattacharjee, Subrata, Fernandez-Pello, Carlos, Miller, Fletcher, Olson, Sandra, T'ien, James, Wichman, Indrek. 2019. presentation.

    SoFIE: material flammability under exploration-like oxygen and pressure.

    NTRS record

    20200000361 · PDF

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    public use permitted

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    dc42805d92fb9073cda48d76b9aa3fdf9fd26b7780d537a9e8e1b73ac433e7b0

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    3 findings

    Abstract

    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.

19. Advanced Combustion via Microgravity Experiments (ACME) on the International Space Station (ISS)

    Dennis Stocker. poster.

    ACME gaseous flames on the ISS (mechanistic evidence only).

    NTRS record

    20210015913 · PDF

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    gov public use permitted

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    8cebedd4be120fe2369ad4d971c85f08a148d3af056d88c7d7914bde4089a090

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    2 findings

    Abstract

    Experimental studies of laminar, non-premixed flames of gaseous fuels are underway on the International Space Station (ISS) as part of NASA’s Advanced Combustion via Microgravity Experiments(ACME) project. The research is primarily focused on improving practical terrestrial combustion through fundamental microgravity research, where a secondary objective is spacecraft fire safety. Example goals are to improve understanding of flame stability and extinction limits, soot control and reduction, oxygen-enriched combustion which could enable practical carbon sequestration, combustion at fuel lean conditions where both optimum performance and low emissions can be achieved, the use of electric fields for combustion control, cool flame chemical kinetics, and materials flammability. The microgravity environment avoids buoyancy-induced flicker and enables the creation of spherical flames, allowing numerical models to focus computational power on transport phenomena and chemical kinetics. Compared to normal gravity, microgravity also provides longer residence times and larger length scales, yielding a broad range of flame conditions which are beneficial for simplified analysis, e.g., of limit behavior where chemical kinetics are important. Using modular hardware, research for six independent investigations is being carried out within the station’s Combustion Integrated Rack (CIR). While the ISS crew members set up the experimental hardware, the tests are remotely commanded with investigator input from the NASA Glenn Research Center. Over a thousand flames have been ignited since ACME operations began in Sept. 2017 and selected results from the first five experiments are summarized.