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.
Experiments: BASS, BASS-II, SAME, SPICE
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).
Test conditions.
Extracted from the paper by AI · “Verified” means a person checked it
| Fuel | O₂ | Pressure | Airflow | Sensors | Source | AI conf. | Status |
|---|---|---|---|---|---|---|---|
| PMMA (polymethyl methacrylate) 1-cm and 2-cm wide sheets |
— | — | 0 to 55 cm/s | Video, Digital still camera | p. 11 | 95% | Pending |
| PMMA (polymethyl methacrylate) 1-cm and 2-cm wide sheets |
— | — | 0 to 55 cm/s | Video, Digital still camera | p. 16 | 95% | Pending |
| PMMA (polymethyl methacrylate) Rods (0.25", 0.375", 0.5") |
16% to 21% | — | 0.4 cm/sec to 4 cm/sec | Video, Digital still camera | p. 14 | 95% | Pending |
| PMMA (polymethyl methacrylate) Rods (1/4 inch) |
13.6% | — | Concurrent (stagnation point) flow | Video, Digital still camera | p. 18 | 95% | Pending |
Findings.
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01
In microgravity, PMMA rods exhibited steady flame spreading at 13.6% oxygen, whereas the 1g blowoff limit for the same geometry was 16% oxygen, indicating a negative Oxygen Margin of Safety of 2.4%.
Prevention · p. 18 · AI confidence 95% · Reported · Pending
“The 1g blowoff for the ¼” rod is at 16% oxygen, whereas we obtained steady spreading at 13.6% oxygen in BASS - II. Thus the material has a negative Oxygen Margin of Safety of 2.4% O 2”
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02
Flame spread rates in microgravity are lower than those in normal gravity (1g) for PMMA rods.
Other · p. 15 · AI confidence 95% · Reported · Pending
“1g tests have higher flame spread rates than μg .”
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03
In microgravity, flame spread rate increases as oxygen concentration increases when averaged over all tested flow velocities.
Other · p. 15 · AI confidence 95% · Reported · Pending
“In μg , there is an upward trend in flame spread rate as the oxygen concentration is increased when averaging over all tested flow velocities.”
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04
Radiative quenching occurs in microgravity when flow velocity goes below 2 cm/s for thin PMMA sheets.
Suppression · p. 12 · AI confidence 90% · Reported · Pending
“Sequence of top views showing radiative quenching when flow velocity goes below 2 cm/s.”
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05
Blow off extinction occurs in microgravity as flow velocity crosses 40 cm/s for thin PMMA sheets.
Suppression · p. 12 · AI confidence 90% · Reported · Pending
“Flame nearing blow off extinction as the flow velocity crosses 40 cm/s.”
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06
The minimum in the flammability boundary for PMMA in microgravity occurs at low speeds, on the order of diffusive flows.
Other · p. 18 · AI confidence 95% · Reported · Pending
“The minimum in the flammability boundary is at low speed, on the order of diffusive flows.”