Spacecraft Fire Safety Research at NASA Glenn Research Center
Meyer, Marit
Experiments: ACME, CFI, FLEX, SAFFIRE I, SAME
Appropriate design of fire detection systems requires knowledge of both the expected fire signature and the background aerosol levels. Terrestrial fire detection systems have been developed based on extensive study of terrestrial fires. Unfortunately there is no corresponding data set for spacecraft fires and consequently the fire detectors in current spacecraft were developed based upon terrestrial designs. In low gravity, buoyant flow is negligible which causes particles to concentrate at the smoke source, increasing their residence time, and increasing the transport time to smoke detectors. Microgravity fires have significantly different structure than those in 1-g which can change the formation history of the smoke particles. Finally the materials used in spacecraft are different from typical terrestrial environments where smoke properties have been evaluated. It is critically important to detect a fire in its early phase before a flame is established, given the fixed volume of air on any spacecraft. Consequently, the primary target for spacecraft fire detection is pyrolysis products rather than soot. Experimental investigations have been performed at three different NASA facilities which characterize smoke aerosols from overheating common spacecraft materials. The earliest effort consists of aerosol measurements in low gravity, called the Smoke Aerosol Measurement Experiment (SAME), and subsequent ground-based testing of SAME smoke in 55-gallon drums with an aerosol reference instrument. Another set of experiments were performed at NASAs Johnson Space Center White Sands Test Facility (WSTF), with additional fuels and an alternate smoke production method. Measurements of these smoke products include mass and number concentration, and a thermal precipitator was designed for this investigation to capture particles for microscopic analysis. The final experiments presented are from NASAs Gases and Aerosols from Smoldering Polymers (GASP) Laboratory, with selected results focusing on realistic fuel preparations and heating profiles with regards to early detection of smoke. SAFFIRE is the upcoming large-scale fire experiment which will be executed in a Cygnus vehicle after it undocks from the ISS.
Test conditions.
Extracted from the paper by AI · “Verified” means a person checked it
| Fuel | O₂ | Pressure | Airflow | Sensors | Source | AI conf. | Status |
|---|---|---|---|---|---|---|---|
| Teflon | — | — | — | ISS smoke detector | p. 30 | 95% | Pending |
| Pyrell foam |
— | — | — | small, cheap instruments, particle collector | p. 18 | 85% | Pending |
| Kapton film |
— | — | — | small, cheap instruments, particle collector | p. 18 | 85% | Pending |
| Lamp wick (cellulose) wick |
— | — | — | small, cheap instruments, particle collector | p. 18 | 85% | Pending |
| Silicone rubber | — | — | — | small, cheap instruments, particle collector | p. 18 | 85% | Pending |
| Nomex woven textile |
— | — | — | Compact Optical Dust Sensor (COTS) | p. 28 | 85% | Pending |
| Tobacco | — | — | — | Compact Optical Dust Sensor (COTS) | p. 29 | 85% | Pending |
| FR-4 (printed circuit board) bare PCB |
— | — | — | ISS smoke detector | p. 30 | 85% | Pending |
Findings.
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01
Current fire detection systems in space were developed without spacecraft fire data.
Detection · p. 7 · AI confidence 95% · Reported · Pending
“Current fire detection systems in space were developed without spacecraft fire data”
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02
In microgravity, smoke does not rise due to the absence of gravity.
Other · p. 9 · AI confidence 95% · Reported · Pending
“With the absence of gravity smoke does not rise”
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03
The most likely source of a fire in spacecraft is overheating electronic equipment.
Prevention · p. 9 · AI confidence 95% · Reported · Pending
“Most likely source of a fire is overheating electronic equipment”
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04
The goal of spacecraft fire safety research is to detect smoke before a flame develops.
Detection · p. 9 · AI confidence 95% · Reported · Pending
“Goal: detect smoke before a flame develops”
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05
Research focuses on smoke from pyrolysis rather than flames (combustion).
Other · p. 9 · AI confidence 95% · Reported · Pending
“Research smoke from pyrolysis , not flames (combustion)”
-
06
The ISS Destiny Laboratory smoke detection model indicates that 'dirty air' is pulled through HEPA filters.
Detection · p. 13 · AI confidence 90% · Reported · Pending
“‘Dirty air’ pulled through HEPA filters here”
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07
The SAME experiment was designed to generate pyrolysis smoke in low gravity using common spacecraft materials.
Detection · p. 15 · AI confidence 95% · Reported · Pending
“Experiment designed to generate pyrolysis smoke in low gravity • Common spacecraft materials”
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08
The Smoke-in-drums ground experiment aims to measure SAME smoke with returned ISS instruments and a high fidelity reference instrument.
Detection · p. 22 · AI confidence 95% · Reported · Pending
“Make SAME smoke in a lab • Measure with returned ISS instruments — AND — a high fidelity reference instrument”
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09
Diluting smoke in a large drum stops the coagulation (aging) of smoke particles during measurements.
Other · p. 22 · AI confidence 95% · Reported · Pending
“Dilute the smoke by sending it into a large 55 gallon drum • Stops coagulation (aging) of the smoke particles during measurements”
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10
The ISS smoke detector alarm threshold is 2 mg/m^3.
Detection · p. 30 · AI confidence 95% · Reported · Pending
“ISS smoke detector alarm threshold = 2 mg/m 3”
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11
Teflon smoke generated in GASP experiments would never trigger the ISS smoke detector alarm.
Detection · p. 30 · AI confidence 95% · Reported · Pending
“Teflon smoke generated would never trigger alarm”
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12
Detection times for GASP experiments ranged from 1 minute to 6 minutes, which was considered too slow.
Detection · p. 30 · AI confidence 95% · Reported · Pending
“Detection times from 1 minute to 6 minutes (Teflon is infinity) Too slow!”
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13
Thermal decomposition of Kapton results in liquid aromatic products.
Other · p. 35 · AI confidence 95% · Reported · Pending
“Thermal decomposition of Kapton results in liquid aromatic products”
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14
Kapton smoke particles form chain-like agglomerates with 100 to 350 nm primaries.
Other · p. 35 · AI confidence 95% · Reported · Pending
“Chain - like agglomerates, 100 to 350 nm primaries”
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15
FLEX results revealed a unique two-stage burning event involving cool flames.
Other · p. 43 · AI confidence 95% · Reported · Pending
“Flame Extinguishment Experiment (FLEX) results revealed a unique two - stage burning event: Cool Flames”
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16
Spacecraft safety procedures based only on hot flames may be inadequate for assuring safety under all conditions.
Prevention · p. 43 · AI confidence 95% · Reported · Pending
“Spacecraft safety procedures based only on considerations of hot flames may be inadequate for assuring safety under all conditions.”
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17
SAFFIRE Tests 1 through 3 have a combustion emphasis, while Tests 4 through 6 have a smoke detection emphasis.
Detection · p. 41 · AI confidence 95% · Reported · Pending
“Tests 1 through 3 – combustion emphasis • Tests 4 through 6 – smoke detection emphasis”