Smoke Detection in Low Gravity Results from the Smoke Aerosol Measurement Experiments (SAME) Conducted on the International Space Station

Transcription

1 Smoke Detection in Low Gravity Results from the Smoke Aerosol Measurement Experiments (SAME) Conducted on the International Space Station March 4, th AIAA Aerospace Sciences Meeting, January

2 Smoke Detection in Low Gravity Results from the Smoke Aerosol Measurement Experiments (SAME) Conducted on the International Space Station NASA Glenn Research Center David Urban, Gary Ruff, Marit Meyer, Paul Greenberg, David Fischer University of Maryland George Mulholland National Center for Space Exploration Research Zeng-guang Yuan, Victoria Bryg National Institute of Standards and Technology Thomas Cleary, Jiann Yang 2

3 Smoke Detection Background: Destiny Smoke Detection Simulation-25% Soot effect of gravity Low-gravity Normal-gravity 3

4 Background: Spacecraft Fire Detection STS Detector: sensitive < 1 micron Dual-chamber ionization with inertial separator which rejects particles larger than 1-2 microns Developed in the late 70 s when Ionization detectors were prevalent ISS detector: sensitive > 0.5 micron 2-pass IR laser-diode forward-scattering detector (30 degrees) minimum reported sensitivity is 0.3 μm Developed in the 90 s and took advantage of the availability of stable diode light sources 4

5 Smoke Detector Obscuration and Scatter - Current Crew Sleep Spikes represent dust passing through SD Crew Work Node 3 Detectors USL Detectors

6 ISS Background Conditions Inter-module ventilation filter screen Smoke detector with dust deposits 50 th AIAA Aerospace Sciences Meeting, Nashville, TN 6

7 Objective Determine whether typical conditions on spacecraft will change the particle size distribution of target smokes Soot particle size increases seen in low-gravity (work of Megaridis and Dobbins; Ku and Greenberg; and Faeth et al.) Increased residence time in high concentration zone Potential for trapped smoke in avionics enclosures 7

8 Approach Preflaming pyrolysis smoke Vary pyrolysis rate, air flow rate Measure statistics of particle size distribution and capture samples for TEM analysis 8

9 f N Log-Normal Distribution ( D) (2 ) 1/ Nt 2 Dln g exp ln D ln D 2ln 2 g g 2 Number is dominated by the smaller particles Mass is dominated by the larger particles (tail) Log-normal distribution σ g = 1.6, D g = 1 9

10 SAME Experimental Diagnostic Measurements All measure moments of the particle size distribution i Mi D fn ( D) dd Arithmetic Mean Diameter (M 1 / M 0 ) Diameter of Average Mass (M 3 / M 0 ) 1/3 Geometric Mean can be calculated with the assumption of a log-normal distribution Zeroth Moment: TSI PTrak First Moment: First Alert Smoke Detector Third Moment: TSI Dust Trak 10

11 SAME Sample Carousel Sample Materials: Silicone Teflon Kapton LampWick Pyrell DBP 11

12 SAME in MSG (mockup) Data Acquisition and Control Unit Aging Chamber Fluids Control Unit Sample Diluter Commercial Diagnostics Hose Bundle Experiment Support Plate Sample Carousel Thermal Precipitator P-Trak Enclosure 12

13 SAME Hardware on orbit 13

14 SAME Particle Capture Stereolithography manifold Hot-wire Leads Handle for quick installation and removal X-valve solenoid bank Electrical Connection Vacuum Connection Cover 14

15 Thermal Precipitator Overview image showing deposition boundary 15

16 TEM Results Teflon (Run 56) Lampwick (Run 54) Pyrell (Run 63) Kapton (Run 62) Length 2 μm scale 16

17 TEM Results - Pyrell Aging Pre aging Post aging 2 microns 2 microns High Temperature Pyrell: 480 second aging run (Run 84) 17

18 TEM Results Pyrell- effect of flow 5 microns 5 microns 8 cm/s air flow No air flow Pyrell with and without flow 18

19 SAME Raw Data 7 6 Silicone Run 24 GMT 267 ISSDetectorScatterMeasurement(Volts) STSDetectorMeasurement(Volts) IonDetectorBMeasurement(Volts) PTrakMeasurement(PtPerCC)/1000 (right) DustTrakAMeasurement(MgPerM3) (right) DustTrakBMeasurement(MgPerM3) (right) Two Dust Traks were used one with a 10 micron cut off and one with a 1 micron cutoff. The difference between the two gives an indication of the particle size distribution Teflon: Note similarity in Dust Traks indicating smaller particles 3 30 Teflon Test 25 GMT 268 ISSDetectorScatterMeasurement(Volts) STSDetectorMeasurement(Volts) IonDetectorBMeasurement(Volts) PTrakMeasurement(PtPerCC/1000) (right) 80 DustTrakAMeasurement(MgPerM3) (right) DustTrakBMeasurement(MgPerM3) (right) Silicone Rubber: Note difference in Dust Traks indicating large particles Time (Seconds) 19

20 SAME Raw Data Silicone Run 24 GMT 267 ISSDetectorScatterMeasurement(Volts) STSDetectorMeasurement(Volts) 7 IonDetectorBMeasurement(Volts) 80 PTrakMeasurement(PtPerCC)/1000 (right) 6 DustTrakAMeasurement(MgPerM3) (right) DustTrakBMeasurement(MgPerM3) (right) Teflon: Note weak scattering (ISS) detector signal but ionization (STS) is still strong Teflon Test 25 GMT 268 ISSDetectorScatterMeasurement(Volts) STSDetectorMeasurement(Volts) IonDetectorBMeasurement(Volts) PTrakMeasurement(PtPerCC/1000) (right) 80 DustTrakAMeasurement(MgPerM3) (right) DustTrakBMeasurement(MgPerM3) (right) Silicone Rubber: Note strong signal on both smoke detectors Time (Seconds) 20

21 DustTrak Ratio (10 micron mass / 1 micorn mass) Micron versus 1 micron Mass ratios Dust Track 10 micron/ 1 micron impactor mass ratio Kapton unaged Lampwick unaged Teflon unaged Silicone unaged Kapton Aged Lampwick Aged Teflon aged Silicone Aged Diameter of average mass (µm) 10 micron versus 1 micron mass ratios for different flow rates and sample temperatures 21

22 DustTrak Ratio (10 micron mass / 1 micorn mass) Micron versus 1 micron Mass ratios Dust Track 10 micron/ 1 micron impactor mass ratio Kapton unaged Lampwick unaged Teflon unaged Silicone unaged Kapton Aged Lampwick Aged Teflon aged Silicone Aged Diameter of average mass (µm) 10 micron versus 1 micron mass ratios for different flow rates and sample temperatures 22

23 SAME Flight Size Results for fresh and aged smoke Kapton Lampwick Silicone Teflon Pyrell Geometric Mean Diameter (Dg) (µm) Count Mean Diameter (M 1 /M 0 ) (µm) Diameter of Average Mass (M 3 /M 0 ) (µm) Unaged Aged 720 s Unaged Aged 720 s Unaged Aged 720 s Unaged Aged 720 s Unaged Aged 720 s σ g 23

24 Diamter of Average Mass (µm) Effect of Air Flow on Diameter of Average Diameter of Average Mass versus Air Speed Teflon Kapton LampWick Pyrell Silicone Air Flow (cm/s) Constant temperature for each material with no aging. 24

25 Diamter of Average Manss (µm) Effect of Aging on Diameter of Average Mass Diameter of Average Mass versus Aging (v=8cm/s Baseline T) Teflon Kapton LampWick Pyrell Silicone Aging Duration (s) 8 cm/s airflow Constant temperature for each sample. 25

26 Diameter of Average Mass, low-gravity results (µm) Effect of Gravity on Diameter of Average Mass 8 cm/s flow Diameter of Average Mass: low-gravity versus normal gravity 0.8 Teflon, Baseline Temperature Teflon,High Temperature 0.7 Teflon, Baseline Temperature, Aged Kapton, Baseline Temperature 0.6 Kapton, Teflon, High Baseline Temperature Teflon,High Temperature Kapton, Baseline Temperature, Aged Teflon, Baseline Temperature, Aged Kapton, Kapton, High Baseline Temperature, Aged 0.5 Lampwick, Kapton, Baseline High Temperature Temperature Kapton, Baseline Temperature, Aged Lampwick, High Temperature Kapton, High Temperature, Aged 0.4 Lampwick, Lampwick, Baseline Temperature, Aged Lampwick, High Lampwick, High Temperature, Aged Lampwick, Baseline Temperature, Aged Silicone, Lampwick, Baseline High Temperature, Temperature Aged 0.3 Silicone, Silicone, High Baseline Temperature Silicone, High Temperature Silicone, Baseline Temperature, Aged Silicone, Baseline Temperature, Aged 0.2 Pyrell, Pyrell, Baseline Baseline Temperature Pyrell, Pyrell, High High Temperature Pyrell, Baseline Aged Pyrell, Baseline Temperature, Aged 0.1 Pyrell, High Temperature, Aged Pyrell, Slope High = 1Temperature, Aged Slope = Diameter of Average Mass, normal-gravity results (µm)

27 Conclusions Particle sizes ranged from 100 to 600 nm Consistent with a log-normal distribution Particle sizes increase substantially with aging Particle dimensions increase substantially as air flow was decreased TEM showed a significant range of distinct particle morphologies For lampwick and silicone approximately 40% of the aerosol mass had aerodynamic diameters greater than 1 μm Ground based testing at 8 cm/s showed particle dimensions very close to the flight results 27

28 Conclusions Spacecraft fire conditions include an even wider array of materials and conditions. Spacecraft background aerosols can be quite large. Detection methods that can measure more than one moment of the size distribution may show more successful detection and false alarm rejection than single moment detectors. 28