1 00:00:00,000 --> 00:00:06,940 So are you with me so far? Good. Let's go chat with Dr. Sandra Olson here at NASA Glenn Research Center 2 00:00:10,420 --> 00:00:15,820 How do fires in space travel differently from fires on earth from the position versus time graph 3 00:00:15,820 --> 00:00:21,600 What type of relationship is this from the flameless? What is the slope of a position versus time graph tell you? 4 00:00:22,320 --> 00:00:27,160 Hey, dr. Olson. Hello Jennifer. I'm glad you're able to come and see our facility today 5 00:00:27,340 --> 00:00:31,440 Thank you for asking me to explain how we use measurement and graphing techniques in our research 6 00:00:31,860 --> 00:00:36,880 So what kind of research do you do here? I do experiments in microgravity combustion 7 00:00:36,880 --> 00:00:40,380 Especially as it relates to spacecraft fire safety, you know, Jennifer 8 00:00:40,380 --> 00:00:42,880 We're told as children that if there's a fire in our house 9 00:00:42,880 --> 00:00:47,460 We're supposed to get out of the house and call the fire department but in spacecraft this isn't an option 10 00:00:47,460 --> 00:00:51,220 there are no fire departments in space and you just can't walk outside a 11 00:00:51,500 --> 00:00:55,660 Bad fire actually happened on the Russian Mir space station in 1997 12 00:00:55,880 --> 00:00:58,200 We need to understand fire behavior in microgravity 13 00:00:58,720 --> 00:01:04,340 So that we will know how to avoid the fire as much as possible and survive it if it does occur now, dr 14 00:01:04,340 --> 00:01:09,880 Olson it sounds to me like you're saying that fire behaves differently in space than it does here on earth 15 00:01:10,120 --> 00:01:15,480 Very differently Jennifer gravity is such a dominant force in fires here on earth that we take it for granted 16 00:01:16,120 --> 00:01:22,440 For example, a wildfire is very gravity dependent on earth wildfires spread uphill much faster than downhill 17 00:01:22,660 --> 00:01:27,620 The reason for this is that the heated air from the fire rises up the hill and heats the fuel 18 00:01:27,780 --> 00:01:30,560 Like the grass trees and shrubs ahead of the fire 19 00:01:30,900 --> 00:01:37,940 Blown into the wind the fire's reach is long and it can spread very fast over the nice warm fuel on the other hand 20 00:01:37,940 --> 00:01:44,120 Going downhill. The wind is fresh cool air being drawn into the fire to replace the rising hot gases 21 00:01:44,300 --> 00:01:47,900 The vegetation remains cool until the flames are very close 22 00:01:48,120 --> 00:01:54,120 The flames reach is very short and it takes longer to heat up the cold fuel and the flame spreads more slowly 23 00:01:54,520 --> 00:01:57,760 In space fires like to go in the exact opposite direction 24 00:01:58,320 --> 00:02:02,480 They like to spread against the wind while wildfires are blown by the wind 25 00:02:03,040 --> 00:02:05,680 Because hot air doesn't rise in a microgravity environment 26 00:02:06,280 --> 00:02:12,920 the only air flows in an orbiting spacecraft come from ventilation fans cooling fans and crew movements a 27 00:02:13,140 --> 00:02:15,980 Fire given a choice in this microgravity environment 28 00:02:16,700 --> 00:02:22,060 Will preferentially spread into the fresh air the flame doesn't have any control over the airflow 29 00:02:22,060 --> 00:02:28,100 So it has to seek out the fresh air the windblown or downwind side of the flame is only receiving polluted air 30 00:02:28,220 --> 00:02:35,100 That contains smoke and carbon dioxide, but not much oxygen because that's already been consumed by the upwind side of the flame 31 00:02:35,620 --> 00:02:41,700 So when the air flows from the ventilation fans are low the downwind side of the flame can't spread at all 32 00:02:41,880 --> 00:02:48,020 Even though it has fuel and heat it doesn't have the oxygen in a microgravity environment if we reduce the airflow 33 00:02:48,600 --> 00:02:54,640 Even the oxygen-seeking upwind side of the flame has trouble getting enough oxygen and it breaks up into little flamelets 34 00:02:54,920 --> 00:03:01,000 Okay, so how do you measure or collect data on these little flamelets in our experiments? 35 00:03:01,000 --> 00:03:07,220 We use this droppable wind tunnel to study the effect of airflow on the flamelets when we drop this miniature wind tunnel 36 00:03:07,220 --> 00:03:09,980 We can get brief periods of microgravity here on earth 37 00:03:10,600 --> 00:03:15,080 We can measure the effect of airflow on the flame by applying a very low speed air flow 38 00:03:15,160 --> 00:03:19,000 To a flame as it spreads across a thin sheet of paper as it spreads 39 00:03:19,000 --> 00:03:24,380 We can measure its position as a function of time and plot time and position on a graph 40 00:03:24,860 --> 00:03:29,760 The following graph allows us to compare position versus time for flamelet tracking 41 00:03:30,000 --> 00:03:37,100 The x-axis or horizontal axis is the time measured in seconds and the y-axis or vertical axis 42 00:03:37,100 --> 00:03:39,780 Is the position of the flame measured in millimeters? 43 00:03:40,200 --> 00:03:46,800 This graph represents a flame that starts out uniform and after five seconds of travel breaks up into flamelets 44 00:03:47,120 --> 00:03:49,120 The point zero zero 45 00:03:49,360 --> 00:03:54,920 Represents the location where the uniform flame breaks up into flamelets. Okay, dr. Olson from this graph 46 00:03:54,920 --> 00:03:58,120 there appears to be a linear relationship between position and 47 00:03:58,880 --> 00:04:06,120 Time why is the slope of the line representing the uniform flame steeper than the line representing the flamelets? 48 00:04:06,540 --> 00:04:08,540 That's a great question Jennifer 49 00:04:08,580 --> 00:04:13,140 The steepness or slope of the line tells us the spread rate or the velocity of the flame 50 00:04:13,380 --> 00:04:20,640 So, let me see if I get this as the slope of the line decreases then the spread rate or velocity decreases. That's correct 51 00:04:21,020 --> 00:04:27,820 For this particular test run the velocity of the uniform flame was calculated to be three point four millimeters per second 52 00:04:27,820 --> 00:04:32,460 And the velocity of the flamelets was calculated to be one point zero millimeters per second 53 00:04:32,680 --> 00:04:34,680 Although the flamelets spread more slowly 54 00:04:34,680 --> 00:04:38,960 They're very hard to detect and they can flare up into a big fire again 55 00:04:38,960 --> 00:04:40,760 If we turn up the airflow 56 00:04:40,760 --> 00:04:46,000 Imagine if the astronauts put out a fire and then turned on the air circulation system to clean up the smoke 57 00:04:46,080 --> 00:04:47,720 The fire could flare up again 58 00:04:47,720 --> 00:04:48,240 Wow 59 00:04:48,240 --> 00:04:55,240 I can see how important your research is to the safety of the astronauts on board the International Space Station and the space shuttle 60 00:04:55,360 --> 00:04:57,920 Thank you so much. Dr. Olson. Thank you Jennifer 61 00:04:58,520 --> 00:05:01,320 Hey kids, it's now time for a cue card review 62 00:05:01,820 --> 00:05:07,180 How do fires in space travel differently from fires on earth from the position versus time graph? 63 00:05:07,180 --> 00:05:12,980 What type of relationship exists from the flamelets? What is the slope of a position versus time graph tell you?