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Microgravity Combustion - Contenido educativo
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NASA Connect segment explaining how fires in space act differently than on earth. The segment also explores flamelets and the idea of slope on a position versus time graph.
So are you with me so far? Good. Let's go chat with Dr. Sandra Olson here at NASA Glenn Research Center
00:00:00
How do fires in space travel differently from fires on earth from the position versus time graph
00:00:10
What type of relationship is this from the flameless? What is the slope of a position versus time graph tell you?
00:00:15
Hey, dr. Olson. Hello Jennifer. I'm glad you're able to come and see our facility today
00:00:22
Thank you for asking me to explain how we use measurement and graphing techniques in our research
00:00:27
So what kind of research do you do here? I do experiments in microgravity combustion
00:00:31
Especially as it relates to spacecraft fire safety, you know, Jennifer
00:00:36
We're told as children that if there's a fire in our house
00:00:40
We're supposed to get out of the house and call the fire department but in spacecraft this isn't an option
00:00:42
there are no fire departments in space and you just can't walk outside a
00:00:47
Bad fire actually happened on the Russian Mir space station in 1997
00:00:51
We need to understand fire behavior in microgravity
00:00:55
So that we will know how to avoid the fire as much as possible and survive it if it does occur now, dr
00:00:58
Olson it sounds to me like you're saying that fire behaves differently in space than it does here on earth
00:01:04
Very differently Jennifer gravity is such a dominant force in fires here on earth that we take it for granted
00:01:10
For example, a wildfire is very gravity dependent on earth wildfires spread uphill much faster than downhill
00:01:16
The reason for this is that the heated air from the fire rises up the hill and heats the fuel
00:01:22
Like the grass trees and shrubs ahead of the fire
00:01:27
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
00:01:30
Going downhill. The wind is fresh cool air being drawn into the fire to replace the rising hot gases
00:01:37
The vegetation remains cool until the flames are very close
00:01:44
The flames reach is very short and it takes longer to heat up the cold fuel and the flame spreads more slowly
00:01:48
In space fires like to go in the exact opposite direction
00:01:54
They like to spread against the wind while wildfires are blown by the wind
00:01:58
Because hot air doesn't rise in a microgravity environment
00:02:03
the only air flows in an orbiting spacecraft come from ventilation fans cooling fans and crew movements a
00:02:06
Fire given a choice in this microgravity environment
00:02:13
Will preferentially spread into the fresh air the flame doesn't have any control over the airflow
00:02:16
So it has to seek out the fresh air the windblown or downwind side of the flame is only receiving polluted air
00:02:22
That contains smoke and carbon dioxide, but not much oxygen because that's already been consumed by the upwind side of the flame
00:02:28
So when the air flows from the ventilation fans are low the downwind side of the flame can't spread at all
00:02:35
Even though it has fuel and heat it doesn't have the oxygen in a microgravity environment if we reduce the airflow
00:02:41
Even the oxygen-seeking upwind side of the flame has trouble getting enough oxygen and it breaks up into little flamelets
00:02:48
Okay, so how do you measure or collect data on these little flamelets in our experiments?
00:02:54
We use this droppable wind tunnel to study the effect of airflow on the flamelets when we drop this miniature wind tunnel
00:03:01
We can get brief periods of microgravity here on earth
00:03:07
We can measure the effect of airflow on the flame by applying a very low speed air flow
00:03:10
To a flame as it spreads across a thin sheet of paper as it spreads
00:03:15
We can measure its position as a function of time and plot time and position on a graph
00:03:19
The following graph allows us to compare position versus time for flamelet tracking
00:03:24
The x-axis or horizontal axis is the time measured in seconds and the y-axis or vertical axis
00:03:30
Is the position of the flame measured in millimeters?
00:03:37
This graph represents a flame that starts out uniform and after five seconds of travel breaks up into flamelets
00:03:40
The point zero zero
00:03:47
Represents the location where the uniform flame breaks up into flamelets. Okay, dr. Olson from this graph
00:03:49
there appears to be a linear relationship between position and
00:03:54
Time why is the slope of the line representing the uniform flame steeper than the line representing the flamelets?
00:03:58
That's a great question Jennifer
00:04:06
The steepness or slope of the line tells us the spread rate or the velocity of the flame
00:04:08
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
00:04:13
For this particular test run the velocity of the uniform flame was calculated to be three point four millimeters per second
00:04:21
And the velocity of the flamelets was calculated to be one point zero millimeters per second
00:04:27
Although the flamelets spread more slowly
00:04:32
They're very hard to detect and they can flare up into a big fire again
00:04:34
If we turn up the airflow
00:04:38
Imagine if the astronauts put out a fire and then turned on the air circulation system to clean up the smoke
00:04:40
The fire could flare up again
00:04:46
Wow
00:04:47
I can see how important your research is to the safety of the astronauts on board the International Space Station and the space shuttle
00:04:48
Thank you so much. Dr. Olson. Thank you Jennifer
00:04:55
Hey kids, it's now time for a cue card review
00:04:58
How do fires in space travel differently from fires on earth from the position versus time graph?
00:05:01
What type of relationship exists from the flamelets? What is the slope of a position versus time graph tell you?
00:05:07
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- Materias:
- Matemáticas
- Niveles educativos:
- ▼ Mostrar / ocultar niveles
- Nivel Intermedio
- Autor/es:
- NASA LaRC Office of Education
- Subido por:
- EducaMadrid
- Licencia:
- Reconocimiento - No comercial - Sin obra derivada
- Visualizaciones:
- 165
- Fecha:
- 28 de mayo de 2007 - 16:52
- Visibilidad:
- Público
- Enlace Relacionado:
- NASAs center for distance learning
- Relación de aspecto:
- 4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
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