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NASA CONNECT
2002-2003 SEASON
Measurement, Ratios, and Graphing:
Who Added the "Micro" to Gravity?
Jennifer Pulley
Hi, I'm Jennifer Pulley and welcome to NASA CONNECT, the
show that connects you to math, science, technology and NASA.
Today we're at NASA Glenn Research Center in Cleveland,
Ohio and THIS is the Zero Gravity facility and it's where NASA conducts
microgravity experiments.
You've seen microgravity. You've seen it in videos of the
International Space Station and NASA's KC-135.
On today's program, we'll investigate how NASA researchers
conduct research in a microgravity environment.
You'll observe NASA researchers using the math concepts
of measurement, ratios, and graphing to research combustion science and
the importance of fire safety on the International Space Station.
In your classroom you'll do a cool hands-on activity to
learn more about gravity by collecting, organizing, graphing, and analyzing
data.
And, using the instructional technology activity, you will
investigate apparent weight to see how astronauts in space can feel “weightless.”
NASA researchers use the math concepts of ratio, measurement
and graphing all the time. First, let's review ratios. A ratio is a comparison
of two quantities.
For example, NASA Glen Research Center and NASA Marshall
Spaceflight Center, which are the NASA facilities that primarily conduct
microgravity research, are two of ten NASA Centers located across the
country.
A ratio can be written as a fraction and it can be written
in any form that is equivalen to that fraction.
So the ratio two-tenths can also be written as…. 2:10,
20%, 20/100. and .20. When you work with ratios you can express fractions,
decimals, and percentages.
To learn how NASA researchers apply the concept of ratios
to the microgravity environment, let's go see Dr. Roger Crouch. He's the
Senior Scientist for the International Space Station.
Hey, Dr. Crouch!
Dr. Roger Crouch
Hello Jennifer! Math is very important to everyone, but
especially to scientists and engineers. We use ratios in every aspect of research in a microgravity
environment.
Jennifer Pulley
So, Dr. Crouch, what is microgravity?
Dr. Roger Crouch Microgravity is a condition
where the effects of gravity are or appear to be very much smaller than
they normally are here on Earth.
The prefix “micro” comes from the Greek root,
mikros, which simply means “small.”
However, in the scientific metric system, “micro”
literally means one part in a million or one to one millionth.
We use the term “microgravity” to describe
the environment on board a spacecraft in orbit around the earth.
Gravity is everywhere. We usually call it high gravity
if it is more than here on Earth, and low gravity if it is less than here
on Earth. An example of a low gravity environment
would be the moon. The gravity of the moon is about one sixth of that on
Earth.
Jennifer Pulley
Hey! 1/6th? That's a ratio!
Roger Crouch
That's right! What are the quantities
being compared in this statement?
The gravity of the moon is about one sixth of that on Earth.
If you said the moon's gravity to the Earth's gravity,
then you are starting to understand ratios.
The ratio 1/6th means that the gravity of the moon is six times smaller
than the gravity on Earth.
We sometimes use the term microgravity to describe a condition
where gravity is not small, but appears to be small. This is the condition
experienced on orbiting spacecraft, such as the International Space Station
or ISS, the Space Shuttle, and all objects in free fall. That's me appearing
to float inside the Space Shuttle. Really I'm not floating but, falling
at the same rate as the shuttle, so to the observer it looks like I'm
floating.
Jennifer Pulley
So Microgravity is not really zero gravity…
Dr. Roger Crouch
That's right. It diminishes relatively quickly with distance,
so its weaker on the space station than it is on Earth.
But it is 6400 km from the surface to the center of the
earth, which is considered the origin of the Earth's gravity field. Then,
the ISS is only another 400 km above the surface of the Earth. So, at
that altitude, the gravitational acceleration is still about 89% or 89/100th
of that at the Earth's surface.
If the gravitational acceleration at the Earth's surface
is 9.8 m/s2, what would be the gravitational acceleration be,
400 km above the Earth's surface?
Jennifer Pulley
Let's see. You would approximate the gravitational acceleration
400 km above the Earth's surface by calculating the product of 9.8 and
.89 or 89/100ths.
Dr. Roger Crouch
That's correct…
By multiplying 9.8 and .89, we see that the gravitational
acceleration at 400 km above the Earth's surface is about 8.7 m/s2. Comparing 9.8 and 8.7 m/s2…gravity
at the altitude of the ISS is nearly the same as that on Earth.
But given the images of floating astronauts, it appears
that gravity is reduced by much more than 11%.
Jennifer Pulley
So Dr. Crouch, what is happening here?
Dr. Roger Crouch
Gravity attracts all objects towards the center of the earth
at the same rate. If I release two objects of different weight and they
have room to fall, they will accelerate towards the center of the earth
at the same rate until they meet the resistance in the form of a floor,
for instance. In other words, they will hit the floor at the same time.
It's the force of the floor that we feel as our weight. When gravity is
the only force acting on an object, then it is said to be in state called
free fall. Objects in free fall can be said to be weightless.
Imagine you have an apple on a scale, which displays the
apple's weight. If you drop the scale, the apple and scale will fall together,
but the apple will no longer compress the scale, so the scale will show
zero weight.
In the same way, astronauts inside the ISS or the Space
Shuttle are falling around the Earth.
Unlike the apple on the scale, both the astronauts and the
spacecraft free fall by circling the Earth at approximately 7,870 m/s
or 17,000mph. They are falling towards the Earth, they just never get
there.
Jennifer Pulley
How are measurement and graphing important to NASA researchers
and scientists?
Dr. Roger Crouch
Research in the space environment gives scientists a new
tool for looking at phenomena in ways that are just not possible here
on Earth.
But these discoveries won't take place with out understanding
and applying the math concepts of measurement and graphing.
To demonstrate how NASA scientists and researchers use these
concepts, Dr. Sandra Olson, a Microgravity Combustion Scientist at the
NASA Glenn Research Center, will tell us more!
Jennifer Pulley
Great. Thank you so much, Dr. Crouch.
Dr. Roger Crouch
Thank You, Jennifer. I enjoyed it.
Jennifer Pulley
Now, before we visit Dr. Olson, let's review the math concepts
of measurement and graphing.
Measurement. It usually tells us the size of something and
it consists of a number and a unit.
For example, the gravitational acceleration at the surface
of the earth is 9.8 m/s2. 9.8 is called the number and m/s2
is called the unit. The unit in a measurement is a fixed quantity with
a size that is understood. The number in a measurement tells how many
units there are in what is being measured.
This allows us to compare the size of what is being measured
to the size of the unit. For example…
Dr. Crouch indicated that the gravitational acceleration
400 km above the Earth's surface is 8.7 m/s2 units compared
to the gravitational acceleration at the Earth's surface, which is 9.8
m/s2 units. Notice that the unit of measurement is the same
for both numbers.
And in case you are wondering, what does the unit m/s2
mean?
Well, 1 m/s2 or 1 m/s/s means that for every
second of travel the velocity increases by 1 m/s. So if the acceleration
due to gravity is 9.8 m/s2, then for every second of travel,
the velocity increases by 9.8 m/s.
Okay guys, the next concept for today's show is graphing.
And graphing is really important because it creates a visual representation
of relationships that you may not be able to determine using numbers alone.
And there are many types of graphs that can be used to visually represent
data.
There are bar graphs, circle graphs, line graphs, pictographs,
and scatter plots just to name a few.
Remember when Dr. Crouch told us that gravity diminishes
as we get farther and farther away from the Earth? We can represent this
visually with a graph. The x-axis or horizontal axis represents distance
and the y-axis or vertical axis represents gravity. From the graph you
can see that gravity decreases with increasing distance.
So, are you with me so far? Good. Let's go chat with Dr. Sandra
Olson, here at NASA Glenn Research Center.
Student #1
1. How do fires in space travel differently from fires on
Earth?
Student #2
2. From the Position vs. Time graph, what type of relationship
exists for the flamelets?
Student #3
3. What does the slope of a Position vs. Time graph tell
you?
Jennifer Pulley
Hey, Dr. Olson!
Dr. Sandra Olson
Hello Jennifer.
I'm glad you're able to come here to see our facility,
today. Thank You for asking me to explain how we use measurement and graphing
techniques in our research.
Jennifer Pulley
So, what kind of research do you do
here?
Dr. Sandra Olson
I do experiments in microgravity combustion
especially as it relates to spacecraft fire safety.
You know, Jennifer, we're told as children that if there
is a fire in our house, we are supposed to get out of the house and call
the fire department.
But in spacecraft, this isn't an option.
There are no fire departments in space and you just can't walk outside.
A bad fire actually happened on the Russian Mir space
station in 1997. We need to understand fire behavior in microgravity so
that we will know how to avoid the fire as much as possible and survive
it if it does occur.
Jennifer Pulley
Now, Dr. Olson, it sounds to me like you're saying that
fire behaves differently in space than it does here on Earth?
Dr. Sandra Olson
Very differently, Jennifer.
Gravity is such a dominant force in fires here on Earth
that we take it for granted. For example, wildfires are very gravity dependent.
On Earth, wildfires spread uphill much faster than downhill.
The reason for this is that the heated air from the fire
rises up the hill and heats the fuel like the grass, trees, and shrubs
ahead of the fire. 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, going
downhill, the wind is fresh cool air being drawn into the fire to replace
the rising hot gases. The vegetation remains cool until the flames are
very close. The flames reach is very short, and it takes longer to heat
up the cold fuel and the flame spreads more slowly.
In space, fires like to go in the exact opposite direction!
They like to spread against the wind, while wildfires are blown by the
wind. Because hot air doesn't rise in a microgravity environment, the
only air flows in an orbiting spacecraft come from ventilation fans, cooling
fans and crew movements. A fire, given a choice in this microgravity environment,
will preferentially spread into the fresh air.
The flame doesn't have control over the airflow, so it
has to seek out the fresh air. The wind-blown or down wind side of
the flame is only receiving “polluted” air that contains smoke
and carbon dioxide but not much oxygen because that's already consumed by
the upwind side of the flame. So when the air flows from the ventilation
fans are low, the downwind side of the flame can't spread at all –
even though it has fuel and heat, it doesn't have the oxygen.
In a microgravity environment, if we reduce the airflow, even the oxygen-seeking
upwind side of the flame has trouble getting enough oxygen, and it breaks
up into little “flamelets”.
Jennifer Pulley
Okay. So how do you measure or collect data on these
little flamelets?
Dr. Sandra Olson
In our experiments, we use this droppable wind tunnel to
study the effect of airflow on the flamelets. When we drop this miniature
wind tunnel, we can get brief periods of microgravity here on Earth.
We can measure the effect of air flow on the flame by applying
a very low-speed airflow to a flame as it spreads across a thin sheet
of paper. As it spreads we can measure its position as a function of time
and plot Time and Position on a graph.
The following graph allows us to compare position vs.
time for flamelet tracking. The x-axis or horizontal axis is the time measured
in seconds and the y-axis or vertical axis is the position of the flame
measured in millimeters.This graph represents a flame that starts out uniform
and after 5 seconds of travel, breaks up into flamelets. The point (0,0)
represents the location where the uniform flame breaks up into flamelets.
Jennifer Pulley
Okay, Dr. Olson. From this graph, there appears to be
a linear relationship between position and time. Why is the slope of the
line representing the uniform flames steeper than the line representing
the flamelets?
Dr. Sandra Olson
That's a great question Jennifer. The steepness or slope
of the line tells us the spread rate or velocity of the flame.
Jennifer Pulley
So let me see if I get this. As the slope of a line decreases,
then the spread rate or velocity decreases.
Dr. Sandra Olson
That's correct. For this particular test run, the velocity
of the uniform flame was calculated to be 3.4 mm/s and the velocity of the
flamelets was calculated to 1.0 mm/s. Although the flamelets spread more
slowly, they're very hard to detect and they can flare up into a big fire
again if we turn up the airflow. Imagine if the astronauts put out a fire
and then turned on the air circulation system to clean up the smoke. The
fire could flare up again!
Jennifer Pulley
Wow.I can see how important your research is to safety
of the astronauts on board the International Space Station and the Space
Shuttle. Thank you so much Dr. Olson!
Dr. Sandra Olson
Thank YOU, Jennifer.
Jennifer Pulley
Hey kids! It's now time for a cue card review.
Kids
1. How do fires in space travel differently from fires on
Earth?
2. From the Position vs. Time graph, what type of relationship
exists for the flamelets?
3. What does the slope of a Position vs. Time graph tell
you?
Jennifer Pulley
Ok, let's review. We highlighted the math concepts of ratios,
measurement, and graphing. Dr. Crouch applied the concept of ratios to
help us define microgravity. And Dr. Olson explained the importance of
measurement and graphing while conducting spacecraft fire safety research.
Now it's your turn to apply these math concepts in your
classroom. Check out this program's awesome hands-on activity.
Student #1
Hi! We're students at Northside Middle School here in Norfolk,
Virginia!
Student #2
NASA CONNECT asked us to show you this program's hands-on
activity.
Student #3
You can download the lesson guide and a list of materials
from the NASA Connect web site.
Student #4
Here are the main objectives!
Dan Geroe
·
apply techniques to determine measurements.
·
use metric measurement.
·
build mathematical knowledge through investigation and experimentation.
·
collect, organize and graph data for analysis.
·
build an understanding of microgravity.
Teacher
Good morning class. Today, NASA has asked us to investigate
how Graphing techniques are helpful in understanding the concepts of position,
velocity, and acceleration.
Dan Geroe
Teachers will find a location for dropping pre-selected
objects. A set of bleachers provides a good variation in heights, without
using ladders.
Mark the drop location in even increments, if possible.
Eight to ten drop stations create a good graph that students can easily
view. Measure each station in meters or inches and use the conversion: 1m
= 3.281 ft. Organize students into groups of four. Once each
group has selected a different ball to use for all their test drops, distribute
the student materials. A Student Recorder writes down the height
of each drop station on the data collection chart. A Student
Timer records five drops at each drop station. Only the Ball
Dropper should climb to the drop site, with the rest remaining at ground
level. The Student Counter returns the ball to the dropper and
begin the countdown again when everyone is ready. Average the
times for each drop station, and record on the data collection chart.
Square the average times for each drop station and record on the data collection
chart.
Using height and average time data for each drop station,
plot a distance vs. time graph on Drop Data Chart 1.
Using height and average squared time data for each drop
station, plot a distance vs time squared graph on Drop Data Chart 2.
The teacher will collect the Drop Data Chart s from each
group and Compare the data on Drop Data Chart 1 for each ball and discuss
the shape the data point create.
Next, Overlay all Drop Data Chart 1 transparencies to compare
the data simultaneously.
In the next comparison, compare the data on Drop Data Chart
2 for each ball and discuss the shape the data points create.
Again, overlay all Drop Data Chart 2 transparencies to compare
the data simultaneously.
Teacher
It's time for questioning. Based on your observations, predict
what will happen to the acceleration if the object is dropped from a greater
height? Christine.
Student
I don't think it will matter where you drop the ball from
the bleacher. The acceleration will remain the same.
Teacher
Great answer. Mr. Coppola?
Other Teacher
Thank You. Did the shape or surface of the object dropped
have any effect on the results? Explain. John!
Student
I don't think that it will have any effect on this experiment
because we are using objects such as a ball and the air resistance is
negligible. But, on
the other hand, if you were to use an object such as a piece of paper
it would float down and it would take longer to hit the ground.
Dan Geroe
Teachers, if you would like help to perform the preceding
lesson or any other NASA CONNECT lesson, simply enlist the help of an
AIAA Mentor who will be glad to assist your class in these activities!
Jennifer Pulley
Super job you guys! Hey! Did you know that NASA is working
with students to develop new products and new experiments for space research?
Dr. John Pojma,n a Professor of Chemistry and Biochemistry at the University
of Southern Mississippi, has some cool applications for microgravity research
which students like you can be working on someday!
Student #1
What is buoyancy-induced convection?
Student #2
What is the relationship between density and volume?
Student #3
What is the trend in the Density vs. Temperature Graph?
Dr. John Pojman
Hi! Nasa's Reduced Gravity Program began in 1959 but in
the past five years students from more than 100 schools have been conducting
experiments in a microgravity environment!
Several of my students and I have flown on the KC-135,
NASA's flying laboratory. It's science that is interesting, challenging
and fun. One experiment we are conducting involves making new
space age materials by a really cool process called frontal polymerization
and the other involves studying how molecules attract each other in fluids
that mix. Everything is made up of very, very small pieces of
stuff called 'molecules'. Molecules attract each other. How strongly
they attract determines if the stuff is a liquid, solid or gas. Some
materials mix completely. Others do not. Here is something you can
try at home yourself. We
have water here which has food coloring in it and syrup. And as I pour the
syrup in and stir it up, it will make one continuous liquid.
But if I take something that is immiscible with water like mineral oil and
pour it into the water with food coloring and mix this solution up, it will
separate into two layers with time.
Water molecules attract each other more strongly than they attract
oil molecules and so the water stays separate. A monomer is a small
molecule that can be made to form long chains of monomers connected end
to end, called a polymer. It's sort of like boxcars hooked together to form
a train. The mixing process is called convection.
It is the term for liquid motion. There are two ways in which
convection can spontaneously occur in a liquid. One is
caused by gravity and is called buoyancy-induced convection. Differences
between the densities of the liquids make the lighter fluid rise and SEPARATE
from the heavier fluid. Another type of convection is called
interfacial-tension induced convection.
Kid
Interfacial WHAT?!!
Dr. John Pojman
Interfacial-tension induced convection. Let's split the
term up.
First, interfacial tension is like the surface tension
which holds up a water bug when it skitters across a pond. The surface
is the result of the water molecules ATTRACTING each other.
But heating a surface here on earth causes buoyancy-induced
convection. How can we study only the convection caused by interfacial
effects alone?
We need to eliminate gravity - or its effects. We
can never eliminate gravity but by free falling we can create a system
that acts as if there were no gravity.
Performing experiments In weightlessness allows us to study
phenomena we can't study on earth and to answer questions we can't answer
down here.
By eliminating buoyancy-induced convection, we sometimes
can create superior protein crystals in weightlessness that can help researchers
design new drugs.
Eliminating buoyancy-induced convection can also help us
understand how to make better semiconductors here on earth -- like the
ones used in your computer.
We take a lesson from computer chip manufacturers who use
light to make the circuit patterns.
Microgravity research shows us that we can create patterns on fluids
which would not be allowed on Earth where buoyancy-convection mixes up
the patterns due to gravity.
My students and I are studying how forces between molecules
in fluids that mix can cause convection.
We use light as an initiating agent to make the monomer
turn into the polymer. By exposing the monomer to light with a specific
pattern, we hope to observe how the monomer and polymer molecules pull
on each other. For many minutes, we predict that the two fluids will
act like oil on water.
But in the long run, the molecules will diffuse into each
other and make a single fluid.
Why can't we do the experiment in the lab? Because buoyancy-driven
convection will smear everything out. So there is "no way on
earth" to do the experiment.
We also study a process called frontal polymerization in
which plastics and foams can be made with a chemical reaction that spreads
out like a “liquid flame'. Gases can be released by the hot reaction
that makes bubbles, which can form the foam.
Of course, bubbles float in a
liquid because of gravity.
Without the buoyant force, bubbles can become larger in a microgravity
environment.
Kid
How do you use math in your work?
Dr. John Pojman
Math is essential to our work. For example, in order to
predict how gravity will cause convection, we need to prepare graphs of
the density of our materials as a function of temperature. We use a special
instrument called a densitometer but we have to know how to use math to
make sense of what it tells us.
Let's look at some of the data from my lab. Here we have
plotted the densities of the monomer and the polymer on the y-axis and
the temperature on the x-axis.
First, notice that the density of the polymer is higher than the
monomer. Next, We can draw straight lines through the points. The slope
of each line is the ratio of the change in density to the change in temperature.
The density of the polymer decreases 0.03 g per cubic centimer
for a 50 degree centrigade increase in temperature. The density of the
monomer also decreases but it decreases 0.04 g per cubic centimeter for
the same temperature change.
As we go farther and farther from Earth into space, we're
going to be required eventually to make our own materials in space. It's
a whole lot cheaper to carry up polymeric – reacting materials than
to carry up bulky building materials. Foams are just one of the things
we need to look at.
Remember we said buoyancy-driven convection happens because
of differences in density and that the less dense liquids will float to
the top. The information from this graph tells us how the density
changes when we heat the monomer and polymer and so we can predict how
much buoyancy-driven convection will occur during experiments on earth.
The graph also tells us how much the volume changes as we heat the liquids
-- essential information for designing our experiment on the International
Space Station.
As we go farther and farther from Earth into space, we're
going to be required eventually to make our own materials in space. Foams
are just one of the things we need to look at. Gaining an understanding
of the new opportunities in microgravity research today, will be valuable
knowledge when you, the young researchers of today are ready for our first
manned flight to Mars.
s
What is buoyancy-induced convection
What is the relationship between density and volume?
What is the trend in the Density vs. Temperature Graph?
Jennifer Pulley
Okay, did you get all that?
Let's go visit Dan Geroe in his web Domain
Dan Geroe
Hi and welcome to my domain! NASA CONNECT has created a
really cool web activity to help you investigate apparent weight and to
see how astronauts in outer space can feel “weightless.” We
also have a second activity to help you make an important elevator design
decision.
First, be sure you have the Squeak plug-in. It can be downloaded
at www.squeakland.org for easy installation.
Once you have the Squeak plug-in installed, you can access
the activity at the NASA CONNECT web site under Dan's Domain! This activity
is designed for use by students, teachers, and parents in the school or
home setting.
Now you are ready to start the activity.
On this site, Norbert and Zot are waiting in an elevator
for you to investigate what happens when you accelerate the elevator. If you are the hands-on type and
want to try on your own at first, read the brief directions along the
left side of the screen and start by trying to make Norbert and Zot weightless.
Then you should read the book on the right side of the screen
for important definitions, brief interactivities, explorations you should
do, and challenges you should consider. If you want more directions before
you start, begin by reading the book starting with the first page and
click the little right arrow at the top center to go on.
To help you get a head start, velocity is the distance traveled
divided by the time it takes. If the elevator moves Norbert and Zot downward,
we will say their velocity is a positive number. To accelerate is to change
the velocity. If you increase the velocity in the downward direction,
we will say the acceleration is a positive number, then if you increase
the velocity in the upward direction, we will say the acceleration is
a negative number. Positive and negative numbers are essential to describe
motion.
Have fun and explore!
Jennifer Pulley
Well guys, that wraps up another episode of NASA CONNECT!
Got a comment, question or suggestion? Then Email us at
connect@larc.nasa.gov.
Or pick up a pen and write us at
NASA CONNECT
NASA's Center for Distance Learning
NASA Langley Research Center
Mail Stop 400
Hampton, VA 23681
Teachers, if you would like a videotape of this program
and the accompanying educator's guide, check out the NASA CONNECT web
site.
So, until next time, stay connected to Math, Science, Technology,
and NASA! See you then!
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