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Hydroponics · Magnetic Chamber · Newton's Laws· Effervescence · Chromatography · Simple Machines · Live Lesson 1 · Live Lesson 2
WHERE WE’VE BEEN AND WHERE WE’RE GOING,
WHY?
Challenger’s Second Lost Live
Lesson
“Marshmallows…otherwise known as cotton balls and (candy) beans!”
Where We’ve Been
and Where We’re Going, Why?
(8.2 MB, hi-res wmv file 23.3 MB)
Challenger’s Second Live Lesson
Introduction:
Besides
the six lost science lessons scheduled for filming aboard Challenger, two televised “live lessons” were planned for the sixth
day of the mission. The time scheduled
for each was fifteen minutes. These were
to be aired on the Public Broadcasting
Network (PBS) at 10:40 a.m. and 10:40 p.m. Central Standard Time.
Unlike,
the first live lesson which was a simple tour of the Shuttle, the second is
much like the filmed six lost lessons. However, only fifteen minutes time was planned for its execution. The second live lesson is addressed in some
detail in Bob Mayfield’s paper. It was
entitled “Where
We’ve Been, Where We’ve Going, Why?”(8.2 MB, hi-res wmv file 23.2 MB). Reading the planned choreography of various mixing demonstrations shows the challenge Christa faced. Remembering that Christa was expected to
narrate each demonstration impresses all with Christa’s demeanor. Throughout
the practice video, she appears cheerful, dedicated and fully in command of
what was expected of her. This she did
despite knowing that millions of students, young and old, would be attending her class on day 6 of the
mission.
Background:
The
background description for the second
live lesson, “Where We’ve Been and Where We’re Going Why? ” comes from the NASA
publication: “Teacher in Space Project:”
Where We’ve Been, Where We’re Going,
Why?
Viewer Objectives:
1.
To explain some advantages and disadvantages of
manufacturing in a microgravity environment
2.
To describe spinoffs and other benefits which have
evolved from the space program
3.
To list ways in which the modular Space Station would
change the lives of human beings
Video Lesson Description:
As
the lesson from space begins, Christa McAuliffe will refer to the models of the Wright Brothers’ plane and of a proposed
NASA Space Station to help viewers recall that only 82 years separate that early flight and today’s life
in space.
McAuliffe
will discuss the reasons we are living and working in space, covering
astronomy, Earth observations, experiments on-board the Shuttle, satellites
on-board the mission, materials processing, and technological advances.
Discussion:
After
reading the above scenario, watch the
video once more, starting with the set up planning
video (9.2 MB, hi-res wmv file 24.4 MB) by Christa, Barbara Morgan, and Astronaut Mike Smith. Note the camera is mounted on a tripod. [This
is a video camera, not the film camera to have been employed for the six lost
lessons. The motion picture camera was
called the Airiflex and is shown below being examined by Christa and
Barbara. The video camera used in the
ground practice is shown in the below right photo. While the film camera seems quite cumbersome
compared to the video counterpart, in zero-g the Airiflex mass would be quite
manageable.]
Concerning
the tripod, Pilot Mike Smith talks in the video of “coming down from the flight
deck to help set up the camera.” This
indicates the tripod would have been used as the camera’s permanent mount for the live lesson,
otherwise, it would have floated randomly about.
Because
the live lesson camera, unlike that to be used for the six lost lessons, was a
video type, it would have broadcast a
television signal via the Public Broadcasting System, an educational television network seen throughout the
Christa’s second live lesson practice begins in the mid-deck area. In preparation for the scene, Christa asks Judy Resnik, who is controlling the camera, to zoom in for the best view of the scene. What Judy views is seen on her monitor displayed at the camera control station.
After
some planning, the practice begins with the words, “Challenger, (This is)…
In
order to more carefully analyze the second live lesson, a portion of Bob
Mayfield’s description is repeated below along with the editor’s comments in
brackets […].
“Several
demonstrations will be conducted to illustrate
the behavior of materials in microgravity. A sphere of orange juice will be
formed carefully from a drink container. The fact that liquids form perfect
spheres in space is useful in forming mono-disperse latex beads, for instance, which can be used by the Bureau of Standards. Mixing of molecules of different substances
will be illustrated using marshmallows and
chocolate candies in a plastic bag. [This is what Christa is alluding to in the
bag of cotton balls chosen to replicate the marshmallows.]
Mixing of liquids of differing densities will be demonstrated
using salad oil and colored water sealed in lexan bottles. [Christa
reaches for a container representing one of the lexan bottles. It topples onto
the floor of the mock-up mid-deck. Her
comment shows her wonderful sense of humor, “Whoops…this zero gravity environment is
just awful!”(290 KB, hi-res wmv file 1.2 MB)]
 |
Two
of these containers will be used. One has 1/2 water and 1/2 oil. The other
contains 1/3 water, 1/3 oil, and 1/3 air.
These can be compared to determine how the presence of the air affects the way
the liquids behave. A marble is in each bottle to stir the mixture. Also, the teacher [Christa] will use a large quartz crystal
to discuss the special conditions conducive
to the growth of large crystals, especially
relating to the growth of crystals in space. “
A Classroom Version of Christa’s
“Where We’ve Been and Where We’re Going, Why?”
Lost Lesson
The following demonstration replicates Christa’s planned live lesson
experiment:
Principles:
The crux of the second live lesson is fluid behavior in zero-g. The focus deals with fluid mixing behavior as well as settling behavior. An important facet of the demonstration is comparing these actions with earth-based techniques under the influence of gravity. While a qualitative demonstration is not complicated, the scientific explanations dealing with surface tension and other molecular forces are quite involved, perhaps, to a greater extent than the six filmed lessons. However, the discussion of differences between gravity forming and mixing phenomena versus zero-g results is useful. For example, the dropping of a raindrop earthward would be in “free-fall”, i.e., in zero-g, but the added effect, friction, of air molecules contacting the falling drop would distort its spherical form. Such would not be the case aboard Challenger. No gravity would cause a drop of liquid to speed through the cabin atmosphere. These kinds of qualitative considerations would be a benefit of the live lesson mixing and liquid formation demonstrations.
A principle which earth based fluids
obey is “buoyancy”, the separation of fluids by virtue of their density or
“weight per unit volume” which cause lighter fluids to float on top of denser
heavier liquids. Of course, without
gravity, buoyancy is absent. In such an
environment fluids of varying densities might be expected to mix more readily
such that the resulting liquid is a uniform composite mixture. Earth based mixing depends on the physical
shaking of the multi-fluid mixture to assume a uniform composition temporarily
until the effects of buoyancy slowly separate the fluids once more. The use of gravity can be helpful in separate
fluids of differing densities. For this
reason, increasing the applied force above that of gravity makes a “centrifuge”
useful in “precipitating” a material from a solution. The added centrifugal force acts to separate
the solid substance from the fluid, depositing the precipitate on the bottom of
the centrifuge test tube. In zero-g,
such an apparatus would prove helpful in separating materials from a liquid
solution, especially since gravity is not present to simply let settling work
to form the precipitate.
Fortunately, among the video clips of
Christa and others in the zero-g aircraft, are bubbles sailing about the KC-135
interior. These are, actually, produced
by the effervescing tablet gas bubbles escaping inadvertently from the
experiment container. In zero-g these
would be expected to form spheres. However, because of the lightness, (i.e., small mass) of the air
contained within the bubble formed by surface tension, these bubbles would have
formed in a gravity environment as well. Indeed, they are simply the same manifestation as those bubbles produced
by a child’s bubble ring kit. Nevertheless, this is a useful scenario.
Liquids in orbit behave like soap
bubbles on earth. It is because both
have such little mass compared to the force of molecular surface tension. Also,
the pressure of the air pushing on the bubble is equal to the gas within the bubble
keeping the bubble inflated like a balloon. The effects of gravity do not distort (“pop”) these spherical gas bubble
shapes. [Note: Behind Christa, Bob Mayfield, and Barbara Morgan, a man throws a ball over their heads while
they practice the experiment. The ball
is thrown in a trajectory which bounds off the ceiling of the KC-135
aircraft. Based on the speed of the ball
overhead, it would be expected to strike Christa, Bob, or Barbara. Instead, it simply continues above them as
though gravity does not exist. This is
added evidence how balls, liquids, bubbles and people behave in
zero-gravity. They simply float in mid
air.]
(Depress the “CTR:” key and click here (1 MB, hi-res wmv file 3.1 MB) to watch Christa
inadvertently produce her zero-g bubbles.) The scene serves to demonstrate what Christa might have shown during
the second life lesson scheduled for
day-six of the Challenger mission. Additionally, the zero-g mixing
demonstration could have been easily done in the KC-135 aircraft.
In fact, similar experiments have been
done by NASA using that aircraft as a test bed. Below are a pair of videos showing the effect of zero-g compared to
one-g on mixing of liquids of different
densities. Their different colors differentiate them. Click here (500 KB, hi-res wmv file 1 MB) for the mixing in a one
g environment. Click here (670 KB, hi-res wmv 1.2 MB) for the mixing video in
micro-gravity environment produced by a NASA zero-g aircraft.
Materials:
- Soap bubble kit from
dollar store
- Bubble Gum
- Spherical Balloons
- Video camera
- Eye Dropper
- Dark Grape Juice
Performing
the Live Lesson “The Ultimate Field Trip” in the Classroom:
1) Watch (2.0 MB, hi-res wmv file 4.0 MB) Christa’s effervescent bubbles escape from
their bottle container aboard the zero-g NASA aircraft.
2) Have a student create a stream of bubbles with the bubble kit.
3) Have another student blow up a bubble with bubble gum.
4) Ask the students to compare Christa’s bubble with the soap bubble and
the bubble gum bubble.
5) What is alike about all three of the bubbles? Answer: Each has air, or, a
gas, within them. Each required someone
or something to “blow up” the bubble to force the air inside to form the
spherical bubble shape. Each has a
material to contain or hold the air within the sphere. The balloon has a closed bag made of
rubber. The soap bubble has an enclosed
bag made of soap molecules, and the bubble gum has an enclosed bag made of
gum. All have to deal with the
equilibrium of gas forces on their respective “bags” of soap, rubber, or gum.
6) Next ask what
was is not alike about the bubbles? Answer: The soap bubble and Christa’s bubble have a thin liquid-like surface
held together by “surface-tension” while the balloon and bubble gum have
pliable solid materials providing the containing surface.
Analysis:
Study
of thin films has fascinated scientists for centuries. Related to the topic is the examination of spheres of liquids and
gases under the force of gravity and microgravity. The laws of gravity and buoyancy affect how gases and liquids interact. The interaction helps to explain and
investigate the behavior of viscous and gaseous substances on earth and in
space.
Whether
on land, under the sea, in the air, or in space, instructive experiments
contribute to study, teaching, and understanding physical and scientific
principles of terrestrial or extraterrestrial living. Therefore, examining how a Shuttle zero g
environment influences the forming of a fluid’s geometry is important.
Of
course, such study is readily done in the atmosphere when gravity in
conjunction with air currents is not a factor. But in a closed room, without the influence of gravity or air currents,
an ideal laboratory is present. Only the
variables (forces) contributing directly to forming the geometric object need be
considered. And best of all, the
experimental environment is long lasting, hours, days, and even
Though
Christa’s study of liquid properties in zero g was only planned for 15 minutes,
this is years compared to the limited time available for a single flight of
NASA’s KC-135 zero g aircraft, offering less than 25 seconds exposure to
microgravity.
Since
humankind first ventured into weightless space flights, examination of fluid
behavior has revealed liquids assume a spherical shape in zero gravity. Perhaps, it was the Soviet dog Laika who
first observed the phenomena on Sputnik
II in 1958.
Numerous
video clips exist in NASA’s archives showing the principle Christa hoped to
revisit during her fifteen minute live lesson. Click here (877 KB, hi-res wmv file 2.0 MB) with the ctrl key pressed. Watch an astronaut dispense fluid into his mouth. Note the sphere formed.
Christa’s Unique Contribution
What Christa
might have done beyond previous demonstrations dealt with her ability to
teach. For example, she made the
following comment about helping kids
understand constructing something when weightless.
“Because I think it’s hard for kids to realize that you can build
something that’s not attached to anything, but in zero gravity you can do that,
so that at that point I wanted to let it (space
station model) go.” Christa
personified the idea that a gifted teacher must first be a “teachable”
student. An example of this is her
interview with the manager of the
Wright
Brothers’ Airplane and the International Space Station
In Christa’s
demonstration, she holds up a model of the Wright Brothers’ plane. Their aircraft was a glider with an
engine. Knowing that a wing’s lift is
not needed in zero gravity, Christa might have thrust themodel across the cabin.
Questions to Answer:
1. Compare a scuba diver’s environment to an
astronaut’s aboard the Shuttle. Could
the diver conduct Christa’s orange juice lesson using a colored liquid with
slightly greater density than water? What
would happen?
2. How does NASA use a swimming pool to train
astronauts? How is this like working on board the Shuttle?
3.In the classroom, how would Christa’s
demonstration of the Wright Brothers’ plane and the
4. Do you think that the space station’s
wing-like solar panels are affected by air? If so, what is the effect, and how is it dealt with?
5. Should the space station be “stream-lined”
like a jet aircraft? Why or why not?
What Would Have Happened on Challenger?
This question is best
answered by actually performing the above experiment. In the process, ask these questions:
1. What differences exist on earth, not present
for the Challenger demonstration?
2. Why would Christa’s demonstration of how the
space station is built work better on orbit than in the classroom on earth?
For
added information or copies of the project, contact the project editor Jerry
Woodfill, at ER7, NASA JSC,
The
project is a work of the Automation, Robotics, and Simulation Division of the
