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HARDWARE DEVELOPMENT
TEACHER IN SPACE ACTIVITIES FLIGHT 51-L
Hardware design and
development began at
The
Teacher in Space Project (TISP) involves six activities which will be filmed and photographed during the mission and two
live lessons aired on flight day 6. The
six activities are listed below in the order in which they will be conducted. A
discussion of some of the rationale for the
hardware design follows: [The following
are henceforth identified as the lost six.]
Before
discussing each activity, it is probably appropriate to relate some of the general constraints that applied
to the payload in general. First, it had
to fit within the confines of one mid-deck locker (approximately 17"x14"x22"). It had to pass off-gas tolerance
criteria. This eliminated or restricted
the use of many plastics, metals, adhesives, and liquids. Obviously, it had to be safe and not
interfere with the operations of the Orbiter's systems. Also considered was the flammability of the
materials independently and collectively.
Other
constraints were established by the perceived goals of the project. For instance, it was important that teachers
in the classroom would be able to closely duplicate the equipment and conduct
demonstrations to be used as a comparison of the behavior of phenomena on Earth and on-orbit. It was believed that highly exotic hardware would inhibit the
involvement of some teachers and student groups. The range of age levels had to be considered. The action, interaction, or reaction of
components had to be clear in order to be
filmed and photographed.
Finally, the number
and variety of the activities, plus the
equipment to support the live lessons precluded the possibility for the
education staff to develop viable quantitative science experiments of each
activity in the time allotted to produce the hardware. Therefore, the activities
had to be considered qualitative demonstrations.
Click on link below to go directly to the Lesson Plan:
The goal of the
hydroponics activity was to demonstrate a possible procedure that might be used
on the Space Station and in future space
endeavors to provide nutrient requirements in a closed environment in microgravity. The
objective was to demonstrate the processes related to growing plants in
microgravity.
The lesson
plan called for two white beans to be germinated per day beginning 7 days prior
to launching. One plant from each pair
would have been selected for flight, contained in its own closed hydroponics
system.
Several problems
emerged. White
beans take several days to germinate. They produce large plants quickly after emerging. The absence of good light for plant growth on the Orbiter would have aggravated the latter
problem by causing the plant to be "leggy" or elongated. There would
not be room in the locker to accommodate adequate containers. Mung beans had better characteristics and had
been flown on a previous mission, providing some baseline information. The number of plants was reduced to six due
to payload volume constraints, and it was decided to use three seedlings 2 days
old and three newly germinating seeds to reduce the overall time involvement by ground support staff with this single activity.
Hydroponics
in Space Lesson
Aboard
the Zero-G Aircraft, Christa Applies Misting to Chamber 6 which will hold
a Mung Bean
Another major problem
was that of providing a substrate for the plants that would allow for growth
while keeping the fertilizer fluid where it
belonged. A number of ideas were tested
with the help of volunteers such as Cheryl Barnard, an undergraduate student at
the
Hydroponics Chamber
Another aspect of this
activity is the root misting apparatus in cylinder
number six. This idea was stimulated by
experiments at the
Close
View of Hydroponics Experiment Apparatus
Click on link below to go directly to the Lesson Plan:
The goal of the magnetism activity was to understand the role
of magnetic lines of force in the space environment. The objectives were to photograph and observe
demonstrations of magnetism in space, and to
photograph and observe lines of magnetic force in three dimensions in a
microgravity environment.
A compass
and bar magnet readily procured from a teacher supply store were selected to
demonstrate that magnetism certainly is a force in microgravity. The magnet had to be stripped of its plating
material and nickel plated to make it pass off-gas criteria.
A box made
of aluminum or some other nonferrous material, holding iron filings, and
covered by a transparent top was proposed as a means of demonstrating lines of
magnetic force in two dimensions. It
soon became clear that a sandwich of two lexan plates separated by a
"gasket" of lexan would occupy less volume and be easier to
fabricate. Two tiny holes were drilled
in one plate to preclude problems of pressure differential in case of a contingency
EVA causing the cabin pressure to be lowered. Safety considerations precluded the use of iron filings which might have
been ingested by crewmembers or electronic equipment if accidentally released
into the cabin. Instead, soft iron wire
(baling wire) was cut into lengths 1/8- to 1/4-inch long for use in this and
the other magnetism demonstration. These
wire pieces had to be coated with nickel oxide, soaked in oil, then baked to
prevent rusting. They were also tumbled
with ball bearings 24 hours to remove sharp edges. Some tests were done using #6 steel shot, but thelinear
wire pieces gave the best results.
The original proposal
for demonstrating lines of force in 3-D called for a transparent beach ball with an
electromagnet suspended inside. An exhaustive search for a suitable ball was
futile. Therefore, a cube was
constructed of the same material found covering the drink containers used on
the Shuttle. Tests proved its optical
qualities were acceptable, it was tough, and could be bonded using equipment at
the
The electromagnet
evolved out of much testing of suitable core materials, wire sizes and lengths,
and battery configurations. The final
product consists of 400 feet of copper magnet wire around a 3-1/2 inch soft
iron bolt 1/4-inch in diameter. The resulting magnet is 3/4 inches in diameter. Soft iron does not retain magnetism when the power is turned off. Power is supplied by two "AA" batteries wired to a toggle switch
with built-in LED, and a variable resistor
with a range of 0-250 ohms.
Magnetism Lines of
Force in Space Lesson
Though this electromagnet
is not strong enough to hold the wire pieces
in 1 g, tests on the KC-135 weightless trainer proved its effectiveness in microgravity conditions. A more powerful magnet was
not used to preclude interference with the Orbiter systems.
An additional problem to be
addressed was the introduction of moisture from the breath as the cube was
inflated. The resulting condensation
obscured viewing into the bag and caused rusting on the approximately 4000 wire
pieces inside. Solving the problem
included treating the wire as previously
described and putting a desiccant filter in the inflation tube.
Click on link below to go directly to the Lesson Plan:
The goal of this
activity was to demonstrate the fundamental laws of motion during
weightlessness. The objectives were to
show the principle of inertia in an orbiting spacecraft; to show the
relationship between force, mass, and acceleration; and to show the
action-reaction of two different masses colliding.
To first demonstrate
that objects have no apparent weight .in the
spacecraft was relatively straightforward; an object would be suspended in
midair on a small spring. The spring
would not stretch because the object is in
free-fall around the Earth traveling at the same rate
as the spacecraft. If the end of the
spring were attached to the inside of the craft and a thruster were
fired, it would cause the spring to stretch
due to the spacecraft changing velocity with respect to the object.
Determining how to
demonstrate the objectives was not so
straight-forward. Historically, educators have disagreed on methodology
for treating this
topic.
Add the educated opinion of engineers and technically
oriented support staff to the realities of
the Orbiter environment and the problem became
very complex.
There was discussion
of using objects such as wooden blocks of
different sizes, therefore different mass; except some of the activity called
for objects of the same size, yet 1/2 or 1/4 of the mass of each other. This would
have meant finding materials whose densities
varied with the desired proportions, or mechanically altering (drilling holes)
in one of the objects to achieve the desired effect. The wooden block idea sounded plausible until flammability and off-gassing were considered. Using metal blocks was considered and
dismissed, remembering the criteria of keeping the hardware within the ability of teachers and students to copy as closely as possible. Overall payload
weight (pre-launch) was also considered - metal masses large enough to
be filmed effectively would have been relatively heavy, even using aluminum. Another problem with blocks would have
presented itself when the teacher attempted to use whatever triggering device
was developed to exert a force on the object. If the forces were not exerted precisely through the center of mass of the block, it would tumble and not move as
desired. A sphere would not present this
problem.
The decision to use
spheres created a new challenge: making spheres of common substances acceptable
for flight in a manner available to the
public. The challenge was met by
acquiring a billiard ball, then locating a steel ball bearing whose mass was
almost exactly 1/2 its mass. Conveniently, the diameter ratio of the spheres was almost exactly 1 to
2 also. The ball bearing used was 1-1/8
inches in diameter.
Another problem to
address was the force actuator or trigger
device. Some means had to be provided
for the teacher to apply the same amount of force to
different objects accurately, repeatedly,
without imparting other influences.
Using the retraction mechanism of a ball point pen was
considered. This posed
difficulties. Though the teacher would
be able to exert the force through the
center of mass of the sphere easily, it would prove difficult to aim the pen while holding it next to the ball before
triggering it to send the ball along the
desired path. Remember, this would be
performed while the demonstrator and the ball were free-floating, subject to
air currents set up by the ventilation system.
The resulting actuator
uses the vacuum created by suction on a tube to hold the ball against a
flexible cup. The ball compresses a coil
spring protruding from the center of the
cup. Thus captured, the ball may be aimed accurately so that it will
follow the desired path in front of the cloth metric measure strip
that will be Velcro attached to the 4'x
6' backdrop affixed to the mid-deck locker doors to improve visibility of
objects during filming. Using two
different springs and the vacuum system the teacher can release the spheres at
the same time, using the same force repeatedly.
Ball point pen
retractors or something similar may be
used in 1 g on a billiard ball and ball bearing sitting on a level table or on a V-groove
track to duplicate this activity in the
classroom.
Click on link below to go directly to the Lesson Plan:
The goal of the
effervescence activity was to understand why products may or may not effervesce in a microgravity environment. The object was to show the action of bubbles produced in a microgravity
environment and to observe the lack of buoyancy. The activity originally called for a clear plastic container, open on
top, an effervescent tablet, and a water gun. The teacher would have placed the tablet in the container, then used the
water gun to add water. This scenario
presented several concerns to the safety board and
engineers. Though one of the Skylab
crews demonstrated that water could be squirted .into an open container using
their food re-hydration water gun, they had good control of the forces acting
on the water, i.e., the release of liquids into the cabin. Errant fluids pose a threat to electronic
systems in the Orbiter. The container
would have to be covered. Glass containers were undesirable due to possible
breakage. The search began for transparent
bottles of adequate size, clarity and acceptable material.
A standard drink
container with a tablet sealed inside was tested. Filming the action was difficult, and the
pressure generated by the carbon dioxide gas caused the water to be ejected from
the septum. Some means had to be
developed to accommodate the CO2 and allow for air displacement during filling
in cases in which a hard walled Plexiglas container was considered. Finally, a transparent lexan bottle was
discovered that proved to be the solution to this and other hardware
puzzles. Lexan is tough, transparent,
and flight approved. There would be no concerns about off-gassing or
breakage. Pressure tests proved the
bottles able to maintain a seal to at least 60 psi, and the tablets generated
somewhere in the range of .2 psi.
Modifications on the
bottle include the addition of a Teflon gasket in the lid, and a viton
diaphragm glued over the mouth. The
diaphragm has a slit to accommodate insertion of the effervescent material, and
functions as a barrier for the water while the lid is off. The water in the bottle is colored with blue
food coloring to enhance visibility.
Picture
of Christa inserting the tablet into cap-slot
Photo
is of Christa screwing on lid while tablet effervesces
The last component of
this activity to be discussed is the effervescent tablet. A commonly available tablet will be used,
but it will be crushed and the powder enclosed in water soluble gelatin
capsules that may be purchased at a pharmacy. The capsule is perforated by 60 holes.
Several concerns led
to this arrangement. The first was
safety. It is not as simple to insert an
unprotected tablet through the slit in the diaphragm as one might believe. The small amount of water that will be present
on top of the diaphragm when the lid is removed begins to dissolve the tablet
immediately allowing water to escape, and preventing observation and filming of the object. That portion of the tablet that enters the bottle then reacts quickly so
that observation and study are hindered. It is hoped that the perforated capsule will allow the desired results to be achieved while
slowing down the reaction time of the chemicals.
Click on link below to go directly to the Lesson Plan:
The objectives
of this activity were to demonstrate chromatographic separation of pigments and
capillary action in microgravity. This
activity was originally part of the hydroponics demonstration, thoughin that
case, capillary action and osmosis would have been observedinstead of chromatographic separation. The original plans were changed primarily because of the complexities
they created in thedesign of the hydroponics chamber. Time was a critical factor driving the selection of off-the-shelf
equipment and design, testing, andfabrication
of all the hardware for this project. Thus, a chromatography
activity emerged.
Chromatography in Space
Lesson
Tests with various
inks, papers, and quantities of water
promisedthis to be an easily duplicated
demonstration for the classroom. Place a spot of ink on a piece of
paper, hang the paper on thebulletin board,
add a drop of water, and observe while the waterdissolves
the ink. The water moves against gravity due to capillaryaction, carrying the components of the ink with
it. These componentsare deposited in layers or strata, much like
sediment in a river,according to their molecular mass and the size,
shape, and chargeof their molecules.
The teacher will use
strips of filter paper 1/2"x 3"
long, and aflight approved, water base ink
felt tip pen. The paper will beplaced in a lexan vial
after adding a water drop to begin the process. This prevents evaporation from slowing down and stopping theprocess prematurely.
There are
parallels between the behavior of the ink molecules in this demonstration and
the behavior of the molecules of the chemicals used in the continuous flow
electrophoresis (CFES) used to process pharmaceuticals.
Click on link below to go directly to the Lesson Plan:
The objective of this
activity was for students to understand similarities and differences between
the use of simple machines in space and Earth environments. The question posed was "would certain
simple machines have been developed by people who always lived in microgravity?" Stated another way, “what are the applications in space for simple
machines like the wheel and axle, lever, inclined plane, wedge, and pulley?”
The original plan
called for a wooden inclined plane, a cart with four wheels, hammer and nail,
screw to be screwed into the inclined plane, and a pulley. The commander immediately
vetoed the idea of driving nails into the
wood because of the potential for damage to the Orbiter". A refresher in physics reminds one that the forces input into the hammer-nail-wood system would
ultimately have to be transmitted to either a crewmember or the craft. Since the goal of this particular part of the activity was to use the hammer
to pull the nail, thereby
demonstrating a fulcrum and lever, it was decided to demonstrate the lever using the 18" pry bar in the Orbiter tool kit instead. Also, it was not
desirable to use wood due to flammability. For some time a 4”wide folding aluminum meter measure was considered to serve as an inclined plane and with
the
A pulley will be attached to the mid-deck locker and used to pull a
small car "up" the inclined plane. This demonstrates that the wheels are useless on the car, lacking friction
with the plane, but that the wheel functions well as a pulley to change the
direction of a force. Of course,
multiple pulleys could be used to multiply a force to assist in moving mass in microgravity.
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
