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SHUTTLE SPACE SUIT


N A S A
EDUCATIONAL BRIEFS For The Classroom


Outer space is a hostile environment. In order for astronauts to
survive there, part of the Earth's environment must be carried with
them. Air, pressure, and moderate temperatures have to be contained in
a shell surrounding the space traveler. One method of doing this is to
encase the astronaut in a protective flexible capsule called the space
suit.

Up to now, space suits on space missions from the Mercury Program
through the Apollo/Soyuz Test Project have been effective protection
but have been handicapped by certain design problems. They were
custom-fitted garments and in some suit models, more than 70 different
measurements had to be taken of the astronaut in order to manufacture
the suit to the proper fit. As a result, a space suit could be worn by
only one astronaut on only one mission. Space suits were stiff, and
simple motions such as grasping objects sapped the strength of an
astronaut. Even donning the suit was an exhausting process lasting, at
times, more than an hour and requiring the help of an assistant.

For the Space Shuttle astronauts, a new suit has been developed that
offers many improvements in comfort, convenience, and mobility over
the previous models. The suit, which is worn only outside the Shuttle,
is modular and features many interchangeable parts. Torso, pants,
arms, and gloves comes in several different sizes and can be assembled
for each mission in the proper combinations to suit individual
astronauts. This modular feature makes the Shuttle suit wearable on
more than one mission and results in significant cost savings. Space
Shuttle astronauts wear the suit when leaving the Orbiter cabin to
deploy payloads, repair and service satellites in orbit, and assemble
large structures from parts carried in the Orbiter cargo bay.


                           MAJOR COMPONENTS

The Shuttle suit, known as an EMU for Extravehicular Mobility Unit,
consists of three main parts: liner, pressure vessel, and primary life
support system. These components are supplemented by a drink bag,
communications set, helmet, and visor assembly.

The suit liner is technically called the liquid cooling and vent
garment. It is quite similar in appearance to long underwear with one
important difference. The stretchy, form-fitting nylon Spandex fabric
is laced with small Tygon plastic tubes. The outside layers of the
Shuttle suit are exceptionally well insulated making body heat
dissipation a critical concern. Water cooled in the life support
system circulates around the body it encloses through the plastic
tubes for temperature control. Openings in the fabric weave also
permit ventilation of the body.

The liquid cooling and vent garment is the first major suit component
donned by the astronaut. It is followed by the pressure vessel, a
multilayered garment. Actually, only one of the layers contains the
pressure. The remainder are comprised of alternating layers of
aluminized mylar plastic and unwoven Dacron that insulate the suit
from the Sun-to-shade temperature extremes of 148 degrees to minus 129
degrees in outer space. On top of those layers is a single outside
layer of though Ortho fabric, a combination of Teflon, Kevlar, and
Nomex with a neoprene liner, that serves as an abrasion and tear
resistant cover as well as the primary micrometeoroid shield.

The principal function of the pressure vessel is the containment of
oxygen under pressure to make a livable atmosphere for the astronaut.
One layer of Kevlar, lined with a polyurethane plastic bladder and
Dacron shell, contains the oxygen at a pressure of 281.24 grams per
square centimeter (4 psi). With a normal atmospheric mixture of
gasses, this pressure would be hardly livable. However, pure oxygen of
the suit atmosphere makes the pressure acceptable.

One of the major challenges in designing space suits has been to make
the pressure vessel flexible. With inside pressure, the vessel
inflates balloon-like and becomes stiff. On previous models, joint
areas such as the shoulders were made of molded neoprene rubber and
reinforced with cables. These joints required constant muscle exertion
to hold them in a flexed position. The pressure vessel fabric however,
permits tucks to be stitched in the shoulder, elbow, wrist, knee, and
ankle area. The tucks allow the joints to retain a flexed shape
without constant muscle exertion.

The final major component of the Shuttle suit is the PLSS or Primary
Life Support System. It is a two-part system consisting of a backpack
unit and a control and display unit on the suit's chest. The PLSS is
relatively heavy and the attachments of similar systems on Apollo
suits was an arduous process. To simplify the Shuttle suit, a
fiberglass shell, called the Hard Upper Torso or HUT, is built inside
the upper torso of the pressure vessel. The HUT is similar in
appearance to the breastplate of a suit of armor. The PLSS is
permanently mounted to the HUT and all necessary connections are made
through the suit's upper layers.

The backpack portion of the PLSS supplies oxygen for breathing, suit
pressurization, and ventilation. It also cools and circulates the
water used in the liquid cooling and vent garment and controls the
oxygen temperature. Still another function of the PLSS is the cleaning
of carbon dioxide and odors as well as other contaminants from the
suit's atmosphere. Depending upon the exertion of the astronaut
wearing the suit, there is a seven-hour oxygen supply in the backpack
with an extra half-hour emergency supply.

The front of the PLSS is a control and display unit. A microprocessor
automatically provides startup instructions, checks out the suit's
major functions, and warns the wearer of malfunctions. The
microprocessor is literally a computer on a tiny circuit chip.


                        WASTE CONTAINMENT SYSTEM

Containment of body wastes is a significant problem in space suit
design. As previously discussed, the PLSS will handle odors, carbon
dioxide, and contaminant gasses in the suit's atmosphere. A separate
system is required for urine relief. Because the Space Shuttle carries
both male and female crewmembers, two different systems have been
designed. Both systems are capable of containing approximately 900
milliliters of urine. Due to the short time durations of anticipated
space suit activity, fecal containment is considered unnecessary.


                           MINOR COMPONENTS

The final items in assembling the Shuttle suit for use are the helmet
and visor assembly. The helmet is a rigid, one-piece hemisphere of
ultraviolet polycarbonate plastic. Donning the helmet automatically
aligns the upper torso and helmet portions of the suit ventilation
system. On top of the helmet is placed a visor assembly that consists
of a visor with thermal/optical coatings, and center and side shades.
This assembly provides impact, visible light, and thermal protection
to the head region.

Prior to fixing the helmet in place, a "Snoopy-type" skull cap with
microphone and earphones for communications is placed on the head. A
radio in the PLSS relays crew voice transmissions as well as telemetry
from sensors that monitor the physiological condition of the
astronaut.

One other item is fixed in place prior to attaching the helmet. A
small in-suit drink bag is filled with 950 ml of water from the
Orbiter's portable water supply and placed inside the neck area of the
upper torso's HUT. A drink tube with a suction-actuated valve permits
occasional refreshment during EVA.


                        DONNING THE SPACE SUIT

To make ready for work outside the Space Shuttle, the astronaut enters
an airlock that exists into the Orbiter cargo bay. Here the crewmember
puts on the appropriate urine collection system and the liquid cooling
and vent garment. To simplify putting on the outer layers, the upper
torso of the pressure vessel and PLSS are mounted to one of the
airlock walls. The crew member pulls on the pants and then "dives" up
into the upper torso. The pants and upper torso are easily joined by a
metal ring connector at the waist. After the life support system is
actuated and all connections are made, the communications cap, helmet,
visor assembly, and gloves are attached. The entire process can be
completed without assistance and the crew member can be ready for work
in just minutes.


----------------------------------------------------------------------

QUESTIONS AND ACTIVITIES FOR THE CLASSROOM

1.   What are the advantages of the Shuttle suit over previous
     space suit models?

2.   What makes it possible for the crewmember to survive in low
     pressure atmosphere of the Shuttle suit?

3.   What is one of the most challenging aspects in designing a space
     suit? Why?

4.   What are the main components of the Shuttle suit? What are their
     functions?

5.   Compare the environmental functions of space suits, space
     capsules, and the Earth.

6.   Research the history of space suit design from the early high-
     altitude pressure suits to the new Shuttle suit.

7.   Illustrate the need for tucked joints in the Shuttle suit
     pressure vessel by inflating a long toy balloon. Bend the balloon
     in the middle and note the need to constantly exert force to
     retain the new shape.

8.   Investigate the insulative properties of a variety of materials
     such as aluminum foil, mylar plastic, and cloth. Form small
     pouches from these materials and insert the bulb end of a
     thermometer. Use a strong light bulb to radiate the pouch and
     note the temperature changes over a unit of time. Also evaluate
     the materials for tear and puncture resistance and flexibility.

9.   Research the minimum environmental parameters required for human
     survival in outer space.

10.  Challenge the students to design an experiment that measures the
     oxygen requirements of a "typical" astronaut during rest, and
     light and strenuous exertion.

----------------------------------------------------------------------
NASA EDUCATIONAL BRIEFS For The Classroom, Shuttle Space Suit, EB-81-2


"6_2_8_3.TXT" (131921 bytes) was created on 11-30-92

Suited for Spacewalking
Teacher's Guide With Activities

EP-279
March 1992

Note: a complete copy of this activity guide with illustrations can be obtained
from NASA Teacher Resource Rooms. Refer to the appropriate menu in SPACELINK
for addresses and telephone numbers.





Acknowledgements

Writer
Gregory L. Vogt, Ed.D.
Crew Educational Affairs Liaison
NASA Johnson Space Center

Managing Editor
Cheryl A. Manning
Education Division
NASA Headquarters

This publication was produced in a cooperative effort of the National
Aeronautics and Space Administration and the Challenger Center for Space
Science Education. The following individuals and organizations provided support
and guidance in the development of its contents.

NASA Headquarters
Washington, DC
Education Division
Elementary and Secondary Branch
Technology and Evaluation Branch
Educational Publications Branch

NASA Johnson Space Center
Houston, Texas
Space Shuttle Support Office
Astronaut Office

Challenger Center for Space Science Education
Alexandria, Virginia

Oklahoma State University
Stillwater, Oklahoma
Aerospace Education Services Program

Special thanks also go to the following individuals for their assistance.

James W. McBarron
Chief, EVA Branch
Crew and Thermal Systems Division
NASA Johnson Space Center

Joseph J. Kosmo
Subsystems Manager for Spacesuit Development
Crew and Thermal Systems Division
NASA Johnson Space Center

Charles E. Whitsett
Manager for Projects
Automation and Robotics Division
NASA Johnson Space Center

Shirley Sirota Rosenberg
Consulting Editor
SSR, Incorporated

Sam Haltom
Cover Designer
Another Color, Inc.

Marco G. Zambetti
Animator
McDonnell Douglas Space Systems Company

Table of Contents



Acknowledgments ii
Introduction                                     1
EARTH AND SPACE                                  2
The Outer Space Environment                      3
Spacewalking History                             4
The Space Shuttle EMU                            8
Putting on the EMU                              11
Working In Space                                19
Manned Maneuvering Unit                         19
Future Spacesuits                               22
EVA                                             23
CLASSROOM ACTIVITIES                            25
   Unit 1  Investigating the Space Environment  26
   Unit 2  Dressing for Spacewalking            35
   Unit 3  Moving and Working In Space          48
   Unit 4  Exploring the Surface of Mars        54

Introduction

Spacewalking has captured the imagination of generations of children and adults
since science-fiction authors first placed their characters on the Moon. But
true space- walking did not actually begin until the mid-1960s with the
exploits of Alexei A. Leonov in the Soviet Union and Edward H. White II in the
United States. Since those first tentative probings outside a space capsule,
astronauts and cosmonauts have logged thousands of hours on extravehicular
activities, and some have even walked on the surface of the Moon. The stories
of their missions in space are fascinating, but just as interesting is the
spacesuit technology that made it possible for them to "walk" in space.

        This publication is an activity guide for teachers interested in using
the intense interest many children have in space exploration as a launching
point for exciting hands- on learning opportunities.  The guide begins with
brief discussions of the space environment, the history of spacewalking, the
Space Shuttle spacesuit, and working in space.  These are followed by a series
of activities that enable children to explore the space environment as well as
the science and technology behind the functions of spacesuits.  The activities
are not rated for specific grade levels because they can be adapted for
students of many ages.  The chart on curriculum application at the back of the
book is designed to help teachers incorporate activities into various subject
areas.

Measurement

This activity guide makes exclusive use of the metric system for measurement.
If English-system equivalents are desired, a table of conversion factors can be
found in many dictionaries and science textbooks.  The metric unit for pressure
may be unfamiliar to readers, and an English-system conversion factor for this
unit may not appear in some tables.  The metric unit for pressure is the
pascal.  A pascal is equal to a force of one newton exerted over an area of one
square meter.  Because the pascal is a relatively small unit, the more
convenient unit of kilopascal (1,000 pascals) is used here instead.  To convert
kilopascals to the English-system unit of pounds per square inch, divide by
6.895.


 Earth and Space

 If we loosely define an astronaut as someone who travels through space, then
everyone is an astronaut.  Even though we may be standing still on the surface
of Earth, we are actually traveling through space.  Indeed, our planet may be
thought of as a spaceship on a never- ending voyage.  As "astronauts" traveling
through space on the surface of Earth, we take for granted the complex
environment that sustains life.  Earth's gravitational attraction holds a dense
atmosphere of nitrogen, oxygen, carbon dioxide, and water vapor in a thick
envelope surrounding Earth's entire surface.  The weight of this atmosphere
exerts pressure, and its movements distribute heat from the Sun to balance
global temperatures.  Its density filters out harmful radiations and
disintegrates all but the largest meteoroids.  Earth's atmosphere is a shell
that protects and sustains the life forms that have evolved on its surface.
Without the atmosphere's protection, life as presently known would not be
possible.

        When Earth astronauts leave the surface of their planet and travel into
space, they must carry some of their environment with them.  It must be
contained in a physical shell because their body masses are too small to hold
it in place by gravitational attraction alone.  The shell that is used is
called a spacecraft--a rigid collection of metal, glass, and plastic.  Though
far simpler in function than Earth's, a spacecraft's environment serves well
for short missions lasting a few days or weeks.  On some flights, the shell is
deliberately opened and the astronauts pass through an airlock to venture
outside.  When doing so, they must still be protected by a smaller and very
specialized version of their spacecraft called the Extravehicular Mobility Unit
(EMU).  This smaller spacecraft is composed of a spacesuit with a life-support
system.  It differs from the first spacecraft, or mother ship, in its
anthropomorphic (human) shape and its flexibility.  Astronauts wearing EMUs
need to be able to move arms, hands, and legs to perform an array of tasks in
space.  They must be able to operate many types of scientific apparatus,
collect samples, take pictures, assemble equipment and structures, pilot
themselves about, and repair and service defective or worn-out satellites and
other space hardware.  The tasks of astronauts outside their mother ship are
called extravehicular activities, or EVAs.

The Outer Space Environment

Outer space is just what its name implies.  It is the space that surrounds the
uppermost reaches of the atmosphere of Earth and all other objects in the
universe.  Although it is a void, outer space may be thought of as an
environment.  Radiation and objects pass through it freely.  An unprotected
human or other living being placed in the outer space environment would perish
in a few brief, agonizing moments.

        The principal environmental characteristic of outer space is the
vacuum, or nearly total absence of gas molecules.  The gravitational attraction
of large bodies in space, such as planets and stars, pulls gas molecules close
to their surfaces, leaving the space between virtually empty.  Some stray gas
molecules are found between these bodies, but their density is so low that they
can be thought of as practically nonexistent.

        On Earth, the atmosphere exerts pressure in all directions.  At sea
level, that pressure is 101 kilopascals.  In space, the pressure is nearly
zero.  With virtually no pressure from the outside, air inside an unprotected
human's lungs would immediately rush out in the vacuum of space; dissolved
gases in body fluids would expand, pushing solids and liquids apart.  The skin
would expand much like an inflating balloon.  Bubbles would form in the
bloodstream and render blood ineffective as a transporter of oxygen and
nutrients to the body's cells.  Furthermore, the sudden absence of external
pressure balancing the internal pressure of body fluids and gases would rupture
fragile tissues such as eardrums and capillaries.  The net effect on the body
would be swelling, tissue damage, and a deprivation of oxygen to the brain that
would result in unconsciousness in less than 15 seconds.

        The temperature range found in outer space provides a second major
obstacle for humans.  The sunlit side of objects in space at Earth's distance
from the Sun can climb to over 120 degrees Celsius while the shaded side can
plummet to lower than minus 100 degrees Celsius. Maintaining a comfortable
temperature range becomes a significant problem.

        Other environmental factors encountered in outer space include
weightlessness, radiation of electrically charged particles from the Sun,
ultraviolet radiation, and meteoroids.  Meteoroids are very small bits of rock
and metal left over from the formation of the solar system and from the
collisions of comets and asteroids.  Though usually small in mass, these
particles travel at very high velocities and can easily penetrate human skin
and thin metal.  Equally dangerous is debris from previous space missions.  A
tiny paint chip, traveling at thousands of kilometers per hour, can do
substantial damage.

Spacewalking History

The Extravehicular Mobility Unit worn during spacewalks by NASA's Space Shuttle
astronauts represents more than 50 years of development and testing of pressure
suits in the U.S., France, Italy, Germany, and other countries.  It all began
with high-altitude flyers, and one of the first was an American, Wiley Post.
Post was an aviation pioneer of the 1930s who was seeking to break
high-altitude and speed records.  Post, as well as others, knew that protection
against low pressure was essential.  Through experience, aviators had learned
that Earth's atmosphere thins out with altitude.

        At 5,500 meters, air is only one-half as dense as it is at sea level.
At 12,200 meters, the pressure is so low and the amount of oxygen present is so
small that most living things perish.  For Wiley Post to achieve the altitude
records he sought, he needed protection. (Pressurized aircraft cabins had not
yet been developed.) Post's solution was a suit that could be pressurized by
his airplane engine's supercharger.

        First attempts at building a pressure suit failed, since the suit
became rigid and immobile when pressurized.  Post discovered he couldn't move
inside the inflated suit, much less work airplane controls.  A later version
succeeded with the suit constructed already in a sitting position.  This
allowed Post to place his hands on the airplane controls and his feet on the
rudder bars.  Moving his arms and legs was difficult, but not impossible.  To
provide visibility, a viewing port was part of the rigid helmet placed over
Post's head.  The port was small, but a larger one was unnecessary because Post
had only one good eye!

        During the next 30 years, pressure suits evolved in many ways, and
technical manufacturing help was gained from companies that made armor, diving
suits, galoshes, and even girdles and corsets.  Designers learned in their
search for the perfect suit that it wasn't necessary to provide full sea-level
pressure.  A suit pressure of 24.13 kilopascals would suffice quite nicely if
the wearer breathed pure oxygen.  Supplying pure oxygen at this low pressure
actually provides the breather with more oxygen than an unsuited person
breathes at sea level. (Only one-fifth of the air at sea level is oxygen.)

        Various techniques were used for constructing pressure garments.  Some
approaches employed a rigid layer with special joints of rings or cables or
some other device to permit limb movements.  Others used nonstretch
fabrics--laced up corset fashion.

        With the advent of pressurized aircraft cabins, comfort and mobility in
the suit when it was unpressurized became prime objectives in suit design.  The
suit could then be inflated in the event that the aircraft cabin lost pressure.

        By the time NASA began the Mercury manned space flight program, the
best full- pressure suit design consisted of an inner gas-bladder layer of
neoprene-coated fabric and an outer restraint layer of aluminized nylon.  The
first layer retained pure oxygen at 34.5 kilopascals; the second layer
prevented the first from expanding like a balloon.  This second fabric
restraint layer directed the oxygen pressure inward on the astronaut.  The
limbs of the suit did not bend in a hinge fashion as do human arms and legs.
Instead, the fabric arms and legs bent in a gentle curve, which restricted
movement.  When the astronaut moved one of his arms, the bending creased or
folded the fabric inward near the joints, decreasing the volume of the suit and
increasing its total pressure slightly.  Fortunately for the comfort of the
Mercury astronauts, the Mercury suit was designed to serve only as a pressure
backup if the spacecraft cabin decompressed.  No Mercury capsule ever lost
pressure during a mission, and the suits remained uninflated.

        The six flights of the Mercury series were followed by ten flights in
the Gemini program.  Suit designers were faced with new problems.  Not only
would a Gemini suit have to serve as a pressure backup to the spacecraft cabin,
but also as an escape suit if ejection seats had to be fired for an aborted
launch and as an EMU for extravehicular activity.  To increase mobility and
comfort of the suit for long-term wear, designers departed from the Mercury
suit concept.  Instead of fabric joints, they chose a construction that
employed a bladder restrained by a net.  The bladder was an anthropomorphically
shaped layer of neoprene-coated nylon.  That was covered in turn with a layer
of Teflon-coated nylon netting.  The netting, slightly smaller than the
pressure bladder, limited inflation of the bladder and retained the pressure
load in much the same way automobile tires retained the load in inner tubes in
the days before tubeless tires.  The new spacesuit featured improved mobility
in the shoulders and arms and was more comfortable when worn unpressurized
during space flights lasting as long as 14 days.

        The first Gemini astronaut to leave his vehicle ("go EVA") was Ed
White. White exited from the Gemini 4 space capsule on June 3, 1965--just a few
months after Leonov made the first Soviet spacewalk.  For a half hour White
tumbled and rolled in space, connected to the capsule only by an oxygen-feed
hose that served secondary functions as a tether line and a communication link
with the capsule.  Although the term "spacewalk" was coined for the Gemini
program, no actual walking was involved.  On his spacewalk, White used a small
hand-held propulsion gun for maneuvering in space.  When he pulled a trigger,
the gun released jets of nitrogen that propelled him in the opposite direction.
It was the first personal maneuvering unit used in space.

        Upon completion of the Gemini program, NASA astronauts had logged
nearly 12 additional hours of EVA experience.  Approximately one-half of that
time was spent merely standing up through the open hatch.

        One of the most important lessons learned during the Gemini program was
that EVAs were not as simple as they looked.  Moving around in space required a
great deal of work.  The work could be lessened, however, by extensive training
on Earth. The most effective training took place underwater.  Wearing specially
weighted spacesuits while in a deep tank of water gave later Gemini crewmembers
adequate practice in maneuvers they would soon perform in space.  It was also
learned that a better method of cooling the astronaut was required.  The gas
cooling- system could not remove heat and moisture as rapidly as the astronaut
produced them, and the inside of the helmet visor quickly fogged over, making
it difficult to see.

        Following Gemini, the Apollo program added a new dimension in spacesuit
design because actual spacewalks (on the surface of the Moon) were now to occur
for the first time.  As with Mercury and Gemini space garments, Apollo suits
had to serve as a backup pressure system to the space capsule.  Besides
allowing flexibility in the shoulder and arm areas, they also had to permit
movements of the legs and waist.  Astronauts needed to be able to bend and
stoop to pick up samples on the Moon. Suits had to function both in
weightlessness and in the one-sixth gravity of the Moon's surface.
Furthermore, when walking on the Moon, Apollo astronauts needed the flexibility
to roam freely without dragging a cumbersome combination oxygen line and
tether.  A self-contained portable life-support system was needed.

        The Apollo spacesuit began with a garment that used water as a coolant.
The garment, similar to long johns but laced with a network of thin-walled
plastic tubing, circulated cooling water around the astronaut to prevent
overheating.  On top of this layer was the pressure garment assembly.  The
innermost layer of this assembly was a comfort layer of lightweight nylon with
fabric ventilation ducts.  This was followed by a multilayered outer suit.  The
innermost layer of this garment was a neoprene-coated nylon bladder surrounded
by a nylon restraint layer.  Improved mobility was achieved by bellows-like
joints of formed rubber with built- in restraint cables at the waist, elbows,
shoulders, wrist, knees, and ankles.  Next followed five layers of aluminized
Mylar for heat protection, mixed with four spacing layers of nonwoven Dacron.
Outside of that were two layers of Kapton and beta marquisette for additional
thermal protection, and these were covered with a nonflammable and
abrasion-protective layer of Teflon-coated filament beta cloth.  The outermost
layer of the suit was white Teflon cloth.  The last two layers were flame
resistant.  In total, the suit layers provided pressure, served as a protection
against heat and cold, and protected the wearer against micrometeoroid impacts
and the wear and tear of walking on the Moon.

        Capping off the suit was a communications headset and a clear
polycarbonate-plastic pressure helmet.  Slipped over the top of the helmet was
an assembly consisting of sun-filtering visors and adjustable blinders for
sunlight protection.  The final items of the Apollo spacesuit were custom-sized
gloves with molded silicone-rubber fingertips that provided some degree of
fingertip sensitivity in handling equipment, lunar protective boots, and a
portable life-support system.

        The life-support system, a backpack unit, provided oxygen for breathing
and pressurization, water for cooling, and radio communications for lunar
surface excursions lasting up to eight hours.  Furthermore, back inside the
lunar lander the life-support system could be recharged for additional Moon
walks.

        During the Apollo program, 12 astronauts spent a total of 161 hours of
EVA on the Moon's surface.  An additional four hours of EVA were spent in
weightlessness while the astronauts were in transit from the Moon to Earth.
During those four hours, a single astronaut, the command module pilot, left the
capsule to retrieve photographic film.  There was no need for the portable
life-support system away from the Moon, as those astronauts were connected to
the spacecraft by umbilical tether lines supplying them with oxygen.

        NASA's next experience with EVAs came during the Skylab program and
convincingly demonstrated the need for astronauts on a spacecraft.
Space-suited Skylab astronauts literally saved the Skylab program.

        Skylab was NASA's first space station.  It was launched in 1973, six
months after the last Apollo Moon landing.  Trouble developed during the launch
when a micrometeoroid shield ripped away from the station's outer surface.
This mishap triggered the premature deployment of two of the six solar panels,
resulting in one being ripped away by atmospheric friction.  The second was
jammed in a partially opened position by a piece of bent metal.  In orbit,
Skylab received insufficient electrical power from the remaining solar panels:
the station was overheating because of the missing shield.  Instead of
scrapping the mission, NASA assigned the first three- astronaut crew the task
of repairing the crippled station.  While still on board the Apollo command
module, Paul Weitz unsuccessfully attempted to free the jammed solar panel as
he extended himself through the open side hatch.  On board Skylab, the crew
poked an umbrella-like portable heat shield through the scientific airlock to
cover the area where the original shield was torn away.  Later, on an EVA, the
metal holding the jammed solar arrays was cut, and the panel was freed to open.
During an EVA by the second Skylab crew, an additional portable heat shield was
erected over the first.

        The Skylab EMU was a simplified version of the Apollo Moon suits.
There was no need for the portable life-support system, because the crewmember
was attached to the station by an umbilical tether that supplied oxygen and
cooling water.  An astronaut life-support assembly, consisting of a
pressure-control unit and an attachment for the tether, was worn on the chest,
and an emergency oxygen package containing two supply bottles was attached to
the right upper leg.  A simplified visor assembly was used over the pressure
helmet.  Lunar protective boots were not needed.  Skylab astronauts logged 17.5
hours of planned EVA for film and experiment retrieval and 65 hours of
unplanned EVA for station repairs.

The Space Shuttle EMU

The Space Shuttle has opened an entirely new era in space travel.  Launched as
a rocket, the Shuttle operates in space as a spacecraft and returns to Earth as
an airplane.  Both the orbiter and its solid rocket boosters are reusable.
Only the external tank is expended and replaced after each mission.  The
orbiter's payload bay, 18.3 meters long and 4.6 meters in diameter, with its
remote manipulator system (RMS), or mechanical arm, makes the Shuttle a
versatile space transportation system.

        A new EMU enhances the Shuttle's overall capabilities.  Like the
spacecraft itself, the new Shuttle EMU is reusable.  The spacesuits used in
previous manned space flight programs were custom built to each astronaut's
body size.  In the Apollo program, for example, each astronaut had three custom
suits--one for flight, one for training, and one for flight backup.  Shuttle
suits, however, are tailored from a stock of standard-size parts to fit
astronauts with a wide range of measurements.

        In constructing the new Shuttle spacesuit, developers were able to
concentrate all their designs toward a single function--going EVA. Suits from
earlier manned space flight programs had to serve multiple functions.  They had
to provide backup pressure in case of cabin pressure failure and protection if
ejection became necessary during launch (Gemini missions).  They also had to
provide an environment for EVA in weightlessness and while walking on the Moon
(Apollo missions).  Suits were worn during liftoff and reentry and had to be
comfortable under the high-g forces experienced during acceleration and
deceleration.  Shuttle suits are worn only when it is time to venture outside
the orbiter cabin.  At other times, crewmembers wear comfortable shirts and
slacks, or coveralls.

Many Layers

The Shuttle EMU has 12 layers to protect astronauts on EVAs. The two inner
layers comprise the liquid-cooling-and-ventilation garment.  It is made of
spandex fabric and plastic tubing.  Next comes the pressure bladder layer of
urethane-coated nylon and fabric layer of pressure-restraining Dacron. This is
followed by a seven-layer thermal micrometeoroid garment of aluminized Mylar,
laminated with Dacron scrim topped with a single-layer fabric combination of
Gortex, Kevlar, and Nomex materials.

Shuttle EMU End Items

The Shuttle EMU consists of 19 separate items.  Fully assembled, the Shuttle
EMU becomes a nearly complete short-term spacecraft for one person.  It
provides pressure, thermal and micrometeoroid protection, oxygen, cooling
water, drinking water, food, waste collection, (including carbon dioxide
removal), electrical power, and communications.  The EMU lacks only maneuvering
capability, but this capability can be added by fitting a gas-jet- propelled
Manned Maneuvering Unit (MMU) over the EMU's primary life-support system.  On
Earth, the suit and all its parts, fully assembled but without the MMU, weighs
about 113 kilograms.  Orbiting above Earth it has no weight at all.  It does,
however, retain its mass in space, which is felt as resistance to a change in
motion.

1.  Primary Life-Support System (PLSS)

A self-contained backpack unit containing an oxygen supply, carbon-dioxide-
removal equipment, caution and warning system, electrical power, water-cooling
equipment, ventilating fan, machinery, and radio.

2.  Displays and Control Module (DCM)

Chest-mounted control module containing all controls, a digital display, and
the external liquid, gas, and electrical interfaces.  The DCM also has the
primary purge valve for use with the Secondary Oxygen Pack.

3.  EMU Electrical Harness (EEH)

A harness worn inside the suit to provide bioinstrumentation and communications
connections to the PLSS.

4.  Secondary Oxygen Pack (SOP)

Two oxygen tanks with a 30-minute emergency supply, valve, and regulators.  The
SOP is attached to the base of the PLSS. The SOP can be removed from the PLSS
for ease of maintenance.

5.  Service and Cooling Umbilical (SCU)

Connects the orbiter airlock support system to the EMU to support the astronaut
before EVA and to provide in-orbit recharge capability for the PLSS. The SCU
contains lines for power, communications, oxygen and water recharge, and water
drainage.  The SCU conserves PLSS consumables during EVA preparation.

6.  Battery

Supplies electrical power for the EMU during EVA. The battery is rechargeable
in orbit.

7.  Contaminant Control Cartridge (CCC)

Cleanses suit atmosphere of contaminants with an integrated system of lithium
hydroxide, activated charcoal, and a filter contained in one unit.  The CCC is
replaceable in orbit.

8.  Hard Upper Torso (HUT)

Upper torso of the suit, composed of a hard fiberglass shell.  It provides
structural support for mounting the PLSS, DCM, arms, helmet, In-Suit Drink Bag,
EEH, and the upper half of the waist closure.  The HUT also has provisions for
mounting a mini-workstation tool carrier.

9.  Lower Torso

Spacesuit pants, boots, and the lower half of the closure at the waist.  The
lower torso also has a waist bearing for body rotation and mobility, and
brackets for attaching a safety tether.

10.  Arms (left and right)

Shoulder joint and armscye (shoulder) bearing, upper arm bearings, elbow joint,
and glove- attaching closure.

11.  EVA Gloves (left and right)

Wrist bearing and disconnect, wrist joint, and fingers.  One glove has a
wristwatch sewn onto the outer layer.  The gloves have tethers for restraining
small tools and equipment.  Generally, crewmembers also wear thin fabric
comfort gloves with knitted wristlets under the EVA gloves.

12.  Helmet

Plastic pressure bubble with neck disconnect ring and ventilation distribution
pad.  The helmet has a backup purge valve for use with the secondary oxygen
pack to remove expired carbon dioxide.

13.  Liquid Cooling-and-Ventilation Garment (LCVG)

Long underwear-like garment worn inside the pressure layer.  It has liquid
cooling tubes, gas ventilation ducting, and multiple water and gas connectors
for attachment to the PLSS via the HUT.

14.  Urine Collection Device (UCD)

Urine collection device for male crewmembers consisting of a roll-on cuff and
storage bag.  The UCD is discarded after use.

15.  Disposable Absorption and Containment Trunk (DACT)

Urine-collection garment for female crewmembers consisting of a pair of shorts
constructed from five layers of chemically treated absorbent nonwoven fibrous
materials.  The DACT is discarded after use.

16.  Extravehicular Visor Assembly (EVA)

Assembly containing a metallic-gold-covered Sun-filtering visor, a clear
thermal impact- protective visor, and adjustable blinders that attach over the
helmet.  In addition, four small "head lamps" are mounted on the assembly; a TV
camera-transmitter may also be added.

17.  In-Suit Drink Bag (IDB)

Plastic water-filled pouch mounted inside the HUT. A tube projecting into the
helmet works like a straw.

18.  Communications Carrier Assembly (CCA)

Fabric cap with built-in earphones and a microphone for use with the EMU radio.

19.  Airlock Adapter Plate (AAP)

Fixture for mounting and storing the EMU inside the airlock and for use as an
aid in donning the suit.


Putting On the EMU

Putting on a Shuttle EMU is a relatively simple operation that can be
accomplished in a matter of about 15 minutes.  However, the actual process of
preparing to go EVA takes much longer.  When working in the Shuttle cabin,
crewmembers breathe a normal atmospheric mix of nitrogen and oxygen at 101
kilopascals.  The suit's atmosphere is pure oxygen at 29.6 kilopascals.  A
rapid drop from the cabin pressure to the EMU pressure could result in a
debilitating ailment that underwater divers sometimes experience--the bends.
The bends, also known as caisson disease, are produced by the formation and
expansion of nitrogen gas bubbles in the bloodstream when a person breathing a
normal air mixture at sea-level pressure is exposed to a rapid drop in external
pressure.  The bends are characterized by severe pains in the joints, cramps,
paralysis, and eventual death if not treated by gradual recompression.  To
prevent an occurrence of the bends, crewmembers intending to go EVA spend a
period of time prebreathing pure oxygen.  During that time, nitrogen gas in the
bloodstream is replaced by pure oxygen.

        Prebreathing begins when the crewmembers who plan to go EVA don the
special launch and entry helmets.  For one hour they are attached to the
orbiter's oxygen supply system and breathe pure oxygen.  With a long feeder
hose, they can go about their business and initiate the next phase of
prebreathing.

        The atmospheric pressure of the entire orbiter cabin is depressed from
the normal 101 kilopascals to 70.3 pascals while the percentage of oxygen is
slightly increased.  This step must take place at least 24 hours before the
exit into space.  By now, much of the dissolved nitrogen gas has been cleared
from the EVA crewmembers, and they can remove their helmets.  Later, when they
don their spacesuits and seal the helmets, an additional 30 to 40 minutes of
pure oxygen prebreathing takes place before the suits are lowered to their
operating pressure of 29.6 kilopascals.

        Most of the EMU-donning process takes place inside the airlock.  The
airlock is a cylindrical chamber located on the orbiter's mid-deck.  One hatch
leads from the middeck into the airlock, and a second hatch leads from the
airlock out to the unpressurized payload bay.

        Before entering the hatch, but following their initial prebreathing,
the crewmembers put on the Urine Collection Device or Disposable Absorption and
Containment Trunk. The urine collector for males is simply an adaptation of a
device used by people who have kidney problems.  It is a pouch with a roll-on
connector cuff that can contain approximately one quart of liquid.  The device
for females consists of multilayered shorts that hold a highly absorptive
powder.  This system is also capable of containing about one quart of liquid.

        Next comes the Liquid Cooling- and-Ventilation Garment. The LCVG has
the general appearance of long underwear.  It is a one-piece suit with a
zippered front, made of stretchable spandex fabric laced with 91.5 meters of
plastic tubing.  When the EMU is completely assembled, cooling and ventilation
become significant problems.  Body heat, contaminant gases, and
perspiration--all waste products--are contained by the insulation and pressure
layers of the suit and must be removed.  Cooling of the crewmember is
accomplished by circulating chilled water through the tubes.  Chilling the
water is one of the functions of the Primary Life- Support System. The PLSS
device for water cooling and the tubing system are designed to provide cooling
for physical activity that generates up to 2 million joules of body heat per
hour, a rate that is considered "extremely vigorous." (Approximately 160 joules
are released by burning a piece of newsprint one centimeter square.) Ducting
attached to the LCVG ventilates the suit by drawing ventilating oxygen and
expired carbon dioxide from the suit's atmosphere into the PLSS for
purification and recirculation.  Body perspiration is also drawn away from the
suit by the venting system.  These ducts meet at a circular junction on the
back of the LCVG after running along each arm and leg.  Purified oxygen from
the PLSS reenters the suit through another duct, mounted in the back of the
helmet, that directs the flow over the astronaut's face to complete the
circuit.

        The EMU electrical harness is attached to the HUT and provides
biomedical and communications hookups with the PLSS. The biomedical hookup
monitors the heart rate of the crewmembers, and this information is radioed via
a link with the orbiter to Mission Control on Earth. When the orbiter is over
ground tracking station, voice communications are also carried on this circuit.

        Next, several simple tasks are performed.  Antifog compound is rubbed
on the inside of the helmet.  A wrist mirror and a small spiral-bound 27-page
checklist are put on the left arm of the upper torso.  The wrist mirror was
added to the suit because some of the knobs on the front of the displays and
control module are out of the vision range of the crewmember.  The mirror
permits the knob settings to be read. (Setting numbers are written backwards
for ease of reading in the mirror.)

        Another task at this time is to insert a food bar and a water-filled
In-Suit Drink Bag inside the front of the HUT. The food bar of compressed
fruit, grain, and nuts is wrapped in edible rice paper, and its upper end
extends into the helmet area near the crewmember's mouth.  When hungry, the
crewmember bites the bar and pulls it upward before breaking off a piece to
chew.  In that manner, a small piece of the bar remains extended into the
helmet for the next bite.  It is necessary to eat the entire bar at one time,
because saliva quickly softens the protruding food bar, making it mushy and
impossible to break off.  The IDB is placed just above the bar.  The bag is
filled with up to 0.65 liters of water from the water supply in the orbiter's
galley before the airlock is entered.  A plastic tube and valve assembly
extends up into the helmet so that the crewmember can take a drink whenever
needed.  Both the food bar and drink bag are held in place by Velcro
attachments.

        During EVAs, the crewmembers may need additional lighting to perform
their tasks.  A light-bar attachment (helmet-mounted light array) is placed
above the helmet visor assembly.  Small built-in flood lamps provide
illumination to places that sunlight and the regular payload bay lights do not
reach.  The EVA light has its own battery system and can be augmented with a
helmet-mountable television camera system with its own batteries and radio
frequency transmitter.  The camera's lens system is about the size of a postage
stamp.  Through this system, the crew remaining inside the orbiter and the
mission controllers on Earth can get an astronaut's eye view of the EVA action.
During complicated EVAs, viewers may be able to provide helpful advice for the
tasks at hand.

        Next, the Communications Carrier Assembly (CCA), or "Snoopy cap," is
connected to the EMU electrical harness and left floating above the HUT. The
CCA earphones and microphones are held by a fabric cap.  After the crewmember
dons the EMU, the cap is placed on the head and adjusted.

        When the tasks preparatory to donning the suit are completed, the lower
torso, or suit pants, is pulled on.  The lower torso comes in various sizes to
meet the varying size requirements of different astronauts.  It features pants
with boots and joints in the hip, knee, and ankle, and a metal body-seal
closure for connecting to the mating half of the ring mounted on the hard upper
torso.  The lower torso's waist element also contains a large bearing.  This
gives the crewmember mobility at the waist, permitting twisting motions when
the feet are held in workstation foot restraints.

        Joints for the lower and upper torsos represent an important advance
over those of previous spacesuits.  Earlier joint designs consisted of hard
rings, bellows-like bends in the pressure bladder, or cable- and
pulley-assisted fabric joints.  The Shuttle EMU joints maintain nearly constant
volume during bending.  As the joints are bent, reductions in volume along the
inner arc of the bend are equalized by increased volume along the outer arc of
the bend.

        Long before the upper half of the EMU is donned, the airlock's Service
and Cooling Umbilical is plugged into the Displays and Control Module Panel on
the front of the upper torso.  Five connections within the umbilical provide
the suit with cooling water, oxygen, and electrical power from the Shuttle
itself.  In this manner, the consumables stored in the Primary Life-Support
System will be conserved during the lengthy prebreathing period.  The SCU also
is used for battery and consumable recharging between EVAs.

        The airlock of the Shuttle orbiter is only 1.6 meters in diameter and
2.1 meters high on the inside.  When two astronauts prepare to go EVA, the
space inside the airlock becomes crowded.  For storage purposes and as an aid
in donning and doffing the EMU, each upper torso is mounted on airlock adapter
plates.  Adapter plates are brackets on the airlock wall for supporting the
suits' upper torsos.

        With the lower torso donned and the orbiter providing consumables to
the suits, each a crewmember "dives" with a squirming motion into the upper
torso.  To dive into it, the astronaut maneuvers under the body-seal ring of
the upper torso and assumes a diving position with arms extended upward.
Stretching out, while at the same time aligning arms with the suit arms, the
crewmember slips into the upper torso.  As two upper and lower body-seal
closure rings are brought together, two connections are made.  The first joins
the cooling water- tubing and ventilation ducting of the LCVG to the Primary
Life-Support System. The second connects the biomedical monitoring sensors to
the EMU electrical harness that is connected to the PLSS. Both systems are
turned on, and the crewmember then locks the two body-seal closure rings
together, usually with the assistance of another crewmember who remains on
board.

        One of the most important features of the upper half of the suit is the
HUT, or Hard Upper Torso. The HUT is a hard fiberglass shell under the fabric
layers of the thermal- micrometeoroid garment.  It is similar to the breast and
back plates of a suit of armor.  The HUT provides a rigid and controlled
mounting surface for the Primary Life-Support System on the back and the
Displays and Control Module on the front.

        In the past, during the Apollo Moon missions, donning suits was a very
lengthy process because the life-support system of those suits was a separate
item.  Because the Apollo suits were worn during launch and landing and also as
cabin-pressure backups, a HUT could not be used.  It would have been much too
uncomfortable to wear during the high accelerations and decelerations of
lift-off and reentry.  The life-support system had to be attached to the suit
inside the lunar module.  All connections between PLSS and the Apollo suit were
made at that time and, with two astronauts working in cramped quarters,
preparing for EVA was a difficult process.  The Shuttle suit HUT eliminates
that lengthy procedure because the PLSS is already attached.  It also
eliminates the exposed and vulnerable ventilation and life-support hoses of
earlier EMU designs that could become snagged during EVA.

        The last EMU gear to be donned includes eyeglasses if needed, the CCA,
comfort gloves, the helmet with lights and optional TV, and EVA gloves.  The
two gloves have fingertips of silicone rubber that permit some degree of
sensitivity in handling tools and other objects.  Metal rings in the gloves
snap into rings in the sleeves of the upper torso.  The rings in the gloves
contain bearings to permit rotation for added mobility in the hand area.  The
connecting ring of the helmet is similar to the rings used for the body-seal
closure.  Mobility is not needed in this ring, because the inside of the helmet
is large enough for the crewmember's head to move around.  To open or lock any
of the connecting rings, one or two sliding, rectangular- shaped knobs are
moved to the right or the left.  When opened, the two halves of the connecting
rings come apart easily.  To close and lock, one of the rings slides part way
into the other against an O-ring seal.  The knob is moved to the right, and
small pins inside the outer ring protrude into a groove around the inside ring,
thereby holding the two together.

        All suit openings have locking provisions that require a minimum of
three independent motions to open.  This feature prevents any accidental
opening of suit connections.

        With the donning of the helmet and gloves, the spacesuits are now
sealed off from the atmosphere of the airlock.  The crewmembers are being
supported by the oxygen, electricity, and cooling water provided by the
orbiter.  A manual check of suit seals is made by pressurizing each suit to
29.6 kilopascals d. (The "d" stands for differential, meaning above the airlock
pressure.) Inside the airlock, the pressure is either 70.3 or 101 kilopascals.
The suit's pressure is elevated an additional 29.6 kilopascals, giving it a
pressure differential above the air lock pressure.  Once pressure reaches the
desired level, the oxygen supply is shut off and the digital display on the
chest-mounted control module is read.  To assist in reading the display, an
optional Fresnel lens inside the space helmet may be used to magnify the
numbers.  Some leakage of spacesuit pressure is normal.  The maximum allowable
rate of leakage of the Shuttle EMU is 1.38 kilopascals per minute, and this is
checked before the suit is brought back down to airlock pressure.

        As the suit pressure is elevated, crewmembers may experience discomfort
in their ears and sinus cavities.  They compensate for the pressure change by
swallowing, yawning, or pressing their noses on an optional sponge mounted to
the left on the inside of the helmet ring.  Attempting to blow air through the
nose when pressing the nose on the sponge forces air inside the ears and sinus
cavities to equalize the pressure.

        During the next several minutes the two spacesuits are purged of any
oxygen/nitrogen atmosphere remaining from the cabin; this is replaced with pure
oxygen.  Additional suit checks are made while the final oxygen prebreathe
takes place.

        The inner door of the airlock is sealed, and the airlock pressure
bleed- down begins.  A small depressurization valve in the airlock latch is
opened to outside space, permitting the airlock atmosphere to escape.  While
this is taking place the EMU automatically drops its own pressure to 66.9
kilopascals and leak checks are conducted.  Failure of the leak test would
require repressurizing the airlock, permitting the EVA crew to reexamine the
seals of their suits.

        Final depressurization is begun by opening the airlock depressurization
valve.  The outer airlock hatch is then opened and the suited astronauts
prepare to pull themselves out into the payload bay.  As a safety measure, they
tether themselves to the orbiter to prevent floating away as they move from
place to place by hand holds.  It is at this point that they disconnect the
orbiter Service and Cooling Umbilical from the EMU. The PLSS begins using its
own supply of oxygen, cooling water, and electricity.  The astronauts pull
themselves through the outer airlock hatch, and the EVA begins.

The Primary and Secondary Life- Support Systems

Astronauts experienced their first real freedom while wearing spacesuits during
the Apollo Moon- walk EVAs, because of a portable life-support system worn on
their backs.  All other EVAs up to that time were tied to the spacecraft by the
umbilical-tether line that supplied oxygen and kept crewmembers from drifting
away.  In one sense, the tether was a leash, because it limited movements away
from the spacecraft to the length of the tether.  On the Moon, however,
astronauts were not hampered by a tether and, in the later missions, were
permitted to drive their lunar rovers up to 10 kilometers away from the lander.
(That distance limit was imposed as a safety measure.  It was determined that
10 kilometers was the maximum distance an astronaut could walk back to the
lander if a lunar rover ever broke down.)

        Space Shuttle astronauts have even greater freedom than the Apollo
lunar astronauts, because their EVAs take place in the near-weightless
environment of space.  They do employ tethers when EVAs center in and about the
Shuttle's payload bay, but those tethers act only as safety lines and do not
provide life support.  Furthermore, the tethers can be moved from one location
to another on the orbiter, permitting even greater distances to be covered.
When activities center some distance from the orbiter, a backpack style of
maneuvering system is used, limited in mobility only by the amount of
propellants carried in the system.

        The freedom of movement afforded to Shuttle astronauts on EVAs is due
to the Primary Life-Support System carried on their backs.  The PLSS, an
advanced version of the Apollo system, provides life support, voice
communications, and biomedical telemetry for EVAs lasting as long as seven
hours.  Within its dimensions of 80 by 58.4 by 17.5 centimeters, the PLSS
contains five major groups of components for life support.  Those are the
oxygen- ventilating, condensate, feedwater, liquid transport, and primary
oxygen circuits.

        The oxygen-ventilating circuit is a closed-loop system.  Oxygen is
supplied to the system from the primary oxygen circuit or from a secondary
oxygen pack that is added to the bottom of the PLSS for emergency use.  The
circulating oxygen enters the suit through a manifold built into the Hard Upper
Torso. Ducting carries the oxygen to the back of the space helmet, where it is
directed over the head and then downward along the inside of the helmet front.
Before passing into the helmet, the oxygen warms sufficiently to prevent
fogging of the visor.  As the oxygen leaves the helmet and travels into the
rest of the suit, it picks up carbon dioxide and humidity from the crewmember's
respiration.  More humidity from perspiration, some heat from physical
activity, and trace contaminants are also picked up by the oxygen as it is
drawn into the ducting built into the Liquid Cooling-and-Ventilation Garment. A
centrifugal fan, running at nearly 20,000 rpm, draws the contaminated oxygen
back into the PLSS at a rate of about 0.17 cubic meters per minute, where it
passes through the Contaminant Control Cartridge.

        Carbon dioxide and trace contaminants are filtered out by the lithium
hydroxide and activated charcoal layers of the cartridge.  The gas stream then
travels through a heat exchanger and sublimator for removal of the humidity.
The heat exchanger and sublimator also chill water that runs through the tubing
in the Liquid Cooling-and-Ventilation Garment. The humidity in the gas stream
condenses out in the heat exchanger and sublimator.  The relatively dry gas
(now cooled to approximately 13 degrees Celsius) is directed through a carbon
dioxide sensor before it is recirculated through the suit.  Oxygen is added
from a supply and regulation system in the PLSS as needed.  In the event of an
emergency, a purge valve in the suit can be opened.  The purge valve opens the
gas-flow loop, permitting the moisture and the carbon dioxide-rich gas to dump
outside the suit just before it reaches the Contaminant Control Cartridge.

        One of the by-products of the oxygen-ventilating circuit is moisture.
The water produced by perspiration and breathing is withdrawn from the oxygen
supply by being condensed in the sublimator and is carried by the condensate
circuit. (The small amount of oxygen that is also carried by the condensate
circuit is removed by a gas separator and returned to the oxygen- ventilating
system.) The water is then sent to the water-storage tanks of the feedwater
circuit and added to their supply for eventual use in the sublimator.  In this
manner, the PLSS is able to maintain suit cooling for a longer period than
would be possible with just the tank's original water supply.

        The function of the feedwater and the liquid transport circuits is to
cool the astronaut.  Using the pressure of oxygen from the primary oxygen
circuit, the feedwater circuit moves water from the storage tanks (three tanks
holding a total of 4.57 kilograms of water) to the space between the inner
surfaces of two steel plates in the heat exchanger and sublimator.  The outer
side of one of the plates is exposed directly to the vacuum of space.  That
plate is porous and, as water evaporates through the pores, the temperature of
the plate drops below the freezing point of water.  Water still remaining on
the inside of the porous plate freezes, sealing off the pores.  Flow in the
feedwater circuit to the heat exchanger and sublimator then stops.

        On the opposite side of the other steel plate is a second chamber
through which water from the liquid transport circuit passes.  The liquid
transport circuit is a closed- loop system that is connected to the plastic
tubing of the Liquid Cooling-and-Ventilation Garment. Water in this circuit,
driven by a pump, absorbs body heat.  As the heated water passes to the heat
exchanger and sublimator, heat is transferred through the aluminum wall to the
chamber with the porous wall.  The ice formed in the pores of that wall is
sublimated by the heat directly into gas, permitting it to travel through the
pores into space.  In this manner, water in the transport circuit is cooled and
returned to the LCVG. The cooling rate of the sublimator is determined by the
work load of the astronaut.  With a greater work load, more heat is released
into the water loop, causing ice to be sublimated more rapidly and more heat to
be eliminated by the system.

        The last group of components in the Primary Life-Support System is the
primary oxygen circuit.  Its two tanks contain a total of 0.54 kilograms of
oxygen at a pressure of 5,860.5 kilopascals, enough for a normal seven-hour
EVA. The oxygen of this circuit is used for suit pressurization and breathing.
Two regulators in the circuit step the pressure down to usable levels of 103.4
kilopascals and 29.6 kilopascals.  Oxygen coming from the 103.4- kilopascal
regulator pressurizes the water tanks, and oxygen from the 29.6-kilopascal
regulator goes to the ventilating circuit.

        To insure the safety of astronauts on EVAs, a Secondary Oxygen Pack is
added to the bottom of the PLSS. The two small tanks in this system contain 1.2
kilograms of oxygen at a pressure of 41,368.5 kilopascals.  The Secondary
Oxygen Pack can be used in an open-loop mode by activating a purge valve or as
a backup supply should the primary system fall to 23.79 kilopascals.

        If the Displays and Control Module purge valve (discussed below) is
opened, used- oxygen contaminants and collected moisture dump directly out of
the suit into space.  Because oxygen is not conserved and recycled in this
mode, the large quantity of oxygen contained in the SOP is consumed in only 30
minutes.  This half-hour still gives the crewmember enough time to return to
the orbiter's airlock.  If carbon dioxide control is required, the helmet purge
valve may be opened.  That valve has a lower flow rate than the DCM valve.

Displays and Control Module

The PLSS is mounted directly on the back of the Hard Upper Torso, and the
controls to run it are mounted on the front.  A small irregularly shaped box,
the Displays and Control Module, houses a variety of switches, valves, and
displays.  Along the DCM top are four switches for power, feedwater,
communications mode selection, and caution and warning.  A suit- pressure purge
valve projects from the top at the left for use with the emergency oxygen
system.  Near the front on the top is an alpha-numeric display.  A
microprocessor inside the PLSS permits astronauts to monitor the condition of
the various suit circuits by reading the data on the display.

        Stepped down from the top of the DCM, on a small platform to the
astronaut's right, is a ventilation-fan switch and a push-to-talk switch. (The
astronaut has the option of having the radio channel open at all times or only
when needed.) On a second platform, to the left, is an illuminated
mechanical-suit pressure gauge.  At the bottom, on the front of the DCM, are
additional controls for communications volume, display lighting intensity, and
oxygen flow.

Working In Space

One of the great advantages of working in space is that objects, including the
astronauts themselves, have no weight.  Regardless of the weight of an object
on Earth, a single crew- member can move and position that object in orbit with
ease provided that the crewmember has a stable platform from which to work.
Without that platform, any force exerted to move an object will be met with a
corresponding motion of the astronaut in the opposite direction.  A simple
Earth task, such as turning a nut with a wrench, can become quite difficult,
because the astronaut--and not the nut--may turn.

        The physics of working in space is the same as that of working on
Earth. All people and things contain matter and have mass.  Because of that
mass, they resist any change in motion.  Physicists refer to that resistance as
inertia.  The greater the mass, the greater the inertia.  To change the motion
of objects, an application of force is required.  According to Sir Isaac
Newton's Third Law of Motion, a force causing an object to move one way is met
with an equal and opposite force in the other direction.  The third law is more
familiarly stated as, "For every action there is an equal and opposite
reaction." A person planted firmly on the ground can lift heavy objects because
the equal and opposite force is directed downward through the legs and feet.
The inertia of Earth is so great that the corresponding response to that
downward force is infinitesimal.

        In space, astronauts do not have the advantage of having a planet to
stand on to absorb the equal and opposite force during work activities.
Although orbiting objects do not have the property of weight, they still resist
change in motion.  Pushing on an object causes the object and the crewmember to
float away in opposite directions.  To gain any advantage over objects, the
crewmember must be braced by a stable platform, such as the massive and
actively stabilized Shuttle orbiter itself, or must have a self-contained
maneuvering system--a kind of "rocket" backpack.

Manned Maneuvering Unit

During the first American EVA, Ed White experimented with a personal propulsion
device, the Hand-Held Maneuvering Unit (HHMU).  The HHMU tested by White was a
three- jet maneuvering gun.  Two jets were located at the ends of rods and
aimed back, so that firing them pulled White forward.  A third jet was aimed
forward to provide a braking force.  By holding the gun near his center of mass
and aiming it in the direction in which he wanted to travel, he was able to
propel himself forward.  Stopping that movement required firing the center jet.
The propulsive force of the HHMU was produced by releasing compressed oxygen
from two small built-in tanks.

        Although the HHMU worked as intended, it had two disadvantages.  To
produce the desired motion, it had to be held as close to the astronaut's
center of mass as possible.  Determining the center position was difficult
because of the bulky spacesuit White wore, and was a matter of guesswork and
experience.  Furthermore, precise motions to position an astronaut properly
during an activity such as servicing a satellite were difficult to achieve and
maintain, and proved physically exhausting.

        On the Gemini 9 mission, a backpack maneuvering unit was carried.
However, problems with the unit prevented Gene Cernan from testing it.

        Following the Gemini program, the next space experiments that tested
maneuvering units for EVAs took place during the second and third manned Skylab
missions.  The device was tested only inside the spacecraft, but the experiment
confirmed that a maneuvering device of that design was both feasible and
desirable for future EVA use.  The experiments were dubbed M-509. Five of the
six astronauts who flew in those two missions accumulated a total of 14 hours
testing the advanced device, called the AMU, or Astronaut Maneuvering Unit. The
AMU was shaped like a large version of a hiker's backpack.  Built into the
frame was a replaceable tank of compressed nitrogen gas.  Controls for the unit
were placed at the ends of "arm rests." To move, the astronaut worked
rotational and translational, or nonrotational, hand controls.  Propulsive jets
of nitrogen gas were released from various nozzles spaced around the unit.  The
14 nozzles were arranged to aim top-bottom, front-back, and right-left to
produce six degrees of freedom in movement.  The AMU could move forward and
back, up and down, and side to side, and could roll, pitch, and yaw.  With the
11 additional nozzles, precise positioning with the AMU was far simpler than
with the HHMU of the Gemini program.  The astronaut was surrounded by the unit,
taking the guesswork out of determining center of mass and making control much
more accurate.  The astronaut could move closely along the surface of a curved
or irregularly shaped object without making contact with it.

        The Manned Maneuvering Unit of the Space Shuttle is an advanced version
of the Skylab AMU. It is designed to operate in the weightless environment of
outer space and under the temperature extremes found there.  The MMU is
operated by a single space- suited astronaut.  The unit features redundancy to
protect against failure of individual systems.  It is designed to fit over the
life-support system backpack of the Shuttle EMU.

        The MMU is approximately 127 centimeters high, 83 centimeters wide, and
69 centimeters deep.  When carried into space by the Shuttle, it is stowed in a
support station attached to the wall of the payload bay near the airlock hatch.
Two MMUs are normally carried on a mission, and the second unit is mounted
across from the first on the opposite payload bay wall.  The MMU controller
arms are folded for storage, but when an astronaut backs into the unit and
snaps the life-support system into place, the arms are unfolded.  Fully
extended, the arms increase the depth of the MMU to 122 centimeters.  To adapt
to astronauts with different arm lengths, controller arms can be adjusted over
a range of approximately 13 centimeters.  The MMU is small enough to be
maneuvered with ease around and within complex structures.  With a full
propellant load, its mass is 148 kilograms.

        Gaseous nitrogen is used as the propellant for the MMU. Two aluminum
tanks with Kevlar filament overwrappings contain 5.9 kilograms of nitrogen each
at a pressure of 20.68 kilopascals, enough propellant for a six-hour EVA,
depending on the amount of maneuvering done.  In normal operation, each tank
feeds one system of thrusters.  In the event some of the thrusters fail,
crossfeed valves may be used to connect the two systems, permitting all
propellant from both tanks to be used.  At the direction of the astronaut,
through manual control or at the direction of an automatic attitude-hold
system, propellant gas is moved through feed lines to varying combinations of
24 nozzles arranged in clusters of three each on the eight corners of the MMU.
The nozzles are aimed along three axes perpendicular to each other and permit
six degrees of freedom of movement.  To operate the propulsion system, the
astronaut uses his or her fingertips to manipulate hand controllers at the ends
of the MMU's two arms.  The right-hand controller produces rotational
acceleration for roll, pitch, and yaw.  The left controller produces
acceleration without rotation for moving forward-back, up-down, and left-right.
Orders pass from the hand controls through a small logic unit (Control
Electronics Assembly) that operates the appropriate thrusters for achieving the
desired acceleration.  Coordination of the two controllers produces intricate
movements in the unit.  Once a desired orientation has been achieved, the
astronaut can engage an automatic attitude-hold function that maintains the
inertial attitude of the unit in flight.  This frees both hands for work.  Any
induced rotations produced by the astronaut's manipulating payloads and
equipment or by changes in the center of gravity are automatically countered
when sensed by small gyros.




Using the MMU

When it becomes necessary to use the MMU, an astronaut first enters the
orbiter's airlock and dons a spacesuit.  Exiting into space, the astronaut
attaches a safety tether and moves along handholds to the MMU. The maneuvering
unit is attached to the payload-bay wall with a framework that has stirrup-like
foot restraints.  Facing the MMU and with both feet in the restraints, the
crewmember visually inspects the unit.  If battery replacement is necessary or
if the propellant tanks need recharging, those tasks can be accomplished at
this time.  When ready, the astronaut turns around and backs into position.
The life-support system of the suit locks into place, hand-controller arms are
unfolded and extended, and the MMU is released from the frame.

        While maneuvering, the astronaut must use visual cues to move from one
location to another.  No other guidance system is necessary.  The only contact
with the orbiter during maneuvering is through the EMU radio
voice-communication equipment.

        While flying the MMU, the crewmember keeps track of the propellant
supply with two gauges located on either side of his or her head.  Keeping
track of the supply is important because when it is depleted no additional
maneuvering is possible.  This means that the astronaut must keep in reserve
for the return to the orbiter at least as much propellant as was expended in
flying out to the satellite.  The rest of the load can be used for maneuvering
on station with the target.  Generally, a total velocity change of 20.1 meters
per second is possible on one flight.  Furthermore, that delta velocity, as it
is called, must be divided in half so that propellant will be available for the
trip back.  It is divided in half again to allow for rotational accelerations.
Generally, astronauts fly the MMU at velocities of only 0.3 to 0.6 meters per
second relative to the Shuttle. While these velocities may seem small, they
accomplish much in the weightless environment of Earth orbit.  Once an
astronaut begins moving in a new direction or at a new velocity, he or she will
keep moving indefinitely until an opposing thrust is applied.

        Upon completion of assigned tasks, the astronaut returns to the payload
bay and reverses the unstowing procedure.  To assist in realignment with the
mounting frame, large mushroom-like knobs, built into the frame, are available
for grasping by the crewmember as he or she pushes backwards onto the frame.

Future Space Suits

The Space Shuttle Extravehicular Mobility Unit, Manned Maneuvering Unit, and
all the associated EVA systems are the result of many years of research and
development.  They now comprise a powerful tool for orbital operations, but
they are not end-of-the-line equipment.  Many improvements are possible: the
spacesuit of the future may look dramatically different from the Space Shuttle
EMU.

        Advanced versions of the EMU are being studied, including spacesuits
that operate at higher pressures than the current EMU. The advantage of higher
operating pressures is that virtually no time will be lost to prebreathing in
preparation for EVA.

        To build an operational high-pressure suit requires improved joint
technology and integration of those joints into the suit.  Under consideration
are fabric and metal suits and suits with a hard external shell.  Most of the
technology needed for these suits has already been tested.  One of the biggest
challenges is to make a highly mobile glove.  At higher operating pressures,
fingers of older-style spacesuit gloves become so increasingly stiff that
finger dexterity is severely reduced.  Research to address this problem has led
to the development of high-pressure gloves made with metal bands for knuckle
and palm joints.  These gloves show potential for use with future suits as well
as with current suits.

        Another potential advantage of high-pressure suits is that they can be
designed to be serviced and resized in orbit.  Current EMUs can be used in
space for up to 21 hours before they have to be completely cleaned and checked
out on Earth. One new EMU potentially could be used for several hundred hours
in space before a return to Earth is necessary.  This capability will be vital
when the United States constructs its first permanent space station in orbit.
There, crewmembers will remain in space for months at a time, and EVAs for
station maintenance could become a routine event.

        Another suit improvement is a "heads-up display" for reading the
instruments on the EMU chest-mounted displays and control module.  Heads-up
displays are currently being used in the cockpits of commercial and military
aircraft as well as on the flight deck of the Shuttle orbiter.  These displays
reflect instrument readings on a transparent screen so that a pilot can look
straight out the window while landing instead of continually tilting his or her
head down to check readings.  A heads-up display should make DCM readings
easier to see in sunlight and eliminate the need for Fresnel lenses or bifocals
for some crewmembers.

        The Manned Maneuvering Unit is also undergoing redesign.  Although the
exterior of the MMU is likely to remain the same, important changes are due on
the inside.  Larger nitrogen tanks, with greater operating pressures, could
lead to substantially increased operational range in space.

        Still further into the future, spacesuits will change to meet the
demands of new missions.  For the most part, the design of a spacesuit is based
on the environment in which it is designed to operate.  Space Shuttle
spacesuits for use in Earth orbit are designed to operate in a vacuum and
weightlessness.  A spacesuit for use on the surface of Mars, however, will
require a different design.  A Space Shuttle style of spacesuit would weigh
about 43 kilograms on Mars. Consequently, lighter EMU structures will be needed
to lessen the load a future Martian explorer will carry.  In addition, the thin
Martian atmosphere provides too much pressure for a cooling sublimator to work.
Some other cooling strategy will have to be devised.  Still another concern is
to provide protection from dust that is carried by Martian winds and will be
kicked up by the explorers.  These and other properties of the Martian
environment provide interesting and exciting challenges to spacesuit designers
and builders.

EVA

Starting with Edward White's spacewalk in 1965, American astronauts have logged
many hundreds of hours of extravehicular activity in space.  Mission planners
correctly foresaw the role EVA would play in future space missions.  The early
Gemini experience was primarily experimental.  During the Apollo and Skylab
programs, EVA was critical to success.  With the Space Shuttle, it is even more
critical.  The Shuttle, in spite of its complexity, is really a kind of space
truck.  It is a means--an economical transportation system--for getting
payloads into space and returning them to Earth. Enhancing the Shuttle's
capability is the Extravehicular Mobility Unit. By donning the EMU and
attaching a Manned Maneuvering Unit, an astronaut becomes a small, short-term
spacecraft.  Space-suited crewmembers can manipulate payloads, make
adjustments, repair broken parts, join pieces together, and handle a host of
other activities.  Most important, they bring with them the human ability to
cope with unexpected or unusual situations that occur in the hard and
unforgiving vacuum of outer space.

        With the capability of astronauts to go EVA, the Space Shuttle is more
than just a transportation system.  It is a satellite servicing vehicle, a
space structure assembly base, an assembly tool for future space station
construction, and a way station for preparing for deep space research missions.
EVA is a vital part of America's future in space.



Classroom Activities


The activities and related student projects that follow emphasize hands-on
involvement of the students.  Where possible, they make use of inexpensive and
easy-to-find materials and tools.  The activities are arranged into four basic
units, each relating to a different aspect of spacesuits and spacewalking.

Unit 1: Investigating the Space Environment

Objectives: To demonstrate how very different the space environment is from the
environment at the surface of Earth.

                To illustrate why spacesuits must be worn by astronauts going
on a spacewalk.

Unit 2: Dressing for Spacewalking

Objectives: To demonstrate how spacesuits create a livable environment for
astronauts.

                  To illustrate some of the complexities involved in
constructing a usable spacesuit.

Unit 3: Moving and Working in Space

Objective: To experience the problems astronauts face when trying to move and
work in space and understand how those problems are solved.

Unit 4: Exploring the Surface of Mars

Objective: To design, through a team effort, a spacesuit for future use on the
planet Mars.



Unit 1: Investigating the Space Environment

ACTIVITY 1: A Coffee Cup Demonstrates Weightlessness

TOPIC: Weightlessness in space

DESCRIPTION: A stream of water coming out of a hole in a cup stops when the cup
is dropped.

MATERIALS NEEDED:
Styrofoam or paper coffee cup
Pencil or other pointed object
Water
Bucket or other catch basin

PROCEDURE:

Step 1.  Punch a small hole in the side of the cup near its bottom.

Step 2.  Hold your thumb over the hole as you fill the cup with water.  Ask
students what will happen if you remove your thumb.

Step 3.  Remove your thumb and let the water stream out into the catch basin on
the floor.

Step 4.  Again seal the hole with your thumb and refill the cup.  Ask students
if the water will stream out of the hole if you drop the cup.

Step 5.  Drop the filled cup into the catch basin.  The demonstration is more
effective if you hold the cup high before dropping it.

DISCUSSION:

Earth-orbiting spacecraft experience a condition described as weightlessness.
The spacecraft is in a state of free-fall as it orbits.  If the spacecraft has
astronauts on board, the astronauts are able to move about with ease because
they too are in a state of free-fall.  In other words, everything in their
immediate world is falling together.  This creates the weightless condition.
Crewmembers and all the other contents of the spacecraft seemingly float
through the air.

On Earth, momentary weightlessness can be created in a number of ways.  Some
amusement parks achieve a second or two of weightlessness in certain wild
high-tech rides.  A springboard diver feels a moment of weightlessness at the
top of a spring just as the upward motion stops and just before the downward
tumbling motion to the water below begins.  As the diver falls, friction with
air quickly offsets the weightless sensation and produces drag that returns at
least a portion of the diver's weight before the water is struck.  NASA
eliminates the air friction problem and achieves about 30 seconds of
weightlessness with a special airplane.  High above Earth, the plane begins a
long arc-like dive downward at a speed equal to the acceleration of a falling
object.  After 30 seconds, the plane pulls out of the dive and climbs back to
the high altitude to begin another weightless cycle.  The airplane's skin and
engine thrust during the dive totally negate air friction on the people and
experiments in the plane.

The falling cup for a moment demonstrates weightlessness (or zero-g).  When the
cup is stationary, water freely pours out of the cup.  If the cup falls, the
water remains inside the cup for the entire fall.  Even though the water
remains inside, it is still attracted to Earth by gravity and ends up in the
same place that the water from the first experiment did.

The demonstration works best when students are asked to predict what will
happen when the cup is dropped.  Will the water continue to pour out the hole
as the cup falls?  If your school has videotape equipment, you may wish to
videotape the demonstration and then use the slow motion controls on the
playback machine to replay the action.

ADDITIONAL DEMONSTRATIONS ON WEIGHTLESSNESS:

* Place a heavy book on a bathroom scale.  Note the book's weight.  Drop the
book and scale together from a height of about a meter on to a mattress or some
pillows.  As it drops, quickly observe the book's weight. (The book's weight
becomes zero as it falls.)

* Cut a small hole in the lid of a clear plastic jar.  Drill a hole into a cork
stopper and insert one end of a drinking straw into the stopper.  Fill the jar
with water and place the cork inside the jar with the straw extending through
the hole.  Push the cork to the bottom.  Hold the jar a couple of meters off
the floor and drop it into someone's hands.  As it falls, watch the cork and
straw. (During free-fall, the buoyancy of the cork disappears.)

* Obtain a clear plastic tube (hard or soft plastic but not glass) from a
hardware store.  Cap one end of the tube, fill with colored water, and cap the
other end.  A small amount of air remaining in the tube will form a bubble.
Hold the tube upright so that the bubble begins rising from the bottom.  When
the bubble is halfway to the top, toss the tube to someone near you.  Observe
where the bubble is when the tube is caught by the other person. (The bubble
stops rising to the top while the tube travels through the air.)

ACTIVITY 2: Meteoroids and Space Debris

TOPIC: Potential hazard to spacewalkers from meteoroids and space debris

DESCRIPTION: The penetrating power of a projectile with a small mass but high
velocity is demonstrated.

MATERIALS NEEDED:
Raw baking potato
Large-diameter plastic straw

PROCEDURE:

Step 1.  Hold a raw potato in one hand.  While grasping the straw with the
other hand, stab the potato with a quick, sharp motion.  The straw should
penetrate completely through the potato.  Caution: Be careful not to strike
your hand.

Step 2.  Again hold the potato and this time stab it with the straw using a
slow push.  The straw should bend before penetrating the potato very deeply.

DISCUSSION:

Astronauts on spacewalks are likely to encounter fast-moving rocky particles
called meteoroids.  A meteoroid can be very large with a mass of several
thousand metric tons, or it can be very small--a micrometeoroid about the size
of a grain of sand.  Every day Earth's atmosphere is struck by hundreds of
thousands or even millions of meteoroids, but most never reach the surface
because they are vaporized by the intense heat generated when they rub against
the atmosphere.  It is rare for a meteoroid to be large enough to survive the
descent through the atmosphere and reach solid Earth. If it does, it is called
a meteorite.

In space there is no blanket of atmosphere to protect spacecraft from the full
force of meteoroids.  It was once believed that meteoroids traveling at
velocities averaging 80 kilometers per second would prove a great hazard to
spacecraft.  However, scientific satellites with meteoroid detection devices
proved that the hazard was minimal.  It was learned that the majority of
meteoroids are too small to penetrate the hull of spacecraft.  Their impacts
primarily cause pitting and sandblasting of the covering surface.

Of greater concern to spacecraft engineers is a relatively recent problem--
spacecraft debris.  Thousands of space launches have deposited many fragments
of launch vehicles, paint chips, and other "space trash" in orbit.  Most
particles are small, but traveling at speeds of nearly 30,000 kilometers per
hour, they could be a significant hazard to spacecraft and to astronauts
outside spacecraft on extravehicular activities.

Engineers have protected spacecraft from micrometeoroids and space trash in a
number of ways, including construction of double-walled shields.  The outer
wall, constructed of foil and hydrocarbon materials, disintegrates the striking
object into harmless gas that disperses on the second wall.  Spacesuits provide
impact protection through various fabric-layer combinations and strategically
placed rigid materials.

Although effective for particles of small mass, these protective strategies do
little if the particle is large.  It is especially important for spacewalking
astronauts to be careful when they repair satellites or do assembly jobs in
orbit.  A lost bolt or nut could damage a future space mission through an
accidental collision.

ADDITIONAL DEMONSTRATION ON METEOROIDS AND SPACE DEBRIS:

* Aim a pea shooter at a piece of tissue paper taped to a cardboard frame.  Aim
the shooter at the tissue paper and blow hard into the shooter to accelerate
the pea to the tissue at a high velocity.  Drop the pea on to the tissue paper
from a height of two meters.  In the first demonstration the pea will penetrate
the tissue, but in the second the pea will bounce.



ACTIVITY 3: Air Pressure Can Crusher

TOPIC: Vacuums

DESCRIPTION: Air pressure exerts a force that crushes an aluminum beverage can.

MATERIALS NEEDED:
Aluminum beverage can
Tongs to hold the can
Dish of cold water
Heat source (propane torch set at low  flame, alcohol lamp)
Eye protection for demonstrator
Towel for cleanup


PROCEDURE:

Step 1.  Place approximately 30 ml of water in the can and heat it to boiling.
Permit the water to boil for at least 30 seconds before removing it from the
heat.

Step 2.  Immediately invert the can and thrust its top (end with the opening) a
short distance into the cold water.  The can will collapse implosively.
Caution: Avoid splashing the boiling water.


DISCUSSION:

The crushed can in this activity demonstrates the force of air pressure.  An
absence of pressure is a deadly hazard of space flight.

The can collapses because a partial vacuum has been created inside and its
metal walls are not strong enough to sustain its original shape against the
outside air pressure.  The first step in creating the vacuum is to boil the
water inside the can to produce steam.  After approximately 30 seconds of
boiling, the air in the can is replaced by the steam.  When the can is inverted
into the cold water, a rapid temperature drop takes place, causing the steam to
return to water drops.  What is left is a vacuum.  Since the opening of the can
is sealed with water in the dish, the can collapses before water in the dish
has a chance to fill the void.

The amount of air pressure on the can may be calculated by determining the
surface area of the can and multiplying this by a sea-level air pressure of 101
kilopascals:

Surface area of can = area of cylinder + area of 2 ends
                        or
Surface area of can = 2 pi r x length  + 2 x pi r squared



ACTIVITY 4:  Boiling Water With Ice

TOPIC: Vacuums

DESCRIPTION: A sealed flask of hot water is brought to a boil by immersing it
in ice water.

MATERIALS NEEDED:
Pyrex glass boiling flask (round or flat bottom)
Solid rubber stopper to fit flask
Bunsen burner or propane torch (flame spreader optional)
Ring stand and clamp
Aquarium filled with ice water
Eye protection for anyone standing near the boiling flask

PROCEDURE:

STEP 1.  Fill the flask to about one-third capacity with water and attach to
the ring stand.

STEP 2.  Heat the bottom of the flask until the water begins to boil.

STEP 3.  Remove the heat source.  When the boiling stops, insert the stopper.

STEP 4.  Free the clamp from the stand and immerse the entire flask in the
aquarium.  Be sure the side of the aquarium is wiped free of condensation so
that the flask can easily be seen.  Observe what happens to the water in the
flask.

DISCUSSION:

Water boils when its temperature reaches 100 degrees C. The act of boiling
changes the state of matter from liquid into gas.  In doing so, heat is carried
away by the gas, so that the remaining liquid cools below the boiling point.
Consequently, continuous heating is necessary until all the liquid is converted
to gas.

Although the boiling temperature of water appears to be fixed, it is not.  It
varies with air pressure.  Water boils at 100 degrees C at a sea-level pressure
of 101 kilopascals.  However, water's boiling temperature drops as air pressure
drops, and air pressure drops with elevation above sea level. (Because of
depressed boiling temperatures at higher elevations, many commercial cake mixes
come with instructions for increasing baking times if the cake is going to be
baked in a mountain home.)

At very low atmospheric pressures, such as those encountered at elevations
higher than 18 km above sea level, water boils spontaneously even at room
temperature.  This creates a problem for pilots of high-altitude research
planes and astronauts in space.  The human body is approximately 60% water.  At
very low atmospheric pressures, body water contained within the skin would
begin to boil, and the skin would start inflating.  Needless to say, this is a
very unpleasant experience and one that can be fatal if it persists for too
many seconds.  High-altitude pilots and astronauts on extravehicular activity
require pressure-suit protection for survival.

This demonstration shows the effect of lowered pressure on the boiling point of
water.  When the water has stopped boiling and the flask is sealed, it is
thrust into chilled water.  The temperature of the hot, moist air above the
water in the flask is quickly lowered and it contracts, thereby lowering the
pressure inside the flask.  With the lowered pressure, the water, even though
its temperature has actually lowered, begins boiling again.  Boiling will stop
shortly as the pressure in the flask increases due to newly released gas.

Note: The rubber stopper may be difficult to remove from the flask once the
water inside the flask has cooled.  Simply reapply heat to the flask and remove
the stopper as air pressure inside increases.  Be sure to wear eye protection
while doing this.


Additional Demonstrations on Vacuums

Additional demonstrations on the properties of the vacuum found in space can be
done with a vacuum pump, vacuum plate, and bell jar.  This apparatus is
available through science supply catalogs, and many schools have them in their
equipment inventories.  If your school does not have this equipment, it may be
possible to borrow it from another school.

* Set the alarm on a windup alarm clock to ring in a few minutes.  Place the
clock on the vacuum plate, cover with the bell jar, and evacuate the air.  When
the alarm goes off, it will be possible to see but not hear the clock ring.
There is no air inside the chamber to conduct the sound waves from the ringing
of the bell.  Some sound may conduct through the vacuum plate, however, through
its contact with the clock feet.  This demonstration illustrates why radios are
built into spacesuits.  Contrast this demonstration with science fiction movies
in which sounds from explosions are heard through space.

* Obtain a clear balloon or a clear plastic freezer bag.  Put water in the
balloon or bag and seal.  Place the balloon or bag on the vacuum plate, cover
with the bell jar, and evacuate the chamber.  Observe the boiling that takes
place in the water and how the balloon or bag begins to inflate.  The inflation
provides an analogy to the way exposed skin will inflate in a vacuum because of
the gas bubbles that form in the liquid contained in cells.





STUDENT PROJECT 1: Earth Is a Spaceship

TOPIC: Earth as a life-support system for travel through space

BACKGROUND INFORMATION: Every 365 days, 5 hours, and 46 minutes, Earth
completes an orbit around the Sun. To do so, it travels at a speed of 109,500
km per hour.  At the same time this is happening, our Sun and all its planets
are traveling in the direction of the star Vega at a speed of 20 km per second.
As a part of the Milky Way galaxy, we are also orbiting the galactic center at
a speed of about 250 km per second.  Finally, the Milky Way is on its own
voyage through the universe at a speed of 600 km per second.  Combining all
these motions together, we discover that Earth is actually a spaceship,
hurtling us through space at the incredible speed of approximately 900 km per
second, or nearly 30 billion km per year!

Writing Assignment: Like astronauts traveling on rockets or moving about
through outer space in their spacesuits, earthling astronauts need protection
from the hazards of space. * Write an essay about spaceship Earth. What
"services" does Earth provide for human life-support?  How do the ways Earth
provides these services compare with the way the life-support system of a
spacesuit functions?  Why is it important to protect our life-support systems?
* Write a short story on what might happen to our spaceship if we do not take
care of it.

Art Project: Create a mural, collage, or mobile that illustrates the spaceship
Earth concept.

Mathematics Assignment: Compare the travel of spaceship Earth with terrestrial
locomotion-such as walking, running, automobiles, trains, airplanes-and with
the Space Shuttle. How long would it take a person in an automobile (train,
plane, etc.) to travel the distance Earth travels through space in just one
hour?

Historical Research: Try to learn who first proposed the concept of Earth as a
spaceship and the event that led to the development of this environmental
concept.




Unit 2: Dressing for Spacewalking

ACTIVITY 1: Choosing the Right Color

TOPIC: Spacesuit design

DESCRIPTION: The relative effects of light versus dark surfaces on heat
absorption and radiation are investigated.

MATERIALS NEEDED:
2 coffee cans with plastic snap lids
2 thermometers (dial or glass)
Spray paint (white and black)
Flood lamp and light fixture
Stopwatch or watch with a second hand
Graph paper

PROCEDURE:

STEP 1.  Spray-paint the outside of one coffee can black and spray the other
white.

STEP 2.  Snap on the plastic lids and punch a hole in the center of each lid.
Insert one thermometer into each lid.

STEP 3.  Direct the light from a flood lamp at the sides of the two cans.  Make
sure it is equidistant from both cans.

STEP 4.  Begin recording temperatures starting with an initial reading of each
thermometer, and take readings thereafter every 30 seconds for the next 10
minutes.  Extend the time beyond 10 minutes if you wish.

STEP 5.  Plot the temperature data on graph paper, using a solid line for the
black can and a dashed line for the white can.  Construct the graph so that the
data for temperature are along the Y (vertical) axis and for time along the X
(horizontal) axis.

STEP 6.  Compare the slope of the temperature plots for the white and black
cans.

DISCUSSION:

It is not by chance or for aesthetics that the outer layer of a spacesuit is
constructed of a durable white fabric.  Environments in outer space fluctuate
from shade to full sunlight.  In full Sun, the temperature will rise to 120
degrees C and in shade drop to minus 100 degrees C. Such extremes are
constantly being encountered by astronauts out on extravehicular activities.
The side of the astronaut facing the Sun cooks while the side in shade freezes.

One of the challenges in spacesuit design is to maintain a comfortable working
temperature inside.  A liquid cooling-unit inside the suit helps moderate body
heat caused by the astronaut's physical exertion, but the heat coming into the
suit from the outside and the heat escaping from the suit to the outside must
be moderated as well.  Several inside layers provide insulation, but that is
not enough to protect the crew member.  White fabric on the outside of the suit
is used because it absorbs less heat than does dark fabric.


ACTIVITY 2: Keeping Cool

TOPIC: Spacesuit design

DESCRIPTION: The functioning of the liquid cooling-garment of spacesuits is
demonstrated.

MATERIALS NEEDED:
2 coffee cans with plastic snap-on lids
2 thermometers (dial or glass.  Must be able to read a full range of
 temperatures from freezing to boiling.)
Spray paint (black)
Floodlight and light fixture
6 meters of plastic aquarium tubing
Masking tape
2 buckets
Ice
Water
Stopwatch or watch with a second hand
Graph paper
Metal punch or drill



PROCEDURE:

STEP 1.  Spray-paint the outside of both cans black and permit them to dry.

STEP 2.  Punch a hole in the center of each lid and insert a thermometer.
Punch a second hole in one of the lids large enough to admit the aquarium
tubing.  Also punch a hole in the side of one of the two cans near its base.

STEP 3.  Form a spiral coil with the plastic tubing along the inside wall of
the can with the hole punched in its side.  Do not pinch the tube.  Extend the
tube's ends out of the can, one through the hole in the can and the other
through the hole in the lid.  The upper end of the tube should reach into the
elevated water bucket and the other should hang down from the side of the can
toward the lower bucket.

STEP 4.  Set up the floodlight so that it shines on the sides of the two cans.
Make sure the light is equidistant from the two cans.

STEP 5.  Fill one bucket with ice and water.  Make sure there is enough ice to
chill the water thoroughly.

STEP 6.  Elevate the ice water bucket on a box or some books next to the can
with the tubing.

STEP 7.  Insert the long end of the aquarium tubing into the ice water bucket
to the bottom.  Using your mouth, suck air from the other end of the tube to
start a siphoning action.  Permit the water to drain into a second bucket on
the floor.

STEP 8.  Immediately turn on the floodlight so that both cans are equally
heated.

STEP 9.  Begin recording temperatures, starting with an initial reading of each
thermometer just before the light is turned on and every 30 seconds thereafter
until the water runs out.

STEP 10.  Plot the temperature data on graph paper, using a solid line for the
can that held the ice water and a dashed line for the other can.  Construct the
graph so that the temperature data are along the Y (vertical) axis and those
for time along the X (horizontal) axis.

STEP 11.  Compare the slope of the plots for the two cans.

DISCUSSION:

Astronauts out on extravehicular activity are in a constant state of exertion.
Body heat released from this exertion can quickly build up inside a spacesuit,
leading to heat exhaustion.  Body heat is controlled by a liquid
cooling-garment made from stretchable spandex fabric and laced with
small-diameter plastic tubes that carry chilled water.  The water is circulated
around the body.  Excess body heat is absorbed into the water and carried away
to the suit's backpack, where it runs along a porous metal plate that permits
some of it to escape into outer space.  The water instantly freezes on the
outside of the plate and seals the pores.  More water circulates along the back
of the plate.  Heat in the water is conducted through the metal to melt the ice
directly into water vapor.  In the process, the circulating water is chilled.
The process of freezing and thawing continues constantly at a rate determined
by the heat output of the astronaut.

This activity demonstrates how chilled water can keep a metal can from heating
up even when exposed to the strong light of a floodlight.

ADDITIONAL DEMONSTRATIONS ON COOLING:

* Make a sleeve of spandex (stretchable) fabric.  Lace the sleeve with plastic
aquarium tubing as shown.  Circulate cold water through the sleeve with a
siphoning action to demonstrate the cooling effects of the Shuttle EMU's liquid
cooling-and-vent- garment.  Discuss how the water is recycled and rechilled.
(Note: To assist in placing the sleeve on different people, slit the side of
the sleeve from one end to the other and attach Velcro strips.)

* Make small bags of various materials to test their insulating properties.
Slip a thermometer into each bag and measure the bags' temperature rise when
exposed to a heat source such as a floodlight or sunlight.  Try using fabrics,
paper, aluminum foil, and plastics as well as commercial insulating materials
such as rock wool and cellulose.  Also experiment with multilayered materials.
Compare the bulk and weight of different insulators with their effectiveness.
What criteria must spacesuit designers use in evaluating spacesuit insulation?
(Weight, bulk, durability, flexibility, flammability.)


ACTIVITY 3: Oxygen for Breathing

TOPIC: Spacesuit life-support

DESCRIPTION: The lung capacity of an average student is determined and related
to the oxygen supply carried in the portable life-support system of a
spacesuit.

MATERIALS:
Large glass cider jug
Rubber or plastic hose
Basin
Measuring cup
Permanent marking pen
Water
Hydrogen peroxide or other nontoxic
   disinfectant
Exercise device such as a stationary bike (optional)
Stop watch or clock with a second hand

PROCEDURE:

Step 1.  Calibrate the glass jug in units of liters.  Pour 1 liter of water
into the jug and mark the water level on the side of the jug.  Add a second
liter and again mark the level.  Repeat twice more.

Step 2.  Completely fill the jug with water and invert it into a basin of water
so that air pressure causes the water to remain in the jug.  Insert one end of
the tube into the jug.

Step 3.  Invite several student volunteers, one at a time, to exhale through
the tube into the jug.  Water will be expelled from the jug.  Students should
breathe normally when doing this.  Count how many breaths it takes to empty the
water from the bottle.  Also, determine the number of breaths each student
takes during one minute.  Record the two measurements on a chart under the
headings "Breathing Volume" and "Breaths per Minute." Caution: Be sure to
disinfect the end of the tube between student participations.

Step 4.  After all volunteers have participated in the first measurements, run
the experiment again, but this time have each student engage in vigorous
exercise for 1 minute before breathing into the tube.  Using an exercise bike
or running in place should be sufficient to promote heavy breathing.  Again
measure how many breaths are required to empty the jug.  Also measure the
number of breaths each student takes during a period of one minute.  Keep a
record of these numbers under the headings of "Breathing Volume II" and
"Breaths per Minute II."

Step 5.  Calculate averages for each of the four columns on the data chart.
Use the first set of measurements to determine what volume of air an average
student will consume per minute during normal activity.  Next, calculate how
much air is needed for one hour by that average student under normal activity
and under heavy work.

Step 6.  Ask the students to calculate how much air would be needed by an
average student-astronaut on a six-hour spacewalk.  Typically, space-walks
involve both light and heavy exertion.

Discussion:

It is of obvious concern to spacewalking astronauts to have enough oxygen to
breathe while they are conducting a mission.  They need enough oxygen to
complete their assigned tasks and additional oxygen in case of unforeseen
problems and emergencies.  How much oxygen they carry with them is determined
by their oxygen use rate and the time length of their mission.  Physically
difficult tasks cause astronauts to use oxygen more rapidly than do physically
simple tasks.

To provide enough oxygen for spacewalk missions, NASA has had to determine
oxygen use rates for different levels of physical activity.  Oxygen use is
measured rather than air use because it was determined early in the space
program that using air for spacewalks would be inefficient because air would
require very large holding tanks.  Air is approximately 80 percent nitrogen and
20 percent oxygen.  By eliminating the nitrogen and providing pure oxygen, much
smaller tanks can be used.

In this activity, students have determined the amount of air an average student
breathes during rest and during heavy physical activity.  They have calculated
how much air would be needed for a six-hour spacewalk.  If no one thinks of it,
suggest they consider using pure oxygen instead of air.  Have your students
calculate the volume of pure oxygen that would satisfy the needs of the average
student for the six-hour mission and compare this to the quantity of air that
would be required for the same mission.


ACTIVITY 4: Keeping the Pressure Up

TOPIC: Spacesuit life-support

DESCRIPTION: How spacesuits maintain a safe pressure environment is
demonstrated.


MATERIALS NEEDED:
Bicycle or automobile foot pump (with pressure gauge)
Gear type of hose clamp (small  size--available from hardware store)
Helium quality balloon--30 to 40 cm diameter (several)
Ripstop nylon (about 45 cm from fabric-store bolt)
Thread
Sewing machine
Scissors
Screw driver

PROCEDURE:

Step 1.  Use the pattern on the next page to make the nylon restraint layer
bag.

Step 2.  Slide the pump nozzle entirely into a balloon.  The valve should
almost touch the other side of the balloon.

Step 3.  Slip the hose clamp over the balloon nozzle and tighten it over the
air hose.

Step 4.  While watching the pressure gauge, pump up the balloon until it
breaks.  Make a note of the maximum pressure attained.

Step 5.  Slip a second balloon over the nozzle as before.

Step 6.  Insert the balloon and nozzle into the nylon bag.  The nozzle of the
balloon should lie just under the nozzle of the bag.

Step 7.  Use the hose clamp to seal both the balloon and the bag around the air
hose.

Step 8.  While watching the pressure gauge, pump up the balloon.  Stop pumping
when the gauge reaches 35 to 70 kilopascals (5 to 10 lbs per square inch if
pump gauge is in English units).  Feel the bag.

Note: The balloon can be deflated by loosening the hose clamp.

DISCUSSION:

Pressure is essential to human survival in space.  Spacesuits provide pressure
by enclosing an astronaut inside an airtight bag.  A spacesuit is made up of
many layers.  The pressure-containing portion of the suit is a nylon layer
coated on the inside with rubber.  The rubber, by itself, acts like a balloon
to contain oxygen.  This would be fine except that balloons expand when they
are pressurized.  A spacesuit with just a rubber layer would grow bigger and
bigger until it popped.  However, the nylon or restraint layer prevents this
from happening by permitting expansion to go only so far.  Any additional
oxygen added to the inside increases the pressure that is exerted on the
astronaut wearing the suit.

In this activity, the balloon simulated the rubber layer of a spacesuit, and
the nylon bag simulated the restraint layer.  When an unrestrained balloon was
pumped up, it just increased in size until it popped.  Even at the moment of
popping, the pressure gauge barely moved.  With the restraint layer over the
balloon, the balloon could expand only so much, and then additional air pumped
inside increased the internal pressure.  Thereupon, the bag became very hard
and stiff.

The safe operating pressure inside a Shuttle spacesuit is about 29.65
kilopascals.  Although this pressure is about one-third that at sea level on
Earth, the astronaut wearing the suit experiences no difficulty in breathing,
for the gas inside is pure oxygen rather than the approximately 20 percent
concentration of oxygen in normal air.  Even at the lower pressure, the
astronaut takes in more oxygen with each breath inside a spacesuit than on
Earth while breathing a normal air mixture.


SEWING INSTRUCTIONS:

Cut out two layers of ripstop nylon according to the pattern and stitch up
along the sides indicated.  Provide a 1-cm seam allowance.  Restitch the seam
with a zigzag stitch for reinforcement.  Turn the bag inside out.  You may wish
to hem the open end of the bag to prevent fraying.

ACTIVITY 5: Bending Under Pressure

TOPIC: Spacesuit mobility

DESCRIPTION: Students compare the ability of inflated balloons to bend in an
analogy to the arm of a spacesuit.

MATERIALS NEEDED:
2 long balloons
3 plastic bracelets, metal craft rings, or thick rubber bands

PROCEDURE:

Step 1.  Inflate one balloon fully and tie it.

Step 2.  Inflate the second balloon, but while it is inflating, slide the
bracelets, craft rings, or rubber bands over the balloon so that the balloon
looks like sausage links.

Step 3.  Ask the students to compare the "bendability" of the two balloons.

DISCUSSION:

Maintaining proper pressure inside a spacesuit is essential to astronaut
survival.  A lack of pressure is fatal.  Pressure, however, produces its own
problems.  An inflated spacesuit can be very difficult to bend.  In essence, a
spacesuit is a balloon with the astronaut inside.  The rubber of a balloon
keeps in air.  But, as pressure inside the balloon builds up, the balloon's
walls become stiff and hard to bend.  It would be impossible for an astronaut
to function effectively in a stiff suit.


Spacesuit designers have learned that strategically placed breaking points (the
rings in this demonstration) at appropriate points outside the pressure bladder
(the balloon-like layer inside a spacesuit) makes the suit become more
bendable.  The breaking points help form joints that bend more easily than
unjointed materials.  The same thing happens with the balloon and rings.
Further spacesuit research has determined that there are other techniques for
promoting bending.  Built-in joints, like ribs on vacuum cleaner hoses, also
promote easier bending than does unjointed material.


ACTIVITY 6: Getting The Right Fit


TOPIC: Spacesuit design

DESCRIPTION: Students design and build space helmets that can be used by anyone
in class.

MATERIALS NEEDED:

Several cloth tape measures (metric)
Metric rulers
Cardboard calipers (see diagram)
Brass paper fasteners
Pencil and paper
Calculator (optional)
Large, round balloons
Papier mache: paste and newspaper
String
Graph paper
Field-of-view measurement device
        Plywood board 60x30 cm
        White poster board
        Thumbtacks
        Marking pen
        Protractor

PROCEDURE: Head Measurements

1.  Divide the students into groups of three to five.

2.  Working as teams, the students should take four separate measurements of
each member's head in centimeters, and tally the data.  The measurements will
be: (1) Head Circumference, (2) Head Breadth, (3) Head Depth, (4) Chin to Top
of Head. Refer to the diagram in the next column.  Use calipers and cloth tape
measures for the actual measuring.  Be sure the students check each other's
work.

3.  After the measurements are taken, the teams should practice calculating
averages by averaging the measurements for all members of the team.

4.  Tally the results for all the groups in the class and calculate averages
for each measure.

PROCEDURE: Field of View

1.  Construct a field-of-view measurement device out of wood and poster board.
Cut a partial circle (220 degrees) with a radius of at least 30 cm out of
plywood.  Refer to the pattern on the next page for details.  Tack or glue a
strip of white poster board to the arc.  Using a protractor and a marking pen,
measure and mark the degrees around the arc as shown in the illustration.

2.  Place the device on the edge of a table so that it extends over the edge
slightly.  Begin measuring the field of view by having a student touch his or
her nose to the center of the arc and look straight ahead.  Have a second
student slide a marker, such as a small strip of folded paper, around the arc.
Begin on the right side at the 110-degree mark.  The student being tested
should say, "Now," when he or she sees the marker out of the corner of the eye.
Record the angle of the marker on a data table for the right eye.  Repeat for
the left eye.

3.  Take the same measurements for the other students.  When all the data have
been collected, calculate the average field of view for all the students.

PROCEDURE: Designing a Space Helmet

1.  Working in the same teams as before, have the students draw sketches on
graph paper of their ideas for a space helmet that could be worn by anyone in
class.  The students should determine a scale on the graph paper that will
translate into a full-size helmet.  In designing the helmet, three
considerations must be met.  First, it must fit anyone in the class.  Second,
it must provide adequate visibility.  Finally, it must be made as small as
possible to reduce its launch weight and make it as comfortable to wear as
possible.

2.  Students may wish to add special features to their helmet designs such as
mounting points for helmet lights and radios.

PROCEDURE: Building a Space Helmet

1.  Have each team inflate a large round balloon to serve as a form for making
a space helmet.  Tie the balloon with a string.

2.  Using strips of newspaper and papier mache paste, cover the balloon except
for the nozzle.  Put on a thin layer of newspaper and hang the balloon by the
string to dry.

3.  After the first layer of papier mache is dry, add more layers until a rigid
shell is formed around the balloon.  Lights, antennas, and other appendages can
be attached to the helmet as the layers are built up.

4.  Using a pin, pop the balloon inside the paper mache shell.  According to
the design prepared in the earlier activity, cut out a hole for slipping the
helmet over the head and a second hole for the eyes.

5.  Paint the helmet and add any designs desired.

6.  When all helmets are completed, evaluate each one for comfort and utility.
Have students try on the helmets and rate them on a scale that the students
design. (For example: on a scale of 1 to 5, with 1 the best, how easy is it to
put the helmet on?)

DISCUSSION:

Spacesuit designers have expended great energy to make sure spacesuits fit
their wearers properly.  It is essential that suit joints line up with the
wearer's joints.  A mismatched elbow can make it very difficult for the wearer
to bend an arm.

To save on spacesuit construction costs, designers have sought to develop
common parts that can be worn by the greatest number of people.  To do so has
required careful evaluation of the human form.  Many different people have been
measured to determine the ranges of sizes that a spacesuit must fit
comfortably.  In the present activity only a few head measurements were taken,
but in designing complete spacesuits many different measurements are necessary.
The dimensions below are based on a spacesuit designed to fit astronauts having
this range of measurements. * Stature increases approximately 3 percent over
the first three to four days in weightlessness.  Because almost all the change
appears in the spinal column, other dimensions, such as vertical trunk
dimension, increase selectively.

Thigh circumference will significantly decrease during the first day in orbit
due to the shift of fluid to the upper torso.

Category                                Minimum (cm) Maximum (cm)

A.      Stature*                              162.1   187.7
B.      Vertical trunk dimension               64.3    74.4
C.      Crotch height                          32.3    38.9
D.      Knee height                            74.4    91.9
E.      Wrist to wrist distance               131.6   167.1
F.      Elbow to elbow distance                85.9   106.2
G.      Chest breadth                          27.9    36.6
H.      Head breadth                           12.7    16.5
I.      Hip breadth                            32.3    38.9
J.      Arm reach                              80.5    94.2
K.      Shoulder to wrist reach                62.2    73.7
L.      Chest depth                            21.3    27.7
M.      Head depth                             18.3    21.6
N.      Chin to top of head                    21.8    24.4
O.      Hip depth                              21.1    27.4
P.      Foot length                            24.1    29.2
Q.      Foot width                              8.9    10.7
R.      Thigh circumference                    52.1    67.1
S.      Biceps circumference (flexed)          27.4    36.8
T.      Chest circumference                    89.2   109.7
U.      Instep                                   NA     8.3
V. Head circumference                          55.5    60.2





STUDENT PROJECT 2: Spacesuit History

TOPIC: How spacesuits evolved into their present design

BACKGROUND INFORMATION: The Extravehicular Mobility Unit worn by Space Shuttle
astronauts is the result of decades of research and testing.  The introductory
material in this activity guide provides a brief history of its development.

Research and Writing Assignment: Ask students to research spacesuit history and
write reports on specific topics.  Students might choose from the following
topics:

  Project Mercury Spacesuits
  Project Gemini Spacesuits
  Project Apollo Spacesuits
  Skylab Spacesuits
  Soviet Cosmonauts' Spacesuits
  High-Altitude Aircraft Pressure Suits
  Comparison of Spacesuits with Deep Sea  Divers' Suits
  Spacesuits in Science Fiction Stories and Film

Art Project: Create a mural of the evolution of spacesuit design.


UNIT 3: MOVING AND WORKING IN SPACE

ACTIVITY 1: Spinning Chair

TOPIC: Moving in space

DESCRIPTION: Students sit, one at a time, on a swivel chair and try to make the
chair turn without touching the floor or other furniture with their hands or
feet.

MATERIALS NEEDED:
Swivel stool or desk chair with a good bearing mechanism that permits smooth
motion
2 sandbags made from canvas sacks (about 2 kg each)

PROCEDURE:

STEP 1.  Ask for a volunteer student to sit on the chair or stool.

STEP 2.  Instruct the student to make the chair or stool turn in a circle.  The
student must not touch the floor or anything else except the chair's seat.
Stand back and watch.

STEP 3.  Permit other students to try.

STEP 4.  Help students out by giving them sandbags to hold in their hands.  If
no student thinks to toss the bags, suggest that he or she do so at an angle
perpendicular to their extended arms (tangential direction).

Caution: Do not use a stool or chair that tips easily.  Stand nearby to keep
the student from falling.  The student should toss the bags gently at first.

DISCUSSION:

Although very difficult, some circular motion may be possible with the chair.
Astronauts away from the inside walls of the Space Shuttle orbiter quickly
learn that through awkward twisting, it is possible to change their direction.
However, the moment they stop the twisting, the movement they had achieved
stops as well.  In spite of the movement, center of mass is exactly in the same
place as it was before.  They learn that to achieve movement from place to
place it is necessary to have something to push against to start and something
else at the other end to push against to stop.

Outside the orbiter, the problem of movement becomes even more difficult.  If
an astronaut bumps something and is not attached to the orbiter by a tether,
the astronaut will simply drift away in the opposite direction, and no amount
of twisting and turning will reverse or stop the drift.

In the demonstration, the swivel chair illustrates the manner in which
astronauts can change the direction they face but cannot move away without
having something to push against.  The sandbags, however, do permit real
movement through the action-reaction principle stated by English scientist Sir
Isaac Newton. The chair continues to spin for a time after the movement stops.
Astronauts take advantage of this principle when they wearthe Manned
Maneuvering Unit while on extravehicular activity.  The unit releases
compressed nitrogen gas to propel the astronaut along, just as air escaping
from a balloon propels it along.

ACTIVITY 2: Fizz, Pop!


TOPIC: Moving in space

DESCRIPTION: Action-reaction demonstration using "antacid power."

MATERIALS NEEDED:
Plastic 35-mm film canister
Masking tape
String
Water
Effervescent antacid tablet
Eye protection for demonstrator
Towel for mop up

PROCEDURE:

STEP 1.  Attach a string to the side of a plastic film canister with tape as
shown in the illustration.  Suspend the canister from the ceiling, waist-high
above the floor.

STEP 2.  Make a small tape loop and press it to the inside of the film canister
cap.  Press an effervescent antacid tablet to the tape.

STEP 3.  Hold the canister upright and fill it halfway with water.  Snap the
cap, with the tablet, onto the canister snugly.

STEP 4.  Tip the canister to its side and suspend it from the string.  Prevent
it from swinging.  Stand back and watch. (Note: Some film canisters don't work
as well as others.  It is advisable to have a backup in case the first one
fizzles.)

Caution: Although this activity does not present a significant eye hazard, eye
protection is recommended for the demonstrator.

DISCUSSION:

Immediately upon contact with water, the tablet begins effervescing.  Because
the cap is snapped onto the film canister, gas pressure builds up.  Eventually,
the cap pops off the end of the canister, releasing the water and gas inside.

The explosive separation of the lid from the canister provides an action force
that is balanced with a reaction force that causes the canister to swing the
other way.  This is a simple demonstration of the action-reaction principle
described in Newton's Third Law of Motion.

In space, any deviation of a spacecraft's motion from its orbit requires an
action- reaction force to be expended.  An astronaut on a spacewalk can
accomplish the same end by pushing against the spacecraft.  The action-reaction
force will propel the astronaut in the opposite direction.

Precise movements in space by space-walkers can be achieved with the Manned
Maneuvering Unit. Although it operates by the same principle as does the
popping film canister, the MMU is propelled by compressed nitrogen gas.  The
MMU is far more controllable than the canister because it has 24 nozzles
instead of just the one opening.  Shaped like a box with arms, the MMU has
nozzles arranged in clusters of three at each corner.  Controls on each arm
permit sequential firing of pairs of nozzles for precise movements.


ADDITIONAL DEMONSTRATIONS ON THE ACTION-REACTION PRINCIPLE:

* Tape a round balloon to the end of a flexible soda straw.  Push a pin through
the straw into a pencil eraser.  Inflate the balloon through the straw and let
the air escape.

* Make a Hero engine from an aluminum beverage can.  Punch angled holes around
the base of the can and suspend the can with a piece of string.  Fill the can
with water by immersing it in a bucket of water.  Raise the can out of the
water by lifting it with the string.  Observe what happens.

The Hero engine was invented by Hero (also called Heron) of Alexandria sometime
around the first century B.C. His engine was a sphere connected to a
water-filled kettle heated from below.  Steam produced by boiling water escaped
through two L-shaped tubes and caused the sphere to spin.  Remarkably, the Hero
engine was considered a novelty and, reportedly, no attempt to harness its
power was made at that time.

The principle behind the engine is simple.  Steam from the boiling water inside
the kettle pressurizes the sphere.  The steam rapidly escapes through the
tubes, producing an action-reaction force that causes the sphere to spin.  The
action- reaction principle of the Hero engine is the same that is used to
propel airplanes and rockets.


ACTIVITY 3: Space Tools

TOPIC: Space tools

DESCRIPTION: Students practice using tools while wearing heavy gloves that
represent the gloves worn by astronauts on spacewalks.

MATERIALS NEEDED:
Several sets of thick insulated ski gloves or heavy rubber work gloves
Miscellaneous tools and items such as
        Needle-nose pliers
        Socket wrenches
        Small machine screws and nuts
        Lamp cord and plug
        Tinker Toys (tm) or Legos (tm)
        Perfection (tm) game
Paper and pencil

PROCEDURE:

STEP 1.  Instruct students to put on the gloves and begin working with the
tools and other items.  The gloves represent the stiff, bulky gloves astronauts
wear while on space-walks.

STEP 2.  Have your students compare the difficulty of doing a particular task
such as wiring a lamp cord to a plug, assembling a structure out of
construction toys, or writing a message, with and without gloves. .

STEP 3.  Ask your students to try to design tools that could help them do their
work in space if they were repairing a satellite.

DISCUSSION:

Spacesuit gloves can be stiff and hard to work in.  The gloves worn by Apollo
astronauts on the Moon caused much finger fatigue and abrasion during long Moon
walks.  Designers for the Shuttle spacesuit have placed special emphasis on
making pressurized gloves more flexible and easy to wear.  This is not a simple
task because, when inflated, gloves become stiff just like an inflated balloon.
Designers have employed finger joints, metal bands, and lacings to make gloves
easier to use.

A second effort is underway to create design tools for use with spacesuit
gloves.  Even with very flexible spacesuit gloves, small parts and conventional
tools can be difficult to manipulate.  This activity illustrates the problem of
manipulating objects and encourages students to custom-design tools to help
spacewalkers do their jobs.

STUDENT PROJECT 3: EVA Tools and Workstations

TOPIC: The design of EVA tools and workstations for Space Station Freedom

BACKGROUND INFORMATION: When Space Station Freedom is constructed, astronauts
may have to don their spacesuits and participate in a variety of assembly tasks
to bring its parts together.  After the station becomes operational, EVAs will
be necessary for periodic Space Station maintenance, unscheduled repairs, and
to service payloads.  Years of EVA experience have shown that even simple jobs,
such as turning a screw with a screwdriver, can be very difficult in space if
no anchor point is available for the astronaut to brace against.  Much research
has been invested in the creation of special tools and workstations to make EVA
jobs easier.  The screwdriver problem is solved with an electric screwdriver
that pits the astronaut's inertia against the friction of the screw.  Bracing
an astronaut for work is solved with workstations--platforms with footholds and
tool kits.

Design Project: Ask students to design tools and a workstation that can be used
by astronauts outside Space Station Freedom. The workstation should have
provisions for holding the astronaut in place, holding tool kits, providing
adequate lighting, and being moved around the outside of the Space Station to
different work sites.  The tools should make possible a variety of tasks such
as screwing screws, tightening bolts, cutting and splicing wires, and
transferring fluids.  Students should include in their designs provisions for
preventing the tools from drifting off if they slip out of an astronaut's hand
and for extending the reach of an astronaut.  Have your students illustrate
their designs and present oral or written reports on how their tools and
workstation will be used.  If possible, have them build prototype tools for
testing in simulated EVAs.


Unit 4: Exploring the Surface of Mars


GROUP PROJECT: Exploring the Surface of Mars

OBJECTIVE: This project encourages students to work cooperatively in the
development of a spacesuit for the exploration of the surface of Mars and to
conduct a simulated EVA on the surface of the planet.

BACKGROUND INFORMATION: The National Aeronautics and Space Administration has
begun planning for a bold new program that it calls the Space Exploration
Initiative. Also known as SEI, the initiative is based on the goals President
George Bush outlined in a major speech he gave on the 20th anniversary of the
first Apollo Moon landing.  The President called for a return to the Moon and
exploration of the planet Mars.

Making these exploration goals possible will require the development of many
new technologies, including suits for exploring the Martian surface.  The
Martian environment, although less hostile than that of outer space, is such
that a human could not survive there without protection.  Although NASA has
extensive experience with spacesuits used on the Moon and with suits used on
the Space Shuttle, Mars offers new challenges in suit design.  Mars has a
gravitational pull equal to almost four-tenths that of Earth. This means that
new, lightweight structures will be needed to minimize the load the wearer will
have to bear.  Other factors to be accounted for include a thin atmosphere that
will require a new kind of suit-cooling system, wind-blown Martian dust, and a
temperature range that is similar to Earth's. These and many other factors must
be accounted for in creating a new suit for exploring Mars.

Teacher's Instructions: Divide your students into working groups that will each
work on some aspect of the design of new Martian exploration suits.  Each group
should select a group leader who will keep track of the activities of the group
and report on accomplishments and problems encountered.  Also select one or
more students as mission managers to see that all groups are working smoothly
and on time.  Working with the mission managers, develop a schedule for the
completion of each group's assigned task.  When the suits have been designed
and constructed, conduct a simulated mission on the surface of Mars to evaluate
the design of the suits.

This activity offers students many opportunities for important lessons in
problem solving.  For example, one problem is that not everyone can become an
astronaut.  When the time comes for the actual exploration of Mars, only a tiny
fraction of the people on Earth will be able to go.  In this activity, only two
of the students will wear the suits in the simulation.  How should those
students be selected?  What criteria should be used?  What about the people
left behind?  The important lesson is that everyone's job is important and that
teamwork is essential or else the mission would not be possible.  The success
of the Martian explorers is the success of everyone involved.

Another of the opportunities offered by this activity is the involvement of
parents and community members.  Parents and community members may be willing to
donate suit construction materials and help with the sewing and other tasks of
fabrication.

Student Challenge:

You have been assigned to work on one of the teams that will design and test
new exploration suits for use on the surface of the planet Mars. You will be
given a specific assignment as part of one of several working groups.  The goal
for all working groups is to bring the components of two prototype suits
together so that they can be tested on a simulated Martian mission.  Because
you will be developing prototype suits for testing on Earth, these suits will
not have to be sealed and pressurized.

Working Group Assignments



Working Group 1: Research

What is the environment of Mars like?  Go to astronomy books and encyclopedias
to find out such important environmental characteristics of Mars as its surface
gravity, atmospheric pressure, atmospheric composition, temperature range, and
surface composition.  Also determine the average size of the students in the
class so that the group working on the design and construction will know how
large to build the prototype suits.  Determine the range and average of your
classmates' measurements, including their body height and arm and leg length.

(Teacher's Note: Because of sensitivity to weight, measuring waists and chests
is not recommended.  The prototype suits should be made in a large or extra
large size to fit any of the students.)


Working Group 2: Design

What will the Martian suit look like?  To answer this question, network with
the research working group to find out what the Martian environment is like.
The research working group can also tell you how big to make the suits.
Contact the life-support working group for details on how the suit will provide
a suitable atmosphere, temperature control, and food and water.  Furthermore,
consider what kinds of tools the Martian explorers are likely to need.  Create
drawings of the Martian suits and patterns for their construction.


Working Group 3: Life Support

How will you keep the Martian explorers alive and safe in their exploration
suits?  What will you do to provide air for breathing, provide pressure, and
maintain the proper temperature?  How will you monitor the medical condition of
the explorers?  Contact the research working group for details on the
environment of Mars. Make drawings of the Mars suit's life-support system and
write descriptions of how it will work.  Share your plans for life-support with
the design working group.


Working Group 4: Construction

From what will you build the Martian exploration suits?  Contact the design and
life-support working groups for the suit components you must build.  Obtain
suit patterns from the design working group and collect the necessary
construction materials.  Build two Mars exploration suits.  You may be able to
get donations of construction materials from community businesses and the
assistance of parents in fabricating the suits.

Working Group 5: Astronaut Selection and Training

Who should be selected to be the astronauts in the simulated mission?  Create
application forms for interested students who wish to become Martian explorers.
Give an application to every interested student.  Conduct interviews and select
prime and backup crews for the simulated mission.  Design a simulated Mars
mission that will last 15 minutes.  What should the explorers do on Mars?
Obtain materials to create a mini-Martian environment in one corner of the
classroom.  Contact the research working group to learn what the surface of
Mars looks like.  Develop training activities so that the prime and backup
crews can practice what they will do when they test the suit.  Create emergency
situations of the kind that might be encountered on Mars so that the crews can
practice emergency measures.  One emergency might be a dust storm.

The Simulation:

Prepare a small test area in one corner of the classroom or in a separate room.
Decorate the test area to resemble a portion of the Martian environment.  Also
prepare a Mission Control center where the test conductors can observe the
simulated mission and communicate with the astronauts.  If video equipment is
available, set up a television camera on a tripod in the test area and stretch
a cable to a television monitor in Mission Control. To add additional realism,
communicate with the astronauts using walkie-talkies.  During the simulation,
one very important communication issue will have to be set aside.
Communication between Mission Control and the astronauts during the simulation
will be instantaneous.  During the actual mission to Mars, one-way
communication time between Mars and Earth will be at least 20 minutes.  If an
astronaut asks a question of mission control, 20 minutes will elapse before the
message will reach Earth and another 20 minutes will elapse before the answer
can be returned.  Consequently, the Martian explorers will have to be very well
trained to meet every kind of emergency imaginable.

Additional Activities:

* Create a mission patch.

* Publish a project newsletter filled with stories about working group
activities, Mars, and other space exploration information.

* Invite parents and community members to observe the simulation.

* Let every student try on the suits and take photos for keepsakes.



Glossary

AMU             Astronaut Maneuvering Unit
Apollo          NASA project that landed astronauts on the Moon
CCA             Communications Carrier Assembly
CCC             Contaminant Control Cartridge
DACT            Disposable Absorption and Containment Trunk (female
                urine-collection system)
DCM             Displays and Control Module
EEH             EMU Electrical Harness
EMU             Extravehicular Mobility Unit
EVA             Extravehicular Activity; Extravehicular Visor Assembly
Gemini          NASA project that pioneered space flight technologies for
                spacecraft rendezvous and docking and spacewalking
HHMU            Hand-Held Maneuvering Unit
HUT             Hard Upper Torso
IDB             In-Suit Drink Bag
LCVG            Liquid Cooling-and-Ventilation Garment
MMU             Manned Maneuvering Unit
Mercury         The NASA project that launched the first U.S. astronauts into
                space and demonstrated that humans could live and work in space
PLSS            Primary Life-Support System
RMS             Remote Manipulator System
SCU             Service and Cooling Umbilical
SEI             Space Exploration Initiative
Skylab          First U.S. space station
SOP             Secondary Oxygen Pack
Space Shuttle   Reusable spaceship currently  used for all U.S. manned space
                missions
Space Station Freedom   The international space station under development by
                NASA, European Space Agency, Japan, and Canada
UCD             Urine Collection Device (male urine- collection system)

References and Resources


Allen, J.P. with Martin, M. (1984), Entering Space, An Astronaut's Odyssey,
Stewart, Tabori & Chang, New York.

Challenger Center (1991), Suited for Space Activity Book, Challenger Center for
Space Science Education, Alexandria, VA.

Compton, W. & Bensen, C. (1983), Living and Working In Space, A History of
Skylab, NASA SP-4208, Scientific and Technical Information Branch, NASA,
Washington.

Froehlich, W. (1971), Apollo 14: Science at Fra Mauro, EP-91, NASA, Washington.

Machell, R. ed. (1967), Summary of Gemini Extravehicular Activity, NASA SP-
149, Scientific and Technical Information Division, Office of Technology
Utilization, NASA, Washington.

Mohler, S.R. & Johnson, B.H. (1971), Wiley Post, His Winnie Mae, and the
World's First Pressure Suit, Smithsonian Institution Press, Washington.

NASA (1973), Apollo, EP-100, NASA, Washington.

NASA (1970), Apollo 12, A New Vista for Lunar Science, EP-74, NASA, Washington.

NASA (1971), Apollo 15 At Hadley Base, EP-94, NASA, Washington.

NASA (1972), Apollo 16 At Descartes, EP-97, NASA, Washington.

NASA (1973), Apollo 17 At Taurus-Littrow, EP-102, NASA, Washington.

NASA (1991), Go For EVA, Liftoff to Learning Series. (Videotape), Education
Working Group, Johnson Space Center.

NASA (1987), The Early Years: Mercury to Apollo-Soyuz, Information Summaries,
PMS 001-A, Kennedy Space Center, FL.

NASA (1970), The First Lunar Landing As Told by The Astronauts, EP-73, NASA,
Washington.

Vogt, G. (1987), Spacewalking, Franklin Watts, New York.

Vogt, G. and Haynes, R. (1990), Spacesuit Guidebook, PED-117, NASA, Washington.