Spacesuit Demo
Introduction:
A spacesuit must protect the astronauts
from the harsh environments of space.
In space there are very few air
molecules. Note that air pressure is the
result of the movement and collisions of
air molecules. This absence of
molecules is referred to as a vacuum.
An astronaut's body fluids would fizz
and bubble without protection.
The Earth's atmosphere exerts a
pressure against our bodies. This
pressure is 14.7 pounds per square inch
at sea level. This pressure helps keep
our bodily fluids from escaping or
changing into vapor, although some is
lost through perspiration and other
means. This air pressure thus places a
stress on our bodies. Gravity also places a stress on bodies.
When this air pressure is removed, an astronaut's body changes to release this stress according
to Le Chatelier's principle. This is achieved through the boiling of bodily fluids. The internal
stress in the astronaut's body drives this change.
The purpose of this launch/entry suit is to provide the astronauts with protection against the heat
and pressure changes during liftoff. It also provides an extra layer of
protection from cold or fire in case of an emergency. It consists of
an outer suit, long underwear, communications hat, helmet,
parachute, flotation device, gloves, back pad, seat support, boots,
gravity pants, socks, diaper, and diaper belt. Yes, each astronaut
needs to wear a diaper because the liftoff acceleration puts
pressure on the astronaut's bladder. Also, the astronauts must sit
through a long countdown prior to launch, which may last three
hours.
Spacesuits for the space shuttle era are pressurized at 4.3 pounds
per square inch (psi), but because the gas in the suit is 100 percent
oxygen instead of 20 percent, the person in a spacesuit actually has
more oxygen to breathe than is available at an altitude of 10,000
feet or even at sea level without the spacesuit. Before leaving the
space shuttle to perform tasks in space, an astronaut has to spend
several hours breathing pure oxygen before proceeding into space.
This procedure is necessary to remove nitrogen dissolved in body
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fluids and thereby to prevent its release as gas bubbles when pressure is reduced, a condition
commonly called "the bends."
The heavy and complex suits currently in use are hardly the sort of outfit you can just throw on.
And even in the microgravity of orbit, moving and working while wearing the massive
contraptions during an extravehicular activity (EVA) can
quickly exhaust an astronaut.
The Job of a Spacesuit
Outer space is an extremely hostile place. If you
were to step outside a spacecraft such as the
International Space Station, or onto a world with little
or no atmosphere, such as the moon or Mars, and
you were not wearing a spacesuit, the following
things would happen:
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You would become unconscious within 15
seconds because there is no oxygen.
Your blood and body fluids would "boil" and
then freeze because there is little or no air
pressure.
Your tissues (skin, heart, other internal organs) would expand because of
the boiling fluids.
You would face extreme changes in temperature:
 sunlight: 248 degrees Fahrenheit / 120 degrees Celsius
 shade: -148 F / -100 C
 You would be exposed to various types of radiation, such
as cosmic rays, and charged particles emitted from the sun (solar wind).
You could be hit by small particles of dust or rock that move at high speeds
(micrometeoroids) or orbiting debris from satellites or spacecraft.
So, to protect you from these dangers, a spacesuit must:
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Have a pressurized atmosphere
Give you oxygen
Remove carbon dioxide
Maintain a comfortable temperature despite strenuous work and
movement into and out of sunlit areas
Protect you from micrometeoroids
Protect you from radiation to some degree
Let you see clearly
Allow you to move your body easily inside the spacesuit
Let you talk with others (ground controllers, other astronauts)
Let you move around the outside of the spacecraft
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Extravehicular Mobility Unit (EMU)
Contains:
EMU Facts
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Maximum Absorption Garment (MAG) collects urine produced by the astronaut
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Liquid Cooling and Ventilation Garment
(LCVG) - removes excess body heat produced by
the astronaut during spacewalks
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EMU Electrical Harness (EEH) - provides
connections for communications and bioinstruments
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Communications Carrier Assembly (CCA) contains microphones and earphones for
communications
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Lower Torso Assembly (LTA) - lower half of the
EMU including pants, knee and ankle joints,
boots and lower waist
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Hard Upper Torso (HUT) - hard fiberglass shell
that supports several structures including the
arms, torso, helmet, life-support backpack and
control module
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Arms
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Gloves - outer and inner gloves
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Helmet
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Extravehicular Visor Assembly (EVA) - protects the astronaut from
bright sunlight
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In-suit Drink Bag (IDB) - provides drinking water for the astronaut during
the spacewalk
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Primary Life Support Subsystem (PLSS) - provides oxygen, power,
carbon dioxide removal, cooling water, radio equipment and warning
system
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Secondary Oxygen Pack (SOP) - provides emergency oxygen supply
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Display and Control Module (DCM) - displays and controls to run the
PLSS
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Weight = 280 lb
(127 kg) on Earth
Thickness = 3/16
in (0.48 cm), 13
layers
Atmosphere = 4.3
lb/in2 (0.29 atm) of
pure oxygen
Volume = 4.4 to
5.4 ft3 (.125 to .153
m3) without
astronaut
Cost = $12 million
each
Contractors Hamilton
Sundstrand, ILC
Dover
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Extravehicular Mobility Unit Continued
While early spacesuits were made entirely of soft fabrics, the EMU has a combination of soft
and hard components to provide support, mobility and comfort. The suit itself has 13 layers of
material, including an inner cooling garment (two layers), pressure garment (two layers), thermal
micrometeroid garment (eight layers) and outer cover (one layer). The materials used include:
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Nylon tricot
Spandex
Urethane-coated Nylon
Dacron
Neoprene-coated Nylon
Mylar
Gortex
Kevlar (material in bullet-proof vests)
Nomex
All of the layers are sewn and cemented together to form the suit. In contrast to early
spacesuits, which were individually tailored for each astronaut, the EMU has component pieces
of varying sizes that can be put together to fit any given astronaut.
Communications Carrier Assembly (CCA)
The CCA is a fabric cap worn by the astronaut. It contains microphones and speakers for use
with the radio. It allows hands-free radio communications within the suit.
Lower Torso Assembly (LTA)
The LTA is a one-piece unit that contains the lower half of the EMU, including pants, knee and
ankle joints, boots and lower waist. It is fitted to the upper half of the EMU by a metal connect
ring. The LTA has loops to tether tools so that they do not float away in space.
Hard Upper Torso (HUT)
The HUT is a hard fiberglass shell in the shape of a vest. It supports several structures including
the arms, lower torso, helmet, life-support backpack and control module. It can also hold a minitool carrier. Pieces click into the HUT through quick-connect rings.
Arms
Arm units contain shoulder, upper arm and elbow joint bearings so that the astronaut can move
his or her arms in many directions. The arm units come in various sizes so that the EMU can be
fitted to different astronauts. The arm units fit into the HUT by quick connect rings.
Gloves
Like the arm units, gloves have wrist bearings for easy movement. They fit into the arms by
quick-connect rings. The gloves have rubberized fingertips to help astronauts grip things.
Astronauts also wear fine-fabric gloves inside the outer glove units for comfort. The outer gloves
have loops on them to tether tools.
Helmet
The helmet is made of clear, impact-resistant, polycarbonate plastic, and fits to the HUT by a
quick-connect ring. The helmet is padded in the rear for comfort, because the helmet remains
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fixed rather than rotating with the astronaut's head. It has a purge valve to remove carbon
dioxide if the backup oxygen supply must be used. In the helmet, oxygen flows from behind the
astronaut's head, over the head and down his or her face. The inside of the helmet is treated
with an anti-fog compound prior to the spacewalk.
Extravehicular Visor Assembly (EVA)
The EVA fits over the helmet. It has the following pieces:
 A metallic-gold-covered visor to filter sunlight
 A clear, impact resistant cover for thermal and impact protection
 Adjustable blinders to block sunlight
 Four head lamps
 A TV camera
In-suit Drink Bag (IDB)
Astronauts working in a spacesuit for up to seven hours need water. So the spacesuit has the
IDB, which is a plastic pouch mounted inside the HUT. The IDB can hold 32 ounces (1.9 liters)
of water and has a small tube, a straw, that is positioned next to the astronaut's mouth.
There is also a slot in the helmet for a rice-paper-covered fruit and cereal bar that the astronaut
can eat if he or she gets hungry during the spacewalk. The bar is designed so that the astronaut
can take a bite and pull the remainder up. The entire bar must be eaten at once to prevent
crumbs from floating within the helmet. However, most astronauts prefer to eat prior to the
spacewalk and not use this bar.
Primary Life-Support Subsystem (PLSS)
The PLSS is the backpack worn by the astronaut. It contains the oxygen tanks (1.2 lb / 0.54 kg
at 518 atm tank pressure), carbon dioxide scrubbers/filters, cooling water (10 lb / 4.6 kg total),
radio, electrical power, ventilating fans and warning systems. Oxygen flows into the suit behind
the astronauts's head and out of the suit at the feet and elbows. Once inside the PLSS, the air
flow enters a charcoal cartridge, to remove odors, and then the carbon dioxide scrubber
cartridge. The gas flow then goes through a fan, and then to a sublimator that removes water
vapor and returns it to the cooling-water supply. The temperature of the air flow is maintained at
55 F (12.8 C). The astronaut can adjust the temperature, pressure and air flow through controls
on the DCM. The PLSS provides up to seven hours of oxygen supply and carbon dioxide
removal.
The EMU battery is made of 11 zinc cells connected in series. The battery provides about 27
amp-hours of electrical current, and can be recharged inside the shuttle.
Secondary Oxygen Pack (SOP)
The SOP is an emergency oxygen supply that fits below the PLSS on the backpack frame. It
has two oxygen tanks that contain a total of 2.6 lb (1.2 kg) at 408 atm tank pressure. This is
enough oxygen for 30 minutes, which is sufficient time to get a crewmember back inside the
spacecraft. This oxygen supply automatically turns on when the oxygen pressure in the suit
drops below 0.23 atm.
Display and Control Module (DCM)
The DCM is a chest-mounted unit. It contains all of the switches, gauges, valves and LCD
displays necessary to operate the PLSS. The DCM can be seen by the astronaut, sometimes
with the aid of a sleeve-mounted mirror.
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In addition to these major parts, the EMU has some of the following accessories:
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Servicing and Cooling Umbilical (SCU) - provides connections to the spacecraft's
oxygen, power, communication and water lines
Airlock Adapter Plate (AAP) - holds the EMU pieces while the astronaut is suiting up
Helmet Lights and Camera - provide additional lighting and cameras for ground control
monitoring
Sleeve-mounted Mirrors - help astronauts see gauges on the DCM
Sleeve-mounted Checklists - remind them of spacewalk procedures
Servicing and Cooling Umbilical (SCU)
The SCU is an umbilical cord containing tubes for cooling water, electrical wires for power and
tubes for oxygen. The SCU is used to provide water, power and oxygen to the EMU while the
astronaut is in the airlock preparing for the spacewalk. This helps conserve the EMU's
expendable supplies until the astronaut actually leaves the spacecraft.
Airlock Adapter Plate (AAP)
The AAP is a frame mounted to the wall of the airlock that helps hold the EMU pieces while the
astronaut is suiting up.
Helmet Lights and Camera
These devices are mounted on the EVA, which fits over the helmet. They are used to help the
astronauts and ground controllers see into dark areas.
Sleeve-mounted Mirrors and Checklists
These devices fit over the sleeves of the EMU. The mirrors help the astronauts see the DCM
displays and see behind them. The checklists help them remember procedures over the course
of a seven-hour spacewalk.
Maneuvering in space
The manned maneuvering unit (MMU) is a oneman, nitrogen-propelled backpack that latches
to the EMU spacesuit's PLSS. Using rotational
and translational hand controllers, the crew
member can fly with precision in or around the
orbiter cargo bay or to nearby free-flying
payloads or structures, and can reach many
otherwise inaccessible areas outside the
orbiter. Astronauts wearing MMU's have
deployed, serviced, repaired, and retrieved
satellite payloads.
The MMU propellant-non-contaminating
gaseous nitrogen stored under high pressure-can be recharged from the orbiter. The
reliability of the unit is guaranteed with a dual
parallel system rather than a backup redundant system. In the event of a failure in one parallel
system, the system would be shut down and the remaining system would be used to return the
MMU to the orbiter cargo bay The MMU, which weighs 310 pounds, includes a 35-mm still
photo camera that is operated by the astronaut while working in space.
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