The fitting elastic fabric, with small tubing sewn

The
spacesuit has many different configurations; for example the spacesuit is
modified for being within the spaceship, instead of being outside the
spaceship. The Extravehicular Mobility Unit (EMU) is the component of the spacesuit
that allows an astronaut to work outside a spacecraft for up to seven hours in
the harsh environment of space. The EMU has various components that regulate
heat. Among them is the full body liquid cooling and ventilation garment
(LCVG). This garment itself has 13 layers of material, which make up an inner
cooling garment, the pressure garment, the thermal micrometeoroid garment and
the outer cover. The purpose of the LCVG is to removes excess body heat produced
by the astronaut during spacewalks.   

Figure
1: Liquid Cooling Ventilation Garmet
Diagram

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

There
is a need to remove excess body heat from the astronaut for two reasons: the
first being that the astronaut has to have many layers of insulation for
protection against radiation and, the second reason being that the human body
has to maintain a certain temperature to remain in homeostasis. As mentioned
previously, the astronauts are exposed to radiation from the sun, which can
alter the state of cells in the body, making the astronaut sick. A normal
healthy body temperature for a human ranges between 36.1 degrees Celsius and
37.2 degrees Celsius. When exposed to too much heat, people can experience heat
exhaustion which can result in dizziness, headache and fainting. When sustained
heatwaves hit a region a person can even suffer major organ damage. Therefore,
it is critical for the LCVG to exist in a spacesuit and regulate the heat
transfer and safety of the astronaut.

The
LCVG has many components. One component is having various ventilation ducts
which are small holes that take moist air from the wearer – essentially
removing sweat from the astronauts’ skin. The LCVG also has a special fabric
that contributes to keeping the astronaut cool. The fabric is a tight fitting
elastic fabric, with small tubing sewn along the garment in a parallel
configuration. Cool water passes through the tubing, removing excess heat from
the astronaut’s body. The tubing has a small diameter which allows more
flexibility for the astronaut, but unfortunately still permits a lower heat
absorption capacity, and increased pressure to push liquid through tubing.  The water itself is kept cool with simple
technology – a bag filled with ice and a pump to circulate the fluid. As the
fluid returns to the heat exchangers, the heat is transferred through a thin
layer of generated ice that gets vaporized into space.

In
addition to LCVG, the spacesuit is capable of cooling the astronaut through
evaporative cooling. Evaporative cooling is the process of converting liquid
into vapor using the thermal energy in the air, resulting in a lower
temperature. In the case of the spacesuit, the thermal energy is the heat
generated by the body.

Since
the LCVG operates by circulating water though the garment, the spacesuit has to
be capable of maintaining the liquid state of the fluid. It is rare for water
to exist in the universe as it does on Earth, in liquid form. Water can only be
a liquid in specific conditions: it turns into a gas at 100 degrees Celsius,
and freezes at 0 degrees Celsius. On earth, at higher altitudes water can boil.
In the environment of space, where there is no pressure, water can boil
instantly. Therefore, the spacesuit has an internal pressure system to keep the
fluid in the LCVG, and the fluid in the human body in liquid form. Pressure
contributes to making sure the astronaut does not boil alive! The suit acts
like an inflated tire, that is restricted by the casing of the suit. The
pressure in the suit is maintained at .29 atm by filling the suit with air on
the spaceship and sealing the air with a pressure-sealing neck ring. A diagram
to maintain water in liquid form can be found in Figure 2 below.

Figure
2: Conditions needed for water to
remain in liquid form

Now,
due to the thirteen layers that makeup the spacesuit, the spacesuit is well
insulated to keep heat within, and has a well designed LCVG to keep the
astronaut cooled. To understand how the LCVG and insulation, work together to
contribute to heat regulation, the concept of a heat sink must be explained.

A
heat sink is an object that disperses heat from another object. The heat sink
makes use of the Second Law of Thermodynamics, which states that entropy of the
entire universe, as an isolated system will always increase over time. The
second law also states that the changes in the entropy in the universe can
never be negative. This Second Law of Thermodynamics is the primary explanation
for why heat always travels from hot to low temperature until equilibrium is
met. A heat sink is always a cooler object that serves to take heat away from
the primary object.

While
the spacesuit is designed to remove heat from the astronaut, it is not
necessarily as obvious how heat is being generated. In the case of the space
suit, heat is generated primarily from the human body. As mentioned previously,
space has a cosmic background temperature which is negative 250 degrees
Celsius. It takes time for radiation to travel through the vacuum of space, at  3.0 x 108
meters per second. Therefore, an astronaut is the warmest object for 300,000,000
meters, each second! As a result, the vastness and coldness of space is the
effective heat sink. The body generates heat which is insulated within the 13
layers. The LCVG has tubes to regulate heat dissipation for the comfort of the astronaut,
and any excess heat is lost to the surrounding cold cosmic background
temperature.

The
design of the EMU, while efficient, does provide some inherent dangers for the
astronaut. Since heat generation depends only on the human heat generation, if
any part of the spacesuit breaks, the astronaut is subject to the frigidness of
the cosmic background temperature over overheating. A counter measure for overheating,
is for an astronaut to touch any object. Since the astronaut is the primary
heat generator for the space suit, if the astronaut touches a colder object,
such as the outside of the spaceship, the colder material touched will also act
as a heat sync.

Heat
can also be removed from the outer layers of the spacesuit. Since the astronaut
may still be exposed to warm temperatures, the spacesuit itself is designed to
reflect sunlight, and hence reflect radiation. The outmost layers of the suit
such as the helmet and upper and lower torso, are covered in Mylar or a
reflective white sheet. However, this design is only limited protection from
radiation and con not protect the astronaut from solar flares. As a result,
astronauts intentionally minimize the time they are exposed to solar activity.

The
spacesuit is an amazing heat transfer design accomplishment. Scientists
understood the fundamentals of the cosmic background temperature, and the
radiation generated from stars. Knowing that heat is sparse, due to the gas
molecules being too far and few in-between to be influenced severely by the
heat generated from insulation, intelligent scientsists knew that the astonuat
would be the only object generating heat for hundred of kilometers. To
accommodate for this, the spacesuit was designed to insulate heat generated
from the human body. Then, the LCVG contained small tubing with water to
regulate the heat generated from the body, to make sure the astronaut can
remain healthy and safe within the spacesuit. This design also made use of the
giant heat sync surrounding the astronaut, the cosmic background temperature,
and making sure any excess heat can be radiated away to the environment. In
addition to this, the astronaut was protected from boiling alive by maintaining
an internal presser o keep all fluids in liquid form. The outermost layer of
the spacesuit has reflective material to keep as much radiation as possible
away from the astronaut, so that they do not overheat. All of these components contribute
to how the spacesuit is a wonderful scientific feat, especially in terms of heat
transfer.