Heat solar flares (solar particle events); and galactic

Heat
Transfer is the study of the movement of thermal energy from one object to
another object of different temperature. When considering heat transfer
technologies, many may consider examples such as battery cooling, soldering,
brazing, solar panels and turbines. However, the study of heat transfer and
heat transfer design heavily contributes to the design of spacesuits.
Spacesuits are required to keep an astronaut safe in the harsh environments of
space; an environment that is completely lethal to human beings without proper
engineering. With the help of heat transfer technology, such as heat sinks, an
astronaut in space can be safely exposed to the dangerous conditions. To
regulate heat, heat syncs are incorporated into three primary components of the
spacesuit that allow the astronaut to maintain homeostasis in the spacesuit
comfortably:  extravehicular activity,
coolant through various tubing, and layered insulation.

To
understand the critical components of a spacesuit, one must first understand what
makes the space environment dangerous for life. Space is a vacuum, meaning
there is no air and no pressure, and this kind of environment allows electromagnetic radiation to travel great
distances without being scattered, which is about 3.0 x 108 meters
per second through a vacuum.

With
the combination of vacuums and electromagnetic waves, space is subjected to
extremely hot and cold temperatures. Understanding how these varying
temperatures interact with objects in space, the concept of “empty space” is
critical. Empty space, is known as the space between the stars, and is
comprised of 99.9% of atoms. Empty space has a cosmic background temperature
which is negative 270 degrees Celsius, and this is the temperature of the
majority of space.  Temperatures only
increase when next to stars, like the Sun, which generate heat through radiation.
However, heat can still travel through the vacuum of space by infrared
radiation. In space, the UV radiation generated is mostly due to the sun.
Radiation can also be generated from particles trapped in the Earth’s magnetic
field; particles shot into space during solar flares (solar particle events);
and galactic cosmic rays, which are high-energy protons and heavy ions from
outside the Milky Way solar system. Due to the frigid nature of the cosmic
background temperature, the various gasses and molecules that do exist in empty
space do not have the energy to bounce around, and heat is sparse despite
radiation heat transfer existing. This combination of the natural frigid state
of space and the heat generated from various stars, such as Earth’s Sun,
essentially means that most of the gas that exists in empty space is too far
and few in between. There are not enough energized particles to bump into each
other, and transfer heat in empty space, despite having numerous starts that
generate heat.

Therefore,
heat transfer boils down to two extremes in space: whether an object is
shielded by the sun or not. If an object is in space, but shielded from the sun,
essentially all heat is radiated away to the cooler cosmic background
temperature. If not shielded by the sun, that same object is exposed to extreme
radiation that would kill any living organism in space that is not properly
protected. Even on earth where 95% of UV radiation is absorbed by
the atmosphere, problems such as sunburns and increasing the risk of DNA and
other cellular damage in living organisms exists.

When considering a spacesuit that must protect an astronaut,
these extreme conditions must be taken into consideration. In addition to
protecting the astronaut from extreme temperatures, the spacesuit has other
components that are necessary for the astronaut to function in space. The suit
is capable of supplying the astronaut with oxygen, since there is no air in
space. The spacesuit contains water for the astronauts to drink and the suit
protects the astronaut from getting injured by small space debris, which have
the potential to travel faster than a bullet. The spacesuit has several pats.
The chest is protected by the Hard Upper torso, made from fiberglass.  There is also a helmet, which is made from a
polycarbonate material, and has a large plastic pressurized bubble that has ventilation
distribution pad. There is a straw for drinking, a camera for recording and a
microphone for keeping communication. 
The Lower torso includes pants boots layers of synthetic polymers such
as nylon, Teflon, Kevar and Nomex. There is a backpack worn called the Primary
Life Support Subsystem, which holds the oxygen for astronauts. A small fan
moves the oxygen from the life support subsystem,  through the spacesuit and life support
systems. The subsystem also provides electricity for the suit. In addition to
this there is the Liquid Cooling and Ventilation and Garment, which cools the
astronauts down. A schematic of the spacesuit can be found below in Figure 1:

insert figure of spacesuit

 

In
addition to considering design features of the space suit, such as stabilizing
internal pressure, mobility, adequate supply of oxygen; the design of a space
suit is largely a heat regulation and heat transfer design accomplishment. For example, just in Earth’s orbit, conditions can be
as cold as minus 156 degrees Celsius. In the sunlight, they can be as hot as 121
degrees Celsius. If an astronaut’s back is facing the sun and the front is not,
the temperature difference can be as much as 135°C. The vacuum in space
increases the temperature too, as heat cannot escape into the surrounding air
as it does on Earth. The vacuum can also free trapped pollutants such as water
vapor, and deposit this water on cool parts of the space suit where it can
cause problems such as shorting electronics. Spacesuits are specially
designed to protect astronauts from the cold, radiation and low pressure in
space. To regulate heat, heat syncs are incorporated into three primary
components of the spacesuit that allow the astronaut to maintain homeostasis in
the spacesuit comfortably:  extravehicular
activity, coolant through various tubing, and layered insulation.