In my
previous blog post, I gave a general overview of the different problems that
astronauts are faced with while they’re in space. I also gave a brief
description of what measures are taken through the use of technology before,
during, and after spaceflight to try and minimise any harm that may befall them.
In this post I will be going into more depth about the technology used before
spaceflight to prepare an astronaut for when they go out into space.
The first
thing that most people think about when they think of space is the zero gravity
environment. However, space is not a zero gravity environment. It is a
microgravity environment. Gravity works by pulling two objects closer together;
no matter how far apart these objects are, gravity will continue to try and
pull them closer to each other. However, when in space, there are no objects
that are large enough and close enough to have a significant gravitational pull
on an astronaut so the effects are deemed negligible. Hence space is considered
a microgravity environment. Astronauts cannot just be sent into space because
we don’t know how well they will be able to adapt to such an environment. For
example, some people become extremely nauseous under the effects of
microgravity. This would become a major problem if not known about before being
sent into space. Due to this, astronauts prepare themselves in microgravity
simulators on Earth.
The two main
methods that are used to prepare astronauts for the feeling of weightlessness
or microgravity are neutral buoyancy and parabolic flight. Neutral buoyancy
occurs when the average density of a physical body is the same as the density
of the fluid surrounding it. The physical body will neither sink nor float.
Since the densities are equal, the force pulling the body down to make it sink
(gravity) is equal to the force pushing it upwards to make it float (buoyancy).
For astronauts, the fluid usually used to train for this is water. Since water
is slightly more dense than the human body, astronauts wear specially designed
suits which have their weight adjusted, giving them the same density as water.
While wearing these suits, astronauts are made to perform tasks such as moving
bits of hardware around. Since this would require a lot of space and for the
water to be of a significant depth, professional scuba divers are used to
assist the astronauts, making sure that the depth of the water doesn’t have a
negative impact on them. The pool used at the Neutral Buoyancy laboratory in
Houston, Texas has dimensions of 62m in length, 31m in width, and 12.34m in
depth[1]. A major disadvantage of neutral buoyancy is that water
creates a huge amount of drag. This makes it more difficult to move objects and
keep them moving. The objects are also more easily stopped. To minimise these
effects which are the opposite of what would happen in space, any training done
under these effects are done slowly.
Parabolic
flight is also used to simulate microgravity but is nowhere near as much due to
its inefficiency. The plane starts by flying upwards at a high speed and a
steep angle, once it is about to start to level off, it slows down a bit. It
maintains this horizontal motion for around 20 to 25 seconds before going into
a steep nosedive at high velocity again. The simulation of microgravity occurs
when the plane starts to slow down to reach the peak of its parabola and ends
when it goes into a nose dive. Unlike with neutral buoyancy, this method
creates a lot less drag and simulates a more natural feeling of weightlessness.
However, due to the short time frame of only 20-25 seconds, it is also quite
inefficient. One of the first planes used to train astronauts using this method
was the C-131 Samaritan in 1959. The plane was called the “vomit commit”
because this method was known to make people very nauseous and vomit[2].
This was, of course, another disadvantage to this method. It was very costly
and inefficient, but it was also a great way to conduct equipment tests.
In my next
blog post, I will discuss other technologies used when astronauts prepare for
spaceflight and I will also begin discussing the technologies used while in
space by astronauts.
[1] "Extravehicular mobility unit
training and astronaut injuries". Strauss S, Krog RL, Feiveson AH (May
2005).
Aviat Space Environ Med. 76 (5):
469–74. PMID 15892545. Retrieved 05/10/2016.
[2] "Mercury Astronauts in Weightless
Flight on C-131 Aircraft". 2006-08-02. Retrieved 05/10/2016