Thursday, 6 October 2016

Technical Blog 2

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

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