Md Sadat Hussain Rafsanjani :Astronaut, also referred in Russian as cosmonaut, taikonaut for Chinese spaceman, spationaut in French or vyomanaut in India is a trained person who serves as the pilot or crew of a spacecraft for earth orbiting or space exploration program. The term is not confined to a pilot or commanding person of the ship any more but applicable anyone who can stay on the board or make a space flight in exchange of money, scientific exploration or research. Thus not only professional space flight crews but also who takes the space walk like a business tycoon or a politician is regarded officially as an astronaut. The term first appeared in science-fiction stories back in 1929 but got popularity after 1959 space program. NASA initially wanted to coin different term mercury to refer a space traveller after the Roman God but as ill luck would have it, the name never got recognition. Contemporary term have similar meanings for instance, Astronaut means ‘sailor among the stars.’ Similar term cosmonaut means ‘sailor of the universe.’ Taikonaut refers to ‘great emptiness.’However the effective altitude reached by a person is a matter of greater importance to certify him or her as an astronaut. The atmosphere is divided into several spheres or layers. Each layers ha s a definitive name and use. Troposphere starts at 6km above the ground level and expands to 20km; usually airplanes and commercial jets use this layer. Above the troposphere, the next layer is named Stratosphere, weather balloons roams I this layer, expands up to 20km. The Mesosphere is about 85km long; meteorite and space particles whenever enter the earth atmosphere, burnt out in this layer. Te Thermosphere is 690km long in width usually space shuttle roams here and orbits the earth at a fixed velocity. The first 100km is marked as the Karman line, marks the boundary of earth and space. Aurora, a lightening effect also occurs in this layer. Hungarian born physicist Theodore Von-Karman first noticed that, at that level the atmosphere becomes too thin to support the spacecraft wishing to orbit the earth thus extra velocity is required must to orbit the earth at this level to maintain the aerodynamic lift effect. First human built craft to cross the Karman line was V-2 rocket, built during World War-II era, officially, designated as Aggregate-4, a ballistic missile. It was a liquid propellant rocket developed in Germany.According to the Federation of Aeronautique Internationale (FAI), a world governing body organised for constituting air sporting code, any spacecraft if exceeds 100 km is certified and the person on the board who took the walk is recognized officially as an astronaut. But in USA, a person if travel 80km altitudes, is given the mark of space-flight wings called astronaut badge thus officially regarded as an astronaut. The person doesn’t necessarily need to be in military or pilot but any civilian.Astronaut badge can be of two versions; military version is awarded to the military personnel who have taken part in a space-flight program successfully. The military version has four types. The typical design of the insignia consists of a golden shooting star with an elliptical orbit. US army astronaut badge is designated to those who are army aviator, air surgeons or an aircrew. This badge has three degree namely basic, junior and senior. However, a person who has not taken part in a space-flight program yet is awarded army aviation badge. The badge has a silver version designed for army service uniform and a black version worn on army combat uniform. This is the most prestigious and toughest badge to be earned in the US Army. Member of air force is awarded the USAF astronaut badge; the astronaut device is worn in front of the USAF insignia. The mission specialist is a person who aids technical or medical knowledge on the board, a position held by the NASA astronaut generally. However, a USAF member can be a mission specialist, can be rated and mentioned often as observer. The observer has three different categories: observer, senior observer and master observer. A USAF member who has competed training course but has not been a member of a mission or completed a space-flight may get observer insignia.Becoming an astronaut is one of the challenging professions in the world nowadays. It not only takes higher education in science and flight experiences but a lot of physical trainings. In a sense an astronaut is a polymath who possesses vast knowledge of engineering, physical science, natural science, mathematics, biology, mechanical instrument expertise and many more.An astronaut can be a pilot, a mission specialist or a mission specialist educator. However, NASA recruits astronaut only for two positions. The pilot or commander is the chief on the board who pilots the probe. A pilot must be an USAF pilot or must be in the active military service or the air division. Mission specialist assists the commander, maintains spacecraft and executes experiments. The space educator goes through the same training regime but they do not take part actively in the mission rather they train other applicants and inspire them. Any US citizen with a degree in engineering, physics or science from any accredited university can apply for the astronaut program. NASA requires a person with perfect visual acuity in both eyes and blood pressure level is 140 by 90 in sitting positions, height must be five feet two inch up to six feet two inch. The height level slightly differs for the post of mission specialist. Persons who have undergone LASIK surgery are not eligible. The candidate must have a bachelor degree in any of the engineering field or natural science. For piloting the probe, a person must be a pilot as well as 1000 hours of flight experience at least although test pilots are acceptable.There are many training phases involved in building an astronaut. As space travel is a sensitive and challenging profession, special forms or trainings are received by persons who are enrolled in the space-flight training program. An eligible candidate after getting selection reports to the Johnson Space Centre, NASA’s prime facility to train candidates, located in Houston, Texas. The site is named after the late president Lyndon Johnson, a native. This course lasts for two years almost. The training is categorised in three stages and three perspectives. Technical training helps to learn the astronaut new found skill and problem solving mechanism. At least, two person on the board must be able to identify mechanical malfunction and able to solve them with ease. Medical knowledge is essential for treatment and first aid. Personal training teaches to cope with the space station environment as well as the psychological assistance. As the space station is very small, confined place, limited movement can lead to depression, anxiety and unstable mental health. So, special instructions are instructed to the applicant to adapt with the situation. The last but not the least, group training is the core part of space-flight training program as they are immersed in a simulation. They need to up and running their life support system on and maintain the balance in the gyro sphere. The first stage employs theory classes. It helps the student to get acquainted with the space station. They receive further knowledge in mathematics, physics, earth science, meteorology and space science. The candidate also undergoes survival training in preparation for crash landing. They receive swimming training unless get a pass in scuba diving. A 25-metre pool must be passed by swimming three times without stopping and then. This must be completed in the first training month. The second stage starts after the eligible candidate pass the entire course taught in the first stage. They are assigned a former astronaut as a mentor who shares knowledge and skills with the novice. The last ten-month is called the advanced stage. Here final candidates receive weight less training program under a deep-water pool. It is called Neutral Buoyancy Laboratory or NBL, a 200-feet long and 40-feet deep pool filled with 6.2million gallon water. Under this facility, a person is trained to cope with the weightlessness feeling. They must be trained for both space travel and specific mission objectives.NASA has many other training facilities, devised for specific purpose. The Jake Garn Training Facility serves as the in-orbit training simulator to train an astronaut. The Space Vehicle Mockup Facility trains for space station operations. It is an exact full size replica of the international space station that provided as much realism as possible. At Marshall Space Flight Centre the virtual reality laboratory is used to simulate the space-walk and robotic arm operation performed by the candidate. It is very essential to take this training properly as in the space orientation of up and down is different and hard to control.When taking a space-walk or working in the space, the astronaut is required to wear a extra-vehicular mobility unit that works as the life support in the extreme condition of the space. It contains eight-hour life support facility and thirty-minute backup support of oxygen, air pressure of 4.3psi maintained by the PLSS or primary life support system. The PLSS keeps the suit pressure, removes carbon dioxide and humidity and cools the spacesuit interior. It has an in-built two-way communication device, telemetry for the suit functions. The suit has two part, a torso and lower part, can be worn easily. There are two different types of suit currently being worn by astronauts, one is made of USA and another one is from Russia. Due to micro-gravity in the low orbit and zero gravity in the space, life is different in the sky. Weightlessness causes bone and muscle density deterioration. Astronaut eats dry food to reduce the bacteria development and keep the food stored for long period of time. Whenever they take meal, they just add water to the food to make it soft to consume. Hot food is restricted as they can float and give nasty burn on the skin. Also listening to the nature is the most awkward situation in the space. The toilets are designed specially. The solid waste are collected and flashed to a container with air to store. The liquid waste is collected and dumped at the space. Bathing is not possible in the space thus astronaut use soap sponge to wash their body and washcloth to remove the soap. Some station also has specially designed room to take bath with water by spraying. n
