|Preparing for a Walk In Space|
|http://www.sina.com.cn 2004/09/03 13:37 新浪教育|
EXPLORATIONS - Preparing for a Walk In Space
By Paul Thompson
Broadcast: June 4, 2003
This is Ray Freeman.
And this is Steve Ember with the VOA Special English program EXPLORATIONS. Today, we tell about how astronauts prepare to leave the safety of the International Space Station and work outside in the very dangerous environment of space.
All astronauts who have worn protective clothing and left a spacecraft to work in space have told about the beautiful sights they see. While working in space they can see most of the Earth as their orbit carries them around our planet. In the stillness of space, it is easy to forget that they are traveling at several thousand kilometers an hour. The great beauty they see makes it easy to forget that they are working in an extremely dangerous environment.
American Astronaut Don Pettit recently returned to Earth as a member of crew number six of the International Space Station. He returned to Earth with American Astronaut Ken Bowersox and Russian Cosmonaut Nikolai Budarin. Mister Pettit was the International Space Station science officer. He and the other crewmembers spent almost six months in space. During that time Mister Pettit wrote several reports for the American space agency about his experiences.
One of the most interesting reports is about what the crew members must do to prepare to leave the space station and work safely in space. Doug Johnson reads the words of American Astronaut Don Pettit.
Have you ever seen a movie about crewmembers on a spacecraft who have to go outside to fight evil creatures or repair a hole in their spacecraft? They quickly put on their space suits and leave the ship in just a few seconds.
Well, maybe in the distant future we may be able to do it that quickly. However, getting ready to leave the safety of the International Space Station can take as long as one week. Nothing happens fast while preparing for a trip outside the space station.
The first thing you must know is that no mistakes can be made. Space is an extremely dangerous environment. Making a mistake in space is not like making a mistake on a school test. A mistake in space can cost you your life.
The major problem with preparing to go outside is the huge amount of work that must be completed. There are many small details but each is very important.
For example, many rubber rings are placed between each part of the space suit as it is linked together. Each of these rubber rings helps prevent air from leaking out of the protecting clothing. Each of these rings is very important and must be inspected. Damaged rings must be replaced.
Don Pettit says the first major job that must be performed is cleaning the small room that is the link between the space station and outside. The astronauts are careful about cleaning the room because they do not want anything to move into space by accident. A forgotten tool or object could cause severe damage or block their work.
This small room is called an airlock. It has two doors -- one to the inside of the space station and the other to the outside and space. But as Astronaut Pettit explains, leaving the space station is still several days away. He explains how the space suit is carefully put together.
The space suit comes in many parts. We keep it in a special case. We have a huge book that lists all of the parts and each of the tasks that must be done. It takes a great deal of time to read each step that must be performed and to attend to each detail. First, there are the batteries that will supply the electric power to the equipment in the suit.
The batteries supply power for the lights on the helmet that covers the astronaut’s head and a video camera on the helmet. Another battery supplies heat to the special gloves that cover the hands. The heat is needed to protect our hands from the fierce cold of space.
The many batteries are inspected and connected to the power supply of the space station. It can take several hours for the batteries to receive the full amount of electricity. You do not want to be outside and have a battery fail.
Next we work on the equipment that will permit us to breathe. All humans produce carbon dioxide when they breathe. This natural gas must be taken out of the air supply we carry.
A special device in the breathing equipment takes the carbon dioxide out of the air. This device has a special chemical that must be heated in an oven for about fourteen hours before it can be used. This is an extremely important job.
Each piece of equipment, each device, each link must be inspected. When the testing and inspecting are done, we put on the space suit for more tests. The book has a list of tests that must now be performed. Everything is carefully tested following the instructions in the book. If everything works as it should, the tests and inspections are complete.
In the movies, an astronaut puts on his space suit and is ready to go. As Don Pettit says, it is not that simple for real astronauts. It is impossible for one person to put on all the necessary protective clothing before going into space. Everyone needs help. Don Pettit says that like most tasks in the International Space Station, putting on a space suit is a team effort.
At the beginning of a space walk day, we ride an exercise bicycle. We do this wearing a breathing device that provides one-hundred percent oxygen. The atmosphere inside the space station is the same as that on Earth. The atmosphere is twenty percent oxygen and eighty percent nitrogen. Air pressure inside the space station is the same as it is on Earth. However the space suit we must wear outside does not have the same air pressure.
If there were any nitrogen in our bodies it would cause severe problems if we quickly went from one air pressure to the other. This problem is called “the bends.” Deep-sea divers must deal with the same problem. So, we breathe one-hundred percent oxygen until it forces all of the nitrogen from our bodies. We will continue to breathe only oxygen while we are in the space suit.
Now we begin the task of putting on the space suit. A crewmember helps with the many connections, links, locks and other equipment on the space suit. Many of the connections make a nice clicking sound when they are linked together correctly. We carefully listen for that sound. Our lives depend on it. Like all of our other jobs, putting on the space suit is done using our list of instructions. Nothing is left to chance. Getting dressed in a space suit takes about six hours from the time you start in the morning to the time you are ready to open the door and step out into space.
The crewmember who is helping the astronaut with the many parts of the space suit has one last job to perform. The astronaut going outside is fitted with a special device that is linked to the back of the space suit. This device is filled with high-pressure nitrogen gas.
It permits the astronaut to fly back to the space station if he were to accidentally move too far away from the spacecraft. Moving too far away from the space station without this device would be a deadly mistake. Nothing could be done to bring the astronaut back to the space station.
The crewmember now helps the others safely enter the room that will permit them to enter space. Again, everything is tested. Then the door to the International Space Station is tightly closed and locked. Don Pettit explains what happens next.
Slowly, the air inside the little room is released into space. After all of the air is gone, the door to space is opened. My first time going outside, the door would not open completely.
It just would not open. After all the work we did getting ready we thought we might have to go back inside. We could even see the extremely bright light of the sun showing through the small opening on the edge of the door. It was only a small piece of rubber that kept the door from opening. At the last moment, it did open and we stepped out into space.
It really was worth the hard work. Working outside the space station is a beautiful experience. However, if this were a movie about chasing bad guys in space, I am afraid they would have gotten away long before we were ready.
This program was written by Paul Thompson and produced by Mario Ritter. Doug Johnson was the voice of Astronaut Don Pettit. This is Steve Ember.
And this is Ray Freeman. Join us again next week for another EXPLORATIONS program in Special English on the Voice of America.
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