------Program code: NS-080512-03648 (what's this?)
Source: CCTV.com
05-12-2008 11:42
People have admired birds since ancient times. This has also prompted a desire for human beings to fly. They tried to satisfy this dream by inventing the kite as well as fairy tale characters that can fly. But the person who really made a serious effort to fly was someone in the Ming Dynasty. He sat on a chair with 47 rockets bound on it, and asked his servants to light the rockets, hoping to fly to the sky upon the rocket’s thrust.
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It failed, to say the least. Then how can people realize their dream of flying?
When people throw an object, the speed is closely connected with the distance at which it is cast. The greater the force, the higher the speed, and thus the further it goes.
Some boldly assumed that upon reaching a certain speed, full flight would be possible. It would fly around the Earth continuously without falling down. In that case, what speed is it supposed to be? After doing various calculations, scientists came up with an answer.
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Modern rockets of high thrust managed to reach a speed of 7.92 kilometers per second. On October 4th, 1957, the former Soviet Union launched the first man-made satellite, which was 900 kilometers above the ground and flying at a speed of 8 kilometers per second. This was the first time that people sent an object into the space at so high a speed.
On April 24, 1970, China launched the first satellite “Dong Fang Hong 1”. From then on, China have launched 15 different kinds of satellites, including communication, meteorological, recoverable, remote sensing and scientific experiment satellites, and contributed a lot to the development of human society.
When the rocket sends the satellite into the projected orbit, they’ll separate, leaving the satellite flying on the orbit without thrust from the rocket. That’s to say, the satellite at that time, can suspend in the space even if there is no force to keep it. Because the rocket has promoted its speed to over 7.92 kilometers per second right before it enters the orbit.
