Mr. Yu walked to the blackboard and drew a schematic diagram: "That's it. We can completely lower the orbits of several satellites and put them on the middle-earth orbit, so that they can not only bear the balanced load of satellite communications, but also become inter-satellite link relays, and also link relays."
Another old man added: "This is equivalent to moving some gateway main stations to the middle-earth orbit, both taking into account and being flexible, and having the advantages of both networking methods."
"It also has an important role." An old man also said: "We can reduce the launch cost by launching more than one arrow, and then these stars are divided into two layers. The Middle Earth satellite can be used as a backup satellite for synchronous satellites. Once there is a problem with the synchronization satellite responsible for the main communication mission, we can let a Middle Earth satellite perform orbit change operation and transfer it to the synchronous orbit to replace the satellite that has the problem."
"Great..." Zhou Zhi now felt like he was reading a good poem and hearing a good song. This new solution was simply amazing.
The orbit of the Zhongdi satellite is 2,000 to 20,000 kilometers, and the orbit of the synchronous satellite is 35,000 kilometers. The distance between the two seems to be 15,000 kilometers, which is a very long distance.
However, this distance of 5,000 kilometers is not as difficult as everyone imagines.
There are two mechanical principles here: the principle of centrifugal motion and the principle of variable speed circular motion.
The satellite moves uniformly at a circular motion in the original orbit. If the ignition accelerates at a certain point, the moving orbit will become an elliptical orbit and the orbit radius will become larger.
When the satellite moves to perigee in low orbit, the ignition accelerates. Since the satellite's speed increases at this time and the gravity does not change, the satellite changes from its original uniform circular motion to its centrifugal motion, entering a new orbit that is stretched into an ellipse, called the "transfer orbit".
As the satellite continues to move away from the earth in its new orbit and needs to overcome gravity, the satellite's speed will become slower and slower. This is like when we throw an object upward, it will slow down due to overcoming gravity during the ascent.
When the satellite moves to the apogee of the transfer orbit, the movement speed drops to a smaller level, and the gravity is relatively large, the satellite begins to move near-centerly towards the direction of the earth, and under the pull of gravity, the speed becomes faster and faster.
When the satellite moves to perigee again along the transfer orbit, it ignites the satellite and accelerates it. If this speed can balance gravity and centripetal force, the satellite will complete orbit change.
Of course, sometimes it is not possible to ignite one or two times. For example, later Chan'e-1 had to reach the lunar orbit 385,000 kilometers away from the earth, and had undergone a total of four orbital changes.
As a large spacecraft, there is no problem doing this, but as a medium-sized satellite with a load of one or two hundred kilograms, Zhou Zhi couldn't help but become curious: "Old Yu, how can the fuel for changing orbits be solved? Will it consume a large amount of the satellite's payload?"
"I wonder if you have cared about the first prize of the National Science and Technology Progress?" Yu asked.
Speaking of this Zhou Zhi, he couldn't help but feel a little proud: "Hanwen Big Font Library won this award."
Yu Lao was happy. He also forgot that there was this in Zhou Zhi's background information, and nodded and smiled, "But I'm talking about the time in 1987." "Lanzhou 510 Space Physics Research Institute was the first unit in China to carry out research on electric propulsion technology. It began to develop ionic electric thrust system as early as 1974. By 1986, it developed 80mm mercury ionic electric propulsion. This achievement won the first prize of National Science and Technology Progress in 1987, reaching the international leading level. The product level is not weaker than that of the United States, which has been engaged in this field since the 1950s."
"Electric propulsion? Ion?" Zhou Zhi felt that these things should be almost the content that appeared in space science fiction novels. I really don't know that the current space technology is so advanced.
"Ion propulsion is a type of electrical propulsion. Its characteristics are small thrust and high specific impact. It is widely used in space propulsion, such as spacecraft attitude control, position maintenance, orbital maneuver and interstellar flight. "An old man may be an expert in this field, explaining to Zhou Zhishen: "The principle of ion propulsion is very simple, which is to use electrical energy to ionize the working fluid to generate ions. The ions are accelerated and ejected under the action of an electrostatic field, thereby generating thrust."
"Theoretically, there is no energy loss during the acceleration process, so the efficiency is high. With an acceleration voltage of 1,000 volts, a specific impulse of thousands of seconds can be obtained. This propulsion method is actually an electrical propulsion with the earliest research and development time and relatively sufficient ground and space flight tests."
"The thruster that Yu just said that the award was only 80 mm? How much thrust can it generate?" Zhou Zhi felt incredible: "This force can make the satellite upgrade 15,000 kilometers?"
"It's true." The old man who just claimed that he could achieve satellite orbit change smiled and said, "The characteristics of the ionic electric propulsion engine are as you guessed, acceleration is as follows: Both the force and acceleration are very low, like ours, only a few dozen millinewtons and a few centimeters per square second. This thrust can only blow a piece of paper. "
"But unlike the extremely short combustion time of a chemical rocket, the acceleration time provided by an electric propulsion rocket can be very long, so the engine is relatively large, that is, using the same mass of working fluid can provide greater total thrust and final speed. "
"Although it emits only a bunch of charged particles or ions, and the thrust provides weaker, as long as the ion thruster can maintain stable performance for a long time, it can eventually accelerate the spacecraft to a higher speed."
"Because space is originally a vacuum and light gravitational state, it only takes a small amount of force to allow the spacecraft to obtain acceleration. As long as this acceleration always exists, even if it is very small, as long as it takes a long time to accumulate to achieve an extremely high operating speed."
Anyone who has studied junior high school physics can easily understand this. If this is the case, satellites do not need to carry chemical fuel at all. They only need to carry light compressed gas as working fluid, and then use the electrical energy generated by the solar windsurfing plate to excite the satellites.
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Safe, lasting, long-term, and has many benefits. "I'm really ignorant." Zhou Zhi grinned and said, "So our satellites are going to use this thing?"
"This is Academician Zhang Shuqiu, an expert in our country's ion electric propulsion system." Old Yu pointed to a person and introduced: "Let him pour you bitterness." "Although we achieved a breakthrough in mercury ion propulsion in 1987, since the United States did not start to apply, the country has always had doubts about this project and finally decided not to engage in research on ion electric propulsion systems." Zhang Shuqiu couldn't help but say: "But the comrades from the Institute of 510 are reluctant to let it go, and they are optimistic about the future development prospects of this technology. Therefore, they did not disband the scientific research team. Instead, they maintained research through self-raised funds in the past nine years, and successfully developed a 90mm xenon ion electric propulsion system in 1993!" (This chapter ended)