Riding the wind of rebirth

Mr. Yu walked to the blackboard and drew a diagram: "That's it. We can lower the orbits of several satellites a little bit and put them in medium-Earth orbit, so that they can not only bear the balanced load of satellite communications, but also become intersatellite link relays and link relays at the same time."

Another old man added: "This is equivalent to moving part of the gateway terminal to the medium-earth orbit. It is both comprehensive and flexible, and has the advantages of both networking methods."

"There is another important function." Another old man also said: "We can reduce the launch cost by launching multiple satellites with one rocket. Then these satellites can work in two layers. The central satellite can be used as a backup satellite for the synchronous satellite. Once the synchronous satellite responsible for the main communication mission has a problem, we can let a central satellite perform an orbit change operation and move it to the synchronous orbit to replace the satellite with the problem."

"It's great..." Zhou Zhi now felt like reading a good poem and listening to a good song. This new plan was simply wonderful.

The orbit of the Central Earth 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 differ by 15,000 kilometers, which is a very long distance.

However, this distance of 15,000 kilometers is not as difficult to overcome as everyone imagines.

There are two mechanical principles here: the principle of centrifugal motion and the principle of variable speed circular motion.

The satellite performs uniform circular motion in its original orbit. If it is ignited and accelerated instantaneously at a certain point, the orbit will become an elliptical orbit and the orbit radius will increase.

When the satellite moves to the perigee in a low orbit, it ignites to accelerate. Since the satellite's speed increases at this time, and the gravitational force does not change, the satellite changes from the original uniform circular motion to centrifugal motion, and enters a new orbit that is elongated into an ellipse, called a "transfer orbit."

As the satellite continues to move away from the earth in its new orbit, it needs to overcome gravity, and its speed becomes slower and slower. This is like when we throw an object upwards, it will slow down during the upward process because it has to overcome gravity.

When the satellite moves to the apogee of the transfer orbit, its speed decreases to a relatively small value, and the universal gravitation is relatively large, so the satellite begins to move pericentrically toward the earth, and under the pull of gravity, its speed becomes faster and faster.

When the satellite moves to the perigee again along the transfer orbit, it is ignited and accelerated again. If this speed can balance the gravity and centripetal force, the satellite will complete the orbit change.

Of course, sometimes one or two ignitions are not enough. For example, the later Chan'e-1 wanted to reach the lunar orbit 385,000 kilometers away from the earth, and it made a total of four orbit changes.

There is no problem with doing this for a large spacecraft, but for a medium-sized satellite with a payload of 100 to 200 kilograms, Zhou Zhi couldn't help but become curious: "Mr. Yu, how do you solve the problem of fuel for orbit change? Will it consume a large amount of the satellite's payload?"

"I wonder if you have ever cared about the National Science and Technology Progress First Prize?" asked Mr. Yu.

Zhou Zhi couldn't help but feel a little proud when talking about this: "Hanwen Font Library has won this award."

Old Yu was amused. He had forgotten that Zhou Zhi's background information contained this information. He nodded and smiled, "But I was talking about the time in 510." "The Lanzhou 1974 Space Physics Institute was the first institution in China to conduct research on electric propulsion technology. As early as 1986, it began to develop an ion electric thrust system. In 80, it developed an 1987mm mercury ion electric thruster. This achievement won the first prize of the National Science and Technology Progress Award in 50, reaching the international leading level. The product level is not inferior to that of the United States, which has been engaged in research in this field since the s."

"Electric propulsion? Ions?" Zhou Zhi felt that these things should be the content that appears in space science fiction novels. He really didn't know that today's space technology is so advanced.

"Ion thrusters are a type of electric propulsion, characterized by low thrust and high specific impulse. They are widely used in space propulsion, such as spacecraft attitude control, position keeping, orbital maneuvers, and interstellar flight." An old man, who might be an expert in this field, explained to Zhou Zhi and his friends, "The principle of ion propulsion is very simple. It uses electrical energy to ionize the working fluid to generate ions. The ions are accelerated and ejected under the action of the electrostatic field, thereby generating thrust."

"In theory, there is no energy loss during the acceleration process, so the efficiency is high. At an acceleration voltage of one thousand volts, a specific impulse of several thousand seconds can be obtained. This propulsion method is actually the earliest type of electric propulsion developed and has been fully tested on the ground and in space."

"Mr. Yu just said that the winning thruster is only 80 millimeters? How much thrust can it generate?" Zhou Zhi found it unbelievable: "This little force can raise the satellite's orbit to 15,000 kilometers?"

"That's true." The old man who had just claimed that he could change the satellite's orbit smiled and said, "The characteristics of the ion electric propulsion engine are just as you guessed. The acceleration force and acceleration are very low. Ours is only a few tens of millinewtons and a few centimeters per square second. This kind of thrust is just enough to blow a piece of paper."

"But unlike the extremely short combustion time of chemical rockets, the acceleration time provided by electric propulsion rockets can be very long, so the engine specific impulse is very large, that is, with the same mass of working fluid, it can provide greater total thrust and final speed."

"Although it only ejects a beam of charged particles or ions, the thrust it provides is relatively weak, but as long as the ion thruster can maintain stable performance over a long period of time, it can eventually accelerate the spacecraft to a higher speed."

"Because space is originally a vacuum and has light gravity, only a small amount of force is needed to accelerate a spacecraft. As long as this acceleration exists, even if it is very small, as long as the effect time is long enough, it can accumulate into an extremely high running speed."

This is easy to understand for anyone who has studied junior high school physics. If this is the case, satellites do not need to carry chemical fuels at all. They only need to carry lightweight compressed gas as a working fluid, and then use the electricity generated by solar panels to excite the satellites to obtain power.

Safe, durable, long-lasting, and has so many benefits.

"You are really ignorant." Zhou Zhi grinned and said, "So our satellite is going to use this thing?"

"This is Academician Zhang Shuqiu, an expert in ion electric propulsion systems in our country." Yu pointed to a man and introduced him, "Just listen to him complain to you."

"Although we achieved a breakthrough in mercury ion propulsion in 87, the United States had not yet started to apply it, so the country had always been skeptical about this project and finally decided not to engage in research on ion electric propulsion systems." Zhang Shuqiu couldn't help but sigh: "But the comrades of the 510th Institute were reluctant to give up and were optimistic about the future development of this technology. Therefore, they did not disband the scientific research team, but maintained the research through self-raised funds for nine years, and successfully developed a 93mm xenon ion electric propulsion system in 90!" (End of this chapter)