Chapter 1091 Satellite Attitude Maneuver
2003, October 15th.
Early morning, 0:30.
Dongfeng Aerospace City.
It is late at night in the northwest in mid-October, and the temperature has become a little cold.
Chang Haonan was wearing a coat and standing in the slightly deserted command and control center hall.
At this time, it has been less than nine hours since the launch of Shenzhou 5. Many staff are still inspecting the equipment over and over again and have not appeared here.
1,500 meters away, the lake-blue launch tower stands tall, pointing straight into the sky. Three sets of rotating platforms are like powerful arms, and the nearly 60-meter-high Long March 2F Yao-5 carrier rocket is hugging it. In my arms.
Of course, for safety reasons, the control center does not have direct access to the outside window.
Chang Haonan can only see the situation at the launch site through one of the six large screens in front.
However, the ship and arrow assembly was not the focus of his observation.
In fact, he was originally planning to return to the capital after the last full-scale training two days ago and go to the Tanzhou Measurement and Control Station to personally command the Qingluan Constellation to perform attitude maneuvers.
After all, in Space City, it really can’t play any direct role.
In the end, the superiors made the decision, saying that Comrade Chang Haonan, as the senior commander and basic R&D personnel of the project, could not play a direct role even in Tanzhou after the satellite had already been launched into the sky. It was better to follow the instructions As a rule, stay in the launch center with the leaders of other subsystems.
Of course Chang Haonan knew that this was the organization's intention to allow him to witness this iconic moment for all of China.
But having said that, there is actually nothing wrong with what the superior said.
He is not a professional orbit controller. No matter how capable he is on the ground, there is nothing he can do about the spacecraft that has already entered orbit.
So, I just stayed like this.
Moreover, when the times developed to 2003, the communication network in the atmosphere had already developed relatively well.
Even if he is at the command and control center in Suzhou, he can still see the working conditions of the four Qingluan satellites——
At this time, it was displayed on another of the six large screens.
At the same time, there are instructions from Danju Station.
To a certain extent, it is equivalent to "live broadcast" using a luxury dedicated line.
If necessary, he can even contact the other party to issue instructions.
"The attitude maneuver of the relay constellation is about to begin?"
At some point, Shen Junrong had arrived behind Chang Haonan.
As the general person in charge of the manned space engineering measurement and control system, he actually faced the same situation as Chang Haonan in the last period before launch.
Rationally, I felt that I had to do something.
But the front-line tasks and personnel allocation are all fickle. If an old man like him is involved, it may be a disservice.
So I just came to Chang Haonan, ready to talk to someone to relieve the anxiety in my heart.
Chang Haonan nodded, but his eyes did not leave the big screen in front:
"In half an hour, Star 02 will enter the attitude maneuver range."
As a relay communication Satellites and the Qingluan constellation themselves can also forward control signals, so they are less restricted by measurement and control resources.
However, the determination of the attitude and position of small satellites is highly dependent on magnetometers. For the sake of orbital accuracy, it is still necessary to avoid performing operations in high latitudes as much as possible.
So, the time window set aside for each satellite is not too large.
In a few corners a little away from the two, dozens of media staff were fiddling with the equipment in their hands.
Although the live broadcast plan was officially abandoned during the last joint training process, Chang Haonan's suggestion was still adopted.
After confirming that the launch mission is successful, Station C will broadcast a special program in the evening of that day to review the entire launch process in a fully recorded and broadcasted manner.
And, it doesn’t stop there.
The broadcast time of the program will coincide with the spacecraft entering the 8th and 9th laps.
This is the stage in the plan that is most suitable for relay communication testing.
Therefore, after reviewing the launch-orbit process, the program will seamlessly connect to a quasi-live broadcast delayed by 8-10 minutes, showing the situation inside the spacecraft directly to people around the world.
In this regard, Shenzhou 5 has a good one.
That is, the astronauts will not enter the orbital module throughout the entire process, but will always stay in the less sensitive return module.
So the content that needs to be cut out is mainly limited to part of the voice during the call between heaven and earth, not the picture.
This saves you the trouble of coding in the middle.
It can be said that the only question next is whether Chang Haonan and his "Qingluan" constellation can stably maintain sufficient relay communication time...
...
At one o'clock in the morning, Qingluan 02 took the lead in entering the pre-planned maneuvering range.
"Attention of all units, according to the Haojing orbit monitoring calculation, the following confirms the attitude adjustment path of the target aircraft..."
Zhang Weiyong's voice came from the headphones.
Controlling a satellite is not about driving a car, and it is certainly not about letting technicians directly control it with a steering wheel or joystick. Instead, commands are input into the control program and then executed by the satellite.
Now, it is the last confirmation before the order is issued. At this time, Shen Junrong next to him also picked up another earphone and put it to his ear.
I was just listening casually, but after a while, he showed a slightly surprised expression.
"Your posture is maneuverable, taking a sinusoidal path?"
As he said this, he turned to look at Chang Haonan, who was looking at one of the six screens intently.
This maneuver of the Qingluan system does not involve orbit changes, so the "path" here does not refer to changes at the orbital level, but the relationship between angular velocity and time during the attitude adjustment process.
"Yes."
This sudden question suddenly relieved Chang Haonan's pressure a lot.
He took off his headphones and explained to Shen Junrong:
"Although the trapezoidal path has the highest utilization rate of time and actuator performance, there are sudden changes in angular acceleration, which may affect the satellite's workload, such as solar energy For windsurfing or liquid fuel in a tank, the sinusoidal path will be easier to control in this regard.”
As an expert in this field, the latter certainly understands the differences between different path planning, so Chang Haonan. The answer did not resolve his doubts:
“But I have seen some of the design parameters of your satellite. They are not the kind of large flexible structure satellites that are prone to divergent vibrations. The size and capacity of the fuel tank It is very small... and it should be almost full at the moment, so there is no need to consider the problem of liquid sloshing, right? "
The trapezoidal path, as the name suggests, simply and roughly gives three constants during the posture change process, right? The acceleration value allows the spacecraft's angular velocity to undergo three processes: uniform increase - uniform motion - uniform deceleration.
It is the simplest control principle that can be understood after studying high school physics.
It is also the least prone to problems.
Therefore, although there are many shortcomings, when the conditions are met, the ladder path will basically be chosen.
The integral of the sine function is a cosine function, which means that the change in angular acceleration is more complicated, especially for small MSIs with limited performance of actuators and control mechanisms.
The choice of Qingluan constellation seems to be a bit trouble-free.
But this time, Chang Haonan did not answer immediately, but gave a mysterious smile:
"Mr. Shen, you will find out in a moment..."
Shen Junrong was stunned when he heard this, and also laughed. one time.
Then he stopped talking and put an earphone to his ear again, waiting for Chang Haonan's performance.
While the two were discussing the problem, Qingluan 02 had already begun its attitude adjustment maneuver.
In space, it is naturally impossible to have a camera staring at a satellite.
The small satellite project itself has little publicity value, and we will not make a 3D schematic diagram just for the sake of intuition.
Therefore, what is displayed on the screen at this time is only the attitude angular velocity curve returned by the sensor and the modal coordinate curve.
As for the movements of the satellite...
The only thing you can do is rely on your imagination.
As Zhang Weiyong issued the attitude adjustment command, the ordinate of the angular velocity curve gradually began to grow upward from 0, drawing a sinusoidal function curve on the coordinate system.
Later, the modal coordinates also began to give data.
However, compared with the angular velocity curve, which has a nearly perfect fitting degree, if you look closely at the data of the modal coordinates, there are a lot of irregular fluctuations that look like noise.
That is the flexural vibration that Shen Junrong mentioned before.
However, perhaps because of the sinusoidal path, the amplitude in front of you will not have any impact on the satellite itself.
He could even see that after the satellite's angular velocity reached the maximum value, that is, after the angular acceleration returned to zero, the vibration had entered a convergence state.
Shen Junrong looked at Chang Haonan next to him, not knowing what was special about this.
He even knew what would happen next -
In the second half of the attitude adjustment, the angular acceleration reappears (negative acceleration), and the vibration will be strengthened again.
Until the entire adjustment process is completed, the vibration will slowly return to zero in the next 8-10 minutes or even longer.
But Chang Haonan did not look away. He just pointed at the screen and signaled Shen Junrong to continue reading.
When the latter returned his attention to the curve on the screen, he stood frozen on the spot.
When the angular velocity starts to decrease again, the vibration level shown on the modal coordinate curve does not increase again.
On the contrary, it continues to weaken.
After another 120 seconds, Qingluan 02 finally positioned itself in a new posture.
The vibration of the space-borne accessories completely disappeared almost at the same time...
There was no subsequent gradual weakening process as he expected.
Don’t underestimate this difference.
In addition to affecting the working status of the equipment and the star itself, flexural vibration may also be coupled with orbital translation, thereby affecting the satellite orbit.
If the impact is large, after the attitude adjustment is completed, an orbit adjustment may even be needed to get the satellite into a suitable working condition.
And like the Qingluan 02 star in front of us, the vibration ends almost simultaneously with the attitude maneuver, so this situation can almost be completely avoided.
It’s just...
Even with the size of a 100kg small satellite and the sinusoidal path, this action feature is a bit too outrageous.
Fortunately at this time, Chang Haonan gave a further explanation just right:
“The advantage of the sinusoidal path is not only to weaken the vibration caused by angular acceleration, but more importantly, there is no The instantaneous mutation from the positive maximum value to 0 is eliminated. In other words, the induced vibration is more regular... Therefore, we have tentatively applied active vibration suppression technology from the aviation field on the Qingluan series satellites. "
"And now it seems that the effect is pretty good..."
(End of this chapter)