Chapter 1091 Satellite Attitude Maneuvering


    October 15, 2003.


    Early in the morning, 0:30.


    Dongfeng Aerospace City.


    It''s late at night in the northwest in mid-October, and the temperature is already a bit chilly.


    Chang Haonan was wearing a coat and standing in the slightly deserted command and control center hall.


    At this time, it had been less than nine hours since the launch of Shenzhou 5. Many staff were still inspecting the equipment over and over again and did not appear here.


    And 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, hugging the nearly 60-meter-high Long March 2F Yao-5 launch vehicle.


    Of course, for safety reasons, the control center does not have direct access to the outside window.


    Chang Haonan could only see the situation at the launch site through one of the six large screens in front.


    However, the ship and arrow combination was not the focus of his observation.


    In fact, he originally planned 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 the 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 when the satellite was already in the sky. It was better to follow the usual practice and follow the other projects. The system director stayed at the launch center together.


    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 that.


    Moreover, when the times developed to 2003, the communication network in the atmosphere had already developed relatively well.


    Even if he was at the command and control center in Suzhou, he could still see the working conditions of the four Qingluan satellites—


    At this time, it was displayed on another of the six large screens.


    Also presented were instructions from Danju Station.


    To a certain extent, it is equivalent to "live broadcast" using a luxury dedicated line.


    If necessary, he could even contact the other party to issue instructions.


    "Is the attitude maneuver of the relay constellation 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.


    Intellectually, I felt that I had to do something.


    However, front-line tasks and personnel allocation are very fragile. If an old man like him is involved, it may not be helpful.


    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 satellite, the Qingluan constellation itself can also forward control signals, so it is 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 orbit accuracy, it is still necessary to avoid performing operations in high latitudes as much as possible.


    Therefore, 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 the success of the launch mission, Station C will broadcast a special program in the evening of that day to review the entire launch process in a fully recorded and broadcast manner.


    And, that''s not all.


    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.


    Therefore, the content that needs to be cut out is mainly limited to part of the voice during the world call, rather than 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 all units, based on the Haojing orbit monitoring calculation, the attitude adjustment path of the target aircraft will be confirmed below..."


    Zhang Weiyong''s voice came from the headphones.


    Controlling a satellite is not about driving a car, and it is definitely 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.


    And 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.


    Originally he was just listening casually, but not long after, he showed a slightly surprised expression.


    "Your posture maneuver is taking a sinusoidal path?"


    As he spoke, 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 panels or liquid fuel in the tank. The sinusoidal path will have a negative impact in this regard. It’s easier to control.”


    As an expert in this field, the latter certainly understands the differences between different path plans, so Chang Haonan''s answer did not resolve his doubts:


    "But I have seen some of the design parameters of your satellite. It is not the kind of large flexible structure satellite that is easy to cause divergent vibration. The size and capacity of the fuel tank are very small... and it should be almost full at the moment, so there is no need to Consider the liquid sloshing problem?”


    The trapezoidal path, as the name suggests, simply and crudely provides three constant acceleration values ??during the attitude change process, allowing the spacecraft''s angular velocity to undergo three processes: uniform increase, uniform motion, and uniform deceleration.


    It is the simplest control principle that can be understood after studying high school physics.


    It is also the least likely to cause 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 of 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 just smiled mysteriously:


    "Mr. Shen, you will find out later..."


    Shen Junrong was stunned when he heard this, and then he also smiled.


    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 Star 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 promotional 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 satellite’s movements…


    Then you can only 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 began to be given.


    However, compared with the angular velocity curve, which has a nearly perfect fit, if you look closely at the modal coordinate data, you will find that it contains a lot of irregular fluctuations that look like noise.


    This 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 was coming next—


    In the second half of the posture 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.


    But 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.


    Instead, 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.


    only…


    Even with the size of a 100kg small satellite and the sinusoidal path, this action characteristic is a bit 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 instantaneous mutation from the positive maximum value to 0. In other words, the induced vibration is more regular... So, we are On the Qingluan series of satellites, active vibration suppression technology from the aviation field has been tentatively applied.”


    "And now it seems that the effect is pretty good..."


    (End of chapter)