Chapter 1091 Satellite Attitude Maneuvers

October 15, 2003.

Early morning, 0:30.

Dongfeng Space City.

In the northwest in mid-October, it was late at night, and the temperature had already shown a little chill.

Chang Haonan, wearing a coat, stood in the slightly deserted hall of the command and control center.

At this time, it was less than nine hours before the launch of Shenzhou V, and many staff members were still inspecting the equipment again and again, and did not appear here.

And 1,500 meters away, the lake blue launch tower stood tall and pointed to the sky. The three sets of rotating platforms were like powerful arms, hugging the nearly 60-meter-high Long March 2F Yao 5 carrier rocket.

Of course, for safety reasons, the control center did not have windows directly leading to the outside.

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

However, the ship-rocket combination was not the focus of his observation.

In fact, he was originally planning to return to the capital after the last full-course joint training two days ago, and personally command the Qingluan constellation to perform attitude maneuvers at the Tanzhou tracking and control station.

After all, he really couldn't play any direct role in the Aerospace City.

In the end, it was the superiors who made the decision, saying that Comrade Chang Haonan, as a senior commander and basic R&D personnel of the project, could not play a direct role even in Tanzhou when the satellite had already been launched, so it would be better for him to stay in the launch center with the other subsystem leaders as usual.

Chang Haonan certainly knew that the organization intended to let him witness this iconic moment for all of China.

But then again, there was nothing wrong with what the superiors said.

He was not a professional orbit controller, and no matter how capable he was on the ground, he could not do anything about the spacecraft that had already entered orbit.

So, he stayed.

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

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

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

At the same time, there were also instructions from the Tanzhou station.

To some extent, it was equivalent to a "live broadcast" using a luxury dedicated line.

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

"Is the attitude maneuver of the relay constellation about to begin?"

At some point, Shen Junrong had come behind Chang Haonan.

As the general manager of the measurement and control system of the manned space engineering, he actually faced the same situation as Chang Haonan in the last period before the launch.

Rationally, he felt that he had to do something.

But the front-line tasks and personnel allocation were all optional, and if he, an old man, got in, it might be counterproductive.

So he simply came to Chang Haonan's place, ready to talk to someone and relieve his anxiety.

Chang Haonan nodded, but his eyes did not leave the big screen in front of him:

"There is still half an hour, and 02 satellite will enter the attitude maneuvering 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 attitude and position determination of small satellites are highly dependent on magnetometers. For the sake of orbital accuracy, it is still necessary to avoid performing actions in high latitudes as much as possible.

So, the time window left for each satellite is not large.

In several corners slightly away from the two, dozens of media staff were fiddling with their equipment.

Although the live broadcast plan was officially abandoned during the last joint rehearsal, 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 the same day, reviewing the entire launch process in a fully recorded manner.

And it's not just that.

The time of the program broadcast will just catch up with the spacecraft entering the 8th and 9th laps.

That is, the most suitable stage for relay communication testing in the plan.

Therefore, after reviewing the launch-orbiting process, the program will seamlessly connect to the quasi-live broadcast with a delay of 8-10 minutes, directly showing the situation inside the spacecraft to people all over the world.

In this regard, Shenzhou V has one advantage.

That is, the astronauts will not enter the orbital module throughout the process, but will stay in the return module with a lower sensitivity.

Therefore, the content that needs to be cut is mainly limited to some voices during the call between the earth and the sky, rather than the pictures.

This also saves the trouble of coding in the middle.

It can be said that the only problem next is whether Chang Haonan and his "Qingluan" constellation can stably maintain sufficient relay communication time...

...

At 1:00 a.m., Qingluan 02 was the first to enter the pre-planned maneuvering range.

"Attention, all units, according to the orbital monitoring calculation of Gaojing, the target aircraft attitude adjustment path is confirmed below..."

The voice of Zhang Weiyong came from the headset.

Controlling a satellite is not like driving a car, and it is definitely not for technicians to directly operate it with a steering wheel or a joystick, but to enter instructions in the control program and then execute them by the satellite.

And now, it is the last confirmation before the instruction is issued.

At this time, Shen Junrong next to him also picked up another headset and put it to his ear.

He was just listening casually, but after a while, 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 a 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. There’s no need to worry about liquid sloshing, right?”

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 going to 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 motioned for 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 that it weakens 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... Therefore, we have tried to apply active vibration suppression technology from the aviation field on the Qingluan series of satellites."

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