Why does the Shenzhou spacecraft always choose to launch in the early morning? The right time + the right place + the right people →

At 12:51 on October 30, 2024, the Shenzhou 19 manned spacecraft successfully entered space, starting a new space journey.

The launch of the Shenzhou 19 manned spacecraft was a complete success

Looking back at the launch history of the Shenzhou series of spacecraft, it is not difficult to find that the Shenzhou spacecraft often chooses to "set off" in the early morning, and many manned spacecraft of the United States, the former Soviet Union and other countries are also launched in the early morning. Why is this?

Time

As we all know, space launch is an extremely complex and huge system engineering. Any small error may lead to serious consequences. Therefore, choosing the right time for launch is crucial. And "time" is one of the most critical factors affecting the success or failure of a launch.

Based on comprehensive consideration and judgment, scientific researchers finally determine a certain time period of the day as the time for launching the spacecraft. This time period is called the "launch window."

The most important reason why the launch window of the Shenzhou series spacecraft is chosen in the early morning is that the rocket spitting flames is very conspicuous and prominent in the dark night sky. This high-contrast visual effect makes it easier for ground-based optical tracking and measurement equipment to capture the trajectory of the rocket. In contrast, the strong light and background complexity during the day will greatly reduce the accuracy of tracking.

Shenzhou 18 manned spacecraft launched at night

Moreover, in the early morning hours, the temperature is relatively low and the air density is relatively high. Lower temperatures help reduce the volatilization of rocket fuel and ensure full utilization of the fuel, thereby increasing the success rate of the launch. Cloud cover will also directly affect the observation effect of ground optical tracking and measurement equipment. When there are fewer clouds, it is easier for ground equipment to capture the trajectory of the rocket, thereby monitoring and adjusting flight parameters in real time. In the early morning hours, the sky is usually clearer and there are fewer clouds, allowing optical tracking equipment to capture the flight trajectory of the rocket more accurately.

Wind speed is also an important factor affecting rocket launches. Strong winds may cause the rocket to deviate from its intended trajectory or even cause safety accidents. In the early hours of the morning, especially from late night to early morning, the wind speed is usually low and the weather conditions are relatively stable.

Geographical advantage

In addition to meteorological conditions, the ground environment is also an important factor in determining the launch time. Choosing to launch in the early morning can effectively reduce ground electromagnetic interference and ensure the safety and reliability of the launch process.

Nowadays, the development of modern communication technology has brought a large number of electromagnetic signals, which may interfere with the rocket's navigation system and communication equipment. Electromagnetic interference can cause signal distortion, data transmission errors and other problems, and in serious cases may even affect the normal operation of the rocket. In the early hours of the morning, most ground communication activities are at a low point and the electromagnetic environment is relatively quiet. Choosing to launch during this time period can effectively reduce the impact of ground electromagnetic interference on the rocket and ensure the safety and reliability of the launch process.

In addition, during the day, noise and vibration generated by airports, factories, vehicles, etc. may affect the precision equipment at the launch site. In the early hours of the morning, most of these interference sources are stationary, and the environment around the launch site is quieter. In addition, the road traffic volume in the early hours of the morning is small, which makes it easier to implement traffic control measures.

Choosing to launch in the early morning can also reduce the impact on the surrounding environment. Rocket launches produce huge noise and smoke, and these pollutants may affect the quality of life of nearby residents. In the early hours of the morning, most people have already gone to bed, so the noise and smoke have less impact on residents. At the same time, the animals and plants around the launch site are also dormant and are less disturbed.

People and

The Shenzhou spacecraft was chosen to be launched in the early morning, and the physiological and psychological state of the astronauts also needed to be taken into consideration.

Usually, astronauts will go to sleep a few hours before launch to ensure that they are highly focused and alert during launch to deal with various situations that may arise during the launch. Although early morning launches have a certain impact on astronauts' biological clocks, this impact can be minimized through scientific work and rest arrangements and psychological adjustments.

Shenzhou 19 astronauts feel good

In summary, the choice of the Shenzhou spacecraft to launch in the early morning is based on comprehensive considerations of weather, location, and people. If the prediction time is to be accurate to the hour, minute, or even second, it is necessary to combine the space station's orbit, spacecraft orbit parameters, rocket flight trajectory, space warning, and the optimal strategy for the spacecraft's rendezvous and docking with the space station.

With the successful launch of Shenzhou 19, China's space industry has taken another solid step forward. In the future, through big data analysis and machine learning technology, we can more accurately predict the best launch time. In this brilliant starry sky, the Shenzhou spacecraft will continue to write the legend of China's space industry, and China's space industry will continue to forge ahead in the sea of ​​stars, contributing Chinese wisdom and strength to the development of human civilization.

Some information comes from CCTV.com, China Military, People's Daily, etc.

(Scientific reviewer: Liu Yong, researcher at the National Space Science Center of the Chinese Academy of Sciences)