Why Did Shenzhou-19 Launch at Night? Unveiling the Secrets of the "Launch Window"

Why Did Shenzhou-19 Launch at Night? Unveiling the Secrets of the "Launch Window"While everyone was sleeping soundly, Chinas Shenzhou-19 crew members, Cai Xuzhe, Song Lingdong, and Wang Haozhe, embarked on their journey to the Chinese Space Station aboard the Shenzhou spacecraft. The successful launch of Shenzhou-19 marked the beginning of a new round of missions for the Chinese Space Station

Why Did Shenzhou-19 Launch at Night? Unveiling the Secrets of the "Launch Window"

While everyone was sleeping soundly, Chinas Shenzhou-19 crew members, Cai Xuzhe, Song Lingdong, and Wang Haozhe, embarked on their journey to the Chinese Space Station aboard the Shenzhou spacecraft. The successful launch of Shenzhou-19 marked the beginning of a new round of missions for the Chinese Space Station. However, many people have questioned: Why was Shenzhou-19 launched at night? Why couldn't it launch during the day? After all, daytime seems safer. What's the real story? Let's delve into this topic and review the Shenzhou-19 crews important tasks upon entering the space station.

Shenzhou-19 Launch Successful! Six Astronauts Embark on This Joint Mission

The Shenzhou-19 mission is led by Cai Xuzhe, joined by crew members Song Lingdong and Wang Haozhe. The crew comprises one astronaut from the second batch and two from the third batch. Notably, Song Lingdong and Wang Haozhe are both 90s-born astronauts embarking on their first spaceflight mission. It's worth mentioning that Wang Haozhe is currently China's only female spaceflight engineer and the third Chinese woman to undertake a manned spaceflight mission, making her role particularly significant.

With Wang Haozhe's inclusion, there are now four known female astronauts in China. Besides her, there are Wang Yaping, Liu Yang, and the fourth batch's Hong Kong female astronaut, Li Jiaying. While China typically doesn't disclose astronaut lists in advance, Hong Kong media previously reported Li Jiaying's name. Hence, information about these four known Chinese female astronauts has been revealed. Many people are speculating whether China will form an all-female crew for future missions. There is no definitive answer yet, and we await official announcements for confirmation.

Six Astronauts on the Space Station: Transitioning In-orbit Missions

Upon reaching the space station, the Shenzhou-19 astronauts will join the Shenzhou-18 crew, resulting in a "six-person" crew. This is not a coincidence but a crucial aspect of China's space station missions in-orbit mission handover. This handover process involves:

• Technical Experience Handover: The Shenzhou-18 astronauts conducted two extravehicular activities and implemented safety measures to enhance the space station's protection. Their practical experience, such as conducting extravehicular operations and optimizing safety measures, will be passed on to the Shenzhou-19 crew, providing valuable insights for the smooth execution of future missions.

• Experimental Project Handover: The astronauts conducted various scientific experiments on the space station, some of which may need ongoing research. The Shenzhou-19 crew must thoroughly understand the steps, operational times, etc., of previous projects to ensure their continuation and successful completion.

• Logistics Handover: The space station's resources need regular replenishment. The Shenzhou-19 crew must understand the current resource utilization and distribute them appropriately to ensure sufficient supplies for subsequent missions. Moreover, the Tianzhou-8 cargo spacecraft, which is scheduled to reach the space station, will replenish resources and standardize the space station's layout.

Besides these aspects, other elements, such as space station keys, also require handover. In essence, every aspect related to space station missions needs to be smoothly transitioned between the Shenzhou-19 and Shenzhou-18 crews. Once the handover is complete, the Shenzhou-18 crew will return to the Dongfeng landing site. They are expected to return on November 4th, but the exact time will be confirmed by official announcements.

Why Was Shenzhou-19 Launched at Night?

Following the successful launch of Shenzhou-19, many people questioned the launch time. Why was it launched at night? Isn't it safer during the day?

In reality, launching at any time is a meticulous decision, with safety being the absolute priority. China's manned space missions don't differentiate between night or day launches. The launch time depends on a crucial factor the "launch window."

The "launch window" refers to the optimal time range for a launch vehicle, also known as the width of the launch window. Choosing a suitable launch window is critical for any spacecraft. The Shenzhou-19 launch time was meticulously calculated and precisely adjusted based on the launch window to ensure the spacecraft could successfully enter its designated orbit and dock with the space station.

What is a "Launch Window"?

Determining the launch window requires accurately measuring and predicting the space station's orbit and designing a theoretical launch time. Ground control coordinates with the rocket, aiming to launch as close as possible to the theoretical time. This is the origin of the term "zero-width time window" for spacecraft launches.

After liftoff, the rocket's control system further corrects any remaining deviations during flight, ensuring the accuracy of the orbital injection point. Upon reaching this point, the spacecraft is placed in the same orbital plane as the space station, but at a specific point below and behind it. Subsequently, the spacecraft follows a planned trajectory adjustment strategy to gradually raise its orbit, allowing it to catch up with the space station at the predetermined time.

The orbital injection point represents the designed relative relationship between the two vehicles (altitude difference and positional difference). Different relative relationships require different trajectory adjustment strategies for tracking. The same tracking distance can be achieved through multiple tracking strategies. For instance, a larger proportion of flight time at a lower orbit leads to faster tracking and a shorter overall rendezvous duration.

China's manned and cargo spacecraft have some variations in their strategies, but ultimately, all missions operate within a precise launch window. Therefore, launches aren't arbitrary; the nighttime launch occurred because the launch window coincided with that time.

Shenzhou-20 Stands Ready, Providing "Double Insurance" for Astronaut Safety

Prior to the Shenzhou-19 launch, Shenzhou-20 was already on standby at the launch center. This underscores China's high regard for astronaut safety, employing a "double insurance" strategy. Beginning with the Shenzhou-12 mission, China has adopted a "launch one, backup one" and "rolling backup" launch model utilizing the Long March-2F launch vehicle, providing double insurance for astronaut safety.

Should the Shenzhou-19 crew encounter extreme conditions and need an early return to Earth or require emergency rescue, the Long March-2F Y-20 launch vehicle and Shenzhou-20 spacecraft will immediately enter launch mode to execute an emergency rescue mission for the space station, ensuring astronaut safety.

Anticipation for Shenzhou-19 Astronauts to Create Miracles

The Shenzhou-19 crew is scheduled to return to the Dongfeng landing site in late April or early May next year. During their stay in orbit, they will welcome visits from the Tianzhou-8 cargo spacecraft and Shenzhou-20 manned spacecraft. Let us look forward to the Shenzhou-19 crews incredible feats at the Chinese Space Station!

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