Breaking News! During its operation in orbit, the Shenzhou No. 20 manned spacecraft is suspected to have been hit by a small space debris. Currently, the mission team is conducting emergency impact analysis and risk assessment.
This incident once again brings the issue of space debris into the spotlight, especially those hard-to-track micro-debris. Although small, they pose significant risks. Space debris mainly comes from retired satellites, rocket debris, mission leftovers, and debris generated from collisions. With the increasing frequency of human space activities, the number of debris in Earth's orbit continues to grow, becoming an unavoidable threat to space missions.
Micro-debris typically refers to particles with a diameter less than 1 cm. They are small in size and numerous, making it difficult for ground monitoring systems to accurately track them. However, due to their extremely high speed in orbit—averaging 7 to 8 kilometers per second, or even faster—their kinetic energy is astonishing.
According to NASA's estimates, a 0.5 cm aluminum fragment at orbital speed can have the same kinetic energy as a bullet fired from a gun on the ground. This impact force is sufficient to penetrate thin-walled structures, damage critical components, or even trigger chain reactions.
Historically, incidents caused by micro-debris have occurred frequently. In 1983, the U.S. Space Shuttle Challenger was struck by a tiny paint chip while on a mission, causing serious damage to the window and forcing the mission to be terminated early and return to Earth.
A more recent example is on December 14, 2022, when the Soyuz MS-22 spacecraft docked with the International Space Station (ISS) was hit by a micrometeoroid, causing a coolant pipe to rupture. The coolant sprayed out at high speed for several hours, leading to a failure in the thermal regulation system. Astronauts then used a robotic arm to inspect and confirm the impact point, but the incident forced mission adjustments, highlighting the real-time and serious nature of the micro-debris threat. These cases show that even though the debris is small, the high-speed impact can cause structural damage, system failure, or functional interruption, thereby threatening the safety of astronauts and the success of the mission.
In response to this threat, spacecraft design has adopted multi-layered protection strategies. First, for larger and trackable debris (typically over 10 cm in diameter), ground control centers continuously monitor their orbital data through a global monitoring network. If calculations indicate a potential collision risk, the space station or spacecraft will use thrusters to perform a maneuver to avoid the potential impact. For example, the International Space Station has executed over 30 debris avoidance maneuvers since its launch in 1999, with the frequency increasing in recent years, reflecting the worsening debris environment. This active avoidance relies on accurate orbital predictions and rapid response capabilities, but it is not foolproof due to limitations in monitoring accuracy and debris density.
For the massive amount of untrackable micro-debris, spacecraft primarily rely on passive protective structures to "withstand" impacts. Both the Chinese Space Station and the International Space Station use advanced protective devices, such as Whipple shields. This structure consists of multiple layers of cushioning materials, with the outer layer designed to shatter incoming debris, and the inner layer to absorb and disperse energy, thus reducing damage to the main structure.
In terms of materials, spacecraft often use high-strength composites, such as Kevlar or ceramic matrix composites, to enhance impact resistance. Additionally, system design emphasizes redundancy and distributed layout, such as using backup schemes for critical lines and equipment to prevent single-point failures; important instruments are installed in dispersed locations to reduce the risk of concentrated exposure. This design philosophy enhances the survival capability of spacecraft, allowing overall functionality to be maintained even if part of the area is damaged.
Returning to the Shenzhou No. 20 incident, the Chinese space agency publicly disclosed the impact situation, demonstrating its principle of prioritizing safety. Currently, the mission team is assessing the extent of the damage through various means. Key inspection targets include the heat shield of the reentry capsule, which is crucial for withstanding high temperatures during atmospheric re-entry. If damaged, it may affect the safety of the return. In addition, the pipeline system, key electronic equipment, and main cables are also core areas of concern. The onboard impact leakage monitoring and positioning system is playing a key role, using a sensor network to detect pressure changes and abnormal vibrations in real time, assisting in locating the damage points.
If the initial analysis indicates the need for further inspection, the mission team may initiate a spacewalk using the robotic arm or even arrange for astronauts to conduct an extravehicular activity to visually inspect the external structure.
If the assessment indicates that the Shenzhou No. 20 is severely damaged and cannot safely execute the subsequent return mission, China's space program already has an emergency plan in place.
In fact, China has implemented an innovative model in its crewed spaceflight program: "launch one, keep one as backup." When the Shenzhou No. 21 crewed spacecraft is launched, the Shenzhou No. 22 has already completed the final assembly and testing at the Jiuquan Satellite Launch Center, with propellants loaded, escape tower system checked, and cabin environment maintained at an appropriate state.
This flexible arrangement ensures that in case of an emergency, rescue launches can be organized as quickly as possible, enabling the return of astronauts between Earth and space. In contrast, the International Space Station once faced extended astronaut stays due to insufficient preparation of rescue spacecraft in similar situations.
Additionally, the mission team can make flexible adjustments, such as first using the Shenzhou No. 21 spacecraft to retrieve some astronauts, and then launching the Shenzhou No. 22 to dock with the space station as a subsequent return vehicle.
The severity of the space debris issue should not be underestimated. According to statistics, there are hundreds of millions of debris particles in Earth's orbit, most of which are micro-debris. They not only threaten crewed missions but can also collide with satellites and damage space infrastructure. Micro-debris is generated from various factors, including satellite breakup, residual debris from rocket stage separation, and debris clouds from anti-satellite tests. These fragments remain in orbit for a long time and may generate more debris through collisions, forming a "Kessler Syndrome" effect—where the density of debris becomes so high that chain collisions become self-sustaining, continuously deteriorating the orbital environment.
Against this backdrop, our space station and our crewed spacecraft need to further strengthen their protective capabilities to ensure the safety of our spacecraft.
Original article: https://www.toutiao.com/article/7569075505362682431/
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