How to ensure the safe return of astronauts to the ground? These "artifacts" are crucial, and the journey home is a thrilling journey back to the capsule | spaceship | artifact

"Throw a heat-resistant bottom!"

"Return cabin hanging!"

"Landing reverse thrust engine ignition!"

At 6:33 am today, the return capsule of the Shenzhou-15 manned spacecraft successfully landed at the Dongfeng landing site. The astronauts Fei Junlong, Deng Qingming, and Zhang Lu who carried out the flight mission were in good physical condition, and the Shenzhou 15 manned flight mission was a complete success. In this mission, the Shanghai Aerospace Technology Research Institute of China Aerospace Science and Technology Corporation once again took on the responsibility of protecting astronauts and ensuring their safe return to the ground.

Confirm eye contact as soon as possible

In the return mission of the Shenzhou-15 spacecraft, Shanghai Aerospace 804 Institute undertook multiple products, including landing search beacons, voice processing equipment, USB responders, image processing equipment, remote control and telemetry equipment. Among them, landing search beacons and voice processing equipment play important roles in the spacecraft's return mission.

The landing search beacon is located at the bottom of the return capsule and is one of the communication equipment between the spacecraft and the ground. It serves as a guide for the air and ground search centers, mainly to send out beacon signals during normal return landing or emergency landing, provide positioning information for landing search, sea search, and international rescue, and cooperate with the implementation of the return capsule search and rescue mission.

After entering the dense atmosphere, the return capsule is the most adverse stage of the return process. As the altitude decreases, the air density increases, and the friction between the surface of the spacecraft and the atmosphere generates enormous heat, resulting in the return module not receiving the radio signals sent by the ground, and the ground also not receiving the radio signals sent by the return module. This area is known as the radio "black zone".

The landing search beacon aircraft starts working immediately after the black obstacle appears, continuously sending out beacon signals to ensure that when the black obstacle disappears and the return capsule is approximately 35 kilometers away from Earth, it immediately re confirms its gaze with the ground, obtains contact, and provides location information. Afterwards, the landing search beacon continued to operate, marking its own location and telling search and rescue personnel "I am here" to provide decision-making basis for the command center until the return capsule search and rescue mission was completed.

In addition to sending beacon signals, the landing search beacon can also switch working modes. After the return module leaves the "black zone", astronauts can establish voice communication with the ground through the landing search beacon.

The manned flight mission requires finding the return capsule as soon as possible, rescuing the astronauts as soon as possible, reporting the on-site situation as soon as possible, and ensuring the safety of the astronauts. With the "communication support line" during the landing and return process, astronauts can hear the "discovery signal, normal tracking, and stable orientation" emitted from the ground, and the ground can also receive the "feeling good" given by astronauts

Steadily return to the "last meter"

The return of the spacecraft goes through four stages: braking deceleration, free gliding outside the atmosphere, re-entry into the atmosphere, and recovery landing. Among them, recovery landing is the final step of manned spaceflight and also the ultimate symbol of the success or failure of manned spaceflight missions. In order to protect astronauts from returning home safely, Shanghai Aerospace 806 Institute has developed a highly reliable and safe engine to escort the spacecraft's return capsule to the "last meter" of its journey.

Reducing speed and mitigating impact are key to ensuring the safety of astronauts during the return landing process of the spacecraft. When the return capsule is about 10 kilometers away from the ground, the guidance parachute, deceleration parachute, and main parachute are opened one after another, and the speed of the return capsule decreases from 200 meters per second to 7 meters per second. However, the speed of 7 meters per second is still very dangerous for astronauts, and it is highly likely to cause damage to their spine. In order to ensure the safety of astronauts and provide a good riding experience at the last moment of landing, it is necessary to perform the final step of safety protection before landing with a reverse engine.

When the return capsule lands about one meter above the ground, the four landing thrust engines installed at the bottom of the capsule activate the "precise brakes" to further reduce the descent speed based on the parachute deceleration. After receiving the command, the reverse engine ignites simultaneously within 10 milliseconds to slow down the landing speed.

"This is a one-time irreversible process, and the program actions of the entire engine are coherent and interlocked, like a high-level stunt performance. What we can do is to ensure that the engine not only ignites quickly but also works stably in about 200 milliseconds." said the engine designer at 806 Institute.

Since joining the manned space engineering development team in 1994, 806 Institute has been committed to the development of thrust reversers. The landing thrust reversers of its Shenzhou-1 to Shenzhou-15 spacecraft have successfully completed their flight missions.