What technological forces are behind the successful return of Shenzhou-14?

At 20:09 on December 4, the return capsule of the Shenzhou XIV manned spacecraft successfully landed at the Dongfeng landing site. The scientific research teams of central enterprises such as China Aerospace Science and Technology Corporation, China Aerospace Science and Industry Corporation, and China Electronics Technology Group Corporation have innovated a number of technical methods to ensure the smooth return of the Shenzhou XIV crew.

At 20:09 on December 4, the return capsule of the Shenzhou XIV manned spacecraft successfully landed at the Dongfeng landing site, and the Shenzhou XIV manned flight mission was a complete success.

The return of the Shenzhou XIV crew is the first return mission after the completion of the "T" basic configuration of the Chinese space station. It is also the first time that a manned spacecraft returns to the Dongfeng landing site at night in winter. The mission continues the technical status since the return of the Shenzhou XIII manned spacecraft. Using the rapid return mode, the return flight around the earth is shortened from 18 to 5, and the return time is shortened by nearly 20 hours. Compared with previous missions, low temperature and dark night are the two major challenges of this mission. Faced with the test, my country's scientific research team has innovated a number of technical methods to escort the Shenzhou XIV crew home smoothly.

Xinhua News Agency photo, Beijing, December 4, 2022

Thermal control system makes astronauts' journey home warmer and more comfortable

In December, the Dongfeng landing site was hit by a biting cold wind, with the temperature dropping to minus 20 degrees Celsius at night. Many people were concerned about how the astronauts on the Shenzhou XIV spacecraft would keep warm on their journey home.

Peng Huakang, the overall technical director of the manned spacecraft recovery test team of the Fifth Academy of China Aerospace Science and Technology Corporation, introduced that after the manned spacecraft separates from the space station, the spacecraft's own thermal control subsystem will take over the temperature and humidity control and control the temperature of the sealed cabin within the range of 17 degrees Celsius to 25 degrees Celsius.

The measures taken by this system include active thermal control and passive thermal control. Passive thermal control refers to the heat-resistant materials, coatings and cabin fans on the surface of the spacecraft; active thermal control includes heating plates and radiators inside the spacecraft.

Xinhua News Agency photo, Dongfeng landing site, December 4, 2022

During the process of entering the atmosphere, the temperature of the return capsule will rise to a certain extent due to the intense friction with the atmosphere. However, through thermal control pre-cooling, the temperature inside the return capsule can be lowered in advance. At the same time, the ablation and sublimation of the ablation material on the surface of the return capsule will take away a lot of heat.

After the return capsule lands, it is mainly the passive thermal insulation performance of the capsule that comes into play. "Through simulation calculations, if the return capsule lands in a desert at minus 25 degrees Celsius, the temperature inside the cabin can be kept above 15 degrees Celsius for one hour without opening the hatch and ventilation fans," said Peng Huakang.

The reporter learned from the China Astronaut Center that in response to the low temperature and dark night environment, scientific researchers have developed new warming devices for astronauts and added a series of auxiliary lighting measures. At the same time, they have optimized the medical monitoring and health insurance work process, reduced the astronauts' exposure time outside the cabin, and ensured timely entry into the carrier to carry out medical monitoring and health insurance related work.

The communication and control network creates "bright eyes" for the safe return of spacecraft

From the return capsule changing speed to enter the return orbit to the separation of the propulsion capsule and the return capsule, from the return capsule entering the atmosphere to its safe landing... every step of the return requires the measurement and control system to receive and send commands, pulling and escorting the return journey layer by layer.

At the main landing site, China Electronics Technology Group Corporation has deployed a multi-station satellite communication system and a multi-model measurement and control system, and upgraded the satellite communication equipment, increasing the transmission capacity by 5 to 10 times. The newly developed Beidou situation system in the recovery area uses the positioning and short message functions of the Beidou navigation system to build a command center, front command, and search platform trinity command system, which greatly improves the search efficiency of the return capsule and shortens the recovery time.

Since the Shenzhou XIV re-entry capsule entered the atmosphere, the measurement radar of the Second Academy of China Aerospace Science and Industry Corporation has been tracking and measuring real-time data like a "bright eye".

The "blackout zone" formed when the return capsule enters the atmosphere will cut off the communication between the return capsule and the ground tracking and control station. To solve this problem, the 23rd Institute of the Second Academy of China Aerospace Science and Industry Corporation independently developed the phased array measurement radar "Recovery No. 1". The radar for this mission absorbed the experience of previous missions and optimized its design.

The dual challenges of darkness and extreme cold have put forward higher requirements for directional search and rescue equipment. Song Lei, head of the manned space mission team of China Electronics Technology Group Corporation 22nd Institute, introduced that in this mission, the scientific research team strengthened the construction of the integrated sky-ground search and guidance system, and the newly developed astronaut communication radio achieved seamless connection with the measurement and control system at the landing site, and for the first time "extended" the astronauts' voice calls in the cabin to the Beijing Flight Control Center.

In addition, the helicopter's front cabin search and guidance system conducts deep integration and intelligent decision-making of multi-source search and rescue information at the landing site, helping the search helicopter to predict the return capsule's trajectory in advance from a long distance, gaining valuable "advance time" for the search mission.

The deceleration buffers are linked together to achieve a "gentle" landing

Peng Huakang introduced that from the moment the return capsule entered the atmosphere, as the carbonization and ablation of the heat-resistant materials on the surface of the capsule took away a large amount of heat, the flight kinetic energy of the return capsule continued to decrease, and the speed gradually decreased from 7.9 kilometers per second to several hundred meters per second.

When the spacecraft was about 40 kilometers from the ground, it had basically left the "black barrier zone". The static pressure altitude controller installed on the return capsule determines the altitude by measuring the atmospheric pressure. When the return capsule is about 10 kilometers from the ground, the guide parachute, the deceleration parachute and the main parachute are opened successively, and the area of ​​the three parachutes gradually increases from a few square meters to more than 1,000 square meters. This set of parachutes reduces the speed of the return capsule from 200 meters per second to 7 meters per second, achieving the purpose of reducing overload and protecting astronauts.

Xinhua News Agency photo, Dongfeng landing site, December 4, 2022

Shortly after the main parachute was fully opened, the gamma altitude control device in the return capsule began to work, measuring the altitude from the ground in real time by emitting gamma rays.

When the return capsule drops to a height of 1 meter from the ground, the gamma altitude control device at the bottom sends out an ignition signal, and the four reverse thrust engines on the capsule ignite, generating an upward impulse, causing the return capsule to land at a speed of 1 to 2 meters per second. At the same time, the astronaut seats equipped with buffer devices will begin to rise before landing, further reducing the impact of the astronauts landing and achieving a "gentle" landing.