Tianzhou-4 sets sail, China's space station gets new features

At 1:56 a.m. on May 10, the Long March-7 carrier rocket ignited and took off from the Wenchang Space Launch Center in Hainan, China, successfully sending the Tianzhou-4 cargo spacecraft into its planned orbit, marking the start of the first flight of China's space station construction phase.

The Long March 7 rocket successfully launched the Tianzhou 4 cargo spacecraft (Photo by Tu Haichao)

"Tianzhou-4" was developed by the Fifth Academy of the China Aerospace Science and Technology Corporation. During this half-year, the spacecraft will transport supplies, refuel, and downlink waste to the space station, and accompany the "Shenzhou-14" astronaut crew through a six-month space journey.

The uplink cargo of Tianzhou-4 weighs about 6.2 tons, which is equivalent to the carrying capacity of the previous two cargo spacecraft. The cargo includes food, medicine, hygiene and cleaning supplies for the astronaut system, backup and repair parts of key equipment of the space station, test payload of space application system, and 750 kilograms of additional propellant for the space station assembly.

According to the plan, Tianzhou-4 will not only complete the mission of uplinking materials, but also undertake the responsibility of experimental support. The uplink materials include three experimental payloads, which will further verify the principle of the equipment in a weightless environment.

“This is the astronauts’ home.”

The astronauts' cargo bags have changed again. From the QR code labels of Tianzhou-2 to the colorful ribbons of Tianzhou-3, the cargo bags of Tianzhou-4 have been upgraded to version 3.0, and now use colorful "ID cards".

The solar panels of the Tianzhou-4 cargo spacecraft are deployed (Photo from CCTV)

There are six colors: light blue, dark blue, green, purple, light brown, and dark brown. Green represents astronaut system food, light brown represents photographic equipment packages, and purple represents materials in the medical experimental field.

Looking back to after the launch of Tianzhou-2, the cargo spacecraft designers were eagerly awaiting feedback from the astronauts. At a symposium after the return of the Shenzhou-12 crew, everyone had a clearer idea of ​​the direction for improving the cargo package. However, the Tianzhou-3 cargo package was already ready at that time, so the designers temporarily used colored ribbons to make a simple distinction for the cargo packages, and further improved it with colored QR code labels on Tianzhou-4.

The label color provides the first-glance information to distinguish the subordinate system and usage scenario of the cargo package, and provides more detailed information for the exclusive QR code of each cargo package. Jia Dongyong, chief designer of the cargo spacecraft machinery of the Fifth Academy of China Aerospace Science and Technology Corporation, summarized: "Eating, wearing, living and using are all clear at a glance."

Cargo packages carried by the Tianzhou-4 cargo spacecraft (Photo courtesy of the China Manned Spaceflight Office)

The cushioning foam in the cargo bag has also been adjusted accordingly. The "Tianzhou-4" uplink materials include precision instruments and other equipment, which need to be cushioned with foam for shock absorption. Space in the sky is very valuable, and traditional foam boards are large and difficult to store. Designers have improved them into small foam blocks and air bags to facilitate astronauts to store them in orbit.

According to the different environments of the cargo spacecraft during ascent and in orbit, the cargo spacecraft designers also made corresponding adjustments to the adapter plate in the cargo compartment.

The rocket fairing carrying the Tianzhou-4 cargo spacecraft is transferred (Photo by Hu Lanyue, a reporter from China Aerospace News)

After the rocket takes off, the cargo bags inside the spacecraft need to withstand continuous overload and vibration. Therefore, the adapter plates of the cargo compartment and the spacer cargo bags are fixed with screws. After the spacecraft enters orbit, the cabin becomes a weightless environment. After the cargo bags are taken out and disassembled, the adapter plates of the spacer cargo bags must also be stored. The cargo spacecraft designers use Velcro commonly used in daily life so that the adapter plates can be directly pasted in the cargo compartment, reducing the workload of astronauts in orbit.

"This is the astronauts' home." Jia Dongyong introduced that the manned space program focuses on people-oriented, and through more humane design improvements, the astronauts' living experience in the space station will become better and better.

"Big Brother" and "Little Brother"

The Long March-7 carrier rocket ignited and took off. After about 10 minutes of flight, the rocket and the ship separated. The Tianzhou-4 solar sail was unfolded, and then it entered the rapid rendezvous and docking mode. About 6.5 hours later, it successfully docked with the space station assembly.

The Tianzhou-4 cargo spacecraft docked with the space station complex (Photo from CCTV)

Based on the experience gained from the previous Tianzhou series spacecraft, Tianzhou-4 performed well. Key technologies such as rapid rendezvous and docking were first verified on Tianzhou-2 and then practiced again on Tianzhou-3, which has accumulated sufficient experience. Jia Dongyong said: "It's like the big brother has done all the work, so the little brother can relax."

This spring, after 306 days in orbit, the Tianzhou-2 separated from the Chinese space station in a controlled manner and burned up alone through the atmosphere. A small amount of debris fell into the waters of Point Nemo in the South Pacific, the "cemetery" of human spacecraft.

The developers have a special feeling for Tianzhou-2. As the backup ship of Tianzhou-1 in 2017, Tianzhou-2 spent the longest time waiting on the ground and underwent the most ground tests during its development. It is the first "visitor" of the Chinese space station, responsible for more than ten technical verifications and has been in orbit for nearly a year, accumulating experience for the in-orbit construction and operation of the space station, and finally retired with success.

The Tianzhou-3, which was launched shortly afterwards, docked successfully with the Tianhe core module, supporting the Shenzhou-13 crew's 183-day in-orbit stay, connecting to the core module's information network and providing power. The relay emergency communications on the spacecraft provided dual guarantees for ground-to-earth dialogue and Tiangong teaching, and it recently completed the orbiting and forward rendezvous and docking tests.

Schematic diagram of the docking of the Tianzhou-3 cargo spacecraft and the Tianhe core module (Photo courtesy of the China Manned Space Administration)

"Tianzhou-3", "Tianzhou-4" and "Tianzhou-5" were put into production in batches. Their status is relatively stable, which ensures the speed and quality of manned space projects to the greatest extent.

"She is beautiful but does not compete for spring. She only announces the arrival of spring. When the mountain flowers are in full bloom, she smiles among the bushes." The cargo spacecraft development team believes that this is the best evaluation of the Tianzhou series of cargo spacecraft.