How many steps are needed to neatly fold three parachutes the size of basketball courts and put them into the return capsule?

The main parachute has an area of ​​1,200 square meters, and can cover three basketball courts when fully deployed; the main parachute is more than 70 meters long when straightened, and can span a football field...Late at night on December 4, the Shenzhou XIV return capsule returned home. During the live broadcast, the giant parachute that opened in the air attracted everyone's attention. This is the "Shenzhou Big Parachute" developed by the 508th Institute of the Fifth Academy of China Aerospace Science and Technology Corporation, which has protected 14 spacecrafts from returning safely.

Image source: China Manned Spaceflight

Success is hard-won. The development of the parachute requires 30 production processes, more than 20 packaging processes and more than 40 assembly processes. How was this giant parachute "born"? And how did it manage to be less than 200 liters in volume after being folded up and fit into an ordinary household refrigerator? Let's take a look.

On December 4, the return capsule of the Shenzhou XIV manned spacecraft successfully landed at the Dongfeng landing site. This is the landing site. Photo by Xinhua News Agency reporter Lian Zhen

Experts from the 508th Institute said that the raw materials for the giant parachute were carefully selected. First, a special material with high strength and light weight was selected based on the design parameters. After the materials were in place, they were retested to test the strength, elongation, air permeability, etc. of the materials to ensure that all indicators met the design requirements. Before processing, the apparent quality of the materials must be further checked, and the inspectors will check the appearance of the materials line by line under the light of the fabric inspection device.

Afterwards, the raw materials are cut into parts of different sizes and shapes. For silk materials, the materials must be spread out and laid flat before cutting, and left to stand for a period of time to remove the material's own stress, and then cut according to the process template. When cutting, the staff will pay special attention to the direction of the silk thread to ensure that the direction of the thread is consistent with the force direction of the product. For rope materials, the process personnel will calculate different loading forces according to different types and specifications to release the material's own stress, thereby effectively ensuring the consistency of the cut products.
The giant parachute uses a typical ring-sail parachute type, which has the advantages of high reliability and strong tear resistance. The red and white rings and sails play an important role in this. The giant parachute can effectively reduce the descent speed of the return capsule because it can obtain a larger resistance area when unfolded, but the initial state of the parachute is a small piece of trapezoidal silk cloth, which needs to be sewn together by the staff.

When sewing, the staff will control the quality of the sewing stitches, not only to ensure the density of the stitches, but also to ensure the stitch width, distance from the edge, stitching, etc. The umbrella canopy is like a "double-eaved roof" when building a house, and each layer of rings or sails is similar to the mortise and tenon structure interlaced with each other.

The return capsule of the Shenzhou 13 manned spacecraft successfully landed in the designated area of ​​the Dongfeng landing site. Photo by Xinhua News Agency reporter Lian Zhen

The giant parachute ring and sail canopy are connected like a line after being sewn together, but as a parachute is a 1,200 square meter surface, it is necessary to use the parachute radial bands and latitudinal bands to combine the sewn rings and sails. The radial bands and latitudinal bands are like the "four beams and eight pillars" when building a house. The radial bands are the main structure that bears the radial tension of the canopy, while the latitudinal bands are the main structure that bears the latitudinal tension of the canopy and maintains the inflated shape of the canopy. The processed radial bands and latitudinal bands can ensure the strength of the parachute.

The parachute ropes of a giant parachute bear the load of the canopy opening during operation and are the main structure for transferring the load to the sling and the return capsule. However, the parachute ropes of a giant parachute are more than 40 meters long and there are 96 of them. How can they be orderly and not tangled during the processing?

During the preparation process, the staff of the 508th Institute first installed and sewed the parachute rope at the same end, and then used a tool called a rope combing clamp to arrange the parachute ropes in order of numbering into the rope combing clamp. Holding the rope combing clamp, they sorted them from the beginning to the end, and then installed the parachute ropes at the other end one by one, so that each rope could be clearly distinguished.

The scene of the Shenzhou spacecraft parachute packaging. Photo provided by the 508th Institute of the Fifth Academy of China Aerospace Science and Technology Corporation

Although the giant parachute is huge, it is very light, weighing less than 100 kilograms. After being folded, the volume of the parachute bag is less than 200 liters, which can be stuffed into an ordinary household refrigerator. However, the soft parachute is not randomly rolled up and placed in the return capsule, but the canopy, parachute ropes, connecting straps and other components of the parachute are neatly and orderly packed into the parachute bag to keep a certain geometric shape. This involves an irreversible task that sounds simple but has high technical content - packing the parachute.

It is reported that before the parachute is officially packed, it must be aired to release the internal stress of the material and clean up the excess; then the canopy is folded, the parachute ropes are combed, the parachute bag is sorted, the parachute is loaded, the bag is sealed, and the weight is weighed. Finally, the 1,200-square-meter large parachute is turned into a parachute bag of only 200 liters, completing the final work before entering the cabin.