The "Golden Rocket" encountered a sudden failure before 100 launches: an emergency replacement of a valve leak

　　Original title: a sudden failure of the Gold Rocket before 100 launches-- those who experienced it told a little-known story.

On April 20, China successfully launched the 44th satellite of the Beidou navigation system from the Xichang Satellite launch Center.This launch was also the 100th launch of the long triple A series of carrier rockets, and became another record set by this "gold rocket."

However, many people do not know that the rocket encountered a malfunction before this launch. Recently, Li Kai, the model manager in charge of the 211 factory of the China Aerospace Science and Technology Corporation, told the story of the troubleshooting to the reporter of the Science and Technology Daily.

On April 9, when the launch site staff were testing the rocket, they found that there was an air leakage in the oxygen overflow valve located at the back bottom of the third stage oxygen tank of the rocket, which was several times higher than the normal target. The valve was originally used to exhaust and relieve pressure when the pressure of the oxygen box exceeds the standard, but if it keeps leaking, it will make the oxygen box unable to maintain the normal pressure, resulting in "insufficient oxygen supply" when the engine needs oxygen fuel. After finding out the cause of the failure, the staff decided to replace the valve.

At this time, the rocket has been hoisted and erected on the tower, and the replacement operation can only be carried out on the tower platform. The experimental team of the first hospital sent a team of 4 people, with Wang Jingdong as the main operator, Chen Zitong as the assistant, Zhang Yuchen in charge of photography and inspection, and Li Kai under the command. At about 13:30, they opened the entrance door of the third stage of the rocket and got into the narrow cabin between the second and third stages of the rocket.

This is a cylindrical space with a diameter of 3 meters and a height of about 2 meters. There are not only three-stage engines and nozzles, but also many instrument cables and pipeline valves. The environment is very complex.

It is worth mentioning that this is the first time that the cryogenic valve has been replaced in Xichang launch Center. The surface of the cryogenic valve is covered with layers of thermal insulation materials such as cryogenic glue, fiberglass and foam, which need to be removed before replacement. This is not only laborious, but also produces a lot of debris. Li Kai said that the rocket assembly is extremely strict in controlling the surplus, and if these debris and fibers are adsorbed on the equipment, it may lead to instrument failure. So the teammates need to vacuum away all the debris while dismantling it. Confined spaces, intense work, noise from vacuum cleaners and anoxic environment with high nitrogen concentrations quickly made them dizzy. After more than 40 minutes, the cryogenic material was finally cleaned and exposed the trap door.

Dismantling the valve is even more manual work. Wang Jingdong needs to stand in the cabin, raise his arms, hold the valve in one hand, and unscrew the screws one by one with the other. Because the position of the valve is so small that it can only accommodate both hands, it is very difficult for others to see the valve. Except for delivering tools, Chen Zitong could hardly help. After the trap door was removed, Wang Jingdong was so sweaty that he sat directly on the ground.

The tense task did not leave much rest time for the test team members, and soon they got up again, installed new valves, encapsulated insulation materials, and cleaned up the work site. By this time it was time for dinner. However, the work was not over, and then they accompanied the base staff to carry out an airtight inspection of the new valve, and did not leave the tower until 21:00. (reporter Fu Yifei)