A ceremony marking the production of the 100th rocket fuel tank bottom based on the second-generation hydroforming technology is held on Oct 13. [Photo/chinadaily.com.cn]

Answering the call of how to build the bottom of a rocket fuel tank with a diameter of 3 meters from a single thin plate, Chinese research teams have found the answer. 
 
A team led by Professor Yuan Shijian from the Harbin Institute of Technology and another from the No 149 Factory of the No 8 Academy of China Aerospace Science and Technology Corporation (CASC) have jointly developed this second-generation hydroforming technology.
 
In comparison with the first-generation technology created overseas, the second generation has fundamentally solved a nagging problem in the overall formation of large-size thin-walled curved components, which is the coexistence of wrinkling and cracking.
 
Products applying the new technology also boast significant advantages in terms of their quality, high reliability, and low cost.
 
The carrier rocket is a national treasure – the greater its carrying capacity, the larger the stage for space exploration. The fuel tank is the main structure of the rocket, accounting for 80 percent of its structural weight.
 
The bottom of the fuel tank, which must endure internal pressure, axial pressure, heavy vibrations, and the force of impact among other complex combined loads, is the core component supporting the overall reliability of the rocket.
 
Since 2012, Professor Yuan has led his research team to develop the hydroforming technology, breaking new ground and solving the international challenge of wrinkling that occurs during the holistic forming of thin-walled structures.
 
To transform new theories and processes into tangible production capacity, in 2018 Yuan's research team developed the large-scale CNC sheet hydroforming press. They conquered more than 10 core key technologies and, for the first time, formed a 3-meter level rocket base directly from ultra-thin plates – all of which have been successfully mass-produced.  
 
This has significantly improved the load-bearing capacity and reliability of the rocket structure, and enabled China's key rocket structural manufacturing technology to take a great leap forward.
 
On Oct 13, the 100th rocket fuel tank bottom applying the second-generation technology successfully rolled off the production line.