China is making stainless steel tanks for its future super heavy-lift rockets
HELSINKI — A Chinese state-owned rocket maker is making progress in producing large diameter stainless steel tanks for its next-generation launch vehicles.
The China Academy of Launch Vehicle Technology (CALT) has announced the development of prototype 5.0-meter and 10.6-meter-diameter stainless steel propellant tanks over the past month, with the latter marking a breakthrough for the country’s super heavy-lift rocket plans.
CALT, a leading rocket designer and manufacturer under the China Aerospace Science and Technology Corporation (CASC), announced the developments in late March and late April respectively.
“The success of this prototype marks a major breakthrough in the development of ultra-large-diameter stainless steel tanks and represents a solid first step toward the iterative development of large-diameter stainless steel structures for heavy-lift launch vehicles,” CALT said in a now-deleted statement on the 10.6-meter-diameter tank via its Weixin social media account April 29.
Notably, key leaders from CALT, the China National Space Administration (CNSA), and other high-level authorities were present to witness the completion of the prototype.
The 10.6-meter-diameter, 9.0-meter-high tank is part of the development of the Long March 9; a future reusable super heavy-lift rocket designed for large lunar and infrastructure missions which would transform the country’s launch capabilities. It is also being used in early mission concepts for crewed Mars missions.
The Long March 9 project has morphed in recent years from an expendable rocket designed to facilitate crewed lunar missions, to a reusable, stainless steel project for major infrastructure missions. The changes follow the development and demonstrated progress of SpaceX’s Starship.
The development of the prototype stainless steel tanks demonstrates both progress and commitment towards this new pathway. CALT appears to be developing the Long March 9 to first be partially reusable, before converting it to full reusability in the future.
CALT stated that stainless steel has significant potential for large-diameter cryogenic propellant tanks, especially for reusable, low-cost, and rapidly manufactured launch systems. It added, however, that, compared to aluminum alloy tanks, stainless steel tanks pose unique challenges including being harder to machine, being more prone to buckling, and more susceptible to weld deformation and springback, requiring CALT to make several key technical breakthroughs in assembly, welding and forming technologies.
The reason for CALT’s development of a 5.0-meter-diameter tank is less clear in terms of immediate applications. It is already developing the Long March 10 rocket series, featuring 5.0-meter-diameter first stages, with a common booster core variant for crewed lunar missions, based on the Long March 5. It is unknown if CALT is looking at developing a stainless steel version of the rocket.
CALT said in a March 28 statement that the 5.0-meter-diameter prototype development marked a breakthrough in its production and manufacturing technology innovation, providing strong support for the smooth progress of major national engineering tasks.
The project was also touted as successful exploration of CALT’s innovative development model, featuring rapid iteration with digital empowerment. The academy said it took 60 days to complete design and manufacturing.
The use of stainless steel is a growing trend in China, when taking into consideration the growing commercial sector, which is also developing stainless steel rockets amid a drive for reusable launchers.
Most notably, Landspace is developing the Zhuque-3 stainless steel launcher. It has conducted vertical takeoff, vertical landing tests and is targeting a first orbital launch in the second half of 2025.
Other companies, including Lightyear Exploration—which recently completed a Pre-A round of strategic financing—are engaged in producing stainless steel rocket structure components, while Space Epoch is developing a stainless steel launcher.
