The design philosophy behind the American lunar architecture depends heavily on a single high-performance main engine responsible for critical mission phases. During descent, that engine governs the entire journey from lunar orbit down to the Moon’s surface. 

On ascent, the same single-point system becomes the only means of returning astronauts to lunar orbit. The lack of redundancy means that a malfunction would eliminate any backup option, a concern highlighted in a peer-reviewed study published in Chinese Space Science and Technology in March, which argues the system “contains some glaring weaknesses.”

By contrast, China’s proposed lunar lander adopts a multi-engine approach. Developed by a Shanghai-based national laboratory team, it uses four variable-thrust engines producing over 30 kilonewtons collectively. Even if one engine fails entirely, the remaining three would still deliver thrust comparable to the main engine of NASA’s Orion spacecraft.

Lunar ascent safety debate centers on redundancy versus mass constraints

Beyond the primary propulsion system, the design includes an additional safeguard layer intended to improve mission resilience. If the main engines were to become inoperative, six smaller orbit-control thrusters can still be activated on the lunar surface, providing an alternative pathway for a rapid ascent. This redundancy raises a broader engineering question: if multiple engines offer greater safety than a single one, why are they not universally adopted, the South China Morning Post writes.

The constraint is mass, as additional engines typically increase overall vehicle weight, reducing efficiency and payload capacity. The Chinese engineering team addressed this trade-off through a structural optimization known as a common bulkhead tank, which integrates fuel storage more efficiently and reduces excess mass while still enabling a multi-engine configuration.

China introduced a new tank design in a crewed deep-space vehicle that uses a pressure-fed system, where fuel and oxidiser are separated by a shared wall, often called a “common bottom.” In earlier lunar lander designs, the two propellants were stored in completely separate tanks, which added extra structural weight and took up more space inside the vehicle.

By combining them into a single structure with a shared barrier, the system reduces unnecessary duplication in the tank framework. According to the researchers, this change cuts weight at the “hundred-kilogram level,” making the overall design more efficient without sacrificing capacity or performance.

Hot-fire tests validate new lightweight tank architecture for space missions

The reduction in mass created by this design enables the use of four engines instead of a single main unit, increasing redundancy without exceeding launch constraints. Built from composite materials, the tank achieves more than a 20 per cent weight reduction compared to traditional metal alternatives. 

Beyond storing propellant, the structure also serves a dual purpose as a load-bearing component of the spacecraft, effectively becoming part of the vehicle’s frame and improving overall mass efficiency. The approach is backed by experimental validation, with the paper drawing on results from full-system hot-fire tests. These tests provide real-world performance data under operating conditions, confirming the feasibility of the integrated structural and propulsion design.

Test results indicate that the four variable-thrust engines can be closely coordinated, keeping thrust variation within less than 100 Newtons. This level of precision is crucial for preventing unstable motion that could cause the lander to tumble during critical flight phases. The experiments also suggest that pressure challenges within the common bulkhead tank can be effectively managed.

Recommended Articles