appConfigEntityId

bodyType

customContents

entityId

entityUuid

isVideo

articlePageQuery

article

articleSchemaContent

content

hooksArticlePageAdvertisementConfigArticle

appConfig

filter

json

liveArticle

Stephen Chen

In the 21st century race to the moon, there is a question that engineers must ask: what happens when the main engine fails?
China and the United States are answering this in contrasting ways. Their answers could reveal the value they place on human life.
From the Apollo Lunar Module in the 1960s to Nasa’s new Orion spacecraft for the Artemis programme, the American architecture relies on a single, powerful main engine to do the heavy lifting.
On the descent stage, one main engine controls the entire fall from lunar orbit to the surface. On the ascent stage, one main engine is the only ticket home.
If that one engine fails, there is no backup. This design, to quote a peer-reviewed paper published in the journal Chinese Space Science and Technology in March, “contains some glaring weaknesses”.
The Chinese lunar lander puts its faith not in one main engine, but in four.
According to the project team from a national laboratory in Shanghai, four main variable-thrust engines will power the Chinese craft.
Together, these engines can generate over 30 kilonewtons of thrust. If one of them fails completely, the remaining three can still produce thrust comparable to the entire main engine of the Orion spacecraft.


And the safety net has a second layer. Even if the main propulsion system is crippled, the lander has six smaller orbit-control engines that can fire up on the lunar surface to help in a rapid ascent.
If four engines are safer than just one, but why does not everyone use them? The answer is weight.
More engines mean more mass. The Chinese team solved this problem with a stroke of structural genius: the common bulkhead tank.
For the first time in a crewed deep-space vehicle using a pressure-fed system, China used a tank where the oxidiser and fuel share a common wall, or “common bottom”.
In all previous designs, the lunar lander had two separate tanks, which meant double the structural weight and less usable space.
By letting the two propellants share a wall, the design eliminates structural redundancy in the tank itself, saving “weight in the hundred-kilogram level”, according to the researchers.
This weight saving buys the freedom to install four engines instead of one. Using composite material, this tank sheds over 20 per cent of the weight compared to a conventional metal one.
The structure is also designed to be load-bearing, acting as part of the spacecraft’s frame, further optimising the vehicle’s mass.
The paper presents hard-won data from full-system hot-fire tests. The results proved that they could synchronise the four variable-thrust engines to a thrust deviation of less than 100 Newtons, ensuring the lander will not be thrown into a fatal tumble.
They also showed that the perilous common bulkhead pressure could be tamed.
For any other nation to replicate this four-engine common-bulkhead design, they would have to master the autonomous pressure control of a common bulkhead tank with a razor-thin safety margin.
They would also need to achieve synchronised thrust consistency across multiple throttling engines – a problem that becomes exponentially more complex with each engine added.
SpaceX’s Starship Human Landing System, a 50-metre-tall stainless-steel behemoth, is designed to descend to the lunar surface. While its ambition is breathtaking, many seasoned aerospace experts worry that landing a vehicle of that height on the lunar surface presents an immensely complex physics problem, which means great risk to anyone on board.
The American Artemis programme has already faced nitrogen leaks and troubling damage to its heat shield’s protective coating in human test flights. These problems could be fatal. Yet, the pressure to return to the moon before China’s landing is huge and mounting.
The South China Morning Post contacted Nasa for comment.


Why SpaceX may not be a model for Chinese companies to copy

Chinese team flags life-threatening ‘glaring weakness’ in Nasa’s Artemis programme

Chinese team builds first commercial ‘3-lane highway’ in optical fibre to boost capacity

PLA scientists propose a plan to destroy US carrier groups from 3,000km away

Science

A Chinese team has flagged a “glaring weakness” in Nasa’s Artemis programme which could be life threatening. Photo: Reuters

China delivers first samples collected from far side of the moon to Russian scientists

The Chang’e-6 mission was the first to collect samples from the far side of the moon. Photo: AP

China merges lunar programmes as race to moon with US heats up after latest SpaceX launch

Pictures of the moon’s surface taken by the Chang’e-6 probe in 2024. Photo: EPA-EFE

China launches new war on deserts with technology tested on far side of the moon

An apple orchard in China’s western Xinjiang Uygur autonomous region, along the edge of the Taklamakan Desert. Photo: Xinhua

Looming US rocket debris crash unlikely to hit Chinese moon landers: experts

Nasa’s Lunar Reconnaissance Orbiter map shows the predicted impact site for a Falcon 9 rocket part, expected to strike the moon in August, and the locations of other moon landers. Photo: Nasa

Meet China’s moon porter for Chang’e-8 mission: a 4-wheeled robot with 2 arms

The robot will transport, deploy and install instruments and sensors at their designated lunar locations after the Chang’e-8 probe lands. The object pictured is a model. Photo: SCMP

News

China

Researchers say China’s lunar lander has three backup engines, unlike US design which relies on one main power source


Researchers say China’s lunar lander has three backup engines, unlike US design which relies on one main power source.


United States

SpaceX

Chinese team flags life-threatening ‘glaring weakness’ in Nasa’s Artemis programme

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Researchers say China’s lunar lander has three backup engines, unlike US design which relies on one main power source

Researchers say China’s lunar lander has three backup engines, unlike US design which relies on one main power source