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”.