Lunar tunnel engineers excited by boring Moon colonies

As space agencies prepare to return humans to the Moon, top engineers are racing to design a tunnel boring machine capable of digging underground colonies for the first lunar inhabitants.

"Space is becoming a passion for a lot of people again. There are discussions about going back to the moon, this time to stay," US-Iranian expert Jamal Rostami told AFP at this year's World Tunnel Congress in Naples.

The administration of US President Donald Trump wants NASA to put humans back on the Moon by 2024, and the agency is also drawing up plans for a "Gateway" station to serve as a platform for astronauts travelling to and from the lunar surface.

Billionaires Elon Musk and Jeff Bezos are among those feverishly competing for military, civil or commercial launches, with Musk's SpaceX leading the race on building rockets ready to fly in time.

But the harsh conditions on the surface of the Moon mean that, once up there, humans need to be shielded from radiation and freezing temperatures in structures which maintain atmospheric pressure in a vacuum.

They also need protection from meteorite strikes.

"Imagine something the size of my fist as a piece of rock coming at 10-12 kilometres per...