Going underground: When the regular battlespace becomes too dangerous, just dig deep

A new battlespace could be opening up somewhere unexpected, right here beneath our feet.

Suppose it were possible to move through the Earth's crust as easily as a submarine does through water.

That sound impossible, and probably it is right now, but technology is advancing all the time and some very powerful minds in defence and research are giving it some serious thought.

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Cracked earth, not crackpot

Crackpot science, you think? Well, technology is being developed to one day, perhaps, make that possible.

It's known as a soft robot and mimics what nature has already worked out in the form of the humble earthworm.

US-based GE Research created this six-foot-long prototype and says one day it will dig a tunnel longer than five football fields in just 90 minutes.

It uses pneumatic artificial muscles to move like a worm, compressing soil along the hole's walls, inches forward, removing the need to dispose of any material it's pushing through.

It's unclear how far this research has progressed, or how it could be scaled up to make moving a person through the tunnels it burrows.

But it's the result of a challenge thrown to the defence and research sector by Darpa, America's Defence Advanced Research Projects Agency.