To explore caves on Mars and the Moon, take a hint from Hansel & Gretel, say boffins

Robot adventurers drop mesh network 'breadcrumbs' to stay connected

To explore the subterranean lava tubes and caverns of the Moon or Mars we ought to consider the lessons learned by Hansel and Gretel, boffins have suggested, albeit with mesh networking technology the pair of unfortunate children didn't have.

University of Arizona electrical and computer engineering professor Wolfgang Fink and his team took inspiration from the fairy tale pair to develop a rover-and-breadcrumbs system they said will allow exploration deep underground, and in a manner more adaptable than previous concepts. The key to such robotic exploration is communication, and the team have a cunning plan.

Fink and his team presented what they call a "dynamically deployed communication network," or DDCN, in a recently-published paper. Nodes in the network, dubbed "Hansel & Gretel breadcrumbs" are deployed by subterranean rovers that are controlled and monitored by a mother rover that stays on the surface.


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If this sounds similar to other subterranean exoplanet exploration concepts we've covered before - it is, but with a few major differences, most crucially how smartly the nodes are deployed.

"One of the new aspects is what we call opportunistic deployment – the idea that you deploy the 'breadcrumbs' when you have to and not according to a previously planned schedule," Fink said

Unlike other rover mesh network plans that deploy nodes at a fixed schedule, the Hansel and Gretel system is designed to drop a new node whenever its communication to the previous node becomes too weak. Inter-cave explorer bots, or ICE, will pause whenever their signal is too weak in order to deploy another breadcrumb, and they won't move on until they can validate the new node's connection to the network. 

All of these decisions, Fink said, can be made without input from the mother rover on the surface, as ICE are designed to be autonomous. 

The ICE and nodes, which can be equipped with any number of sensors for mapping and data gathering, are both designed for one-way trips into lava tubes and caves. Fink said this ensures resources aren't being wasted going back into the caves to get them out; "it makes more sense to have them go as far as they possibly can and leave them behind," he said. 

Living the tube life

There's a lot of reasons to start exploring the inner surface of the Moon and Mars, the team argues in their paper. 

Not least among them is the fact that if life still exists on a place as inhospitable as Mars it's likely to do so underground. Liquid or frozen water may be found in lava tubes and caves on the Moon and Mars as well and if we were planning on settling then caves and tunnels provide a radiation-shielded habitat. 

"Lava tubes and caves would make perfect habitats for astronauts because you don't have to build a structure; you are shielded from harmful cosmic radiation, so all you need to do is make it pretty and cozy," Fink said.

Along with addressing one of NASA's long-standing Space Technology Grand Challenges [PDF] - specifically the challenge of all-access mobility - similar tech that lets roving bots decide how best to build their mesh network could also be useful on Earth, too.

The military and disaster recovery could both make use of such autonomous DDCN tech, as could exploratory missions in the oil, gas and mining industries, Fink and company wrote in their paper.

Just to remember to avoid witches and gingerbread houses, if explorers find them. ®

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