Development of a robot that can dig through the hardest rock

Petra, a San Francisco startup, has developed a "Swifty" heat-drilling semi-autonomous robot that can penetrate the hardest geological formations by crushing rock into powder.

Instead of using a mechanical drill, the robot "Swifty" uses a hot drill with high pressure to remove the rock layer without direct contact. In a recent test, Swifty tunneled 45 - 152 cm wide through crushing all kinds of rocks. The test involved a 60cm wide tunnel through 6m of sioux quartzite, the hardest rock on Earth that can only be broken with explosives. The robot tunnels at a speed of about 2.5 cm/min.

Thanks to a combination of heat and high pressure, the tunneling robot can drill through hard rock.

"Previously, there was no method that could dig through this hard rock. Petra's achievement was thanks to Swifty's thermal drilling method that was able to effectively cut through rock without touching," said Ian Wright, director. Petra's chief technology officer, said.

Petra's robot uses machine vision, an artificial intelligence system that allows the robot to "see" and make decisions based on obstacles it encounters. When in operation, the robot breaks the rock with a mixture of hot gases above 1,000 degrees Celsius, turning the rock layer into smaller debris. After the rock layer is broken, a powerful vacuum cleaner sucks up the debris, clearing the way for the robot to continue drilling.

"Petra can drill through the hardest geological formations in the ground, allowing customers to install equipment underground in rugged geographies prone to wildfires and rainstorms. In addition, we can simply digitize projects in the city by allowing engineers to locate beneath the existing infrastructure maze," a Petra company representative shared.

Petra's technology was inspired by an experiment conducted by scientists at Los Alamos National Laboratory in the 1960s. They designed a nuclear-powered tunneling machine that could travel through the upper mantle of the Earth or even the crust of the Moon. That rock-melting drill never materialized, but Petra learned from the project and performed its first tests in an industrial park in Oakland, California in 2018. Initial testing used plasma but the techniques Engineers quickly switched to gas and heat to make the device less bulky.

Petra's Swifty robot aims to dig tunnels through bedrock cheap enough to provide the incentive for businesses to put power lines, network wires and other lines underground. According to Petra, Swifty's thermal drill can reduce the cost of tunneling through bedrock by 50-80%. The company is testing thermal drilling with rocks ranging from granite to limestone in areas from California to the Appalachian Mountains.