San Francisco startup Petra has successfully completed a 20ft (6m) demonstration tunnel through the hardest rock on earth.
Petra used its new semi-autonomous thermal drilling robotic system ‘Swifty’ which can create 18-60 inch (46-152 cm) diameter tunnels through any geology.
Swifty blasts the rock with an extremely hot, high-pressure spallation head.
The startup says that the drilling robot can excavate small tunnels so quickly and cheaply that it could make a lot of underground infrastructure projects economically feasible.

Kim Abrams, CEO and co-founder, commented on the success: “Petra successfully completed a 20ft bore through hard Sioux Quartzite, where we averaged an astounding 1 inch per minute in a geology usually excavated by dynamite.”
“In the past, there have only been a handful of costly and inefficient methods for tunnel construction, starting with manual tools and evolving to the modern tunnel-boring machine.
“Our non-contact method is the next evolution of tunnelling and will usher in a new age of under-grounding utilities.”
DCVC, a Deep Tech venture firm, has invested $30m (c.£21.8m) in the robotics company.
Dr. Chris Boshuizen, DCVC partner and co-founder of Planet, said: “At DCVC we’re committed to investing in companies that are building solutions to make our society’s infrastructure more resilient.
“Petra’s tunneling technology is providing a safer, faster, and more cost-effective option for all underground infrastructure – electricity, water, sewage, and enables projects the world would never have been able to do before.”
Image credit: Petra
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