Virginia Tech engineers tap buried rocks with vibrations to measure their depth

A team at Virginia Tech has built a device that strikes a partly buried rock with an instrumented hammer and reads the vibrations that travel through it with a scanning laser, in order to estimate how far the rock extends below the surface.

The work is led by Erik Komendera, an assistant professor of mechanical engineering who previously worked as an engineer at NASA's Langley Research Center. It addresses a problem that current Mars missions already face: the elevation and roughness of terrain, and the height of exposed rocks, all affect where a spacecraft can safely put down. Komendera and Ruan published the research in IEEE Sensors Journal, according to an article by Alex Parrish distributed on Phys.org.

The researchers frame the long-term goal in science-fiction terms: crewed spaceflight has not reached the boldly-going ambitions of Star Trek, but if astronauts one day want to land on an uncharted planet the way the crew of the USS Enterprise does, they will first need to know what is on, and under, the surface. Virginia Tech says the vibration method may help rovers land safely on Mars, the moon or other largely unexplored planets, and that it could also apply on Earth, for analyzing construction sites or disaster scenes where hazards are buried.

The problem the tool is meant to solve is a robotic one. If a rock stands in the way of a landing surface, a robotic excavator could chip away at it. But if that rock is actually a buried boulder, the robot should not waste energy and wear out its tools trying to remove something it cannot move. Komendera, quoted in the Phys.org article, said that for as long as humans have built things on Earth, they have had to deal with large and heavy obstacles that cannot simply be ignored or scooped out of the way without careful planning, and that it is easy enough for people to look at rocks and make quick, testable judgments.

The tool has so far been tested only on stone samples buried in a sandbox, not on an actual rover, an actual excavator, or an actual planetary surface.