As the Philae lander showed when it touched down on the surface of the comet 67P/Churyumov–Gerasimenko, the surfaces of these small celestial bodies can be more difficult to land on, let alone traverse.
“Hedgehog is a different kind of robot that would hop and tumble on the surface instead of rolling on wheels,” said Issa Nesnas, leader of NASA’s Jet Propulsion Laboratory team. “It is shaped like a cube and can operate no matter which side it lands on.”
The basic concept is a cube with spikes that moves by spinning and braking internal flywheels. The spikes protect the robot’s body from the terrain and act as feet while hopping and tumbling. The spikes could also house instruments such as thermal probes.
Two Hedgehog prototypes were tested onboard NASA’s C-9 aircraft for microgravity research in June 2015. They demonstrated several types of manoeuvres that would be useful for getting around on small bodies with reduced gravity. These manoeuvres were tested in a variety of materials to mimic different surfaces: sandy, rough and rocky, slippery and icy and soft and crumbly.
The Hedgehog has been designed to hop large distances in low gravity situations to reach a certain object. It can also make smaller tumbling motions for more precise movements. However, the researchers also made it perform a ‘tornado’ manoeuvre, in which the robot spins to launch itself from the surface. This could be used to escape from a sandy sink hole or other situations in which the robot would otherwise become stuck.
The researchers are now working on the autonomy of the Hedgehog, increasing how much the robots can do without instructions from Earth.
