Robotic Hedgehogs to Explore Moons and Asteroids

phobos hedgehog© Stanford Dept. of Aeronautics and Astronautics

Stanford University, MIT and NASA are working together on the next big thing in space exploration: robotic hedgehogs. The spiky ball-like autonomous machines would be capable of rolling around and collecting data on super-low gravity moons and asteroids, with Martian moon Phobos as their first planned destination.

The design includes a mother spacecraft called the Phobos Surveyor that would carry several robo-hedgehogs to Phobos where they would tumble out and then roll, hop and bound around gathering and transmitting data back to the Surveyor as it orbits the moon.

The group of researchers, lead by Marco Pavone, an assistant professor in Stanford's Department of Aeronautics and Astronautics, designed the hedgehog-like robots to navigate especially rocky and rough terrain and microgravity environments that the typical rover couldn't handle. While the Curiosity rover is able to cling to the surface of low gravity Mars, it couldn't make it in the microgravity of Phobos.

Stanford University explains:

Today's rovers have trouble operating in the low gravity environment characteristic of small celestial objects. For example, such conditions can cause the wheels of mobile platforms to lose traction and spin uncontrollably. Pavone's team has designed the hybrid system to exploit low gravity by relying primarily on airborne motion.

The hedgehogs do not have wheels, as do the current Mars rovers. Instead they rely on three rotating discs enclosed within each hedgehog, with each disc pointing in a different direction.

In the microgravity of Phobos, the inertial forces of the spinning disks allow the hedgehogs to move nimbly and precisely in environments that would leave other robots bouncing or floating uncontrollably. Quickly accelerating the discs causes the hedgehog to hop, while spinning them even faster results in a bound. Accelerating the discs just slightly makes the hedgehogs tumble, ideal for fine maneuvering.

The Phobos Surveyor and the hedgehogs would work as a team during a mission, with the Surveyor gathering large-scale measurements with its onboard equipment and the hedgehogs collecting more detailed data down on the surface.

The team is now on their third generation of robotic hedgehog prototypes, and while this generation is cubical, they plan on continuing to tweak the geometry over time until it is almost sphere shaped. They are testing the hedgehogs in the variety of terrains that they would encounter on Phobos, from powder-soft to very hard and rocky, in order to make sure the spiky balls can gain traction in all scenarios. They've also been trying to replicate microgravity environments for testing as well.

Even with all the work left to be done, the researchers think a Phobos Surveyor mission could happen in the next 10 to 20 years.

Robotic Hedgehogs to Explore Moons and Asteroids
Spiky rolling robots are under development as the next tool in space exploration.

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