Hedgehog Rovers Will Bounce, Hop, Leap Their Way Over Martian Moon Phobos
January 3, 2013

Hedgehog Rovers Will Bounce, Hop, Leap Their Way Over Martian Moon Phobos

Lawrence LeBlond for redOrbit.com - Your Universe Online

Stanford University researchers, working with NASA´s Jet Propulsion Laboratory (JPL) and MIT, have designed a new robotic platform that could be used to explore the moons of Mars. The platform consists of a mother spacecraft and anywhere from one to several spiky, spherical rovers that can be deployed on the surface of a moon, such as Phobos, where they can hop, roll and tumble their way across rugged terrain.

Each rover, dubbed a "hedgehog," measures about 2 feet wide and would be designed to relay information about the moon´s atmosphere, soil, and origins. The rovers would also be fully autonomous, surveying the land without the need for human control. Making them autonomous could solve a few issues, said the research team. One issue would be a wheeled craft. While Mars´ high gravity makes it easy for a craft such as Curiosity to navigate the terrain, Phobos has a much weaker gravity and wheels would not hold traction as easily.

The robotic rovers, of which two have already been crafted and a third in development, would deploy from a “Surveyor” craft after a detailed probe of the terrain had been completed. Each rover would be deployed separately, a few days apart, to give scientists better coverage of the moon, and to determine the best possible landing zones.

The research team said the rovers could not only probe the Martian moon Phobos, but could also investigate asteroids and comets, all without the need for human control.

"It's the next level of autonomy in space,” said Marco Pavone, assistant professor at Stanford's Department of Aeronautics and Astronautics, and lead developer on the hedgehog rover system.

Pavone said the system could be ready for testing in 2 to 4 years. Once testing proves viability of the system, Pavone expects to send the Surveyor along with five or six hedgehog rovers to the Martian moon Phobos. Of course that could be a decade or longer before occurring.

The new system aims to work out the difficulties of sending a manned mission to the Red Planet as well. Sending humans to the Martian world would be extremely costly and comes fraught with many health obstacles. And with such a high gravity on Mars, it seems more plausible to land human astronauts on Phobos, especially if it can be proven that the moon originated from Mars, which the hedgehogs could help scientists determine.

Pavone said humans could study Phobos itself or use it as a base for robotic explorations of Mars. The moon could also serve as a site to test technologies for potential use in a human mission to the planet.

"It's a piece of technology that's needed before any more expensive type of exploration is considered," Pavone said of the spacecraft-rover system. "Before sampling we need to know where to land. We need to deploy rovers to acquire info about the surface."

The rovers are currently more cubical in shape than spherical. But the researchers hope that they can eventually design them to be more spherical, which would make them more traversable. It has been a tricky process designing a rover to travel over rough, rugged terrain, said the team.

"You can get into very hard rocky terrain, or very soft, almost like powder, terrain," said doctoral candidate Ross Allen. "Whatever's touching the ground needs to get traction on hard stuff without getting stuck on soft stuff... That's something that will require more work and testing."

Pavone and his team are currently developing test sites here on Earth that mimic low-gravity conditions as closely as possible. They hope to complete a test experiment by next summer, using a large overhead crane at the Durand Building in Stanford. The team will secure a hedgehog to the crane´s harness, which is attached to a spring device that will offload weight from the rover, emulating low-gravity effects.

Eventually, the team wants to test the hedgehogs in a reduced-gravity aircraft to further test the rovers´ capabilities.

The researchers initiated the spacecraft-rover project as part of the NASA Innovative Advanced Concepts Program. They will present a paper describing their platform's proposed mission at the Institute of Electrical and Electronics Engineers Aerospace Conference in March.