In April 2009, a NASA rover was exploring the surface of Mars when it rode into soft sand and got trapped on the planet. Now, researchers at the Viterbi School of Engineering say that they have created a potential solution: a four-legged, dog-like robot designed to help rovers escape dangerous terrain.

The three-person research team, in partnership with NASA and five other universities, has been developing and training the robot — aptly named Spirit — which, according to Austin Tsai, a junior majoring in computer engineering and computer science, can simultaneously pull the rover out and prevent future equipment from getting trapped in the first place.

Last summer, Jeongwoo Cho, a second-year graduate student studying mechanical engineering and a project leader, traveled to White Sands National Park in New Mexico — whose terrain mirrors the surface of Mars — to test the robot’s effectiveness. Cho and his team purposely trapped a rover in sand to see how the new legged robot would respond.

“We were able to bring a legged robot in, and then dock it together so it becomes one connected thing, and then it was able to help pull [the rover] out,” Cho said. “That’s something really novel that hasn’t been explored before.”

Unlike typical rovers, which rely on wheels to get around, Cho said that Spirit is unique because its legs enable it to traverse areas that rovers cannot without possibly getting stuck.

Tsai, a member of the research team, said that with every movement, the robot gathers data on how compact or loose the ground is below it.

“It’s simultaneously locomoting, which is like it’s moving, while also doing science experiments for every step,” Tsai said. “We are there to map out the terrain.”

Cho said that the robot can prevent future rovers from becoming stuck because each leg collects data measuring the stiffness of the ground.

“If you have a robot, scout out an area first, right? It goes around and clicks on the stiffness measurements, then it can create a stiffness map,” Cho said. “So then, as a rover, naturally, you will want to follow the path of more stiff areas, right? So that you don’t get stuck.”

The unique robot has been developed through three separate NASA-funded programs: Legged Autonomous Surface Science in Analogue Environments; Legged Autonomous Surface Science In Analog Environments for Mars; and Temporarily, Robots Unite to Surmount Sandy Entrapments, then Separate.

The LASSIE projects focused specifically on mapping out the terrain properties of the Moon and Mars, according to Tsai.

Tsai said that saving wheeled rovers from loose sand and communicating directly with other robots about the stiffness of the ground falls under the purview of the TRUSSES project.

Cho said that rovers and legged robots each have distinct advantages that can be maximized when working together.

“In a collaborative environment and planetary exploration, you can have rovers carry around a bunch of stuff, right? If it gets stuck or something, legged robots can come and help push it out, or something like that,” Cho said. “That’s the idea of the whole TRUSSES project — teamwork between different types of robots.”

Shipeng Liu, a USC alum and previous member of the research team, credited the University’s top-notch engineering resources, collaborators from other universities, NASA’s Jet Propulsion Laboratory and Los Angeles’s local beaches for making the robot’s development possible.

“We would just conduct easy field testing on an L.A. beach, because that would give us a little bit more [of] an overall picture about what our technology can do and cannot,” Liu said. 

After initial tests on local beaches, the research team brought their creation to Mount Hood National Forest in Oregon and White Sands National Park in New Mexico to replicate the terrain found in space, said Cho.

Tsai said that the team hosted a demonstration of its Spirit robot on March 17 and 18 at the NASA Ames Research Center in Moffett Field, California, in front of the project’s funders, NASA and industry professionals.

With that demonstration complete, Cho said that this stage of the project is coming to an end.

Liu said whether the Spirit robot ever makes it to space also depends on new funding, and companies in the space industry will have to invest in making the robot capable of surviving in space’s harsh environment. For example, a 2020 NASA Mars rover required $2.1 billion in funding to launch and land on Mars, according to SpaceNews. 

“It’s up to the professors to propose the next projects, and then it’s up to whether funding is available, and if institutions like NASA are interested in funding stuff like that,” Cho said.