Mobile robots could be the future of Mars exploration |  Digital Trends

Mobile robots could be the future of Mars exploration | Digital Trends

ETH Zurich

If you were a fly on the wall at the Rockhal concert hall in Luxembourg in September 2022, you would have been greeted by a strange sight: no bands or cheering crowds, but a place filled with 220 tons of lava. and stone, and groups of robots crawling across the dusty ground looking for weapons.

It was the second and final round of the European Space Agency’s (ESA) Space Resources Challenge, which invited research teams to bring their robotics and test their skills in searching for resources in a simulated lunar environment. The idea was to look at the bright visions of the next generation of robotic space probes that could help find and display lunar resources, such as water, necessary for future crewed missions.

One of the winning teams in the challenge was a group of three-legged robots that floated, climbed, and moved around the stadium, working together to map, identify, and collect scientific samples. Although this challenge was focused on the moon, the same principles can be applied to robots aimed at Mars and other planetary bodies – and this method can allow robots to explore new areas that have not been seen before.

We spoke with Hendrik Kolvenbach of the Robotic Systems Lab at ETH Zurich, the group that develops legged robots, to learn more.

An idea with legs

Lunar Exploration Robots

Desired moonboats are not built from scratch; they started as commercially available robots from ANYbotics, which makes legged robots similar to those from Boston Dynamics. These models are often used for industrial testing, but may also have potential for off-world testing.


The Robotics Systems Lab has adapted these robots and software, including adding a robotic arm to pick up rocks on the martian surface and experiment with different walking patterns to cope with changing terrain. Regarding the size of the average dog, the version of the robots used for the ESA challenge were able to carry a small load of up to 33 pounds, but Kolvenbach said that the new systems can carry up to 110 pounds.

It is enough for a legged robot to carry scientific equipment such as cameras, spectrographs, or a small drill. Robots are trained using reinforcement learning, so they learn to navigate complex environments using simulation. They can learn to use their three legs to stand while using their fourth legs to produce and manipulate objects in their environment.

The ultimate goal of that research is to create modular hardware systems. Instead of space probes having to be built from scratch for every mission, future missions could take advantage of developing robotic technology here on Earth using a basic configuration that can be modified with different hardware and software as needed.

Kolvenbach compared it to the concept of CubeSats, a standardized interface and form factor that allows the integration of different payloads, making space development cheaper and making the hardware reusable.

Anonymous review

Wheeled robots like the Curiosity and Persistence rovers currently exploring Mars are good for other things. They move quickly over open ground, and can handle going around, or over, surprisingly large rocks and other obstacles. Even if their wheels inevitably sustain damage from years of rolling on martian terrain, as happened to Curiosity, they can keep going as long as the drivers are careful.

So why are legged robots necessary? It all depends on the circumstances that need to be explored by the mission. Both Mars and the moon have surfaces covered with dusty material called regolith, which rovers, for example, are designed to traverse.

But both places have interesting underground areas such as lava tubes, which are underground cave-like structures formed by an ancient process of hot lava.

ETH Zurich

These lava tubes are of great scientific interest, and there is also a real interest in using them as shelters for future manned missions as astronauts can establish underground bases in them and be protected from the harmful radiation on the surface. But no one knows exactly what these places are like, so any robot that hopes to explore them will need to be versatile and able to face unexpected challenges.

Legged robots are perfect for this type of environment. They are also suitable for tackling steep slopes, such as those found in potholes. That’s useful for regions like the far side of the moon, a current focus area for exploration that hosts permanently shadowed craters, and can host significant water ice reserves.

The slope can be difficult. “With wheeled robots, we always have a traction issue,” Kolvenbach said. “The regolith is dry, granular and has many conditions where rovers get stuck.”

Legged robots “go a long way, but they come at a price.” On flat surfaces with no major challenges, wheeled robots are more efficient and there is no need for heavier legged robots. For a more comprehensive study of the vast region, there is an option to explore from the air, as demonstrated by the Mars Ingenuity helicopter. But when it comes to rough and unimproved terrain, legged robots are “very fast and strong,” Kolvenbach said. “That’s where the unique value of these robots lies.”

Working as a team

One way to approach the challenges of robotics exploration is to consider the possibilities of teamwork. With each legged robot much smaller than the current Mars rover, many of them would be needed to carry the same load as a single wheeled robot. But that can be useful, as robots can work independently and in groups.

For the ESA challenge, the lab used a team of three-legged robots, although the team could theoretically be as large or as small as the task required. By changing the way different charges are distributed among team members, you can make robotic experts. For example, one robot may carry tools to rapidly map a large area, while another carries scientific tools to investigate specific points of interest in detail.

The trend now goes to these challenging areas, because there you can do the most interesting science.

This brings benefits of redundancy, as the most important tasks can be shared among team members. So if one robot fails for any reason, the others can still continue to work and take over most of the tasks of the failed robot.

As for how a group of robots can communicate with each other, there are many ways to consider a robot community. One is to have a central infrastructure that will coordinate the actions of each robot. That would be ideal for exploring large, open areas, as robots could be sent in different directions to perform tasks such as collecting samples, which could then be returned to base for analysis. Large and heavy equipment can sit in a central location, with robots acting as couriers.

Another way is to use contact points, robots that act as relays to send orders. That would be ideal for exploring underground regions where communication can be blocked. Robots can drop breadcrumb-like tracks to transmit commands, allowing them to communicate even in unfamiliar environments.

The real advantage of this method is flexibility. What payloads are paid for each robot, how many robots are part of a team, and how that team is organized can all be adjusted based on the needs of a particular task or location.

To space

The legged robots the researchers have been working with are commercial tools, so while they show promise for space exploration technology, they are far from perfect for space. Putting hardware on a space mission has strict requirements, from being able to withstand a wide range of temperatures, handling vibrations and shocks of launch, to the need for very high reliability, as there are no repair shops outside of Earth.

So in preparation, the team is working on a legged robot ready to fly into space called the Space Hopper. “It’s a relatively small robot,” Kolvenbach said. It weighs less than 22 pounds, and uses off-the-shelf spaceflight hardware. It was a pragmatic first step because ‚Äútransitioning from research prototype to real-world research is a lot of engineering work. So we decided to do something small. “

SpaceHopper: The next jump in robotic space | delivery in 2022

They hope the Hopper will be ready to fly as a technology demonstration within the next few years, just in time for space agency launches and commercial missions to the moon. Hopefully, it will open the door to further development of large and complex legged robots to explore new space.

Kolvenbach describes the future use of legged robots as “brainless.” There are many cases where a wheeled robot still makes sense to explore the planet, but when it comes to exploring more challenging and interesting areas of science, he sees legged robots as the future.

“There is a clear need for this,” he said. “We have done many missions in the past in a flat, easy space for other celestial beings. But the trend is now going to these more challenging areas, because there you can do the most interesting science. From the scientific community, there is clearly a need to go there. And legged robots are one emerging technology that could get us there to do that science. “

Editors’ Notes

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