Did you know that rubber tires are banned on Mars? Discover the hidden risks, the challenges of extreme temperatures and how NASA developed a revolutionary solution to ensure the success of missions on the red planet.
There are four vehicles rover on Mars, but the challenges of getting around the red planet continue to intrigue engineers and scientists. How space agencies deal with exploring such a hostile surface? And why aren't regular rubber tires viable on Mars?
If you were planning a long trip, you would probably do a thorough check-up on your car before you left. Checking the fluids, lights, and of course, the tires would be a must. But what if the trip was to Mars?
First, it's a good idea to make sure the heater is working properly, because temperatures there can reach -107°C.
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At this temperature, rubber stops being flexible and becomes brittle, like glass. Kicking a rubber tire on Mars could literally shatter it. This is reason enough to leave traditional tires out of rover designs.
Why is weight a problem on Mars?
Even if extreme cold weren't a problem, weight would be. Robust rubber tires with internal weaving and reinforced rims would add a load that rovers simply can't carry.
Mars missions need to optimize every gram transported. A spacecraft that is too heavy could compromise descent and landing, increasing the risk of a disastrous impact.
The surface of Mars is covered in regolith, a mixture of loose dust and rock fragments. This terrain is treacherous.
If the rover doesn't have an ideal weight distribution, it could sink or slide, putting the entire mission at risk before it even begins.
NASA Made a Lightweight, Yet Sturdy Wheel for Mars
NASA engineers have come up with creative solutions to overcome these challenges. In the case of the rover Curiosity, each wheel was machined from blocks of aluminum, making them incredibly light and thin. At just 0,75mm thick, the wheels sacrificed some durability to meet weight restrictions.
Each extra millimeter in wheel thickness could add about 10 kg to the total mass, which would require cuts in other equipment.
While this approach was critical to the mission’s success, it brought new challenges. The Martian surface turned out to be harsher than expected, with sharp rocks and conditions described as “shark teeth embedded in concrete".
This punishing terrain caused significant damage to the wheels of the Curiosity, with holes and tears that compromise its efficiency.
Locomotion challenges
The rovers suspension system is designed to distribute the load evenly. When a wheel hits an obstacle, the weight is redirected to the other wheels.
This can lead to unexpected pressures at certain points, resulting in greater damage than anticipated.
Holes in wheels are not just an aesthetic inconvenience. They increase resistance to movement, causing the rover consume more energy to move around. This extra energy could be used to perform scientific experiments or send data back to Earth, but instead it is spent just keeping the rover moving.
Improving the design
Faced with these problems, NASA is working on new wheel designs for future missions. The next generation of rovers, scheduled for launch in 2020, has brought the need for design changes.
The materials will likely remain the same, but the shape of the wheels will need to be adapted to better withstand the conditions of the Martian terrain.
In addition to sharp rocks, loose sand remains a major obstacle. The rovers’ wheels are equipped with grippers to improve traction in Mars’ reduced gravity, which is about 40 percent of Earth’s gravity. However, these grippers are not always enough to keep the rover from getting stuck.
The impact of gravity and surface
According to Dr. Terence Richards, an expert in spacecraft performance, the gravity and extreme dryness of Mars exacerbate locomotion problems.
The lack of moisture makes the regolith less compact, making it harder for the rovers to support their weight. When the wheels sink into the ground, rolling resistance increases, requiring more energy to move.
One potential solution is deformable wheels, which increase the contact area with the ground and distribute weight better. However, designing wheels that are lightweight, durable and capable of handling all of these challenges is still a tricky balance.
What we learned from rovers
Innovations developed for Mars rovers have applications beyond space exploration. In 2015, NASA demonstrated the Modular Robotic Vehicle, an electric vehicle that incorporated control technologies and independent wheels used in rovers.
It was energy efficient, easy to maneuver, and controlled by a joystick. While the vehicle is not commercially available, it shows how solutions for Mars can inspire innovations on Earth.
Mars exploration continues to be a learning journey. Each mission reveals new challenges, but also paves the way for technological advances that benefit not only space science, but also our daily lives.