Tag: Mars 2020 Perseverance Rover wheel material

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Mars 2020 Perseverance Rover Structure Components Functions Movement Structure System of Mars 2020 Perseverance Rover

Wheels of Mars 2020 Perseverance Rover

The Mars 2020 Perseverance rover has 6 wheels. Different from its predecessor, each of the Mars 2020 Perseverance rover‘s wheels has a total of 48 gently curved treads instead of 24 chevron-patterned treads. For the wheels of our Perseverance Mars Rover Replica, all the curved treads will be perfectly replicated.

Other than changing the wheel patterns, the Mars 2020 Perseverance rover‘s wheels are around 8.5mm thick, which is around 1mm thicker than the Curiosity rover, not including the pattern thickness on the wheel surface. Proportionally, the thickness of our 1:2 Perseverance Mars Rover Replica‘s wheel should be 1mm, but in order for the wheels to be strong enough to support the rover body and the loads onboard and bear the rocky terrain, we will make the thickness of the Mars Rover Replica‘s wheel 2 mm.

The diameter of the Mars 2020 Perseverance rover‘s wheels is 52.5 centimeters or 20.7 inches, which is a little bit larger than the Curiosity Mars Rover’s 50.8-centimeter or 20-inch wheels. The diameter of the wheels of our 1:2 Perseverance Mars Rover Replica is 26.25 centimeters or 10.35 inches.

The reason to change the tire pattern and to make the Mars 2020 Perseverance rover‘s wheels thicker is due to the wear and tear that the Curiosity Mars rover’s wheels experienced. And this actually affects Curiosity’s performance on the Martian sand. But now with the new design, the Mars 2020 Perseverance rover‘s wheels are more resistant to the harsh Martian surface condition. The wheels of our 1:2 Mars Perseverance Rover Replica are strong enough as well to survive many kinds of rock terrains.

While the spokes of the wheel were made of titanium, the PMars 2020 Perseverance rover‘s tires were machined from aluminum that is widely used in the airplane industry, and it is a type of shape memory alloys. This shape-memory aluminum allows the tires to adapt to the Martian terrain, which is very much like a shock absorption system to provide the Mars 2020 Perseverance rover with a stable ride and minimize damages to the tires and hence to the instruments carried by the rover. The shape-shifting material makes the Mars 2020 Perseverance rover‘s tires light-weight, more durable and they have better traction performance while driving on the Martian rocky roads. For our 1:2 Mars Rover Replica, the spokes are made of aluminum and the wheel surface is made of steel. The reason we choose these two materials to build our Mars Rover Replica is explained in this post [Designing the Perseverance Mars Rover Replica’s Wheels].

With one full turn of the wheels, the Mars 2020 Perseverance rover can move forward a distance of 1.65 meters, or 65 inches. The Perseverance Mars rover can go as fast as 152 m/h, or 4.2 cm/s, which might not seem very fast compared to Earth’s vehicles, but the slow speed actually helps the Perseverance Mars Rover conserve energy for the long-term mission. In terms of our Mars Rover Replica, how fast it can go is still to be determined, but we will try to match the Mars 2020 Perseverance rover‘s speed.

Compared with the Curiosity Mar rover, the Mars 2020 Perseverance rover is much more autonomous in terms of driving. The software onboard allows the Mars 2020 Perseverance rover to decide which way it wants to go, which means the Mars 2020 Perseverance rover will travel much further without having to confirm with Earth each time about the driving paths. For our 1:2 Perseverance Mars Rover Replica, you will remotely control it with screens showing real-time video captured by the cameras mounted around the body of the Mars rover replica.

The Mars 2020 Perseverance rover‘s wheels work with a Rocker-Bogie suspension system when interacting with the surface of Mars. This Rocker-Bogie design allows the Mars 2020 Perseverance rover to go over obstacles twice the height of the wheel and allows the loads onboard evenly distributed on the 6 wheels. In our 1:2 Mars Rover Replica, the Rocker-Bogie feature is perfectly replicated, so you can expect that our Mars Rover Replica will also be able to drive over obstacles that are twice the height of its wheels and have the loads evenly distributed on 6 wheels.

Synonyms: cleats, raised treads, grousers

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1:2 Perseverance Mars Rover Replica Design and Building Diary

Building the Structure for the Drive Motor, the Wheel Fork, and the Steering Motor for the 1:2 Perseverance Mars Rover Replica

The Mars 2020 Perseverance Rover has six wheels, and each of them is connected to a stand-alone drive motor via the axle. And each of the front two wheels and the back two wheels is also connected to a stand-alone steering motor via a C shape structure called the wheel fork. Obviously, since the two middle wheels do not have steering motors connected, there are no C-shape wheel forks involved in the two middle wheels.

To test our design of the 1:2 Perseverance Mars Rover Replica, we 3D printed a prototype first including the structures for the drive motor, the wheel fork, and the steering motor for one wheel of our Perseverance Mars Rover Replica because the cost of 3D printing is much lower than machining, not just the material cost but the processing cost as well, and what’s more, 3D printing is much faster than machining. So if we find any design mistake when building the prototype, we can adjust the 3D design without wasting too much money. Of course, small issues don’t necessarily require re-3D-printing immediately, we can use all kinds of tools to do the fix in the physical world so that we won’t be stopped by these small issues.

After we complete the 3D printed prototype test and the design changes, which obviously may involve more than one round, we then proceed to build the final aluminum version wheel structure of the 1:2 Mars Perseverance Rover replica.

As you can see in the video above, all the 3D-printed parts are perfectly assembled. Some of the parts are already now machined with aluminum alloy.  Once we build the control PCB for the steering motor and drive motor, we will be able to activate the wheel via the code running in microchips.

We are now moving on to build the mast of the 1:2 Perseverance Mars Rover Replica.

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1:2 Perseverance Mars Rover Replica Design and Building Diary

Designing the Perseverance Mars Rover Replica’s Wheels

The wheels of the Mars 2020 Perseverance Rover are made of special aluminum. There are cleats on the outer surface to add traction. This is actually the first challenge during our building journey of the Perseverance Mars Rover Replica.

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The rendered screenshot of the Perseverance Mars Rover Replica wheel design

The special aluminum NASA used to build the Mars 2020 Perseverance Rover’s wheels is obviously very tough so as to bear at least 1/6 weight of the real Perseverance Mars Rover of which the total weight is 2,260lb or 1,025kg. When the Mars 2020 Perseverance Rover driving over the uneven Martian terrain, each wheel may have to bear up to 1/5 weight or even more of the Mars 2020 Perseverance Rover. But the real challenge comes from the cleats. The cleats of the 1:3 Perseverance Mars Rover replica’s wheels are only around 2mm thick. Unless we could find a kind of really awesome aluminum, the 1:3 cleats will easily break on terrains with sharp rocks due to that the burden of a single wheel will all come to the contact point between the cleat and the rock.

The endurance of the wheels of Perseverance Rover’s predecessor – Curiosity Rover is actually good but while driving over sharp, pointy rocks they did break. Mars 2020 Perseverance Rover’s wheels are redesigned to be more robust – narrower than Curiosity’s, but bigger in diameter, 20.7 inches (52.6 centimeters) versus 20 inches (50.8 centimeters) and made of thicker aluminum, have twice as many treads and are gently curved instead of chevron-patterned. But still, they will damage if the terrain harshness is beyond their design standard.

When we choose the material for the 1:3 Perseverance Mars Rover replica’s wheels, our goal is to build them to withstand pressure from almost all kinds of terrains. The reason is quite simple – people would love to enjoy the excitement of manipulating the 1:3 Perseverance Mars Rover replica on terrains similar to Mars but they also would love to see all parts intact after each and every ‘mission’. Dust is OK but damages are definitely a heartbreaker.

In the end, after weighing the pros and cons, we decided to use steel to build the 1:3 Perseverance Mars Rover replica’s wheels. The building cost of each 1:3 Perseverance Mars Rover replica’s wheel is around 1,000 USD. Six wheels are almost 6,000 USD. The cost is high but they don’t break. They are heavy than aluminum but the 1:3 Perseverance Mars Rover replica doesn’t go on the rocket.

A close-up image showing the broken position on Curiosity rover’s left-middle wheel. Credit: NASA/JPL-Caltech/MSSS
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Displacement analysis of the Perseverance Mars Rover Replica’s wheel
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Displacement analysis of the Perseverance Mars Rover Replica’s wheel
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1:2 Perseverance Mars Rover Replica Design and Building Diary

Why 1:3? – Choosing the Size Ratio of the Perseverance Mars Rover Replica

When we first had the idea to build the Perseverance Mars Rover replica, we set the goal as making the Perseverance Mars Rover replica ultra-realistic – looks the same and moves the same as the Mars 2020 Perseverance Rover but with no science instruments.

We had some arguments about the size ratio at the beginning. 1:1, 1:2, and 1:3 seemed to be the three natural candidates.

1:1 Perseverance Mars Rover replica was eliminated first because it is too heavy and too expensive.  The Mars 2020 Perseverance Rover is 1,025 kg or 2,260 lb. The 1:1 Perseverance Mars Rover Replica will not as heavy as the real one but should be around 600 kg or 1,322 lb. The most tricky part is the spokes. The Mars 2020 Perseverance Rover’s spokes are made of titanium, however, it will be way too expensive for us to build the 36 spokes that way. If we use other materials, the building cost is still too high. Moreover, the heavyweight is a big challenge for all the connection structures which requires material and processing and assembly techniques up to a certain high level which is not proper for our first Perseverance Mars Rover replica project.

Unless we spent tons of effort doing simulations and tests in the physical world so as to be 100% sure that it is feasible for all the critical structures to bear the weight of the 1:1 Perseverance Mars Rover replica, any further effort in designing and building the 1:1 replica might be a waste of time. After all, we are not as rich as NASA. We cannot endure waste and risk more than we can afford at this stage.

Then the competition was between 1:2 and 1:3. We hesitated between these two options because each has its advantages and disadvantages and the scores were close. Technically speaking, the difficulties of building Perseverance Mars Rover replicas of these two ratio sizes were very close although the 1:2 did prevail a little bit on most aspects. However, since the 1:2 Perseverance Mars Rover replica is approximately 2.4 times larger than the 1:3, the cost of everything is at least doubled or even more.

On the other hand, the main challenge of the 1:3 comes from its relatively small size against its motorized parts, especially the iconic long arm that carries multiple sensors and cameras and the heavy drill set. Although it is not our goal to build any functional science instruments on our Perseverance Mars Rover replica, we do set the goal to build all the visible parts move the same way as those components of the Mars 2020 Perseverance Rover do. That’s saying that since the Mars 2020 Perseverance Rover can drill on Mars, our Perseverance Mars Rover replica should have the ability to drill on Earth, or at least drill like real.

There is a possibility that the weight of the 1:3 Perseverance Mars Rover replica’s arm was too heavy to be motorized without compromising the joint shapes simply because the arm joints need larger motors to lift the weight but its internal space won’t allow them to accommodate motors of such sizes. Of course, we did estimations and simulations about the torques required and the torques could be provided by the motors of suitable sizes. It turns out that the required and the provided are close. Therefore, we need the exact weight of the component which highly depends on the exact structure design. therefore, the only way to make sure we can make the 1:3 arm for the Perseverance Mars Rover replica was to complete the exact design if not build it physically. But we believe there is a good chance for the 1:3 Perseverance Mars Rover replica to achieve the pre-set goal.

Therefore, we decided to choose the 1:3 Perseverance Mars Rover replica as a start. It is the cheapest among the three candidates, and it is very likely to hit the goal.

Well, cheap is relative. Even the 1:3 Perseverance Mars Rover replica should cost us at least 200,000 USD before we can complete the first prototype. The 1:2 replica is around 300,000 USD while the 1:1 is around 500,000 USD.

>> Related Information

The original dimensions of the body box of the Mars 2020 Perseverance Rover are as follows.

  • Length 10 feet (3 meters)
  • Width 9 feet (2.7 meters)
  • Height 7 feet (2.2 meters)

Therefore, the dimensions of the body box of the 1:3 Perseverance Mars Rover replica are as follows.

  • Length 3 feet 4 inches (1 meter)
  • Width 3 feet (0.9 meters)
  • Height 2 feet 4 inches (0.73 meters)