Category: 1:2 Perseverance Mars Rover Replica Design and Building Diary

To design and build the 1:2 Perseverance Mars Rover Replica, it involves information collection, 3D modeling, material choosing, computer simulation, 3D printing, laser cutting, CNC, advanced assembly, tests, more tests, re-design, re-building, more tests, finalizing prototypes, more tests, general assembly, general evaluation, and finalizing the final replica.

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1:2 Perseverance Mars Rover Replica Design and Building Diary

Building and Testing the Wheel Skeleton of the Mars Perseverance Rover Replica

We have completed the machining of the wheel spokes of the 1:2 Mars Perseverance Rover replica. All the parts are assembled. It is really exciting to hold the assembled wheel skeleton in my hands and feel its weight. Although the structure successfully passed the computer simulations, we still anticipated seeing its bearing ability in the physical world.

We designed a special tool to test the entire wheel of the 1:2 Mars Perseverance Rover replica, including the steering motor structure, the ‘C’ shape connection structure, the wheel hub, and the spokes. In this stage, we only completed the wheel skeleton which is composed of the wheel hub, and the spokes so we cannot take advantage of that special tool to do the test. However, we did find a very primitive but effective way to test the strength of the wheel skeleton of the Perseverance Mars rover replica.

We were worrying whether this skeleton structure can bear the weight of the entire Perseverance Mars rover replica so it’s really nice to see the structure is STRONG. LOL.

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1:2 Perseverance Mars Rover Replica Design and Building Diary

1:2 Perseverance Mars Rover Replica

After doing some tests in the physical world, we decided to upgrade the size of the Perseverance Mars Rover Replica from 1:3 to 1:2, and therefore the static Perseverance Mars Rover replica will be upgraded from 1:4 to 1:3.

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 1:2 Perseverance Mars Rover Replica are as follows.

  • Length 5 feet (1.5 meters)
  • Width 4 feet 6 inches (1.35 meters)
  • Height 3 feet 6 inches (1.1 meters)
Mars Perseverance Rover Replica ratio size compare
Mars Perseverance Rover Replica ratio size compare
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1:2 Perseverance Mars Rover Replica Design and Building Diary

Designing the Spokes of the Wheels of the Perseverance Mars Rover Replica

As I mentioned in my previous diaries, the spokes are a challenge in the design and building of the 1:3 Perseverance Mars rover replica.

spokes design Perseverance Mars rover wheel buymarsrovers
The spoke design of Perseverance Mars rover replica’s wheel.

The wheels of the Mars 2020 Perseverance Rover are connected to their axes via bent spokes. In each wheel, there are six spokes.

These twisted spokes were bent twice in two directions from the wheel axis to the inner surface of the wheel. These specially designed spokes serve as a mechanical spring system contributing to buffer bumps during the Perseverance rover’s journey on Mars, while at the same time, they together bear the weight of the entire Perseverance Mars rover.

The spokes of the Mars 2020 Perseverance rover are made of titanium but we will use aluminum or steel to build them in our 1:3 Perseverance Mars rover replica. To ensure that the two bendings of each spoke in the 1:3 Perseverance Mars rover replica mold accurately as the design, we designed a special tool for the bending operation.

Since we will build the 1:4 Perseverance Mars rover static replica first, we will test our spoke design in the 1:4 replica first.

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1:2 Perseverance Mars Rover Replica Design and Building Diary

A 1:4 Mars Perseverance Rover Static Replica First

We realize the job to build an ultra-detailed Mars 2020 Perseverance Rover replica with all the parts motorized movable exactly the way as the one on Mars is more difficult than we thought at the beginning. Therefore, we plan to build a 1:4 Mars Perseverance rover static replica before we physically build the 1:3 motorized one. All the movable components of the 1:4 Mars Perseverance rover static replica can at least do the same actions as the real Mars 2020 Perseverance Rover replica can manually, while for some components we will design motorized mechanical structure.

As I mentioned in my first two diaries, the major two challenges in the design and building of the Mars 2020 Perseverance Rover replica are the wheels and the robotic arm.

The wheel tread challenge is solved already using steel instead of aluminum, although the spokes are another challenge in wheels.

However, the 1:3 Perseverance Mars rover replica’s long robotic arm with a heavy turret at the end of it is THE big challenge. All the mechanical structures, especially the motorized structures, require a high level of machining accuracy, motors with high ratio gearbox to provide large torques, and little compromising to the external shape in all positions.

Our technologies can achieve the goal for sure but it is always sweet if we can plan something to facilitate this journey.

One good option is to build a 1:4 Mars Perseverance rover static replica first. A smaller model is a widely used approach in industrial design and mechanical engineering which allows designers and engineers to verify designs in a much more cost-efficient way.

In our 1:4 Mars Perseverance rover static replica, we will keep the following features.

  1. precise external shape and detail replica to the Perseverance Mars rover.
  2. functional wheels with their own individual motors and the “rocker-bogie” suspension system exactly as they are in the Perseverance Mars rover.
  3. mast with motors can do exactly the same actions as the Perseverance Mars rover can
  4. steerable X-Band High-Gain Antenna can do exactly the same actions as the Perseverance Mars rover can
  5. a simplified remote control
  6. maybe more features

We are also considering building the long robotic arm with light-duty motors to realize all the same actions as that of the Perseverance Mars rover. To reduce the challenge, the turret will be just an empty shell so as to minimize the weight but keep the appearance.

Meanwhile, we will also build another version of the long robotic arm for the 1:4 Perseverance Mars rover replica. In this version, all the internal motorized mechanical structures to realize the drill function, cameras, electronic components will be designed and built into the turret so that we can have a relatively precise estimation of the weight for the turret in the 1:3 Perseverance Mars rover replica. What’s more, the arm will be thoroughly designed to have all the external details and internal motorized mechanical structure while the motors will not be installed inside joints. Instead, in those positions, there will be specially designed bearing structures to allow manually pose change for the arm. This specially built arm will help us get a relatively precise estimation of the torque required in each joint of the robotic arm in the 1:3 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
Perseverance Mars Rover Replica wheels design buymarsrovers.com 2
Displacement analysis of the Perseverance Mars Rover Replica’s wheel
Perseverance Mars Rover Replica wheels design buymarsrovers.com 2
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)