Tag: Mars Perseverance rover weight

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Sample Handling System of Mars 2020 Perseverance Rover

Robotic Arm the Mars 2020 Perseverance Rover

The Mars 2020 Perseverance Rover‘s robotic arm is located on the front of the rover’s chassis. It has a length of 7 feet or 2.1 meters, which is the same length as its predecessor, the Curiosity rover.  Our 1:2 Mars Rover Replica‘s robotic arm has a length of 3.5 feet or 1.05 meters. The Mars 2020 Perseverance Rover‘s robotic arm wields a rotating 45kg (or 99 lbs) turret assembly, which is 15kg (or 34 lbs) heavier than the Curiosity rover’s turret assembly because it carries bigger science instruments and a bigger corer for drilling compared to the Curiosity rover. The weight of our Mars Rover Replica‘s robotic arm will not be that heavy, because the instruments on it will only be decorations (but ultra-realistic decorations), and the material we use will be lightweight.

The purpose of the Mars 2020 Perseverance Rover‘s robotic arm is to help with exploring the Martian surface and collecting valuable Martian samples. It mimics the human arm – it has joints at its “shoulder”, “elbow” and “wrist” for maximum degrees of freedom. Our Mars Rover Replica‘s robotic arm will also have as many degrees of freedom as the real Mars 2020 Perseverance Rover‘s robotic arm. If the Mars 2020 Perseverance Rover is a human scientist, then the robotic arm is his human arm. At the end of the robotic arm, there is a turret assembly or a hand, and on the hand, there are the science instruments (SHERLOC, WASTON, PIXL), the gDRT, the Corer, and the ground contact sensor which are for Martian rock and soil sample caching. The gDRT and the ground contact sensor are introduced in [Turret of the Mars 2020 Perseverance Mars Rover].

There are some small motors or rotary actuators on the Mars 2020 Perseverance Rover‘s robotic arm, and with these actuators, the Mars 2020 Perseverance Rover‘s robotic arm has 5 degrees of freedom or 5 flexible joints: the shoulder azimuth joint, the shoulder elevation joint, the elbow joint, the wrist joint and the turret joint. Our Mars Rover Replica‘s robotic arm will also have these motors – not the same type or the same size, but the function of the motors is the same –  so that the Mars Rover Replica‘s robotic arm is also 5 degree of freedom. The flexibility of the Mars 2020 Perseverance Rover‘s robotic arm allows it to rotate the turret accurately to a location of interest so that the corer can start its initial abrading operation for the later sampling process, or for the science instruments analyzing process.

After the science team on Earth decides which rocks or regolith to sample, Mars 2020 Perseverance Rover will give the robotic arm the “go” for sample caching. The Mars 2020 Perseverance Rover’s robotic arm will rotate the corer to an angle that is best for the drill bit to operate. Depending on the condition of the drilling site, the drill will choose the rotary mode or the percussive mode for the sample caching. After the sample rocks or regolith are collected, the Mars 2020 Perseverance Rover’s robotic arm will transfer the sample tubes to the bit carousel for the later processes. Although the Mars Rover Replica‘s robotic arm doesn’t have the function like the real Mars 2020 Perseverance Rover, users can control the Mars Rover Replica to drive and mimic the movement of the robotic arm.

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Science Instrument of Mars 2020 Perseverance Rover

MOXIE of the Mars 2020 Perseverance Rover Part 1

Mars’ atmosphere has around 96% carbon dioxide and there is only 0.13% oxygen. Therefore, it is not suitable for humans to breathe. To find out if it is possible for human exploration on Mars, one of the most important things is to figure out how to make oxygen, not only for humans to breathe but also for helping with burning rocket fuel. The Mars 2020 Perseverance rover‘s MOXIE (short for the Mars Oxygen In-Situ Resource Utilization Experiment) is the instrument that will make oxygen from Mars’ atmosphere. It is like an artificial plant, breathing in carbon dioxide and breathing out oxygen (also some byproducts such as carbon monoxide).

The Mars 2020 Perseverance rover‘s MOXIE instrument is located on the inside of the Mars 2020 Perseverance rover‘s right front belly. It has a mass of 17.1 kg, but due to different gravitational forces between Earth and Mars, MOXIE weighs 37.7 lbs on Earth but 14.14 lbs on Mars. The Perseverance Mars Rover’s MOXIE is expected to operate its first mission within 30 sols after it lands on Mars and passes all the health checkups.

The Mars 2020 Perseverance rover‘s MOXIE is inside of the rover’s body, and you cannot see it from the outside, so our 1:2 Perseverance Mars Rover Replica might not replicate it, or we will replicate it after all the other components are completed. If we do replicate the PMars 2020 Perseverance rover‘s MOXIE instrument, our Mars Rover replica‘s MOXIE will not actually make oxygen, but the appearance structure will be replicated.

Interestingly, the Mars 2020 Perseverance rover‘s MOXIE has 2 microphones so we can hear it making oxygen on Earth. The reason for the microphones is because MOXIE runs by a motor. By listening to the motor running, engineers will know MOXIE is working. Even though our 1:2 Perseverance Mars Rover Replica might not replicate the MOXIE instrument, we may add a speaker inside of the Mars Rover Replica‘s body and make the motor running sound effects to simulate the MOXIE’s working sound.

The Mars 2020 Perseverance rover‘s MOXIE instrument only has a size of a car battery but once it is operating. If we replicate it on our Perseverance Mars Rover replica, it will be half the size of the real Mars 2020 Perseverance rover‘s MOXIE. When operating, the Mars 2020 Perseverance rover‘s MOXIE will use up to around 30% of the Mars 2020 Perseverance rover‘s power, and the heat generated will be so hot that the scientists had to insulate it. Otherwise, the instrument on board or even the whole of Mars 2020 Perseverance rover will get damaged. However, how hot it will get or how much voltage will be used are still to be found out during real operations on Mars.

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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)