Perseverance mobility system - Summary reader's response draft 3

According to NASA’s webpage on rover wheels, the mobility system of the Perseverance rover stands out among Martian vehicles. The rover can travel at speeds of 4.2 cm per second and consumes less than 200 watts. The mobility system consists of the driving and suspension systems. The driving system consists of six wheels fitted with brushless DC motors, accompanied by extra steering motors in the front and rear legs (NASA, 2019). These wheels, measuring 52.5 cm in diameter, are crafted from an aluminium alloy with titanium spokes. The wheels have individually modified “EC 32 flat drive” motors (Maxon, 2020) and retrofitted cleats to enhance traction. The legs are constructed from titanium tubing, enabling the rover to traverse uneven Martian terrain, overcoming obstacles surpassing 40 cm in height (NASA, n.d). The suspension system, identified as the "rocker-bogie" system, is composed of three interconnected components: the differential, rocker, and bogie. These elements collaborate to receive information from the internal measurement unit and efficiently distributes the rover's weight across its six wheels. This intricately designed system minimises tilt during traversal over uneven Martian terrain, thereby enhancing the rover's overall stability (NASA, n.d). Compared to the previous Martian rovers, the Perseverance rover’s mobility system exhibits remarkable improvements in speed and rate of ground covered, enhancing its capability to fulfil the mission objective of exploring the geography of the area. The improved ground coverage rate is largely due to its upgraded navigational system. According to NASA’s webpage on rover cameras, the navigational system consists of two navigation cameras (Navcams) and six hazard avoidance cameras (HazCams). The Navcams are primarily used to navigate the rover safely and can be found on the rover's mast, while the HazCams are positioned at the front and rear of the rover's body, detecting hazards and obstacles that were missed out by the Navcams. Images from these cameras are sent to two central processors, analysing them in real-time as the rover moves over Martian terrain. These processors provide concurrent information, identifying optimal paths and location of obstacles to allow the rover to transverse the martian terrain efficiently (Rankin et al., 2023). Perseverance exhibits superior mobility compared to previous Martian rovers, enabling it to traverse the Martian terrain at a significantly faster pace. In a study on the Perseverance rapid traverse campaign (Rankin et al., 2023), it was found that Perseverance achieved speeds of 4.2 cm per second, covering a distance of 5 km in 31 sols (Martian days). In contrast, previous Martian rovers, such as Opportunity and Curiosity, required 96 and 240 sols respectively to cover the same distance. This substantial difference in traversal time can be attributed to Curiosity and Opportunity lacking the capability for continuous travel; they required to halt and assess their location after moving every few seconds, achieving speeds of 4 cm per second and 1 cm per second, respectively. Due to Perseverance's ability to explore more Martian terrain at an accelerated rate, the rover managed to sample 23 locations during its first 1000 sols on Mars (NASA, n.d), while its predecessor Curiosity sampled only 11 locations in the same period (Abbey et al., 2020). The enhanced mobility has allowed the rover to reach high-priority science targets at a faster rate, allowing scientists to analyze and review more Martian terrain.

  Compared to the Curiosity rover, one potential challenge the Perseverance rover's mobility system may encounter is the accelerated wear and tear of its wheels due to covering higher mileage at a faster rate. According to NASA's Jet Propulsion Laboratory (JPL) webpage on Premature Wear of the MSL Wheels (2017), Curiosity experienced progressive damage to its wheels attributed to metal fatigue. This fatigue resulted from repeated stress while traversing sharp rocks, led to wheel deformation and fractures. Although Perseverance's wheels are narrower, they are thicker and have a larger diameter compared to Curiosity's. These features coupled with the enhanced navigation system were implemented to mitigate the risk of wheel damage on Perseverance. However, the increased rate of travel may subject Perseverance's wheels to a higher risk of metal fatigue, potentially jeopardizing the rover's functionality. In such a scenario, scientific experiments and exploration missions on Mars conducted by the Perseverance rover could be delayed or terminated in the worst-case scenario. The increase in scientific sampling at high-priority science targets, facilitated by the faster rate of ground coverage and enhanced navigational systems compared to the Curiosity rover, demonstrates the enhanced ability of the rover to fulfil its mission objectives of exploring the Martian geography, uncovering scientific discoveries that could pave the way for human life on Mars. Despite the potential risk of faster metal fatigue on the rover's wheels due to these improvements, the accelerated rate of scientific analysis of Mars enables the rover to fulfil its mission objectives faster than ever before. References

Abbey, W., Anderson, R., Beegle, L. W., Peters, G., Morookian, J. M., Biesiadecki, J., Carsten, J., Collins, C., Davis, K., Kinnett, R., Klein, D., … Vasavada, A. R. (2020). A look back, part II: The drilling campaign of the curiosity rover during the Mars Science Laboratory’s second and Third martian years. Icarus, 350, 113885.  https://www.sciencedirect.com/science/article/pii/S0019103520302657?via%3Dihub Maxon. (2020, July 7). maxon DC motors are heading to Mars onboard NASA's Perseverance rover.  https://www.maxongroup.net.au/medias/sys_master/root/8843051204638/maxon-DC-motors-are-heading-to-Mars-onboard-NASA-s-Perseverance-rover.pdf NASA. (2022, April 8). How Perseverance Drives on Mars. https://mars.nasa.gov/resources/26660/how-perseverance-drives-on-mars/ NASA. (2017, September 26). Premature Wear of the MSL Wheels.  https://llis.nasa.gov/lesson/22401 NASA. (n.d.). Curiosity’s and Perseverance’s wheels – NASA mars exploration.  https://mars.nasa.gov/resources/24910/curiositys-and-perseverances-wheels/ NASA. (n.d.). Mars Rock samples. NASA Mars Exploration.  https://mars.nasa.gov/mars-rock-samples/#23 NASA. (n.d.). Wheels. https://mars.nasa.gov/msl/spacecraft/rover/wheels/ NASA. (n.d.). Rover Brains. https://mars.nasa.gov/mars2020/spacecraft/rover/brains/ NASA. (n.d.). Rover Cameras. https://mars.nasa.gov/mars2020/spacecraft/rover/cameras/ NASA. (n.d.). Rover Wheels. https://mars.nasa.gov/mars2020/spacecraft/rover/wheels/ Rankin A., Sesto T., Hwang P., Justice H., Maimone M., Verma V., Graser E., (2023, May 15). Perseverance Rapid Traverse campaign. https://ieeexplore.ieee.org/document/10115835/