Perseverance mobility system - Summary reader's response draft 1

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 4.2cm per second and consumes less than 200 watts. The mobility system consists of the driving, suspension, and navigational 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 3-axis position information from the internal measurement unit (IMU) and efficiently distribute the rover's weight across its six wheels. This intricately designed system minimizes tilt during traversal over uneven Martian terrain, thereby enhancing the rover's overall stability (NASA, n.d). The navigational system consists of 2 navigation cameras (Navcams) and 6 hazard avoidance cameras (HazCams). The Navcams are located on the rover's mast and is primarily used to navigate the rover safely, while the HazCams are located at the front and rear of the rover's body, detecting hazards and obstacles as the rover moves (NASA, n.d). These cameras work together with the rover's 2 central processors to process and analyse images as the rover transverses along the rocky Martian terrain, avoiding hazards and obstacles as it moves. In contrast to the mobility system on Perseverance, which achieves an average speed of 4.2 cm per second, the mobility systems of preceding Martian rovers show slower performance. For instance, the Curiosity rover maintains an average speed of 4 cm per second, while the Opportunity rover operated at a more modest 1 cm per second. Compared to the previous Martian rovers, the Perseverance rover’s mobility system exhibits remarkable improvements in speed and rate of ground covered, enhancing the ability of the rover to explore the geography of the area at a faster rate.  

Perseverance exhibits enhanced mobility as compared to the previous Martian rovers. In a report on the Perseverance rapid transverse campaign (Rankin et al., 2023), Perseverance could achieve average speeds of 4.2 cm per second, covering 5km in 31 sols (Solar day). The previous Martian rovers, opportunity and curiosity took 96 and 240 sols respectively to cover the same distance. Due to the enhanced mobility of the rover, it could cover a larger distance in a shorter period. This allowed scientists to analyze and review more Martian terrain, and get the rover to high-priority science targets at a faster rate. Also, due to Perseverance's ability to review more Martian terrain, Perseverance managed to sample 23 locations during its first 1000th Sol on mars (NASA, n.d), while its predecessor Curiosity sampled only 11 locations in the same period (Abbey et al., 2020).  

Compared to the Curiosity Rover, one problem the Perseverance's mobility system could face is faster damage to its wheels due to its higher mileage covered at a faster rate. According to JPL's webpage on Premature Wear of the MSL Wheels (2017), Curiosity faced progressive damage to its wheels due to metal fatigue. The metal fatigue, caused by the repeated stress from driving over sharp rocks caused a weakened condition in the wheels, resulting in deformation and fractures. Although the width of the wheels on Perseverance are narrower, the wheels are thicker and have a bigger diameter as compared to Curiosity. Due to the faster rate of travel, Perseverance's wheels may experience a faster rate of metal fatigue, eventually crippling the rover, causing scientific experiments and exploration of Mars with the Perseverance rover to halt. 

In conclusion, the increase of scientific sampling at high-priority science targets due to faster rate of ground covered as compared to the Curiosity rover, shows the enhanced ability of the rover to fulfil its mission objectives of exploring the Martian geography and finding scientific discoveries that could help with paving the way for human life on Mars. Although, the improvements of the rover could cause a faster rate of metal fatigue on the wheels, the enhanced rate of scientific discoveries on Mars could still fulfil the mission objectives faster than ever before.  

References 

A. Rankin, T. del Sesto, P. Hwang, H. Justice, M. Maimone, V. Verma, E. Graser, "Perseverance Rapid Traverse Campaign," 2023 IEEE Aerospace Conference, 7 March 2023, 07 March 2023.  

Abbey, W., Anderson, R., Beegle, L. W., Peters, G., Morookian, J. M., Biesiadecki, J., Carsten, J., Collins, C., Davis, K., Kinnett, R., Klein, D., Kuhn, S., Logan, C., Maimone, M., Melko, J., Okon, A., Reid, J., Robinson, M., Singer, J., … 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 (New York, N.Y. 1962), 350, 113885-. https://doi.org/10.1016/j.icarus.2020.113885  

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. (n.d.). Curiosity’s and Perseverance’s wheels – NASA mars exploration. https://mars.nasa.gov/resources/24910/curiositys-and-perseverances-wheels/

NASA. (2022, April 8). How Perseverance Drives on Mars https://mars.nasa.gov/resources/26660/how-perseverance-drives-on-mars/  

NASA. (n.d.). Wheels. https://mars.nasa.gov/msl/spacecraft/rover/wheels/  

NASA. (n.d.). Mars Rock samples. NASA Mars Exploration. https://mars.nasa.gov/mars-rock-samples/#23 

NASA. (2017, September 26). Premature Wear of the MSL Wheels. https://llis.nasa.gov/lesson/22401  

NASA. (n.d.). Rover Wheels. https://mars.nasa.gov/mars2020/spacecraft/rover/wheels/  

NASA. (n.d.). Rover Brains. https://mars.nasa.gov/mars2020/spacecraft/rover/brains/  

NASA. (n.d.). The Rover’s wheels. https://mars.nasa.gov/mer/mission/rover/wheels-and-legs/