Earth-based experiments reveal potential reasons why NASA's rovers repeatedly encounter issues and become stationary on Mars.
NASA Rover Challenges: The Missing Piece in Earth Testing
A new study published in the Journal of Field Robotics has shed light on a long-standing issue in the way NASA tests its rovers before sending them to Mars and the Moon. The study, led by a team of engineers from the University of Wisconsin-Madison, has highlighted the overlooked factor of gravity's effect on the sand itself.
The researchers found that the gravity on Earth pulls down on sand much more strongly than on Mars or the Moon. This difference in gravity's pull has a significant impact on the sand's rigidity, with Earth's gravity compacting the sand more firmly, making it less likely to shift under rover wheels. In contrast, the sand on the Moon tends to be fluffier, making it less supportive and causing rovers to lose traction and become stuck more easily.
This oversight could explain why simulated rover extraction plans that succeeded in Earth tests often failed on lunar or Martian terrains. For instance, the six-wheeled Spirit rover, which got stuck on the sandy Martian surface in the spring of 2019, was unable to be freed despite months of attempts by NASA. The same issue occurred with the Opportunity rover, which got stuck in sand in 2005, and Curiosity, which got bogged down in soft terrain in 2014.
To address this issue, the team used advanced physics-based simulations with Project Chrono to better model rover mobility on "squishy" alien soils. By incorporating the effects of reduced gravity on both the rover and the granular soil, they discovered that the extraterrestrial surface material shifts more readily, reducing rover traction and mobility.
The team's findings suggest that rovers on extraterrestrial terrains, like the Moon or Mars, are more likely to struggle with getting their wheels stuck in less-cooperative sands. By accounting for the difference in gravity's pull on sand, NASA can better prepare its robots for the harsh terrain ahead.
Dan Negrut, a professor of mechanical engineering at UW-Madison and lead author of the paper, stated that considering the effect of gravity on the sand is necessary to get a better understanding of how rovers will perform on the Moon. He emphasised that understanding how sand behaves under the lighter gravitational pull of other worlds can help improve rover design, testing, and mission planning.
The study's team discovered the missing piece of the puzzle while simulating NASA's VIPER, a rover meant to launch to the Moon this year before its mission got cancelled. The new findings could have important implications for future lunar and Martian missions, ensuring that NASA's robots are better equipped to navigate the unique challenges posed by extraterrestrial terrains.
[1] Journal of Field Robotics [2] University of Wisconsin-Madison News [3] Space.com [4] The Verge
- The study, published in the Journal of Field Robotics, revealed that NASA has been overlooking the impact of gravity on sand, which affects rover mobility on Mars and the Moon.
- The researchers found that the difference in gravity's pull on Earth, Mars, and the Moon significantly influences the sand's rigidity, with Earth's gravity compressing the sand more than on other planets, potentially causing rovers to become stuck.
- By accounting for the effects of reduced gravity on both rovers and granular soil, as done in Project Chrono simulations, the team found that the extraterrestrial surfaces shift more readily, reducing rover traction and mobility.
- The new findings from the study could have significant implications for future lunar and Martian missions, ensuring that NASA's rovers are better designed, tested, and prepared to navigate the unique challenges posed by extraterrestrial terrains, as reported by Space.com and The Verge.
