(dr) David R. Scott / NASA
Astronaut Jim Irwin, pilot of the Apollo 15 mission, next to a lunar rover
Combining engineering principles from Leonardo Da Vinci and folding patterns from origami, scientists have created wheels for lunar rovers that easily adapt to the Moon’s treacherous geology.
Under the cratered surface of the Moon, there are networks of lava tubes and deep pits, natural caves that could house future lunar bases from cosmic radiation and sudden temperature variations. These underground structures represent some of the most scientifically valuable areas of the Solar System, but the The challenge of reaching them is enormous!
The entrances to these caves have steep and rugged terrain, with rocks and loose regolith. Small rovers, preferred for lunar exploration because they allow the sending of several of them, reducing mission risks, face an inherent limitation. Its compact wheels simply cannot overcome obstacles much larger than the diameter of the wheel itself. Sending a swarm of small scout vehicles allows even if some fail, others continue the mission. Sending a single large rover means that a single failure ends everything.
Variable-diameter wheels are a new addition to lunar exploration and could solve this problem, expanding when necessary to overcome obstacles and contracting for efficient transportation. But building a wheel like this for the Moon turned out to be practically impossible. The lunar environment is uniquely hostile to mechanical systems. The fine, abrasive dust infiltrates everything and, in the airless vacuum, the exposed metal surfaces adhere to each other through a process called cold welding. Traditional hinges and joints do not last long in these conditions.
A research team led by Professor Dae-Young Lee of the Korea Advanced Institute of Science and Technology (KAIST) has found an elegant solution by looking into the past. They combined principles of self-supporting bridge designs from Leonardo da Vinci with origami folding patterns to create a wheel that transforms without traditional mechanical joints.
The wheel uses an elastic metal frame and fabric tensioners that flex rather than rotate. This design can expand from a compact size of 230mm to 500mm in diameter, more than doubling its size. A small rover equipped with these wheels maintains a low profile during transport, but gains the climbing capability of a much larger vehicle when deployed to the lunar surface.
The team put the wheel through rigorous testing using artificial lunar soil. It demonstrated superior traction on unstable slopes and survived a drop impact equivalent to 100 meters in lunar gravity. The metallic structure proved to be sufficiently flexible to transform reliably and, at the same time, be rigid enough to support the weight of the rover on the loose regolith.
Dr. Chae Kyung Sim of the Korea Institute of Astronomy and Space Sciences emphasized the scientific importance, calling lunar craters “natural geological heritage” that this technology makes affordable. Dr. Jongtae Jang of the Korea Aerospace Research Institute noted that the wheel was optimized using thermal models to withstand temperature fluctuations of 300 degrees Celsius between lunar day and night.
Professor Lee expressed optimism that, despite remaining challenges with communications and power systems, this innovative technology positions the team as potential leaders in future lunar exploration missions, targeting the Moon’s mysterious subsurface frontier.
