NASA developed Spirit, a mobile exploration robot that moves on six wheels, for Mars exploration and landed it on the planet in 2004. But in 2009, the right rear wheel became stuck in sand, leaving it stranded. The mission shifted from roaming to stationary science, but communications were lost in March the following year.
Spectrum, published by the Institute of Electrical and Electronics Engineers (IEEE), said on the 3rd (local time) that a space exploration robot has been developed that has no wheels or legs, eliminating the risk of getting stuck in sand or tripping over rocks. It is RoboBall, a robot that rolls like a gym ball used to train core muscles at a health club. After a little over five years of development, a prototype was produced and succeeded in moving by bouncing across terrain similar to the lunar surface.
◇ Hopes for use in exploring inside lunar craters
Robert Amrose (Robert Amrose), a professor of mechanical engineering at Texas A&M University, came up with the idea in 2003, while working at NASA, of wrapping a lunar exploration robot in an inflatable sphere. So far, space exploration robots have not overcome the problem of tipping over on irregular terrain. A ball only rolls; it does not tip over. Cameras and instruments inside maintain orientation by rotating in sync with the ball's movement.
The inflated outer skin, like a ball, prevents instruments from being damaged by sharp rocks or dust. It also blocks extreme temperature swings. On the moon, temperatures swing more than 200 degrees Celsius in a day. When sunlight hits during the day, temperatures rise to 121 degrees Celsius, then drop to minus 133 degrees at night. The inside of craters that never receive sunlight is even colder.
NASA sees Shackleton crater at the lunar south pole as an optimal site to build a base for astronauts. Amrose's team said RoboBall is perfectly suited to explore the interior of this crater. Scientists believe large amounts of water are stored as ice inside Shackleton crater because sunlight never reaches it. Water can provide drinking supplies for astronauts, and its breakdown products oxygen and hydrogen can be used for breathing and as rocket propellant.
The Texas A&M team tested RoboBall III, 1.8 meters in diameter and weighing 150 kilograms, at a quarry in central Texas in Feb. RoboBall rolled unimpeded over rock, gravel and mud. Shackleton crater is 4 kilometers deep. Robots with wheels or legs have difficulty descending safely. RoboBall can bounce down like a ball.
It can also change direction. When a pendulum inside the ball moves left and right, RoboBall moves accordingly. On steep descents, moving the pendulum backward can slow the descent. Masahiro Ono, a professor who heads the Planetary Robotics Laboratory at Georgia Tech, said, "The best thing about RoboBall is its simplicity." He said robots move with actuators, and RoboBall has only two actuators, both housed inside the spherical shell, reducing the risk of damage from dust or rocks.
◇ Torque boosted 2.5 times and rockets added
The team said RoboBall could send lunar rock and soil samples back to Earth for the first time in half a century. Since Apollo 17 in Dec. 1972, NASA has not returned rock or soil samples from the moon. RoboBall's work to collect lunar samples and send them to Earth would proceed in stages.
First, an unmanned rover from the lander would travel to the crater rim and inflate RoboBall. It would then descend and deploy instruments at icy sites to collect samples. RoboBall can roll downhill but cannot climb back up on its own. The team devised a method to load the samples onto a rocket for launch. The rover would retrieve the rocket and load the samples onto a spacecraft bound for Earth.
Amrose joined Texas A&M University in 2021 and began full-scale RoboBall research. The following year, the team developed the 50-centimeter RoboBall II, proving the idea could be realized. It then took 11 months to build the full-scale RoboBall III. After the first quarry test, the team increased torque 2.5 times. Thanks to that, they said, it can hop over small obstacles and climb slopes of 20 degrees.
In a paper released in Nov. last year in an international journal, the team said battery-powered RoboBall III descended a quarry slope and traversed soft, sandlike terrain. A small rocket launched a mock payload up the slope. Building the RoboBall prototype cost $250,000.
Amrose said the team will make RoboBall's shell robust enough to roll over steel debris and withstand temperatures down to minus 184 degrees Celsius. At the same time, they plan to design it to adjust its driving mode automatically according to slope. Texas A&M University also said it plans to open the world's largest lunar and Martian terrain simulation facility in Houston at the end of this year.
More research is needed before RoboBall can explore lunar craters. Before that, it can prove its performance on Earth. Rishi Jangale (Rishi Jangale), the paper's first author and a doctoral researcher, said, "Imagine RoboBalls deployed in swarms after a hurricane," adding, "The ball robots can map flooded areas and find survivors."
References
IEEE Transactions on Field Robotics (2025), DOI: https://doi.org/10.1109/TFR.2025.3633215