▲ Carde rover prototype under test. Source: NASA
The National Aeronautics and Space Administration (NASA) plans to send several small landers to the lunar surface to explore the moon ahead of the lunar re-landing and manned exploration. Among them, the Commercial Lunar Payload Service (CLPS) lander, which will be launched in 2024, will carry three small shoebox-sized rovers.
The Cooperative Autonomous Distributed Robotic Exploration (CADRE) system explores the moon in a completely different way from NASA’s previous exploration rovers.
NASA’s Mars rovers, such as Perseverance and Curiosity, are loaded with all experimental and exploration equipment in a compact vehicle-sized rover weighing 800 kg. As such, if the rover breaks down or suffers an accident, the entire system may become unusable and the mission may fail. Therefore, NASA scientists are only moving the rover a little bit per day along safe routes.
Although it is an unavoidable choice, it is a very inefficient structure for exploring large areas, creating topographical maps, or working. In particular, in the case of external planets like Mars, communication with Earth takes a considerable amount of time, greatly reducing efficiency.
The core of CARDE lies in decentralization and autonomy. Each robot uses a stereo camera and ground-penetrating radar to explore the terrain and investigate below the surface. Instead of manipulating them directly, they simply give instructions to explore the area. The robots then cooperate with each other to autonomously survey the area.
▲ The CARDE rover compared to the Mars rover. Source: NASA
The primary goal is to self-survey an area of 400 square meters and create a three-dimensional topographical map, which can complete the work much faster than manipulating it directly. Even if one robot breaks down during the exploration process and cannot work, the work speed will only slow down and it will not change that it autonomously performs the same mission.
To perform missions on its own without human guidance, the CARDE rover needs a more powerful CPU than the BAE Systems RAD750 mounted on Perseverance or Curiosity. BAE Systems’ RAD750 has safety that guarantees operation for decades even in a radiation environment, but its performance is only comparable to that of a 1997 PC, making it difficult to perform autonomous missions.
Therefore, the CARDE rover uses a smartphone processor like Injeonuity, a helicopter on Mars. Instead of having a short lifespan and poor safety in a high-radiation environment, the latest technology can be integrated to improve performance.
However, unlike the cold Mars, the moon is very hot during the day, so it is difficult to handle the heat if the processor and motor continue to operate. Therefore, CARDE rovers take a 30-minute break, then recharge their batteries with solar cells and resume their mission. Still, the overall mission time is much faster than that of conventional rovers.
But, in fact, there is another reason to get the job done quickly. Because the small rover cannot be equipped with a thermal insulation system to protect its electronic systems from the lunar cold, the rover’s maximum mission duration is only about 14 days of daylight.
The lunar night and day last about 14 days, and the temperature exceeds 100 degrees Celsius during the day, but plummets below minus 100 degrees Celsius at night, so the device will be damaged unless there is a separate heating system. Therefore, CARDE must accomplish its mission within it. It’s short, but since it’s for the purpose of testing autonomous collaborative robots, it should be enough to collect the information needed for verification.
In 2024, NASA plans to test the CARDE rover, which autonomously achieves its goals by sharing missions with each other in the Raynor Gamma region in the Lunar Ocean of Storms. If they do satisfactorily, we could see a larger and more diverse set of autonomous collaborative robots in space exploration in the future.
Gordon Jung Science Columnist [email protected]
