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Modularity is taking off in more ways than one in space exploration. The design of the upcoming "Lunar Gateway" space station is supposed to be modular, with different modules being supplied by different organizations. In an effort to extend that thinking down to rovers on the ground, researchers at Germany's space agency (DLR), developed an architecture where a single, modular rover could be responsible for both exploration and carrying payloads around the moon or Mars. The study is in Acta Astronautica.

The architecture itself is simple enough—use a rover to pull around specialized "payloads," all of which use a standardized mechanical connection that allows electricity and fluids to flow between the rover and the payload. That connection also allows the rover to pull the payload to where it is needed and connect it to other infrastructure in the area. The payloads could vary depending on the need. They could be a power supply, a suite of scientific instruments, or even construction attachments like a shovel or backhoe.

A typical use case for this type of infrastructure is exemplified by water extraction on the moon. The rovers, which are derived from the TransRoPorter (TRP) concept originally developed at DLR, would be responsible for scouting where potential water ice might exist. They could then bring the necessary equipment, in the form of payloads, to any ice they discover. They could also then be used to move the water ice from the mining site to locations where it could be better utilized, such as rocket fuel factories of astronaut habitats.

This is all much easier with standardized connectors and communications and controls interfaces. However, perhaps the most important part of this architecture are the rovers themselves, so the researcher decided to simulate several different configurations of how the rovers might move and interact with payloads.

All of the rovers were a "hybrid" locomotion system where the rover's wheels are placed on the end of long articulated legs. This configuration has some advantages over alternative hybrid systems, such as that used on Curiosity—perhaps most importantly for the context of this architecture, the TRP configuration is faster.

In the simulation, there were plenty of other variables to play with though. One of the most important was whether the wheels were controlled where one entire side moved together (serial) or whether a wheel on each side was controlled with another one (parallel). Other variables included the configuration of the legs themselves, whether or not there was a payload, and the type of slope and surface the rover was required to move across.

Over 1,500 simulations, some critical design choices began to stand out. There was no clear "winner," as the choices represented trade-offs. Metrics like hip torque and ground clearance were the measurements that were most affected by the rover's configuration, with some causing unacceptable outcomes in either of those values. The stability of the system seemed relatively consistent no matter the design choices, and the power consumption seemed to vary the most with the presence (or absence) of a payload, no matter how the rover itself was configured.

The paper represents another step forward in the long-standing development of the DLR's legged rovers for space exploration. As rovers start to be relied on for more than just exploration, and become a key aspect of infrastructural work for new off-world colonies, understanding the best configuration for a given implementation will be critical. And the ability to switch between different configurations depending on the needed context might be even more so. While there aren't any current plans to launch these rovers off world, they've officially taken another step towards being ready when they're finally called on to do so.