It is also hoped the inflatable design could be commanded to deflate at locations of interest, causing it to "sit down" and stop rolling. As the underside will be in greater contact with the ground, perhaps analysis tools can be lowered into the cavity beneath, sampling any gases vented from the ground. (Watch the video to see the inflatable Tumbleweed in action.)
Another prominent Tumbleweed design is a ridged "box kite" type. Although this technique is less mature than the inflatable design, the sail-like paddles have a better drag coefficient. This means they will use the available Mars winds more efficiently, perhaps traveling further and faster.
To aid control over the Tumbleweed, an offset weight housed in the center of the sphere could be commanded to alter position, shifting the Tumbleweed's center of mass and essentially steering it that way.
These concepts, along with others - namely the Dandelion, Eggbeater, and Tumble-cup configurations - have been tested and developed by a collaboration of research institutions including NASA Langley Research Center, North Carolina State University, Texas Tech University, the Biorobotics Laboratory at Case Western Reserve University and Planetary Science Institute.