The selection of rover size, whether the environment be on land, in the sea or air, or on the surface of another world, necessarily entails certain tradeoffs. These tradeoffs include vehicle mass, power source, speed, range, size of obstacles that can be dealt with, sensor compliment, and ultimately, mission objectives. Smaller sized vehicles have advantages in that they tend to be more nimble and can more closely explore a complex environment, but, in general, at a cost of reduced capability in all other areas. Larger vehicles enhance these capabilities, but at a cost of being somewhat ponderous, especially in complex environments. Hierarchical roving seeks to maximize the best of these extremes by carrying a hierarchy of smaller specialized rovers within a larger one. The larger rover acts as a carrier vehicle, communications relay, and power recharge source. The smaller specialized vehicles are deployed at a given site, execute their mission, are then recovered by the carrier vehicle, and finally transported to the next site. Greater situational awareness and the opportunity for self-rescue are additional benefits of hierarchical roving. Experience with a carrier vehicle containing three smaller vehicles is discussed, as are the design tradeoffs.
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