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Adapting the CMU Roving Robot as a Regolith Mover

Jim Nobles

Lunar Rover with earth-moving equipment

Conceptual Overview

LunaCorp and Carnegie Mellon University (CMU) are developing a robotic lunar rover designed to traverse some 650 miles of the lunar surface. This vehicle will return high-quality video of the journey to its operators for use in a variety of commercial recreational enterprises.

NOTE: The Lunar Rover concept and design belong to LunaCorp and CMU.

This article concerns the possibility of converting another vehicle of the same design into a lunar regolith handler (earth mover) for use in the Artemis Project for shielding and insulating the core module of Moonbase Artemis as well as other lunar regolith handling tasks. This possible adaptation is based upon the addition of a tool-carrying framework, referred to as the "scoop assembly," to the basic LunaCorp lunar rover configuration.

The scoop assembly is composed of three major components; two parallel support members that attach to the Rover frame underneath the vehicle and run fore and aft, a power systems module mounted on the support members that extend to the rear of the Rover and the tool mount fittings that are attached to the parallel members that extend in front of the Rover. Note that even though the scoop tool is illustrated, various other types of tooling may be accommodated.

Since the basic Lunar Rover has been optimized for a mission requiring no moving or hauling of any mass other than its own, there are several questions that need to be addressed concerning power production and sharing, weights and balances, and mechanical loads on the Rover frame and wheel assemblies.

The electrical power production module mounted at the rear of the assembly fits closely to the Rover's aft section so the entire Rover's center of gravity is affected as little as possible. Even so, some attention will almost certainly be required to the two rear wheels. The aft wheels are steerable and are how the the Rover changes its direction during travel. The two forward wheels on each side possess some pivotability on an axis perpendicular to the Rover's direction of travel but aren't steerable. The rear wheels may have to be "beefed up" or enlarged to compensate for the additional load of the scoop assembly power module. The actuators (motors) within the wheel axle housings will also probably need to be upgraded for the loads estimated for regolith handling. Each of the six wheels has its own actuator and each will almost certainly be upgraded to handle the additional load requirements.

The electrical power module would house a deployable solar cell array and battery unit for power collection and storage to augment the Rover's native power system.

Possible Tooling Applications

The scoop tool illustrated in these examples has been conceived as deep and narrow rather than shallow and wide. It was felt that weight distribution, simplicity of design, and the ability to extend the scoop into areas possibly obstructed by obstacles on either side were the most important factors. Note that there is no real provision to raise or lower the scoop other than by rotation on its cylindrical axis. To provide true raising and lowering capability would probably require redesign of the front section of the basic Rover chassis and the addition of extra weight for the mechanism.

Various types of tooling may be required depending on problems encountered once on the lunar surface. One of the more obvious (and often suggested) choices is simply a stiff wire rotary brush-type tool. If the regolith particulate size is small enough, such a rotary brush could be used to brush the material right up to the structures to be covered. It may even be possible to add a shroud to this tool, increase the RPMs to a high rate, and actually throw a stream of material up onto the structure. The shroud would direct the flow.

If a section of surface is found that exhibits the desirable particulate size, appears to have enough volume to make material extraction attractive, but appears a little too hard packed for a scoop or brush, then a tine (scratcher)-type tool may be useful. It could be used to break up the regolith for collection and transport by a different tool type. It is doubtful that a tine tool would be able to move material with as much efficiency as a scoop or perhaps a brush but it might be useful for the specific purpose outlined.

There is always, of course, the basic (bulldozer) blade tool. On terrestrial earth-moving machinery the basic blade is often used to transfer and shape soil. But these machines rely on their mass and weight as anchors to give them the leverage to break the soil loose. In the lunar environment a vehicle attempting to take a reasonable bite out of the regolith with a blade might spin its wheels rather than dislodge much material. A blade tool is simply a wide shallow scoop. Attempting to transport material with a blade would mean pushing it the entire distance rather than carrying it. Nevertheless a blade might be useful in some circumstances and is considered.

Issues and Observations

All of the examples cited above are based upon the basic off-the-shelf LunaCorp/CMU Lunar Rover being configured as illustrated. If this configuration does not represent the final form of the vehicle, then conceptual designs based on it are invalid. Since the LunaCorp Rover is optimized for a non-material-handling mission, its adaptation to that role may prove to be too much, in terms of loss of efficiency, to enable it as a viable option. A regolith-handling vehicle may need to be developed that is not based on a simple adaptation of the CMU Rover. Major systems, however, might still be used in their almost entirely original form. The telerobotics and communication systems, for example, might very well be directly adaptable for both roles.

There have been suggestions and proposals for a "snow blower"-type device for throwing regolith on top of moonbase structures for insulation and shielding. Such a device was not addressed here because it's considered an important piece of equipment in its own right and not likely to be a simple tool add-on to a Rover. Indeed, such a device might be stationary, especially if it has sufficient power to project the regolith stream as required onto the module, and regolith may be brought to it by a roving robot.

Copyright; Jim Nobles 17 Dec 1995.

Lunar Rover Initiative Vehicle

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