279 Refined Gearbox Design for the Chariot Lunar Rover 

Steve Bauman* and David Lewicki* 

Abstract 

In planning for NASA’s return to the moon by the year 2020, the NASA John son Space Center (JSC)  designed and built a lunar concept vehicle called Char iot. Slightly larger than a pickup truck, it was  designed to demonstrate sim ilar utilitarian functions, but with twel ve wheels for redunda ncy, reliability,  and reduced surface contact pressure. JSC designed a motor gearbox to drive each of Chariot’s six  wheel pods. The pods can be independently steered over 360° for maneuverability. This paper describes the design of a second generation,  drop-in replacement gearbox. The new design has a lower parts  count, and is lighter than the original, which represents a step toward flight hardware.      Introduction 

The goal of this work is to demonstrate a gearbox fo r Chariot that would be cl oser to what NASA could  ultimately send to the moon. With fewer moving par ts, it would be smaller, lighter, and have improved  reliability. Helicopter gearb ox designs, one of our major research areas, shar e the concerns for reliability  and weight reduction that  space hardware demands. Therefor e, NASA Glenn Rese arch Center was  selected to help custom design the Chariot gearbox. As part of this effort, hi gh-performance, aerospace  quality gears were designed, specified and fabricated.    Design requirements for the new gearbox were devel oped to include, very importantly, that the new  gearbox make use of identical motors so that direct  comparisons could be made quantitatively. Like the  original, two gear reduction speeds would be provided, and each would supply nearly the same output gear reduction ratio as the original. The same mounting bolt pattern to the steering box top plate would be specified so that replacement of the original gearbo x would be straightforward, with minimal operational  downtime. Similarly, the electrical circuits would be compatible, and the exact same electrical wire connectors used.    Description of Chariot 

Chariot is slightly larger than a pickup truck and is designed for truck-type utilitarian purposes on the  moon (Fig. 1). This includes the ability to carry as tronauts and/or substantial loads of equipment or  regolith. It can be fitted with a soil-moving blade, and the flat top deck of the vehicle lends itself to custom-configurations for different missions.  Chariot has six identical and independently motor-dr iven wheel pods, three on each side of the vehicle  (Fig. 2). Each pod has a pair of driven wheels, so t he vehicle has a total of twelve wheels total. Having  numerous wheels and pods creates redundancy to as sure reliability, and reduces the ground surface  contact pressure. All six pods and wheel pairs can be  steered independently, and to any angle (a full 360degree capability) making the vehicle highly maneuverable.  For example, it can tr avel a straight path or  make turns while maintaining the vehicle body at any desired angle relative to the motion (often referred to as crab-motion control). Steering can also be optimized for special duties such as towing another  vehicle, or conducting rego lith excavating operations.  

                                                              * NASA Glenn Research Center, Cleveland, OH 

Proceedings of the 40th Aerospace Mechanisms Symposium, NASA Kennedy Space Center, May 12-14, 2010  NASA/CP-2010-216272