NASA’s Ground Test Unit (GTU) Lunar Terrain Vehicle (LTV) Conceptual Hand Controllers Studies

Over that past year, the National Aeronautics and Space Administration (NASA) has been preparing and developing a set of standardized testing protocols for the commercial Lunar Terrain Vehicle (LTV) vendor selection. Two studies have been conducted on two possible hand controller concepts specifically designed for the operation of NASA’s Ground Test Unit (GTU) Lunar Terrain Vehicle (LTV) that can be applied to the heretofore unknown designs developed by future LTV vendors. The objective for the two studies were to determine which hand controller enable acceptable operation of the LTV in a simulated lunar traverse. In the first evaluation a total of nine subjects in shirtsleeves with ungloved hands performed two simulated lunar driving courses in an engineering simulator with each hand controller. Controller concept one was the T-handle fashioned after the Apollo Lunar Roving Vehicle’s (LRV) T-Handle controller. The rational for using this design is it’s a proven design while in a pressurized suit. However, the LTV does have a driving mode the LRV did not consider. The mode of crabbing or strafing the vehicle at different angles; thus, the idea of a dual T-Handle controllers to accommodate this function without using a switch or display was introduced. The second concept controller is a new innovative controller call the Tri-Rotor [NASA patent review MSC-27385-1]. Inspired by Formula One race steering, the Tri-Rotor was designed to take advantage of the restricted movement and dexterity of a pressurized space suit. During testing, all subjects were able to successfully navigate through two test courses of varying lengths and complexity. Results indicated the dual T-handle had minimal recommendations for improvement while the Tri-Rotor had more extensive ones. It must be noted, the Tri-Rotor is a first-generation prototype and has some known mechanical concerns; thus, recommendations from this study will be incorporated into the second generation.The second evaluation used two low fidelity physical GTU mockups with subjects wearing a Z-2 space suit with Portable Air Backpack (PAB) pressurized to 4.3 psia. Subjects also exercised the hand controllers feasibility for pressurized suited operations. The GTU mockups were static in nature. Feedback on usability, clearance, reach, and operability was captured. For the dual T-Handle controllers, results indicated that having to hold a continuous forward motion using the palm of a pressurized gloved hand would be fatiguing. Reach was considered reliable; however, the hand controllers mounted to the mockup did not have the same adjustability range when comparing right and left controllers. With the Tri-Rotor controller, it was observed when using the loop handles for driving operations, the loops induced a simultaneous wrist rotation which caused some flexing in the suit and over time could be fatiguing to the crewmember. This also may have introduced controller cross coupling. This type of cross-coupling was not seen in the earlier shirtsleeve testing. Lowering the hand controller’s height approximately 7.62 to 15.24 centimeters (3 to 6 inches) would aid in lessening the issue positioning the arms of the suit parallel to the ground taking full advantage of the suit’s wrist bearing reducing the awkward posture and decreasing cross coupling.