Sensorimotor Displays and Controls to Enhance the Safety of Human/Machine Cooperation During Lunar Landing

In the previous year, we have performed three separate experiments. At NASA JSC, the tilt-translation sled (TTS) was used to study the effect of our advanced countermeasure prototype display on manual control piloting performance. Performance was measured in a series of different motion paradigms designed to provide motion cues as might be experienced by a microgravity adapted astronaut flying a lunar lander vehicle. First a "critical tracking task" was studied in which the pilot attempted to keep an unstable vehicle upright. Next a "hover task" was studied in which the pilot attempted to keep the vehicle at a fixed horizontal position. Both of the tasks were done only in the pitch/fore-aft direction. A human subject experiment was performed in which manual control performance was consistently greater with the prototype display, with > 70% reduction in root-mean-square error. At the U.S. Army Aeromedical Research Laboratory, the UH-60 helicopter simulator was utilized to study the effect of lunar dust blowback on pilot perceptions of vehicle orientation during the final stages of landing. The dust characteristics in the visual database were modified to more closely resemble the attributes of lunar dust inferred from Apollo landing videos and the cockpit was modified to mimic the forward window fields-of-view from the Apollo Lunar Module. In the experiment subjects reported their perceived orientation (pitch and roll) and horizontal velocity (direction and magnitude) during simulated lunar landings. Different levels of dust blowback were simulated and compared to cases where the subject had no visual cues or when the subject was provided an instrument display. Subjects often misperceived their orientation during landings, particularly when dust blowback obscured visual out-the-window cues. Finally, we have begun an experimental study of the effect of gravity on human perception of orientation. In cooperation with the National AeroSpace Training and Research (NASTAR) Center, we are using centrifuge-induced hyper-gravity as an altered gravity test-bed. In the experiment, subjects report their perceived orientation during roll tilts presented at 1, 1.5, and 2 Earth Gs. The roll tilts are presented over a range of angles and rotation rates or frequencies. Subjects report their perceptions using a somatosensory indicator, which they attempt to align with their perceived horizontal while in the dark. This technique allows us to study spatial orientation perception during dynamic roll tilts. Preliminary results indicate that while the typical overestimation characteristic of static tilt perception in hyper-gravity (G-Excess illusion) is present during dynamic tilts, sensory integration reduces the magnitude of overestimation. This is important in understanding how the altered gravity levels experienced during space exploration missions may impact astronaut perceptions of vehicle orientation.