Simulation Study of Human Input Devices in a Variable Gravity Environment for Commercial Space Transportation

Abstract

Commercial spaceflight is an exciting and rapidly growing segment of the space industry. Recent accomplishments by private companies taking non-professional astronauts into space have added additional momentum to the growth of the Commercial Space Transportation (CST) industry. It is expected that increasing numbers of private individuals will participate in commercial orbital and sub-orbital human spaceflight activities as Spaceflight Participants (SFPs). In several circumstances, the SFPs will be launched without the assistance and supervision of professional crew, requiring the SFPs to be able to manage their own safety and emergency procedures. To ensure SFPs’ safety, it is imperative to understand the unique effects of the spaceflight environment, particularly the effects of microgravity on the physio-cognitive capability of SFPs. The goal of this study is to develop general CST design guidelines for control input devices usable in variable gravity with or without a spacesuit. To accomplish this, we conducted an experiment to identify the best physio-cognitive control input logic and mechanisms for human operators in a variable gravity environment. The physiological effects of microgravity were produced by reclining participants in a Head-Down-Tilt (HDT) posture, using the Adaptive Spaceship Cockpit Simulator (ASCS). Participants were asked to perform a Fitt’s target selection task where the size and distance of a target were varied to produce different levels of target selection difficulty according to Fitt’s Law. We tested 27 participants in shirtsleeves in both the upright and HDT conditions using four input devices: (i) a touchpad, (ii) a touchscreen, (iii) a joystick, and (iv) a numpad. We investigated the accuracy of the target selection and response time across the four input devices in the two orientations. The experimental data indicated a significant difference in the target selection performance, and the touchscreen produced significantly more errors than the other devices. We conducted a regression analysis between the target width and the accuracy of target selection to determine the minimum target width required to ensure 95 percent selection accuracy for each type of input device. The approach used in this study allows for the inclusion of speed and accuracy in determining control input size and distance recommendations. This study paves the way for establishing an industry design guide in the growing CST domain.