Up to 90% of astronauts experience spatial disorientation during reentry and landing of the shuttle, with prevalence proportional to the length of the mission. The possibility of extending shuttle missions is currently under investigation, and it is likely that the incidence and severity of spatial disorientation during reentry will increase with flight duration. This is a critical issue, as Orbiter landing data shows a decrement in performance following microgravity exposure compared to simulated landings in the Vertical Motion Simulator (VMS) at NASA Ames and the NASA Shuttle Training Aircraft. Despite the potential impact on landing operations, the basis of microgravity-related spatial disorientation is poorly understood. The aim of this proposal is to obtain basic data on the characteristics of head and eye movements during simulated Orbiter landings. The first stage involves measuring head-eye coordination during simulated shuttle approaches in a commercial flight motion simulator located at the Airbus Training Facility in Toulouse, France. The pilot lands the A340-600 with a steep glide slope of 12º (much steeper than the typical commercial approach of 3º) analogous to the steep 18-20º glide slope of the shuttle. Touchdown speed is equivalent to the Orbiter at around 200-220 knots, about twice as fast as a typical A340 landing. We have also begun testing in the VMS, which is used to train shuttle pilots. Our first subject, Ron Gerdes, is a former NASA test pilot, and performed successful shuttle landings in the simulator under various off-nominal conditions.

Phase II of this project involves the development of an ambulatory system for modeling microgravity-induced spatial disorientation, and its application in the simulator. We have developed a system based on Galvanic Vestibular Stimulation (GVS) which uses a small (<5mA) current to stimulate the vestibular (balance) system via surface electrodes placed behind each ear. The GVS system has been tested on 40 subjects (including 7 veteran astronauts), and has proven to replicate the postural, locomotor, gaze and perceptual deficits commonly observed after space flight. Moreover, results from astronaut subjects reveal that the effects of mission duration can be modeled by adjusting the magnitude of the GVS current.

Simulated landings in both the airbus simulator and VMS with pilots exposed to GVS demonstrated that pilot performance was degraded in a manner similar to that observed after actual shuttle landings. Pilots exposed to GVS induced roll oscillations of the aircraft during final approach and yaw oscillations during roll-out.

 

Supported by NASA grant NNJ04HF51G  (S. Moore PI, H. MacDougall Co-I).

Captain Xavier Lesceu of Airbus calibrating the eye movement system prior to simulated shuttle landings.

Schematic of final approach and landing of the shuttle.

The 20-g centrifuge at NASA Ames will be used to model spatial disorientation after spaceflight.

Pilot's view through the head-up display (HUD) during final approach at KSC. This landing was simulated in the VMS.

Ron Gerdes, a NASA test pilot, with video goggles prior to a simulated shuttle landing in the VMS.

Time-lapse photo of the VMS demonstrating its range of motion.

Schematic of the VMS, the largest flight simulator in the world, located at NASA Ames.

Simulated shuttle landing in the Airbus A340-600 motion simulator.

 

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