Galvanic vestibular stimulation as an analogue of spatial disorientation after spaceflight.

BACKGROUND Exposure to microgravity adversely affects performance of astronaut pilots; a review of the first 100 Shuttle missions found that touchdown speed was above specified limits in 20% of landings, in contrast to near ideal performance in preflight high-fidelity Shuttle simulations. Ground-based simulators emphasize spacecraft handling abilities, but do not recreate the effects of extended weightlessness on sensorimotor function. The aim of this study was to validate an analogue of the sensorimotor effects of microgravity using pseudorandom bilateral bipolar galvanic vestibular stimulation (GVS) during Shuttle landing simulations. METHODS Pilot performance was assessed during simulated Shuttle landings in the Vertical Motion Simulator at NASA Ames Research Center, Moffett Field, CA (used for astronaut pilot training). Subjects (N = 11) flew eight pairs of identical landing profiles (final approach and touchdown), with and without GVS, presented in a pseudorandom order. RESULTS Touchdown speed was on target (204 kn) without GVS [203.8 kn], but increased significantly during GVS exposure 1208.5 kn] and was at the upper limit (209 kn) of the target range. The adverse effects of GVS on pilot performance were obvious. Unsuccessful (crash) landings increased from 2.3% (2/88) without GVS to 9% (7/88) with GVS. Hard landings, with touchdown speed in the 'red' (unacceptable) range (> 214 kn), almost doubled from 14 (15.9%) without GVS to 27 (30.7%) with GVS. CONCLUSION GVS was an effective analogue of decrements in postflight Shuttle pilot performance.