M. F. Reschke | Engineering Papers

NASA NTRSDate not supplied

DEVELOPING AN EARTH-FIXED VISUAL REFERENCE TO AID STABILITY, READAPTATION, AND EGRESS AFTER A WATER LANDING

Water landings present the worst possible sensory conditions for crews trying to orient and stabilize themselves immediately after long-duration spaceflight. Of the three sensory feedback systems involved in maintaining stability (i.e., proprioceptive, vestibular, and visual), none will provide reliable orientation information under the current water landing scenarios. Although the visual system is likely not affected by the disuse and adaptation to microgravity that affect the proprioceptive and vestibular systems, the visual environment within an enclosed space that is subject to wave-induced rocking will prevent the crewmember from using vision to determine which direction is up. This is true whether enclosed in the capsule or in a room on the recovery ship. The result is an increased risk of fall-related injury. In a prior study, 70% (21 of 30) of nonimpaired subjects reported that the presence of an Earth-fixed horizontal line helped them stabilize when their visually enclosed environment was exposed to wave motion. In addition to aiding stability, an Earth-fixed visual reference also can assist in the readaptation process. Sensory re-adaptation occurs when the three sensory systems are synchronized with one another and aligned with Earth’s gravity. The earlier an Earth-fixed visual reference can be introduced the sooner the readaptation process can begin. The goal of this project is to identify the optimal features of a device that visually presents gravitational reference cues to support egress, stability and readaptation. **Remainder of abstract in document preview or downloadable version

B. T. Peters↗

NASA NTRSDate not supplied

Functional Task Tests in Partial Gravity During Parabolic Flight

BACKGROUND Critical mission tasks required by crews immediately after landing on a planetary surface include walking, jumping, and egressing from a seat. Understanding how these functional tasks are performed in partial gravity such as on the moon or Mars is necessary to define effective and comprehensive countermeasure strategies for preserving crew performance during exploration-class missions. We propose to study the performance of these tasks during the partial gravity phases of parabolic flight. These tasks will be performed using the same equipment and procedures as those used with astronauts returning from spaceflight and with ground-based subjects after prolonged axial body unloading during bed rest (sensorimotor standard measures). HYPOTHESIS We hypothesize that partial gravity during parabolic flight will cause acute changes in vestibular, proprioceptive, and sensorimotor functions, and these changes will impact the performance of mission critical tasks such as standing, walking, and jumping. The largest changes in performance are expected at the lowest gravity level (0.25g) because subjects will no longer be able to use the gravitational reference for the perception of upright. Ultimately, this information could be used to assess performance risks and inform the design of countermeasures for NASA exploration-class human missions. METHODS Twelve subjects will be tested during three flights of 30 parabolas, including 10 parabolas at 0.25g, 10 parabolas at 0.5g, and 10 parabolas at 0.75g. Subjects also will perform tests in 1g between parabolas. The tasks will be the same as those tested on astronauts returning from spaceflight: sit-to-stand with obstacle walk, tandem rail balance, jump down, and recovery from fall. Measurements will include: (a) time to test completion (sit-to-stand with obstacle walk, recovery from fall); (b) time elapsed between the start of motion and the stabilization of upright posture (recovery from fall, jump down); (c) mean sway speed during quiet standing (recovery from fall, jump down); (d) changes in heart rate and blood pressure (recovery from fall); (e) balance time and torso accelerations (tandem rail balance); (f) cone of stability (jump down); and (g) severity of motion sickness symptoms. RELEVANCE Although gravitational dose-response curves have been obtained for some biochemical systems in animals, these dose-responses are unknown for most human physiologic systems. Our study will compare the outcomes of four functional task tests in 0.25g, 0.5g, 0.75g, and 1g with those previously obtained in ground-based subjects after prolonged axial body unloading and in astronauts immediately after spaceflight. These comparisons will help us understand the true extent of functional task performance deficits in partial gravity. The dose-response relationship between gravity level and task performance decrement also will help determining the gravity threshold for these functional tasks. ACKNOWLEDGEMENT This work is supported by the NASA’s Human Research Program Human Health Countermeasures Element.

T. R. Macaulay↗