INVESTIGATION OF THE EFFECTS OF VIBRATION ON DIAL READING PERFORMANCE WITH A NASA PROTOTYPE APOLLO HELMET.

Dial reading performance while wearing a NASA prototype Apollo helmet was investigated during short duration whole-body sinusoidal vibration. The subjects were in the semisupine position so that the force of gravity acted through the X-axis of the body, with the vibration acting in the X-axis in one experiment and in the Y-axis in another. In each study, dial reading was assessed subject and dial vibrating at 6, 11, and 15 Hz when the helmet was worn either with or without a helmet liner. The vibration intensity was plus or minus 1.2 G in the X-axis experiment and plus or minus 0.9 G in the Y-axis experiment. Static control measurements were also made both with and without the helmet. The results showed significant decrements in dial reading performance during vibration which were differentially related to direction of vibration, frequency of vibration, and to combinations of liner versus no liner with the three frequencies. The results further indicated that the effects of different directions and frequencies of vibration while wearing the Apollo helmet were quite similar to those found in previous studies under the same conditions using a Mercury helmet without a face plate. However, the data suggested that performance was somewhat poorer during both vibration and static conditions while wearing the prototype Apollo helmet. This is probably the result of visual interference produced by the curvature of the helmet face plate and by small scratches and blemishes on the face plate of the particular helmet used in this study.