Comparison of Estimated and Measured LM Acoustically Induced Vibration

Abstract

The launch vibration levels induced during an acoustical test of the Lunar Module on several items are compared with estimates made by extrapolating statistically analyzed measured data. Procedures and data adapted from work by Mahaffey and Smith and by Barrett were used. Both methods were generally conservative. Estimates for a densely arranged 12 ton electronic equipment rack were particularly high. The use of component and support structure weights as attenuation factors is described to demonstrate the necessarily large reliance on engineering judgment in these procedures. The acoustical test, in which a representation of the entire Apollo system is excited through contiguous external ducts, is described briefly. An envelope of measurements of 282 accelerometer locations on the ascent stage considered as measuring equipment response is compared with 75 locations considered “primary” structure motion to demonstrate that specifying an envelope over the latter can be very conservative.