ACOUSTIC FILL EFFECT TEST AND ANALYSIS OF SPACE-CRAFT

摘要

Spacecraft is exposed to severer vibro-acoustic environments during rocket launches. To demonstrate the ability of spacecraft to endure acoustic levels imposed by launch vehicle and to validate unit random test levels, acoustic test is carried out during the design. The acoustic levels are usually representative of the unfilled environment in the fairing. In fact, fill effect occurs in the cavity, which is located in the clearance gap between the inner side of the faring and the payloads. This phenomenon results in an increase in sound pressure level (SPL). Acoustic fill effect for specifying an acoustic environment is vital importance. It then becomes necessary to account for the presence of the payload fill and its effects on the interior SPL. NASA-STD-7001A introduces a methodology for calculating the payload fill effect. Beijing Institute of Spacecraft Environment Engineering (BISEE) performed a test program to investigate the acoustic fill effect for an unblanketed payload fairing for variety of spacecraft. This paper discusses the test program and test results, introduces a new methodology for calculating the fill effect, and makes comparison with theoretical predictions. The result is also compared with NASA LeRC's acoustic fill effect theory. The analysis of the data obtained enabled BISEE to define an implementation methodology and incorporate it into the ISO standard.