Failure Analysis of a Launch Vehicle Umbilical Shutter Mechanism During Vibration Qualification

Payload fairing (PLF) of a launch vehicle is exposed to harsh vibration environments due to jet noise during liftoff and in-flight aerodynamic noise. Accordingly, the systems mounted on the payload fairing are to be qualified for the vibration levels, predicted corresponding to the envelope of acoustic spectrums at critical instants of atmospheric flight. This paper presents a detailed study of a failure observed on the payload cooling umbilical system, mounted on the cylindrical portion of the PLF structure, during its design qualification vibration testing. The umbilical shutter inadvertently opened during the test. The vibration responses on the shutter, the dynamic behavior of the system, and the forces and moments on the mechanism are analyzed, and the physics of failure is understood. The design marginality is identified, and the shutter locking mechanism reconfigured to achieve the desired level of robustness in the system.