Advanced Iso-Grid Fairing Qualification TestFor Minotaur Launch Vehicle

摘要

The development of the grid-stiffened fairing to be flown on the Minotaur launchvehicle has made significant progress over the past five years. During November and December2002, this qualification structure was subjected to static qualification testing at the Air ForceResearch Laboratory (AFRL/VS) at Kirtland Air Force Base. The 6 m (20 ft) tall fairing wasconstructed of a carbon fiber composite grid structure that was over-wrapped to create alaminated skin. Upon completion of curing and machining, the fairing was cut in half to createthe classic “clam-shell” fairing. Metallic joints were bonded and fastened to the fairing at allinterfaces to complete the assembly process and simulate attachment of the base to a launchvehicle. Static qualification of the fairing tested the integrity of the fairing, thereby proving thedesign and manufacturing process. Loads were applied incrementally in a static loading scenario.The applied load envelope exceeded worst-case dynamic flight conditions with an added safetyfactor of 25%. At peak load the fairing must maintain structural integrity remaining within thedefined dynamic displacement envelope.Load application was accomplished through hydraulic actuators attached to the fairing by twomeans. Shear (lateral) loads were distributed over a large amount of surface area through the useof wide-body polyester straps. Additional loads were applied to the forward end or nose of thefairing. An aluminum “load head” was bolted in place of the nose cap, with actuators applyingload directly to the load head. The fairing and all actuators were bolted to a large steel frame thatprovided a rigid interface for load reaction. A multi-channel, servo-hydraulic load controller wasused to ensure all loads were within predetermined error bands. Additional safety measures weredesigned into the load control software to prevent overloading and uneven loading of the testarticle.Data was collected during the test from a variety of sensors. Traditional displacement transducerand strain gage data were recorded with a 256-channel data acquisition system. In addition, fullfield displacement was monitored at critically loaded fairing sections and downloaded by meansof digital photogrammetry. This system used three high-resolution cameras to record images atvarious intervals of load application. Post-processing the images gives the analysis team insightinto the relative skin and rib displacements in the tapered base of the fairing structure. This papersummarizes the test results, discuss the overall performance of the fairing under the test loads,correlate test response and analysis, as well as identify lessons learned.