Design, Fabrication, and Testing of the Minotaur IV Large Fairing

Abstract

This paper describes the development and testing of a new fairing for the Minotaur IV launch vehicle that increases the nominal diameter by 20 percent to 110 inches. The Air Force Research Laboratory's Space Vehicles Directorate managed the development of this fairing for the purposes of demonstrating two out-of-autoclave large composite structure manufacturing processes. The larger portion of the fairing was fabricated using Alliant Techsystems' developed procedures for high quality composites using pre-preg cloth, extensive vacuum bagging, and oven curing. The smaller, but highly loaded, boattail portion of the fairing uses a WebCore sandwich core with a carbon fiber wrapped foam core. This portion of the fairing was produced using a Vacuum Assisted Resin Transfer Molding process followed by an oven cure. The fairing assembly is composed of four main sections with bolted composite-to-composite connections. The large fairing qualification test is the first of its kind conducted at AFRL since recent facility upgrades. The primary objective is to validate that the fairing can survive 125 percent of the predicted flight-induced loads. During the experiment force is concurrently applied at four discrete locations to create critical flight-like stresses and strains in the proper test article region without over testing non-critical areas. During the test synchronized force, strain, and displacement data will be acquired for comparison to pretest predictions. I. Introduction his paper describes the development and testing of a new fairing for the Minotaur IV launch vehicle. This is a relatively new launch vehicle assembled from Minuteman solid rockets and extra stages to allow delivery of moderately large spacecraft to orbital missions. The baseline fairing for this launch vehicle is 92 inches in diameter; the new fairing, planned by Space and Missile Systems Center and their contractor Orbital Sciences Corporation (OSC), is 110 inches, using a boattail configuration with a modest 1.2 aspect ratio, shown in Figure 1. The length of the fairing is approximately 21 feet. Air Force Research Laboratory's (AFRL) Space Vehicles Directorate, Kirtland AFB, NM has agreed to develop this fairing for the purposes of demonstrating, and potentially obtaining, flight heritage for two out-of-autoclave composite manufacturing processes. The larger portion of the fairing was fabricated using Alliant Techsystems (ATK) developed procedures for high quality composites using pre-preg cloth, extensive vacuum bagging, and oven curing. The much smaller, but highly loaded boattail portion of the fairing, uses a WebCore sandwich core with a carbon fiber wrapped foam core. This portion of the fairing was produced using a Vacuum Assisted Resin Transfer Molding (VARTM) process and oven curing. 1 The fairing was assembled from four sections with bolted composite to composite connections. The fairing will be qualification tested in the AFRL's laboratory at Kirtland AFB. The second half of this paper details the design and execution of a unique aerospace structural test.