Composite isogrid structures for spacecraft components

The TRW Space & Technology Division along with its partners, Composites Optics, Inc. and the NASA Langley Research Center, conducted a joint research and development program to evaluate advanced composite isogrid structural design concepts to produce lightweight, cost-effective, and "minimum-part-count" composite spacecraft structural components. This study analytically and experimentally determined the structural and thermal performance benefits of composite isogrid structures for a range of spacecraft applications, including a solar array substrate panel, and equipment avionics, panel, and a high frequency RF reflector. The isogrid structures are fabricated from flat laminates using a composite Optics, Inc. isogrid composite manufacturing approach. The analytical results indicated that an isogrid panel can be constructed to meet both the bending stiffness and mass requirements for a range of spacecraft applications, but with a slightly greater panel height compared to the conventional designs. Thermal analysis, performed for a number of isogrid design configurations and compared with the thermal response of a standard honeycomb sandwich panel, indicated that the isogrid concept offers the prospect of lower operating temperatures relative to that experienced with honeycomb panels. for example, a solar array isogrid panel fabricated (open isogrid side facing the space environment) would operate 11 degrees F cooler than a traditional honeycomb panel. The lower operating temperature for the isogrid panel is a result of a higher effective radiant heat transfer. A comparative cost analysis between the isogrid and honeycomb sandwich constructions indicated that for flat panels the costs for fabricating isogrid structures can approach the costs in fabricating honeycomb sandwich structures. For doubly-curved surfaced, i.e., reflectors, isogrid structures are more cost-effective when compared to honeycomb sandwich structures.