Structural design of the MSX spacecraft

The Midcourse Space Experiment (MSX) spacecraft represents the largest structure ever assembled at the Applied Physics Laboratory. The design of the structure involves the application of conventional aluminum framework/honeycomb panel construction with composite materials technology to satisfy both the launch vehicle induced loads and the dimensional stability requirements of the optical sensors and instruments. The 1.59-m(2) by 4.11-m-long structure is divided into three discrete elements consisting of (1) an electronics section, which provides an interface to the Delta II launch vehicle and a mounting platform for instrument and spacecraft electronics; (2) a thermally stable graphite/epoxy composite truss structure for mounting the Spatial Infrared Imaging Telescope III (SPIRIT III) instrument and providing an interface between the instrument and electronics sections; and (3) a temperature-controlled instrument section with embedded heat pipes for mounting delicate sensors and instruments. The instrument section also provides a thermally stable mounting structure for the optical bench and the beacon receiver bench. This article describes the features of the MSX structural design, the structural analysis, and testing efforts associated with qualifying the design. A description of the efforts involved in the development of the graphite/epoxy composite optical bench and beacon receiver bench is also presented.