Session
Session IV: The Past & Coming Years
Abstract
The THEMIS project requires the placement of five small spinning satellites, called Probes, into eccentric Earth orbits. The mission requires a lightweight bus with an optimized structure. The final structure design consists primarily of graphite composite panels, titanium and aluminum fittings and brackets, aluminum and nonmagnetic steel fasteners, and various thermal isolators. Extensive analysis and development testing was performed on the new composite elements of the structure. This bus design was challenging in every subsystem area. In particular, the Probe structure had to accommodate the complex and sometimes competing set of requirements. The fairing envelope constraint led to a tightly packaged bus with limited external protrusions. The Delta V requirement led to accommodating a complex propulsion system. The temperature extremes drove many aspects of the structure design. The final design meets all of the mission and detailed requirements, achieves a very high packing factor and has extremely low mass. Five identical Probe buses were fabricated. The schedule was demanding and did not allow for an engineering test unit structure. The first proto-flight structure was successfully designed, analyzed, fabricated, assembled and qualification-tested in a historical brief period of time.
Presentation Slides
An Optimized Small Satellite Bus and Structure for the THEMIS Mission
The THEMIS project requires the placement of five small spinning satellites, called Probes, into eccentric Earth orbits. The mission requires a lightweight bus with an optimized structure. The final structure design consists primarily of graphite composite panels, titanium and aluminum fittings and brackets, aluminum and nonmagnetic steel fasteners, and various thermal isolators. Extensive analysis and development testing was performed on the new composite elements of the structure. This bus design was challenging in every subsystem area. In particular, the Probe structure had to accommodate the complex and sometimes competing set of requirements. The fairing envelope constraint led to a tightly packaged bus with limited external protrusions. The Delta V requirement led to accommodating a complex propulsion system. The temperature extremes drove many aspects of the structure design. The final design meets all of the mission and detailed requirements, achieves a very high packing factor and has extremely low mass. Five identical Probe buses were fabricated. The schedule was demanding and did not allow for an engineering test unit structure. The first proto-flight structure was successfully designed, analyzed, fabricated, assembled and qualification-tested in a historical brief period of time.
