Abstract
NASA’s MobileLauncher 2 (ML2) is designed to support the launch of the largest of theupcoming Space Launch System (SLS) launch vehicles, enabling the Artemisprogram to transport astronauts and heavy cargo to the Moon and beyond. The ML2structure consists of a vertical trussed tower mounted on a crawler-transporterbase, allowing for transport of the tower and SLS Rocket between the VehicleAssembly Building and the launch pad. ML2 is composed of three primarystructural sections: the base of the tower, which integrates with NASA’scrawler-transporter and incorporates flame diversion, the lower chair portionof the tower, an asymmetric pyramidal space truss that supports the modules andtransitions to the base, and the upper module portion of the tower, consistingof seven stacked rectangular modules along with various umbilical attachmentsto the launch vehicle.
The tower’s primary structural elements—18-inch and24-inch diameter heavy-walled pipe sections—are joined using custom-designedcast steel nodes. These nodes are critical for transferring complexmulti-planar loads while accommodating the 3D truss geometry. Designed withboth welded and bolted attachment points, the cast nodes improve tolerances andsimplify field assembly as compared to a fabricated alternative. This paperprovides an in-depth analysis of the cast nodes used in the chair portion ofML2, highlighting their design variations and structural advantages. Itexplores how these components address ML2’s intricate geometric and structural challenges,offering insights into their role in optimizing strength, stiffness, weight,connection geometry, and construction efficiency.