A space crane concept: Preliminary design and static analysis

Future in-space construction and assembly facilities will require the use of space cranes capable of supporting and manipulating large and massive loads. The large size of the space components being considered for construction will require that these cranes have a reach on the order of 100 meters. A space crane constructed from an erectable four-longeron truss beam with 19 5-sq-m truss bays is considered. This concept was selected to be compatible with the Space Station truss. This truss is hinged at three locations along its bottom edge and attached at one end to a rotary joint cantilevered to the assembly depot's main truss structure. The crane's boom sections are rotated by extensible longeron actuators located along the top edge of the beam. To achieve maximum position maneuvering capability for the crane requires that the individual sections be capable of rotating 180 degrees about the hinge point. This can only be accomplished by offsetting the hinges from the longeron axes. Since offset hinges introduce bending moments in the truss members, an analysis of the effect of hinge offsets on the load-carrying capacity of the structure is required. The objective of the static finite element analysis described is to determine the effect of various offset lengths on the overall bending stiffness of the crane and on the maximum stresses.