EASE/ACCESS - Experiment and EVAs

Experiment and EVAs

Astronauts Jerry L. Ross and Sherwood C. Spring repeatedly assembled a 3.7-metre (12 ft) tetrahedral truss (EASE) and a triangular column truss (ACCESS) during two extra-vehicular activities (EVAs). The first EVA was devoted to studying human performance in assembly techniques, while the second was dedicated to supplementary experiments, including alternative construction techniques and maintenance scenarios.

The EASE structure consisted of six identical aluminum beams, each 12 feet (3.7 m) long and with a mass of 64 pounds (29 kg), connected by four nodal joints. ACCESS consisted of 93 tubular aluminum struts, each 1-inch (25 mm) in diameter—thirty-three 4.5 feet (1.4 m) struts, and sixty 6 feet (1.8 m) struts—connected by thirty-three nodal joints. While assembling the EASE structure, the astronauts moved about the structure under their own power. For the assembly of the ACCESS structure, the astronauts were secured to a mobile platform on the Remote Manipulator System, which was guided by astronaut Mary L. Cleave.

A stereoscopic camera system recorded the movements of the structural beams during assembly. Taking into account the effects of inertia, drag, and virtual mass, researchers used this data to reconstruct the applied moments of inertia. The structure was also assembled in neutral buoyancy simulation, and the two environments were compared. The EVAs were also recorded by an IMAX camera mounted in the shuttle cargo bay.