This report displays the mass evolution of representative Spacelab configurations, both combined and broken down in to functional subsystems, such as module structure (pressurized), pallet structure (unpressurized), environmental control (atmosphere and thermal control), avionics (data/power handling and distribution) and Orbiter/Spacelab interface hardware (retention beams and transfer tunnel).

The underlying mass data analysis aims at identifications, separation, and distinct display of mass variations resulting from changes in mission requirements. For example; environment predictions, payload provisions, orbiter interface evolution (supplies, utilities, controls), safety provisions, as well as from design process changes (in sufficiency of mass estimations, make work actions).

Since the Spacelab program has advanced to a point where system and subsystem designs are essentially frozen, a projected mass for the date of Spacelab completion is defined including suggested extrapolation to cover upcoming changes as will result from Spacelab integration and test phases.