This paper addresses the constraints concerning the allocation of equipment to volume within two of the pressurized, habitable modules of Space Station Freedom. This problem of topology optimization must address multiple competing constraints at various stages of the design evolution. Consistent and logical balance of conflicting location constraints is the objective in design optimization. This study defines the physical, functional, and operational constraints affecting the optimization of the Space Station Freedom Habitation and U.S. Laboratory module configurations, and discusses the evolution of their current baseline.