Future long-term exploratory missions such as the piloted moon and Mars missions discussed in President Bush's July 20,1989 initiative expose crew members to reduced gravity environments. While the artificial gravitational environments created by rotation may reduce or eliminate the debilitating effects of microgravity on humans, they also present unique design challenges. This paper discusses the role of a Variable Gravity Research Facility (VGRF) as a test bed, the identification of critical crew systems issues, and the simulation of all phases of a piloted Mars mission in the relative safety of Earth orbit. Three candidate internal architectures and specific crew interface systems are presented and evaluated. Potential uses of the same or similar internal architectures for crew volumes on the surface of the moon and Mars are discussed. Crew systems variables such as overall internal architecture, systems and stowage allocations, workstation and restraint design, crew quarters, and commonality with Space Station Freedom are considered in conceptualizing and evaluating candidates for use in a VGRF. The additional constraint to operate over a range of acceleration levels from microgravity to more than one earth gravity is a driving factor. Potential vestibular disturbances in the crew and similar rotational problems in the systems further complicate a VGRF's internal architecture design.