This is the NASA 20-G centrifuge, a large-scale version of the centrifuges you may have seen in biology class used to separate suspended material. In the NASA centrifuge, the human subject rides in a small compartment on the end of the arm and experiences the "fictitious" centrifugal force pushing outward at up to 20 times the force of gravity. To learn more about the NASA centrifuge, see 20G Centrifuge. For more on the centrifugal force, check out this Hyperphysics page.
