Design and validation of a compact radius centrifuge artificial gravity test platform

Abstract

Intermittent exposure to artificial gravity on a short radius centrifuge (SRC) with exercise is a promising, comprehensive countermeasure to the cardiovascular and musculoskeletal deconditioning that occurs as a result of prolonged exposure to microgravity. To date, the study of artificial gravity has been done using bedrest and SRC's with subjects positioned radially with the head at the center of rotation. A recent proposal to put a human centrifuge on the International Space Station (ISS) highlighted the reality that near-term inflight SRC's will likely be confined to radii shorter than has been typically used in terrestrial analogs. The unique positioning required by such a constraint would result in physiological effects such as accelerations on the head, a change in blood pressure gradient across the body, and potential changes in muscle activation during exercise. In this project, we define a compact radius centrifuge (CRC) as a centrifuge with a radius of less than 1.95 meters, the height of the 9 9 th percentile male astronaut. Based on this definition, CRC's represent a class of centrifuges that cannot accommodate all subjects in a supine, radial position as is typically done in SRC's A CRC test platform is designed and fabricated on the MIT human centrifuge, which is constrained to a radius of 1.4 meters, the upper radial limit for a centrifuge to fit within an ISS module. The CRC includes a cycle ergometer for exercise during centrifugation, and also positions the subject sideways with the interaural axis parallel to the axis of rotation. Such positioning aligns the direction of the legs while exercising with the Coriolis forces, thereby eliminating lateral deflection at the knees and reducing the risk of a knee or hip injury. The CRC platform's design process is discussed, and the final design is described in detail. Finally, motor performance is characterized, and the CRC test platform and all associated systems are validated through a pilot run. The validated CRC will serve as a versatile platform on which future studies will be able to investigate physiological and mechanical responses to this unique, realistic centrifuge configuration.