Abstract
During lunar landings, astronauts are generally in the standing position. However, there is a higher than acceptable risk of tibia fracture in the standing position. Tibia fractures during space missions can be mission ending or fatal due to the lack of intensive medical care while in space. While a seating position can pose less risk to the astronaut, the seat adds a large amount of mass to the lunar lander, and reduces visibility and mobility for the astronauts. This study explored the concept of a half-seat, where an astronaut can lean back on an angled seat for support allowing the seat to absorb some of the deceleration forces while still maintaining the benefits of a standing position. This study used a SimWise4D software simulation to model the human in a standing and half-seated position during a simulated lunar landing. This study determined the axial compression forces on the tibia and allowed calculation of the Revised Tibia Index (RTI), an injury metric used to determine if the half-seat can reduce the risk of injury compared to the standing position, and if these values are within the NASA injury thresholds. This study determined that the half-seat posture can reduce the risk of injury as determined by RTI values compared to the standing position, although the axial compression forces in the half-seat position are comparable to or greater than those calculated for the standing position. While the compression forces are higher in the half-seat position, they remain below NASA injury thresholds. The study results indicate that the half-seat can create a safer alternative to the standing position during lunar landings.