An airbag-based crew impact attenuation system for the Orion Crew Exploration Vehicle

Abstract

It is a well known fact that every capsule-shaped reentry vehicle developed by NASA was initially conceived to land on land, but was ultimately designed to land in water. In all cases, the primary factor contributing to this fundamental shift was related to difficulties with keeping the vehicle to within its mass allocation. In recognizing the recurrence of this scenario during the development of the Orion Crew Exploration Vehicle (CEV), the concept of airbag-based crew impact attenuation was identified as being a potential means for providing a low mass, reconfigurable alternative to the currently baselined pallet-strut design. This thesis presents the development effort undertaken to determine the feasibility of this concept in terms of protecting an astronaut from the impact loads incurred during the nominal 7.62m/s Orion CEV landing on land. Through the complete development and testing of an analog airbag system and an intermediate technology demonstrator, practical means for system implementation have been developed, and insights into the influence of the system configuration on its overall impact attenuation performance obtained. These findings have culminated in the design and implementation of a full-scale multi airbag system, which has been experimentally shown to be capable of maintaining the risk of injury to the occupant during a 7.85m/s, 0' impact angle land-landing to within the NASA specified limit of 0.5%. In accomplishing this, the airbag-based impact attenuation concept has been proven to be feasible. Moreover, the obtained test results suggest that by implementing anti-bottoming airbags to prevent direct contact between the system and the landing surface, the system performance during landings with 0' impact angles can be further improved, by at least a factor of two. Additionally, a series of drop tests from the nominal Orion impact angle of 30' indicated that severe injury risk levels would be sustained beyond impact velocities of 5m/s. This is due to the differential stroking of the airbags within the system causing a shearing effect between the occupant seat structure and the spacecraft floor, removing significant stroke from the airbags. These results combined indicate that with further detailed design in the context of the currently fixed Orion crew cabin design, and the enforcement of a flat impact angle during landing, airbag-based impact attenuation may prove to be the key to finally achieving the elusive goal of capsule-shaped vehicle reentry and land-landing.