Study of Crew Seat Impact Attenuation System for Indian Manned Space Mission 2024-26-0469

The descent phase of GAGANYAAN (Indian Manned Space Mission) culminates with a crew module impacting at a predetermined site in Indian waters. During water impact, huge amount of loads are experienced by the astronauts. This demands an impact attenuation system which can attenuate the impact loads and reduce the acceleration experienced by astronauts to safe levels. Current state of the art impact attenuation systems use honeycomb core, which is passive, expendable, can only be used once (at touchdown impact) during the entire mission and does not account off-nominal impact loads. Active and reusable attenuation systems for crew module is still an unexplored territory. Three configurations of impact attenuators were selected for this study for the current GAGANYAAN crew module configuration, namely, hydraulic damper, hydro-pneumatic damper and airbag systems. All the subsystems were mathematically modelled and initial sizes were estimated using Genetic Algorithm and SQP optimization techniques. Semi-active control for Hydraulic and Hydro-Pneumatic dampers was implemented and evaluated against its passive counterpart. We also establish an airbag impact attenuation system and evaluate its performance in two configurations, stuck and unstuck. Venting will not cease for the former configuration, whereas it is pressure controlled for the latter. For zero degree impact load case, Brinkley DRI (Direct Response Index), a NASA HSIR index on the risk of likelihood of spinal damage, is reduced by 36% for hydraulic damper and 22% for Hydro-Pneumatic damper using semi-active control and 15% for Airbag system. Hydraulic dampers were proven to be superior to Airbag and Hydro-Pneumatic systems within the spatial constraints imposed by the present crew module configuration.