Research On Improved Design For Landing Impact Buffer Seat System In Reentry Capsule Of Manned Spacecraft

The landing technology of reentry capsule of manned spacecraft is a key technology for manned space flight. The buffer seats in reentry capsule are essential to reduce the impact overload on the astronauts to ensure their safety. Buffer seats at present have strong compatibility to attenuate the chest-back impact acceleration,but weak to the head-pelvis one. The multi-directional impact loads imposed on the crewman maybe exceed the head-pelvis acceleration limit. To improve attenuation compatibility of the chest-back and the head-pelvis acceleration, this dissertation presents a systematic survey on the improved design schemes, attenuation capability, parameters optimization of buffer seats and the shock attenuation experiments of the cushion pole. The main research contents and results in this dissertation are summarized as follows.1) The landing conditions of reentry capsule and the attenuation compatibility of the present seat with the front gemel support are analyzed.A dynamic model of the present buffer seat is established based on the characteristics of the reentry capsule landing and work mechanism of the vertical cushion pole. The response and characteristics of the landing conditions, shapes of shock, various positions of buffer seats, and mechanics of the cushion pole are studied respectively. The analysis of the horizontal impact factors reveal hidden trouble due to short buffer distance and increscent head-pelvis acceleration. The promising measures are presented consequently according to the structural features of the present seat.2) The attenuation compatibility, the influence of the parameters and optimal design of the improved seats with the front elastic supports are studied.Four promising schemes are provided by supplementing elastic supports on the front end of the buffer seat, consisting of the horizontal support, the vertiacl support, the double support and the titled support. The dynamic models of the improved buffer seats are established. The influence of stiffness, damper and surport angle for all improvement schemes is studied. A multi-objective optimization algorithm is applied for obtaining parameters ranges of the design problems. One design scheme which applying a horizontal elastic support on the front end of the seat is choosed finally, because of its effective reduction of the head-pelvis impact load and small engineering constraints.3) The attenuation compatibility of seats with various horizontal buffers support on the front end is studied, and the optimum improved scheme is determined finally.The preferred design scheme that uses a horizontal nonlinear buffer support is analyzed in detail. This chapter is concerned with the comparison of three nonlinear support design schemes, including nonlinear spring and damper surpport, magneto-rheological fluid damper support, and expandable ring cushion pole support. The horizontal expandable ring cushion pole support is superior to the other two schemes because of its outstanding head-pelvis energy disppation capability, its short response time and convenient installation resulting from many references to the present buffer seat.4)The design methods of the expandable ring and the conic knot are proposed, and the experiments to measure the structural parameters and force are conducted.The design parameters of the expandable rings and the conic knot are proposed. The fomula to calculate the expanding force of the expandable rings are raised. The influence of the design parameters to the expanding force are discussed by numeric simulation. Two design parameters are obtained from the expanding ring material mechanical capability tests and the friction coefficient measure tests between expanding rings and a conic knot. The following successful static expanding ring tests show that the design fomula and the theory analysis are reliable.5) The engineering design and the multi-objective optimization of the expandable ring cushion pole are developed, and the shock attenuation experiments of the the cushion pole are conducted.Three segments design route of the expandable ring cushion pole is put forward, with normal and extreme landing speed considered. By the introduction of adjusting coefficients for the force and the stroke, the design extension is extended for the cushion pole that is made of same or various length rings. The preselecting engineering design and the comprehensive multi-objective optimum design are applied to the vertical cushion pole and the horizontal cushion pole. The high buffer capability of the expandable ring cushion pole and the validity of the engineering design are proved by the dynamic tests of the pole.