Mathematical model and snatch force prediction for the lines-first parachute deployment

Prediction method for the lines-first parachute unfurling process was provided, in which the viscoelasticity of suspension lines was taken into consideration. The fundamental equation of the mathematical model of parachute unfurling process was formulated. The effect of viscosity term in fundamental equation on spreading of tensile wave along suspension lines was emphatically analyzed. The viscoelastic tensile wave not only causes delay of tension spreading from the canopy sleeve end to the other end, but also makes the tension at the two ends different due to absorption and dispersion during the parachute unfurling process. The present model was used to calculate unfurling loads and motions of a parachute deployment. The dynamic change of snatch force was analyzed and it shows that the max snatch force borne on the load end is related not only to max tension produced at the moment when the parachute skirt being drawn out, but also to the load tension produced after skirt is drawn out.