Study On The Effect Of Fabric Permeability On Aerodynamic Performance Of Supersonic Mars Parachute

Supersonic parachute plays a crucial role in the descent of Mars exploration missions.Whether the Mars parachute can function successfully will determine the success or failure of the mission.However,the disk-gap-band parachute used on all current Mars exploration missions is no longer sufficient for the future mission’s payload,meanwhile the new generations of supersonic disk-sail and ring-sail parachute had failed in their flight tests,which may be related to their complicated porosities(fabric permeability and geometric porosity).Fabric permeability is one of the most important characteristics of parachute.At present,most effects on fabric permeability are mostly considered for the cases in the subsonic flows,and the influence mechanism of fabric permeability under supersonic conditions is rarely reported.Therefore,it is necessary to carry out relevant research on the air permeability of parachute.Firstly,in order to investigate the influence of different fabric permeability on the aerodynamic performance of disk-gap-band parachute system under the low density of supersonic and subsonic flows,canopy models with different thickness and specific porosity(computed from its fabric permeability at a standard pressure differential)are designed for comparative study in this thesis.The results show that the canopies with the specific porosity of 16%～24% exhibit better stability when the thickness is 1mm.When the canopy has the specific porosity of12%,the canopies with the thickness of 0.2～0.5mm can effectively reduce the fluctuation within the parachute,which greatly improves the stability of parachute.Secondly,different air permeability schemes(including fabric permeability and geometric porosity)are designed for the supersonic disk-sail parachute system under the supersonic flow.The influence of different ratio of geometric porosity to fabric permeability on the flow field around the parachute under the premise of the same total porosity is compared and analyzed.As a result,when the ratio of geometric porosity to fabric permeability is 5:5,the fluctuation range of stand-off distance of canopy shock is small,and the stability of parachute has obvious advantages over other air permeability schemes.When the ratio of geometric porosity to fabric permeability is 7:3,the canopy has the best drag performance.With the contribution of fabric permeability increased from 30% to 70%,the drag performance of the disk-sail parachute presents a decreasing trend,but the decreasing amplitude is only about 6percent.Finally,the air permeability schemes with better aerodynamic performance are put into Mars exploration missions.The aerodynamic performance of supersonic disk-sail parachute system with different ratio of geometric porosity to fabric permeability in supersonic,transonic and subsonic flow environments is compared and analyzed.The results show that in the supersonic stage of the process of descent in the Mars exploration mission,the aerodynamic performance of the disk-sail parachute is better when the ratio of geometric porosity to fabric permeability is 7:3.In the transonic stage,the ratio of geometric porosity to fabric permeability of 7:3 has better drag performance,while the ratio of geometric porosity to fabric permeability of 5:5 has better stability.In the subsonic stage,both the drag performance and stability are at a higher level when the ratio of geometric porosity to fabric permeability is 5:5.