Investigation On Parachute Impact Damage And Repairment Strategy Caused By Airflow Behavior Of Martian Dust Particles

The Mars exploration has become the most popular issue of deep space exploration missions in the past decade.Unlike other extraterrestrial planets such as the moon and asteroids,the Mars has a unique dusty atmospheric environment due to its dry and rarefied atmosphere.The high-speed aeolian activity may cause impact damage to the canopy of the Mars parachute.According to the results of high-altitude drop tests of ESA’s Exo Mars 2020 parachute,the parachute canopy with slight damage may further suffer much more serious tearing damage under the high-load working condition during the EDL process.Thus,the huge threat caused by the Mars dusty atmosphere to the Mars parachute cannot be ignored.In this paper,aiming at the characteristics of Martian dusty atmosphere as well as their threats to the Mars parachute,the contact mechanical model of Martian dust particles and the rarefied Martian aeolian two-phase flow are established to analyze the nonlinear mechanical behaviors of Martian dust particles and interactions between the gas-phase and the dust-phase of the Martian aeolian two-phase flow.Meanwhile,investigations on the key technology of parachute impact damage monitoring and structural self-repairing are carried out as well.Investigations on the contact mechanical model of Martian dust particles are carried out.According to the irregularly shaped characteristics of Martian dust particles,a contact state model of Martian dust particles is established based on the fractal theory and the Fourier analysis method.Based on the analyzing results of Martian dust simulant particles,particle templates of Martian dust with particle fractal dimensions of 2.2~2.6 are established,and fractal morphology parameters as well as Fourier contact parameters of all these particle templates are analyzed.The contact mechanical model of irregularly shaped Martian dust particles with aforementioned fractal morphology parameters and Fourier contact parameters are established based on the Discrete Element Method(DEM).In addition,the contact mechanical model is verified by carrying out the DEM simulation of particle loading test and experiments of particle loading test respectively,which reveals the law of contact mechanics of irregularly shaped Martian dust particles.Investigations on the behavior of Martian rarefied aeolian two-phase flow are carried out.According to the low-pressure atmospheric environment of the Mars as well as the tiny size of Martian dust particles,the rarefied characteristic of Martian aeolian two-phase flow is analyzed by calculating the Knudsen number of the interaction between the gas-phase and the dust-phase,while the Martian rarefied airflow is modeled based on the Boltzmann equation.Due to the difficulty in solving the integral term of the Boltzmann equation,the Martian rarefied airflow model is established based on the DSMC method and the discrete particle model respectively.In addition,characteristics of Martian rarefied airflow are analyzed by carrying out DSMC simulation and DEM simulation respectively.Based on this,the interaction between the gas-phase and the dust-phase of Martian rarefied aeolian two-phase flow is analyzed via DEM simulation,and effects of different parameters to the interphase interaction are investigated to reveal the law of Martian rarefied aeolian two-phase flow.Investigations on the key technology of parachute impact damage monitoring and structural self-repairing are carried out.Aiming at the flexible characteristic of Mars parachute fabric and the interaction between dust particles and the parachute fabric,the DEM model of Mars parachute fabric is established based on the springmass model and the discrete element method.The dust-parachute impact damage under the Martian dust storm environment is investigated by carrying out DEM simulation,and effects of different factors on the impact damage are analyzed to reveal the dominant factor and occurrence conditions of the impact damage.According to the load characteristics of the Mars exploration mission and the structural composition of the Mars parachute,a triboelectric nanogenerator(TENG)based self-powered sensing technology is proposed aiming at monitoring the impact damage of the Mars parachute fabric.The triboelectric dust-parachute collision sensor(TDPCS)is designed and optimized to improve the parachute impact damage monitoring technology.Meanwhile,the constitutive model of the Mars parachute shell is established,and the stress distribution model of the damaged parachute fabric is obtained.Based on the Shape Memory Effect,an SMA-based self-repairing mechanism(SBSRM)is designed to deal with the stress concentration around the damage hole.FEM simulation is carried out to analyze the working performance of the SBSRM,and the parachute structural self-repairing technology is improved as well.The aforementioned key technology of parachute impact damage monitoring and structural self-repairing are verified with experimental tests.The TDPCS is manufactured and the cyclic loading tests are carried out to verify the reliability of the TDPCS.The experimental test platform for the particle impact sensing is established.Experimental tests of TDPCS’s performance are carried out to verify the impact sensing function of the TDPCS.The experimental test platform for the particle-parachute impact monitoring is established based on the prototype of Mars parachute,and impact sensing tests are carried out to verify the proposed parachute impact damage monitoring technology.The SBSRM is manufactured and the experimental test platform for the self-repairing of damaged structure is established.Self-repairing tests are carried out to analyze the performance of the SBSRM,and the proposed parachute structural self-repairing technology is verified based on aforementioned tests.