Research On The Asteroid Landing Mechanism And Its Penetrating And Anchoring

Asteroid landing exploration is a new field in deep space probing. It has greatscientific and economic value in learning the origin of the solar system andexploring the asteroid. Three key problems including the asteroid landingmechanism and it soft landing, anchoring theory of the landing mechanism on theasteroid surface, and simulated test of the landing mechanism on the ground aremainly studied in the thesis.Design Constraints of the asteroid landing mechanism are pointed out byanalyzing the characteristics of the asteroid, and then the mechanical structure of theasteroid landing mechanism is developed. Its structure mainly includes the landinggear and the anchoring system. The landing gear sonsists of landing foot, landingtruss, attitude element, buffer element, load element, and so on. The anchoringsystem consists of penetrating element, pushing element, rewinding element andcushion element, and so on. Soft landing of the equipment and anchoring of thelanding gear on the asteroid are realized by the landing gear and the anchoringsystem respectively.It is a precondition for exploring the asteroid that the landing mechanism safelylands on the asteroid, thus it is essential that the landing mechanism has excellentlanding performance. The main evaluation indexes of the landing performance areoverloading acceleration and stability period, and these two indexes can becalculated by landing dynamic. After analyzing characteristics of the landingmechanism and its landing strategy, a two dimension landing dynamic model is builtbased on Lagrange equation, which describes the dynamic characteristics of theasteroid landing mechanism in landing and turning stages. It can be found from thelanding dynamic model that the main factors affecting the landing performance arereverse thrust, buffer element damping and attitude element damping. In order togain excellent landing performance, the values of reverse thrust and buffer elementdamping are estimated, and then the attitude element damping is educed utilizing thelanding dynamic model. Whereafter landing performance of the asteroid landingmechanism is simulated using the parameters calculated above. Besides, the factorsaffecting the landing performance, such as attitude element damping, barbs underthe landing foot, landing slope and landing attitude, are simulated. Analysis of thesefactors can guide in initial landing condition choosing for the purpose of advancingthe landing performance.The landing mechanism is easy to flow away from the asteroid surface becauseit is of microgravity and the rotation speed of the asteroid is high, thus the landing mechanism will be fixed on the asteroid by the anchoring system after landing.Penetration equation of the anchoring system is built firstly in order to analyze therelationship between the penetration speed and anchoring force. This equationdescribes the mathematical relationship among penetration depth, penetration speed,anchor body mass, anchor tip shape and medium parameters in Mohr-Coulombmedium. Anchoring model of the anchoring system describing the mathematicalrelationship between penetration depth and medium parameters in Mohr-Coulombmedium is built secondly. Then the relationship between anchoring force andpenetration speed is established using the penetration depth as a link. Furthermore,conic tip is selected as anchor tip of the anchoring system and its geometrydimensions are designed based on penetration analysis, and factors affecting thepenetration depth are analyzed using penetration equation.Currently, ground simulated test which is necessary to verify the performanceof the landing mechanism is less developed. Thus microgravity landing andpenetrating/anchoring of the landing mechanism on the ground are developed in thepaper. Floating platform and penetrating/anchoring platform are designed, and theoverloading acceleration and stability period of the landing mechanism on thefloating platform with different velocity, attitude and landing slope are analyzed.Besides, penetrating and anchoring performances of the anchoring system in clay,sand, ice, snow, gypsum and concrete are tested on the penetrating/anchoringplatform, and the performance of the anchoring system is analyzed by thepenetration depth and anchoring force.