Kinetic Impact Research On The Defense Of Hazardous Asteroid

There are many asteroids having close encounters with the Earth between whiles,once they hit the ground,an immense destruction would follow.In 2013,only a 15-m meteorite's airburst at height of 30 km injured more than 1500 people in Russia.It is necessary and urgent for human to be prepared for the outer threat.There are many hazardous asteroid mitigation means and techniques proposed,kinetic impact is one of the most mature means to deflect a hazardous asteroid.The Deep Impact mission had already impacted a comet as successfully as planned,NASA and ESA have a cooperation on a kinetic impactor demonstration mission AIDA,many related techniques will be tested and verified.Doing some further researches on kinetic impact,such as proposing a new impact strategy,discovering more impacting laws,searching more application scenarios by using kinetic impactors and so on,would be very helpful to the development of techniques of kinetic impact defence and would also provide more scientific goals of the asteroid exploration missions.Based on the deflection of a hazardous asteroid,further researches of impacts on an asteroid are carried out in this dissertation.Considering the unintended disruptions are very common in high velocity impacts,a much gentler multiple impacts strategy by us-ing several impactors equipped on an accompanying mothership is proposed.Then both single and multiple impacts are analyzed to learn about the orbit and rotation change of target asteroid.Moreover,an impact that could destroy the target asteroid is con-sidered,a very elongated fiction asteroid is chosen as target,numerical simulation is utilized to study the single fracture of the asteroid.The main innovations of this dissertation are summarized below:In case of unintended disruption of an asteroid after a high speed impact,and for the sake of a precise observation of the impact process,we proposed to make the target asteroid followed by a mothership which does some explorations before the impact and then sends the attached impactors to impact the planned locations,the impact could be gentle and controlled.The mothership can also observe the impact to make the best decision for the next impact.In the simulation of a multiple-impact scenario,the orbital change of the asteroid is studied.Comparing the impact results of single and multiple impact,a linear super-position could be used in a quick estimation of the times of multiple impact.The orbital changes of asteroids with different porous material are also compared,which quanti-tatively show the influences of pores on impacting results.Moreover,the statistical information of the orbit of target asteroid is considered in the simulation,the impact effects are analyzed through the change of the impact probability of the target asteroid.The rotational change of an asteroid is also studied during multiple impacts.The impact results'of different shapes of asteroids show multiple impacts could have great influences on the despinning of an elongated asteroid,which means the gentle multi-ple impacts may be used in a asteroid exploring mission,such as asteroid mining and redirect,to slow down the rotation speed of the target asteroid.The impact results of oblique impact show the normal impact is very efficient in changing both translation and rotation states of a nonporous elongated asteroid.The tumbling motion of an aster?oid after impact is studied,the tiny craters formed during impacts have influences on rotational states,especially on tumbling motions.An impact scenario in which the disruption of an asteroid is considered,and an extremely elongated asteroid is chosen as the target.For the first time,impact fracture of a free long rocky rod is studied.This impact scenario can also be used in a sample return mission when the impact position is close to the end and a small fragment would come out and be grabbed.The numerical simulation is used to calculate the impact results under different impact points and velocities.Then the scaling law of impact fracture is used to establish functional relations between the initial impact condition and impact results.And data fitting is used to obtain the functional relations,which could be used to predict the impact results,the relation may also be useful in the analysis of the evolution of the solar system.