Progress of Planetary Defense Research in China

Near-Earth Asteroids(NEA)impose potential major disaster to humanity.Planetary defense is an inevitable requirement for the survival of human civilization.In recent years,China has made rapid progress in planetary defense research,which has won the attention of the government and attracted more and more scholars and organizations.This paper summarizes the research progress in planetary defense in China in recent years,including the fireball events in China,academic activities and policy planning,monitoring and warning technology,onorbit defense technology,impact hazard assessment,international cooperation and science popularization.

Planetary defense mission concepts for disrupting/pulverizing hazardous asteroids with short warning time

This paper presents an overview of space mission concepts for disrupting or pulverizing hazardous asteroids, especially with warning time shorter than approximately 10 years. An innovative mission concept, referred to as a nuclear hypervelocity asteroid intercept vehicle (HAIV) system, employs both a kinetic-energy impactor and nuclear explosive devices. A new mission concept of exploiting a multiple kinetic-energy impactor vehicle (MKIV) system that doesn’t employ nuclear explosives is proposed in this paper, especially for asteroids smaller than approximately 150 m in diameter. The multiple shock wave interaction effect on disrupting or pulverizing a small asteroid is discussed using hydrodynamic simulation results. A multi-target terminal guidance problem and a planetary defense mission design employing a heavy-lift launch vehicle are also brie y discussed in support of the new non-nuclear MKIV mission concept. The nuclear HAIV and non-nuclear MKIV systems complement to each other to effectively mitigate the various asteroid impact threats with short warning time.

When It Strikes,Are We Ready?Lessons Identified at the 7th Planetary Defense Conference in Preparing for a Near-Earth Object Impact Scenario

Near-Earth object(NEO)impact is one of the examples of high impact and low probability(HILP)event,same as the Covid-19 pandemic the world faces since the beginning of 2020.The 7 th Planetary Defense Conference held by the International Academy of Astronautics(IAA)in April 2021 included an exercise on a hypothetical NEO impact event,allowing the planetary defense community to discuss potential responses.Over the span of the 4-day conference this exercise connected disaster response and management professionals to participate in a series of panels,providing feedback and perspective on the unfolding crisis scenario.The hypothetical but realistic asteroid threat scenario illustrated how such a short-warning threat might evolve.The scenario utilized during the conference indicates a need to prepare now for what might come in the future,because even with advance notice,preparation time might be minimal.This scenario chose Europe for the impact,which may likely cope with such a disaster,through the Union Civil Protection Mechanism(UCPM)and other solidarity and support mechanisms within the European Union(EU),as well as with potential support from international partners.This short article raises concern about other areas in the world on how they may access NEO impact information and cope with such disasters.It also provides an idea on vast scale of such disaster vis-a-vis the current capacity of response systems to cope with a larger event in Europe or elsewhere.This scenario showed that planetary defense is a global endeavor.Constant engagement of the planetary defense and disaster response communities is essential in order to keep the world safe from potential disasters caused by NEO impacts.

Capacity of Sun-driven lunar swingby sequences and their application in asteroid retrieval

For deep-space mission design,the gravity of the Sun and the Moon can be first considered and utilized.Their gravity can provide the energy change for launching spacecraft and retrieving spacecraft as well as asteroids.Regarding an asteroid retrieval mission,it can lead to the mitigation of asteroid hazards and an easy exploration and exploitation of the asteroid.This paper discusses the application of the Sun-driven lunar swingby sequence for asteroid missions.Characterizing the capacity of this technique is not only interesting in terms of the dynamic insights but also non-trivial for trajectory design.The capacity of a Sun-driven lunar swingby sequence is elucidated in this paper with the help of the“Swingby-Jacobi”graph.The capacity can be represented by a range of the Jacobi integral that encloses around 660 asteroids currently cataloged.To facilitate trajectory design,a database of Sun-perturbed Moon-to-Moon transfers,including multi-revolution cases,is generated and employed.Massive trajectory options for spacecraft launch and asteroid capture can then be explored and optimized.Finally,a number of asteroid flyby,rendezvous,sample-return,and retrieval mission options enabled by the proposed technique are obtained.