Nonexplosive Approach to Fragment Subkilometer Asteroids with a Tether Centrifuge

Abstract

A THOUGH we have some clues about the mineralogy and surface properties of different families of asteroids and comets we still know very little about the structure and physical properties of their interior. Such information would be extremely precious to plan future missions to divert asteroids from their collision course with our planet or to shatter them in small dispersed fragments. Additionally, a better knowledge of asteroid internal composition, structure, and morphology can provide invaluable insight into the history and formation of our solar system and the development of life. So far, the approaches proposed in the literature toward improving our knowledge of asteroids structure and interior have been based on indirect measurements through radar tomography [1] and seismology [2] and on direct measurements through subsurface sampling [3]. Although the former can only provide limited resolution measurements of the interior the latter are restricted to the outer layers of the celestial object. This Note presents a new approach to study the internal structure and mechanical properties of small asteroids and comets by artificially increasing their spin rate up to a level where the stress induced by the centrifugal load triggers out a fragmentation process. It is shown that the spin-up process can be effectively carried out using a counter-rotating tether satellite anchored to the asteroid surface as a means to exchange energy and angular momentum with the celestial body. By monitoring the mechanical response of the asteroid to the increased centrifugal load scientific data about its strength and structure can be gathered. Most important though, once the fragmentation process is activated a direct access to the inner layers of the celestial body becomes possible providing unique scientific information for asteroid mitigation missions, planetary science, and astrobiology. In addition, once the complex fragmentation dynamics and asteroid mechanical properties are better understood, the concept could provide an alternativemeans for asteroid fragmentation aswell as an important tool in asteroidmining technology. It isworthmentioning that tethered satellite systems of up to 20 km in length have already been successfully deployed during low-cost space missions [4]. Besides, tethered sling systems attached to asteroids have been studied in the past as reusable propellantless transportation systems for planetary missions [5–7] or for recovering asteroid resources to be used as construction material for solar power satellites or space habitats [8]. Although such proposed tether applications differ considerably from the present one, these references have addressed the basic dynamic issues of asteroid-based tether slings. In particular, Puig-Suari et al. [5] discussed the need for a tapered-cross-section tether to minimize the required tether mass and derived a formula for the optimum taper profile, whereas Kuchnicki et al. [6] investigates the spin-up and deployment dynamics of the sling accounting for the inertial characteristics of the tapered tether.