The feasibility of deflecting asteroid 2017 PDC using neutral beam propulsion

摘要

The neutral beam for asteroid control (NBAC) technology is a globally neutral plasma thruster that seeks to fill the operational gap between high impulse and slow push asteroid deflection methods. Additionally, NBAC can be used to modify both the spin state and trajectory of an asteroid. In this work, we study NBAC's ability to de-spin and/or deflect an asteroid, considering a range of asteroid sizes, asteroid spectral types and assuming the asteroid's orbit is that of the hypothetical asteroid 2017 PDC. The analysis assumes that four NBAC-equipped spacecraft are deployed, each with a 10 keV neutral beam emitter. The achieved deflection and the applicability of NBAC to a deflection campaign is presented. This work quantifies the impact of uncertainty in asteroid composition on propellant and deflection time requirements for NBAC. Assuming one perihelion passage prior to Earth-impact, NBAC can successfully deflect a 100-150 m S, C, B, or Xc-type asteroid on the 2017 PDC trajectory. Loss of a spacecraft during deflection and its effect on mission success is also investigated. Failure of one or two (of the four) NBAC-carrying spacecraft during deflection does not preclude successful deflection for a set of sizes and densities. Propellant usage and time required to fully de-spin representative asteroids are also presented. Additionally, the time required for total de-spin is compared to the time required for partial arrest. Partial arrest of unstable spinners is possible under mission constraints for a range of asteroid sizes and densities. Total arrest can be achieved for less than 60 kg per spacecraft for a four-spacecraft NBAC system.