Design of low-thrust missions to asteroids with analysis of the missed-thrust problem

Small bodies in the Solar System, such as asteroids and dwarf planets, are ideal targets for electric propulsion missions because of the high delta-V required to rendezvous with these targets. We study trajectories to the asteroid belt, including a human mission to Ceres and a sample return mission to (216) Kleopatra, along with trajectories to the Jupiter Trojan asteroids. For the human mission to Ceres, payload masses of 75 Mg are achievable with a 11.7 MW nuclear electric propulsion system and an initial mass in LEO of 289 Mg. For low-thrust sample return missions to the main belt asteroid Kleopatra, Mars and Earth are useful gravity assist bodies, with payload masses of 950-1150 kg possible using a 20 kW solar electric propulsion system. A mission to the Jupiter Trojan asteroids would be well-served by visiting two objects. The pair 1986 TS6 and Hektor stand out as ideal targets to visit for launch dates between 2020 and 2040, with missions possible using the off-the-shelf BPT-4000 Hall thruster and power levels in the 30-40 kW range. During a low-thrust mission, there is a significant possibility of an event which causes the spacecraft to miss some portion of a thrust arc. These missed thrust events can be overcome for reasonable propellant margins of 5--15\%, with higher margins required for higher power levels. Gravity-assist trajectories should feature a coast arc leading up to the flyby. If not, the mission may be lost if a missed-thrust event occurs during a thrust arc prior to the gravity assist

Successful Kinetic Impact into an Asteroid for Planetary Defense.

While no known asteroid poses a threat to Earth for at least the next century, the catalog of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation1,2. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid1-3. A test of kinetic impact technology was identified as the highest priority space mission related to asteroid mitigation1. NASA's Double Asteroid Redirection Test (DART) mission is the first full-scale test of kinetic impact technology. The mission's target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by DART's impact4. While past missions have utilized impactors to investigate the properties of small bodies5,6, those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft's autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in Dimorphos's orbit7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary