Uncrewed Systems Technology 046

56 W hile many of the world’s newsrooms and social media platforms discuss plans for human colonies on the Moon and Mars, it must be remembered that an immense amount of groundwork must first be laid by uncrewed missions before they can be established. That does not simply mean laying the literal foundations for habitable environments and the energy and resource inputs needed for human survival. Space and alien worlds are still hugely unknown environments, even before we consider astronaut safety. Fortunately though, the spacecraft industry continues to pursue a wide range of uncrewed missions and systems, to uncover more of the mysteries of our Solar System, and in turn reveal ways that we might mitigate against or defend space crews and uncrewed assets from the most dangerous threats. Asteroids In a major leap forward in humanity’s ability to ensure its survival against existential threats, NASA’s Planetary Defense Coordination Office has successfully crashed an uncrewed spacecraft into an asteroid with the intention of deflecting it from its original path. The spacecraft in question was the DART (Double Asteroid Redirection Test, a name it shared with the mission programme around it), a vehicle equipped with numerous new subsystems NASA aimed to mature as part of the mission. It measured about 2.6 x 1.9 x 1.8 m and weighed 610 kg at launch. Of those subsystems, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) was key to its terminal approach, with SMART Nav (Small-body Manoeuvring Autonomous Real Time Navigation) algorithms powering the autonomy key to DRACO’s intelligent path-planning towards the asteroid. The algorithms ran on a Coresat (Core Small Avionics suiTe) computer built by John Hopkins Applied Physics Laboratory (APL), and streamed photographs back to Earth at 1 Hz via a radial line slot array high-gain antenna. The target asteroid in question was Dimorphos, one of two bodies in the Didymos binary asteroid system. It is 160 m in diameter and orbits the larger, 780 m Didymos. Part of SMART Nav’s functions included distinguishing between the two objects using DRACO’s imagery, to ensure that the correct asteroid was being approached. Dimorphous and its sibling are not threats to Earth, but researchers anticipate that the impact will shorten Dimorphos’ orbit by about 1%, or roughly 10 minutes. Precise measurements of the degree of deflection achieved was one of the primary purposes of the full-scale test, with closer understanding of how to redirect the trajectories of asteroids through kinetic uncrewed spacecraft impacts, planetary defence being the end goal. To reach Dimorphous, the DART also integrated the NEXT–C (NASA’s Evolutionary Xenon Thruster – Commercial) ion engine, an electric propulsion solution developed by the Glenn Research Center in Ohio, in collaboration with California-based Aerojet Rocketdyne. The electric demonstrator engine ran using xenon (with 50 kg of hydrazine propellant for manoeuvring and attitude October/November 2022 | Uncrewed Systems Technology Critical missions Uncrewed systems are playing a vital role in understanding offworld environments and keeping space crews safe in them, as Rory Jackson explains