Learning from DART to protect the world from future near-Earth object impacts
For as long as he can remember, Rahil Makadia says he has wanted to make a positive contribution to spaceflight and help humanity make great technological advances. Because of his undergraduate and graduate work in the Department of Aerospace Engineering at the University of Illinois Urbana-Champaign with NASAs Double Asteroid Redirection Test mission, he has already begun living that dream.
Now, as a doctoral student, working with Professor Siegfried Eggl, Makadia's goal has sharpened to something more specific. "I would like to conduct work that enhances the state-of-the-art capabilities for protecting the world from near-Earth object impacts," Makadia said.
NASA agrees. Recently, Makadia received a NASA Space Technology Graduate Research Opportunities award. The NASA fellowship includes funding for four years of his graduate studies. It also supports visiting technologist experiences at NASA, an invaluable opportunity for students to get exposure to the agency.
His project title is "Keyhole-Based Impact Site Selection and Post-Deflection Impact Risk Assessment for Near-Earth Objects." With the impact of the Double Asteroid Redirection Test scheduled for September 26, Makadia believes research on this solution and efforts to develop other options is imperative.
"We need to develop efficient and effective strategies to change the orbit of incoming asteroids," Makadia said. "The DART mission is a test that aims to demonstrate the deflection of an asteroid via kinetic impact. However, if they are not deflected in a controlled manner, potential impactors can return and collide with the Earth. The research I’m working on with Professor Eggl will combine aspects of celestial mechanics and planetary science to ensure the success of future asteroid deflection efforts through a novel method for steering impacting near-Earth objects clear of the Earth – permanently."
Makadia described more about his research and its relationship to DART.
"DART is, in essence, a spacecraft sent on a high-speed collision course with the asteroid. The resulting kinetic impact transfers the spacecraft momentum onto the asteroid and changes its orbit. Unfortunately, this process comes with uncertainties, and the asteroid’s physical characteristics are the reason for that. The rocks, pebbles, and sand-like fine particles around the impact site contribute to the change in the momentum of the asteroid. When these ejecta particles fly off the asteroid’s surface during a hypervelocity impact, they act as an additional ‘kick’ that can impart more momentum than the impactor itself. Therefore, the direction and magnitude of this ejecta momentum can drive the change in an asteroid’s orbit."
Makadia said this cumulative momentum exchange is quantified by the momentum enhancement parameter.
"Uncertainties in this escaping ejecta momentum translate into uncertainty in the final, deflected position of the asteroid. This can allow it to pass through a gravitational keyhole – a region near the Earth that would guarantee an impact by the asteroid in the future, and render the initial deflection moot," he said.
He added, "Fortunately for us, our work has shown that the target of the DART mission, the Didymos binary asteroid system, does not have keyholes with the Earth. Therefore, it does not pose an impact risk to the Earth," referring to his recent study, Heliocentric Effects of the DART Mission on the (65803) Didymos Binary Asteroid System, which was published in the Planetary Science Journal.
Makadia’s work will build and improve on previous studies and use data from DART to better understand relationships between impact momentum exchange and asteroid physical parameters.
"I will also leverage my membership in the DART Science Investigation Team to build and update numerical tools that model the momentum exchange from deflecting an asteroid in a more realistic fashion. Combining these updated models with the physical characteristics of other potentially hazardous asteroids will allow me to develop strategies that can locate the optimal impact sites on an asteroid’s surface to steer it clear of keyholes," he said.
His project aims to modernize the capabilities of future DART-like asteroid deflection campaigns by using all available information on a potentially hazardous asteroid, in particular information on its shape and surface composition, to avoid pushing a deflected asteroid into a gravitational keyhole.
"The outcome of the project will be an end-to-end pipeline that can be used alongside existing trajectory optimization tools to design future deflection missions for hazardous asteroids," Makadia said. “Having such a framework available could save precious time when an asteroid is discovered to be on a collision course with the Earth."