Redirecting an asteroid with introductory mechanics

In September, the Double Asteroid Redirection Test (DART) spacecraft will intercept the binary asteroid Didymos, colliding head on with Dimorphos, the smaller of the two asteroid bodies. The impact will reduce Dimorphos’ speed and shorten its period. By measuring the change in period, scientists hope to learn if collision redirection is viable for planetary defense.

In addition to testing protection methods for Earth, the mission presents an ideal opportunity for physics educators. Joseph Amato described the physics of the DART mission, including the spacecraft and asteroid’s heliocentric orbits, binary Didymos’ internal dynamics, the orbital effects of the collision, and the resultant impact crater.

“So many NASA missions are perfect illustrations of the laws of classical mechanics,” said Amato. “On Earth, nothing is ever ideal because there’s friction, or air resistance, or something else. But in space, there’s none of that. Things move just as you expect.”

Amato believes the mission is perfect for motivating and enriching a discussion on the conservation of momentum. The physics presented in his work is accessible to first year undergraduates, and he hopes his paper will encourage instructors to think more broadly and creatively about the way they present their lessons.

By incorporating further introductory mechanics topics, like energy conservation, forces, and collisions that are not head-on, DART could be an excellent way to collect and summarize important topics at the end of a course.

“I think the traditional curriculum, where one throws a ball in the air and calculates when and where it lands, or bounces billiard balls off each other, that kind of thing, is uninspiring,” Amato said. “We can do much better.”

Source: “DART: planetary defense in the introductory physics curriculum,” by Joseph C. Amato, The Physics Teacher (2022). The article can be accessed at https://doi.org/10.1119/5.0085522 .