San Antonio’s Southwest Research Institute played role in successful mission to strike asteroid with craft

The thought of an asteroid striking the earth and wreaking havoc might keep people awake at night. But scientists worked on a way to prevent this from happening by playing a sort of interplanetary game of pool. The idea was to use the kinetic energy of a spacecraft to deflect these potential earthbound asteroids.

On Monday evening, that idea was successfully realized. The Double Asteroid Redirection Test (DART) spacecraft, traveling about 14,000 mph, slammed into an asteroid named Dimorphos, right on target. Read NPR’s latest story on the $300 million project here.

In mid September, about two weeks before the mission, TPR’s Jerry Clayton spoke with James Walker, director of the Engineering Dynamics Department at Southwest Research Institute, and one of the scientists on the DART team.

This conversation has been condensed and edited for clarity.

Clayton: For those who aren’t familiar, can you give us a brief overview of the DART mission?

Walker: The DART spacecraft was launched last November. It’s on a trajectory which will intersect with an asteroid with the intent to impact the asteroid, small moon or moonlet. The asteroid is Didymos, the moonlet is named Dimorphos, and the intent of this mission is to get information on how much momentum is transferred from the spacecraft to the asteroid.

There’s more momentum than just that of the spacecraft because of the debris that comes out from the crater that’s formed from the impact. This information is of interest to us, because someday we may need to or want to deflect an asteroid or a comet nucleus.

Clayton: I looked at some of the work that you do and some pictures from your lab, and it looks like a fun place! What’s it like?

Walker: Here in the Engineering Dynamics Department, we do quite a bit of impact related work. In particular, we have what’s known as a two stage light gas gun which can shoot projectiles up to six, seven kilometers per second, so on the order of 15,000 miles per hour.

We use this launcher for a variety of studies, including studies related to asteroids and impact on the asteroids and other celestial objects.

Clayton: So at this point, what is your expectation as to what will happen when the DART spacecraft hits its target?

Walker: So when the DART spacecraft strikes the moonlet of the asteroid, we’ll expect a relatively large crater to be formed, throwing a lot of ejecta back in the direction the spacecraft was traveling.

The spacecraft is moving at about 6.1 kilometers per second relative to the asteroid, around 13,000 miles an hour. And because of that, we will get more momentum than the spacecraft had originally. And we are expecting at least three times as much momentum will be transferred.

Clayton: Are there still questions about the density and composition of the asteroid and its moon?

Walker: There is. In particular, it’s a question of density and composition of the moon. The density of the asteroid is known, but the moon we don’t actually know. So it’s conjectured — it will be similar to the asteroid. But the way we’re going to infer the density will be based on photographs as the spacecraft approaches that it sends back for our analysis.

Clayton: Looking forward, how confident are you that this idea would work when it comes to a real near-Earth asteroid?

Walker: We’re quite confident that we know how to hit objects in space, not only from work with spacecraft before — and there’s been a previous impact. Intentional. The comet Tempel 1 was struck by the Deep Impact spacecraft. The question really is how efficient is it at deflecting an asteroid or a comet nucleus?

That’s why we’re doing the test to better understand how much momentum is transferred, since if the multiplier is quite large, that would imply this is actually a very efficient and effective approach to deflecting an asteroid. And by this method, I mean hitting it with a hyper-velocity impactor.