The Double Asteroid Redirection Test (DART), one of NASA’s most thrilling and unique missions in years, is set to launch tonight on its journey to strike and deflect an oncoming space rock millions of kilometers from Earth. You can see it live here, though the major smash will not happen for a while. DART is our first effort as a spacefaring species to alter an incoming asteroid’s trajectory. Rest assured, this one poses no threat to our dear planet, but it does serve as an excellent test bed for the kind of interception that could be required if such a threat arises.
“Planetary Defense has been working on the problem for decades,” NASA’s Science Mission Directorate’s Thomas Zurbuchen noted, “It’s time to start putting this toolkit together; it’s becoming increasingly crucial for all of our stakeholders.” The program’s popularity has risen dramatically in the previous five years or so. People were talking about how this is truly excellent, we can see its effectiveness from the ground, there’s no need for a second inquiry.”
The asteroid in question is really the smaller of two in a binary system that is moving through the solar system as a married pair. Didymos, the bigger asteroid, is roughly half a mile broad – not quite a planet-killer, but close enough to cause havoc in your area. Our objective, Dimorphos, rotates around it, roughly 525 feet wide and peanut-shaped, about the size of the Statue of Liberty bouldering on.
DART fly out there and smash into Dimorphos as hard as possible just as it comes around the far side of Didymos — which will quite hard given that the spacecraft will weigh about 1,210 pounds and its new ion engine will have propelled it to a speed of 4.1 miles per second (if it had eyes and there was air). (For our metric friends, that is 550 kilos at 6.6 km/s; I will leave the impact force calculation to the experts.)
Dimorphos will not detonate and scatter bits all over the place. On the contrary, the effect will be scarcely discernible. However, the collision will have a little effect on the duration of its orbit around Didymos, slowing and enlarging it to the point where it may seen by a strong telescope. Scientists should able to determine the mass of the object and how efficient this refined approach of striking a heavy object with another thing was monitoring this change.
They may then make an educated choice about what could be required if, for example, an asteroid twice as huge were on a crash trajectory. We can redirect it just enough that it will not reach us by exerting this much force at this angle, at this moment, and at this distance (as far out as feasible, according to one team member).
This type of planetary defense activity will rely heavily on DART. We hope we will never need it, but we can all agree that it is better to be prepared than to have to assemble a motley gang of oilrig roughnecks at the last minute to bomb the Big One. Another “Armageddon” allusion to keep our adoring older readers interested.
“What we really want to accomplish with this is figure out how to size an impactor based on the amount of the danger that’s coming in.” “We want a really accurate impactor model,” Zurbuchen explained. Although there are no plans for another impact mission at this time, “I could easily see that a follow-up test with a different asteroid type might be on the books.”
Of course, even if the impact is minor, it will still be enjoyable. As a result, we are sending up a companion spacecraft, LICIACube, to keep an eye on things from afar, giving data as well as crowd-pleasing footage of our assault on Space Mountain. Most likely, it will appear to be nothing more than a cloud of dust, gravel, and solar panel components, but you never know.
It is possible that this is the asteroid with life on it. If that is the case, it will still be 6.8 million miles away, so we will not be in any danger right soon. In any case, it is difficult to envision a spacecraft colliding with an asteroid and not capturing the event on film.
“It’s a high-risk, high-impact experiment,” Zurbuchen said of the companion cubesat, which will need to correctly positioned and observe the impact constantly. “We’re confident it would have worked without it, but… gosh, I want to watch that movie.”
DART’s launch window begins tonight at around 10:20 p.m. Pacific, and the weather at Vandenberg Space Force Base is looking 90 percent good, according to the latest reports. Once it is out there, it will take about a year for the spacecraft to make its deadly collision with Dimorphos: the impact scheduled for the end of September 2022, but we will not know the precise date until all the variables locked down.
