Building The World’s First Asteroid Defense SystemSeptember 24, 2020
“Quite a few of your readers have probably seen the Armageddon movie with Bruce Willis,” said Heli Greus, product assurance and safety manager for the European Space Agency’s Hera project. “That [would] never work, but a realistic asteroid deflection technique is basically what we are trying to prove is possible. Hopefully, we will [soon] be able to say that, yes, it is possible to deflect an asteroid [on demand].”
For most of us, the idea of a planetary defense initiative remains the stuff of science fiction — or that more-than-slightly bonkers 1998 Michael Bay blockbuster. In 2020, there are plenty of more earthbound threats to worry about than the potential collision of giant rocks from outer space. But it does remain a risk. And it’s one that, thanks to the likes of Greus and her ESA colleagues, along with researchers from NASA and elsewhere, we shouldn’t have to worry about. Provided everything goes according to plan, that is.
Over the next several years, an international task force of scientists on the Asteroid Impact and Deflection Assessment (AIDA) team will be carrying out detailed research into this subject. Along the way, they will carry out a pair of pioneering space missions that will determine whether it is, indeed, possible to shift an asteroid as it hurtles through space at unimaginably high speed.
“Planetary defense is intrinsically a global issue, so it’s only natural that an asteroid deflection test be done in a context of international cooperation”
To start with, NASA will next year launch a mission called DART, or the Double Asteroid Redirection Test, in which the goal is to rocket an unmanned spacecraft directly into an asteroid at 13,320 miles per hour. Due to the distance the spacecraft has to travel, impact will only take place in 2022. Then, in 2024, the ESA will launch its follow-up Hera mission, which, by 2026, will reach the asteroid and carry out a variety of experiments to measure DART’s level of success. By the end of the decade, the world should have some idea of the degree to which this method could be used to alter the trajectory of a potential killer asteroid. At that point, work will start on a more permanent solution.
Teamwork makes the asteroid-killing dream work
At the end of Alan Moore’s magisterial comic series Watchmen (beware spoilers), the book’s ostensible villain makes it appear as though an alien has attacked Earth. His idea, it transpires, is that such an external attack will cause humanity to put aside its differences to work together to solve a bigger threat.
Space missions have, of course, changed an enormous amount since the days of the “Space Race” of the 1960s. But the idea of space as a haven for competition persists, with its most recent incarnation being the rise of rival space companies like SpaceX and Blue Origin, and the burgeoning rush for space resources. AIDA, for its part, is all about cooperation.
“Planetary defense is intrinsically a global issue, so it’s only natural that an asteroid deflection test be done in a context of international cooperation,” Tom Statler, program scientist for DART at NASA Headquarters, told Digital Trends.
Alongside the twin titan space agencies NASA and ESA, other players are involved. The DART mission includes the LICIACube cubesat, a contribution from the Italian Space Agency that will record the event by imaging the resulting ejecta plume. The Hera mission, meanwhile, will include a lidar instrument developed by a consortium from Portugal, Romania, and Latvia. The Milani CubeSat used in the project is the work of researchers from Italy, Finland, and the Czech Republic. And a thermal imager will be developed by the Japanese Space Agency and based on the one flown on the Hayabusa2 asteroid mission. Just to name a few.
“A binary asteroid is the perfect natural laboratory for a kinetic impact test”
Greus described the possibility of a deadly asteroid hitting Earth as “really, really minimal.” But “really, really minimal” is still a risk — and when it comes to potential existential threats, it’s not a risk worth taking. Over the years, scientists have gotten better at tracing asteroids. The problem is that, right now, planetary defense is a bit like having a smart security camera on in your home if you’re on vacation and have no way of calling 911. Sure, you can watch what’s happening, but you can’t do much about it. This is what the Asteroid Impact and Deflection Assessment team hopes to change.
‘Nobody has to panic’
The asteroid that will be used as a proof of concept in the upcoming decade-long mission is not a threat to Earth. “Nobody has to panic,” said Greus reassuringly. It is a small asteroid called Dimorphos that is, itself, a tiny moon orbiting a much larger asteroid called Didymos in what is referred to as a binary asteroid system. (Small is, of course, relative. Dimorphos is approximately the size of the Great Pyramid of Giza, and could obliterate a city if it ever collided with Earth.)
“A binary asteroid is the perfect natural laboratory for a kinetic impact test, because it lets us gauge the effect of the impact from the change in the binary orbit, which we can observe using telescopes on Earth,” Statler said.
Currently Dimorphos orbits Didymos once every 11 hours, 55 minutes, and 18 seconds. Statler said that he expects the DART impact to change that period “by several minutes.” In other words, it will simply be a nudge that could, in a more life-and-death context, give a would-be killer asteroid a slight push to send it whizzing past the Earth, rather than into it. (Or, if that is not possible, conceivably destroy them on site.)
“This is definitely an issue that would affect the whole world, so working all together, we maximize the chance to create a solution.”
The DART spacecraft, he explained, is a whole lot like a regular spacecraft. “DART is conventional in many ways, and that’s deliberate,” Statler said. “If we ever need to launch a kinetic impactor to prevent a real asteroid impact, we’ll want to use tried-and-true designs for quick development and low risk. So DART has the same basic components, doing the same basic tasks, as most other spacecraft. It’s even simpler than most of our planetary spacecraft because it has only one instrument: The Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO).”
The three aspects that are new are a SmartNav system that will enable the craft to steer autonomously in its final few hours, a Roll-Out Solar Arrays (ROSA) configuration that will be flown for the first time on a planetary mission, and NASA’s Evolutionary Xenon Thruster — Commercial (NEXT–C), a solar-electric ion propulsion system. Other than that, it’s a regular spacecraft. Albeit a kamikaze one.
Building the anti-asteroid weapons that will keep us safe
Whatever findings are gathered from this project will ultimately form the basis of some kind of planetary defense system in the years to come. “Everything that we will find will be new information,” Greus said. “Based on the new information, then we can develop new technologies.”
Like the combined DART and Hera project, hopefully this too will become a global collaboration. After all, wherever petty differences we might have on Earth hopefully pale into insignificance in the face of a potential threat against humanity as a whole.
Projects like the International Space Station show what can be achieved when space agencies from around the globe unite in the name of space science. Now, asteroid defense could be at the forefront of the next phase in cooperation.
“This is definitely an issue that would affect the whole world, so working all together, we maximize the chance to [create a solution],” Greus said.